open solar magnetic: Topics by Science.gov

Solar Open Flux Migration from Pole to Pole: Magnetic Field Reversal.

PubMed

Huang, G-H; Lin, C-H; Lee, L C

2017-08-25

Coronal holes are solar regions with low soft X-ray or low extreme ultraviolet intensities. The magnetic fields from coronal holes extend far away from the Sun, and thus they are identified as regions with open magnetic field lines. Coronal holes are concentrated in the polar regions during the sunspot minimum phase, and spread to lower latitude during the rising phase of solar activity. In this work, we identify coronal holes with outward and inward open magnetic fluxes being in the opposite poles during solar quiet period. We find that during the sunspot rising phase, the outward and inward open fluxes perform pole-to-pole trans-equatorial migrations in opposite directions. The migration of the open fluxes consists of three parts: open flux areas migrating across the equator, new open flux areas generated in the low latitude and migrating poleward, and new open flux areas locally generated in the polar region. All three components contribute to the reversal of magnetic polarity. The percentage of contribution from each component is different for different solar cycle. Our results also show that the sunspot number is positively correlated with the lower-latitude open magnetic flux area, but negatively correlated with the total open flux area.
Signature of open magnetic field lines in the extended solar corona and of solar wind acceleration

NASA Technical Reports Server (NTRS)

Antonucci, E.; Giordano, S.; Benna, C.; Kohl, J. L.; Noci, G.; Michels, J.; Fineschi, S.

1997-01-01

The observations carried out with the ultraviolet coronagraph spectrometer onboard the Solar and Heliospheric Observatory (SOHO) are discussed. The purpose of the observations was to determine the line of sight and radial velocity fields in coronal regions with different magnetic topology. The results showed that the regions where the high speed solar wind flows along open field lines are characterized by O VI 1032 and HI Lyman alpha 1216 lines. The global coronal maps of the line of sight velocity were reconstructed. The corona height, where the solar wind reaches 100 km/s, was determined.
Variations of solar, interplanetary, and geomagnetic parameters with solar magnetic multipole fields during Solar Cycles 21-24

NASA Astrophysics Data System (ADS)

Kim, Bogyeong; Lee, Jeongwoo; Yi, Yu; Oh, Suyeon

2015-01-01

In this study we compare the temporal variations of the solar, interplanetary, and geomagnetic (SIG) parameters with that of open solar magnetic flux from 1976 to 2012 (from Solar Cycle 21 to the early phase of Cycle 24) for a purpose of identifying their possible relationships. By the open flux, we mean the average magnetic field over the source surface (2.5 solar radii) times the source area as defined by the potential field source surface (PFSS) model of the Wilcox Solar Observatory (WSO). In our result, most SIG parameters except the solar wind dynamic pressure show rather poor correlations with the open solar magnetic field. Good correlations are recovered when the contributions from individual multipole components are counted separately. As expected, solar activity indices such as sunspot number, total solar irradiance, 10.7 cm radio flux, and solar flare occurrence are highly correlated with the flux of magnetic quadrupole component. The dynamic pressure of solar wind is strongly correlated with the dipole flux, which is in anti-phase with Solar Cycle (SC). The geomagnetic activity represented by the Ap index is correlated with higher order multipole components, which show relatively a slow time variation with SC. We also found that the unusually low geomagnetic activity during SC 23 is accompanied by the weak open solar fields compared with those in other SCs. It is argued that such dependences of the SIG parameters on the individual multipole components of the open solar magnetic flux may clarify why some SIG parameters vary in phase with SC and others show seemingly delayed responses to SC variation.
An Alternative Interpretation of the Relationship between the Inferred Open Solar Flux and the Interplanetary Magnetic Field

NASA Technical Reports Server (NTRS)

Riley, Pete

2007-01-01

Photospheric observations at the Wilcox Solar Observatory (WSO) represent an uninterrupted data set of 32 years and are therefore unique for modeling variations in the magnetic structure of the corona and inner heliosphere over three solar cycles. For many years, modelers have applied a latitudinal correction factor to these data, believing that it provided a better estimate of the line-of-sight magnetic field. Its application was defended by arguing that the computed open flux matched observations of the interplanetary magnetic field (IMF) significantly better than the original WSO correction factor. However, no physically based argument could be made for its use. In this Letter we explore the implications of using the constant correction factor on the value and variation of the computed open solar flux and its relationship to the measured IMF. We find that it does not match the measured IMF at 1 AU except at and surrounding solar minimum. However, we argue that interplanetary coronal mass ejections (ICMEs) may provide sufficient additional magnetic flux to the extent that a remarkably good match is found between the sum of the computed open flux and inferred ICME flux and the measured flux at 1 AU. If further substantiated, the implications of this interpretation may be significant, including a better understanding of the structure and strength of the coronal field and I N providing constraints for theories of field line transport in the corona, the modulation of galactic cosmic rays, and even possibly terrestrial climate effects.
Magnetic Fields and Flows in Open Magnetic Structures

NASA Technical Reports Server (NTRS)

Jones, Harrlson P.

2004-01-01

Open magnetic structures connect the solar surface to the heliosphere and are thus of great interest in solar-terrestrial physics. This talk is primarily an observational review of what is known about magnetic fields and particularly flows in such regions with special focus on coronal holes and origins of the fast solar wind. First evidence of the connection between these two features was seen in correlations of Skylab data with in situ measurements of the solar wind soon after the discovery of coronal holes, which are now known to emanate from unipolar magnetic regions at the photosphere. Subsequently many observations of have been made, ranging from oscillations in the underlying photosphere and chromosphere, to possible beginnings of the solar wind as observed by Doppler shifts in high chromospheric and transition-region lines, to coronagraphic time-lapse studies of outward-moving blobs of material which perhaps trace elements of solar-wind plasma. Some of the many unresolved and controversial issues regarding details of these observations and their association with the solar wind will be discussed.
Coronal Holes and Magnetic Flux Ropes Interweaving Solar Cycles

NASA Astrophysics Data System (ADS)

Lowder, Chris; Yeates, Anthony; Leamon, Robert; Qiu, Jiong

2016-10-01

Coronal holes, dark patches observed in solar observations in extreme ultraviolet and x-ray wavelengths, provide an excellent proxy for regions of open magnetic field rooted near the photosphere. Through a multi-instrument approach, including SDO data, we are able to stitch together high resolution maps of coronal hole boundaries spanning the past two solar activity cycles. These observational results are used in conjunction with models of open magnetic field to probe physical solar parameters. Magnetic flux ropes are commonly defined as bundles of solar magnetic field lines, twisting around a common axis. Photospheric surface flows and magnetic reconnection work in conjunction to form these ropes, storing magnetic stresses until eruption. With an automated methodology to identify flux ropes within observationally driven magnetofrictional simulations, we can study their properties in detail. Of particular interest is a solar-cycle length statistical description of eruption rates, spatial distribution, magnetic orientation, flux, and helicity. Coronal hole observations can provide useful data about the distribution of the fast solar wind, with magnetic flux ropes yielding clues as to ejected magnetic field and the resulting space weather geo-effectiveness. With both of these cycle-spanning datasets, we can begin to form a more detailed picture of the evolution and consequences of both sets of solar magnetic features.
Magnetic Helicity and the Solar Dynamo

NASA Technical Reports Server (NTRS)

Canfield, Richard C.

1997-01-01

The objective of this investigation is to open a new window into the solar dynamo, convection, and magnetic reconnection through measurement of the helicity density of magnetic fields in the photosphere and tracing of large-scale patterns of magnetic helicity in the corona.
The Evolution of Open Magnetic Flux Driven by Photospheric Dynamics

NASA Technical Reports Server (NTRS)

Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav S.; Antiochos, Spiro K.

2010-01-01

The coronal magnetic field is of paramount importance in solar and heliospheric physics. Two profoundly different views of the coronal magnetic field have emerged. In quasi-steady models, the predominant source of open magnetic field is in coronal holes. In contrast, in the interchange model, the open magnetic flux is conserved, and the coronal magnetic field can only respond to the photospheric evolution via interchange reconnection. In this view the open magnetic flux diffuses through the closed, streamer belt fields, and substantial open flux is present in the streamer belt during solar minimum. However, Antiochos and co-workers, in the form of a conjecture, argued that truly isolated open flux cannot exist in a configuration with one heliospheric current sheet (HCS) - it will connect via narrow corridors to the polar coronal hole of the same polarity. This contradicts the requirements of the interchange model. We have performed an MHD simulation of the solar corona up to 20R solar to test both the interchange model and the Antiochos conjecture. We use a synoptic map for Carrington Rotation 1913 as the boundary condition for the model, with two small bipoles introduced into the region where a positive polarity extended coronal hole forms. We introduce flows at the photospheric boundary surface to see if open flux associated with the bipoles can be moved into the closed-field region. Interchange reconnection does occur in response to these motions. However, we find that the open magnetic flux cannot be simply injected into closed-field regions - the flux eventually closes down and disconnected flux is created. Flux either opens or closes, as required, to maintain topologically distinct open and closed field regions, with no indiscriminate mixing of the two. The early evolution conforms to the Antiochos conjecture in that a narrow corridor of open flux connects the portion of the coronal hole that is nearly detached by one of the bipoles. In the later evolution, a
Is magnetic topology important for heating the solar atmosphere?

PubMed

Parnell, Clare E; Stevenson, Julie E H; Threlfall, James; Edwards, Sarah J

2015-05-28

Magnetic fields permeate the entire solar atmosphere weaving an extremely complex pattern on both local and global scales. In order to understand the nature of this tangled web of magnetic fields, its magnetic skeleton, which forms the boundaries between topologically distinct flux domains, may be determined. The magnetic skeleton consists of null points, separatrix surfaces, spines and separators. The skeleton is often used to clearly visualize key elements of the magnetic configuration, but parts of the skeleton are also locations where currents and waves may collect and dissipate. In this review, the nature of the magnetic skeleton on both global and local scales, over solar cycle time scales, is explained. The behaviour of wave pulses in the vicinity of both nulls and separators is discussed and so too is the formation of current layers and reconnection at the same features. Each of these processes leads to heating of the solar atmosphere, but collectively do they provide enough heat, spread over a wide enough area, to explain the energy losses throughout the solar atmosphere? Here, we consider this question for the three different solar regions: active regions, open-field regions and the quiet Sun. We find that the heating of active regions and open-field regions is highly unlikely to be due to reconnection or wave dissipation at topological features, but it is possible that these may play a role in the heating of the quiet Sun. In active regions, the absence of a complex topology may play an important role in allowing large energies to build up and then, subsequently, be explosively released in the form of a solar flare. Additionally, knowledge of the intricate boundaries of open-field regions (which the magnetic skeleton provides) could be very important in determining the main acceleration mechanism(s) of the solar wind. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Observations of disconnection of open coronal magnetic structures

NASA Technical Reports Server (NTRS)

Mccomas, D. J.; Phillips, J. L.; Hundhausen, A. J.; Burkepile, J. T.

1991-01-01

The solar maximum mission coronagraph/polarimeter observations are surveyed for evidence of magnetic disconnection of previously open magnetic structures and several sequences of images consistent with this interpretation are identified. Such disconnection occurs when open field lines above helmet streamers reconnect, in contrast to previously suggested disconnections of CMEs into closed plasmoids. In this paper a clear example of open field disconnection is shown in detail. The event, on June 27, 1988, is preceded by compression of a preexisting helmet streamer and the open coronal field around it. The compressed helmet streamer and surrounding open field region detach in a large U-shaped structure which subsequently accelerates outward from the sun. The observed sequence of events is consistent with reconnection across the heliospheric current sheet and the creation of a detached U-shaped magnetic structure. Unlike CMEs, which may open new magnetic flux into interplanetary space, this process could serve to close off previously open flux, perhaps helping to maintain the roughly constant amount of open magnetic flux observed in interplanetary space.
The Evolution of Open Magnetic Flux Driven by Photospheric Dynamics

NASA Astrophysics Data System (ADS)

Linker, Jon A.; Lionello, Roberto; Mikić, Zoran; Titov, Viacheslav S.; Antiochos, Spiro K.

2011-04-01

The coronal magnetic field is of paramount importance in solar and heliospheric physics. Two profoundly different views of the coronal magnetic field have emerged. In quasi-steady models, the predominant source of open magnetic field is in coronal holes. In contrast, in the interchange model, the open magnetic flux is conserved, and the coronal magnetic field can only respond to the photospheric evolution via interchange reconnection. In this view, the open magnetic flux diffuses through the closed, streamer belt fields, and substantial open flux is present in the streamer belt during solar minimum. However, Antiochos and coworkers, in the form of a conjecture, argued that truly isolated open flux cannot exist in a configuration with one heliospheric current sheet—it will connect via narrow corridors to the polar coronal hole of the same polarity. This contradicts the requirements of the interchange model. We have performed an MHD simulation of the solar corona up to 20 R sun to test both the interchange model and the Antiochos conjecture. We use a synoptic map for Carrington rotation 1913 as the boundary condition for the model, with two small bipoles introduced into the region where a positive polarity extended coronal hole forms. We introduce flows at the photospheric boundary surface to see if open flux associated with the bipoles can be moved into the closed-field region. Interchange reconnection does occur in response to these motions. However, we find that the open magnetic flux cannot be simply injected into closed-field regions—the flux eventually closes down and disconnected flux is created. Flux either opens or closes, as required, to maintain topologically distinct open- and closed-field regions, with no indiscriminate mixing of the two. The early evolution conforms to the Antiochos conjecture in that a narrow corridor of open flux connects the portion of the coronal hole that is nearly detached by one of the bipoles. In the later evolution, a
Identifying open magnetic field regions of the Sun and their heliospheric counterparts

NASA Astrophysics Data System (ADS)

Krista, L. D.; Reinard, A.

2017-12-01

Open magnetic regions on the Sun are either long-lived (coronal holes) or transient (dimmings) in nature. Both phenomena are fundamental to our understanding of the solar behavior as a whole. Coronal holes are the sources of high-speed solar wind streams that cause recurrent geomagnetic storms. Furthermore, the variation of coronal hole properties (area, location, magnetic field strength) over the solar activity cycle is an important marker of the global evolution of the solar magnetic field. Dimming regions, on the other hand, are short-lived coronal holes that often emerge in the wake of solar eruptions. By analyzing their physical properties and their temporal evolution, we aim to understand their connection with their eruptive counterparts (flares and coronal mass ejections) and predict the possibility of a geomagnetic storm. The author developed the Coronal Hole Automated Recognition and Monitoring (CHARM) and the Coronal Dimming Tracker (CoDiT) algorithms. These tools not only identify but track the evolution of open magnetic field regions. CHARM also provides daily coronal hole maps, that are used for forecasts at the NOAA Space Weather Prediction Center. Our goal is to better understand the processes that give rise to eruptive and non-eruptive open field regions and investigate how these regions evolve over time and influence space weather.
Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution

NASA Astrophysics Data System (ADS)

Lockwood, Mike; Owens, Mathew J.; Imber, Suzanne M.; James, Matthew K.; Bunce, Emma J.; Yeoman, Timothy K.

2017-06-01

Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25.Plain Language SummaryThere is growing interest in being able to predict the evolution in solar conditions on a better basis than past experience, which is necessarily limited. Two of the key features of the solar magnetic cycle are that the polar fields reverse just after the peak of each sunspot cycle and that the polar field that has accumulated by the time of each sunspot </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.1944N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.1944N">Magnetic Reconnection and Particle Acceleration in the Solar Corona</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Neukirch, Thomas Reconnection plays a major role for the magnetic activity of the solar atmosphere, for example solar flares. An interesting open problem is how magnetic reconnection acts to redistribute the stored magnetic energy released during an eruption into other energy forms, e.g. gener-ating bulk flows, plasma heating and non-thermal energetic particles. In particular, finding a theoretical explanation for the observed acceleration of a large number of charged particles to high energies during solar flares is presently one of the most challenging problems in solar physics. One difficulty is the vast difference between the microscopic (kinetic) and the macro-scopic (MHD) scales involved. Whereas the phenomena observed to occur on large scales are reasonably well explained by the so-called standard model, this does not seem to be the case for the small-scale (kinetic) aspects of flares. Over the past years, observations, in particular by RHESSI, have provided evidence that a naive interpretation of the data in terms of the standard solar flare/thick target model is problematic. As a consequence, the role played by magnetic reconnection in the particle acceleration process during solar flares may have to be reconsidered. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030106064','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030106064">The Magnetic Structure of H-Alpha Macrospicules in Solar Coronal Holes</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Yamauchi, Y.; Moore, R. L.; Suess, S. T.; Wang, H.; Sakuri, T. 2003-01-01 Measurements by Ulysses in the high-speed polar solar wind have shown the wind to carry some fine-scale structures in which the magnetic field reverses direction by having a switchback fold in it. The lateral span of these magnetic switchbacks, translated to the Sun, is of the scale of the lanes and cells of the magnetic network in which the open magnetic flux of the polar coronal hole and polar solar wind are rooted. This suggests that the magnetic switchbacks might be formed from network-scale magnetic loops that erupt into the corona and then undergo reconnection with the open field. This possibility motivated us to undertake the study reported here of the structure of H-alpha macrospicules observed at the limb in polar coronal holes, to determine whether a significant fraction of these eruptions appear to be erupting loops. From a search of the polar-coronal holes in 6 days of image-processed full-disk H-alpha movies from Big Bear Solar Observatory, we found a total of 35 macrospicules. Nearly all of these (32) were of one or the other of two different forms: 15 were in the form of an erupting loop, and 17 were in the form of a single-column spiked jet. The erupting-loop macrospicules are appropriate for producing the magnetic switchbacks in the polar wind. The spiked-jet macrospicules show the appropriate structure and evolution to be driven by reconnection between network-scale closed field (a network bipole) and the open field rooted against the closed field. This evidence for reconnection in a large fraction of our macrospicules (1) suggests that many spicules may be generated by similar but smaller reconnection events, and (2) supports the view that coronal heating and solar wind acceleration in coronal holes and in quiet regions and corona are driven by explosive reconnection events in the magnetic network. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040071072&hterms=polar+bear&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dpolar%2Bbear','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040071072&hterms=polar+bear&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dpolar%2Bbear">The Magnetic Structure of H-alpha Macrospicules in Solar Coronal Holes</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Yamauchi, Y.; Moore, R. L.; Suess, S. T.; Wang, H.; Sakurai, T. 2004-01-01 Measurements by Ulysses in the high-speed polar solar wind have shown the wind to carry some fine-scale structures in which the magnetic field reverses direction by having a switchback fold in it. The lateral span of these magnetic switchbacks, translated back to the Sun, is of the scale of the lanes and cells of the magnetic network in which the open magnetic field of the polar coronal hole and polar solar wind are rooted. This suggests that the magnetic switchbacks might be formed from network-scale magnetic loops that erupt into the corona and then undergo reconnection with the open field. This possibility motivated us to undertake the study reported here of the structure of Ha macrospicules observed at the limb in polar coronal holes, to determine whether a significant fraction of these eruptions appear to be erupting loops. From a search of the polar coronal holes in 6 days of image- processed full-disk Ha movies from Big Bear Solar Observatory, we found a total of 35 macrospicules. Nearly all of these (32) were of one or the other of two different forms: 15 were in the form of an erupting loop, and 17 were in the form of a single column spiked jet. The erupting-loop macrospicules are appropriate for producing the magnetic switchbacks in the polar wind. The spiked-jet macrospicules show the appropriate structure and evolution to be driven by reconnection between network-scale closed field (a network bipole) and the open field rooted against the closed field. This evidence for reconnection in a large fraction of our macrospicules (1) suggests that many spicules may be generated by similar but smaller reconnection events and (2) supports the view that coronal heating and solar wind acceleration in coronal holes and in quiet regions are driven by explosive reconnection events in the magnetic network. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040191354','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040191354">The Effects of Differential Rotation on the Magnetic Structure of the Solar Corona: MHD Simulations</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Lionello, Roberto; Riley, Pete; Linker, Jon A.; Mikic, Zoran 2004-01-01 Coronal holes are magnetically open regions from which the solar wind streams. Magnetic reconnection has been invoked to reconcile the apparently rigid rotation of coronal holes with the differential rotation of magnetic flux in the photosphere. This mechanism might also be relevant to the formation of the slow solar wind, the properties of which seem to indicate an origin from the opening of closed magnetic field lines. We have developed a global MHD model to study the effect of differential rotation on the coronal magnetic field. Starting from a magnetic flux distribution similar to that of Wang et al., which consists of a bipolar magnetic region added to a background dipole field, we applied differential rotation over a period of 5 solar rotations. The evolution of the magnetic field and of the boundaries of coronal holes are in substantial agreement with the findings of Wang et al.. We identified examples of interchange reconnection and other changes of topology of the magnetic field. Possible consequences for the origin of the slow solar wind are also discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...594A..98Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...594A..98Y">The global distribution of magnetic helicity in the solar corona</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yeates, A. R.; Hornig, G. 2016-10-01 By defining an appropriate field line helicity, we apply the powerful concept of magnetic helicity to the problem of global magnetic field evolution in the Sun's corona. As an ideal-magnetohydrodynamic invariant, the field line helicity is a meaningful measure of how magnetic helicity is distributed within the coronal volume. It may be interpreted, for each magnetic field line, as a magnetic flux linking with that field line. Using magneto-frictional simulations, we investigate how field line helicity evolves in the non-potential corona as a result of shearing by large-scale motions on the solar surface. On open magnetic field lines, the helicity injected by the Sun is largely output to the solar wind, provided that the coronal relaxation is sufficiently fast. But on closed magnetic field lines, helicity is able to build up. We find that the field line helicity is non-uniformly distributed, and is highly concentrated in twisted magnetic flux ropes. Eruption of these flux ropes is shown to lead to sudden bursts of helicity output, in contrast to the steady flux along the open magnetic field lines. Movies are available at http://www.aanda.org </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRA..118.6889H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRA..118.6889H">An MHD simulation model of time-dependent global solar corona with temporally varying solar-surface magnetic field maps</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hayashi, K. 2013-11-01 We present a model of a time-dependent three-dimensional magnetohydrodynamics simulation of the sub-Alfvenic solar corona and super-Alfvenic solar wind with temporally varying solar-surface boundary magnetic field data. To (i) accommodate observational data with a somewhat arbitrarily evolving solar photospheric magnetic field as the boundary value and (ii) keep the divergence-free condition, we developed a boundary model, here named Confined Differential Potential Field model, that calculates the horizontal components of the magnetic field, from changes in the vertical component, as a potential field confined in a thin shell. The projected normal characteristic method robustly simulates the solar corona and solar wind, in response to the temporal variation of the boundary Br. We conduct test MHD simulations for two periods, from Carrington Rotation number 2009 to 2010 and from Carrington Rotation 2074 to 2075 at solar maximum and minimum of Cycle 23, respectively. We obtained several coronal features that a fixed boundary condition cannot yield, such as twisted magnetic field lines at the lower corona and the transition from an open-field coronal hole to a closed-field streamer. We also obtained slight improvements of the interplanetary magnetic field, including the latitudinal component, at Earth. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930049682&hterms=Open+Field&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DOpen%2BField','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930049682&hterms=Open+Field&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DOpen%2BField">Counterstreaming solar wind halo electron events on open field lines?</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gosling, J. T.; Mccomas, D. J.; Phillips, J. L. 1992-01-01 Counterstreaming solar wind halo electron events have been identified as a common 1 AU signature of coronal mass ejection events, and have generally been interpreted as indicative of closed magnetic field topologies, i.e., magnetic loops or flux ropes rooted at both ends in the Sun, or detached plasmoids. In this paper we examine the possibility that these events may instead occur preferentially on open field lines, and that counterstreaming results from reflection or injection behind interplanetary shocks or from mirroring from regions of compressed magnetic field farther out in the heliosphere. We conclude that neither of these suggested sources of counterstreaming electron beams is viable and that the best interpretation of observed counterstreaming electron events in the solar wind remains that of passage of closed field structures. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li class="active">1</li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_2" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="21"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...859L..29Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...859L..29Z">Effects of Coronal Magnetic Field Structures on the Transport of Solar Energetic Particles</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhao, Lulu; Zhang, Ming 2018-06-01 This Letter presents a model calculation of solar energetic particle (SEP) transport to test the sensitivity of the distribution of escaped SEPs in interplanetary space and dependence upon the details of the magnetic field structure in the corona. It is applied to a circumsolar event on 2011 November 3, in which SEPs are observed promptly after the solar event eruption by three spacecraft (the twin Solar TErrestrial RElations Observatories (STEREO-A and STEREO-B) and ACE) separated by more than 100° in longitude from each other. The corona magnetic field reconstructed from photosphseric field measurements using the PFSS method changes substantially before and after the solar eruption, especially around the active region. The locations of open field regions, separatrix surfaces including the heliospheric current sheet, and footpoints of magnetic field lines connected to the spacecraft location have shifted substantially. We inject 100 keV energetic electrons on the open field lines at 1.5 R s within the size of observed coronal mass ejections (CMEs) and follow their propagation in the corona and the interplanetary space. We find that with a perpendicular diffusion due to field line random walk equal to 10% of the supergranular diffusion rate, the overall distribution of escaped SEPs does not change much even though the region of open field lines from SEPs has changed. The result suggests that detailed small-scale coronal magnetic field structures and the exact magnetic field connection are not crucially important for observing SEPs in the interplanetary space. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM42A..03G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM42A..03G">Magnetic reconnection in 3D magnetosphere models: magnetic separators and open flux production</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Glocer, A.; Dorelli, J.; Toth, G.; Komar, C. M.; Cassak, P. 2014-12-01 There are multiple competing definitions of magnetic reconnection in 3D (e.g., Hesse and Schindler [1988], Lau and Finn [1990], and Boozer [2002]). In this work we focus on separator reconnection. A magnetic separator can be understood as the 3D analogue of a 2D x line with a guide field, and is defined by the line corresponding to the intersection of the separatrix surfaces associated with the magnetic nulls. A separator in the magnetosphere represents the intersection of four distinct magnetic topologies: solar wind, closed, open connected to the northern hemisphere, and open connected to the southern hemisphere. The integral of the parallel electric field along the separator defines the rate of open flux production, and is one measure of the reconnection rate. We present three methods for locating magnetic separators and apply them to 3D resistive MHD simulations of the Earth's magnetosphere using the BATS-R-US code. The techniques for finding separators and determining the reconnection rate are insensitive to IMF clock angle and can in principle be applied to any magnetospheric model. The present work examines cases of high and low resistivity, for two clock angles. We also examine the separator during Flux Transfer Events (FTEs) and Kelvin-Helmholtz instability. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AAS...22432351D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AAS...22432351D">Solar Polar Jets Driven by Magnetic Reconnection, Gravity, and Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> DeVore, C. Richard; Karpen, Judith T.; Antiochos, Spiro K. 2014-06-01 Polar jets are dynamic, narrow, radially extended structures observed in solar EUV emission near the limb. They originate within the open field of coronal holes in “anemone” regions, which are intrusions of opposite magnetic polarity. The key topological feature is a magnetic null point atop a dome-shaped fan surface of field lines. Applied stresses readily distort the null into a current patch, eventually inducing interchange reconnection between the closed and open fields inside and outside the fan surface (Antiochos 1996). Previously, we demonstrated that magnetic free energy stored on twisted closed field lines inside the fan surface is released explosively by the onset of fast reconnection across the current patch (Pariat et al. 2009, 2010). A dense jet comprised of a nonlinear, torsional Alfvén wave is ejected into the outer corona along the newly reconnected open field lines. Now we are extending those exploratory simulations by including the effects of solar gravity, solar wind, and expanding spherical geometry. We find that the model remains robust in the resulting more complex setting, with explosive energy release and dense jet formation occurring in the low corona due to the onset of a kink-like instability, as found in the earlier Cartesian, gravity-free, static-atmosphere cases. The spherical-geometry jet including gravity and wind propagates far more rapidly into the outer corona and inner heliosphere than a comparison jet simulation that excludes those effects. We report detailed analyses of our new results, compare them with previous work, and discuss the implications for understanding remote and in-situ observations of solar polar jets.This work was supported by NASA’s LWS TR&T program. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E.149A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E.149A">MASC: Magnetic Activity of the Solar Corona</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Auchere, Frederic; Fineschi, Silvano; Gan, Weiqun; Peter, Hardi; Vial, Jean-Claude; Zhukov, Andrei; Parenti, Susanna; Li, Hui; Romoli, Marco We present MASC, an innovative payload designed to explore the magnetic activity of the solar corona. It is composed of three complementary instruments: a Hard-X-ray spectrometer, a UV / EUV imager, and a Visible Light / UV polarimetric coronagraph able to measure the coronal magnetic field. The solar corona is structured in magnetically closed and open structures from which slow and fast solar winds are respectively released. In spite of much progress brought by two decades of almost uninterrupted observations from several space missions, the sources and acceleration mechanisms of both types are still not understood. This continuous expansion of the solar atmosphere is disturbed by sporadic but frequent and violent events. Coronal mass ejections (CMEs) are large-scale massive eruptions of magnetic structures out of the corona, while solar flares trace the sudden heating of coronal plasma and the acceleration of electrons and ions to high, sometimes relativistic, energies. Both phenomena are most probably driven by instabilities of the magnetic field in the corona. The relations between flares and CMEs are still not understood in terms of initiation and energy partition between large-scale motions, small-scale heating and particle acceleration. The initiation is probably related to magnetic reconnection which itself results magnetic topological changes due to e.g. flux emergence, footpoints motions, etc. Acceleration and heating are also strongly coupled since the atmospheric heating is thought to result from the impact of accelerated particles. The measurement of both physical processes and their outputs is consequently of major importance. However, despite its fundamental importance as a driver for the physics of the Sun and of the heliosphere, the magnetic field of our star’s outer atmosphere remains poorly understood. This is due in large part to the fact that the magnetic field is a very difficult quantity to measure. Our knowledge of its strength and </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PEPI..187...78H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PEPI..187...78H">Solar magnetic fields</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hood, Alan W.; Hughes, David W. 2011-08-01 This review provides an introduction to the generation and evolution of the Sun's magnetic field, summarising both observational evidence and theoretical models. The eleven year solar cycle, which is well known from a variety of observed quantities, strongly supports the idea of a large-scale solar dynamo. Current theoretical ideas on the location and mechanism of this dynamo are presented. The solar cycle influences the behaviour of the global coronal magnetic field and it is the eruptions of this field that can impact on the Earth's environment. These global coronal variations can be modelled to a surprising degree of accuracy. Recent high resolution observations of the Sun's magnetic field in quiet regions, away from sunspots, show that there is a continual evolution of a small-scale magnetic field, presumably produced by small-scale dynamo action in the solar interior. Sunspots, a natural consequence of the large-scale dynamo, emerge, evolve and disperse over a period of several days. Numerical simulations can help to determine the physical processes governing the emergence of sunspots. We discuss the interaction of these emerging fields with the pre-existing coronal field, resulting in a variety of dynamic phenomena. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...850...45R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...850...45R">Global Solar Magnetic Field Organization in the Outer Corona: Influence on the Solar Wind Speed and Mass Flux Over the Cycle</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Réville, Victor; Brun, Allan Sacha 2017-11-01 The dynamics of the solar wind depends intrinsically on the structure of the global solar magnetic field, which undergoes fundamental changes over the 11-year solar cycle. For instance, the wind terminal velocity is thought to be anti-correlated with the expansion factor, a measure of how the magnetic field varies with height in the solar corona, usually computed at a fixed height (≈ 2.5 {R}⊙ , the source surface radius that approximates the distance at which all magnetic field lines become open). However, the magnetic field expansion affects the solar wind in a more detailed way, its influence on the solar wind properties remaining significant well beyond the source surface. We demonstrate this using 3D global magnetohydrodynamic (MHD) simulations of the solar corona, constrained by surface magnetograms over half a solar cycle (1989-2001). A self-consistent expansion beyond the solar wind critical point (even up to 10 {R}⊙ ) makes our model comply with observed characteristics of the solar wind, namely, that the radial magnetic field intensity becomes latitude independent at some distance from the Sun, and that the mass flux is mostly independent of the terminal wind speed. We also show that near activity minimum, the expansion in the higher corona has more influence on the wind speed than the expansion below 2.5 {R}⊙ . </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.nrel.gov/news/press/1999/5199homes.html','SCIGOVWS'); return false;" href="https://www.nrel.gov/news/press/1999/5199homes.html">Tour Opens Doors to Solar Homes</a> <a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a> , 1999 Â The Tour of Solar Homes will open the doors of hundreds of passive and active solar homes available for $5 at NREL's Visitors Center on the day of the tour. The Visitors Center will open at 9 a.m solar electric systems, will be open 10 a.m. to 4 p.m. Ever wonder what it would feel like to live in a </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AnGeo..35.1293B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AnGeo..35.1293B">Open and partially closed models of the solar wind interaction with outer planet magnetospheres: the case of Saturn</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Belenkaya, Elena S.; Cowley, Stanley W. H.; Alexeev, Igor I.; Kalegaev, Vladimir V.; Pensionerov, Ivan A.; Blokhina, Marina S.; Parunakian, David A. 2017-12-01 A wide variety of interactions take place between the magnetized solar wind plasma outflow from the Sun and celestial bodies within the solar system. Magnetized planets form magnetospheres in the solar wind, with the planetary field creating an obstacle in the flow. The reconnection efficiency of the solar-wind-magnetized planet interaction depends on the conditions in the magnetized plasma flow passing the planet. When the reconnection efficiency is very low, the interplanetary magnetic field (IMF) does not penetrate the magnetosphere, a condition that has been widely discussed in the recent literature for the case of Saturn. In the present paper, we study this issue for Saturn using Cassini magnetometer data, images of Saturn's ultraviolet aurora obtained by the HST, and the paraboloid model of Saturn's magnetospheric magnetic field. Two models are considered: first, an open model in which the IMF penetrates the magnetosphere, and second, a partially closed model in which field lines from the ionosphere go to the distant tail and interact with the solar wind at its end. We conclude that the open model is preferable, which is more obvious for southward IMF. For northward IMF, the model calculations do not allow us to reach definite conclusions. However, analysis of the observations available in the literature provides evidence in favor of the open model in this case too. The difference in magnetospheric structure for these two IMF orientations is due to the fact that the reconnection topology and location depend on the relative orientation of the IMF vector and the planetary dipole magnetic moment. When these vectors are parallel, two-dimensional reconnection occurs at the low-latitude neutral line. When they are antiparallel, three-dimensional reconnection takes place in the cusp regions. Different magnetospheric topologies determine different mapping of the open-closed boundary in the ionosphere, which can be considered as a proxy for the poleward edge of the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ApJ...719...28D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ApJ...719...28D">A Model of Magnetic Braking of Solar Rotation that Satisfies Observational Constraints</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Denissenkov, Pavel A. 2010-08-01 The model of magnetic braking of solar rotation considered by Charbonneau & MacGregor has been modified so that it is able to reproduce for the first time the rotational evolution of both the fastest and slowest rotators among solar-type stars in open clusters of different ages, without coming into conflict with other observational constraints, such as the time evolution of the atmospheric Li abundance in solar twins and the thinness of the solar tachocline. This new model assumes that rotation-driven turbulent diffusion, which is thought to amplify the viscosity and magnetic diffusivity in stellar radiative zones, is strongly anisotropic with the horizontal components of the transport coefficients strongly dominating over those in the vertical direction. Also taken into account is the poloidal field decay that helps to confine the width of the tachocline at the solar age. The model's properties are investigated by numerically solving the azimuthal components of the coupled momentum and magnetic induction equations in two dimensions using a finite element method. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5518764','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5518764">Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Owens, Mathew J.; Imber, Suzanne M.; James, Matthew K.; Bunce, Emma J.; Yeoman, Timothy K. 2017-01-01 Abstract Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25. PMID:28781930 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28781930','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28781930">Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lockwood, Mike; Owens, Mathew J; Imber, Suzanne M; James, Matthew K; Bunce, Emma J; Yeoman, Timothy K 2017-06-01 Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21455040-model-magnetic-braking-solar-rotation-satisfies-observational-constraints','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21455040-model-magnetic-braking-solar-rotation-satisfies-observational-constraints">A MODEL OF MAGNETIC BRAKING OF SOLAR ROTATION THAT SATISFIES OBSERVATIONAL CONSTRAINTS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Denissenkov, Pavel A., E-mail: pavel.denisenkov@gmail.co The model of magnetic braking of solar rotation considered by Charbonneau and MacGregor has been modified so that it is able to reproduce for the first time the rotational evolution of both the fastest and slowest rotators among solar-type stars in open clusters of different ages, without coming into conflict with other observational constraints, such as the time evolution of the atmospheric Li abundance in solar twins and the thinness of the solar tachocline. This new model assumes that rotation-driven turbulent diffusion, which is thought to amplify the viscosity and magnetic diffusivity in stellar radiative zones, is strongly anisotropic withmore » the horizontal components of the transport coefficients strongly dominating over those in the vertical direction. Also taken into account is the poloidal field decay that helps to confine the width of the tachocline at the solar age. The model's properties are investigated by numerically solving the azimuthal components of the coupled momentum and magnetic induction equations in two dimensions using a finite element method.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760017040','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760017040">The large-scale magnetic field in the solar wind. [astronomical models of interplanetary magnetics and the solar magnetic field</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Burlaga, L. F.; Ness, N. F. 1976-01-01 A literature review is presented of theoretical models of the interaction of the solar wind and interplanetary magnetic fields. Observations of interplanetary magnetic fields by the IMP and OSO spacecraft are discussed. The causes for cosmic ray variations (Forbush decreases) by the solar wind are examined. The model of Parker is emphasized. This model shows the three dimensional magnetic field lines of the solar wind to have the form of spirals wrapped on cones. It is concluded that an out-of-the-ecliptic solar probe mission would allow the testing and verification of the various theoretical models examined. Diagrams of the various models are shown. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29374211','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29374211">Low Altitude Solar Magnetic Reconnection, Type III Solar Radio Bursts, and X-ray Emissions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cairns, I H; Lobzin, V V; Donea, A; Tingay, S J; McCauley, P I; Oberoi, D; Duffin, R T; Reiner, M J; Hurley-Walker, N; Kudryavtseva, N A; Melrose, D B; Harding, J C; Bernardi, G; Bowman, J D; Cappallo, R J; Corey, B E; Deshpande, A; Emrich, D; Goeke, R; Hazelton, B J; Johnston-Hollitt, M; Kaplan, D L; Kasper, J C; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Ord, S M; Prabu, T; Roshi, A; Shankar, N Udaya; Srivani, K S; Subrahmanyan, R; Wayth, R B; Waterson, M; Webster, R L; Whitney, A R; Williams, A; Williams, C L 2018-01-26 Type III solar radio bursts are the Sun's most intense and frequent nonthermal radio emissions. They involve two critical problems in astrophysics, plasma physics, and space physics: how collective processes produce nonthermal radiation and how magnetic reconnection occurs and changes magnetic energy into kinetic energy. Here magnetic reconnection events are identified definitively in Solar Dynamics Observatory UV-EUV data, with strong upward and downward pairs of jets, current sheets, and cusp-like geometries on top of time-varying magnetic loops, and strong outflows along pairs of open magnetic field lines. Type III bursts imaged by the Murchison Widefield Array and detected by the Learmonth radiospectrograph and STEREO B spacecraft are demonstrated to be in very good temporal and spatial coincidence with specific reconnection events and with bursts of X-rays detected by the RHESSI spacecraft. The reconnection sites are low, near heights of 5-10 Mm. These images and event timings provide the long-desired direct evidence that semi-relativistic electrons energized in magnetic reconnection regions produce type III radio bursts. Not all the observed reconnection events produce X-ray events or coronal or interplanetary type III bursts; thus different special conditions exist for electrons leaving reconnection regions to produce observable radio, EUV, UV, and X-ray bursts. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21452847-major-electron-events-coronal-magnetic-configurations-related-solar-active-regions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21452847-major-electron-events-coronal-magnetic-configurations-related-solar-active-regions">MAJOR ELECTRON EVENTS AND CORONAL MAGNETIC CONFIGURATIONS OF THE RELATED SOLAR ACTIVE REGIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Li, C.; Owen, C. J.; Matthews, S. A. A statistical survey of 26 major electron events during the period 2002 February through the end of solar cycle 23 is presented. We have obtained electron solar onset times and the peak flux spectra for each event by fitting to a power-law spectrum truncated by an exponential high-energy tail, i.e., f(E){approx}E{sup -{delta}}e{sup -E/E{sub 0}}. We also derived the coronal magnetic configurations of the related solar active regions (ARs) from the potential-field source-surface model. It is found that (1) 10 of the 11 well-connected open field-line events are prompt events whose solar onset times coincide with the maxima of flare emissionmore » and 13 of the 14 closed field-line events are delayed events. (2) A not-well-connected open field-line event and one of the closed field-line events are prompt events, they are both associated with large-scale coronal disturbances or dimming. (3) An averaged harder spectrum is found in open field-line events compared with the closed ones. Specifically, the averaged spectral index {delta} is of 1.6 {+-} 0.3 in open field-line events and of 2.0 {+-} 0.4 in closed ones. The spectra of three closed field-line events show infinite rollover energies E {sub 0}. These correlations clearly establish a significant link between the coronal magnetic field-line topology and the escape of charged particles from the flaring ARs into interplanetary space during the major solar energetic particle events.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22679874-precipitation-release-solar-energetic-particles-from-solar-coronal-magnetic-field','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22679874-precipitation-release-solar-energetic-particles-from-solar-coronal-magnetic-field">Precipitation and Release of Solar Energetic Particles from the Solar Coronal Magnetic Field</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Zhang, Ming; Zhao, Lulu, E-mail: mzhang@fit.edu Most solar energetic particles (SEPs) are produced in the corona. They propagate through complex coronal magnetic fields subject to scattering and diffusion across the averaged field lines by turbulence. We examine the behaviors of particle transport using a stochastic 3D focused transport simulation in a potential field source surface model of coronal magnetic field. The model is applied to an SEP event on 2010 February 7. We study three scenarios of particle injection at (i) the compact solar flare site, (ii) the coronal mass ejection (CME) shock, and (iii) the EUV wave near the surface. The majority of particles injectedmore » on open field lines are able to escape the corona. We found that none of our models can explain the observations of wide longitudinal SEP spread without perpendicular diffusion. If the perpendicular diffusion is about 10% of what is derived from the random walk of field lines at the rate of supergranular diffusion, particles injected at the compact solar flare site can spread to a wide range of longitude and latitude, very similar to the behavior of particles injected at a large CME shock. Stronger pitch-angle scattering results in a little more lateral spread by holding the particles in the corona for longer periods of time. Some injected particles eventually end up precipitating onto the solar surface. Even with a very small perpendicular diffusion, the pattern of the particle precipitation can be quite complicated depending on the detailed small-scale coronal magnetic field structures, which could be seen with future sensitive gamma-ray telescopes.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...846..107Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...846..107Z">Precipitation and Release of Solar Energetic Particles from the Solar Coronal Magnetic Field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhang, Ming; Zhao, Lulu 2017-09-01 Most solar energetic particles (SEPs) are produced in the corona. They propagate through complex coronal magnetic fields subject to scattering and diffusion across the averaged field lines by turbulence. We examine the behaviors of particle transport using a stochastic 3D focused transport simulation in a potential field source surface model of coronal magnetic field. The model is applied to an SEP event on 2010 February 7. We study three scenarios of particle injection at (I) the compact solar flare site, (II) the coronal mass ejection (CME) shock, and (III) the EUV wave near the surface. The majority of particles injected on open field lines are able to escape the corona. We found that none of our models can explain the observations of wide longitudinal SEP spread without perpendicular diffusion. If the perpendicular diffusion is about 10% of what is derived from the random walk of field lines at the rate of supergranular diffusion, particles injected at the compact solar flare site can spread to a wide range of longitude and latitude, very similar to the behavior of particles injected at a large CME shock. Stronger pitch-angle scattering results in a little more lateral spread by holding the particles in the corona for longer periods of time. Some injected particles eventually end up precipitating onto the solar surface. Even with a very small perpendicular diffusion, the pattern of the particle precipitation can be quite complicated depending on the detailed small-scale coronal magnetic field structures, which could be seen with future sensitive gamma-ray telescopes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060044031&hterms=corona&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dcorona','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060044031&hterms=corona&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dcorona">Ultra-fine-scale filamentary structures in the Outer Corona and the Solar Magnetic Field</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Woo, Richard 2006-01-01 Filamentary structures following magnetic field lines pervade the Sun's atmosphere and offer us insight into the solar magnetic field. Radio propagation measurements have shown that the smallest filamentary structures in the solar corona are more than 2 orders of magnitude finer than those seen in solar imaging. Here we use radio Doppler measurements to characterize their transverse density gradient and determine their finest scale in the outer corona at 20-30 R(circled dot operator), where open magnetic fields prevail. Filamentary structures overly active regions have the steepest gradient and finest scale, while those overlying coronal holes have the shallowest gradient and least finest scale. Their organization by the underlying corona implies that these subresolution structures extend radially from the entire Sun, confirming that they trace the coronal magnetic field responsible for the radial expansion of the solar wind. That they are rooted all over the Sun elucidates the association between the magnetic field of the photosphere and that of the corona, as revealed by the similarity between the power spectra of the photospheric field and the coronal density fluctuations. This association along with the persistence of filamentary structures far from the Sun demonstrate that subresolution magnetic fields must play an important role not only in magnetic coupling of the photosphere and corona, but also in coronal heating and solar wind acceleration through the process of small-scale magnetic reconnection. They also explain why current widely used theoretical models that extrapolate photospheric magnetic fields into the corona do not predict the correct source of the solar wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH31C2444U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH31C2444U">Constraining Large-Scale Solar Magnetic Field Models with Optical Coronal Observations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Uritsky, V. M.; Davila, J. M.; Jones, S. I. 2015-12-01 Scientific success of the Solar Probe Plus (SPP) and Solar Orbiter (SO) missions will depend to a large extent on the accuracy of the available coronal magnetic field models describing the connectivity of plasma disturbances in the inner heliosphere with their source regions. We argue that ground based and satellite coronagraph images can provide robust geometric constraints for the next generation of improved coronal magnetic field extrapolation models. In contrast to the previously proposed loop segmentation codes designed for detecting compact closed-field structures above solar active regions, we focus on the large-scale geometry of the open-field coronal regions located at significant radial distances from the solar surface. Details on the new feature detection algorithms will be presented. By applying the developed image processing methodology to high-resolution Mauna Loa Solar Observatory images, we perform an optimized 3D B-line tracing for a full Carrington rotation using the magnetic field extrapolation code presented in a companion talk by S.Jones at al. Tracing results are shown to be in a good qualitative agreement with the large-scalie configuration of the optical corona. Subsequent phases of the project and the related data products for SSP and SO missions as wwll as the supporting global heliospheric simulations will be discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM43E..06X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM43E..06X">Characterization of the Martian magnetic topology response to extreme solar transient events with MGS data</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xu, S.; Curry, S.; Mitchell, D. L.; Luhmann, J. G.; Lillis, R. J.; Dong, C. 2017-12-01 Characterizing how the solar cycle affects the physics of the Mars-solar wind interaction can improve our understanding of Mars' atmospheric evolution and the plasma environment at Mars. In particular, solar transient events such as Interplanetary Coronal Mass Ejections (ICMEs) and Stream Interaction Regions (SIRs) significantly change the solar-wind interaction, including the magnetic topology and ion acceleration. However, both the Mars Express and Mars Atmosphere Volatile EvolutioN (MAVEN) missions have encountered relatively few extreme solar transient events due to the recent low solar activity (2004-2017). In contrast, Mars Global Surveyor (MGS) was operating during a relatively active solar maximum (1999-2003). Based on new results from MAVEN, this study reanalyzes MGS data to better understand how the Martian plasma environment responds to extreme solar events. In particular, we aim to investigate how the magnetic topology during these extreme events differs from the topology during quiet times. We conduct orbit comparisons of the magnetic topology inferred from MGS electron pitch angle distributions during quiet periods and extreme events to determine how the open and closed field patterns respond to extreme events. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_3" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="41"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...848...70L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...848...70L">The Open Flux Problem</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Linker, J. A.; Caplan, R. M.; Downs, C.; Riley, P.; Mikic, Z.; Lionello, R.; Henney, C. J.; Arge, C. N.; Liu, Y.; Derosa, M. L.; Yeates, A.; Owens, M. J. 2017-10-01 The heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun’s photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. In this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun’s magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22679762-open-flux-problem','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22679762-open-flux-problem">The Open Flux Problem</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Linker, J. A.; Caplan, R. M.; Downs, C. The heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun’s photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. Inmore » this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun’s magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22078548-solar-magnetized-tornadoes-relation-filaments','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22078548-solar-magnetized-tornadoes-relation-filaments">SOLAR MAGNETIZED 'TORNADOES': RELATION TO FILAMENTS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Su Yang; Veronig, Astrid; Temmer, Manuela Solar magnetized 'tornadoes', a phenomenon discovered in the solar atmosphere, appear as tornado-like structures in the corona but are rooted in the photosphere. Like other solar phenomena, solar tornadoes are a feature of magnetized plasma and therefore differ distinctly from terrestrial tornadoes. Here we report the first analysis of solar 'tornadoes' (two papers which focused on different aspects of solar tornadoes were published in the Astrophysical Journal Letters and Nature, respectively, during the revision of this Letter). A detailed case study of two events indicates that they are rotating vertical magnetic structures probably driven by underlying vortex flows in themore » photosphere. They usually exist as a group and are related to filaments/prominences, another important solar phenomenon whose formation and eruption are still mysteries. Solar tornadoes may play a distinct role in the supply of mass and twists to filaments. These findings could lead to a new explanation of filament formation and eruption.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100015554&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DOpen%2BField','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100015554&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DOpen%2BField">Evidence in Magnetic Clouds for Systematic Open Flux Transport on the Sun</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Crooker, N. U.; Kahler, S. W.; Gosling, J. T.; Lepping, R. P. 2008-01-01 Most magnetic clouds encountered by spacecraft at 1 AU display a mix of unidirectional suprathermal electrons signaling open field lines and counterstreaming electrons signaling loops connected to the Sun at both ends. Assuming the open fields were originally loops that underwent interchange reconnection with open fields at the Sun, we determine the sense of connectedness of the open fields found in 72 of 97 magnetic clouds identified by the Wind spacecraft in order to obtain information on the location and sense of the reconnection and resulting flux transport at the Sun. The true polarity of the open fields in each magnetic cloud was determined from the direction of the suprathermal electron flow relative to the magnetic field direction. Results indicate that the polarity of all open fields within a given magnetic cloud is the same 89% of the time, implying that interchange reconnection at the Sun most often occurs in only one leg of a flux rope loop, thus transporting open flux in a single direction, from a coronal hole near that leg to the foot point of the opposite leg. This pattern is consistent with the view that interchange reconnection in coronal mass ejections systematically transports an amount of open flux sufficient to reverse the polarity of the heliospheric field through the course of the solar cycle. Using the same electron data, we also find that the fields encountered in magnetic clouds are only a third as likely to be locally inverted as not. While one might expect inversions to be equally as common as not in flux rope coils, consideration of the geometry of spacecraft trajectories relative to the modeled magnetic cloud axes leads us to conclude that the result is reasonable. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH13A2473P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH13A2473P">Using the Solar Polar Magnetic Field for Longterm Predictions of Solar Activity, Solar Cycles 21-25</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pesnell, W. D.; Schatten, K. H. 2017-12-01 We briefly review the dynamo and geomagnetic precursor methods of long-term solar activity forecasting. These methods depend upon the most basic aspect of dynamo theory to predict future activity, future magnetic field arises directly from the amplification of pre-existing magnetic field. We then generalize the dynamo technique, allowing the method to be used at any phase of the solar cycle, to the Solar Dynamo Amplitude (SODA) index. This index is sensitive to the magnetic flux trapped within the Sun's convection zone but insensitive to the phase of the solar cycle. Since magnetic fields inside the Sun can become buoyant, one may think of the acronym SODA as describing the amount of buoyant flux. We will show how effective the SODA Index has been in predicting Solar Cycles 23 and 24, and present a unified picture of earlier estimates of the polar magnetic configuration in Solar Cycle 21 and 22. Using the present value of the SODA index, we estimate that the next cycle's smoothed peak activity will be about 125 ± 30 solar flux units for the 10.7 cm radio flux and a sunspot number of 70 ± 25. This suggests that Solar Cycle 25 will be comparable to Solar Cycle 24. Since the current approach uses data prior to solar minimum, these estimates may improve when the upcoming solar minimum is reached. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015FrASS...2....2M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015FrASS...2....2M">Deciphering Solar Magnetic Activity: On Grand Minima in Solar Activity</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mcintosh, Scott; Leamon, Robert 2015-07-01 The Sun provides the energy necessary to sustain our existence. While the Sun provides for us, it is also capable of taking away. The weather and climatic scales of solar evolution and the Sun-Earth connection are not well understood. There has been tremendous progress in the century since the discovery of solar magnetism - magnetism that ultimately drives the electromagnetic, particulate and eruptive forcing of our planetary system. There is contemporary evidence of a decrease in solar magnetism, perhaps even indicators of a significant downward trend, over recent decades. Are we entering a minimum in solar activity that is deeper and longer than a typical solar minimum, a "grand minimum"? How could we tell if we are? What is a grand minimum and how does the Sun recover? These are very pertinent questions for modern civilization. In this paper we present a hypothetical demonstration of entry and exit from grand minimum conditions based on a recent analysis of solar features over the past 20 years and their possible connection to the origins of the 11(-ish) year solar activity cycle. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850021557','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850021557">Measurements of Solar Vector Magnetic Fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hagyard, M. J. (Editor) 1985-01-01 Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH43B2460T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH43B2460T">The Coronal Solar Magnetism Observatory</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tomczyk, S.; Landi, E.; Zhang, J.; Lin, H.; DeLuca, E. E. 2015-12-01 Measurements of coronal and chromospheric magnetic fields are arguably the most important observables required for advances in our understanding of the processes responsible for coronal heating, coronal dynamics and the generation of space weather that affects communications, GPS systems, space flight, and power transmission. The Coronal Solar Magnetism Observatory (COSMO) is a proposed ground-based suite of instruments designed for routine study of coronal and chromospheric magnetic fields and their environment, and to understand the formation of coronal mass ejections (CME) and their relation to other forms of solar activity. This new facility will be operated by the High Altitude Observatory of the National Center for Atmospheric Research (HAO/NCAR) with partners at the University of Michigan, the University of Hawaii and George Mason University in support of the solar and heliospheric community. It will replace the current NCAR Mauna Loa Solar Observatory (http://mlso.hao.ucar.edu). COSMO will enhance the value of existing and new observatories on the ground and in space by providing unique and crucial observations of the global coronal and chromospheric magnetic field and its evolution. The design and current status of the COSMO will be reviewed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SoPh..292..121K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SoPh..292..121K">Contribution to the Solar Mean Magnetic Field from Different Solar Regions</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kutsenko, A. S.; Abramenko, V. I.; Yurchyshyn, V. B. 2017-09-01 Seven-year-long seeing-free observations of solar magnetic fields with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) were used to study the sources of the solar mean magnetic field, SMMF, defined as the net line-of-sight magnetic flux divided over the solar disk area. To evaluate the contribution of different regions to the SMMF, we separated all the pixels of each SDO/HMI magnetogram into three subsets: weak (BW), intermediate (BI), and strong (BS) fields. The BW component represents areas with magnetic flux densities below the chosen threshold; the BI component is mainly represented by network fields, remains of decayed active regions (ARs), and ephemeral regions. The BS component consists of magnetic elements in ARs. To derive the contribution of a subset to the total SMMF, the linear regression coefficients between the corresponding component and the SMMF were calculated. We found that i) when the threshold level of 30 Mx cm-2 is applied, the BI and BS components together contribute from 65% to 95% of the SMMF, while the fraction of the occupied area varies in a range of 2 - 6% of the disk area; ii) as the threshold magnitude is lowered to 6 Mx cm-2, the contribution from BI+BS grows to 98%, and the fraction of the occupied area reaches a value of about 40% of the solar disk. In summary, we found that regardless of the threshold level, only a small part of the solar disk area contributes to the SMMF. This means that the photospheric magnetic structure is an intermittent inherently porous medium, resembling a percolation cluster. These findings suggest that the long-standing concept that continuous vast unipolar areas on the solar surface are the source of the SMMF may need to be reconsidered. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH41E..02B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH41E..02B">Magnetic Flux Transients during Solar Flares</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Balasubramaniam, K. S.; Delgado, F.; Hock, R. A. 2013-12-01 Solar flares result from the sudden release of energy stored in the magnetic field of the solar atmosphere, attributed to magnetic reconnection. In this work, we use line-of-sight magnetograms to study the changes in photospheric magnetic field during large solar flares. The magnetograms are derived from observations using NASA's Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory, and have a cadence of 3 minutes at a 0.5 arcsecond spatial resolution. We studied the inferred magnetic flux changes in 11 X-class flares from (2011-2012) and 26 M-class flares (2011). Of the 37 flares, 32 exhibited short-lived (less than 30 minutes) magnetic flux transients (MFTs) during the progress of the flare, similar to those by Maurya et al. (2012). We note that MFTs were co-temporal with GOES X-ray peaks. Flares with rapid rises (impulsive flares) had stronger transients while those with slower rises (gradual flares) had weak or no MFTs. Finally, flares with stronger GOES X-ray peaks (flare class) showed stronger MFTs. We believe that these changes are non-physical because the changes in the magnetic field are transient (the magnetic field returns to the pre-flare state) and coincide with the impulsive phase of the flare. This work supported by the US Airforce Office of Scientific Research and the AFRL/RV Space Scholar Program. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMIN51F..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMIN51F..06H">Embracing Open Software Development in Solar Physics</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hughitt, V. K.; Ireland, J.; Christe, S.; Mueller, D. 2012-12-01 We discuss two ongoing software projects in solar physics that have adopted best practices of the open source software community. The first, the Helioviewer Project, is a powerful data visualization tool which includes online and Java interfaces inspired by Google Maps (tm). This effort allows users to find solar features and events of interest, and download the corresponding data. Having found data of interest, the user now has to analyze it. The dominant solar data analysis platform is an open-source library called SolarSoft (SSW). Although SSW itself is open-source, the programming language used is IDL, a proprietary language with licensing costs that are prohibative for many institutions and individuals. SSW is composed of a collection of related scripts written by missions and individuals for solar data processing and analysis, without any consistent data structures or common interfaces. Further, at the time when SSW was initially developed, many of the best software development processes of today (mirrored and distributed version control, unit testing, continuous integration, etc.) were not standard, and have not since been adopted. The challenges inherent in developing SolarSoft led to a second software project known as SunPy. SunPy is an open-source Python-based library which seeks to create a unified solar data analysis environment including a number of core datatypes such as Maps, Lightcurves, and Spectra which have consistent interfaces and behaviors. By taking advantage of the large and sophisticated body of scientific software already available in Python (e.g. SciPy, NumPy, Matplotlib), and by adopting many of the best practices refined in open-source software development, SunPy has been able to develop at a very rapid pace while still ensuring a high level of reliability. The Helioviewer Project and SunPy represent two pioneering technologies in solar physics - simple yet flexible data visualization and a powerful, new data analysis environment. We </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140000631','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140000631">Magnetic Untwisting in Most Solar X-Ray Jets</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Moore, Ronald; Sterling, Alphonse; Falconer, David; Robe, Dominic 2013-01-01 From 54 X-ray jets observed in the polar coronal holes by Hinode's X-Ray Telescope (XRT) during coverage in movies from Solar Dynamic Observatory's Atmospheric Imaging Assembly (AIA) taken in its He II 304 Å band at a cadence of 12 s, we have established a basic characteristic of solar X-ray jets: untwisting motion in the spire. In this presentation, we show the progression of few of these X-ray jets in XRT images and track their untwisting in AIA He II images. From their structure displayed in their XRT movies, 19 jets were evidently standard jets made by interchange reconnection of the magnetic-arcade base with ambient open field, 32 were evidently blowout jets made by blowout eruption of the base arcade, and 3 were of ambiguous form. As was anticipated from the >10,000 km span of the base arcade in most polar X-ray jets and from the disparity of standard jets and blowout jets in their magnetic production, few of the standard X-ray jets (3 of 19) but nearly all of the blowout X-ray jets (29 of 32) carried enough cool (T is approximately 105 K) plasma to be seen in their He II movies. In the 32 X-ray jets that showed a cool component, the He II movies show 10-100 km/s untwisting motions about the axis of the spire in all 3 standard jets and in 26 of the 29 blowout jets. Evidently, the open magnetic field in nearly all blowout X-ray jets and probably in most standard X-ray jets carries transient twist. This twist apparently relaxes by propagating out along the open field as a torsional wave. High-resolution spectrograms and Dopplergrams have shown that most Type-II spicules have torsional motions of 10-30 km/s. Our observation of similar torsional motion in X-ray jets strengthens the case for Type-II spicules being made in the same way as X-ray jets, by blowout eruption of a twisted magnetic arcade in the spicule base and/or by interchange reconnection of the twisted base arcade with the ambient open field. This work was funded by NASA's Heliophysics Division </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22525314-time-dependent-turbulent-heating-open-flux-tubes-chromosphere-corona-solar-wind','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22525314-time-dependent-turbulent-heating-open-flux-tubes-chromosphere-corona-solar-wind">TIME-DEPENDENT TURBULENT HEATING OF OPEN FLUX TUBES IN THE CHROMOSPHERE, CORONA, AND SOLAR WIND</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Woolsey, L. N.; Cranmer, S. R., E-mail: lwoolsey@cfa.harvard.edu We investigate several key questions of plasma heating in open-field regions of the corona that connect to the solar wind. We present results for a model of Alfvén-wave-driven turbulence for three typical open magnetic field structures: a polar coronal hole, an open flux tube neighboring an equatorial streamer, and an open flux tube near a strong-field active region. We compare time-steady, one-dimensional turbulent heating models against fully time-dependent three-dimensional reduced-magnetohydrodynamic modeling of BRAID. We find that the time-steady results agree well with time-averaged results from BRAID. The time dependence allows us to investigate the variability of the magnetic fluctuations andmore » of the heating in the corona. The high-frequency tail of the power spectrum of fluctuations forms a power law whose exponent varies with height, and we discuss the possible physical explanation for this behavior. The variability in the heating rate is bursty and nanoflare-like in nature, and we analyze the amount of energy lost via dissipative heating in transient events throughout the simulation. The average energy in these events is 10{sup 21.91} erg, within the “picoflare” range, and many events reach classical “nanoflare” energies. We also estimated the multithermal distribution of temperatures that would result from the heating-rate variability, and found good agreement with observed widths of coronal differential emission measure distributions. The results of the modeling presented in this paper provide compelling evidence that turbulent heating in the solar atmosphere by Alfvén waves accelerates the solar wind in open flux tubes.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJS..228....4Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJS..228....4Z">An Anomalous Composition in Slow Solar Wind as a Signature of Magnetic Reconnection in its Source Region</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhao, L.; Landi, E.; Lepri, S. T.; Kocher, M.; Zurbuchen, T. H.; Fisk, L. A.; Raines, J. M. 2017-01-01 In this paper, we study a subset of slow solar winds characterized by an anomalous charge state composition and ion temperatures compared to average solar wind distributions, and thus referred to as an “Outlier” wind. We find that although this wind is slower and denser than normal slow wind, it is accelerated from the same source regions (active regions and quiet-Sun regions) as the latter and its occurrence rate depends on the solar cycle. The defining property of the Outlier wind is that its charge state composition is the same as that of normal slow wind, with the only exception being a very large decrease in the abundance of fully charged species (He2+, C6+, N7+, O8+, Mg12+), resulting in a significant depletion of the He and C element abundances. Based on these observations, we suggest three possible scenarios for the origin of this wind: (1) local magnetic waves preferentially accelerating non-fully stripped ions over fully stripped ions from a loop opened by reconnection; (2) depleted fully stripped ions already contained in the corona magnetic loops before they are opened up by reconnection; or (3) fully stripped ions depleted by Coulomb collision after magnetic reconnection in the solar corona. If any one of these three scenarios is confirmed, the Outlier wind represents a direct signature of slow wind release through magnetic reconnection. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720046891&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DMagnetic%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720046891&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DMagnetic%2Benergy">Magnetic energy flow in the solar wind.</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Modisette, J. L. 1972-01-01 Discussion of the effect of rotation (tangential flow) of the solar wind on the conclusions of Whang (1971) suggesting an increase in the solar wind velocity due to the conversion of magnetic energy to kinetic energy. It is shown that the effect of the rotation of the sun on the magnetic energy flow results in most of the magnetic energy being transported by magnetic shear stress near the sun. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950054630&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOpen%2BField','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950054630&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOpen%2BField">Shear-induced opening of the coronal magnetic field</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wolfson, Richard 1995-01-01 This work describes the evolution of a model solar corona in response to motions of the footpoints of its magnetic field. The mathematics involved is semianalytic, with the only numerical solution being that of an ordinary differential equation. This approach, while lacking the flexibility and physical details of full MHD simulations, allows for very rapid computation along with complete and rigorous exploration of the model's implications. We find that the model coronal field bulges upward, at first slowly and then more dramatically, in response to footpoint displacements. The energy in the field rises monotonically from that of the initial potential state, and the field configuration and energy appraoch asymptotically that of a fully open field. Concurrently, electric currents develop and concentrate into a current sheet as the limiting case of the open field is approached. Examination of the equations shows rigorously that in the asymptotic limit of the fully open field, the current layer becomes a true ideal MHD singularity. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017109','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017109">Solar Magnetism eXplorer (Solme X)</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Peter, Hardi; Abbo, L.; Andretta, V.; Auchere, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Cassini, R.; Curdt, W.; Davila, J.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140017109'); toggleEditAbsImage('author_20140017109_show'); toggleEditAbsImage('author_20140017109_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140017109_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140017109_hide"> 2011-01-01 The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona-that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850022685','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850022685">Magnetic probing of the solar interior</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Benton, E. R.; Estes, R. H. 1985-01-01 The magnetic field patterns in the region beneath the solar photosphere is determined. An approximate method for downward extrapolation of line of sight magnetic field measurements taken at the solar photosphere was developed. It utilizes the mean field theory of electromagnetism in a form thought to be appropriate for the solar convection zone. A way to test that theory is proposed. The straightforward application of the lowest order theory with the complete model fit to these data does not indicate the existence of any reasonable depth at which flux conservation is achieved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003SPD....34.2014D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003SPD....34.2014D">Beyond Solar-B: MTRAP, the Magnetic TRAnsition Region Probe</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Davis, J. M.; Moore, R. L.; Hathaway, D. H.; Science Definition CommitteeHigh-Resolution Solar Magnetography Beyond Solar-B Team 2003-05-01 The next generation of solar missions will reveal and measure fine-scale solar magnetic fields and their effects in the solar atmosphere at heights, small scales, sensitivities, and fields of view well beyond the reach of Solar-B. The necessity for, and potential of, such observations for understanding solar magnetic fields, their generation in and below the photosphere, and their control of the solar atmosphere and heliosphere, were the focus of a science definition workshop, "High-Resolution Solar Magnetography from Space: Beyond Solar-B," held in Huntsville Alabama in April 2001. Forty internationally prominent scientists active in solar research involving fine-scale solar magnetism participated in this Workshop and reached consensus that the key science objective to be pursued beyond Solar-B is a physical understanding of the fine-scale magnetic structure and activity in the magnetic transition region, defined as the region between the photosphere and corona where neither the plasma nor the magnetic field strongly dominates the other. The observational objective requires high cadence (< 10s) vector magnetic field maps, and spatially resolved spectra from the IR, visible, vacuum UV, to the EUV at high resolution (< 50km) over a large FOV ( 140,000 km). A polarimetric resolution of one part in ten thousand is required to measure transverse magnetic fields of < 30G. The latest SEC Roadmap includes a mission identified as MTRAP to meet these requirements. Enabling technology development requirements include large, lightweight, reflecting optics, large format sensors (16K x 16K pixels) with high QE at 150 nm, and extendable spacecraft structures. The Science Organizing Committee of the Beyond Solar-B Workshop recommends that: 1. Science and Technology Definition Teams should be established in FY04 to finalize the science requirements and to define technology development efforts needed to ensure the practicality of MTRAP's observational goals. 2. The necessary </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730002035','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730002035">Coronal magnetic fields and the solar wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Newkirk, G., Jr. 1972-01-01 Current information is presented on coronal magnetic fields as they bear on problems of the solar wind. Both steady state fields and coronal transient events are considered. A brief critique is given of the methods of calculating coronal magnetic fields including the potential (current free) models, exact solutions for the solar wind and field interaction, and source surface models. These solutions are compared with the meager quantitative observations which are available at this time. Qualitative comparisons between the shapes of calculated magnetic field lines and the forms visible in the solar corona at several recent eclipses are displayed. These suggest that: (1) coronal streamers develop above extended magnetic arcades which connect unipolar regions of opposite polarity; and (2) loops, arches, and rays in the corona correspond to preferentially filled magnetic tubes in the approximately potential field. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030014815','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030014815">Interplanetary Magnetic Field Control of the Entry of Solar Energetic Particles into the Magnetosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Richard, R. L.; El-Alaoui, M.; Ashour-Abdalla, M.; Walker, R. J. 2002-01-01 We have investigated the entry of energetic ions of solar origin into the magnetosphere as a function of the interplanetary magnetic field orientation. We have modeled this entry by following high energy particles (protons and 3 He ions) ranging from 0.1 to 50 MeV in electric and magnetic fields from a global magnetohydrodynamic (MHD) model of the magnetosphere and its interaction with the solar wind. For the most part these particles entered the magnetosphere on or near open field lines except for some above 10 MeV that could enter directly by crossing field lines due to their large gyroradii. The MHD simulation was driven by a series of idealized solar wind and interplanetary magnetic field (IMF) conditions. It was found that the flux of particles in the magnetosphere and transport into the inner magnetosphere varied widely according to the IMF orientation for a constant upstream particle source, with the most efficient entry occurring under southward IMF conditions. The flux inside the magnetosphere could approach that in the solar wind implying that SEPs can contribute significantly to the magnetospheric energetic particle population during typical SEP events depending on the state of the magnetosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...852...16Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...852...16Y">Formation of Cool and Warm Jets by Magnetic Flux Emerging from the Solar Chromosphere to Transition Region</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yang, Liping; Peter, Hardi; He, Jiansen; Tu, Chuanyi; Wang, Linghua; Zhang, Lei; Yan, Limei 2018-01-01 In the solar atmosphere, jets are ubiquitous at various spatial-temporal scales. They are important for understanding the energy and mass transports in the solar atmosphere. According to recent observational studies, the high-speed network jets are likely to be intermittent but continual sources of mass and energy for the solar wind. Here, we conduct a 2D magnetohydrodynamics simulation to investigate the mechanism of these network jets. A combination of magnetic flux emergence and horizontal advection is used to drive the magnetic reconnection in the transition region between a strong magnetic loop and a background open flux. The simulation results show that not only a fast warm jet, much similar to the network jets, is found, but also an adjacent slow cool jet, mostly like classical spicules, is launched. Differing from the fast warm jet driven by magnetic reconnection, the slow cool jet is mainly accelerated by gradients of both thermal pressure and magnetic pressure near the outer border of the mass-concentrated region compressed by the emerging loop. These results provide a different perspective on our understanding of the formation of both the slow cool jets from the solar chromosphere and the fast warm jets from the solar transition region. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760044011&hterms=activity+Physics&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dactivity%2BPhysics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760044011&hterms=activity+Physics&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dactivity%2BPhysics">Recent perspectives in solar physics - Elemental composition, coronal structure and magnetic fields, solar activity</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Newkirk, G., Jr. 1975-01-01 Elemental abundances in the solar corona are studied. Abundances in the corona, solar wind and solar cosmic rays are compared to those in the photosphere. The variation in silicon and iron abundance in the solar wind as compared to helium is studied. The coronal small and large scale structure is investigated, emphasizing magnetic field activity and examining cosmic ray generation mechanisms. The corona is observed in the X-ray and EUV regions. The nature of coronal transients is discussed with emphasis on solar-wind modulation of galactic cosmic rays. A schematic plan view of the interplanetary magnetic field during sunspot minimum is given showing the presence of magnetic bubbles and their concentration in the region around 4-5 AU by a fast solar wind stream. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SSRv..186..227S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SSRv..186..227S">Magnetic Flux Emergence Along the Solar Cycle</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schmieder, B.; Archontis, V.; Pariat, E. 2014-12-01 Flux emergence plays an important role along the solar cycle. Magnetic flux emergence builds sunspot groups and solar activity. The sunspot groups contribute to the large scale behaviour of the magnetic field over the 11 year cycle and the reversal of the North and South magnetic polarity every 22 years. The leading polarity of sunspot groups is opposite in the North and South hemispheres and reverses for each new solar cycle. However the hemispheric rule shows the conservation of sign of the magnetic helicity with positive and negative magnetic helicity in the South and North hemispheres, respectively. MHD models of emerging flux have been developed over the past twenty years but have not yet succeeded to reproduce solar observations. The emergence of flux occurs through plasma layers of very high gradients of pressure and changing of modes from a large β to a low β plasma (<1). With the new armada of high spatial and temporal resolution instruments on the ground and in space, emergence of magnetic flux is observed in tremendous detail and followed during their transit through the upper atmosphere. Signatures of flux emergence in the corona depend on the pre-existing magnetic configuration and on the strength of the emerging flux. We review in this paper new and established models as well as the recent observations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030061137&hterms=magnetic+vector+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmagnetic%2Bvector%2Bpotential','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030061137&hterms=magnetic+vector+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmagnetic%2Bvector%2Bpotential">Beyond Solar-B: MTRAP, the Magnetic Transition Region Probe</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Davis, John M.; Moore, Ronald L.; Hathaway, David H. 2003-01-01 The next generation of solar missions will reveal and measure fine-scale solar magnetic fields and their effects in the solar atmosphere at heights, small scales, sensitivities, and fields of view well beyond the reach of Solar-B. The necessity for, and potential of, such observations for understanding solar magnetic fields, their generation in and below the photosphere, and their control of the solar atmosphere and heliosphere, were the focus of a science definition workshop, 'High-Resolution Solar Magnetography from Space: Beyond Solar-B,' held in Huntsville Alabama in April 2001. Forty internationally prominent scientists active in solar research involving fine-scale solar magnetism participated in this Workshop and reached consensus that the key science objective to be pursued beyond Solar-B is a physical understanding of the fine-scale magnetic structure and activity in the magnetic transition region, defined as the region between the photosphere and corona where neither the plasma nor the magnetic field strongly dominates the other. The observational objective requires high cadence (less than 10s) vector magnetic field maps, and spatially resolved spectra from the IR, visible, vacuum UV, to the EUV at high resolution (less than 50km) over a large FOV (approximately 140,000 km). A polarimetric resolution of one part in ten thousand is required to measure transverse magnetic fields of less than 30G. The latest SEC Roadmap includes a mission identified as MTRAP to meet these requirements. Enabling technology development requirements include large, lightweight, reflecting optics, large format sensors (16K x 16K pixels) with high QE at 150 nm, and extendable spacecraft structures. The Science Organizing Committee of the Beyond Solar-B Workshop recommends that: (1) Science and Technology Definition Teams should be established in FY04 to finalize the science requirements and to define technology development efforts needed to ensure the practicality of MTRAP </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009NaPho...3..649C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009NaPho...3..649C">Polymer solar cells with enhanced open-circuit voltage and efficiency</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Hsiang-Yu; Hou, Jianhui; Zhang, Shaoqing; Liang, Yongye; Yang, Guanwen; Yang, Yang; Yu, Luping; Wu, Yue; Li, Gang 2009-11-01 Following the development of the bulk heterojunction structure, recent years have seen a dramatic improvement in the efficiency of polymer solar cells. Maximizing the open-circuit voltage in a low-bandgap polymer is one of the critical factors towards enabling high-efficiency solar cells. Study of the relation between open-circuit voltage and the energy levels of the donor/acceptor in bulk heterojunction polymer solar cells has stimulated interest in modifying the open-circuit voltage by tuning the energy levels of polymers. Here, we show that the open-circuit voltage of polymer solar cells constructed based on the structure of a low-bandgap polymer, PBDTTT, can be tuned, step by step, using different functional groups, to achieve values as high as 0.76 V. This increased open-circuit voltage combined with a high short-circuit current density results in a polymer solar cell with a power conversion efficiency as high as 6.77%, as certified by the National Renewable Energy Laboratory. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170005502','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170005502">Magnetic Nulls and Super-Radial Expansion in the Solar Corona</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gibson, Sarah E.; Dalmasse, Kevin; Rachmeler, Laurel A.; De Rosa, Marc L.; Tomczyk, Steven; De Toma, Giuliana; Burkepile, Joan; Galloy, Michael 2017-01-01 Magnetic fields in the Sun's outer atmosphere, the corona, control both solar-wind acceleration and the dynamics of solar eruptions. We present the first clear observational evidence of coronal magnetic nulls in off-limb linearly polarized observations of pseudostreamers, taken by the Coronal Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where magnetic reconnection is likely to act as a catalyst for solar activity.CoMP linear-polarization observations also provide an independent, coronal proxy for magnetic expansion into the solar wind, a quantity often used to parameterize and predict the solar wind speed at Earth. We introduce a new method for explicitly calculating expansion factors from CoMP coronal linear-polarization observations, which does not require photospheric extrapolations. We conclude that linearly polarized light is a powerful new diagnostic of critical coronal magnetic topologies and the expanding magnetic flux tubes that channel the solar wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920069705&hterms=dynamo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddynamo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920069705&hterms=dynamo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddynamo">Multiple periodicities in the solar magnetic field - Possible origin in a multiple-mode solar dynamo</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Boyer, D. W.; Levy, E. H. 1992-01-01 The solar magnetic field is generated in an oscillatory mode with a 22 yr full period and gives rise to the 11 yr sunspot cycle. However, analyses of contemporary solar records, as well as other surrogate indicators of solar activity, suggest the presence also of longer term periodicities in the solar magnetic cycle. This paper suggests that the solar dynamo can operate in a multiply periodic state, with several periodicites being generated simultaneously at different depths in the convection zone. A simple two-layer model of the solar convection zone is used to illustrate the physical mechanism of spatially localized, multiple-periodicity-mode dynamo regeneration. The two layers are characterized by differences in their respective turbulent magnetic diffusivities. Although the magnetic modes interact with one another, each mode is produced large in one layer or the other, and has an oscillation period approximately equal to the time characteristic of magnetic diffusion across the layer. The observed complicated periodicity pattern in the solar magnetic field could be a combination of two (or more) dynamo modes generated in this manner. The calculations are carried out using a differential rotation model consistent with recent helioseismological measurements, illustrating the challenge to dynamo theory raised by those observational results. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AIPC..504.1588K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AIPC..504.1588K">The magnetic particle plume solar sail concept</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Knuth, William H. 2000-01-01 A magnetic particle space radiator was proposed in the late 1950s as a means to dissipate waste heat from space nuclear systems. The concept was a plume of hot magnetic particles confined to and traversing a magnetic field produced by super conducting magnets in the space vehicle. The large surface area of the hot particles was expected to effectively radiate away the heat. The cooling particles followed along the lines of the magnetic field and eventually returned to the vehicle where they again picked up a fresh charge of waste heat for return out to the plume. This paper presents a new concept for consideration. The same basic magnetic particle plume idea is proposed in this paper, except the purpose of the plume would be to receive momentum (and possibly electric power) from the solar wind in the manner of a solar sail. Recent nano-technologies allow the magnetic particles to be 2-3 orders of magnitude smaller than envisioned for the heat radiator, and the magnetic field would be stronger than we envisioned in the '50s. The application of the magnetic solar sail would be for propelling space-faring vehicles on long duration exploration of the solar system and possibly beyond. A first look is provided at the elements of the system, together with an estimate of the thrust potential and the approximate weights of the system. The system appears to have the potential to develop on the order of 50lb and 100lb of thrust and weight on the order of 15,000lb . </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009855','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009855">The Magnetic Origins of Solar Activity</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Antiochos, S. K. 2012-01-01 The defining physical property of the Sun's corona is that the magnetic field dominates the plasma. This property is the genesis for all solar activity ranging from quasi-steady coronal loops to the giant magnetic explosions observed as coronal mass ejections/eruptive flares. The coronal magnetic field is also the fundamental driver of all space weather; consequently, understanding the structure and dynamics of the field, especially its free energy, has long been a central objective in Heliophysics. The main obstacle to achieving this understanding has been the lack of accurate direct measurements of the coronal field. Most attempts to determine the magnetic free energy have relied on extrapolation of photospheric measurements, a notoriously unreliable procedure. In this presentation I will discuss what measurements of the coronal field would be most effective for understanding solar activity. Not surprisingly, the key process for driving solar activity is magnetic reconnection. I will discuss, therefore, how next-generation measurements of the coronal field will allow us to understand not only the origins of space weather, but also one of the most important fundamental processes in cosmic and laboratory plasmas. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH52A..08L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH52A..08L">How Much Energy Can Be Stored in Solar Active Region Magnetic Fields?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Linker, J.; Downs, C.; Torok, T.; Titov, V. S.; Lionello, R.; Mikic, Z.; Riley, P. 2015-12-01 Major solar eruptions such as X-class flares and very fast coronal mass ejections usually originate in active regions on the Sun. The energy that powers these events is believed to be stored as free magnetic energy (energy above the potential field state) prior to eruption. While coronal magnetic fields are not in general force-free, active regions have very strong magnetic fields and at low coronal heights the plasma beta is therefore very small, making the field (in equilibrium) essentially force-free. The Aly-Sturrock theorem shows that the energy of a fully force-free field cannot exceed the energy of the so-called open field. If the theorem holds, this places an upper limit on the amount of free energy that can be stored: the maximum free energy (MFE) is the difference between the open field energy and the potential field energy of the active region. In thermodynamic MHD simulations of a major eruption (the July 14, 2000 'Bastille' day event) and a modest event (February 13, 2009, we have found that the MFE indeed bounds the energy stored prior to eruption. We compute the MFE for major eruptive events in cycles 23 and 24 to investigate the maximum amount of energy that can be stored in solar active regions.Research supported by AFOSR, NASA, and NSF. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663665-variations-solar-parameters-cosmic-rays-solar-magnetic-polarity','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663665-variations-solar-parameters-cosmic-rays-solar-magnetic-polarity">Variations in Solar Parameters and Cosmic Rays with Solar Magnetic Polarity</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Oh, S.; Yi, Y., E-mail: suyeonoh@jnu.ac.kr The sunspot number varies with the 11-year Schwabe cycle, and the solar magnetic polarity reverses every 11 years approximately at the solar maximum. Because of polarity reversal, the difference between odd and even solar cycles is seen in solar activity. In this study, we create the mean solar cycle expressed by phase using the monthly sunspot number for all solar cycles 1–23. We also generate the mean solar cycle for sunspot area, solar radio flux, and cosmic ray flux within the allowance of observational range. The mean solar cycle has one large peak at solar maximum for odd solar cyclesmore » and two small peaks for most even solar cycles. The odd and even solar cycles have the statistical difference in value and shape at a confidence level of at least 98%. For solar cycles 19–23, the second peak in the even solar cycle is larger than the first peak. This result is consistent with the frequent solar events during the declining phase after the solar maximum. The difference between odd and even solar cycles can be explained by a combined model of polarity reversal and solar rotation. In the positive/negative polarity, the polar magnetic field introduces angular momentum in the same/opposite direction as/to the solar rotation. Thus the addition/subtraction of angular momentum can increase/decrease the motion of plasma to support the formation of sunspots. Since the polarity reverses at the solar maximum, the opposite phenomenon occurs in the declining phase.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654481-magnetic-nulls-super-radial-expansion-solar-corona','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654481-magnetic-nulls-super-radial-expansion-solar-corona">Magnetic Nulls and Super-radial Expansion in the Solar Corona</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Gibson, Sarah E.; Dalmasse, Kevin; Tomczyk, Steven Magnetic fields in the Sun’s outer atmosphere—the corona—control both solar-wind acceleration and the dynamics of solar eruptions. We present the first clear observational evidence of coronal magnetic nulls in off-limb linearly polarized observations of pseudostreamers, taken by the Coronal Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where magnetic reconnection is likely to act as a catalyst for solar activity. CoMP linear-polarization observations also provide an independent, coronal proxy for magnetic expansion into the solar wind, a quantity often used to parameterize and predict the solar wind speed at Earth. We introduce a new method for explicitly calculating expansion factorsmore » from CoMP coronal linear-polarization observations, which does not require photospheric extrapolations. We conclude that linearly polarized light is a powerful new diagnostic of critical coronal magnetic topologies and the expanding magnetic flux tubes that channel the solar wind.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPlPh..82d9201V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPlPh..82d9201V">Storing free magnetic energy in the solar corona</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vekstein, G. 2016-08-01 This article presents a mini-tutorial aimed at a wide readership not familiar with the field of solar plasma physics. The exposition is centred around the issue of excess/free magnetic energy stored in the solar corona. A general consideration is followed with a particular example of coronal magnetic arcade, where free magnetic energy builds up by photospheric convective flows. In the context of solar physics the major task is to explain how this free energy can be released quickly enough to match what is observed in coronal explosive events such as solar flares. Therefore, in the last section of the paper we discuss briefly a possible role of magnetic reconnection in these processes. This is done in quite simple qualitative physical terms, so that an interested reader can follow it up in more detail with help of the provided references. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AnGeo..32..383L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AnGeo..32..383L">Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr - Part 4: Near-Earth solar wind speed, IMF, and open solar flux</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lockwood, M.; Nevanlinna, H.; Barnard, L.; Owens, M. J.; Harrison, R. G.; Rouillard, A. P.; Scott, C. J. 2014-04-01 In the concluding paper of this tetralogy, we here use the different geomagnetic activity indices to reconstruct the near-Earth interplanetary magnetic field (IMF) and solar wind flow speed, as well as the open solar flux (OSF) from 1845 to the present day. The differences in how the various indices vary with near-Earth interplanetary parameters, which are here exploited to separate the effects of the IMF and solar wind speed, are shown to be statistically significant at the 93% level or above. Reconstructions are made using four combinations of different indices, compiled using different data and different algorithms, and the results are almost identical for all parameters. The correction to the aa index required is discussed by comparison with the Ap index from a more extensive network of mid-latitude stations. Data from the Helsinki magnetometer station is used to extend the aa index back to 1845 and the results confirmed by comparison with the nearby St Petersburg observatory. The optimum variations, using all available long-term geomagnetic indices, of the near-Earth IMF and solar wind speed, and of the open solar flux, are presented; all with ±2σ uncertainties computed using the Monte Carlo technique outlined in the earlier papers. The open solar flux variation derived is shown to be very similar indeed to that obtained using the method of Lockwood et al. (1999). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001ASSL..259..183D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001ASSL..259..183D">Solar Polarimetry and Magnetic Field Measurements</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> del Toro Iniesta, J. C. 2001-05-01 The magnetic nature of most solar (spatially resolved or unresolved) structures is amply recognized. Magnetic fields of the Sun play a paramount rôle in the overall thermodynamic and dynamic state of our star. The main observable manifestation of solar magnetic fields is the polarization of light either through the Zeeman effect on spectral lines or through the Hanle effect (depolarization by very weak magnetic fields of light previously polarized by scattering). Hence, one can easily understand the increasing importance that polarimetry is experimenting continuously in solar physics. Under the title of this contribution a six-hour course was given during the summer school. Clearly, the limited extension allocated for the notes in these proceedings avoids an extensive account of the several topics discussed: 1) a description of light as an electromagnetic wave and the polarization properties of monochromatic, time-harmonic, plane waves; 2) the polarization properties of polychromatic light and, in particular, of quasi-monochromatic light; 3) the transformations of (partially) polarized light by linear optical systems and a description of the ways we measure the Stokes parameters by spatially and/or temporally modulating the polarimetric signal; 4) a discussion on specific problems relevant to solar polarimetry like seeing-induced and instrumental polarization, or modulation and demodulation, along with a brief description of current solar polarimeters; 5) the vector radiative transfer equation for polarized light and its links to the scalar one for unpolarized light, together with a summary of the Zeeman effect and its consequences on line formation in a magnetized stellar atmosphere; 7) an introduction of the paramount astrophysical problem, i.e., that of finding diagnostics that enable the solar physicist to interpret the observables in terms of the solar atmospheric quantities, including a discussion on contribution and response functions; and 8) a brief </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667439-possible-impact-l5-magnetograms-non-potential-solar-coronal-magnetic-field-simulations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667439-possible-impact-l5-magnetograms-non-potential-solar-coronal-magnetic-field-simulations">THE POSSIBLE IMPACT OF L5 MAGNETOGRAMS ON NON-POTENTIAL SOLAR CORONAL MAGNETIC FIELD SIMULATIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Weinzierl, Marion; Yeates, Anthony R.; Mackay, Duncan H. The proposed Carrington-L5 mission would bring instruments to the L5 Lagrange point to provide us with crucial data for space weather prediction. To assess the importance of including a magnetograph, we consider the possible differences in non-potential solar coronal magnetic field simulations when magnetograph observations are available from the L5 point, compared with an L1-based field of view (FOV). A timeseries of synoptic radial magnetic field maps is constructed to capture the emergence of two active regions from the L5 FOV. These regions are initially absent in the L1 magnetic field maps, but are included once they rotate into themore » L1 FOV. Non-potential simulations for these two sets of input data are compared in detail. Within the bipolar active regions themselves, differences in the magnetic field structure can exist between the two simulations once the active regions are included in both. These differences tend to reduce within 5 days of the active region being included in L1. The delayed emergence in L1 can, however, lead to significant persistent differences in long-range connectivity between the active regions and the surrounding fields, and also in the global magnetic energy. In particular, the open magnetic flux and the location of open magnetic footpoints, are sensitive to capturing the real-time of emergence. These results suggest that a magnetograph at L5 could significantly improve predictions of the non-potential corona, the interplanetary magnetic field, and of solar wind source regions on the Sun.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.nrel.gov/news/press/1998/39tour.html','SCIGOVWS'); return false;" href="https://www.nrel.gov/news/press/1998/39tour.html">Tour Opens Doors, Minds to Solar Energy</a> <a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a> ., Oct. 5, 1998 Â The third annual Tour of Solar Homes will open the doors to hundreds of passive and Conifer, will be open 10 a.m. to 4 p.m. NREL's Visitors Center will open at 9 a.m. The Boulder tour, which </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050223614','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050223614">[A Predictive Model for the Magnetic Field in the Heliosphere and Acceleration of Suprathermal Particles in the Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Fisk, L. A. 2005-01-01 The purpose of this grant was to develop a theoretical understanding of the processes by which open magnetic flux undergoes large-scale transport in the solar corona, and to use this understanding to develop a predictive model for the heliospheric magnetic field, the configuration for which is determined by such motions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26PSL.492..222O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26PSL.492..222O">Were chondrites magnetized by the early solar wind?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Oran, Rona; Weiss, Benjamin P.; Cohen, Ofer 2018-06-01 Chondritic meteorites have been traditionally thought to be samples of undifferentiated bodies that never experienced large-scale melting. This view has been challenged by the existence of post-accretional, unidirectional natural remanent magnetization (NRM) in CV carbonaceous chondrites. The relatively young inferred NRM age [∼10 million years (My) after solar system formation] and long duration of NRM acquisition (1-106 y) have been interpreted as evidence that the magnetizing field was that of a core dynamo within the CV parent body. This would imply that CV chondrites represent the primitive crust of a partially differentiated body. However, an alternative hypothesis is that the NRM was imparted by the early solar wind. Here we demonstrate that the solar wind scenario is unlikely due to three main factors: 1) the magnitude of the early solar wind magnetic field is estimated to be <0.1 μT in the terrestrial planet-forming region, 2) the resistivity of chondritic bodies limits field amplification due to pile-up of the solar wind to less than a factor of 3.5 times that of the instantaneous solar wind field, and 3) the solar wind field likely changed over timescales orders of magnitude shorter than the timescale of NRM acquisition. Using analytical arguments, numerical simulations and astronomical observations of the present-day solar wind and magnetic fields of young stars, we show that the maximum mean field the ancient solar wind could have imparted on an undifferentiated CV parent body is <3.5 nT, which is 3-4 and 3 orders of magnitude weaker than the paleointensities recorded by the CV chondrites Allende and Kaba, respectively. Therefore, the solar wind is highly unlikely to be the source of the NRM in CV chondrites. Nevertheless, future high sensitivity paleomagnetic studies of rapidly-cooled meteorites with high magnetic recording fidelity could potentially trace the evolution of the solar wind field in time. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4810402L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4810402L">Magnetic Reconnection in the Solar Chromosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lukin, Vyacheslav S.; Ni, Lei; Murphy, Nicholas Arnold 2017-08-01 We report on the most recent efforts to accurately and self-consistently model magnetic reconnection processes in the context of the solar chromosphere. The solar chromosphere is a notoriously complex and highly dynamic boundary layer of the solar atmosphere where local variations in the plasma parameters can be of the order of the mean values. At the same time, the interdependence of the physical processes such as magnetic field evolution, local and global energy transfer between internal and electromagnetic plasma energy, radiation transport, plasma reactivity, and dissipation mechanisms make it a particularly difficult system to self-consistently model and understand. Several recent studies have focused on the micro-physics of multi-fluid magnetic reconnection at magnetic nulls in the weakly ionized plasma environment of the lower chromosphere[1-3]. Here, we extend the previous work by considering a range of spatial scales and magnetic field strengths in a configuration with component magnetic reconnection, i.e., for magnetic reconnection with a guide field. We show that in all cases the non-equilibrium reactivity of the plasma and the dynamic interaction among the plasma processes play important roles in determining the structure of the reconnection region. We also speculate as to the possible observables of chromospheric magnetic reconnection and the likely plasma conditions required for generation of Ellerman and IRIS bombs.[1] Leake, Lukin, Linton, and Meier, “Multi-fluid simulations of chromospheric magnetic reconnection in a weakly ionized reacting plasma,” ApJ 760 (2012).[2] Leake, Lukin, and Linton, “Magnetic reconnection in a weakly ionized plasma,” PoP 20 (2013).[3] Murphy and Lukin, “Asymmetric magnetic reconnection in weakly ionized chromospheric plasmas,” ApJ 805 (2015).[*Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017080','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017080">Multiscale Dynamics of Solar Magnetic Structures</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Uritsky, Vadim M.; Davila, Joseph M. 2012-01-01 Multiscale topological complexity of the solar magnetic field is among the primary factors controlling energy release in the corona, including associated processes in the photospheric and chromospheric boundaries.We present a new approach for analyzing multiscale behavior of the photospheric magnetic flux underlying these dynamics as depicted by a sequence of high-resolution solar magnetograms. The approach involves two basic processing steps: (1) identification of timing and location of magnetic flux origin and demise events (as defined by DeForest et al.) by tracking spatiotemporal evolution of unipolar and bipolar photospheric regions, and (2) analysis of collective behavior of the detected magnetic events using a generalized version of the Grassberger-Procaccia correlation integral algorithm. The scale-free nature of the developed algorithms makes it possible to characterize the dynamics of the photospheric network across a wide range of distances and relaxation times. Three types of photospheric conditions are considered to test the method: a quiet photosphere, a solar active region (NOAA 10365) in a quiescent non-flaring state, and the same active region during a period of M-class flares. The results obtained show (1) the presence of a topologically complex asymmetrically fragmented magnetic network in the quiet photosphere driven by meso- and supergranulation, (2) the formation of non-potential magnetic structures with complex polarity separation lines inside the active region, and (3) statistical signatures of canceling bipolar magnetic structures coinciding with flaring activity in the active region. Each of these effects can represent an unstable magnetic configuration acting as an energy source for coronal dissipation and heating. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AAS...22440205W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AAS...22440205W">Solar Wind Acceleration: Modeling Effects of Turbulent Heating in Open Flux Tubes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Woolsey, Lauren N.; Cranmer, Steven R. 2014-06-01 We present two self-consistent coronal heating models that determine the properties of the solar wind generated and accelerated in magnetic field geometries that are open to the heliosphere. These models require only the radial magnetic field profile as input. The first code, ZEPHYR (Cranmer et al. 2007) is a 1D MHD code that includes the effects of turbulent heating created by counter-propagating Alfven waves rather than relying on empirical heating functions. We present the analysis of a large grid of modeled flux tubes (> 400) and the resulting solar wind properties. From the models and results, we recreate the observed anti-correlation between wind speed at 1 AU and the so-called expansion factor, a parameterization of the magnetic field profile. We also find that our models follow the same observationally-derived relation between temperature at 1 AU and wind speed at 1 AU. We continue our analysis with a newly-developed code written in Python called TEMPEST (The Efficient Modified-Parker-Equation-Solving Tool) that runs an order of magnitude faster than ZEPHYR due to a set of simplifying relations between the input magnetic field profile and the temperature and wave reflection coefficient profiles. We present these simplifying relations as a useful result in themselves as well as the anti-correlation between wind speed and expansion factor also found with TEMPEST. Due to the nature of the algorithm TEMPEST utilizes to find solar wind solutions, we can effectively separate the two primary ways in which Alfven waves contribute to solar wind acceleration: 1) heating the surrounding gas through a turbulent cascade and 2) providing a separate source of wave pressure. We intend to make TEMPEST easily available to the public and suggest that TEMPEST can be used as a valuable tool in the forecasting of space weather, either as a stand-alone code or within an existing modeling framework. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28949585','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28949585">Solar Irradiance Variability is Caused by the Magnetic Activity on the Solar Surface.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yeo, Kok Leng; Solanki, Sami K; Norris, Charlotte M; Beeck, Benjamin; Unruh, Yvonne C; Krivova, Natalie A 2017-09-01 The variation in the radiative output of the Sun, described in terms of solar irradiance, is important to climatology. A common assumption is that solar irradiance variability is driven by its surface magnetism. Verifying this assumption has, however, been hampered by the fact that models of solar irradiance variability based on solar surface magnetism have to be calibrated to observed variability. Making use of realistic three-dimensional magnetohydrodynamic simulations of the solar atmosphere and state-of-the-art solar magnetograms from the Solar Dynamics Observatory, we present a model of total solar irradiance (TSI) that does not require any such calibration. In doing so, the modeled irradiance variability is entirely independent of the observational record. (The absolute level is calibrated to the TSI record from the Total Irradiance Monitor.) The model replicates 95% of the observed variability between April 2010 and July 2016, leaving little scope for alternative drivers of solar irradiance variability at least over the time scales examined (days to years). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ScChE..60.1408G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ScChE..60.1408G">Origin and structures of solar eruptions II: Magnetic modeling</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Guo, Yang; Cheng, Xin; Ding, MingDe 2017-07-01 The topology and dynamics of the three-dimensional magnetic field in the solar atmosphere govern various solar eruptive phenomena and activities, such as flares, coronal mass ejections, and filaments/prominences. We have to observe and model the vector magnetic field to understand the structures and physical mechanisms of these solar activities. Vector magnetic fields on the photosphere are routinely observed via the polarized light, and inferred with the inversion of Stokes profiles. To analyze these vector magnetic fields, we need first to remove the 180° ambiguity of the transverse components and correct the projection effect. Then, the vector magnetic field can be served as the boundary conditions for a force-free field modeling after a proper preprocessing. The photospheric velocity field can also be derived from a time sequence of vector magnetic fields. Three-dimensional magnetic field could be derived and studied with theoretical force-free field models, numerical nonlinear force-free field models, magnetohydrostatic models, and magnetohydrodynamic models. Magnetic energy can be computed with three-dimensional magnetic field models or a time series of vector magnetic field. The magnetic topology is analyzed by pinpointing the positions of magnetic null points, bald patches, and quasi-separatrix layers. As a well conserved physical quantity, magnetic helicity can be computed with various methods, such as the finite volume method, discrete flux tube method, and helicity flux integration method. This quantity serves as a promising parameter characterizing the activity level of solar active regions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......241L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......241L">Deep Convection, Magnetism and Solar Supergranulation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lord, J. W. We examine the effect of deep convection and magnetic fields on solar supergranulation. While supergranulation was originally identified as a convective flow from relatively great depth below the solar surface, recent work suggests that supergranules may originate near the surface. We use the MURaM code to simulate solar-like surface convection with a realistic photosphere and domain size up to 197 x 197 x 49 Mm3. This yields nearly five orders of magnitude of density contrast between the bottom of the domain and the photosphere which is the most stratified solar-like convection simulations that we are aware of. Magnetic fields were thought to be a passive tracer in the photosphere, but recent work suggests that magnetism could provide a mechanism that enhances the supergranular scale flows at the surface. In particular, the enhanced radiative losses through long lived magnetic network elements may increase the lifetime of photospheric downflows and help organize low wavenumber flows. Since our simulation does not have sufficient resolution to resolve increased cooling by magnetic bright points, we artificially increase the radiative cooling in elements with strong magnetic flux. These simulations increase the cooling by 10% for magnetic field strength greater than 100 G. We find no statistically significant difference in the velocity or magnetic field spectrum by enhancing the radiative cooling. We also find no differences in the time scale of the flows or the length scales of the magnetic energy spectrum. This suggests that the magnetic field is determined by the flows and is largely a passive tracer. We use these simulations to construct a two-component model of the flows: for scales smaller than the driving (integral) scale (which is four times the local density scale height) the flows follow a Kolmogorov (k-5/3) spectrum, while larger scale modes decay with height from their driving depth (i.e. the depth where the wavelength of the mode is equal to the driving </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19960021313&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DOpen%2BField','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19960021313&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DOpen%2BField">Open and disconnected magnetic field lines within coronal mass ejections in the solar wind: Evidence for 3-dimensional reconnection</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gosling, J. T.; Birn, J.; McComas, D. J.; Phillips, J. L.; Hesse, M. 1995-01-01 Measurements of suprathermal electron fluxes in the solar wind at energies greater than approximatley 80 eV indicate that magnetic field lines within coronal mass ejections. CMEs, near and beyond 1 AU are normally connected to the Sun at both ends. However, a preliminary reexamination of events previously identified as CMEs in the ISEE 3 data reveals that about 1/4 of all such events contain limited regions where field lines appear to be either connected to the Sun at only one end or connected to the outer heliosphere at both ends. Similar intervals of open and disconnected field lines within CMEs have been identified in the Ulysses observations. We believe that these anomalous field topologies within CMEs are most naturally interpreted in terms of 3-dimensional reconnection behind CMEs close to the Sun. Such reconnection also provides a natural explanation both for the flux rope topology of many CMEs as well as the coronal loops formed during long-duration solar soft X ray events. Although detailed numerical simulations of 3-dimensional reconnection behind CMEs are not yet available, such simulations have been done for the qualitatively similar geometry that prevails within the geomagnetic tail. Those simulations of plasmoid formation in the geomagnetic tail do produce the mixture of field topologies within plasmoids discussed here for CMEs. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720044025&hterms=Parkin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DParkin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720044025&hterms=Parkin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DParkin">Measurements of lunar magnetic field interaction with the solar wind.</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Dyal, P.; Parkin, C. W.; Snyder, C. W.; Clay, D. R. 1972-01-01 Study of the compression of the remanent lunar magnetic field by the solar wind, based on measurements of remanent magnetic fields at four Apollo landing sites and of the solar wind at two of these sites. Available data show that the remanent magnetic field at the lunar surface is compressed as much as 40% above its initial value by the solar wind, but the total remanent magnetic pressure is less than the stagnation pressure by a factor of six, implying that a local shock is not formed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040161431&hterms=magnetic+vector+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmagnetic%2Bvector%2Bpotential','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040161431&hterms=magnetic+vector+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dmagnetic%2Bvector%2Bpotential">Large Solar Flares and Sheared Magnetic Field Configuration</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Choudhary, Debi Prasad 2001-01-01 This Comment gives additional information about the nature of flaring locations on the Sun described in the article "Sun unleashes Halloween storm", by R. E. Lopez, et al. What causes the large explosions from solar active regions that unleash huge magnetic storms and adverse space weather? It is now beyond doubt that the magnetic field in solar active regions harbors free energy that is released during these events. Direct measurements of the longitudinal and transverse components of active region magnetic fields with the vector magnetograph at NASA Marshall Space Flight Center (MSFC), taken on a regular basis for the last 30 years, have found key signatures of the locations of powerful flares. A vector magnetograph detects and measures the magnetic shear, which is the deviation of the observed transverse magnetic field direction from the potential field. The sheared locations possess abundant free magnetic energy for solar flares. In addition to active region NOAA 10486, the one that produced the largest flares last October, the NASA/MSFC vector magnetograph has observed several other such complex super active regions, including NOAA 6555 and 6659. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM34A..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM34A..01H">Kinetic Interactions Between the Solar Wind and Lunar Magnetic Fields</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Halekas, J. S.; Poppe, A. R.; Fatemi, S.; Turner, D. L.; Holmstrom, M. 2016-12-01 Despite their relatively weak strength, small scale, and incoherence, lunar magnetic anomalies can affect the incoming solar wind flow. The plasma interaction with lunar magnetic fields drives significant compressions of the solar wind plasma and magnetic field, deflections of the incoming flow, and a host of plasma waves ranging from the ULF to the electrostatic range. Recent work suggests that the large-scale features of the solar wind-magnetic anomaly interactions may be driven by ion-ion instabilities excited by reflected ions, raising the possibility that they are analogous to ion foreshock phenomena. Indeed, despite their small scale, many of the phenomena observed near lunar magnetic anomalies appear to have analogues in the foreshock regions of terrestrial planets. We discuss the charged particle distributions, fields, and waves observed near lunar magnetic anomalies, and place them in a context with the foreshocks of the Earth, Mars, and other solar system objects. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1512573T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1512573T">The COronal Solar Magnetism Observatory (COSMO) Large Aperture Coronagraph</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tomczyk, Steve; Gallagher, Dennis; Wu, Zhen; Zhang, Haiying; Nelson, Pete; Burkepile, Joan; Kolinksi, Don; Sutherland, Lee 2013-04-01 The COSMO is a facility dedicated to observing coronal and chromospheric magnetic fields. It will be located on a mountaintop in the Hawaiian Islands and will replace the current Mauna Loa Solar Observatory (MLSO). COSMO will provide unique observations of the global coronal magnetic fields and its environment to enhance the value of data collected by other observatories on the ground (e.g. SOLIS, BBO NST, Gregor, ATST, EST, Chinese Giant Solar Telescope, NLST, FASR) and in space (e.g. SDO, Hinode, SOHO, GOES, STEREO, Solar-C, Solar Probe+, Solar Orbiter). COSMO will employ a fleet of instruments to cover many aspects of measuring magnetic fields in the solar atmosphere. The dynamics and energy flow in the corona are dominated by magnetic fields. To understand the formation of CMEs, their relation to other forms of solar activity, and their progression out into the solar wind requires measurements of coronal magnetic fields. The large aperture coronagraph, the Chromospheric and Prominence Magnetometer and the K-Coronagraph form the COSMO instrument suite to measure magnetic fields and the polarization brightness of the low corona used to infer electron density. The large aperture coronagraph will employ a 1.5 meter fuse silica singlet lens, birefringent filters, and a spectropolarimeter to cover fields of view of up to 1 degree. It will observe the corona over a wide range of emission lines from 530.3 nm through 1083.0 nm allowing for magnetic field measurements over a wide range of coronal temperatures (e.g. FeXIV at 530.3 nm, Fe X at 637.4 nm, Fe XIII at 1074.7 and 1079.8 nm. These lines are faint and require the very large aperture. NCAR and NSF have provided funding to bring the large aperture coronagraph to a preliminary design review state by the end of 2013. As with all data from Mauna Loa, the data products from COSMO will be available to the community via the Mauna Loa website: http://mlso.hao.ucar.edu </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22739314','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22739314">Magnetic tornadoes as energy channels into the solar corona.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wedemeyer-Böhm, Sven; Scullion, Eamon; Steiner, Oskar; van der Voort, Luc Rouppe; de la Cruz Rodriguez, Jaime; Fedun, Viktor; Erdélyi, Robert 2012-06-27 Heating the outer layers of the magnetically quiet solar atmosphere to more than one million kelvin and accelerating the solar wind requires an energy flux of approximately 100 to 300 watts per square metre, but how this energy is transferred and dissipated there is a puzzle and several alternative solutions have been proposed. Braiding and twisting of magnetic field structures, which is caused by the convective flows at the solar surface, was suggested as an efficient mechanism for atmospheric heating. Convectively driven vortex flows that harbour magnetic fields are observed to be abundant in the photosphere (the visible surface of the Sun). Recently, corresponding swirling motions have been discovered in the chromosphere, the atmospheric layer sandwiched between the photosphere and the corona. Here we report the imprints of these chromospheric swirls in the transition region and low corona, and identify them as observational signatures of rapidly rotating magnetic structures. These ubiquitous structures, which resemble super-tornadoes under solar conditions, reach from the convection zone into the upper solar atmosphere and provide an alternative mechanism for channelling energy from the lower into the upper solar atmosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1113158V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1113158V">Comparing the solar magnetic field in the corona and in the inner heliosphere during solar cycles 21-23</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Virtanen, I. I.; Mursula, K. 2009-04-01 We compare the open solar magnetic field estimated by the PFSS model based on the WSO photospheric field observations, with the inner heliospheric magnetic field. We trace the observed radial HMF into the coronal PFSS boundary at 2.5 solar radii using the observed solar wind velocity, and determine the PFSS model field at the line-of-sight footpoint. Comparing the two field values, we calculate the power n of the apparent decrease of the radial field. According to expectations based on Maxwell's equations, also reproduced by Parker's HMF model, the radial HMF field should decrease with n=2. However, comparison gives considerably lower values of n, indicating the effect of HCS in the PFSS model and the possible superexpansion. The n values vary with solar cycle, being roughly 1.3-1.4 at minima and about 1.7 at maxima. Interestingly, the n values for the two HMF sectors show systematic differences in the late declining to minimum phase, with smaller n values for the HMF sector dominant in the northern hemisphere. This is in agreement with the smaller field value in the northern hemisphere and the southward shifted HCS, summarized by the concept of the bashful ballerina. We also find that the values of n during the recent years, in the late declining phase of solar cycle 23, are significantly larger than during the same phase of the previous cycles. This agrees with the exceptionally large tilt of the solar dipole at the end of cycle 23. We also find that the bashful ballerina appears even during SC 23 but the related hemispheric differences are smaller than during the previous cycles. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22348445-influence-magnetic-field-running-penumbral-waves-solar-chromosphere','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22348445-influence-magnetic-field-running-penumbral-waves-solar-chromosphere">The influence of the magnetic field on running penumbral waves in the solar chromosphere</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Jess, D. B.; Reznikova, V. E.; Van Doorsselaere, T. 2013-12-20 We use images of high spatial and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the role magnetic field inclination angles play in the propagation characteristics of running penumbral waves in the solar chromosphere. Analysis of a near-circular sunspot, close to the center of the solar disk, reveals a smooth rise in oscillatory period as a function of distance from the umbral barycenter. However, in one directional quadrant, corresponding to the north direction, a pronounced kink in the period-distance diagram is found. Utilizing a combination of the inversion of magnetic Stokes vectors and force-free field extrapolations, wemore » attribute this behavior to the cut-off frequency imposed by the magnetic field geometry in this location. A rapid, localized inclination of the magnetic field lines in the north direction results in a faster increase in the dominant periodicity due to an accelerated reduction in the cut-off frequency. For the first time, we reveal how the spatial distribution of dominant wave periods, obtained with one of the highest resolution solar instruments currently available, directly reflects the magnetic geometry of the underlying sunspot, thus opening up a wealth of possibilities in future magnetohydrodynamic seismology studies. In addition, the intrinsic relationships we find between the underlying magnetic field geometries connecting the photosphere to the chromosphere, and the characteristics of running penumbral waves observed in the upper chromosphere, directly supports the interpretation that running penumbral wave phenomena are the chromospheric signature of upwardly propagating magneto-acoustic waves generated in the photosphere.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110007245&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110007245&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly">Solar Sources and Geospace Consequences of Interplanetary Magnetic Clouds Observed During Solar Cycle 23</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gopalswamy, N.; Akiyama, S.; Yashiro, S.; Michalek, G.; Lepping, R. P. 2007-01-01 We present results of a statistical investigation of 99 magnetic clouds (MCs) observed during 1995-2005. The MC-associated coronal mass ejections (CMEs) are faster and wider on the average and originate within +/-30deg from the solar disk center. The solar sources of MCs also followed the butterfly diagram. The correlation between the magnetic field strength and speed of MCs was found to be valid over a much wider range of speeds. The number of south-north (SN) MCs was dominant and decreased with solar cycle, while the number of north-south (NS) MCs increased confirming the odd-cycle behavior. Two-thirds of MCs were geoeffective; the Dst index was highly correlated with speed and magnetic field in MCs as well as their product. Many (55%) fully northward (FN) MCs were geoeffective solely due to their sheaths. The non-geoeffective MCs were slower (average speed approx. 382 km/s), had a weaker southward magnetic field (average approx. -5.2nT), and occurred mostly during the rise phase of the solar activity cycle. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AIPC..679..409Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AIPC..679..409Z">Magnetic Turbulence, Fast Magnetic Field line Diffusion and Small Magnetic Structures in the Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zimbardo, G.; Pommois, P.; Veltri, P. 2003-09-01 The influence of magnetic turbulence on magnetic field line diffusion has been known since the early days of space and plasma physics. However, the importance of ``stochastic diffusion'' for energetic particles has been challenged on the basis of the fact that sharp gradients of either energetic particles or ion composition are often observed in the solar wind. Here we show that fast transverse field line and particle diffusion can coexist with small magnetic structures, sharp gradients, and with long lived magnetic flux tubes. We show, by means of a numerical realization of three dimensional magnetic turbulence and by use of the concepts of deterministic chaos and turbulent transport, that turbulent diffusion is different from Gaussian diffusion, and that transport can be inhomogeneous even if turbulence homogeneously fills the heliosphere. Several diagnostics of field line transport and flux tube evolution are shown, and the size of small magnetic structures in the solar wind, like gradient scales and flux tube thickness, are estimated and compared to the observations. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730002043','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730002043">The interplanetary and solar magnetic field sector structures, 1962 - 1968</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Jones, D. E. 1972-01-01 The interplanetary magnetic field sector structure was observed from late 1962 through 1968. During this time it has been possible to study the manner in which the sector pattern and its relation to the photospheric magnetic field configuration changes from solar minimum to solar maximum. Observations were also made relating sector boundaries to specific regions on the solar disk. These and other observations related to the solar origin of the interplanetary field are briefly reviewed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPP.M9004E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPP.M9004E">Magnetic pumping of the solar wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Egedal, Jan; Lichko, Emily; Daughton, William 2015-11-01 The transport of matter and radiation in the solar wind and terrestrial magnetosphere is a complicated problem involving competing processes of charged particles interacting with electric and magnetic fields. Given the rapid expansion of the solar wind, it would be expected that superthermal electrons originating in the corona would cool rapidly as a function of distance to the Sun. However, this is not observed, and various models have been proposed as candidates for heating the solar wind. In the compressional pumping mechanism explored by Fisk and Gloeckler particles are accelerated by random compressions by the interplanetary wave turbulence. This theory explores diffusion due to spatial non-uniformities and provides a mechanism for redistributing particle. For investigation of a related but different heating mechanism, magnetic pumping, in our work we include diffusion of anisotropic features that develops in velocity space. The mechanism allows energy to be transferred to the particles directly from the turbulence. Guided by kinetic simulations a theory is derived for magnetic pumping. At the heart of this work is a generalization of the Parker Equation to capture the role of the pressure anisotropy during the pumping process. Supported by NASA grant NNX15AJ73G. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH31C2746P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH31C2746P">Non-Extensive Statistical Analysis of Solar Wind Electric, Magnetic Fields and Solar Energetic Particle time series.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pavlos, G. P.; Malandraki, O.; Khabarova, O.; Livadiotis, G.; Pavlos, E.; Karakatsanis, L. P.; Iliopoulos, A. C.; Parisis, K. 2017-12-01 In this work we study the non-extensivity of Solar Wind space plasma by using electric-magnetic field data obtained by in situ spacecraft observations at different dynamical states of solar wind system especially in interplanetary coronal mass ejections (ICMEs), Interplanetary shocks, magnetic islands, or near the Earth Bow shock. Especially, we study the energetic particle non extensive fractional acceleration mechanism producing kappa distributions as well as the intermittent turbulence mechanism producing multifractal structures related with the Tsallis q-entropy principle. We present some new and significant results concerning the dynamics of ICMEs observed in the near Earth at L1 solar wind environment, as well as its effect in Earth's magnetosphere as well as magnetic islands. In-situ measurements of energetic particles at L1 are analyzed, in response to major solar eruptive events at the Sun (intense flares, fast CMEs). The statistical characteristics are obtained and compared for the Solar Energetic Particles (SEPs) originating at the Sun, the energetic particle enhancements associated with local acceleration during the CME-driven shock passage over the spacecraft (Energetic Particle Enhancements, ESPs) as well as the energetic particle signatures observed during the passage of the ICME. The results are referred to Tsallis non-extensive statistics and in particular to the estimation of Tsallis q-triplet, (qstat, qsen, qrel) of electric-magnetic field and the kappa distributions of solar energetic particles time series of the ICME, magnetic islands, resulting from the solar eruptive activity or the internal Solar Wind dynamics. Our results reveal significant differences in statistical and dynamical features, indicating important variations of the magnetic field dynamics both in time and space domains during the shock event, in terms of rate of entropy production, relaxation dynamics and non-equilibrium meta-stable stationary states. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110015361&hterms=dependence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddependence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110015361&hterms=dependence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddependence">Scale Dependence of Magnetic Helicity in the Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Brandenburg, Axel; Subramanian, Kandaswamy; Balogh, Andre; Goldstein, Melvyn L. 2011-01-01 We determine the magnetic helicity, along with the magnetic energy, at high latitudes using data from the Ulysses mission. The data set spans the time period from 1993 to 1996. The basic assumption of the analysis is that the solar wind is homogeneous. Because the solar wind speed is high, we follow the approach first pioneered by Matthaeus et al. by which, under the assumption of spatial homogeneity, one can use Fourier transforms of the magnetic field time series to construct one-dimensional spectra of the magnetic energy and magnetic helicity under the assumption that the Taylor frozen-in-flow hypothesis is valid. That is a well-satisfied assumption for the data used in this study. The magnetic helicity derives from the skew-symmetric terms of the three-dimensional magnetic correlation tensor, while the symmetric terms of the tensor are used to determine the magnetic energy spectrum. Our results show a sign change of magnetic helicity at wavenumber k approximately equal to 2AU(sup -1) (or frequency nu approximately equal to 2 microHz) at distances below 2.8AU and at k approximately equal to 30AU(sup -1) (or nu approximately equal to 25 microHz) at larger distances. At small scales the magnetic helicity is positive at northern heliographic latitudes and negative at southern latitudes. The positive magnetic helicity at small scales is argued to be the result of turbulent diffusion reversing the sign relative to what is seen at small scales at the solar surface. Furthermore, the magnetic helicity declines toward solar minimum in 1996. The magnetic helicity flux integrated separately over one hemisphere amounts to about 10(sup 45) Mx(sup 2) cycle(sup -1) at large scales and to a three times lower value at smaller scales. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130012782','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130012782">Construction of Solar-Wind-Like Magnetic Fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Roberts, Dana Aaron 2012-01-01 Fluctuations in the solar wind fields tend to not only have velocities and magnetic fields correlated in the sense consistent with Alfven waves traveling from the Sun, but they also have the magnitude of the magnetic field remarkably constant despite their being broadband. This paper provides, for the first time, a method for constructing fields with nearly constant magnetic field, zero divergence, and with any specified power spectrum for the fluctuations of the components of the field. Every wave vector, k, is associated with two polarizations the relative phases of these can be chosen to minimize the variance of the field magnitude while retaining the\\random character of the fields. The method is applied to a case with one spatial coordinate that demonstrates good agreement with observed time series and power spectra of the magnetic field in the solar wind, as well as with the distribution of the angles of rapid changes (discontinuities), thus showing a deep connection between two seemingly unrelated issues. It is suggested that using this construction will lead to more realistic simulations of solar wind turbulence and of the propagation of energetic particles. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940020793','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940020793">Solar magnetic cycle</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Harvey, Karen L. 1993-01-01 Using NSO/KP magnetograms, the pattern and rate of the emergence of magnetic flux and the development of the large-scale patterns of unipolar fields are considered in terms of the solar magnetic cycle. Magnetic flux emerges in active regions at an average rate of 2 x 10(exp 21) Mx/day, approximately 10 times the estimated rate in ephemeral regions. Observations are presented that demonstrate that the large-scale unipolar fields originate in active regions and activity nests. For cycle 21, the net contribution of ephemeral regions to the axial dipole moment of the Sun is positive, and is of opposite sign to that of active regions. Its amplitude is smaller by a factor of 6, assuming an average lifetime of ephemeral regions of 8 hours. Active regions larger than 4500 Mm(sup 2) are the primary contributor to the cycle variation of Sun's axial dipole moment. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760017048','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760017048">Magnetic holes in the solar wind. [(interplanetary magnetic fields)</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Turner, J. M.; Burlaga, L. F.; Ness, N. F.; Lemaire, J. F. 1976-01-01 An analysis is presented of high resolution interplanetary magnetic field measurements from the magnetometer on Explorer 43 which showed that low magnetic field intensities in the solar wind at 1 AU occur as distinct depressions or 'holes'. These magnetic holes are new kinetic-scale phenomena, having a characteristic dimension on the order of 20,000 km. They occurred at a rate of 1.5/day in the 18-day time span (March 18 to April 6, 1971) that was analyzed. Most of the magnetic holes are characterized by both a depression in the absolute value of the magnetic field, and a change in the magnetic field direction; some of these are possibly the result of magnetic merging. However, in other cases the magnetic field direction does not change; such holes are not due to magnetic merging, but might be a diamagnetic effect due to localized plasma inhomogeneities. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730002053','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730002053">Conversion of magnetic field energy into kinetic energy in the solar wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Whang, Y. C. 1972-01-01 The outflow of the solar magnetic field energy (the radial component of the Poynting vector) per steradian is inversely proportional to the solar wind velocity. It is a decreasing function of the heliocentric distance. When the magnetic field effect is included in the one-fluid model of the solar wind, the transformation of magnetic field energy into kinetic energy during the expansion process increases the solar wind velocity at 1 AU by 17 percent. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910042508&hterms=Magnetic+Flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMagnetic%2BFlux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910042508&hterms=Magnetic+Flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMagnetic%2BFlux">Magnetic flux transport of decaying active regions and enhanced magnetic network. [of solar supergranulation</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wang, Haimin; Zirin, Harold; Ai, Guoxiang 1991-01-01 Several series of coordinated observations on decaying active regions and enhanced magnetic network regions on the sun were carried out jointly at Big Bear Solar Observatory and at the Huairou Solar Observing Station of the Bejing Astronomical Observatory in China. The magnetic field evolution in several regions was followed closely for three to seven days. The magnetic flux transport from the remnants of decayed active regions was studied, along with the evolution and lifetime of the magnetic network which defines the boundaries of supergranules. The magnetic flux transport in an enhanced network region was studied in detail and found to be negative. Also briefly described are some properties of moving magnetic features around a sunspot. Results of all of the above studies are presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860045902&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DOpen%2BField','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860045902&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DOpen%2BField">Steady hydromagnetic flows in open magnetic fields. I - A class of analytic solutions. [for stellar winds</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Low, B. C.; Tsinganos, K. 1986-01-01 In the case of an establishment of theoretical models of the hydromagnetic solar wind, the inclusion of the effects of the magnetic field in the solar wind makes it extremely dificult to solve the mathematical problem. This paper has the objective to present a set of particular analytic solutions. The general formulation of Tsinganos (1982) is used to identify a class of analytic solutions to the equations of steady hydromagnetic flows in spherical coordinates. Flow in an open magnetic field are studied, taking into account the problem in dimensionless form, the special case of radial flows with alpha = 0, general radial flows, illustrative examples for flows in which alpha is not equal to 0, a parametric study of nonradial flows in which alpha is not equal to zero, variations in the parameter nu, and variations in the initial speed eta. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM31C..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM31C..07K">Coupling between non-thermal plasmas and magnetic fields in space: in situ and remote observations with Parker Solar Probe and SunRISE</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kasper, J. C. 2017-12-01 This talk will review examples of open questions in the coupling between non-thermal plasmas and magnetic fields in space, including pressure anisotropies, in heating, and particle acceleration, in the context of space missions either preparing for launch or under study and using in situ observations or remote sensing techniques. The Parker Solar Probe, with launch in the summer of next year, will collect the first in situ samples of plasma in the outer corona, allowing us to directly observe the physical processes responsible for the heating and acceleration of the solar corona and solar wind. The Sun Radio Interferometer Space Experiment (SunRISE) mission is a low frequency radio array under study by NASA which would image for the first time locations of particle acceleration relative to coronal mass ejections and trace magnetic field lines that connect active regions to the heliosphere. Major open questions under investigation by these techniques will be explored, with an eye to connections to laboratory experiments. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..217a2001L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..217a2001L">The effects of opening areas on solar chimney performance</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ling, L. S.; Rahman, M. M.; Chu, C. M.; Misaran, M. S. bin; Tamiri, F. M. 2017-07-01 To enhance natural ventilation at day time, solar chimney is one of the suitable options for topical country like Malaysia. Solar chimney creates air flow due to stack effect caused by temperature difference between ambient and inside wall. In the solar chimney, solar energy is harvested by the inner wall that cause temperature rise compare to ambient. Therefore, the efficiency of the solar chimney depends on the availability of solar energy as well as the solar intensity. In addition, it is very hard to get good ventilation at night time by using a solar chimney. To overcome this problem one of the suitable valid option is to integrate solar chimney with turbine ventilator. A new type of solar chimney is designed and fluid flow analyzed with the computational fluid dynamics (CFD) software. The aim of CFD and theoretical study are to investigate the effect of opening areas on modified solar chimney performance. The inlet and outlet area of solar chimney are varied from 0.0224m2 to 0.6m2 and 0.1m2 to 0.14m2 respectively based on the changes of inclination angle and gap between inner and outer wall. In the CFD study the constant heat flux is considered as 500W/m2. CFD result shows that there is no significant relation between opening areas and the air flow rate through solar chimney but the ratio between inlet and outlet is significant on flow performance. If the area ratio between inlet and outlet are equal to two or larger, the performance of the solar chimney is better than the solar chimney with ratio lesser than two. The solar chimney performance does not effect if the area ratio between inlet and outlet varies from 1 to 2. This result will be useful for design and verification of actual solar chimney performance. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017nova.pres.2278K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017nova.pres.2278K">Escape for the Slow Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kohler, Susanna 2017-05-01 Plasma from the Sun known as the slow solar wind has been observed far away from where scientists thought it was produced. Now new simulations may have resolved the puzzle of where the slow solar wind comes from and how it escapes the Sun to travel through our solar system.An Origin PuzzleA full view of a coronal hole (dark portion) from SDO. The edges of the coronal hole mark the boundary between open and closed magnetic field lines. [SDO; adapted from Higginson et al. 2017]The Suns atmosphere, known as the corona, is divided into two types of regions based on the behavior of magnetic field lines. In closed-field regions, the magnetic field is firmly anchored in the photosphere at both ends of field lines, so traveling plasma is confined to coronal loops and must return to the Suns surface. In open-field regions, only one end of each magnetic field line is anchored in the photosphere, so plasma is able to stream from the Suns surface out into the solar system.This second type of region known as a coronal hole is thought to be the origin of fast-moving plasma measured in our solar system and known as the fast solar wind. But we also observe a slow solar wind: plasma that moves at speeds of less than 500 km/s.The slow solar wind presents a conundrum. Its observational properties strongly suggest it originates in the hot, closed corona rather than the cooler, open regions. But if the slow solar wind plasma originates in closed-field regions of the Suns atmosphere, then how does it escape from the Sun?Slow Wind from Closed FieldsA team of scientists led by Aleida Higginson (University of Michigan) has now used high-resolution, three-dimensional magnetohydrodynamic simulations to show how the slow solar wind can be generated from plasma that starts outin closed-field parts of the Sun.A simulated heliospheric arc, composed of open magnetic field lines. [Higginson et al. 2017]Motions on the Suns surface near the boundary between open and closed-field regions the boundary </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH51C2497H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH51C2497H">Measuring the Large-scale Solar Magnetic Field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hoeksema, J. T.; Scherrer, P. H.; Peterson, E.; Svalgaard, L. 2017-12-01 The Sun's large-scale magnetic field is important for determining global structure of the corona and for quantifying the evolution of the polar field, which is sometimes used for predicting the strength of the next solar cycle. Having confidence in the determination of the large-scale magnetic field of the Sun is difficult because the field is often near the detection limit, various observing methods all measure something a little different, and various systematic effects can be very important. We compare resolved and unresolved observations of the large-scale magnetic field from the Wilcox Solar Observatory, Heliseismic and Magnetic Imager (HMI), Michelson Doppler Imager (MDI), and Solis. Cross comparison does not enable us to establish an absolute calibration, but it does allow us to discover and compensate for instrument problems, such as the sensitivity decrease seen in the WSO measurements in late 2016 and early 2017. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960012480','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960012480">Study of magnetic notions in the solar photosphere and their implications for heating the solar atmosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Noyes, Robert W. 1995-01-01 This progress report covers the first year of NASA Grant NAGw-2545, a study of magnetic structure in the solar photosphere and chromosphere. We have made significant progress in three areas: (1) analysis of vorticity in photospheric convection, which probably affects solar atmospheric heating through the stresses it imposes on photospheric magnetic fields; (2) modelling of the horizontal motions of magnetic footpoints in the solar photosphere using an assumed relation between brightness and vertical motion as well as continuity of flow; and (3) observations and analysis of infrared CO lines formed near the solar temperature minimum, whose structure and dynamics also yield important clues to the nature of heating of the upper atmosphere. Each of these areas are summarized in this report, with copies of those papers prepared or published this year included. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970026470','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970026470">On the Dynamics of Small-Scale Solar Magnetic Elements</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Berger, T. E.; Title, A. M. 1996-01-01 We report on the dynamics of the small-scale solar magnetic field, based on analysis of very high resolution images of the solar photosphere obtained at the Swedish Vacuum Solar Telescope. The data sets are movies from 1 to 4 hr in length, taken in several wavelength bands with a typical time between frames of 20 s. The primary method of tracking small-scale magnetic elements is with very high contrast images of photospheric bright points, taken through a 12 A bandpass filter centered at 4305 A in the Fraunhofer 'G band.' Previous studies have established that such bright points are unambiguously associated with sites of small-scale magnetic flux in the photosphere, although the details of the mechanism responsible for the brightening of the flux elements remain uncertain. The G band bright points move in the intergranular lanes at speeds from 0.5 to 5 km/s. The motions appear to be constrained to the intergranular lanes and are primarily driven by the evolution of the local granular convection flow field. Continual fragmentation and merging of flux is the fundamental evolutionary mode of small-scale magnetic structures in the solar photosphere. Rotation and folding of chains or groups of bright points are also observed. The timescale for magnetic flux evolution in active region plage is on the order of the correlation time of granulation (typically 6-8 minutes), but significant morphological changes can occur on timescales as short as 100 S. Smaller fragments are occasionally seen to fade beyond observable contrast. The concept of a stable, isolated subarcsecond magnetic 'flux tube' in the solar photosphere is inconsistent with the observations presented here. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/863467','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/863467">Methods for improving solar cell open circuit voltage</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Jordan, John F.; Singh, Vijay P. 1979-01-01 A method for producing a solar cell having an increased open circuit voltage. A layer of cadmium sulfide (CdS) produced by a chemical spray technique and having residual chlorides is exposed to a flow of hydrogen sulfide (H.sub.2 S) heated to a temperature of 400.degree.-600.degree. C. The residual chlorides are reduced and any remaining CdCl.sub.2 is converted to CdS. A heterojunction is formed over the CdS and electrodes are formed. Application of chromium as the positive electrode results in a further increase in the open circuit voltage available from the H.sub.2 S-treated solar cell. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730002044','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730002044">Large-scale solar magnetic fields and H-alpha patterns</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Mcintosh, P. S. 1972-01-01 Coronal and interplanetary magnetic fields computed from measurements of large-scale photospheric magnetic fields suffer from interruptions in day-to-day observations and the limitation of using only measurements made near the solar central meridian. Procedures were devised for inferring the lines of polarity reversal from H-alpha solar patrol photographs that map the same large-scale features found on Mt. Wilson magnetograms. These features may be monitored without interruption by combining observations from the global network of observatories associated with NOAA's Space Environment Services Center. The patterns of inferred magnetic fields may be followed accurately as far as 60 deg from central meridian. Such patterns will be used to improve predictions of coronal features during the next solar eclipse. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...577A.138K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...577A.138K">Numerical simulations of sheared magnetic lines at the solar null line</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kuźma, B.; Murawski, K.; Solov'ev, A. 2015-05-01 Aims: We perform numerical simulations of sheared magnetic lines at the magnetic null line configuration of two magnetic arcades that are settled in a gravitationally stratified and magnetically confined solar corona. Methods: We developed a general analytical model of a 2.5D solar atmospheric structure. As a particular application of this model, we adopted it for the curved magnetic field lines with an inverted Y shape that compose the null line above two magnetic arcades, which are embedded in the solar atmosphere that is specified by the realistic temperature distribution. The physical system is described by 2.5D magnetohydrodynamic equations that are numerically solved by the FLASH code. Results: The magnetic field line shearing, implemented about 200 km below the transition region, results in Alfvén and magnetoacoustic waves that are able to penetrate solar coronal regions above the magnetic null line. As a result of the coupling of these waves, partial reflection from the transition region and scattering from inhomogeneous regions the Alfvén waves experience fast attenuation on time scales comparable to their wave periods, and the physical system relaxes in time. The attenuation time grows with the large amplitude and characteristic growing time of the shearing. Conclusions: By having chosen a different magnetic flux function, the analytical model we devised can be adopted to derive equilibrium conditions for a diversity of 2.5D magnetic structures in the solar atmosphere. Movie associated to Fig. 5 is available in electronic form at http://www.aanda.org </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080038051&hterms=activity+Physics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dactivity%2BPhysics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080038051&hterms=activity+Physics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dactivity%2BPhysics">The Role of Magnetic Reconnection in Solar Activity</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Antiochos, Spiro; DeVore, C. R. 2008-01-01 The central challenge in solar/heliospheric physics is to understand how the emergence and transport of magnetic flux at the photosphere drives the structure and dynamics that we observe in the corona and heliosphere. This presentation focuses on the role of magnetic reconnection in determining solar/heliospheric activity. We demonstrate that two generic properties of the photospheric magnetic and velocity fields are responsible for the ubiquitous reconnection in the corona. First, the photospheric velocities are complex, which leads to the injection of energy and helicity into the coronal magnetic fields and to the efficient, formation of small-scale structure. Second, the flux distribution at the photosphere is multi-polar, which implies that topological discontinuities and, consequently, current sheets, must be present in the coronal magnetic field. We: present numerical simulations showing that photospherically-driven reconnection is responsible for the heating and dynamics of coronal plasma, and for the topology of the coronal/heliospheric magnetic field. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22666113-downward-catastrophe-solar-magnetic-flux-ropes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22666113-downward-catastrophe-solar-magnetic-flux-ropes">DOWNWARD CATASTROPHE OF SOLAR MAGNETIC FLUX ROPES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Zhang, Quanhao; Wang, Yuming; Hu, Youqiu 2016-07-10 2.5-dimensional time-dependent ideal magnetohydrodynamic (MHD) models in Cartesian coordinates were used in previous studies to seek MHD equilibria involving a magnetic flux rope embedded in a bipolar, partially open background field. As demonstrated by these studies, the equilibrium solutions of the system are separated into two branches: the flux rope sticks to the photosphere for solutions at the lower branch but is suspended in the corona for those at the upper branch. Moreover, a solution originally at the lower branch jumps to the upper, as the related control parameter increases and reaches a critical value, and the associated jump ismore » here referred to as an upward catastrophe. The present paper advances these studies in three aspects. First, the magnetic field is changed to be force-free; the system still experiences an upward catastrophe with an increase in each control parameter. Second, under the force-free approximation, there also exists a downward catastrophe, characterized by the jump of a solution from the upper branch to the lower. Both catastrophes are irreversible processes connecting the two branches of equilibrium solutions so as to form a cycle. Finally, the magnetic energy in the numerical domain is calculated. It is found that there exists a magnetic energy release for both catastrophes. The Ampère's force, which vanishes everywhere for force-free fields, appears only during the catastrophes and does positive work, which serves as a major mechanism for the energy release. The implications of the downward catastrophe and its relevance to solar activities are briefly discussed.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SPIE10615E..59D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SPIE10615E..59D">Hilbert-Huang transform analysis of long-term solar magnetic activity</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Deng, Linhua 2018-04-01 Astronomical time series analysis is one of the hottest and most important problems, and becomes the suitable way to deal with the underlying dynamical behavior of the considered nonlinear systems. The quasi-periodic analysis of solar magnetic activity has been carried out by various authors during the past fifty years. In this work, the novel Hilbert-Huang transform approach is applied to investigate the yearly numbers of polar faculae in the time interval from 1705 to 1999. The detected periodicities can be allocated to three components: the first one is the short-term variations with periods smaller than 11 years, the second one is the mid- term variations with classical periods from 11 years to 50 years, and the last one is the long-term variations with periods larger than 50 years. The analysis results improve our knowledge on the quasi-periodic variations of solar magnetic activity and could be provided valuable constraints for solar dynamo theory. Furthermore, our analysis results could be useful for understanding the long-term variations of solar magnetic activity, providing crucial information to describe and forecast solar magnetic activity indicators. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22518859-sun-like-magnetic-cycles-rapidly-rotating-young-solar-analog-hd','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22518859-sun-like-magnetic-cycles-rapidly-rotating-young-solar-analog-hd">SUN-LIKE MAGNETIC CYCLES IN THE RAPIDLY ROTATING YOUNG SOLAR ANALOG HD 30495</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Egeland, Ricky; Metcalfe, Travis S.; Hall, Jeffrey C. A growing body of evidence suggests that multiple dynamo mechanisms can drive magnetic variability on different timescales, not only in the Sun but also in other stars. Many solar activity proxies exhibit a quasi-biennial (∼2 year) variation, which is superimposed upon the dominant 11 year cycle. A well-characterized stellar sample suggests at least two different relationships between rotation period and cycle period, with some stars exhibiting long and short cycles simultaneously. Within this sample, the solar cycle periods are typical of a more rapidly rotating star, implying that the Sun might be in a transitional state or that it hasmore » an unusual evolutionary history. In this work, we present new and archival observations of dual magnetic cycles in the young solar analog HD 30495, a ∼1 Gyr old G1.5 V star with a rotation period near 11 days. This star falls squarely on the relationships established by the broader stellar sample, with short-period variations at ∼1.7 years and a long cycle of ∼12 years. We measure three individual long-period cycles and find durations ranging from 9.6 to 15.5 years. We find the short-term variability to be intermittent, but present throughout the majority of the time series, though its occurrence and amplitude are uncorrelated with the longer cycle. These essentially solar-like variations occur in a Sun-like star with more rapid rotation, though surface differential rotation measurements leave open the possibility of a solar equivalence.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22522027-spectro-polarimetric-imaging-reveals-helical-magnetic-fields-solar-prominence-feet','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22522027-spectro-polarimetric-imaging-reveals-helical-magnetic-fields-solar-prominence-feet">SPECTRO-POLARIMETRIC IMAGING REVEALS HELICAL MAGNETIC FIELDS IN SOLAR PROMINENCE FEET</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> González, M. J. Martínez; Sainz, R. Manso; Ramos, A. Asensio 2015-03-20 Solar prominences are clouds of cool plasma levitating above the solar surface and insulated from the million-degree corona by magnetic fields. They form in regions of complex magnetic topology, characterized by non-potential fields, which can evolve abruptly, disintegrating the prominence and ejecting magnetized material into the heliosphere. However, their physics is not yet fully understood because mapping such complex magnetic configurations and their evolution is extremely challenging, and must often be guessed by proxy from photometric observations. Using state-of-the-art spectro-polarimetric data, we reconstruct the structure of the magnetic field in a prominence. We find that prominence feet harbor helical magneticmore » fields connecting the prominence to the solar surface below.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015nova.pres..255K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015nova.pres..255K">Witnessing Solar Rejuvenation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kohler, Susanna 2015-09-01 At the end of last year, the Suns large-scale magnetic field suddenly strengthened, reaching its highest value in over two decades. Here, Neil Sheeley and Yi-Ming Wang (both of the Naval Research Laboratory) propose an explanation for why this happened and what it predicts for the next solar cycle.Magnetic StrengtheningUntil midway through 2014, solar cycle 24 the current solar cycle was remarkably quiet. Even at its peak, it averaged only 79 sunspots per year, compared to maximums of up to 190 in recent cycles. Thus it was rather surprising when, toward the end of 2014, the Suns large-scale magnetic field underwent a sudden rejuvenation, with its mean field leaping up to its highest values since 1991 and causing unprecedentedly large numbers of coronal loops to collapse inward.Yet in spite of the increase we observed in the Suns open flux (the magnetic flux leaving the Suns atmosphere, measured from Earth), there was not a significant increase in solar activity, as indicated by sunspot number and the rate of coronal mass ejections. This means that the number of sources of magnetic flux didnt increase so Sheeley and Wang conclude that flux must instead have been emerging from those sources in a more efficient way! But how?Aligned ActivityWSO open flux and the radial component of the interplanetary magnetic field (measures of the magnetic flux leaving the Suns photosphere and heliosphere, respectively), compared to sunspot number (in units of 100 sunspots). A sudden increase in flux is visible after the peak of each of the last four sunspot cycles. Click for a larger view! [Sheeley Wang 2015]The authors show that the active regions on the solar surface in late 2014 lined up in such a way that the emerging flux was enhanced, forming a strong equatorial dipole field that accounts for the sudden rejuvenation observed.Interestingly, this rejuvenation of the Suns open flux wasnt just a one-time thing; similar bursts have occurred shortly after the peak of every sunspot </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH41B2192K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH41B2192K">Can We Predict CME Deflections Based on Solar Magnetic Field Configuration Alone?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kay, C.; Opher, M.; Evans, R. M. 2013-12-01 Accurate space weather forecasting requires knowledge of the trajectory of coronal mass ejections (CMEs), including predicting CME deflections close to the Sun and through interplanetary space. Deflections of CMEs occur due to variations in the background magnetic field or solar wind speed, magnetic reconnection, and interactions with other CMEs. Using our newly developed model of CME deflections due to gradients in the background solar magnetic field, ForeCAT (Kay et al. 2013), we explore the questions: (a) do all simulated CMEs ultimately deflect to the minimum in the background solar magnetic field? (b) does the majority of the deflection occur in the lower corona below 4 Rs? ForeCAT does not include temporal variations in the magnetic field of active regions (ARs), spatial variations in the background solar wind speed, magnetic reconnection, or interactions with other CMEs. Therefore we focus on the effects of the steady state solar magnetic field. We explore two different Carrington Rotations (CRs): CR 2029 (April-May 2005) and CR 2077 (November-December 2008). Little is known about how the density and magnetic field fall with distance in the lower corona. We consider four density models derived from observations (Chen 1996, Mann et al. 2003, Guhathakurta et al. 2006, Leblanc et al. 1996) and two magnetic field models (PFSS and a scaled model). ForeCAT includes drag resulting from both CME propagation and deflection through the background solar wind. We vary the drag coefficient to explore the effect of drag on the deflection at 1 AU. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150007708','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150007708">Using Polar Coronal Hole Area Measurements to Determine the Solar Polar Magnetic Field Reversal in Solar Cycle 24</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Karna, N.; Webber, S.A. Hess; Pesnell, W.D. 2014-01-01 An analysis of solar polar coronal hole (PCH) areas since the launch of the Solar Dynamics Observatory (SDO) shows how the polar regions have evolved during Solar Cycle 24. We present PCH areas from mid-2010 through 2013 using data from the Atmospheric Imager Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) instruments onboard SDO. Our analysis shows that both the northern and southern PCH areas have decreased significantly in size since 2010. Linear fits to the areas derived from the magnetic-field properties indicate that, although the northern hemisphere went through polar-field reversal and reached solar-maximum conditions in mid-2012, the southern hemisphere had not reached solar-maximum conditions in the polar regions by the end of 2013. Our results show that solar-maximum conditions in each hemisphere, as measured by the area of the polar coronal holes and polar magnetic field, will be offset in time. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016A%26A...593A..35R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016A%26A...593A..35R">Magnetic fields of young solar twins</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rosén, L.; Kochukhov, O.; Hackman, T.; Lehtinen, J. 2016-09-01 Aims: The goal of this work is to study the magnetic fields of six young solar-analogue stars both individually, and collectively, to search for possible magnetic field trends with age. If such trends are found, they can be used to understand magnetism in the context of stellar evolution of solar-like stars and to understand the past of the Sun and the solar system. This is also important for the atmospheric evolution of the inner planets, Earth in particular. Methods: We used Stokes IV data from two different spectropolarimeters, NARVAL and HARPSpol. The least-squares deconvolution multi-line technique was used to increase the signal-to-noise ratio of the data. We then applied a modern Zeeman-Doppler imaging code in order to reconstruct the magnetic topology of all stars and the brightness distribution of one of our studied stars. Results: Our results show a significant decrease in the magnetic field strength and energy as the stellar age increases from 100 Myr to 250 Myr, while there is no significant age dependence of the mean magnetic field strength for stars with ages 250-650 Myr. The spread in the mean field strength between different stars is comparable to the scatter between different observations of individual stars. The meridional field component is weaker than the radial and azimuthal field components in 15 of the 16 magnetic maps. It turns out that 89-97% of the magnetic field energy is contained in l = 1 - 3. There is also no clear trend with age and distribution of field energy into poloidal/toroidal and axisymmetric/non-axisymmetric components within the sample. The two oldest stars in this study show an octupole component that is twice as strong as the quadrupole component. This is only seen in 1 of the 13 maps of the younger stars. One star, χ1 Ori, displays two field polarity switches during almost 5 yr of observations suggesting a magnetic cycle length of 2, 6, or 8 yr. Based on observations made with the HARPSpol instrument on the ESO 3.6 m </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770027147','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770027147">Sources of magnetic fields in recurrent interplanetary streams</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Burlaga, L. F.; Behannon, K. W.; Hansen, S. F.; Pneuman, G. W.; Feldman, W. C. 1977-01-01 The sources of magnetic fields in recurrent streams were examined. Most fields and plasmas at 1 AU were related to coronal holes, and the magnetic field lines were open in those holes. Some of the magnetic fields and plasmas were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines are more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes ranged from 2G to 18G. Average measured photospheric magnetic fields along the footprints of the corresponding unipolar fields on circular equatorial arcs at 2.5 solar radii had a similar range and average, but in two cases the intensities were approximately three times higher than the projected intensities. The coronal footprints of the sector boundaries on the source surface at 2.5 solar radii, meandered between -45 deg and +45 deg latitude, and their inclination ranged from near zero to near ninety degrees. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654163-solar-eruption-local-magnetic-parameters','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654163-solar-eruption-local-magnetic-parameters">SOLAR ERUPTION AND LOCAL MAGNETIC PARAMETERS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Lee, Jeongwoo; Chae, Jongchul; Liu, Chang It is now a common practice to use local magnetic parameters such as magnetic decay index for explaining solar eruptions from active regions, but there can be an alternative view that the global properties of the source region should be counted as a more important factor. We discuss this issue based on Solar Dynamics Observatory observations of the three successive eruptions within 1.5 hr from the NOAA active region 11444 and the magnetic parameters calculated using the nonlinear force-free field model. Two violent eruptions occurred in the regions with relatively high magnetic twist number (0.5–1.5) and high decay index (0.9–1.1)more » at the nominal height of the filament (12″) and otherwise a mild eruption occurred, which supports the local-parameter paradigm. Our main point is that the time sequence of the eruptions did not go with these parameters. It is argued that an additional factor, in the form of stabilizing force, should operate to determine the onset of the first eruption and temporal behaviors of subsequent eruptions. As supporting evidence, we report that the heating and fast plasma flow continuing for a timescale of an hour was the direct cause for the first eruption and that the unidirectional propagation of the disturbance determined the timing of subsequent eruptions. Both of these factors are associated with the overall magnetic structure rather than local magnetic properties of the active region.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010435','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010435">Particle-In-Cell Simulations of the Solar Wind Interaction with Lunar Crustal Magnetic Anomalies: Magnetic Cusp Regions</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Poppe, A. R.; Halekas, J. S.; Delory, G. T.; Farrell, W. M. 2012-01-01 As the solar wind is incident upon the lunar surface, it will occasionally encounter lunar crustal remanent magnetic fields. These magnetic fields are small-scale, highly non-dipolar, have strengths up to hundreds of nanotesla, and typically interact with the solar wind in a kinetic fashion. Simulations, theoretical analyses, and spacecraft observations have shown that crustal fields can reflect solar wind protons via a combination of magnetic and electrostatic reflection; however, analyses of surface properties have suggested that protons may still access the lunar surface in the cusp regions of crustal magnetic fields. In this first report from a planned series of studies, we use a 1 1/2-dimensional, electrostatic particle-in-cell code to model the self-consistent interaction between the solar wind, the cusp regions of lunar crustal remanent magnetic fields, and the lunar surface. We describe the self-consistent electrostatic environment within crustal cusp regions and discuss the implications of this work for the role that crustal fields may play regulating space weathering of the lunar surface via proton bombardment. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22127147-ubiquitous-solar-eruptions-driven-magnetized-vortex-tubes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22127147-ubiquitous-solar-eruptions-driven-magnetized-vortex-tubes">UBIQUITOUS SOLAR ERUPTIONS DRIVEN BY MAGNETIZED VORTEX TUBES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kitiashvili, I. N.; Kosovichev, A. G.; Lele, S. K. 2013-06-10 The solar surface is covered by high-speed jets transporting mass and energy into the solar corona and feeding the solar wind. The most prominent of these jets have been known as spicules. However, the mechanism initiating these eruption events is still unknown. Using realistic numerical simulations we find that small-scale eruptions are produced by ubiquitous magnetized vortex tubes generated by the Sun's turbulent convection in subsurface layers. The swirling vortex tubes (resembling tornadoes) penetrate into the solar atmosphere, capture and stretch background magnetic field, and push the surrounding material up, generating shocks. Our simulations reveal complicated high-speed flow patterns andmore » thermodynamic and magnetic structure in the erupting vortex tubes. The main new results are: (1) the eruptions are initiated in the subsurface layers and are driven by high-pressure gradients in the subphotosphere and photosphere and by the Lorentz force in the higher atmosphere layers; (2) the fluctuations in the vortex tubes penetrating into the chromosphere are quasi-periodic with a characteristic period of 2-5 minutes; and (3) the eruptions are highly non-uniform: the flows are predominantly downward in the vortex tube cores and upward in their surroundings; the plasma density and temperature vary significantly across the eruptions.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH13B2478G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH13B2478G">Measuring Solar Coronal Magnetism during the Total Solar Eclipse of 2017</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gibson, K. L.; Tomczyk, S. 2017-12-01 The total solar eclipse on August 21, 2017 provided a notable opportunity to measure the solar corona at specific emission wavelengths to gain information about coronal magnetic fields. Solar magnetic fields are intimately related to the generation of space weather and its effects on the earth, and the infrared imaging and polarization information collected on coronal emission lines here will enhance the scientific value of several other ongoing experiments, as well as benefit the astrophysics and upper atmosphere communities. Coronal measurements were collected during the 2 minute and 24 second totality period from Casper Mountain, WY. Computer-controlled telescopes automatically inserted four different narrow band pass filters to capture images in the visible range on a 4D PolCam, and in the infrared range on the FLIR 8501c camera. Each band pass filter selects a specific wavelength range that corresponds to a known coronal emission line possessing magnetic sensitivity. The 4D PolCam incorporated a novel grid of linear polarizers precisely aligned with the micron scale pixels. This allowed for direct measurement of the degree of linear polarization in a very small instrument with no external moving parts as is typically required. The FLIR offers short exposure times to freeze motion and output accurate thermal measurements. This allowed a new observation of the sun's corona using thermo infrared technology. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH13A2474F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH13A2474F">Solar Surface Velocity in the Large Scale estimated by Magnetic Element Tracking Method</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fujiyama, M.; Imada, S.; Iijima, H.; Machida, S. 2017-12-01 The 11years variation in the solar activity is one of the important sources of decadal variation in the solar-terrestrial environment. Therefore, predicting the solar cycle activity is crucial for the space weather. To build the prediction schemes for the next solar cycle is a key for the long-term space weather study. Recently, the relationship between polar magnetic field at the solar minimum and next solar cycle activity is intensively discussed. Nowadays, many people believe that the polar magnetic field at the solar minimum is one of the best predictor for the next solar cycle. To estimate polar magnetic field, Surface Flux Transport (SFT) model have been often used. On the other hand, SFT model needs several parameters, for example Meridional circulation, differential rotation, turbulent diffusion etc.. So far, those parameters have not been fully understood, and their uncertainties may affect the accuracy of the prediction. In this study, we try to discuss the parameters which are used in SFT model. We focus on two kinds of the solar surface motions, Differential rotation and Meridional circulation. First, we have developed Magnetic Element Tracking (MET) module, which is able to obtain the surface velocity by using the magnetic field data. We have used SOHO/MDI and SDO/HMI for the magnetic field data. By using MET, we study the solar surface motion over 2 cycle (nearly 24 years), and we found that the velocity variation is related to the active region belt. This result is consistent with [Hathaway et al., 2011]. Further, we apply our module to the Hinode/SOT data which spatial resolution is high. Because of its high resolution, we can discuss the surface motion close to the pole which has not been discussed enough. Further, we discuss the relationship between the surface motion and the magnetic field strength and the location of longitude. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122.6240H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122.6240H">Distribution and solar wind control of compressional solar wind-magnetic anomaly interactions observed at the Moon by ARTEMIS</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Halekas, J. S.; Poppe, A. R.; Lue, C.; Farrell, W. M.; McFadden, J. P. 2017-06-01 A statistical investigation of 5 years of observations from the two-probe Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) mission reveals that strong compressional interactions occur infrequently at high altitudes near the ecliptic but can form in a wide range of solar wind conditions and can occur up to two lunar radii downstream from the lunar limb. The compressional events, some of which may represent small-scale collisionless shocks ("limb shocks"), occur in both steady and variable interplanetary magnetic field (IMF) conditions, with those forming in steady IMF well organized by the location of lunar remanent crustal magnetization. The events observed by ARTEMIS have similarities to ion foreshock phenomena, and those observed in variable IMF conditions may result from either local lunar interactions or distant terrestrial foreshock interactions. Observed velocity deflections associated with compressional events are always outward from the lunar wake, regardless of location and solar wind conditions. However, events for which the observed velocity deflection is parallel to the upstream motional electric field form in distinctly different solar wind conditions and locations than events with antiparallel deflections. Consideration of the momentum transfer between incoming and reflected solar wind populations helps explain the observed characteristics of the different groups of events.<abstract type="synopsis"><title type="main">Plain Language SummaryWe survey the environment around the Moon to determine when and where strong amplifications in the charged particle density and magnetic field strength occur. These structures may be some of the smallest shock waves in the solar system, and learning about their formation informs us about the interaction of charged particles with small-scale magnetic fields throughout the solar system and beyond. We find that these compressions occur in an extended region </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvD..96i1103A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvD..96i1103A">Limiting neutrino magnetic moments with Borexino Phase-II solar neutrino data</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Agostini, M.; Altenmüller, K.; Appel, S.; Atroshchenko, V.; Bagdasarian, Z.; Basilico, D.; Bellini, G.; Benziger, J.; Bick, D.; Bonfini, G.; Bravo, D.; Caccianiga, B.; Calaprice, F.; Caminata, A.; Caprioli, S.; Carlini, M.; Cavalcante, P.; Chepurnov, A.; Choi, K.; Collica, L.; D'Angelo, D.; Davini, S.; Derbin, A.; Ding, X. F.; Di Ludovico, A.; Di Noto, L.; Drachnev, I.; Fomenko, K.; Formozov, A.; Franco, D.; Froborg, F.; Gabriele, F.; Galbiati, C.; Ghiano, C.; Giammarchi, M.; Goretti, A.; Gromov, M.; Guffanti, D.; Hagner, C.; Houdy, T.; Hungerford, E.; Ianni, Aldo; Ianni, Andrea; Jany, A.; Jeschke, D.; Kobychev, V.; Korablev, D.; Korga, G.; Kryn, D.; Laubenstein, M.; Litvinovich, E.; Lombardi, F.; Lombardi, P.; Ludhova, L.; Lukyanchenko, G.; Lukyanchenko, L.; Machulin, I.; Manuzio, G.; Marcocci, S.; Martyn, J.; Meroni, E.; Meyer, M.; Miramonti, L.; Misiaszek, M.; Muratova, V.; Neumair, B.; Oberauer, L.; Opitz, B.; Orekhov, V.; Ortica, F.; Pallavicini, M.; Papp, L.; Penek, Ã.-.; Pilipenko, N.; Pocar, A.; Porcelli, A.; Ranucci, G.; Razeto, A.; Re, A.; Redchuk, M.; Romani, A.; Roncin, R.; Rossi, N.; Schönert, S.; Semenov, D.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Stokes, L. F. F.; Suvorov, Y.; Tartaglia, R.; Testera, G.; Thurn, J.; Toropova, M.; Unzhakov, E.; Vishneva, A.; Vogelaar, R. B.; von Feilitzsch, F.; Wang, H.; Weinz, S.; Wojcik, M.; Wurm, M.; Yokley, Z.; Zaimidoroga, O.; Zavatarelli, S.; Zuber, K.; Zuzel, G.; Borexino Collaboration 2017-11-01 A search for the solar neutrino effective magnetic moment has been performed using data from 1291.5 days exposure during the second phase of the Borexino experiment. No significant deviations from the expected shape of the electron recoil spectrum from solar neutrinos have been found, and a new upper limit on the effective neutrino magnetic moment of μνeff<2.8×10 -11 μB at 90% C.L. has been set using constraints on the sum of the solar neutrino fluxes implied by the radiochemical gallium experiments. Using the limit for the effective neutrino moment, new limits for the magnetic moments of the neutrino flavor states, and for the elements of the neutrino magnetic moments matrix for Dirac and Majorana neutrinos, are derived. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22661400-prediction-solar-flares-using-unique-signatures-magnetic-field-images','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22661400-prediction-solar-flares-using-unique-signatures-magnetic-field-images">PREDICTION OF SOLAR FLARES USING UNIQUE SIGNATURES OF MAGNETIC FIELD IMAGES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Raboonik, Abbas; Safari, Hossein; Alipour, Nasibe Prediction of solar flares is an important task in solar physics. The occurrence of solar flares is highly dependent on the structure and topology of solar magnetic fields. A new method for predicting large (M- and X-class) flares is presented, which uses machine learning methods applied to the Zernike moments (ZM) of magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory for a period of six years from 2010 June 2 to 2016 August 1. Magnetic field images consisting of the radial component of the magnetic field are converted to finite sets of ZMs andmore » fed to the support vector machine classifier. ZMs have the capability to elicit unique features from any 2D image, which may allow more accurate classification. The results indicate whether an arbitrary active region has the potential to produce at least one large flare. We show that the majority of large flares can be predicted within 48 hr before their occurrence, with only 10 false negatives out of 385 flaring active region magnetograms and 21 false positives out of 179 non-flaring active region magnetograms. Our method may provide a useful tool for the prediction of solar flares, which can be employed alongside other forecasting methods.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SSRv..210..367C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SSRv..210..367C">The Global Solar Dynamo</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cameron, R. H.; Dikpati, M.; Brandenburg, A. 2017-09-01 A brief summary of the various observations and constraints that underlie solar dynamo research are presented. The arguments that indicate that the solar dynamo is an alpha-omega dynamo of the Babcock-Leighton type are then shortly reviewed. The main open questions that remain are concerned with the subsurface dynamics, including why sunspots emerge at preferred latitudes as seen in the familiar butterfly wings, why the cycle is about 11 years long, and why the sunspot groups emerge tilted with respect to the equator (Joy's law). Next, we turn to magnetic helicity, whose conservation property has been identified with the decline of large-scale magnetic fields found in direct numerical simulations at large magnetic Reynolds numbers. However, magnetic helicity fluxes through the solar surface can alleviate this problem and connect theory with observations, as will be discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.6000S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.6000S">Interaction between Solar Wind and Lunar Magnetic Anomalies observed by Kaguya MAP-PACE</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Saito, Yoshifumi; Yokota, Shoichiro; Tanaka, Takaaki; Asamura, Kazushi; Nishino, Masaki; Yamamoto, Tadateru; Uemura, Kota; Tsunakawa, Hideo 2010-05-01 It is known that Moon has neither global intrinsic magnetic field nor thick atmosphere. Different from the Earth's case where the intrinsic global magnetic field prevents the solar wind from penetrating into the magnetosphere, solar wind directly impacts the lunar surface. Since the discovery of the lunar crustal magnetic field in 1960s, several papers have been published concerning the interaction between the solar wind and the lunar magnetic anomalies. MAG/ER on Lunar Prospector found heating of the solar wind electrons presumably due to the interaction between the solar wind and the lunar magnetic anomalies and the existence of the mini-magnetosphere was suggested. However, the detailed mechanism of the interaction has been unclear mainly due to the lack of the in-situ observed data of low energy ions. MAgnetic field and Plasma experiment - Plasma energy Angle and Composition Experiment (MAP-PACE) on Kaguya (SELENE) completed its ˜1.5-year observation of the low energy charged particles around the Moon on 10 June, 2009. Kaguya was launched on 14 September 2007 by H2A launch vehicle from Tanegashima Space Center in Japan. Kaguya was inserted into a circular lunar polar orbit of 100km altitude and continued observation for nearly 1.5 years till it impacted the Moon on 10 June 2009. During the last 5 months, the orbit was lowered to ˜50km-altitude between January 2009 and April 2009, and some orbits had further lower perilune altitude of ˜10km after April 2009. MAP-PACE consisted of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). All the sensors performed quite well as expected from the laboratory experiment carried out before launch. Since each sensor had hemispherical field of view, two electron sensors and two ion sensors that were installed on the spacecraft panels opposite to each other could cover full 3-dimensional phase space of low energy electrons and ions. One of the ion sensors IMA was </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870052703&hterms=active+site&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dactive%2Bsite','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870052703&hterms=active+site&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dactive%2Bsite">Measurement and interpretation of magnetic shear in solar active regions</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hagyard, M. J.; Rabin, D. M. 1986-01-01 In this paper a summary and synthesis are presented for results on the role of magnetic shear in the flare process that have been derived from the series of Flare Buildup Study Workshops in the Solar Maximum Analysis program. With emphasis on observations, the mechanisms that seem to produce the sheared magnetic configurations observed in flaring active regions are discussed. The spatial and temporal correlations of this shear with the onset of solar flares are determined from quantitative analyses of measurements of the vector magnetic field. The question of why some areas of sheared magnetic fields are the sites of flares and others are not is investigated observationally. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22357182-magnetic-helicity-emerging-solar-active-regions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22357182-magnetic-helicity-emerging-solar-active-regions">Magnetic helicity in emerging solar active regions</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Liu, Y.; Hoeksema, J. T.; Bobra, M. Using vector magnetic field data from the Helioseismic and Magnetic Imager instrument aboard the Solar Dynamics Observatory, we study magnetic helicity injection into the corona in emerging active regions (ARs) and examine the hemispheric helicity rule. In every region studied, photospheric shearing motion contributes most of the helicity accumulated in the corona. In a sample of 28 emerging ARs, 17 follow the hemisphere rule (61% ± 18% at a 95% confidence interval). Magnetic helicity and twist in 25 ARs (89% ± 11%) have the same sign. The maximum magnetic twist, which depends on the size of an AR, is inferredmore » in a sample of 23 emerging ARs with a bipolar magnetic field configuration.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22661432-magnetic-properties-solar-active-regions-govern-large-solar-flares-eruptions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22661432-magnetic-properties-solar-active-regions-govern-large-solar-flares-eruptions">MAGNETIC PROPERTIES OF SOLAR ACTIVE REGIONS THAT GOVERN LARGE SOLAR FLARES AND ERUPTIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Toriumi, Shin; Schrijver, Carolus J.; Harra, Louise K. Solar flares and coronal mass ejections (CMEs), especially the larger ones, emanate from active regions (ARs). With the aim of understanding the magnetic properties that govern such flares and eruptions, we systematically survey all flare events with Geostationary Orbiting Environmental Satellite levels of ≥M5.0 within 45° from disk center between 2010 May and 2016 April. These criteria lead to a total of 51 flares from 29 ARs, for which we analyze the observational data obtained by the Solar Dynamics Observatory . More than 80% of the 29 ARs are found to exhibit δ -sunspots, and at least three ARs violatemore » Hale’s polarity rule. The flare durations are approximately proportional to the distance between the two flare ribbons, to the total magnetic flux inside the ribbons, and to the ribbon area. From our study, one of the parameters that clearly determine whether a given flare event is CME-eruptive or not is the ribbon area normalized by the sunspot area, which may indicate that the structural relationship between the flaring region and the entire AR controls CME productivity. AR characterization shows that even X-class events do not require δ -sunspots or strong-field, high-gradient polarity inversion lines. An investigation of historical observational data suggests the possibility that the largest solar ARs, with magnetic flux of 2 × 10{sup 23} Mx, might be able to produce “superflares” with energies of the order of 10{sup 34} erg. The proportionality between the flare durations and magnetic energies is consistent with stellar flare observations, suggesting a common physical background for solar and stellar flares.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2086265','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2086265">Anterior open bite treatment with magnets.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kiliaridis, S; Egermark, I; Thilander, B 1990-11-01 The aim of this study was to examine the effects of repelling magnets on the treatment of anterior open bite and compare them with the effects of acrylic posterior bite-blocks. Twenty patients, aged 9-16 years with skeletal anterior open bite, were randomly divided into two groups. In one group the patients wore posterior repelling magnet splints and in the other they wore acrylic posterior bite-blocks of the same thickness as the magnet splints. The patients were instructed to use their appliance as much as possible (the minimum accepted being 18 hours daily) during a 6-month period. Dental casts, intra-oral photos, and lateral cephalograms were taken before and after treatment, and the patients were also examined regularly to identify the development of any craniomandibular disorders. In the first group, the dental and skeletal vertical relation responded quickly to the magnet treatment. The open bite was generally closed in just under 4 months, especially in patients in early mixed dentition. Spacing in the labial segments decreased in some cases, while slight crowding was induced in others. Transverse problems, i.e. unilateral cross-bite, sometimes followed by scissor-bite on the opposite side, was observed in those patients who were in the early mixed dentition and had used the magnets intensively. The patients who wore acrylic posterior bite-blocks also showed improvement in the dental and skeletal vertical relationships, especially during the first months. This was followed by a 'plateau' period. No transverse problems were found in these patients. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AdSpR..42.1475C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AdSpR..42.1475C">Correlation between solar flare productivity and photospheric vector magnetic fields</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cui, Yanmei; Wang, Huaning 2008-11-01 Studying the statistical correlation between the solar flare productivity and photospheric magnetic fields is very important and necessary. It is helpful to set up a practical flare forecast model based on magnetic properties and improve the physical understanding of solar flare eruptions. In the previous study ([Cui, Y.M., Li, R., Zhang, L.Y., He, Y.L., Wang, H.N. Correlation between solar flare productivity and photospheric magnetic field properties 1. Maximum horizontal gradient, length of neutral line, number of singular points. Sol. Phys. 237, 45 59, 2006]; from now on we refer to this paper as ‘Paper I’), three measures of the maximum horizontal gradient, the length of the neutral line, and the number of singular points are computed from 23990 SOHO/MDI longitudinal magnetograms. The statistical relationship between the solar flare productivity and these three measures is well fitted with sigmoid functions. In the current work, the three measures of the length of strong-shear neutral line, total unsigned current, and total unsigned current helicity are computed from 1353 vector magnetograms observed at Huairou Solar Observing Station. The relationship between the solar flare productivity and the current three measures can also be well fitted with sigmoid functions. These results are expected to be beneficial to future operational flare forecasting models. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH21C..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH21C..08W">Does the magnetic expansion factor play a role in solar wind acceleration?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wallace, S.; Arge, C. N.; Pihlstrom, Y. 2017-12-01 For the past 25+ years, the magnetic expansion factor (fs) has been a parameter used in the calculation of terminal solar wind speed (vsw) in the Wang-Sheeley-Arge (WSA) coronal and solar wind model. The magnetic expansion factor measures the rate of flux tube expansion in cross section between the photosphere out to 2.5 solar radii (i.e., source surface), and is inversely related to vsw (Wang & Sheeley, 1990). Since the discovery of this inverse relationship, the physical role that fs plays in solar wind acceleration has been debated. In this study, we investigate whether fs plays a causal role in determining terminal solar wind speed or merely serves as proxy. To do so, we study pseudostreamers, which occur when coronal holes of the same polarity are near enough to one another to limit field line expansion. Pseudostreamers are of particular interest because despite having low fs, spacecraft observations show that solar wind emerging from these regions have slow to intermediate speeds of 350-550 km/s (Wang et al., 2012). In this work, we develop a methodology to identify pseudostreamers that are magnetically connected to satellites using WSA output produced with ADAPT input maps. We utilize this methodology to obtain the spacecraft-observed solar wind speed from the exact parcel of solar wind that left the pseudostreamer. We then compare the pseudostreamer's magnetic expansion factor with the observed solar wind speed from multiple spacecraft (i.e., ACE, STEREO-A & B, Ulysses) magnetically connected to the region. We will use this methodology to identify several cases ( 20) where spacecraft are magnetically connected to pseudostreamers, and perform a statistical analysis to determine the correlation of fs within pseudostreamers and the terminal speed of the solar wind emerging from them. This work will help determine if fs plays a physical role in the speed of solar wind originating from regions that typically produce slow wind. This work compliments previous case </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010032414','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010032414">High Resolution Observations and Modeling of Small-Scale Solar Magnetic Elements</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Berger, Thomas E. 2001-01-01 This research contract investigating the radiative transfer and dynamic physics of the smallest observable magnetic structures in the solar photosphere. Due to the lack of a high-resolution visible light satellite instrument for solar studies, all data were acquired using ground-based instrumentation. The primary goal of the investigation was to understand the formation and evolution of "G-band bright points" in relation to the associated magnetic elements. G-band bright points are small (on the order of 100 kin or less in diameter) bright signatures associated with magnetic flux elements in the photosphere. They are seen in the A2A-X2 4308 A molecular bandhead of the CH radical ill the solar spectrum and offer the highest spatial resolution and highest contrast "tracers" of small magnetic structure on the Sun. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhDT........14C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhDT........14C">A study of solar magnetic fields below the surface, at the surface, and in the solar atmosphere - understanding the cause of major solar activity</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chintzoglou, Georgios 2016-04-01 Magnetic fields govern all aspects of solar activity from the 11-year solar cycle to the most energetic events in the solar system, such as solar flares and Coronal Mass Ejections (CMEs). As seen on the surface of the sun, this activity emanates from localized concentrations of magnetic fields emerging sporadically from the solar interior. These locations are called solar Active Regions (ARs). However, the fundamental processes regarding the origin, emergence and evolution of solar magnetic fields as well as the generation of solar activity are largely unknown or remain controversial. In this dissertation, multiple important issues regarding solar magnetism and activities are addressed, based on advanced observations obtained by AIA and HMI instruments aboard the SDO spacecraft. First, this work investigates the formation of coronal magnetic flux ropes (MFRs), structures associated with major solar activity such as CMEs. In the past, several theories have been proposed to explain the cause of this major activity, which can be categorized in two contrasting groups (a) the MFR is formed in the eruption, and (b) the MFR pre-exists the eruption. This remains a topic of heated debate in modern solar physics. This dissertation provides a complete treatment of the role of MFRs from their genesis all the way to their eruption and even destruction. The study has uncovered the pre-existence of two weakly twisted MFRs, which formed during confined flaring 12 hours before their associated CMEs. Thus, it provides unambiguous evidence for MFRs truly existing before the CME eruptions, resolving the pre-existing MFR controversy. Second, this dissertation addresses the 3-D magnetic structure of complex emerging ARs. In ARs the photospheric fields might show all aspects of complexity, from simple bipolar regions to extremely complex multi-polar surface magnetic distributions. In this thesis, we introduce a novel technique to infer the subphotospheric configuration of emerging </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29104346','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29104346">Tessellated permanent magnet circuits for flow-through, open gradient separations of weakly magnetic materials.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Moore, Lee R; Williams, P Stephen; Chalmers, Jeffrey J; Zborowski, Maciej 2017-04-01 Emerging microfluidic-based cell assays favor label-free red blood cell (RBC) depletion. Magnetic separation of RBC is possible because of the paramagnetism of deoxygenated hemoglobin but the process is slow for open-gradient field configurations. In order to increase the throughput, periodic arrangements of the unit magnets were considered, consisting of commercially available Nd-Fe-B permanent magnets and soft steel flux return pieces. The magnet design is uniquely suitable for multiplexing by magnet tessellation, here meaning the tiling of the magnet assembly cross-sectional plane by periodic repetition of the magnet and the flow channel shapes. The periodic pattern of magnet magnetizations allows a reduction of the magnetic material per channel with minimal distortion of the field cylindrical symmetry inside the magnet apertures. A number of such magnet patterns are investigated for separator performance, size and economy with the goal of designing an open-gradient magnetic separator capable of reducing the RBC number concentration a hundred-fold in 1 mL whole blood per hour. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790004815','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790004815">Papers presented to the Conference on Origins of Planetary Magnetism. [magnetic properties of meteorites and solar, lunar, and planetary magnetic fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> 1978-01-01 Abstracts of 63 papers accepted for publication are presented. Topics cover geomagnetism in the context of planetary magnetism, lunar magnetism, the dynamo theory and nondynamo processes, comparative planetary magnetism (terrestrial and outer planets), meteoritic magnetism, and the early solar magnetic field. Author and subject indexes are provided. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SoPh..292..189M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SoPh..292..189M">Interplanetary Magnetic Flux Ropes as Agents Connecting Solar Eruptions and Geomagnetic Activities</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Marubashi, K.; Cho, K.-S.; Ishibashi, H. 2017-12-01 We investigate the solar wind structure for 11 cases that were selected for the campaign study promoted by the International Study of Earth-affecting Solar Transients (ISEST) MiniMax24 Working Group 4. We can identify clear flux rope signatures in nine cases. The geometries of the nine interplanetary magnetic flux ropes (IFRs) are examined with a model-fitting analysis with cylindrical and toroidal force-free flux rope models. For seven cases in which magnetic fields in the solar source regions were observed, we compare the IFR geometries with magnetic structures in their solar source regions. As a result, we can confirm the coincidence between the IFR orientation and the orientation of the magnetic polarity inversion line (PIL) for six cases, as well as the so-called helicity rule as regards the handedness of the magnetic chirality of the IFR, depending on which hemisphere of the Sun the IFR originated from, the northern or southern hemisphere; namely, the IFR has right-handed (left-handed) magnetic chirality when it is formed in the southern (northern) hemisphere of the Sun. The relationship between the orientation of IFRs and PILs can be taken as evidence that the flux rope structure created in the corona is in most cases carried through interplanetary space with its orientation maintained. In order to predict magnetic field variations on Earth from observations of solar eruptions, further studies are needed about the propagation of IFRs because magnetic fields observed at Earth significantly change depending on which part of the IFR hits the Earth. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SSRv..210..227C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SSRv..210..227C">Minimal Magnetic States of the Sun and the Solar Wind: Implications for the Origin of the Slow Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cliver, E. W.; von Steiger, R. 2017-09-01 During the last decade it has been proposed that both the Sun and the solar wind have minimum magnetic states, lowest order levels of magnetism that underlie the 11-yr cycle as well as longer-term variability. Here we review the literature on basal magnetic states at the Sun and in the heliosphere and draw a connection between the two based on the recent deep 2008-2009 minimum between cycles 23 and 24. In particular, we consider the implications of the low solar activity during the recent minimum for the origin of the slow solar wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780025037&hterms=solar+use&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsolar%2Buse','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780025037&hterms=solar+use&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsolar%2Buse">A new use of high resolution magnetograms. [solar activity and magnetic flux</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Baum, P. J.; Bratenahl, A. 1978-01-01 Ground-based solar magnetograms are frequently in error by as much as twenty percent and contribute to the poor correlation between magnetic changes and solar flares. High resolution measurement of the magnetic field component, which is normal to the photosphere and measured at photospheric height, can be used to construct a magnetic flux partition function F. Therefore, dF/dt is an EMF which drives atmospheric currents in reconnecting solar active regions. With a high quality magnetograph, the solar probe can be used to obtain good estimates of F and dF/dt and thereby the energy stored as induced solar atmospheric currents during quiescent interflare periods. Should a flare occur during a favorable observing period, the present method of analysis should show characteristic signatures in F, DF/dt, and especially, in the stored flux computed from dF/dt. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930057243&hterms=Free+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DFree%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930057243&hterms=Free+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DFree%2Benergy">The free energies of partially open coronal magnetic fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Low, B. C.; Smith, D. F. 1993-01-01 A simple model of the low corona is examined in terms of a static polytropic atmosphere in equilibrium with a global magnetic field. The question posed is whether magnetostatic states with partially open magnetic fields may contain magnetic energies in excess of those in fully open magnetic fields. Based on the analysis presented here, it is concluded that the cross-field electric currents in the pre-eruption corona are a viable source of the bulk of the energies in a mass ejection and its associated flare. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663957-internal-gravity-waves-magnetized-solar-atmosphere-magnetic-field-effects','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663957-internal-gravity-waves-magnetized-solar-atmosphere-magnetic-field-effects">Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Vigeesh, G.; Steiner, O.; Jackiewicz, J., E-mail: vigeesh@leibniz-kis.de Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in themore » Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high- β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E.877F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E.877F">Future Trends in Solar Radio Astronomy and Coronal Magnetic-Field Measurements</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fleishman, Gregory; Nita, Gelu; Gary, Dale Solar radio astronomy has an amazingly rich, but yet largely unexploited, potential for probing the solar corona and chromosphere. Radio emission offers multiple ways of detecting and tracking electron beams, studying chromospheric and coronal thermal structure, plasma processes, particle acceleration, and measuring magnetic fields. To turn the mentioned potential into real routine diagnostics, two major components are needed: (1) well-calibrated observations with high spatial, spectral, and temporal resolutions and (2) accurate and reliable theoretical models and fast numerical tools capable of recovering the emission source parameters from the radio data. This report gives a brief overview of the new, expanded, and planned radio facilities, such as Expanded Owens Valley Solar Array (EOVSA), Jansky Very Large Array (JVLA), Chinese Solar Radio Heliograph (CSRH), Upgraded Siberian Solar Radio Telescope (USSRT), and Frequency Agile Solar Radiotelescope (FASR) with the emphasis on their ability to measure the coronal magnetic fields in active regions and flares. In particular, we emphasize the new tools for 3D modeling of the radio emission and forward fitting tools in development needed to derive the magnetic field data from the radio measurements. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654410-compensating-faraday-depolarization-magnetic-helicity-solar-corona','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654410-compensating-faraday-depolarization-magnetic-helicity-solar-corona">Compensating Faraday Depolarization by Magnetic Helicity in the Solar Corona</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Brandenburg, Axel; Ashurova, Mohira B.; Jabbari, Sarah, E-mail: brandenb@nordita.org A turbulent dynamo in spherical geometry with an outer corona is simulated to study the sign of magnetic helicity in the outer parts. In agreement with earlier studies, the sign in the outer corona is found to be opposite to that inside the dynamo. Line-of-sight observations of polarized emission are synthesized to explore the feasibility of using the local reduction of Faraday depolarization to infer the sign of helicity of magnetic fields in the solar corona. This approach was previously identified as an observational diagnostic in the context of galactic magnetic fields. Based on our simulations, we show that thismore » method can be successful in the solar context if sufficient statistics are gathered by using averages over ring segments in the corona separately for the regions north and south of the solar equator.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28553705','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28553705">Origin of Open-Circuit Voltage Loss in Polymer Solar Cells and Perovskite Solar Cells.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kim, Hyung Do; Yanagawa, Nayu; Shimazaki, Ai; Endo, Masaru; Wakamiya, Atsushi; Ohkita, Hideo; Benten, Hiroaki; Ito, Shinzaburo 2017-06-14 Herein, the open-circuit voltage (V OC ) loss in both polymer solar cells and perovskite solar cells is quantitatively analyzed by measuring the temperature dependence of V OC to discuss the difference in the primary loss mechanism of V OC between them. As a result, the photon energy loss for polymer solar cells is in the range of about 0.7-1.4 eV, which is ascribed to temperature-independent and -dependent loss mechanisms, while that for perovskite solar cells is as small as about 0.5 eV, which is ascribed to a temperature-dependent loss mechanism. This difference is attributed to the different charge generation and recombination mechanisms between the two devices. The potential strategies for the improvement of V OC in both solar cells are further discussed on the basis of the experimental data. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654161-magnetic-flux-cancelation-trigger-solar-quiet-region-coronal-jets','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654161-magnetic-flux-cancelation-trigger-solar-quiet-region-coronal-jets">MAGNETIC FLUX CANCELATION AS THE TRIGGER OF SOLAR QUIET-REGION CORONAL JETS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L. We report observations of 10 random on-disk solar quiet-region coronal jets found in high-resolution extreme ultraviolet (EUV) images from the Solar Dynamics Observatory ( SDO )/Atmospheric Imaging Assembly and having good coverage in magnetograms from the SDO /Helioseismic and Magnetic Imager (HMI). Recent studies show that coronal jets are driven by the eruption of a small-scale filament (called a minifilament ). However, the trigger of these eruptions is still unknown. In the present study, we address the question: what leads to the jet-driving minifilament eruptions? The EUV observations show that there is a cool-transition-region-plasma minifilament present prior to each jetmore » event and the minifilament eruption drives the jet. By examining pre-jet evolutionary changes in the line of sight photospheric magnetic field, we observe that each pre-jet minifilament resides over the neutral line between majority-polarity and minority-polarity patches of magnetic flux. In each of the 10 cases, the opposite-polarity patches approach and merge with each other (flux reduction between 21% and 57%). After several hours, continuous flux cancelation at the neutral line apparently destabilizes the field holding the cool-plasma minifilament to erupt and undergo internal reconnection, and external reconnection with the surrounding coronal field. The external reconnection opens the minifilament field allowing the minifilament material to escape outward, forming part of the jet spire. Thus, we found that each of the 10 jets resulted from eruption of a minifilament following flux cancelation at the neutral line under the minifilament. These observations establish that magnetic flux cancelation is usually the trigger of quiet-region coronal jet eruptions.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...853...94W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...853...94W">Observations of a Small Interplanetary Magnetic Flux Rope Opening by Interchange Reconnection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, J. M.; Feng, H. Q.; Zhao, G. Q. 2018-01-01 Interchange reconnection, specifically magnetic reconnection between open magnetic fields and closed magnetic flux ropes, plays a major role in the heliospheric magnetic flux budget. It is generally accepted that closed magnetic field lines of interplanetary magnetic flux ropes (IMFRs) can gradually open through reconnection between one of its legs and other open field lines until no closed field lines are left to contribute flux to the heliosphere. In this paper, we report an IMFR associated with a magnetic reconnection exhaust, whereby its closed field lines were opening by a magnetic reconnection event near 1 au. The reconnection exhaust and the following IMFR were observed on 2002 February 2 by both the Wind and ACE spacecraft. Observations on counterstreaming suprathermal electrons revealed that most magnetic field lines of the IMFR were closed, especially those after the front boundary of the IMFR, with both ends connected to the Sun. The unidirectional suprathermal electron strahls before the exhaust manifested the magnetic field lines observed before the exhaust was open. These observations provide direct evidence that closed field lines of IMFRs can be opened by interchange reconnection in interplanetary space. This is the first report of the closed field lines of IMFRs being opened by interchange reconnection in interplanetary space. This type of interplanetary interchange reconnection may pose important implications for balancing the heliospheric flux budget. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19960021320&hterms=imprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dimprint','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19960021320&hterms=imprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dimprint">Evidence of active region imprints on the solar wind structure</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hick, P.; Jackson, B. V. 1995-01-01 A common descriptive framework for discussing the solar wind structure in the inner heliosphere uses the global magnetic field as a reference: low density, high velocity solar wind emanates from open magnetic fields, with high density, low speed solar wind flowing outward near the current sheet. In this picture, active regions, underlying closed magnetic field structures in the streamer belt, leave little or no imprint on the solar wind. We present evidence from interplanetary scintillation measurements of the 'disturbance factor' g that active regions play a role in modulating the solar wind and possibly contribute to the solar wind mass output. Hence we find that the traditional view of the solar wind, though useful in understanding many features of solar wind structure, is oversimplified and possibly neglects important aspects of solar wind dynamics </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH23D2703P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH23D2703P">The Solar Wind from Pseudostreamers and their Environs: Opportunities for Observations with Parker Solar Probe and Solar Orbiter</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Panasenco, O.; Velli, M.; Panasenco, A.; Lionello, R. 2017-12-01 The solar dynamo and photospheric convection lead to three main types of structures extending from the solar surface into the corona - active regions, solar filaments (prominences when observed at the limb) and coronal holes. These structures exist over a wide range of scales, and are interlinked with each other in evolution and dynamics. Active regions can form clusters of magnetic activity and the strongest overlie sunspots. In the decay of active regions, the boundaries separating opposite magnetic polarities (neutral lines) develop specific structures called filament channels above which filaments form. In the presence of flux imbalance decaying active regions can also give birth to lower latitude coronal holes. The accumulation of magnetic flux at coronal hole boundaries also creates conditions for filament formation: polar crown filaments are permanently present at the boundaries of the polar coronal holes. Mid-latitude and equatorial coronal holes - the result of active region evolution - can create pseudostreamers if other coronal holes of the same polarity are present. While helmet streamers form between open fields of opposite polarities, the pseudostreamer, characterized by a smaller coronal imprint, typically shows a more prominent straight ray or stalk extending from the corona. The pseudostreamer base at photospheric heights is multipolar; often one observes tripolar magnetic configurations with two neutral lines - where filaments can form - separating the coronal holes. Here we discuss the specific role of filament channels on pseudostreamer topology and on solar wind properties. 1D numerical analysis of pseudostreamers shows that the properties of the solar wind from around PSs depend on the presence/absence of filament channels, number of channels and chirality at thepseudostreamer base low in the corona. We review and model possible coronal magnetic configurations and solar wind plasma properties at different distances from the solar surface that </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5667671','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5667671">Tessellated permanent magnet circuits for flow-through, open gradient separations of weakly magnetic materials</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Moore, Lee R.; Williams, P. Stephen; Chalmers, Jeffrey J.; Zborowski, Maciej 2017-01-01 Emerging microfluidic-based cell assays favor label-free red blood cell (RBC) depletion. Magnetic separation of RBC is possible because of the paramagnetism of deoxygenated hemoglobin but the process is slow for open-gradient field configurations. In order to increase the throughput, periodic arrangements of the unit magnets were considered, consisting of commercially available Nd-Fe-B permanent magnets and soft steel flux return pieces. The magnet design is uniquely suitable for multiplexing by magnet tessellation, here meaning the tiling of the magnet assembly cross-sectional plane by periodic repetition of the magnet and the flow channel shapes. The periodic pattern of magnet magnetizations allows a reduction of the magnetic material per channel with minimal distortion of the field cylindrical symmetry inside the magnet apertures. A number of such magnet patterns are investigated for separator performance, size and economy with the goal of designing an open-gradient magnetic separator capable of reducing the RBC number concentration a hundred-fold in 1 mL whole blood per hour. PMID:29104346 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...787..100P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...787..100P">On the Helicity of Open Magnetic Fields</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Prior, C.; Yeates, A. R. 2014-06-01 We reconsider the topological interpretation of magnetic helicity for magnetic fields in open domains, and relate this to the relative helicity. Specifically, our domains stretch between two parallel planes, and each of these ends may be magnetically open. It is demonstrated that, while the magnetic helicity is gauge-dependent, its value in any gauge may be physically interpreted as the average winding number among all pairs of field lines with respect to some orthonormal frame field. In fact, the choice of gauge is equivalent to the choice of reference field in the relative helicity, meaning that the magnetic helicity is no less physically meaningful. We prove that a particular gauge always measures the winding with respect to a fixed frame, and propose that this is normally the best choice. For periodic fields, this choice is equivalent to measuring relative helicity with respect to a potential reference field. However, for aperiodic fields, we show that the potential field can be twisted. We prove by construction that there always exists a possible untwisted reference field. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920055106&hterms=Free+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFree%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920055106&hterms=Free+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFree%2Benergy">Energy buildup in sheared force-free magnetic fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wolfson, Richard; Low, Boon C. 1992-01-01 Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9909E..1HM','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9909E..1HM">Solar adaptive optics: specificities, lessons learned, and open alternatives</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Montilla, I.; Marino, J.; Asensio Ramos, A.; Collados, M.; Montoya, L.; Tallon, M. 2016-07-01 First on sky adaptive optics experiments were performed on the Dunn Solar Telescope on 1979, with a shearing interferometer and limited success. Those early solar adaptive optics efforts forced to custom-develop many components, such as Deformable Mirrors and WaveFront Sensors, which were not available at that time. Later on, the development of the correlation Shack-Hartmann marked a breakthrough in solar adaptive optics. Since then, successful Single Conjugate Adaptive Optics instruments have been developed for many solar telescopes, i.e. the National Solar Observatory, the Vacuum Tower Telescope and the Swedish Solar Telescope. Success with the Multi Conjugate Adaptive Optics systems for GREGOR and the New Solar Telescope has proved to be more difficult to attain. Such systems have a complexity not only related to the number of degrees of freedom, but also related to the specificities of the Sun, used as reference, and the sensing method. The wavefront sensing is performed using correlations on images with a field of view of 10", averaging wavefront information from different sky directions, affecting the sensing and sampling of high altitude turbulence. Also due to the low elevation at which solar observations are performed we have to include generalized fitting error and anisoplanatism, as described by Ragazzoni and Rigaut, as non-negligible error sources in the Multi Conjugate Adaptive Optics error budget. For the development of the next generation Multi Conjugate Adaptive Optics systems for the Daniel K. Inouye Solar Telescope and the European Solar Telescope we still need to study and understand these issues, to predict realistically the quality of the achievable reconstruction. To improve their designs other open issues have to be assessed, i.e. possible alternative sensing methods to avoid the intrinsic anisoplanatism of the wide field correlation Shack-Hartmann, new parameters to estimate the performance of an adaptive optics solar system, alternatives to </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21452660-quasi-biennial-oscillations-solar-tachocline-caused-magnetic-rossby-wave-instabilities','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21452660-quasi-biennial-oscillations-solar-tachocline-caused-magnetic-rossby-wave-instabilities">QUASI-BIENNIAL OSCILLATIONS IN THE SOLAR TACHOCLINE CAUSED BY MAGNETIC ROSSBY WAVE INSTABILITIES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Zaqarashvili, Teimuraz V.; Carbonell, Marc; Oliver, Ramon 2010-11-20 Quasi-biennial oscillations (QBOs) are frequently observed in solar activity indices. However, no clear physical mechanism for the observed variations has been suggested so far. Here, we study the stability of magnetic Rossby waves in the solar tachocline using the shallow water magnetohydrodynamic approximation. Our analysis shows that the combination of typical differential rotation and a toroidal magnetic field with a strength of {>=}10{sup 5} G triggers the instability of the m = 1 magnetic Rossby wave harmonic with a period of {approx}2 years. This harmonic is antisymmetric with respect to the equator and its period (and growth rate) depends onmore » the differential rotation parameters and magnetic field strength. The oscillations may cause a periodic magnetic flux emergence at the solar surface and consequently may lead to the observed QBO in solar activity features. The period of QBOs may change throughout a cycle, and from cycle to cycle, due to variations of the mean magnetic field and differential rotation in the tachocline.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22522131-multi-shell-magnetic-twisters-new-mechanism-coronal-heating-solar-wind-acceleration','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22522131-multi-shell-magnetic-twisters-new-mechanism-coronal-heating-solar-wind-acceleration">MULTI-SHELL MAGNETIC TWISTERS AS A NEW MECHANISM FOR CORONAL HEATING AND SOLAR WIND ACCELERATION</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Murawski, K.; Srivastava, A. K.; Dwivedi, B. N. 2015-07-20 We perform numerical simulations of impulsively generated Alfvén waves in an isolated photospheric flux tube and explore the propagation of these waves along such magnetic structure that extends from the photosphere, where these waves are triggered, to the solar corona, and we analyze resulting magnetic shells. Our model of the solar atmosphere is constructed by adopting the temperature distribution based on the semi-empirical model and specifying the curved magnetic field lines that constitute the magnetic flux tube that is rooted in the solar photosphere. The evolution of the solar atmosphere is described by 3D, ideal MHD equations that are numerically solvedmore » by the FLASH code. Our numerical simulations reveal, based on the physical properties of the multi-shell magnetic twisters and the amount of energy and momentum associated with them, that these multi-shell magnetic twisters may be responsible for the observed heating of the lower solar corona and for the formation of solar wind. Moreover, it is likely that the existence of these twisters can be verified by high-resolution observations.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...833..144X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...833..144X">The Rotation of the Solar Photospheric Magnetic Field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xu, J. C.; Gao, P. X. 2016-12-01 The rotational characteristics of the solar photospheric magnetic field at four flux ranges are investigated together with the total flux of active regions (MFar) and quiet regions (MFqr). The first four ranges (MF1-4) are (1.5-2.9) × 1018, (2.9-32.0) × 1018, (3.20-4.27) × 1019, and (4.27-38.01) × 1019, respectively (the unit is Mx per element). Daily values of the flux data are extracted from magnetograms of the Michelson Doppler Imager on board the Solar and Heliospheric Observatory. Lomb-Scargle periodograms show that only MF2, MF4, MFqr, and MFar exhibit rotational periods. The periods of the first three types of flux are very similar, I.e., 26.20, 26.23, and 26.24 days, respectively, while that of MFar is longer, 26.66 days. This indicates that active regions rotate more slowly than quiet regions on average, and strong magnetic fields tend to repress the surface rotation. Sinusoidal function fittings and cross-correlation analyses reveal that MFar leads MF2 and MF4 by 5 and 1 days, respectively. This is speculated to be related with the decaying of active regions. MF2 and MFar are negatively correlated, while both MF4 and MFqr are positively correlated with MFar. At the timescale of the solar activity cycle, MFar leads (negatively) MF2 by around one year (350 days), and leads MF4 by about 3 rotation periods (82 days). The relation between MF2 and MFar may be explained by the possibility that the former mainly comes from a higher latitude, or emerges from the subsurface shear layer. We conjecture that MF4 may partly come from the magnetic flux of active regions; this verifies previous results that were obtained with indirect solar magnetic indices. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999ASPC..184.....S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999ASPC..184.....S">Third Advances in Solar Physics Euroconference: Magnetic Fields and Oscillations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schmieder, B.; Hofmann, A.; Staude, J. The third Advances in Solar Physics Euroconference (ASPE) "Magnetic Fields and Oscillations"concluded a series of three Euroconferences sponsored by the European Union. The meeting took place in Caputh near Potsdam, Germany, on September 22-25, 1998, followed by the JOSO (Joint Organization for Solar Observations) 30th Annual Board Meeting on September 26, 1998. The ASPE formula is attractive and compares well with other meetings with "show-and-tell" character. This meeting had 122 participants coming from 26 countries; 36 participants came from countries formerly behind the Iron Curtain; a "politically incorrect" estimate says that 48 participants were below 35 years of age, with an unusually large female-to-male ratio. This characteristic of youngness is the more striking since solar physics is a perhaps overly established field exhibiting an overly senior age profile. It was a good opportunity to train this young generation in Solar Physics. The conference topic "Magnetic Fields and Oscillations" obviously was wide enough to cater to many an interest. These proceedings are organized according to the structure of the meeting. They include the topics 'High resolution spectropolarimetry and magnetometry', 'Flux-tube dynamics', 'Modelling of the 3-D magnetic field structure', 'Mass motions and magnetic fields in sunspot penumbral structures', 'Sunspot oscillations', 'Oscillations in active regions - diagnostics and seismology', 'Network and intranetwork structure and dynamics', and 'Waves in magnetic structures'. These topics covered the first 2.5 days of the conference. The reviews, oral contributions, and poster presentations were by no means all of the meeting. The ASPE formula also adds extensive plenary sessions of JOSO Working groups on topics that involve planning of Europe-wide collaboration. At this meeting these concerned solar observing techniques, solar data bases, coordination between SOHO and ground-based observing, and preparations for August 11, 1999 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SSRv..186..491J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SSRv..186..491J">Magnetic Flux Transport at the Solar Surface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jiang, J.; Hathaway, D. H.; Cameron, R. H.; Solanki, S. K.; Gizon, L.; Upton, L. 2014-12-01 After emerging to the solar surface, the Sun's magnetic field displays a complex and intricate evolution. The evolution of the surface field is important for several reasons. One is that the surface field, and its dynamics, sets the boundary condition for the coronal and heliospheric magnetic fields. Another is that the surface evolution gives us insight into the dynamo process. In particular, it plays an essential role in the Babcock-Leighton model of the solar dynamo. Describing this evolution is the aim of the surface flux transport model. The model starts from the emergence of magnetic bipoles. Thereafter, the model is based on the induction equation and the fact that after emergence the magnetic field is observed to evolve as if it were purely radial. The induction equation then describes how the surface flows—differential rotation, meridional circulation, granular, supergranular flows, and active region inflows—determine the evolution of the field (now taken to be purely radial). In this paper, we review the modeling of the various processes that determine the evolution of the surface field. We restrict our attention to their role in the surface flux transport model. We also discuss the success of the model and some of the results that have been obtained using this model. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1176386','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1176386">Method for cleaning a solar cell surface opening made with a solar etch paste</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Rohatgi, Ajeet; Meemongkolkiat, Vichai 2010-06-22 A thin silicon solar cell having a back dielectric passivation and rear contact with local back surface field is described. Specifically, the solar cell may be fabricated from a crystalline silicon wafer having a thickness from 50 to 500 micrometers. A barrier layer and a dielectric layer are applied at least to the back surface of the silicon wafer to protect the silicon wafer from deformation when the rear contact is formed. At least one opening is made to the dielectric layer. An aluminum contact that provides a back surface field is formed in the opening and on the dielectric layer. The aluminum contact may be applied by screen printing an aluminum paste having from one to 12 atomic percent silicon and then applying a heat treatment at 750 degrees Celsius. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820042725&hterms=Wind+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DWind%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820042725&hterms=Wind+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DWind%2Benergy">Solar wind energy transfer through the magnetopause of an open magnetosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Lee, L. C.; Roederer, J. G. 1982-01-01 An expression is derived for the total power, transferred from the solar wind to an open magnetosphere, which consists of the electromagnetic energy rate and the particle kinetic energy rate. The total rate of energy transferred from the solar wind to an open magnetosphere mainly consists of kinetic energy, and the kinetic energy flux is carried by particles, penetrating from the solar wind into the magnetosphere, which may contribute to the observed flow in the plasma mantle and which will eventually be convected slowly toward the plasma sheet by the electric field as they flow down the tail. While the electromagnetic energy rate controls the near-earth magnetospheric activity, the kinetic energy rate should dominate the dynamics of the distant magnetotail. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...835...94O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...835...94O">Chirality and Magnetic Configurations of Solar Filaments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ouyang, Y.; Zhou, Y. H.; Chen, P. F.; Fang, C. 2017-01-01 It has been revealed that the magnetic topology in the solar atmosphere displays hemispheric preference, I.e., helicity is mainly negative/positive in the northern/southern hemispheres, respectively. However, the strength of the hemispheric rule and its cyclic variation are controversial. In this paper, we apply a new method based on the filament drainage to 571 erupting filaments from 2010 May to 2015 December in order to determine the filament chirality and its hemispheric preference. It is found that 91.6% of our sample of erupting filaments follows the hemispheric rule of helicity sign. It is also found that the strength of the hemispheric preference of the quiescent filaments decreases slightly from ˜97% in the rising phase to ˜85% in the declining phase of solar cycle 24, whereas the strength of the intermediate filaments keeps a high value around 96 ± 4% at all times. Only the active-region filaments show significant variations. Their strength of the hemispheric rule rises from ˜63% to ˜95% in the rising phase, and keeps a high value of 82% ± 5% during the declining phase. Furthermore, during a half-year period around the solar maximum, their hemispheric preference totally vanishes. Additionally, we also diagnose the magnetic configurations of the filaments based on our indirect method and find that in our sample of erupting events, 89% are inverse-polarity filaments with a flux rope magnetic configuration, whereas 11% are normal-polarity filaments with a sheared arcade configuration. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ExA....33..271P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ExA....33..271P">Solar magnetism eXplorer (SolmeX). Exploring the magnetic field in the upper atmosphere of our closest star</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad, A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt, W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.; Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald, V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.; Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N.-E.; Raymond, J.; Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.; Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J.-C. 2012-04-01 The magnetic field plays a pivotal role in many fields of Astrophysics. This is especially true for the physics of the solar atmosphere. Measuring the magnetic field in the upper solar atmosphere is crucial to understand the nature of the underlying physical processes that drive the violent dynamics of the solar corona—that can also affect life on Earth. SolmeX, a fully equipped solar space observatory for remote-sensing observations, will provide the first comprehensive measurements of the strength and direction of the magnetic field in the upper solar atmosphere. The mission consists of two spacecraft, one carrying the instruments, and another one in formation flight at a distance of about 200 m carrying the occulter to provide an artificial total solar eclipse. This will ensure high-quality coronagraphic observations above the solar limb. SolmeX integrates two spectro-polarimetric coronagraphs for off-limb observations, one in the EUV and one in the IR, and three instruments for observations on the disk. The latter comprises one imaging polarimeter in the EUV for coronal studies, a spectro-polarimeter in the EUV to investigate the low corona, and an imaging spectro-polarimeter in the UV for chromospheric studies. SOHO and other existing missions have investigated the emission of the upper atmosphere in detail (not considering polarization), and as this will be the case also for missions planned for the near future. Therefore it is timely that SolmeX provides the final piece of the observational quest by measuring the magnetic field in the upper atmosphere through polarimetric observations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654248-sympathetic-solar-filament-eruptions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654248-sympathetic-solar-filament-eruptions">SYMPATHETIC SOLAR FILAMENT ERUPTIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Wang, Rui; Liu, Ying D.; Zimovets, Ivan 2016-08-10 The 2015 March 15 coronal mass ejection as one of the two that together drove the largest geomagnetic storm of solar cycle 24 so far was associated with sympathetic filament eruptions. We investigate the relations between the different filaments involved in the eruption. A surge-like small-scale filament motion is confirmed as the trigger that initiated the erupting filament with multi-wavelength observations and using a forced magnetic field extrapolation method. When the erupting filament moved to an open magnetic field region, it experienced an obvious acceleration process and was accompanied by a C-class flare and the rise of another larger filamentmore » that eventually failed to erupt. We measure the decay index of the background magnetic field, which presents a critical height of 118 Mm. Combining with a potential field source surface extrapolation method, we analyze the distributions of the large-scale magnetic field, which indicates that the open magnetic field region may provide a favorable condition for F2 rapid acceleration and have some relation with the largest solar storm. The comparison between the successful and failed filament eruptions suggests that the confining magnetic field plays an important role in the preconditions for an eruption.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010272','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010272">The Helioseismic and Magnetic Imager (HMI) Investigation for the Solar Dynamics Observatory (SDO)</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Scherrer, Philip Hanby; Schou, Jesper; Bush, R. I.; Kosovichev, A. G.; Bogart, R. S.; Hoeksema, J. T.; Liu, Y.; Duvall, T. L., Jr.; Zhao, J.; Title, A. M.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140010272'); toggleEditAbsImage('author_20140010272_show'); toggleEditAbsImage('author_20140010272_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140010272_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140010272_hide"> 2011-01-01 The Helioseismic and Magnetic Imager (HMI) instrument and investigation as a part of the NASA Solar Dynamics Observatory (SDO) is designed to study convection-zone dynamics and the solar dynamo, the origin and evolution of sunspots, active regions, and complexes of activity, the sources and drivers of solar magnetic activity and disturbances, links between the internal processes and dynamics of the corona and heliosphere, and precursors of solar disturbances for space-weather forecasts. A brief overview of the instrument, investigation objectives, and standard data products is presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910055755&hterms=topology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtopology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910055755&hterms=topology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dtopology">Probing the magnetic topologies of magnetic clouds by means of solar energetic particles</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Kahler, S. W.; Reames, D. V. 1991-01-01 Solar energetic particles (SEPs) have been used as probes of magnetic cloud topologies. The rapid access of SEPs to the interiors of many clouds indicates that the cloud field lines extend back to the sun and hence are not plasmoids. The small modulation of galactic cosmic rays associated with clouds also suggests that the magnetic fields of clouds are not closed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28706068','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28706068">Reconciling solar and stellar magnetic cycles with nonlinear dynamo simulations.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Strugarek, A; Beaudoin, P; Charbonneau, P; Brun, A S; do Nascimento, J-D 2017-07-14 The magnetic fields of solar-type stars are observed to cycle over decadal periods-11 years in the case of the Sun. The fields originate in the turbulent convective layers of stars and have a complex dependency upon stellar rotation rate. We have performed a set of turbulent global simulations that exhibit magnetic cycles varying systematically with stellar rotation and luminosity. We find that the magnetic cycle period is inversely proportional to the Rossby number, which quantifies the influence of rotation on turbulent convection. The trend relies on a fundamentally nonlinear dynamo process and is compatible with the Sun's cycle and those of other solar-type stars. Copyright © 2017, American Association for the Advancement of Science. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26069350','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26069350">The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hayashi, K; Hoeksema, J T; Liu, Y; Bobra, M G; Sun, X D; Norton, A A Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation modules are implemented at the Joint Science Operation Center (JSOC) of the Solar Dynamics Observatory (SDO). The modules regularly produce three-dimensional data of the time-relaxed minimum-energy state of the solar corona using global solar-surface magnetic-field maps created from Helioseismic and Magnetic Imager (HMI) full-disk magnetogram data. With the assumption of a polytropic gas with specific-heat ratio of 1.05, three types of simulation products are currently generated: i) simulation data with medium spatial resolution using the definitive calibrated synoptic map of the magnetic field with a cadence of one Carrington rotation, ii) data with low spatial resolution using the definitive version of the synchronic frame format of the magnetic field, with a cadence of one day, and iii) low-resolution data using near-real-time (NRT) synchronic format of the magnetic field on a daily basis. The MHD data available in the JSOC database are three-dimensional, covering heliocentric distances from 1.025 to 4.975 solar radii, and contain all eight MHD variables: the plasma density, temperature, and three components of motion velocity, and three components of the magnetic field. This article describes details of the MHD simulations as well as the production of the input magnetic-field maps, and details of the products available at the JSOC database interface. To assess the merits and limits of the model, we show the simulated data in early 2011 and compare with the actual coronal features observed by the Atmospheric Imaging Assembly (AIA) and the near-Earth in-situ data. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPD....40.0916H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPD....40.0916H">Solar Mean Magnetic Field Observed by GONG</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Harvey, J. W.; Petrie, G.; Clark, R.; GONG Team 2009-05-01 The average line-of-sight (LOS) magnetic field of the Sun has been observed for decades, either by measuring the circular polarization across a selected spectrum line using integrated sunlight or by averaging such measurements in spatially resolved images. The GONG instruments produce full-disk LOS magnetic images every minute, which can be averaged to yield the mean magnetic field nearly continuously. Such measurements are well correlated with the heliospheric magnetic field observed near Earth about 4 days later. They are also a measure of solar activity on long and short time scales. Averaging a GONG magnetogram, with nominal noise of 3 G per pixel, results in a noise level of about 4 mG. This is low enough that flare-related field changes have been seen in the mean field signal with time resolution of 1 minute. Longer time scales readily show variations associated with rotation of magnetic patterns across the solar disk. Annual changes due to the varying visibility of the polar magnetic fields may also be seen. Systematic effects associated with modulator non-uniformity require correction and limit the absolute accuracy of the GONG measurements. Comparison of the measurements with those from other instruments shows high correlation but suggest that GONG measurements of field strength are low by a factor of about two. The source of this discrepancy is not clear. Fourier analysis of 2007 and 2008 time series of the GONG mean field measurements shows strong signals at 27.75 and 26.84/2 day (synodic) periods with the later period showing more power. The heliospheric magnetic field near Earth shows the same periods but with reversed power dominance. The Global Oscillation Network Group (GONG) project is managed by NSO, which is operated by AURA, Inc. under a cooperative agreement with the National Science Foundation. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22370310-prediction-solar-activity-from-solar-background-magnetic-field-variations-cycles','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22370310-prediction-solar-activity-from-solar-background-magnetic-field-variations-cycles">Prediction of solar activity from solar background magnetic field variations in cycles 21-23</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Shepherd, Simon J.; Zharkov, Sergei I.; Zharkova, Valentina V., E-mail: s.j.shepherd@brad.ac.uk, E-mail: s.zharkov@hull.ac.uk, E-mail: valentina.zharkova@northumbria.ac.uk 2014-11-01 A comprehensive spectral analysis of both the solar background magnetic field (SBMF) in cycles 21-23 and the sunspot magnetic field in cycle 23 reported in our recent paper showed the presence of two principal components (PCs) of SBMF having opposite polarity, e.g., originating in the northern and southern hemispheres, respectively. Over a duration of one solar cycle, both waves are found to travel with an increasing phase shift toward the northern hemisphere in odd cycles 21 and 23 and to the southern hemisphere in even cycle 22. These waves were linked to solar dynamo waves assumed to form in differentmore » layers of the solar interior. In this paper, for the first time, the PCs of SBMF in cycles 21-23 are analyzed with the symbolic regression technique using Hamiltonian principles, allowing us to uncover the underlying mathematical laws governing these complex waves in the SBMF presented by PCs and to extrapolate these PCs to cycles 24-26. The PCs predicted for cycle 24 very closely fit (with an accuracy better than 98%) the PCs derived from the SBMF observations in this cycle. This approach also predicts a strong reduction of the SBMF in cycles 25 and 26 and, thus, a reduction of the resulting solar activity. This decrease is accompanied by an increasing phase shift between the two predicted PCs (magnetic waves) in cycle 25 leading to their full separation into the opposite hemispheres in cycle 26. The variations of the modulus summary of the two PCs in SBMF reveals a remarkable resemblance to the average number of sunspots in cycles 21-24 and to predictions of reduced sunspot numbers compared to cycle 24: 80% in cycle 25 and 40% in cycle 26.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890058245&hterms=alicia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dalicia%2Bd','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890058245&hterms=alicia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dalicia%2Bd">Solar wind-magnetosphere coupling during intense magnetic storms (1978-1979)</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gonzalez, Walter D.; Gonzalez, Alicia L. C.; Tsurutani, Bruce T.; Smith, Edward J.; Tang, Frances 1989-01-01 The solar wind-magnetosphere coupling problem during intense magnetic storms was investigated for ten intense magnetic storm events occurring between August 16, 1978 to December 28, 1979. Particular attention was given to the dependence of the ring current energization on the ISEE-measured solar-wind parameters and the evolution of the ring current during the main phase of the intense storms. Several coupling functions were tested as energy input, and several sets of the ring current decay time-constant were searched for the best correlation with the Dst response. Results indicate that a large-scale magnetopause reconnection operates during an intense storm event and that the solar wind ram pressure plays an important role in the energization of the ring current. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667721-chirality-magnetic-configurations-solar-filaments','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667721-chirality-magnetic-configurations-solar-filaments">CHIRALITY AND MAGNETIC CONFIGURATIONS OF SOLAR FILAMENTS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Ouyang, Y.; Zhou, Y. H.; Chen, P. F. It has been revealed that the magnetic topology in the solar atmosphere displays hemispheric preference, i.e., helicity is mainly negative/positive in the northern/southern hemispheres, respectively. However, the strength of the hemispheric rule and its cyclic variation are controversial. In this paper, we apply a new method based on the filament drainage to 571 erupting filaments from 2010 May to 2015 December in order to determine the filament chirality and its hemispheric preference. It is found that 91.6% of our sample of erupting filaments follows the hemispheric rule of helicity sign. It is also found that the strength of the hemisphericmore » preference of the quiescent filaments decreases slightly from ∼97% in the rising phase to ∼85% in the declining phase of solar cycle 24, whereas the strength of the intermediate filaments keeps a high value around 96 ± 4% at all times. Only the active-region filaments show significant variations. Their strength of the hemispheric rule rises from ∼63% to ∼95% in the rising phase, and keeps a high value of 82% ± 5% during the declining phase. Furthermore, during a half-year period around the solar maximum, their hemispheric preference totally vanishes. Additionally, we also diagnose the magnetic configurations of the filaments based on our indirect method and find that in our sample of erupting events, 89% are inverse-polarity filaments with a flux rope magnetic configuration, whereas 11% are normal-polarity filaments with a sheared arcade configuration.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH43A2796M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH43A2796M">Magnetic Flux Cancellation as the Trigger of Solar Coronal Jets</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McGlasson, R.; Panesar, N. K.; Sterling, A. C.; Moore, R. L. 2017-12-01 Coronal jets are narrow eruptions in the solar corona, and are often observed in extreme ultraviolet (EUV) and X-ray images. They occur everywhere on the solar disk: in active regions, quiet regions, and coronal holes (Raouafi et al. 2016). Recent studies indicate that most coronal jets in quiet regions and coronal holes are driven by the eruption of a minifilament (Sterling et al. 2015), and that this eruption follows flux cancellation at the magnetic neutral line under the pre-eruption minifilament (Panesar et al. 2016). We confirm this picture for a large sample of jets in quiet regions and coronal holes using multithermal (304 Å 171 Å, 193 Å, and 211 Å) extreme ultraviolet (EUV) images from the Solar Dynamics Observatory (SDO) /Atmospheric Imaging Assembly (AIA) and line-of-sight magnetograms from the SDO /Helioseismic and Magnetic Imager (HMI). We report observations of 60 randomly selected jet eruptions. We have analyzed the magnetic cause of these eruptions and measured the base size and the duration of each jet using routines in SolarSoft IDL. By examining the evolutionary changes in the magnetic field before, during, and after jet eruption, we found that each of these jets resulted from minifilament eruption triggered by flux cancellation at the neutral line. In agreement with the above studies, we found our jets to have an average base diameter of 7600 ± 2700 km and an average duration of 9.0 ± 3.6 minutes. These observations confirm that minifilament eruption is the driver and magnetic flux cancellation is the primary trigger mechanism for nearly all coronal hole and quiet region coronal jet eruptions. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38..419S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38..419S">Interaction between solar wind and lunar magnetic anomalies observed by MAP-PACE on Kaguya</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Saito, Yoshifumi; Yokota, Shoichiro; Tanaka, Takaaki; Asamura, Kazushi; Nishino, Masaki N.; Yamamoto, Tadateru I.; Tsunakawa, Hideo It is well known that the Moon has neither global intrinsic magnetic field nor thick atmosphere. Different from the Earth's case where the intrinsic global magnetic field prevents the solar wind from penetrating into the magnetosphere, solar wind directly impacts the lunar surface. MAgnetic field and Plasma experiment -Plasma energy Angle and Composition Experiment (MAP-PACE) on Kaguya (SELENE) completed its 1.5-year observation of the low energy charged particles around the Moon on 10 June 2009. Kaguya was launched on 14 September 2007 by H2A launch vehicle from Tanegashima Space Center in Japan. Kaguya was inserted into a circular lunar polar orbit of 100km altitude and continued observation for nearly 1.5 years till it impacted the Moon on 10 June 2009. During the last 5 months, the orbit was lowered to 50km-altitude between January 2009 and April 2009, and some orbits had further lower perilune altitude of 10km after April 2009. MAP-PACE consisted of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). Since each sensor had hemispherical field of view, two electron sensors and two ion sensors that were installed on the spacecraft panels opposite to each other could cover full 3-dimensional phase space of low energy electrons and ions. One of the ion sensors IMA was an energy mass spectrometer. IMA measured mass identified ion energy spectra that had never been obtained at 100km altitude polar orbit around the Moon. When Kaguya flew over South Pole Aitken region, where strong magnetic anomalies exist, solar wind ions reflected by magnetic anomalies were observed. These ions had much higher flux than the solar wind protons scattered at the lunar surface. The magnetically reflected ions had nearly the same energy as the incident solar wind ions while the solar wind protons scattered at the lunar surface had slightly lower energy than the incident solar wind ions. At 100km altitude, when the reflected ions </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPD....47.0315K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPD....47.0315K">Automated detection of open magnetic field regions in EUV images</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Krista, Larisza Diana; Reinard, Alysha 2016-05-01 Open magnetic regions on the Sun are either long-lived (coronal holes) or transient (dimmings) in nature, but both appear as dark regions in EUV images. For this reason their detection can be done in a similar way. As coronal holes are often large and long-lived in comparison to dimmings, their detection is more straightforward. The Coronal Hole Automated Recognition and Monitoring (CHARM) algorithm detects coronal holes using EUV images and a magnetogram. The EUV images are used to identify dark regions, and the magnetogam allows us to determine if the dark region is unipolar - a characteristic of coronal holes. There is no temporal sensitivity in this process, since coronal hole lifetimes span days to months. Dimming regions, however, emerge and disappear within hours. Hence, the time and location of a dimming emergence need to be known to successfully identify them and distinguish them from regular coronal holes. Currently, the Coronal Dimming Tracker (CoDiT) algorithm is semi-automated - it requires the dimming emergence time and location as an input. With those inputs we can identify the dimming and track it through its lifetime. CoDIT has also been developed to allow the tracking of dimmings that split or merge - a typical feature of dimmings.The advantage of these particular algorithms is their ability to adapt to detecting different types of open field regions. For coronal hole detection, each full-disk solar image is processed individually to determine a threshold for the image, hence, we are not limited to a single pre-determined threshold. For dimming regions we also allow individual thresholds for each dimming, as they can differ substantially. This flexibility is necessary for a subjective analysis of the studied regions. These algorithms were developed with the goal to allow us better understand the processes that give rise to eruptive and non-eruptive open field regions. We aim to study how these regions evolve over time and what environmental </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH13C2491L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH13C2491L">Studying the Formation and Evolution of Eruptive Solar Magnetic Flux Ropes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Linton, M. 2017-12-01 Solar magnetic eruptions are dramatic sources of solar activity, and dangerous sources of space weather hazards. Many of these eruptions take the form of magnetic flux ropes, i.e., magnetic fieldlines wrapping around a core magnetic flux tube. Investigating the processes which form these flux ropes both prior to and during eruption, and investigating their evolution after eruption, can give us a critical window into understanding the sources of and processes involved in these eruptions. This presentation will discuss modeling and observational investigations into these various phases of flux rope formation, eruption, and evolution, and will discuss how these different explorations can be used to develop a more complete picture of erupting flux rope dynamics. This work is funded by the NASA Living with a Star program. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010A%26A...513L...6B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010A%26A...513L...6B">Evidence of small-scale magnetic concentrations dragged by vortex motion of solar photospheric plasma</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Balmaceda, L.; Vargas Domínguez, S.; Palacios, J.; Cabello, I.; Domingo, V. 2010-04-01 Vortex-type motions have been measured by tracking bright points in high-resolution observations of the solar photosphere. These small-scale motions are thought to be determinant in the evolution of magnetic footpoints and their interaction with plasma and therefore likely to play a role in heating the upper solar atmosphere by twisting magnetic flux tubes. We report the observation of magnetic concentrations being dragged towards the center of a convective vortex motion in the solar photosphere from high-resolution ground-based and space-borne data. We describe this event by analyzing a series of images at different solar atmospheric layers. By computing horizontal proper motions, we detect a vortex whose center appears to be the draining point for the magnetic concentrations detected in magnetograms and well-correlated with the locations of bright points seen in G-band and CN images. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22126959-hemispheric-asymmetries-solar-photospheric-magnetism-radiative-particulate-heliospheric-impacts','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22126959-hemispheric-asymmetries-solar-photospheric-magnetism-radiative-particulate-heliospheric-impacts">HEMISPHERIC ASYMMETRIES OF SOLAR PHOTOSPHERIC MAGNETISM: RADIATIVE, PARTICULATE, AND HELIOSPHERIC IMPACTS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> McIntosh, Scott W.; Burkepile, Joan; Miesch, Mark 2013-03-10 Among many other measurable quantities, the summer of 2009 saw a considerable low in the radiative output of the Sun that was temporally coincident with the largest cosmic-ray flux ever measured at 1 AU. Combining measurements and observations made by the Solar and Heliospheric Observatory (SOHO) and Solar Dynamics Observatory (SDO) spacecraft we begin to explore the complexities of the descending phase of solar cycle 23, through the 2009 minimum into the ascending phase of solar cycle 24. A hemispheric asymmetry in magnetic activity is clearly observed and its evolution monitored and the resulting (prolonged) magnetic imbalance must have hadmore » a considerable impact on the structure and energetics of the heliosphere. While we cannot uniquely tie the variance and scale of the surface magnetism to the dwindling radiative and particulate output of the star, or the increased cosmic-ray flux through the 2009 minimum, the timing of the decline and rapid recovery in early 2010 would appear to inextricably link them. These observations support a picture where the Sun's hemispheres are significantly out of phase with each other. Studying historical sunspot records with this picture in mind shows that the northern hemisphere has been leading since the middle of the last century and that the hemispheric ''dominance'' has changed twice in the past 130 years. The observations presented give clear cause for concern, especially with respect to our present understanding of the processes that produce the surface magnetism in the (hidden) solar interior-hemispheric asymmetry is the normal state-the strong symmetry shown in 1996 was abnormal. Further, these observations show that the mechanism(s) which create and transport the magnetic flux are slowly changing with time and, it appears, with only loose coupling across the equator such that those asymmetries can persist for a considerable time. As the current asymmetry persists and the basal energetics of the system continue to </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22521773-magnetic-flux-transport-long-term-evolution-solar-active-regions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22521773-magnetic-flux-transport-long-term-evolution-solar-active-regions">MAGNETIC FLUX TRANSPORT AND THE LONG-TERM EVOLUTION OF SOLAR ACTIVE REGIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Ugarte-Urra, Ignacio; Upton, Lisa; Warren, Harry P. 2015-12-20 With multiple vantage points around the Sun, Solar Terrestrial Relations Observatory (STEREO) and Solar Dynamics Observatory imaging observations provide a unique opportunity to view the solar surface continuously. We use He ii 304 Å data from these observatories to isolate and track ten active regions and study their long-term evolution. We find that active regions typically follow a standard pattern of emergence over several days followed by a slower decay that is proportional in time to the peak intensity in the region. Since STEREO does not make direct observations of the magnetic field, we employ a flux-luminosity relationship to infermore » the total unsigned magnetic flux evolution. To investigate this magnetic flux decay over several rotations we use a surface flux transport model, the Advective Flux Transport model, that simulates convective flows using a time-varying velocity field and find that the model provides realistic predictions when information about the active region's magnetic field strength and distribution at peak flux is available. Finally, we illustrate how 304 Å images can be used as a proxy for magnetic flux measurements when magnetic field data is not accessible.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22661035-proposed-paradigm-solar-cycle-dynamics-mediated-via-turbulent-pumping-magnetic-flux-babcockleighton-type-solar-dynamos','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22661035-proposed-paradigm-solar-cycle-dynamics-mediated-via-turbulent-pumping-magnetic-flux-babcockleighton-type-solar-dynamos">A PROPOSED PARADIGM FOR SOLAR CYCLE DYNAMICS MEDIATED VIA TURBULENT PUMPING OF MAGNETIC FLUX IN BABCOCK–LEIGHTON-TYPE SOLAR DYNAMOS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Hazra, Soumitra; Nandy, Dibyendu At present, the Babcock–Leighton flux transport solar dynamo models appear to be the most promising models for explaining diverse observational aspects of the sunspot cycle. The success of these flux transport dynamo models is largely dependent upon a single-cell meridional circulation with a deep equatorward component at the base of the Sun’s convection zone. However, recent observations suggest that the meridional flow may in fact be very shallow (confined to the top 10% of the Sun) and more complex than previously thought. Taken together, these observations raise serious concerns on the validity of the flux transport paradigm. By accounting formore » the turbulent pumping of magnetic flux, as evidenced in magnetohydrodynamic simulations of solar convection, we demonstrate that flux transport dynamo models can generate solar-like magnetic cycles even if the meridional flow is shallow. Solar-like periodic reversals are recovered even when meridional circulation is altogether absent. However, in this case, the solar surface magnetic field dynamics does not extend all the way to the polar regions. Very importantly, our results demonstrate that the Parker–Yoshimura sign rule for dynamo wave propagation can be circumvented in Babcock–Leighton dynamo models by the latitudinal component of turbulent pumping, which can generate equatorward propagating sunspot belts in the absence of a deep, equatorward meridional flow. We also show that variations in turbulent pumping coefficients can modulate the solar cycle amplitude and periodicity. Our results suggest the viability of an alternate magnetic flux transport paradigm—mediated via turbulent pumping—for sustaining solar-stellar dynamo action.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990109131&hterms=Jason+Moore&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DJason%2BMoore','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990109131&hterms=Jason+Moore&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DJason%2BMoore">Large-Scale Coronal Heating from the Solar Magnetic Network</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Falconer, David A.; Moore, Ronald L.; Porter, Jason G.; Hathaway, David H. 1999-01-01 In Fe 12 images from SOHO/EIT, the quiet solar corona shows structure on scales ranging from sub-supergranular (i.e., bright points and coronal network) to multi- supergranular. In Falconer et al 1998 (Ap.J., 501, 386) we suppressed the large-scale background and found that the network-scale features are predominantly rooted in the magnetic network lanes at the boundaries of the supergranules. The emission of the coronal network and bright points contribute only about 5% of the entire quiet solar coronal Fe MI emission. Here we investigate the large-scale corona, the supergranular and larger-scale structure that we had previously treated as a background, and that emits 95% of the total Fe XII emission. We compare the dim and bright halves of the large- scale corona and find that the bright half is 1.5 times brighter than the dim half, has an order of magnitude greater area of bright point coverage, has three times brighter coronal network, and has about 1.5 times more magnetic flux than the dim half These results suggest that the brightness of the large-scale corona is more closely related to the large- scale total magnetic flux than to bright point activity. We conclude that in the quiet sun: (1) Magnetic flux is modulated (concentrated/diluted) on size scales larger than supergranules. (2) The large-scale enhanced magnetic flux gives an enhanced, more active, magnetic network and an increased incidence of network bright point formation. (3) The heating of the large-scale corona is dominated by more widespread, but weaker, network activity than that which heats the bright points. This work was funded by the Solar Physics Branch of NASA's office of Space Science through the SR&T Program and the SEC Guest Investigator Program. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...820L..37C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...820L..37C">Imaging a Magnetic-breakout Solar Eruption</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Yao; Du, Guohui; Zhao, Di; Wu, Zhao; Liu, Wei; Wang, Bing; Ruan, Guiping; Feng, Shiwei; Song, Hongqiang 2016-04-01 The fundamental mechanism initiating coronal mass ejections (CMEs) remains controversial. One of the leading theories is magnetic breakout, in which magnetic reconnection occurring high in the corona removes the confinement on an energized low-corona structure from the overlying magnetic field, thus allowing it to erupt. Here, we report critical observational evidence of this elusive breakout reconnection in a multi-polar magnetic configuration that leads to a CME and an X-class, long-duration flare. Its occurrence is supported by the presence of pairs of heated cusp-shaped loops around an X-type null point and signatures of reconnection inflows. Other peculiar features new to the breakout picture include sequential loop brightening, coronal hard X-rays at energies up to ˜100 keV, and extended high-corona X-rays above the later restored multi-polar structure. These observations, from a novel perspective with clarity never achieved before, present crucial clues to understanding the initiation mechanism of solar eruptions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22518569-magnetic-classification-solar-active-regions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22518569-magnetic-classification-solar-active-regions">THE MAGNETIC CLASSIFICATION OF SOLAR ACTIVE REGIONS 1992–2015</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Jaeggli, S. A.; Norton, A. A., E-mail: sarah.jaeggli@nasa.gov The purpose of this Letter is to address a blindspot in our knowledge of solar active region (AR) statistics. To the best of our knowledge, there are no published results showing the variation of the Mount Wilson magnetic classifications as a function of solar cycle based on modern observations. We show statistics for all ARs reported in the daily Solar Region Summary from 1992 January 1 to 2015 December 31. We find that the α and β class ARs (including all sub-groups, e.g., βγ, βδ) make up fractions of approximately 20% and 80% of the sample, respectively. This fraction ismore » relatively constant during high levels of activity; however, an increase in the α fraction to about 35% and and a decrease in the β fraction to about 65% can be seen near each solar minimum and are statistically significant at the 2σ level. Over 30% of all ARs observed during the years of solar maxima were appended with the classifications γ and/or δ, while these classifications account for only a fraction of a percent during the years near the solar minima. This variation in the AR types indicates that the formation of complex ARs may be due to the pileup of frequent emergence of magnetic flux during solar maximum, rather than the emergence of complex, monolithic flux structures.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH54A..02L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH54A..02L">Can Polar Fields Explain Missing Open Flux?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Linker, J.; Downs, C.; Caplan, R. M.; Riley, P.; Mikic, Z.; Lionello, R. 2017-12-01 The "open" magnetic field is the portion of the Sun's magnetic field that extends out into the heliosphere and becomes the interplanetary magnetic field (IMF). Both the IMF and the Sun's magnetic field in the photosphere have been measured for many years. In the standard paradigm of coronal structure, the open magnetic field originates primarily in coronal holes. The regions that are magnetically closed trap the coronal plasma and give rise to the streamer belt. This basic picture is qualitatively reproduced by models of coronal structure using photospheric magnetic fields as input. If this paradigm is correct, there are two primary observational constraints on the models: (1) The open field regions in the model should approximately correspond to coronal holes observed in emission, and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. Linker et al. (2017, ApJ, submitted) investigated the July 2010 time period for a range of observatory maps and both PFSS and MHD models. We found that all of the model/map combinations underestimated the interplanetary magnetic flux, unless the modeled open field regions were larger than observed coronal holes. An estimate of the open magnetic flux made entirely from solar observations (combining detected coronal hole boundaries with observatory synoptic magnetic maps) also underestimated the interplanetary magnetic flux. The magnetic field near the Sun's poles is poorly observed and may not be well represented in observatory maps. In this paper, we explore whether an underestimate of the polar magnetic flux during this time period could account for the overall underestimate of open magnetic flux. Research supported by NASA, AFOSR, and NSF. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770011613','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770011613">Studies of silicon p-n junction solar cells. [open circuit photovoltage</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Lindholm, F. A. 1976-01-01 Single crystal silicon p-n junction solar cells made with low resistivity substrates show poorer solar energy conversion efficiency than traditional theory predicts. The physical mechanisms responsible for this discrepancy are identified and characterized. The open circuit voltage in shallow junction cells of about 0.1 ohm/cm substrate resistivity is investigated under AMO (one sun) conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170011707','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170011707">Magnetic Flux Cancellation as the Trigger Mechanism of Solar Coronal Jets</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> McGlasson, Riley A.; Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L. 2017-01-01 Coronal jets are narrow eruptions in the solar corona, and are often observed in extreme ultraviolet (EUV) and X-Ray images. They occur everywhere on the solar disk: in active regions, quiet regions, and coronal holes (Raouafi et al. 2016). Recent studies indicate that most coronal jets in quiet regions and coronal holes are driven by the eruption of a minifilament (Sterling et al. 2015), and that this eruption follows flux cancellation at the magnetic neutral line under the pre-eruption minifilament (Panesar et al. 2016). We confirm this picture for a large sample of jets in quiet regions and coronal holes using multithermal extreme ultraviolet (EUV) images from the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and line-of-sight magnetograms from the SDO/Helioseismic and Magnetic Imager (HMI). We report observations of 60 randomly selected jet eruptions. We have analyzed the magnetic cause of these eruptions and measured the base size and the duration of each jet using routines in SolarSoft IDL. By examining the evolutionary changes in the magnetic field before, during, and after jet eruption, we found that each of these jets resulted from minifilament eruption triggered by flux cancellation at the neutral line. In agreement with the above studies, we found our jets to have an average base diameter of 7600 +/- 2700 km and an average jet-growth duration of 9.0 +/- 3.6 minutes. These observations confirm that minifilament eruption is the driver and that magnetic flux cancellation is the primary trigger mechanism for nearly all coronal hole and quiet region coronal jet eruptions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MmSAI..84..440S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MmSAI..84..440S">The multiscale nature of magnetic pattern on the solar surface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Scardigli, S.; Del Moro, D.; Berrilli, F. Multiscale magnetic underdense regions (voids) appear in high resolution magnetograms of quiet solar surface. These regions may be considered a signature of the underlying convective structure. The study of the associated pattern paves the way for the study of turbulent convective scales from granular to global. In order to address the question of magnetic pattern driven by turbulent convection we used a novel automatic void detection method to calculate void distributions. The absence of preferred scales of organization in the calculated distributions supports the multiscale nature of flows on the solar surface and the absence of preferred convective scales. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JGRA..110.1107G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JGRA..110.1107G">Direct evidence for magnetic reconnection in the solar wind near 1 AU</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gosling, J. T.; Skoug, R. M.; McComas, D. J.; Smith, C. W. 2005-01-01 We have obtained direct evidence for local magnetic reconnection in the solar wind using solar wind plasma and magnetic field data obtained by the Advanced Composition Explorer (ACE). The prime evidence consists of accelerated ion flow observed within magnetic field reversal regions in the solar wind. Here we report such observations obtained in the interior of an interplanetary coronal mass ejection (ICME) or at the interface between two ICMEs on 23 November 1997 at a time when the magnetic field was stronger than usual. The observed plasma acceleration was consistent with the Walen relationship, which relates changes in flow velocity to density-weighted changes in the magnetic field vector. Pairs of proton beams having comparable densities and counterstreaming relative to one another along the magnetic field at a speed of ˜1.4VA, where VA was the local Alfven speed, were observed near the center of the accelerated flow event. We infer from the observations that quasi-stationary reconnection occurred sunward of the spacecraft and that the accelerated flow occurred within a Petschek-type reconnection exhaust region bounded by Alfven waves and having a cross section width of ˜4 × 105 km as it swept over ACE. The counterstreaming ion beams resulted from solar wind plasma entering the exhaust region from opposite directions along the reconnected magnetic field lines. We have identified a limited number (five) of other accelerated flow events in the ACE data that are remarkably similar to the 23 November 1997 event. All such events identified occurred at thin current sheets associated with moderate to large changes in magnetic field orientation (98°-162°) in plasmas characterized by low proton beta (0.01-0.15) and high Alfven speed (51-204 km/s). They also were all associated with ICMEs. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120012850','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120012850">The Effect of Magnetic Topology on the Escape of Flare Particles</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Antiochos, S. K.; Masson, S.; DeVore, C. R. 2012-01-01 Magnetic reconnection in the solar atmosphere is believed to be the driver of most solar explosive phenomena. Therefore, the topology of the coronal magnetic field is central to understanding the solar drivers of space weather. Of particular importance to space weather are the impulsive Solar Energetic particles that are associated with some CME/eruptive flare events. Observationally, the magnetic configuration of active regions where solar eruptions originate appears to agree with the standard eruptive flare model. According to this model, particles accelerated at the flare reconnection site should remain trapped in the corona and the ejected plasmoid. However, flare-accelerated particles frequently reach the Earth long before the CME does. We present a model that may account for the injection of energetic particles onto open magnetic flux tubes connecting to the Earth. Our model is based on the well-known 2.5D breakout topology, which has a coronal null point (null line) and a four-flux system. A key new addition, however, is that we include an isothermal solar wind with open-flux regions. Depending on the location of the open flux with respect to the null point, we find that the flare reconnection can consist of two distinct phases. At first, the flare reconnection involves only closed field, but if the eruption occurs close to the open field, we find a second phase involving interchange reconnection between open and closed. We argue that this second reconnection episode is responsible for the injection of flare-accelerated particles into the interplanetary medium. We will report on our recent work toward understanding how flare particles escape to the heliosphere. This work uses high-resolution 2.5D MHD numerical simulations performed with the Adaptively Refined MHD Solver (ARMS). </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29563498','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29563498">The oldest magnetic record in our solar system identified using nanometric imaging and numerical modeling.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Shah, Jay; Williams, Wyn; Almeida, Trevor P; Nagy, Lesleis; Muxworthy, Adrian R; Kovács, András; Valdez-Grijalva, Miguel A; Fabian, Karl; Russell, Sara S; Genge, Matthew J; Dunin-Borkowski, Rafal E 2018-03-21 Recordings of magnetic fields, thought to be crucial to our solar system's rapid accretion, are potentially retained in unaltered nanometric low-Ni kamacite (~ metallic Fe) grains encased within dusty olivine crystals, found in the chondrules of unequilibrated chondrites. However, most of these kamacite grains are magnetically non-uniform, so their ability to retain four-billion-year-old magnetic recordings cannot be estimated by previous theories, which assume only uniform magnetization. Here, we demonstrate that non-uniformly magnetized nanometric kamacite grains are stable over solar system timescales and likely the primary carrier of remanence in dusty olivine. By performing in-situ temperature-dependent nanometric magnetic measurements using off-axis electron holography, we demonstrate the thermal stability of multi-vortex kamacite grains from the chondritic Bishunpur meteorite. Combined with numerical micromagnetic modeling, we determine the stability of the magnetization of these grains. Our study shows that dusty olivine kamacite grains are capable of retaining magnetic recordings from the accreting solar system. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ARep...62..359F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ARep...62..359F">Two Scenarios for the Eruption of Magnetic Flux Ropes in the Solar Atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Filippov, B. P.; Den, O. E. 2018-05-01 Eruptions of material from lower to upper layers of the solar atmosphere can be divided into two classes. The first class of eruptions maintain their (usually loop-like) shapes as they increase in size (eruptive prominences), or display a sudden expansion of fairly shapeless clumps of plasma in all directions (flare sprays). The second class refers to narrow, collimated flows of plasma on various scales (spicules, surges, jets). It is obvious that the magnetic configurations in which these phenomena develop differ: for the first class they form closed structures that confine the plasma, and in the second class open structures directing flows of plasma in a particular direction, as a rule, upward. At the same time, the mechanisms initiating eruptions of both classes could be similar, or even practically identical. This mechanism could be instability of twisted magnetic tubes (flux ropes), leading to different consequences under different conditions. It is shown that the results of eruptive instability are determined by the ratio of the scales of the magnetic flux rope and the confining coronal field, and also by the configuration of the ambient magnetic field in the corona. Observations of both types of eruptions are analyzed, the conditions for their develoment are examined, and phenomenological models are proposed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH23D2686M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH23D2686M">3D Visualization of Solar Data: Preparing for Solar Orbiter and Parker Solar Probe</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mueller, D.; Nicula, B.; Felix, S.; Verstringe, F.; Bourgoignie, B.; Csillaghy, A.; Berghmans, D.; Jiggens, P.; Ireland, J.; Fleck, B. 2017-12-01 Solar Orbiter and Parker Solar Probe will focus on exploring the linkage between the Sun and the heliosphere. These new missions will collect unique data that will allow us to study, e.g., the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere and the origin and acceleration of solar wind plasma. Combined with the several petabytes of data from NASA's Solar Dynamics Observatory, the scientific community will soon have access to multidimensional remote-sensing and complex in-situ observations from different vantage points, complemented by petabytes of simulation data. Answering overarching science questions like "How do solar transients drive heliospheric variability and space weather?" will only be possible if the community has the necessary tools at hand. In this contribution, we will present recent progress in visualizing the Sun and its magnetic field in 3D using the open-source JHelioviewer framework, which is part of the ESA/NASA Helioviewer Project. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH11B2453R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH11B2453R">Global solar magetic field organization in the extended corona: influence on the solar wind speed and density over the cycle.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Réville, V.; Velli, M.; Brun, S. 2017-12-01 The dynamics of the solar wind depends intrinsically on the structure of the global solar magnetic field, which undergoes fundamental changes over the 11yr solar cycle. For instance, the wind terminal velocity is thought to be anti-correlated with the expansion factor, a measure of how the magnetic field varies with height in the solar corona, usually computed at a fixed height (≈ 2.5 Rȯ, the source surface radius which approximates the distance at which all magnetic field lines become open). However, the magnetic field expansion affects the solar wind in a more detailed way, its influence on the solar wind properties remaining significant well beyond the source surface: we demonstrate this using 3D global MHD simulations of the solar corona, constrained by surface magnetograms over half a solar cycle (1989-2001). For models to comply with the constraints provided by observed characteristics of the solar wind, namely, that the radial magnetic field intensity becomes latitude independent at some distance from the Sun (Ulysses observations beyond 1 AU), and that the terminal wind speed is anti-correlated with the mass flux, they must accurately describe expansion beyond the solar wind critical point (even up to 10Rȯ and higher in our model). We also show that near activity minimum, expansion in the higher corona beyond 2.5 Rȯ is actually the dominant process affecting the wind speed. We discuss the consequences of this result on the necessary acceleration profile of the solar wind, the location of the sonic point and of the energy deposition by Alfvén waves. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100015562&hterms=Total+Care&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTotal%2BCare','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100015562&hterms=Total+Care&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTotal%2BCare">Estimating Total Heliospheric Magnetic Flux from Single-Point in Situ Measurements</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Owens, M. J.; Arge, C. N.; Crooker, N. U.; Schwardron, N. A.; Horbury, T. S. 2008-01-01 A fraction of the total photospheric magnetic flux opens to the heliosphere to form the interplanetary magnetic field carried by the solar wind. While this open flux is critical to our understanding of the generation and evolution of the solar magnetic field, direct measurements are generally limited to single-point measurements taken in situ by heliospheric spacecraft. An observed latitude invariance in the radial component of the magnetic field suggests that extrapolation from such single-point measurements to total heliospheric magnetic flux is possible. In this study we test this assumption using estimates of total heliospheric flux from well-separated heliospheric spacecraft and conclude that single-point measurements are indeed adequate proxies for the total heliospheric magnetic flux, though care must be taken when comparing flux estimates from data collected at different heliocentric distances. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22660897-rotation-solar-photospheric-magnetic-field','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22660897-rotation-solar-photospheric-magnetic-field">THE ROTATION OF THE SOLAR PHOTOSPHERIC MAGNETIC FIELD</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Xu, J. C.; Gao, P. X., E-mail: jcxu@ynao.ac.cn 2016-12-20 The rotational characteristics of the solar photospheric magnetic field at four flux ranges are investigated together with the total flux of active regions (MF{sub ar}) and quiet regions (MF{sub qr}). The first four ranges (MF{sub 1–4}) are (1.5–2.9) × 10{sup 18}, (2.9–32.0) × 10{sup 18}, (3.20–4.27) × 10{sup 19}, and (4.27–38.01) × 10{sup 19}, respectively (the unit is Mx per element). Daily values of the flux data are extracted from magnetograms of the Michelson Doppler Imager on board the Solar and Heliospheric Observatory . Lomb–Scargle periodograms show that only MF{sub 2}, MF{sub 4}, MF{sub qr}, and MF{sub ar} exhibit rotational periods. The periods of the first three typesmore » of flux are very similar, i.e., 26.20, 26.23, and 26.24 days, respectively, while that of MF{sub ar} is longer, 26.66 days. This indicates that active regions rotate more slowly than quiet regions on average, and strong magnetic fields tend to repress the surface rotation. Sinusoidal function fittings and cross-correlation analyses reveal that MF{sub ar} leads MF{sub 2} and MF{sub 4} by 5 and 1 days, respectively. This is speculated to be related with the decaying of active regions. MF{sub 2} and MF{sub ar} are negatively correlated, while both MF{sub 4} and MF{sub qr} are positively correlated with MF{sub ar}. At the timescale of the solar activity cycle, MF{sub ar} leads (negatively) MF{sub 2} by around one year (350 days), and leads MF{sub 4} by about 3 rotation periods (82 days). The relation between MF{sub 2} and MF{sub ar} may be explained by the possibility that the former mainly comes from a higher latitude, or emerges from the subsurface shear layer. We conjecture that MF{sub 4} may partly come from the magnetic flux of active regions; this verifies previous results that were obtained with indirect solar magnetic indices.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ascl.soft05005M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ascl.soft05005M">3DCORE: Forward modeling of solar storm magnetic flux ropes for space weather prediction</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Möstl, C.; Amerstorfer, T.; Palmerio, E.; Isavnin, A.; Farrugia, C. J.; Lowder, C.; Winslow, R. M.; Donnerer, J. M.; Kilpua, E. K. J.; Boakes, P. D. 2018-05-01 3DCORE forward models solar storm magnetic flux ropes called 3-Dimensional Coronal Rope Ejection (3DCORE). The code is able to produce synthetic in situ observations of the magnetic cores of solar coronal mass ejections sweeping over planets and spacecraft. Near Earth, these data are taken currently by the Wind, ACE and DSCOVR spacecraft. Other suitable spacecraft making these kind of observations carrying magnetometers in the solar wind were MESSENGER, Venus Express, MAVEN, and even Helios. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004cosp...35.2435S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004cosp...35.2435S">Solar Spicules: Prospects for Breakthroughs in Understanding with Solar-B</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sterling, A. Spicules densely populate the lower solar atmosphere; any image or movie of the chromosphere shows a plethora of them or their "cousins," such as mottles or fibrils. Yet despite several decades of effort we still do not know the mechanism that generates them, or how important their contribution is to the material and energy balance of the overall solar atmosphere. Solar-B will provide exciting new chromospheric observations at high time- and spatial-resolution, along with associated quality magnetic field data, that promise to open doors to revolutionary breakthroughs in spicule research. In this presentation we will review the current observational and theoretical status of spicule studies, and discuss prospects for advances in spicule understanding during the Solar-B era. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040086091&hterms=Solar+still&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DSolar%2Bstill','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040086091&hterms=Solar+still&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DSolar%2Bstill">Solar Spicules: Prospects for Breakthroughs in Understanding with Solar-B</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Sterling, A. C. 2004-01-01 Spicules densely populate the lower solar atmosphere; any image or movie of the chromosphere shows a plethora of them or their "cousins," such as mottles or fibrils. Yet despite several decades of effort we still do not know the mechanism that generates them, or how important their contribution is to the material and energy balance of the overall solar atmosphere. Solar-B will provide exciting new chromospheric observations at high time- and spatial-resolution, along with associated quality magnetic field data, that promise to open doors to revolutionary breakthroughs in spicule research. In this presentation we will review the current observational and theoretical status of spicule studies, and discuss prospects for advances in spicule understanding during the Solar-B era. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22522342-magnetic-untwisting-solar-jets-go-outer-corona-polar-coronal-holes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22522342-magnetic-untwisting-solar-jets-go-outer-corona-polar-coronal-holes">MAGNETIC UNTWISTING IN SOLAR JETS THAT GO INTO THE OUTER CORONA IN POLAR CORONAL HOLES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David A., E-mail: ron.moore@nasa.gov We study 14 large solar jets observed in polar coronal holes. In EUV movies from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA), each jet appears similar to most X-ray jets and EUV jets that erupt in coronal holes; but each is exceptional in that it goes higher than most, so high that it is observed in the outer corona beyond 2.2 R{sub Sun} in images from the Solar and Heliospheric Observatory/Large Angle Spectroscopic Coronagraph (LASCO)/C2 coronagraph. From AIA He ii 304 Å movies and LASCO/C2 running-difference images of these high-reaching jets, we find: (1) the front of the jet transitsmore » the corona below 2.2 R{sub Sun} at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most of the jets display measureable swaying and bending of a few degrees in amplitude; in three jets the swaying is discernibly oscillatory with a period of order 1 hr. These characteristics suggest that the driver in these jets is a magnetic-untwisting wave that is basically a large-amplitude (i.e., nonlinear) torsional Alfvén wave that is put into the reconnected open field in the jet by interchange reconnection as the jet erupts. From the measured spinning and swaying, we estimate that the magnetic-untwisting wave loses most of its energy in the inner corona below 2.2 R{sub Sun}. We point out that the torsional waves observed in Type-II spicules might dissipate in the corona in the same way as the magnetic-untwisting waves in our big jets, and thereby power much of the coronal heating in coronal holes.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH31B2406L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH31B2406L">Origin of the High-speed Jets Fom Magnetic Flux Emergence in the Solar Transition Region as well as Their Mass and Energy Contribuctions to the Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Liping, Y.; He, J.; Peter, H.; Tu, C. Y.; Feng, X. S. 2015-12-01 In the solar atmosphere, the jets are ubiquitous and found to be at various spatia-temporal scales. They are significant to understand energy and mass transport in the solar atmosphere. Recently, the high-speed transition region jets are reported from the observation. Here we conduct a numerical simulation to investigate the mechanism in their formation, as well as their mass and energy contributions to the solar wind. Driven by the supergranular convection motion, the magnetic reconnection between the magnetic loop and the background open flux occurring in the transition region is simulated with a two-dimensional MHD model. The simulation results show that not only a fast hot jet, much resemble the found transition region jets, but also a adjacent slow cool jet, mostly like classical spicules, is launched. The force analysis shows that the fast hot jet is continually driven by the Lorentz force around the reconnection region, while the slow cool jet is induced by an initial kick through the Lorentz force associated with the emerging magnetic flux. Also, the features of the driven jets change with the amount of the emerging magnetic flux, giving the varieties of both jets.With the developed one-dimensional hydrodynamic solar wind model, the time-dependent pulses are imposed at the bottom to simulate the jet behaviors. The simulation results show that without other energy source, the injected plasmas are accelerated effectively to be a transonic wind with a substantial mass flux. The rapid acceleration occurs close to the Sun, and the resulting asymptotic speeds, number density at 0.3 AU, as well as mass flux normalized to 1 AU are compatible with in site observations. As a result of the high speed, the imposed pulses lead to a train of shocks traveling upward. By tracing the motions of the injected plasma, it is found that these shocks heat and accelerate the injected plasma to make part of them propagate upward and eventually escape. The parametric study shows </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780025047&hterms=heinemann&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dheinemann','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780025047&hterms=heinemann&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dheinemann">The solar probe and coronal dynamics</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Belcher, J.; Heinemann, M.; Goodrich, C. 1978-01-01 The discovery of coronal holes led to basic changes in ideas about the structure of the low corona and its expansion into the solar wind. The nature of the energy flux is not understood. Current ideas include enhanced thermal conductivities, extended MHD wave heating, and wave momentum transfer, all in rapidly diverging geometries. There is little feel for the relative importance of these processes. The Solar Probe, with its penetration deep into the solar corona, could lead to observational constraints on their relative importance, and thus to an understanding of the origin of the solar wind. Observations from the Solar Probe will also bear on such questions as to whether small scale "intrastream" structure is common close to the Sun in open field-line regions, whether the properties of the wind are pronouncedly different over closed and open field-line regions at five solar radii, and many others. The resolution of these questions requires measurements of the magnetic field and of the proton and electron distribution functions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhDT.........1U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhDT.........1U">Brightness and magnetic evolution of solar coronal bright points</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ugarte-Urra, I. 2004-12-01 This thesis presents a study of the brightness and magnetic evolution of several Extreme ultraviolet (EUV) coronal bright points (hereafter BPs). BPs are loop-like features of enhanced emission in the coronal EUV and X-ray images of the Sun, that are associated to the interaction of opposite photospheric magnetic polarities with magnetic fluxes of ≈1018 - 1019 Mx. The study was carried out using several instruments on board the Solar and Heliospheric Observatory (SOHO): the Extreme Ultraviolet Imager (EIT), the Coronal Diagnostic Spectrometer (CDS) and the Michelson Doppler Imager (MDI), supported by the high resolution imaging from the Transition Region And Coronal Explorer (TRACE). The results confirm that, down to 1'' (i.e. ~715 km) resolution, BPs are made of small loops with lengths of ~6 Mm and cross-sections of ~2 Mm. The loops are very dynamic, evolving in time scales as short as 1 - 2 minutes. This is reflected in a highly variable EUV response with fluctuations highly correlated in spectral lines at transition region temperatures (in the range 3.2x10^4 - 3.5x10^5 K), but not always at coronal temperatures. A wavelet analysis of the intensity variations reveals, for the first time, the existence of quasi-periodic oscillations with periods ranging 400 -- 1000 s, in the range of periods characteristic of the chromospheric network. The link between BPs and network bright points is discussed, as well as the interpretation of the oscillations in terms of global acoustic modes of closed magnetic structures. A comparison of the magnetic flux evolution of the magnetic polarities to the EUV flux changes is also presented. Throughout their lifetime, the intrinsic EUV emission of BPs is found to be dependent on the total magnetic flux of the polarities. In short time scales, co-spatial and co-temporal TRACE and MDI images, reveal the signature of heating events that produce sudden EUV brightenings simultaneous to magnetic flux cancellations. This is interpreted in </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080030287&hterms=physical+activity+importance&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dphysical%2Bactivity%2Bimportance','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080030287&hterms=physical+activity+importance&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dphysical%2Bactivity%2Bimportance">Magnetic Reconfiguration in Explosive Solar Activity</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Antiochos, Spiro K. 2008-01-01 A fundamental property of the Sun's corona i s that it is violently dynamic. The most spectacular and most energetic manifestations of this activity are the giant disruptions that give rise to coronal mass ejections (CME) and eruptive flares. These major events are of critical importance, because they drive the most destructive forms of space weather at Earth and in the solar system, and they provide a unique opportunity to study, in revealing detail, the interaction of magnetic field and matter, in particular, magnetohydrodynamic instability and nonequilibrium -- processes that are at the heart of laboratory and astrophysical plasma physics. Recent observations by a number of NASA space missions have given us new insights into the physical mechanisms that underlie coronal explosions. Furthermore, massively-parallel computation have now allowed us to calculate fully three-dimensional models for solar activity. In this talk I will present some of the latest observations of the Sun, including those from the just-launched Hinode and STEREO mission, and discuss recent advances in the theory and modeling of explosive solar activity. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AAS...22440803M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AAS...22440803M">Magnetic Untwisting in Jets that Go into the Outer Solar Corona in Polar Coronal Holes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David 2014-06-01 We present results from a study of 14 jets that were observed in SDO/AIA EUV movies to erupt in the Sun’s polar coronal holes. These jets were similar to the many other jets that erupt in coronal holes, but reached higher than the vast majority, high enough to be observed in the outer corona beyond 2 solar radii from Sun center by the SOHO/LASCO/C2 coronagraph. We illustrate the characteristic structure and motion of these high-reaching jets by showing observations of two representative jets. We find that (1) the speed of the jet front from the base of the corona out to 2-3 solar radii is typically several times the sound speed in jets in coronal holes, (2) each high-reaching jet displays unusually large rotation about its axis (spin) as it erupts, and (3) in the outer corona, many jets display lateral swaying and bending of the jet axis with an amplitude of a few degrees and a period of order 1 hour. From these observations we infer that these jets are magnetically driven, propose that the driver is a magnetic-untwisting wave that is basically a large-amplitude (non-linear) torsional Alfven wave that is put into the open magnetic field in the jet by interchange reconnection as the jet erupts, and estimate that the magnetic-untwisting wave loses most of its energy before reaching the outer corona. These observations of high-reaching coronal jets suggest that the torsional magnetic waves observed in Type-II spicules can similarly dissipate in the corona and thereby power much of the coronal heating in coronal holes and quiet regions. This work is funded by the NASA/SMD Heliophysics Division’s Living With a Star Targeted Research & Technology Program. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH41B2763L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH41B2763L">Large-scale particle acceleration by magnetic reconnection during solar flares</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, X.; Guo, F.; Li, H.; Li, G.; Li, S. 2017-12-01 Magnetic reconnection that triggers explosive magnetic energy release has been widely invoked to explain the large-scale particle acceleration during solar flares. While great efforts have been spent in studying the acceleration mechanism in small-scale kinetic simulations, there have been rare studies that make predictions to acceleration in the large scale comparable to the flare reconnection region. Here we present a new arrangement to study this problem. We solve the large-scale energetic-particle transport equation in the fluid velocity and magnetic fields from high-Lundquist-number MHD simulations of reconnection layers. This approach is based on examining the dominant acceleration mechanism and pitch-angle scattering in kinetic simulations. Due to the fluid compression in reconnection outflows and merging magnetic islands, particles are accelerated to high energies and develop power-law energy distributions. We find that the acceleration efficiency and power-law index depend critically on upstream plasma beta and the magnitude of guide field (the magnetic field component perpendicular to the reconnecting component) as they influence the compressibility of the reconnection layer. We also find that the accelerated high-energy particles are mostly concentrated in large magnetic islands, making the islands a source of energetic particles and high-energy emissions. These findings may provide explanations for acceleration process in large-scale magnetic reconnection during solar flares and the temporal and spatial emission properties observed in different flare events. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JASS...28..123M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JASS...28..123M">Variation of Magnetic Field (By , Bz) Polarity and Statistical Analysis of Solar Wind Parameters during the Magnetic Storm Period</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Moon, Ga-Hee 2011-06-01 It is generally believed that the occurrence of a magnetic storm depends upon the solar wind conditions, particularly the southward interplanetary magnetic field (IMF) component. To understand the relationship between solar wind parameters and magnetic storms, variations in magnetic field polarity and solar wind parameters during magnetic storms are examined. A total of 156 storms during the period of 1997~2003 are used. According to the interplanetary driver, magnetic storms are divided into three types, which are coronal mass ejection (CME)-driven storms, co-rotating interaction region (CIR)-driven storms, and complicated type storms. Complicated types were not included in this study. For this purpose, the manner in which the direction change of IMF By and Bz components (in geocentric solar magnetospheric coordinate system coordinate) during the main phase is related with the development of the storm is examined. The time-integrated solar wind parameters are compared with the time-integrated disturbance storm time (Dst) index during the main phase of each magnetic storm. The time lag with the storm size is also investigated. Some results are worth noting: CME-driven storms, under steady conditions of Bz < 0, represent more than half of the storms in number. That is, it is found that the average number of storms for negative sign of IMF Bz (T1~T4) is high, at 56.4%, 53.0%, and 63.7% in each storm category, respectively. However, for the CIR-driven storms, the percentage of moderate storms is only 29.2%, while the number of intense storms is more than half (60.0%) under the Bz < 0 condition. It is found that the correlation is highest between the time-integrated IMF Bz and the time-integrated Dst index for the CME-driven storms. On the other hand, for the CIR-driven storms, a high correlation is found, with the correlation coefficient being 0.93, between time-integrated Dst index and time-integrated solar wind speed, while a low correlation, 0.51, is found between </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH33B2770B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH33B2770B">Anisotropic Behaviour of Magnetic Power Spectra in Solar Wind Turbulence.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Banerjee, S.; Saur, J.; Gerick, F.; von Papen, M. 2017-12-01 Introduction:High altitude fast solar wind turbulence (SWT) shows different spectral properties as a function of the angle between the flow direction and the scale dependent mean magnetic field (Horbury et al., PRL, 2008). The average magnetic power contained in the near perpendicular direction (80º-90º) was found to be approximately 5 times larger than the average power in the parallel direction (0º- 10º). In addition, the parallel power spectra was found to give a steeper (-2) power law than the perpendicular power spectral density (PSD) which followed a near Kolmogorov slope (-5/3). Similar anisotropic behaviour has also been observed (Chen et al., MNRAS, 2011) for slow solar wind (SSW), but using a different method exploiting multi-spacecraft data of Cluster. Purpose:In the current study, using Ulysses data, we investigate (i) the anisotropic behaviour of near ecliptic slow solar wind using the same methodology (described below) as that of Horbury et al. (2008) and (ii) the dependence of the anisotropic behaviour of SWT as a function of the heliospheric latitude.Method:We apply the wavelet method to calculate the turbulent power spectra of the magnetic field fluctuations parallel and perpendicular to the local mean magnetic field (LMF). According to Horbury et al., LMF for a given scale (or size) is obtained using an envelope of the envelope of that size. Results:(i) SSW intervals always show near -5/3 perpendicular spectra. Unlike the fast solar wind (FSW) intervals, for SSW, we often find intervals where power parallel to the mean field is not observed. For a few intervals with sufficient power in parallel direction, slow wind turbulence also exhibit -2 parallel spectra similar to FSW.(ii) The behaviours of parallel and perpendicular power spectra are found to be independent of the heliospheric latitude. Conclusion:In the current study we do not find significant influence of the heliospheric latitude on the spectral slopes of parallel and perpendicular </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.5899S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.5899S">Magnetic moment of solar plasma and the Kelvin force: -The driving force of plasma up-flow -</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shibasaki, Kiyoto 2017-04-01 Thermal plasma in the solar atmosphere is magnetized (diamagnetic). The magnetic moment does not disappear by collisions because complete gyration is not a necessary condition to have magnetic moment. Magnetized fluid is subjected to Kelvin force in non-uniform magnetic field. Generally, magnetic field strength decreases upwards in the solar atmosphere, hence the Kelvin force is directed upwards along the field. This force is not included in the fluid treatment of MHD. By adding the Kelvin force to the MHD equation of motion, we can expect temperature dependent plasma flows along the field which are reported by many observations. The temperature dependence of the flow speed is explained by temperature dependence of magnetic moment. From the observed parameters, we can infer physical parameters in the solar atmosphere such as scale length of the magnetic field strength and the friction force acting on the flowing plasma. In case of closed magnetic field lines, loop-top concentration of hot plasma is expected which is frequently observed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060041678&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060041678&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS">Distant Tail Behavior During High Speed Solar Wind Streams and Magnetic Storms</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ho, C. M.; Tsurutani, B. T. 1997-01-01 We have examined the ISEE 3 distant tail data during three intense magnetic storms and have identified the tail response to high-speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH13A2464M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH13A2464M">The Evolution of the Solar Magnetic Field: A Comparative Analysis of Two Models</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McMichael, K. D.; Karak, B. B.; Upton, L.; Miesch, M. S.; Vierkens, O. 2017-12-01 Understanding the complexity of the solar magnetic cycle is a task that has plagued scientists for decades. However, with the help of computer simulations, we have begun to gain more insight into possible solutions to the plethora of questions inside the Sun. STABLE (Surface Transport and Babcock Leighton) is a newly developed 3D dynamo model that can reproduce features of the solar cycle. In this model, the tilted bipolar sunspots are formed on the surface (based on the toroidal field at the bottom of the convection zone) and then decay and disperse, producing the poloidal field. Since STABLE is a 3D model, it is able to solve the full induction equation in the entirety of the solar convection zone as well as incorporate many free parameters (such as spot depth and turbulent diffusion) which are difficult to observe. In an attempt to constrain some of these free parameters, we compare STABLE to a surface flux transport model called AFT (Advective Flux Transport) which solves the radial component of the magnetic field on the solar surface. AFT is a state-of-the-art surface flux transport model that has a proven record of being able to reproduce solar observations with great accuracy. In this project, we implement synthetic bipolar sunspots into both models, using identical surface parameters, and run the models for comparison. We demonstrate that the 3D structure of the sunspots in the interior and the vertical diffusion of the sunspot magnetic field play an important role in establishing the surface magnetic field in STABLE. We found that when a sufficient amount of downward magnetic pumping is included in STABLE, the surface magnetic field from this model becomes insensitive to the internal structure of the sunspot and more consistent with that of AFT. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012decs.confE..86M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012decs.confE..86M">Observational Evidence of Magnetic Waves in the Solar Atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McIntosh, Scott W. 2012-03-01 The observational evidence in supporting the presence of magnetic waves in the outer solar atmosphere is growing rapidly - we will discuss recent observations and place them in context with salient observations made in the past. While the clear delineation of these magnetic wave "modes" is unclear, much can be learned about the environment in which they originated and possibly how they are removed from the system from the observations. Their diagnostic power is, as yet, untapped and their energy content (both as a mechanical source for the heating of coronal material and acceleration of the solar wind) remains in question, but can be probed observationally - raising challenges for modeling efforts. We look forward to the IRIS mission by proposing some sample observing sequences to help resolve some of the zoological issues present in the literature. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EPSC....8..772I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EPSC....8..772I">Solar Cycle variations in Earth's open flux content measured by the SuperDARN radar network</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Imber, S. M.; Milan, S. E.; Lester, M. 2013-09-01 We present a long term study, from 1996 - 2012, of the latitude of the Heppner-Maynard Boundary (HMB) determined using the northern hemisphere SuperDARN radars. The HMB represents the equatorward extent of ionospheric convection and is here used as a proxy for the amount of open flux in the polar cap. The mean HMB latitude (measured at midnight) is found to be at 64 degrees during the entire period, with secondary peaks at lower latitudes during the solar maximum of 2003, and at higher latitudes during the recent extreme solar minimum of 2008-2011. We associate these large scale statistical variations in open flux content with solar cycle variations in the solar wind parameters leading to changes in the intensity of the coupling between the solar wind and the magnetosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22365035-polar-network-index-magnetic-proxy-solar-cycle-studies','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22365035-polar-network-index-magnetic-proxy-solar-cycle-studies">POLAR NETWORK INDEX AS A MAGNETIC PROXY FOR THE SOLAR CYCLE STUDIES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Priyal, Muthu; Banerjee, Dipankar; Ravindra, B. 2014-09-20 The Sun has a polar magnetic field which oscillates with the 11 yr sunspot cycle. This polar magnetic field is an important component of the dynamo process which operates in the solar convection zone and produces the sunspot cycle. We have direct systematic measurements of the Sun's polar magnetic field only from about the mid-1970s. There are, however, indirect proxies which give us information about this field at earlier times. The Ca-K spectroheliograms taken at the Kodaikanal Solar Observatory during 1904-2007 have now been digitized with 4k × 4k CCD and have higher resolution (∼0.86 arcsec) than the other available historical datamore » sets. From these Ca-K spectroheliograms, we have developed a completely new proxy (polar network index, hereafter PNI) for the Sun's polar magnetic field. We calculate PNI from the digitized images using an automated algorithm and calibrate our measured PNI against the polar field as measured by the Wilcox Solar Observatory for the period 1976-1990. This calibration allows us to estimate the polar fields for the earlier period up to 1904. The dynamo calculations performed with this proxy as input data reproduce reasonably well the Sun's magnetic behavior for the past century.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM52C..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM52C..07C">Calculating Coronal Mass Ejection Magnetic Field at 1 AU Using Solar Observables</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, J.; Kunkel, V. 2013-12-01 It is well-established that most major nonrecurrent geomagnetic storms are caused by solar wind structures with long durations of strong southward (Bz < 0) interplanetary magnetic field (IMF). Such geoeffective IMF structures are associated with CME events at the Sun. Unfortunately, neither the duration nor the internal magnetic field vector of the ejecta--the key determinants of geoeffectiveness--is measurable until the observer (e.g., Earth) passes through the ejecta. In this paper, we discuss the quantitative relationships between the ejecta magnetic field at 1 AU and remotely observable solar quantities associated with the eruption of a given CME. In particular, we show that observed CME trajectories (position-time data) within, say, 1/3 AU of the Sun, contain sufficient information to allow the calculation of the ejecta magnetic field (magnitude and components) at 1 AU using the Erupting Flux Rope (EFR) model of CMEs. Furthermore, in order to accurately determine the size and arrival time of the ejecta as seen by a fixed observer at 1 AU (e.g., ACE), it is essential to accurately calculate the three-dimensional geometry of the underlying magnetic structure. Accordingly, we have extended the physics-based EFR model to include a self-consistent calculation of the transverse expansion taking into account the non-symmetric drag coupling between an expanding CME flux rope and the ambient solar wind. The dependence of the minor radius of the flux rope at 1 AU that determines the perceived size of the ejecta on solar quantities is discussed. Work supported by the NRL Base Program. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4820006M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4820006M">Onset of the Magnetic Explosion in Solar Polar Coronal X-Ray Jets</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Moore, Ronald L.; Sterling, Alphonse C.; Panesar, Navdeep 2017-08-01 We examine the onset of the driving magnetic explosion in 15 random polar coronal X-ray jets. Each eruption is observed in a coronal X-ray movie from Hinode and in a coronal EUV movie from Solar Dynamics Observatory. Contrary to the Sterling et al (2015, Nature, 523, 437) scenario for minifilament eruptions that drive polar coronal jets, these observations indicate: (1) in most polar coronal jets (a) the runaway internal tether-cutting reconnection under the erupting minifilament flux rope starts after the spire-producing breakout reconnection starts, not before it, and (b) aleady at eruption onset, there is a current sheet between the explosive closed magnetic field and ambient open field; and (2) the minifilament-eruption magnetic explosion often starts with the breakout reconnection of the outside of the magnetic arcade that carries the minifilament in its core. On the other hand, the diversity of the observed sequences of occurrence of events in the jet eruptions gives further credence to the Sterlling et al (2015, Nature, 523, 437) idea that the magnetic explosions that make a polar X-ray jet work the same way as the much larger magnetic explosions that make and flare and CME. We point out that this idea, and recent observations indicating that magnetic flux cancelation is the fundamental process that builds the field in and around pre-jet minifilaments and triggers the jet-driving magnetic explosion, together imply that usually flux cancelation inside the arcade that explodes in a flare/CME eruption is the fundamental process that builds the explosive field and triggers the explosion.This work was funded by the Heliophysics Division of NASA's Science Mission Directorate through its Living With a Star Targeted Research and Technology Program, its Heliophsyics Guest Investigators Program, and the Hinode Project. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880053447&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DMagnetic%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880053447&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DMagnetic%2Benergy">Transport equations for low-energy solar particles in evolving interplanetary magnetic fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ng, C. K. 1988-01-01 Two new forms of a simplified Fokker-Planck equation are derived for the transport of low-energy solar energetic particles in an evolving interplanetary magnetic field, carried by a variable radial solar wind. An idealized solution suggests that the 'invariant' anisotropy direction reported by Allum et al. (1974) may be explained within the conventional theoretical framework. The equations may be used to relate studies of solar particle propagation to solar wind transients, and vice versa. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110016219&hterms=open+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dopen%2Bsource','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110016219&hterms=open+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dopen%2Bsource">A Model fot the Sources of the Slow Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Antiochos, S. K.; Mikic, Z.; Titov, V. S.; Lionello, R.; Linker, J. A. 2011-01-01 Models for the origin of the slow solar wind must account for two seemingly contradictory observations: the slow wind has the composition of the closed-field corona, implying that it originates from the continuous opening and closing of flux at the boundary between open and closed field. On the other hand, the slow wind also has large angular width, up to approx.60deg, suggesting that its source extends far from the open-closed boundary. We propose a model that can explain both observations. The key idea is that the source of the slow wind at the Sun is a network of narrow (possibly singular) open-field corridors that map to a web of separatrices and quasi-separatrix layers in the heliosphere. We compute analytically the topology of an open-field corridor and show that it produces a quasi-separatrix layer in the heliosphere that extends to angles far from the heliospheric current sheet. We then use an MHD code and MDI/SOHO observations of the photospheric magnetic field to calculate numerically, with high spatial resolution, the quasi-steady solar wind, and magnetic field for a time period preceding the 2008 August 1 total solar eclipse. Our numerical results imply that, at least for this time period, a web of separatrices (which we term an S-web) forms with sufficient density and extent in the heliosphere to account for the observed properties of the slow wind. We discuss the implications of our S-web model for the structure and dynamics of the corona and heliosphere and propose further tests of the model. Key words: solar wind - Sun: corona - Sun: magnetic topology </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004ApJ...612L..81C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004ApJ...612L..81C">Recycling of the Solar Corona's Magnetic Field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Close, R. M.; Parnell, C. E.; Longcope, D. W.; Priest, E. R. 2004-09-01 Magnetic fields play a dominant role in the atmospheres of the Sun and other Sun-like stars. Outside sunspot regions, the photosphere of the so-called quiet Sun contains myriads of small-scale magnetic concentrations, with strengths ranging from the detection limit of ~1016 Mx up to ~3×1020 Mx. The tireless motion of these magnetic flux concentrations, along with the continual appearance and disappearance of opposite-polarity pairs of fluxes, releases a substantial amount of energy that may be associated with a whole host of physical processes in the solar corona, not least the enigma of coronal heating. We find here that the timescale for magnetic flux to be remapped in the quiet-Sun corona is, surprisingly, only 1.4 hr (around 1/10 of the photospheric flux recycling time), implying that the quiet-Sun corona is far more dynamic than previously thought. Besides leading to a fuller understanding of the origins of magnetically driven phenomena in our Sun's corona, such a process may also be crucial for the understanding of stellar atmospheres in general. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880043939&hterms=soup&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsoup','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880043939&hterms=soup&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsoup">On the relation between photospheric flow fields and the magnetic field distribution on the solar surface</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Simon, George W.; Title, A. M.; Topka, K. P.; Tarbell, T. D.; Shine, R. A. 1988-01-01 Using the technique of local correlation tracking on a 28 minute time sequence of white-light images of solar granulation, the horizontal flow field on the solar surface is measured. The time series was obtained by the Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 (Space Shuttle flight 51-F) and is free from atmospheric blurring and distortion. The SOUP flow fields have been compared with carefully aligned magnetograms taken over a nine hour period at the Big Bear Solar Observatory before, during, and after the SOUP images. The flow field and the magnetic field agree in considerable detail: vectors which define the flow of the white-light intensity pattern (granulation) point toward magnetic field regions, magnetic fields surround flow cells, and magnetic features move along the flow arrows. The projected locations of free particles ('corks') in the measured flow field congregate at the same locations where the magnetic field is observed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ScChE..60.1383C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ScChE..60.1383C">Origin and Structures of Solar Eruptions I: Magnetic Flux Rope</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cheng, Xin; Guo, Yang; Ding, MingDe 2017-08-01 Coronal mass ejections (CMEs) and solar flares are the large-scale and most energetic eruptive phenomena in our solar system and able to release a large quantity of plasma and magnetic flux from the solar atmosphere into the solar wind. When these high-speed magnetized plasmas along with the energetic particles arrive at the Earth, they may interact with the magnetosphere and ionosphere, and seriously affect the safety of human high-tech activities in outer space. The travel time of a CME to 1 AU is about 1-3 days, while energetic particles from the eruptions arrive even earlier. An efficient forecast of these phenomena therefore requires a clear detection of CMEs/flares at the stage as early as possible. To estimate the possibility of an eruption leading to a CME/flare, we need to elucidate some fundamental but elusive processes including in particular the origin and structures of CMEs/flares. Understanding these processes can not only improve the prediction of the occurrence of CMEs/flares and their effects on geospace and the heliosphere but also help understand the mass ejections and flares on other solar-type stars. The main purpose of this review is to address the origin and early structures of CMEs/flares, from multi-wavelength observational perspective. First of all, we start with the ongoing debate of whether the pre-eruptive configuration, i.e., a helical magnetic flux rope (MFR), of CMEs/flares exists before the eruption and then emphatically introduce observational manifestations of the MFR. Secondly, we elaborate on the possible formation mechanisms of the MFR through distinct ways. Thirdly, we discuss the initiation of the MFR and associated dynamics during its evolution toward the CME/flare. Finally, we come to some conclusions and put forward some prospects in the future. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950047151&hterms=imprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dimprint','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950047151&hterms=imprint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dimprint">Flow downstream of the heliospheric terminal shock: Magnetic field line topology and solar cycle imprint</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Nerney, Steven; Suess, S. T.; Schmahl, E. J. 1995-01-01 The topology of the magnetic field in the heliosheath is illustrated using plots of the field lines. It is shown that the Archimedean spiral inside the terminal shock is rotated back in the heliosheath into nested spirals that are advected in the direction of the interstellar wind. The 22-year solar magnetic cycle is imprinted onto these field lines in the form of unipolar magnetic envelopes surrounded by volumes of strongly mixed polarity. Each envelope is defined by the changing tilt of the heliospheric current sheet, which is in turn defined by the boundary of unipolar high-latitude regions on the Sun that shrink to the pole at solar maximum and expand to the equator at solar minimum. The detailed shape of the envelopes is regulated by the solar wind velocity structure in the heliosheath. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PASJ...69...98U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PASJ...69...98U">Temporal relations between magnetic bright points and the solar sunspot cycle</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Utz, Dominik; Muller, Richard; Van Doorsselaere, Tom 2017-12-01 The Sun shows a global magnetic field cycle traditionally best visible in the photosphere as a changing sunspot cycle featuring roughly an 11-year period. In addition we know that our host star also harbours small-scale magnetic fields often seen as strong concentrations of magnetic flux reaching kG field strengths. These features are situated in inter-granular lanes, where they show up bright as so-called magnetic bright points (MBPs). In this short paper we wish to analyse an homogenous, nearly 10-year-long synoptic Hinode image data set recorded from 2006 November up to 2016 February in the G-band to inspect the relationship between the number of MBPs at the solar disc centre and the relative sunspot number. Our findings suggest that the number of MBPs at the solar disc centre is indeed correlated to the relative sunspot number, but with the particular feature of showing two different temporal shifts between the decreasing phase of cycle 23 including the minimum and the increasing phase of cycle 24 including the maximum. While the former is shifted by about 22 months, the latter is only shifted by less than 12 months. Moreover, we introduce and discuss an analytical model to predict the number of MBPs at the solar disc centre purely depending on the evolution of the relative sunspot number as well as the temporal change of the relative sunspot number and two background parameters describing a possibly acting surface dynamo as well as the strength of the magnetic field diffusion. Finally, we are able to confirm the plausibility of the temporal shifts by a simplistic random walk model. The main conclusion to be drawn from this work is that the injection of magnetic flux, coming from active regions as represented by sunspots, happens on faster time scales than the removal of small-scale magnetic flux elements later on. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SoPh..286..357M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SoPh..286..357M">Solar Magnetic Carpet III: Coronal Modelling of Synthetic Magnetograms</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Meyer, K. A.; Mackay, D. H.; van Ballegooijen, A. A.; Parnell, C. E. 2013-09-01 This article is the third in a series working towards the construction of a realistic, evolving, non-linear force-free coronal-field model for the solar magnetic carpet. Here, we present preliminary results of 3D time-dependent simulations of the small-scale coronal field of the magnetic carpet. Four simulations are considered, each with the same evolving photospheric boundary condition: a 48-hour time series of synthetic magnetograms produced from the model of Meyer et al. ( Solar Phys. 272, 29, 2011). Three simulations include a uniform, overlying coronal magnetic field of differing strength, the fourth simulation includes no overlying field. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. In particular, we study their dependence upon the evolution of the photospheric magnetic field and the strength of the overlying coronal field. We also consider where energy is stored and dissipated within the coronal field. The free magnetic energy built up is found to be more than sufficient to power small-scale, transient phenomena such as nanoflares and X-ray bright points, with the bulk of the free energy found to be stored low down, between 0.5 - 0.8 Mm. The energy dissipated is currently found to be too small to account for the heating of the entire quiet-Sun corona. However, the form and location of energy-dissipation regions qualitatively agree with what is observed on small scales on the Sun. Future MHD modelling using the same synthetic magnetograms may lead to a higher energy release. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MNRAS.465.2734M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MNRAS.465.2734M">A BCool survey of the magnetic fields of planet-hosting solar-type stars</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mengel, M. W.; Marsden, S. C.; Carter, B. D.; Horner, J.; King, R.; Fares, R.; Jeffers, S. V.; Petit, P.; Vidotto, A. A.; Morin, J.; BCool Collaboration 2017-03-01 We present a spectropolarimetric snapshot survey of solar-type planet-hosting stars. In addition to 14 planet-hosting stars observed as part of the BCool magnetic snapshot survey, we obtained magnetic observations of a further 19 planet-hosting solar-type stars in order to see if the presence of close-in planets had an effect on the measured surface magnetic field (|Bℓ|). Our results indicate that the magnetic activity of this sample is congruent with that of the overall BCool sample. The effects of the planetary systems on the magnetic activity of the parent star, if any, are too subtle to detect compared to the intrinsic dispersion and correlations with rotation, age and stellar activity proxies in our sample. Four of the 19 newly observed stars, two of which are subgiants, have unambiguously detected magnetic fields and are future targets for Zeeman-Doppler mapping. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070031867&hterms=Magnetic+Flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMagnetic%2BFlux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070031867&hterms=Magnetic+Flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMagnetic%2BFlux">Using a Magnetic Flux Transport Model to Predict the Solar Cycle</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Lyatskaya, S.; Hathaway, D.; Winebarger, A. 2007-01-01 We present the results of an investigation into the use of a magnetic flux transport model to predict the amplitude of future solar cycles. Recently Dikpati, de Toma, & Gilman (2006) showed how their dynamo model could be used to accurately predict the amplitudes of the last eight solar cycles and offered a prediction for the next solar cycle - a large amplitude cycle. Cameron & Schussler (2007) found that they could reproduce this predictive skill with a simple 1-dimensional surface flux transport model - provided they used the same parameters and data as Dikpati, de Toma, & Gilman. However, when they tried incorporating the data in what they argued was a more realistic manner, they found that the predictive skill dropped dramatically. We have written our own code for examining this problem and have incorporated updated and corrected data for the source terms - the emergence of magnetic flux in active regions. We present both the model itself and our results from it - in particular our tests of its effectiveness at predicting solar cycles. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910973D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910973D">MAVEN observations of complex magnetic field topology in the Martian magnetotail</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> DiBraccio, Gina A.; Espley, Jared R.; Luhmann, Janet G.; Curry, Shannon M.; Gruesbeck, Jacob R.; Connerney, John E. P.; Soobiah, Yasir; Xu, Shaosui; Mitchell, David M.; Harada, Yuki; Halekas, Jasper S.; Brain, David A.; Dong, Chuanfei; Hara, Takuya; Jakosky, Bruce M. 2017-04-01 MAVEN observations have revealed an unexpectedly complex magnetic field configuration in the magnetotail of Mars. This planetary magnetotail forms as the solar wind interacts with the Martian upper atmosphere and the interplanetary magnetic field (IMF) drapes around the planet. This interaction is classically defined as an induced magnetosphere similar to the plasma environments of Venus and comets. However, unlike at these induced magnetic environments, Mars is complicated by the existence of crustal magnetic fields, which are able to reconnect with the IMF to produce open magnetic fields. Preliminary magnetohydrodynamic simulation results have suggested that this magnetic reconnection may be responsible for creating a hybrid magnetotail configuration between intrinsic and induced magnetospheres. This hybrid tail is composed of the closed planetary fields, draped IMF, and two distinct lobes of open magnetic fields. More importantly, these open lobes appear to be twisted by roughly 45°, either clockwise or counterclockwise, from the ecliptic plane with a strong dependence on the east-west component of the IMF and negligible influence from crustal field orientation. To explore this unexpected twisted-tail configuration, we analyze MAVEN Magnetometer (MAG) and Solar Wind Ion Analyzer (SWIA) data to examine magnetic field topology in the Martian magnetotail. We compare the average magnetic field orientation, directed toward and away from the planet, for a variety of solar wind parameters at various downtail distances. We conclude that the east-west IMF component strongly affects the magnetotail structure, as predicted by simulations. Furthermore, these data reveal that the tail lobes are indeed twisted, which we infer based on model results, to be regions of open magnetic fields that are likely reconnected crustal fields. These MAVEN observations confirm that the Martian magnetotail has a hybrid configuration between an intrinsic and induced magnetosphere, shifting </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121..925L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121..925L">Mapping magnetic field lines between the Sun and Earth</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, B.; Cairns, Iver H.; Gosling, J. T.; Steward, G.; Francis, M.; Neudegg, D.; Schulte in den Bäumen, H.; Player, P. R.; Milne, A. R. 2016-02-01 Magnetic field topologies between the Sun and Earth are important for the connectivity to Earth of solar suprathermal particles, e.g., solar energetic particles and beam electrons in type III solar radio bursts. An approach is developed for mapping large-scale magnetic field lines near the solar equatorial plane, using near-Earth observations and a solar wind model with nonzero azimuthal magnetic field at the source surface. Unlike Parker's spiral model, which restricts the in-ecliptic angle ΦB in the Geocentric Solar Ecliptic coordinates to (90°-180°, 270°-360°) and so is unable to predict field configurations for the other ΦB values frequently observed in the solar wind, our approach can account for all the observed ΦB values. A set of predicted maps shows that near both minimal and maximal solar activity the field lines are typically open and that loops with both ends either connected to or disconnected from the Sun are relatively rare. The open field lines, nonetheless, often do not closely follow the Parker spiral, being less or more tightly wound, or strongly azimuthally or radially oriented, or inverted. The time-varying classes, e.g., bidirectional electrons, of suprathermal electron pitch angle distributions (PADs) at 1 AU are predicted from the mapped field line configurations and compared with Wind observations for two solar rotations, one each near solar minimum and solar maximum. PAD predictions by our approach agree quantitatively (≈90%) with the PAD observations and outperform (by ≈20%) PAD predictions using Parker's model. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JHEP...12..076L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JHEP...12..076L">Magnetically-enhanced open string pair production</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lu, J. X. 2017-12-01 We consider the stringy interaction between two parallel stacks of D3 branes placed at a separation. Each stack of D3 branes in a similar fashion carry an electric flux and a magnetic flux with the two sharing no common field strength index. The interaction amplitude has an imaginary part, giving rise to the Schwinger-like pair production of open strings. We find a significantly enhanced rate of this production when the two electric fluxes are almost identical and the brane separation is on the order of string scale. This enhancement will be largest if the two magnetic fluxes are opposite in direction. This novel enhancement results from the interplay of the non-perturbative Schwinger-type pair production due to the electric flux and the stringy tachyon due to the magnetic flux, and may have realistic physical applications. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH51E..08S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH51E..08S">Correlation of Magnetic Fields with Solar Wind Plasma Parameters at 1AU</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shen, F. 2017-12-01 The physical parameters of the solar wind observed in-situ near 1AU have been studied for several decades, and relationships between them, such as the positive correlation between the solar wind plasma temperature T and velocity V, and the negative correlation between density N and velocity V, are well known. However, the magnetic field intensity does not appear to be well correlated with any individual plasma parameter. In this paper, we discuss previously under-reported correlations between B and the combined plasma parameters √NV2 as well as between B and √NT. These two correlations are strong during the periods of corotating interaction regions and high speed streams, moderate during intervals of slow solar wind, and rather poor during the passage of interplanetary coronal mass ejections. The results indicate that the magnetic pressure in the solar wind is well correlated both with the plasma dynamic pressure and the thermal pressure. Then, we employ a 3D MHD model to simulate the formation of the relationships between the magnetic strength B and √NV2 as well as √NT observed at 1AU. The inner boundary condition is derived by empirical models, with the magnetic field and density are optional. Five kinds of boundary conditions at the inner boundary of heliosphere are tested. In the cases that the magnetic field is related to speed at the inner boundary, the correlation coefficients between B and √NV2 as well as between B and √NT are even higher than that in the observational results. At 1AU the simulated radial magnetic field shows little latitude dependence, which matches the observation of Ulysses. Most of the modeled characters in these cases are closer to observation than others. This inner boundary condition may more accurately characterize Sun's magnetic influence on the heliosphere. The new input may be able to improve the simulation of CME propagation in the inner heliosphere and the space weather forecasting. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AN....333..796S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AN....333..796S">The 1.5 meter solar telescope GREGOR</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schmidt, W.; von der Lühe, O.; Volkmer, R.; Denker, C.; Solanki, S. K.; Balthasar, H.; Bello Gonzalez, N.; Berkefeld, Th.; Collados, M.; Fischer, A.; Halbgewachs, C.; Heidecke, F.; Hofmann, A.; Kneer, F.; Lagg, A.; Nicklas, H.; Popow, E.; Puschmann, K. G.; Schmidt, D.; Sigwarth, M.; Sobotka, M.; Soltau, D.; Staude, J.; Strassmeier, K. G.; Waldmann , T. A. 2012-11-01 The 1.5 m telescope GREGOR opens a new window to the understanding of solar small-scale magnetism. The first light instrumentation includes the Gregor Fabry Pérot Interferometer (GFPI), a filter spectro-polarimeter for the visible wavelength range, the GRating Infrared Spectro-polarimeter (GRIS) and the Broad-Band Imager (BBI). The excellent performance of the first two instruments has already been demonstrated at the Vacuum Tower Telescope. GREGOR is Europe's largest solar telescope and number 3 in the world. Its all-reflective Gregory design provides a large wavelength coverage from the near UV up to at least 5 microns. The field of view has a diameter of 150 arcsec. GREGOR is equipped with a high-order adaptive optics system, with a subaperture size of 10 cm, and a deformable mirror with 256 actuators. The science goals are focused on, but not limited to, solar magnetism. GREGOR allows us to measure the emergence and disappearance of magnetic flux at the solar surface at spatial scales well below 100 km. Thanks to its spectro-polarimetric capabilities, GREGOR will measure the interaction between the plasma flows, different kinds of waves, and the magnetic field. This will foster our understanding of the processes that heat the chromosphere and the outer layers of the solar atmosphere. Observations of the surface magnetic field at very small spatial scales will shed light on the variability of the solar brightness. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdSpR..61..759P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdSpR..61..759P">Fundamental (f) oscillations in a magnetically coupled solar interior-atmosphere system - An analytical approach</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pintér, Balázs; Erdélyi, R. 2018-01-01 Solar fundamental (f) acoustic mode oscillations are investigated analytically in a magnetohydrodynamic (MHD) model. The model consists of three layers in planar geometry, representing the solar interior, the magnetic atmosphere, and a transitional layer sandwiched between them. Since we focus on the fundamental mode here, we assume the plasma is incompressible. A horizontal, canopy-like, magnetic field is introduced to the atmosphere, in which degenerated slow MHD waves can exist. The global (f-mode) oscillations can couple to local atmospheric Alfvén waves, resulting, e.g., in a frequency shift of the oscillations. The dispersion relation of the global oscillation mode is derived, and is solved analytically for the thin-transitional layer approximation and for the weak-field approximation. Analytical formulae are also provided for the frequency shifts due to the presence of a thin transitional layer and a weak atmospheric magnetic field. The analytical results generally indicate that, compared to the fundamental value (ω =√{ gk }), the mode frequency is reduced by the presence of an atmosphere by a few per cent. A thin transitional layer reduces the eigen-frequencies further by about an additional hundred microhertz. Finally, a weak atmospheric magnetic field can slightly, by a few percent, increase the frequency of the eigen-mode. Stronger magnetic fields, however, can increase the f-mode frequency by even up to ten per cent, which cannot be seen in observed data. The presence of a magnetic atmosphere in the three-layer model also introduces non-permitted propagation windows in the frequency spectrum; here, f-mode oscillations cannot exist with certain values of the harmonic degree. The eigen-frequencies can be sensitive to the background physical parameters, such as an atmospheric density scale-height or the rate of the plasma density drop at the photosphere. Such information, if ever observed with high-resolution instrumentation and inverted, could help to </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM33B2658D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM33B2658D">MAVEN observations of complex magnetic field configuration in the Martian magnetotail</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> DiBraccio, G. A.; Luhmann, J. G.; Curry, S.; Espley, J. R.; Gruesbeck, J.; Xu, S.; Mitchell, D. L.; Soobiah, Y. I. J.; Connerney, J. E. P.; Dong, C.; Harada, Y.; Ruhunusiri, S.; Halekas, J. S.; Hara, T.; Ma, Y.; Brain, D.; Jakosky, B. M. 2017-12-01 The magnetosphere of Mars has attributes of both induced and intrinsic magnetospheres, forming as a result of direct solar wind interaction with the planet's upper atmosphere and local crustal magnetic fields. Magnetic reconnection is able to occur between the draped interplanetary magnetic field (IMF) and closed crustal magnetic fields, creating an open field topology with one end attached to the planet and the other flowing in the solar wind. For this reason, the Martian magnetotail becomes a complex menagerie of various field topologies that may contribute to atmospheric escape to space. We explore these magnetic topologies in the Martian magnetotail using a combination of observations from the the Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft along with magnetohydrodynamic (MHD) simulations. Preliminary MHD results suggest that the central tail contains two lobes composed of open crustal fields, which are twisted by roughly 45°, either clockwise or counterclockwise from the ecliptic plane, in response to the east-west component of the IMF. These simulated open-field lobes are enveloped by an induced comet-like tail formed by the draped IMF. Using two Earth years of data, we analyze MAVEN Magnetometer and Solar Wind Ion Analyzer (SWIA) measurements to assess the tail magnetic field configuration as a function of IMF orientation. We infer, through data-model comparisons, that the open-field tail lobes are likely a result of reconnection between the crustal fields and the IMF. The open topology of these fields may in fact contribute to atmospheric loss to space. This investigation confirms that the Martian magnetotail is a hybrid configuration between intrinsic and induced magnetospheres, shifting the paradigm of Mars' magnetosphere as we have understood it thus far. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhRvP...9e1003U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhRvP...9e1003U">Electrothermal Feedback and Absorption-Induced Open-Circuit-Voltage Turnover in Solar Cells</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ullbrich, Sascha; Fischer, Axel; Tang, Zheng; Ávila, Jorge; Bolink, Henk J.; Reineke, Sebastian; Vandewal, Koen 2018-05-01 Solar panels easily heat up upon intense solar radiation due to excess energy dissipation of the absorbed photons or by nonradiative recombination of charge carriers. Still, photoinduced self-heating is often ignored when characterizing lab-sized samples. For light-intensity-dependent measurements of the open-circuit voltage (Suns-VO C ), allowing us to characterize the recombination mechanism, sample heating is often not considered, although almost 100% of the absorbed energy is converted into heat. Here, we show that the frequently observed stagnation or even decrease in VOC at increasingly high light intensities can be explained by considering an effective electrothermal feedback between the recombination current and the open-circuit voltage. Our analytical model fully explains the experimental data for various solar-cell technologies, comprising conventional inorganic semiconductors as well as organic and perovskite materials. Furthermore, the model can be exploited to determine the ideality factor, the effective gap, and the temperature rise from a single Suns-VOC measurement at ambient conditions. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH54A..04W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH54A..04W">Multifractal dissipation of intermittent turbulence generated by the magnetic reconnection in the solar wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, Y.; Wei, F.; Feng, X. 2013-12-01 Recent observations revealed a scale-invariant dissipation process in the fast ambient solar wind, while numerical simulations indicated that the dissipation process in collisionless reconnection was multifractal. Here, we investigate the properties of turbulent fluctuations in the magnetic reconnection prevailed region. It is found that there are large magnetic field shear angle and obvious intermittent structures in these regions. The deduced scaling exponents in the dissipation subrange show a multifractal scaling. In comparison, in the nearby region where magnetic reconnection is less prevailed, we find smaller magnetic field shear angle, less intermittent structures, and most importantly, a monofractal dissipation process. These results provide additionally observational evidence for previous observation and simulation work, and they also imply that magnetic dissipation in the solar wind magnetic reconnection might be caused by the intermittent cascade as multifractal processes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830030923&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMagnetic%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830030923&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMagnetic%2Benergy">Magnetohydrodynamics of atmospheric transients. IV - Nonplane two-dimensional analyses of energy conversion and magnetic field evolution. [during corona following solar flare</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wu, S. T.; Nakagawa, Y.; Han, S. M.; Dryer, M. 1982-01-01 The evolution of the magnetic field and the manner of conversion of thermal energy into different forms in the corona following a solar flare are investigated by means of a nonplane magnetohydrodynamic (MHD) analysis. All three components of magnetic field and velocity are treated in a physically self-consistent manner, with all physical variables as functions of time (t) and two spatial coordinates (r, theta). The difference arising from the initial magnetic field, either twisted (force-free) or non-twisted (potential), is demonstrated. Consideration is given to two initial field topologies (open vs. closed). The results demonstrate that the conversion of magnetic energy is faster for the case of the initially twisted (force-free) field than for the initially untwisted (potential) field. In addition, the twisted field is found to produce a complex structure of the density enhancements. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930071260&hterms=Magnetic+Flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DMagnetic%2BFlux','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930071260&hterms=Magnetic+Flux&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DMagnetic%2BFlux">Three-dimensional magnetohydrodynamics of the emerging magnetic flux in the solar atmosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Matsumoto, R.; Tajima, T.; Shibata, K.; Kaisig, M. 1993-01-01 The nonlinear evolution of an emerging magnetic flux tube or sheet in the solar atmosphere is studied through 3D MHD simulations. In the initial state, a horizontal magnetic flux sheet or tube is assumed to be embedded at the bottom of MHD two isothermal gas layers, which approximate the solar photosphere/chromosphere and the corona. The magnetic flux sheet or tube is unstable against the undular mode of the magnetic buoyancy instability. The magnetic loop rises due to the linear and then later nonlinear instabilities caused by the buoyancy enhanced by precipitating the gas along magnetic field lines. We find by 3D simulation that during the ascendance of loops the bundle of flux tubes or even the flux sheet develops into dense gas filaments pinched between magnetic loops. The interchange modes help produce a fine fiber flux structure perpendicular to the magnetic field direction in the linear stage, while the undular modes determine the overall buoyant loop structure. The expansion of such a bundle of magnetic loops follows the self-similar behavior observed in 2D cases studied earlier. Our study finds the threshold flux for arch filament system (AFS) formation to be about 0.3 x 10 exp 20 Mx. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMSH31A0231M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMSH31A0231M">The effect of the magnetic topology of the Magnetic Clouds over the Solar Energetic Particle Events</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Medina, J.; Hidalgo, M.; Blanco, J.; Rodriguez-Pacheco, J. 2007-12-01 We have simulated the effect of the magnetic topology of the Magnetic Clouds (MCs) over the solar energetic particle event (SEPe) fluxes (0.5-100 MeV) provided by solar flares. When a SEPe passes through a MC a characteristic behaviour in the data corresponding to the ion and electron fluxes is observed: a depression after a strong maximum of the flux. Using our cross-section circular and elliptical MC models we have tried to explain that effect, understanding the importance of the topology of the MC. In sight of the results of the preliminary analysis we conclude that the magnitude of the magnetic field seems not to play a significant role but the helicoidal topology associated with topology of the MCs. This work has been supported by the Spanish Comisión Internacional de Ciencia y Tecnologia (CICYT), grant ESP2005-07290-C02-01 and ESP2006-08459. This work is performed inside COST Action 724. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22666223-dependence-stellar-magnetic-activity-cycles-rotational-period-nonlinear-solar-type-dynamo','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22666223-dependence-stellar-magnetic-activity-cycles-rotational-period-nonlinear-solar-type-dynamo">DEPENDENCE OF STELLAR MAGNETIC ACTIVITY CYCLES ON ROTATIONAL PERIOD IN A NONLINEAR SOLAR-TYPE DYNAMO</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Pipin, V. V.; Kosovichev, A. G. 2016-06-01 We study the turbulent generation of large-scale magnetic fields using nonlinear dynamo models for solar-type stars in the range of rotational periods from 14 to 30 days. Our models take into account nonlinear effects of dynamical quenching of magnetic helicity, and escape of magnetic field from the dynamo region due to magnetic buoyancy. The results show that the observed correlation between the period of rotation and the duration of activity cycles can be explained in the framework of a distributed dynamo model with a dynamical magnetic feedback acting on the turbulent generation from either magnetic buoyancy or magnetic helicity. Wemore » discuss implications of our findings for the understanding of dynamo processes operating in solar-like stars.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22520075-activity-analyses-solar-type-stars-observed-kepler-proxies-magnetic-activity','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22520075-activity-analyses-solar-type-stars-observed-kepler-proxies-magnetic-activity">ACTIVITY ANALYSES FOR SOLAR-TYPE STARS OBSERVED WITH KEPLER. I. PROXIES OF MAGNETIC ACTIVITY</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> He, Han; Wang, Huaning; Yun, Duo, E-mail: hehan@nao.cas.cn 2015-11-15 Light curves of solar-type stars often show gradual fluctuations due to rotational modulation by magnetic features (starspots and faculae) on stellar surfaces. Two quantitative measures of modulated light curves are employed as the proxies of magnetic activity for solar-type stars observed with Kepler telescope. The first is named autocorrelation index i{sub AC}, which describes the degree of periodicity of the light curve; the second is the effective fluctuation range of the light curve R{sub eff}, which reflects the depth of rotational modulation. The two measures are complementary and depict different aspects of magnetic activities on solar-type stars. By using themore » two proxies i{sub AC} and R{sub eff}, we analyzed activity properties of two carefully selected solar-type stars observed with Kepler (Kepler ID: 9766237 and 10864581), which have distinct rotational periods (14.7 versus 6.0 days). We also applied the two measures to the Sun for a comparative study. The result shows that both the measures can reveal cyclic activity variations (referred to as i{sub AC}-cycle and R{sub eff}-cycle) on the two Kepler stars and the Sun. For the Kepler star with the faster rotation rate, i{sub AC}-cycle and R{sub eff}-cycle are in the same phase, while for the Sun (slower rotator), they are in the opposite phase. By comparing the solar light curve with simultaneous photospheric magnetograms, it is identified that the magnetic feature that causes the periodic light curve during solar minima is the faculae of the enhanced network region, which can also be a candidate of magnetic features that dominate the periodic light curves on the two Kepler stars.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4912660','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4912660">Observing the release of twist by magnetic reconnection in a solar filament eruption</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Xue, Zhike; Yan, Xiaoli; Cheng, Xin; Yang, Liheng; Su, Yingna; Kliem, Bernhard; Zhang, Jun; Liu, Zhong; Bi, Yi; Xiang, Yongyuan; Yang, Kai; Zhao, Li 2016-01-01 Magnetic reconnection is a fundamental process of topology change and energy release, taking place in plasmas on the Sun, in space, in astrophysical objects and in the laboratory. However, observational evidence has been relatively rare and typically only partial. Here we present evidence of fast reconnection in a solar filament eruption using high-resolution H-alpha images from the New Vacuum Solar Telescope, supplemented by extreme ultraviolet observations. The reconnection is seen to occur between a set of ambient chromospheric fibrils and the filament itself. This allows for the relaxation of magnetic tension in the filament by an untwisting motion, demonstrating a flux rope structure. The topology change and untwisting are also found through nonlinear force-free field modelling of the active region in combination with magnetohydrodynamic simulation. These results demonstrate a new role for reconnection in solar eruptions: the release of magnetic twist. PMID:27306479 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH41F..07Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH41F..07Z">Strong Solar Wind Dynamic Pressure Pulses during Solar Cycle 23 and Their Impacts on Geosynchronous Magnetic Fields</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zuo, P. 2015-12-01 Solar wind dynamic pressure pulse (DPP) structures, across which the dynamic pressure abruptly changes over timescales from a few seconds to several minutes, are often observed in the near-Earth space environment. In this investigation, we first present a statistical study on the properties of strong dynamic pressure pulses in the solar wind during solar cycle 23. It is found that overwhelming majority of DPPs are associated with the solar wind disturbances including the CME-related flows, the corotating interaction regions, as well as the complex ejecta. The annual variations of the averaged occurrence rate of DPPs are roughly in phase with the solar activities. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears no systematic investigations on the response of GMFs to negative DPPs. Here we also study the decompression/compression effects of very strong negative/positive DPPs on GMFs under northward IMFs. In response to the decompression of strong negative DPPs, GMFs on dayside, near the dawn and dusk on nightside are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of events when GOES is located at the midnight sector, GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that on certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here we found that, a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, being stronger at the noon sector. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APS..DPPN11177L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APS..DPPN11177L">Observations of magnetic pumping in the solar wind using MMS data</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lichko, Emily; Egedal, Jan; Daughton, William; Kasper, Justin 2017-10-01 The turbulent cascade is believed to play an important role in the energization of the solar wind plasma. However, there are characteristics of the solar wind that are not readily explained by the cascade, such as the power-law distribution of the solar wind speed. Starting from the drift kinetic equation, we have derived a magnetic pumping model, similar to the magnetic pumping well-known in fusion research, that provides an explanation for these features. In this model, particles are heated by the largest scale turbulent fluctuations, providing a complementary heating mechanism to the turbulent cascade. We will present observations of this mechanism in the bow shock region using data from the Magnetospheric MultiScale mission. This research was conducted with support from National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168, as well as from NSF Award 1404166 and NASA award NNX15AJ73G. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22679576-relationship-between-sunspot-structure-magnetic-field-changes-associated-solar-flares','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22679576-relationship-between-sunspot-structure-magnetic-field-changes-associated-solar-flares">ON THE RELATIONSHIP BETWEEN SUNSPOT STRUCTURE AND MAGNETIC FIELD CHANGES ASSOCIATED WITH SOLAR FLARES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Song, Y. L.; Zhang, M., E-mail: ylsong@bao.ac.cn Many previous studies have shown that magnetic fields and sunspot structures present rapid and irreversible changes associated with solar flares. In this paper, we first use five X-class flares observed by Solar Dynamics Observatory /Helioseismic and Magnetic Imager to show that not only do magnetic fields and sunspot structures show rapid, irreversible changes, but also that these changes are closely related both spatially and temporally. The magnitudes of the correlation coefficients between the temporal variations of the horizontal magnetic field and sunspot intensity are all larger than 0.90, with a maximum value of 0.99 and an average value of 0.96.more » Then, using four active regions during quiescent periods, three observed and one simulated, we show that in sunspot penumbra regions there also exists a close correlation between sunspot intensity and horizontal magnetic field strength in addition to the well-known correlation between sunspot intensity and the normal magnetic field strength. By connecting these two observational phenomena, we show that the sunspot structure change and magnetic field change are two facets of the same phenomena of solar flares; one change might be induced by the change of the other due to a linear correlation between sunspot intensity and magnetic field strength out of a local force balance.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160002245','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160002245">Realistic Modeling of Multi-Scale MHD Dynamics of the Solar Atmosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Kitiashvili, Irina; Mansour, Nagi N.; Wray, Alan; Couvidat, Sebastian; Yoon, Seokkwan; Kosovichev, Alexander 2014-01-01 Realistic 3D radiative MHD simulations open new perspectives for understanding the turbulent dynamics of the solar surface, its coupling to the atmosphere, and the physical mechanisms of generation and transport of non-thermal energy. Traditionally, plasma eruptions and wave phenomena in the solar atmosphere are modeled by prescribing artificial driving mechanisms using magnetic or gas pressure forces that might arise from magnetic field emergence or reconnection instabilities. In contrast, our 'ab initio' simulations provide a realistic description of solar dynamics naturally driven by solar energy flow. By simulating the upper convection zone and the solar atmosphere, we can investigate in detail the physical processes of turbulent magnetoconvection, generation and amplification of magnetic fields, excitation of MHD waves, and plasma eruptions. We present recent simulation results of the multi-scale dynamics of quiet-Sun regions, and energetic effects in the atmosphere and compare with observations. For the comparisons we calculate synthetic spectro-polarimetric data to model observational data of SDO, Hinode, and New Solar Telescope. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhDT........24S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhDT........24S">Magnetic reconnection physics in the solar wind with Voyager 2</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stevens, Michael L. 2009-08-01 Magnetic reconnection is the process by which the magnetic topology evolves in collisionless plasmas. This phenomenon is fundamental to a broad range of astrophysical processes such as stellar flares, magnetospheric substorms, and plasma accretion, yet it is poorly understood and difficult to observe in situ . In this thesis, the solar wind plasma permeating interplanetary space is treated as a laboratory for reconnection physics. I present an exhaustive statistical approach to the identification of reconnection outflow jets in turbulent plasma and magnetic field time series data. This approach has been automated and characterized so that the resulting reconnection survey can be put in context with other related studies. The algorithm is shown to perform similarly to ad hoc studies in the inner heliosphere. Based on this technique, I present a survey of 138 outflow jets for the Voyager 2 spacecraft mission, including the most distant in situ evidence of reconnection discovered to date. Reconnection in the solar wind is shown to be strongly correlated with stream interactions and with solar activity. The solar wind magnetic field is found to be reconnecting via large, quasi-steady slow- mode magnetohydrodynamic structures as far out as the orbit of Neptune. The role of slow-mode shocks is explored and, in one instance, a well-developed reconnection structure is shown to be in good agreement with the Petschek theory for fast reconnection. This is the first reported example of a reconnection exhaust that satisfies the full jump conditions for a stationary slow-mode shock pair. A complete investigation into corotating stream interactions over the Voyager 2 mission has revealed that detectable reconnection structure occurs in about 23% of forced, global-scale current sheets. Contrary to previous studies, I find that signatures of this kind are most likely to be observed for current sheets where the magnetic field shear and the plasma-b are high. Evidence has been found </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Ge%26Ae..57..512N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Ge%26Ae..57..512N">Does magnetic storm generation depend on the solar wind type?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nikolaeva, N. S.; Yermolaev, Yu. I.; Lodkina, I. G.; Yermolaev, M. Yu. 2017-09-01 The purpose of this work is to draw the reader's attention to the problem of possible differences in the generation of magnetic storms by different large-scale solar wind types: corotating interaction regions (CIRs), Sheaths, and interplanetary coronal mass ejections (ICMEs), including magnetic clouds (MCs) and Ejecta. We recently showed that the description of relationships between interplanetary conditions and Dst and Dst* indices with the modified formula by Burton et al. gives an 50% higher efficiency of storm generation by Sheath and CIR than that by ICME. Many function couplings (FCs) between different interplanetary parameters and the magnetosphere state have been suggested in the literature; however, they have not been analyzed for different solar wind types. In this work, we study the generation efficiency of the main phase of a storm by different solar wind streams with the use of 12 FCs on the basis of OMNI data for 1976-2000. The results show that the Sheath has the highest efficiency for most FCs, and MC is the least efficient, and this result corresponds to our previous results. The reliability of the results and possible causes of differences for different FCs and solar wind types are to be studied further. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002PhDT........23B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002PhDT........23B">The influence of crustal magnetic sources on the topology of the Martian magnetic environment</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Brain, David Andrew 2002-09-01 In this thesis I use magnetometer data and magnetic field models to explore the morphology of magnetic fields close to Mars, with emphasis on the manner and extent to which crustal magnetic sources affect the magnetic field configuration. I analyze Mars Global Surveyor (MGS) Magnetometer (MAG) data to determine the relative importance of the solar wind and of crustal magnetic sources in the observations. Crustal sources locally modify the solar wind interaction, adding variability to the Martian magnetic environment that depends on planetary rotation. I identify trends in the vector magnetic field with respect to altitude, solar zenith angle, and geographic location. The influence of the strongest crustal source extends to 1300 1400 km. I then use MAG data to evaluate models for the magnetic field associated with Mars' crust and for the solar wind interaction with the Martian ionosphere. A linear superposition of a spherical harmonic crustal model and a gasdynamic solar wind model improves the fit to MAG data over that from either model individually. I use simple pressure balance to calculate the shape and size of the Martian solar wind obstacle under a variety of different conditions. The obstacle is irregularly shaped (“lumpy”) and varies over the course of a Martian rotation, over a Martian year, and with changes in the upstream pressure. The obstacle above strong crustal sources can exceed 1000 km and is always higher than the altitude of the MGS spacecraft in its mapping orbit. I use a superposition model to explore the magnetic field topology at Mars under a variety of conditions. The model field topology is sensitive to changes in the interplanetary magnetic field (IMF) strength and orientation, as well as to Mars' orientation with respect to the solar wind flow. Regions of open magnetic field are located above strong crustal sources in the models, where the magnetic field is radially oriented with respect to the Martian surface. An examination of MAG </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22356578-statistical-study-free-magnetic-energy-flare-productivity-solar-active-regions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22356578-statistical-study-free-magnetic-energy-flare-productivity-solar-active-regions">Statistical study of free magnetic energy and flare productivity of solar active regions</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Su, J. T.; Jing, J.; Wang, S. Photospheric vector magnetograms from the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory are utilized as the boundary conditions to extrapolate both nonlinear force-free and potential magnetic fields in solar corona. Based on the extrapolations, we are able to determine the free magnetic energy (FME) stored in active regions (ARs). Over 3000 vector magnetograms in 61 ARs were analyzed. We compare FME with the ARs' flare index (FI) and find that there is a weak correlation (<60%) between FME and FI. FME shows slightly improved flare predictability relative to the total unsigned magnetic flux of ARs in themore » following two aspects: (1) the flare productivity predicted by FME is higher than that predicted by magnetic flux and (2) the correlation between FI and FME is higher than that between FI and magnetic flux. However, this improvement is not significant enough to make a substantial difference in time-accumulated FI, rather than individual flare, predictions.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APS..DPPN11182M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APS..DPPN11182M">Experimental Simulation of Solar Wind Interactions with Magnetic Dipole Fields above Insulating Surfaces</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Munsat, Tobin; Deca, Jan; Han, Jia; Horanyi, Mihaly; Wang, Xu; Werner, Greg; Yeo, Li Hsia; Fuentes, Dominic 2017-10-01 Magnetic anomalies on the surfaces of airless bodies such as the Moon interact with the solar wind, resulting in both magnetic and electrostatic deflection of the charged particles and thus localized surface charging. This interaction is studied in the Colorado Solar Wind Experiment with large-cross-section ( 300 cm2) high-energy flowing plasmas (100-800 eV beam ions) that are incident upon a magnetic dipole embedded under various insulating surfaces. Measured 2D plasma potential profiles indicate that in the dipole lobe regions, the surfaces are charged to high positive potentials due to the collection of unmagnetized ions, while the electrons are magnetically shielded. At low ion beam energies, the surface potential follows the beam energy in eV. However, at high energies, the surface potentials in the electron-shielded regions are significantly lower than the beam energies. A series of studies indicate that secondary electrons are likely to play a dominant role in determining the surface potential. Early results will also be presented from a second experiment, in which a strong permanent magnet with large dipole moment (0.55 T, 275 A*m2) is inserted into the flowing plasma beam to replicate aspects of the solar wind interaction with the earth's magnetic field. This work is supported by the NASA SSERVI program. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950060234&hterms=Body+Systems&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DBody%2BSystems','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950060234&hterms=Body+Systems&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DBody%2BSystems">Hypervelocity impacts and magnetization of small bodies in the Solar System</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Chen, Guangqing; Ahrens, Thomas J.; Hide, Raymond 1995-01-01 The observed magnetism of asteroids such as Gaspra and Ida (and other small bodies in the solar system including the Moon and meteorites) may have resulted from an impact-induced shock wave producing a thermodynamic state in which iron-nickel alloy, dispersed in a silicate matrix, is driven from the usual low-temperature, low-pressure, alpha, kaemacite, phase to the paramagnetic, epsilon (hcp), phase. The magnetization was acquired upon rarefaction and reentry into the ferromagnetic, alpha, structure. The degree of remagnetization depends on the strength of the ambient field, which may have been associated with a Solar-System-wide magnetic field. A transient field induced by the impact event itself may have resulted in a significant, or possibly, even a dominant contribution, as well. The scaling law of Housen et al. (Housen, K. R., R. M. Schmidt, and K. A. Holsapple 1991) for catastrophic asteroid impact disaggregation imposes a constraint on the degree to which small planetary bodies may be magnetized and yet survive fragmentation by the same event. Our modeling results show it is possible that Ida was magnetized when a large impact fractured a 125 +/- 22-km-radius protoasteroid to form the Koronis family. Similarly, we calculate that Gaspra could be a magnetized fragment of a 45 +/- 15 km-radius protoasteroid. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22680875','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22680875">Magnetic discontinuities in magnetohydrodynamic turbulence and in the solar wind.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhdankin, Vladimir; Boldyrev, Stanislav; Mason, Joanne; Perez, Jean Carlos 2012-04-27 Recent measurements of solar wind turbulence report the presence of intermittent, exponentially distributed angular discontinuities in the magnetic field. In this Letter, we study whether such discontinuities can be produced by magnetohydrodynamic (MHD) turbulence. We detect the discontinuities by measuring the fluctuations of the magnetic field direction, Δθ, across fixed spatial increments Δx in direct numerical simulations of MHD turbulence with an imposed uniform guide field B(0). A large region of the probability density function (pdf) for Δθ is found to follow an exponential decay, proportional to exp(-Δθ/θ(*)), with characteristic angle θ(*)≈(14°)(b(rms)/B(0))(0.65) for a broad range of guide-field strengths. We find that discontinuities observed in the solar wind can be reproduced by MHD turbulence with reasonable ratios of b(rms)/B(0). We also observe an excess of small angular discontinuities when Δx becomes small, possibly indicating an increasing statistical significance of dissipation-scale structures. The structure of the pdf in this case closely resembles the two-population pdf seen in the solar wind. We thus propose that strong discontinuities are associated with inertial-range MHD turbulence, while weak discontinuities emerge from dissipation-range turbulence. In addition, we find that the structure functions of the magnetic field direction exhibit anomalous scaling exponents, which indicates the existence of intermittent structures. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...851..142W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...851..142W">Is There a CME Rate Floor? CME and Magnetic Flux Values for the Last Four Solar Cycle Minima</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Webb, D. F.; Howard, R. A.; St. Cyr, O. C.; Vourlidas, A. 2017-12-01 The recent prolonged activity minimum has led to the question of whether there is a base level of the solar magnetic field evolution that yields a “floor” in activity levels and also in the solar wind magnetic field strength. Recently, a flux transport model coupled with magneto-frictional simulations has been used to simulate the continuous magnetic field evolution in the global solar corona for over 15 years, from 1996 to 2012. Flux rope eruptions in the simulations are estimated (Yeates), and the results are in remarkable agreement with the shape of the SOlar Heliospheric Observatory/Large Angle and Spectrometric Coronagraph Experiment coronal mass ejection (CME) rate distribution. The eruption rates at the two recent minima approximate the observed-corrected CME rates, supporting the idea of a base level of solar magnetic activity. In this paper, we address this issue by comparing annual averages of the CME occurrence rates during the last four solar cycle minima with several tracers of the global solar magnetic field. We conclude that CME activity never ceases during a cycle, but maintains a base level of 1 CME every 1.5 to ∼3 days during minima. We discuss the sources of these CMEs. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AAS...23030001S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AAS...23030001S">The solar magnetic field: from complexity to simplicity (and back)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schüssler, Manfred 2017-06-01 The Sun is the only astrophysical object that permits a detailed study of the basic processes governing its magnetic field. Observations reveal stunning complexity due to the interaction with turbulent convection. Numerical simulations and observations strongly suggest that most of the small-scale field is generated by a process called small-scale dynamo action. The fundamental nature of this process makes it a candidate for magnetic field generation in a broad variety of astrophysical settings.On the other hand, the global nature of the 11-year cycle (as exhibited, for instance, by the polarity laws of sunspot groups and the regularly reversing axial dipole field) reveals a surprising simplicity. This suggests a description of the global dynamo process underlying the solar cycle in terms of relatively simple concepts. Insufficient knowledge about the structure of magnetic field and flows in the convection zone requires the introduction of a variety of free parameters (or even free functions), which severely impairs the explanatory power of most such models. However, during the last decades, surface observations of plasma flows and magnetic flux emergence, together with studies of magnetic flux transport, provided crucial information aboutthe workings of the dynamo process. They confirm the visionary approach proposed already in the 1960s by Babcock and Leighton. A recent update of their model permits a full study of the space spanned by the few remaining parameters in order to identify the regions with solar-like solutions.Observations of other cool stars show that the magnetic activity level decreases strongly with stellar rotation rate. The relatively slow rotation of the Sun puts it near to the threshold at which global dynamo action ceases. This suggests a further simplification of the dynamo model in terms of a generic normal form for a weakly nonlinear system. Including the inherent randomness brought about by the flux emergence process leads to a stochastic </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983ApJS...52..363Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983ApJS...52..363Y">Dynamo generation of magnetic fields in three-dimensional space - Solar cycle main flux tube formation and reversals</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yoshimura, H. 1983-08-01 The case of the solar magnetic cycle is investigated as a prototype of the dynamo processes involved in the generation of magnetic fields in astrophysics. Magnetohydrodynamic (MHD) equations are solved using a numerical method with a prescribed velocity field in order follow the movement and deformation. It is shown that a simple combination of differential rotation and global convection, given by a linear analysis of fluid dynamics in a rotating sphere, can perpetually create and reverse great magnetic flux tubes encircling the sun. These main flux tubes of the solar cycle are the progenitors of small-scale flux ropes of the solar activity. These findings indicate that magnetic fields can be generated by fluid motions and that MHD equations have a new type of oscillatory solution. It is shown that the solar cycle can be identified with one of these oscillatory solutions. It is proposed that the formation of magnetic flux tubes by streaming plasma flows is a universal mechanism of flux tube formation in astrophysics. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22356518-magnetic-helicity-global-field-solar-cycles','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22356518-magnetic-helicity-global-field-solar-cycles">Magnetic helicity of the global field in solar cycles 23 and 24</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Pipin, V. V.; Pevtsov, A. A. 2014-07-01 For the first time we reconstruct the magnetic helicity density of the global axisymmetric field of the Sun using the method proposed by Brandenburg et al. and Pipin et al. To determine the components of the vector potential, we apply a gauge which is typically employed in mean-field dynamo models. This allows for a direct comparison of the reconstructed helicity with the predictions from the mean-field dynamo models. We apply this method to two different data sets: the synoptic maps of the line-of-sight magnetic field from the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO) andmore » vector magnetic field measurements from the Vector Spectromagnetograph (VSM) on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) system. Based on the analysis of the MDI/SOHO data, we find that in solar cycle 23 the global magnetic field had positive (negative) magnetic helicity in the northern (southern) hemisphere. This hemispheric sign asymmetry is opposite to the helicity of the solar active regions, but it is in agreement with the predictions of mean-field dynamo models. The data also suggest that the hemispheric helicity rule may have reversed its sign during the early and late phases of cycle 23. Furthermore, the data indicate an imbalance in magnetic helicity between the northern and southern hemispheres. This imbalance seems to correlate with the total level of activity in each hemisphere in cycle 23. The magnetic helicity for the rising phase of cycle 24 is derived from SOLIS/VSM data, and qualitatively its latitudinal pattern is similar to the pattern derived from SOHO/MDI data for cycle 23.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663572-magnetically-modulated-heat-transport-global-simulation-solar-magneto-convection','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663572-magnetically-modulated-heat-transport-global-simulation-solar-magneto-convection">Magnetically Modulated Heat Transport in a Global Simulation of Solar Magneto-convection</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Cossette, Jean-Francois; Charbonneau, Paul; Smolarkiewicz, Piotr K. We present results from a global MHD simulation of solar convection in which the heat transported by convective flows varies in-phase with the total magnetic energy. The purely random initial magnetic field specified in this experiment develops into a well-organized large-scale antisymmetric component undergoing hemispherically synchronized polarity reversals on a 40 year period. A key feature of the simulation is the use of a Newtonian cooling term in the entropy equation to maintain a convectively unstable stratification and drive convection, as opposed to the specification of heating and cooling terms at the bottom and top boundaries. When taken together, themore » solar-like magnetic cycle and the convective heat flux signature suggest that a cyclic modulation of the large-scale heat-carrying convective flows could be operating inside the real Sun. We carry out an analysis of the entropy and momentum equations to uncover the physical mechanism responsible for the enhanced heat transport. The analysis suggests that the modulation is caused by a magnetic tension imbalance inside upflows and downflows, which perturbs their respective contributions to heat transport in such a way as to enhance the total convective heat flux at cycle maximum. Potential consequences of the heat transport modulation for solar irradiance variability are briefly discussed.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM21B2175D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM21B2175D">3D Electromagnetic Particle-in-Cell simulations of the solar wind interaction with lunar magnetic anomalies</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Deca, J.; Lapenta, G.; Divin, A. V.; Lembege, B.; Markidis, S. 2013-12-01 Unlike the Earth and Mercury, our Moon has no global magnetic field and is therefore not shielded from the impinging solar wind by a magnetosphere. However, lunar magnetic field measurements made by the Apollo missions provided direct evidence that the Moon has regions of small-scale crustal magnetic fields, ranging up to a few 100km in scale size with surface magnetic field strengths up to hundreds of nanoTeslas. More recently, the Lunar Prospector spacecraft has provided high-resolution observations allowing to construct magnetic field maps of the entire Moon, confirming the earlier results from Apollo, but also showing that the lunar plasma environment is much richer than earlier believed. Typically the small-scale magnetic fields are non-dipolar and rather tiny compared to the lunar radius and mainly clustered on the far side of the moon. Using iPic3D we present the first 3D fully kinetic and electromagnetic Particle-in-Cell simulations of the solar wind interaction with lunar magnetic anomalies. We study the behaviour of a dipole model with variable surface magnetic field strength under changing solar wind conditions and confirm that lunar crustal magnetic fields may indeed be strong enough to stand off the solar wind and form a mini-magnetosphere, as suggested by MHD and hybrid simulations and spacecraft observations. 3D-PIC simulations reveal to be very helpful to analyze the diversion/braking of the particle flux and the characteristics of the resulting particles accumulation. The particle flux to the surface is significantly reduced at the magnetic anomaly, surrounded by a region of enhanced density due to the magnetic mirror effect. Second, the ability of iPic3D to resolve all plasma components (heavy ions, protons and electrons) allows to discuss in detail the electron physics leading to the highly non-adiabatic interactions expected as well as the implications for solar wind shielding of the lunar surface, depending on the scale size (solar wind protons </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JGRA..11112S01N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JGRA..11112S01N">Magnetic helicity and flux tube dynamics in the solar convection zone: Comparisons between observation and theory</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nandy, Dibyendu 2006-12-01 Magnetic helicity, a conserved topological parameter in ideal MHD systems, conditions close to which are realized in the solar plasma, is intimately connected to the creation and subsequent dynamics of magnetic flux tubes in the solar interior. It can therefore be used as a tool to probe such dynamics. In this paper we show how photospheric observations of magnetic helicity of isolated magnetic flux tubes, manifested as the twist and writhe of solar active regions, can constrain the creation and dynamics of flux tubes in the solar convection zone and the nature of convective turbulence itself. We analyze the observed latitudinal distribution of twists in photospheric active regions, derived from solar vector magnetograms, in the largest such sample studied till-date. We confirm and put additional constraints on the hemispheric twist helicity trend and find that the dispersion in the active region twist distribution is latitude-independent, implying that the amplitude of turbulent fluctuations does not vary with latitude in the convection zone. Our data set also shows that the amplitude and dispersion of twist decreases with increasing magnetic size of active regions, supporting the conclusion that larger flux tubes are less affected by turbulence. Among the various theoretical models that have been proposed till-date to explain the origin of twist, our observations best match the Σ effect model, which invokes helical turbulent buffeting of rising flux tubes as the mechanism for twist creation. Finally, we complement our analysis of twists with past observations of tilts in solar active regions and tie them in with theoretical modeling studies, to build up a comprehensive picture of the dynamics of twisted magnetic flux tubes throughout the solar convection zone. This general framework, binding together theory and observations, suggests that flux tubes have a wide range of twists in the solar convection zone, with some as high as to make them susceptible to the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...852...95N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...852...95N">Magnetic Reconnection in Strongly Magnetized Regions of the Low Solar Chromosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ni, Lei; Lukin, Vyacheslav S.; Murphy, Nicholas A.; Lin, Jun 2018-01-01 Magnetic reconnection in strongly magnetized regions around the temperature minimum region of the low solar atmosphere is studied by employing MHD-based simulations of a partially ionized plasma within a reactive 2.5D multi-fluid model. It is shown that in the absence of magnetic nulls in a low β plasma, the ionized and neutral fluid flows are well-coupled throughout the reconnection region. However, non-equilibrium ionization–recombination dynamics play a critical role in determining the structure of the reconnection region, leading to much lower temperature increases and a faster magnetic reconnection rate as compared to simulations that assume plasma to be in ionization–recombination equilibrium. The rate of ionization of the neutral component of the plasma is always faster than recombination within the current sheet region even when the initial plasma β is as high as {β }0=1.46. When the reconnecting magnetic field is in excess of a kilogauss and the plasma β is lower than 0.0145, the initially weakly ionized plasmas can become fully ionized within the reconnection region and the current sheet can be strongly heated to above 2.5× {10}4 K, even as most of the collisionally dissipated magnetic energy is radiated away. The Hall effect increases the reconnection rate slightly, but in the absence of magnetic nulls it does not result in significant asymmetries or change the characteristics of the reconnection current sheet down to meter scales. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22665898','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22665898">Theory of magnetic reconnection in solar and astrophysical plasmas.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Pontin, David I 2012-07-13 Magnetic reconnection is a fundamental process in a plasma that facilitates the release of energy stored in the magnetic field by permitting a change in the magnetic topology. In this paper, we present a review of the current state of understanding of magnetic reconnection. We discuss theoretical results regarding the formation of current sheets in complex three-dimensional magnetic fields and describe the fundamental differences between reconnection in two and three dimensions. We go on to outline recent developments in modelling of reconnection with kinetic theory, as well as in the magnetohydrodynamic framework where a number of new three-dimensional reconnection regimes have been identified. We discuss evidence from observations and simulations of Solar System plasmas that support this theory and summarize some prominent locations in which this new reconnection theory is relevant in astrophysical plasmas. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH43A..03W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH43A..03W">Turbulent Heating and Wave Pressure in Solar Wind Acceleration Modeling: New Insights to Empirical Forecasting of the Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Woolsey, L. N.; Cranmer, S. R. 2013-12-01 The study of solar wind acceleration has made several important advances recently due to improvements in modeling techniques. Existing code and simulations test the competing theories for coronal heating, which include reconnection/loop-opening (RLO) models and wave/turbulence-driven (WTD) models. In order to compare and contrast the validity of these theories, we need flexible tools that predict the emergent solar wind properties from a wide range of coronal magnetic field structures such as coronal holes, pseudostreamers, and helmet streamers. ZEPHYR (Cranmer et al. 2007) is a one-dimensional magnetohydrodynamics code that includes Alfven wave generation and reflection and the resulting turbulent heating to accelerate solar wind in open flux tubes. We present the ZEPHYR output for a wide range of magnetic field geometries to show the effect of the magnetic field profiles on wind properties. We also investigate the competing acceleration mechanisms found in ZEPHYR to determine the relative importance of increased gas pressure from turbulent heating and the separate pressure source from the Alfven waves. To do so, we developed a code that will become publicly available for solar wind prediction. This code, TEMPEST, provides an outflow solution based on only one input: the magnetic field strength as a function of height above the photosphere. It uses correlations found in ZEPHYR between the magnetic field strength at the source surface and the temperature profile of the outflow solution to compute the wind speed profile based on the increased gas pressure from turbulent heating. With this initial solution, TEMPEST then adds in the Alfven wave pressure term to the modified Parker equation and iterates to find a stable solution for the wind speed. This code, therefore, can make predictions of the wind speeds that will be observed at 1 AU based on extrapolations from magnetogram data, providing a useful tool for empirical forecasting of the sol! ar wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1257714','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1257714">Alpha Channeling in Open-System Magnetic Devices</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Fisch, Nathaniel The Grant DE-SC0000736, Alpha Channeling in Open-System Magnetic Devices, is a continuation of the Grant DE-FG02-06ER54851, Alpha Channeling in Mirror Machines. In publications funded by DE-SC0000736, the grant DE-FG02-06ER54851 was actually credited. The key results obtained under Grant DE-SC0000736, Alpha Channeling in Open-System Magnetic Devices, appear in a series of publications. The earlier effort under DE-FG02- 06ER54851 was the subject of a previous Final Report. The theme of this later effort has been unusual confinement effects, or de-confinement effects, in open-field magnetic confinement devices. First, the possibilities in losing axisymmetry were explored. Then a number of issues in rotating plasmamore » were addressed. Most importantly, a spinoff application to plasma separations was recognized, which also resulted in a provisional patent application. (That provisional patent application, however, was not pursued further.) Alpha channeling entails injecting waves into magnetically confined plasma to release energy from one particular ion while ejecting that ion. The ejection of the ion is actually a concomitant effect in releasing energy from the ion to the wave. In rotating plasma, there is the opportunity to store the energy in a radial electric field rather than in waves. In other words, the ejected alpha particle loses its energy to the radial potential, which in turn produces plasma rotation. This is a very useful effect, since producing radial electric fields by other means are technologically more difficult. In fact, one can heat ions, and then eject them, to produce the desired radial field. In each case, there is a separation effect of different ions, which generalizes the original alpha-channeling concept of separating alpha ash from hydrogen. In a further generalization of the separation concept, a double-well filter represents a new way to produce high-throughput separations of ions, potentially useful for nuclear waste remediation.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920061072&hterms=dynamo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddynamo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920061072&hterms=dynamo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Ddynamo">Generation of dynamo magnetic fields in the primordial solar nebula</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Stepinski, Tomasz F. 1992-01-01 The present treatment of dynamo-generated magnetic fields in the primordial solar nebula proceeds in view of the ability of the combined action of Keplerian rotation and helical convention to generate, via alpha-omega dynamo, large-scale magnetic fields in those parts of the nebula with sufficiently high, gas-and magnetic field coupling electrical conductivity. Nebular gas electrical conductivity and the radial distribution of the local dynamo number are calculated for both a viscous-accretion disk model and the quiescent-minimum mass nebula. It is found that magnetic fields can be easily generated and maintained by alpha-omega dynamos occupying the inner and outer parts of the nebula. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUSM.A43B..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUSM.A43B..06S">Integration of Ground-Based Solar FT-IR Absorption Spectroscopy and Open-Path Systems for Atmospheric Analysis</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Steill, J. D.; Hager, J. S.; Compton, R. N. 2006-05-01 Air quality issues in the Knoxville and East Tennessee region are of great concern, particularly as regards the nearby Great Smoky Mountains National Park. Infrared absorption spectroscopy of the atmosphere provides a unique opportunity to analyze the local chemical composition, since many trace atmospheric constituents are open to this analysis, such as O3, CO, CH4, and N2O. Integration of a Bomem DA8 FT-IR spectrometer with rooftop sun-tracking optics and an open-path system provide solar-sourced and boundary- layer atmospheric infrared spectra of these and other relevant atmospheric components. Boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. Vertical concentration profiles are determined by fitting solar-sourced absorbance lines with the SFIT2 algorithm. Improved fitting of solar spectra has been demonstrated by incorporating the tropospheric concentrations as determined by open-path measurements. A record of solar-sourced atmospheric spectra of greater than two years duration is under analysis to characterize experimental error and thus the limit of precision in the concentration determinations. Initial efforts using atmospheric O2 as a calibration indicate the solar- sourced spectra may not yet meet the precision required for accurate atmospheric CO2 quantification by such efforts as the OCO and NDSC. However, this variability is also indicative of local concentration fluxes pertinent to the regional atmospheric chemistry. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of seasonal and diurnal trends in the local trace gas concentrations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29372526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29372526">Solar energy harvesting by magnetic-semiconductor nanoheterostructure in water treatment technology.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Mahmoodi, Vahid; Bastami, Tahereh Rohani; Ahmadpour, Ali 2018-03-01 Photocatalytic degradation of toxic organic pollutants in the wastewater using dispersed semiconductor nanophotocatalysts has a number of advantages such as high activity, cost effectiveness, and utilization of free solar energy. However, it is difficult to recover and recycle nanophotocatalysts since the fine dispersed nanoparticles are easily suspended in waters. Furthermore, a large amount of photocatalysts will lead to color contamination. Thus, it is necessary to prepare photocatalysts with easy separation for the reusable application. To take advantage of high photocatalysis activity and reusability, magnetic photocatalysts with separation function were utilized. In this review, the photocatalytic principle, structure, and application of the magnetic-semiconductor nanoheterostructure photocatalysts under solar light are evaluated. Graphical abstract ᅟ. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780039116&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DOpen%2BField','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780039116&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DOpen%2BField">Open magnetic fields in active regions</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Svestka, Z.; Solodyna, C. V.; Howard, R.; Levine, R. H. 1977-01-01 Soft X-ray images and magnetograms of several active regions and coronal holes are examined which support the interpretation that some of the dark X-ray gaps seen between interconnecting loops and inner cores of active regions are foot points of open field lines inside the active regions. Characteristics of the investigated dark gaps are summarized. All the active regions with dark X-ray gaps at the proper place and with the correct polarity predicted by global potential extrapolation of photospheric magnetic fields are shown to be old active regions, indicating that field opening is accomplished only in a late phase of active-region development. It is noted that some of the observed dark gaps probably have nothing in common with open fields, but are either due to the decreased temperature in low-lying portions of interconnecting loops or are the roots of higher and less dense or cooler loops. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24027782','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24027782">Probe of the solar magnetic field using the "cosmic-ray shadow" of the sun.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Amenomori, M; Bi, X J; Chen, D; Chen, T L; Chen, W Y; Cui, S W; Danzengluobu; Ding, L K; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gou, Q B; Guo, Y Q; Hakamada, K; He, H H; He, Z T; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Jia, H Y; Jiang, L; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, H J; Li, W J; Liu, C; Liu, J S; Liu, M Y; Lu, H; Meng, X R; Mizutani, K; Munakata, K; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ozawa, S; Qian, X L; Qu, X B; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Shao, J; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, H; Wu, H R; Xue, L; Yamamoto, Y; Yang, Z; Yasue, S; Yuan, A F; Yuda, T; Zhai, L M; Zhang, H M; Zhang, J L; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhang, Ying; Zhaxisangzhu; Zhou, X X 2013-07-05 We report on a clear solar-cycle variation of the Sun’s shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun’s shadow, using the potential field source surface model and the current sheet source surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun’s shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun’s shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun’s shadow observed in the TeV cosmic-ray flux. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020094344','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020094344">The Structure and Dynamics of the Solar Corona and Inner Heliosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Mikic, Zoran 2002-01-01 This report covers technical progress during the second quarter of the first year of NASA Sun-Earth Connections Theory Program (SECTP) contract 'The Structure and Dynamics of the Solar Corona and Inner Heliosphere,' NAS5-99188, between NASA and Science Applications International Corporation. and covers the period November 16, 1999 to February 15, 2000. Under this contract SAIC and the University of California, Irvine (UCI) have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD (magnetohydrodynamic) model. The topics studied include: the effect of emerging flux on the stability of helmet streamers, coronal loops and streamers, the solar magnetic field, the solar wind, and open magnetic field lines. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090020586','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090020586">Open-Access, Low-Magnetic-Field MRI System for Lung Research</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Mair, Ross W.; Rosen, Matthew S.; Tsai, Leo L.; Walsworth, Ronald L.; Hrovat, Mirko I.; Patz, Samuel; Ruset, Iullian C.; Hersman, F. William 2009-01-01 An open-access magnetic resonance imaging (MRI) system is being developed for use in research on orientational/gravitational effects on lung physiology and function. The open-access geometry enables study of human subjects in diverse orientations. This system operates at a magnetic flux density, considerably smaller than the flux densities of typical other MRI systems, that can be generated by resistive electromagnet coils (instead of the more-expensive superconducting coils of the other systems). The human subject inhales air containing He-3 or Xe-129 atoms, the nuclear spins of which have been polarized by use of a laser beam to obtain a magnetic resonance that enables high-resolution gas space imaging at the low applied magnetic field. The system includes a bi-planar, constant-current, four-coil electromagnet assembly and associated electronic circuitry to apply a static magnetic field of 6.5 mT throughout the lung volume; planar coils and associated circuitry to apply a pulsed magnetic-field-gradient for each spatial dimension; a single, detachable radio-frequency coil and associated circuitry for inducing and detecting MRI signals; a table for supporting a horizontal subject; and electromagnetic shielding surrounding the electromagnet coils. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SpWea..16..230A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SpWea..16..230A">Ionospheric Peak Electron Density and Performance Evaluation of IRI-CCIR Near Magnetic Equator in Africa During Two Extreme Solar Activities</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Adebesin, B. O.; Rabiu, A. B.; Obrou, O. K.; Adeniyi, J. O. 2018-03-01 The F2 layer peak electron density (NmF2) was investigated over Korhogo (Geomagnetic: 1.26°S, 67.38°E), a station near the magnetic equator in the African sector. Data for 1996 and 2000 were, respectively, categorized into low solar quiet and disturbed and high solar quiet and disturbed. NmF2 prenoon peak was higher than the postnoon peak during high solar activity irrespective of magnetic activity condition, while the postnoon peak was higher for low solar activity. Higher NmF2 peak amplitude characterizes disturbed magnetic activity than quiet magnetic condition for any solar activity. The maximum peaks appeared in equinox. June solstice noontime bite out lagged other seasons by 1-2 h. For any condition of solar and magnetic activities, the daytime NmF2 percentage variability (%VR) measured by the relative standard deviation maximizes/minimizes in June solstice/equinox. Daytime variability increases with increasing magnetic activity. The highest peak in the morning time NmF2 variability occurs in equinox, while the highest evening/nighttime variability appeared in June solstice for all solar/magnetic conditions. The nighttime annual variability amplitude is higher during disturbed than quiet condition regardless of solar activity period. At daytime, variability is similar for all conditions of solar activities. NmF2 at Korhogo is well represented on the International Reference Ionosphere-International Radio Consultative Committee (IRI-CCIR) option. The model/observation relationship performed best between local midnight and postmidnight period (00-08 LT). The noontime trough characteristics is not prominent in the IRI pattern during high solar activity but evident during low solar conditions when compared with Korhogo observations. The Nash-Sutcliffe coefficients revealed better model performance during disturbed activities. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH11A2420A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH11A2420A">Endogenous Magnetic Reconnection in Solar Coronal Loops</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Asgari-Targhi, M.; Coppi, B.; Basu, B.; Fletcher, A.; Golub, L. 2017-12-01 We propose that a magneto-thermal reconnection process occurring in coronal loops be the source of the heating of the Solar Corona [1]. In the adopted model, magnetic reconnection is associated with electron temperature gradients, anisotropic electron temperature fluctuations and plasma current density gradients [2]. The input parameters for our theoretical model are derived from the most recent observations of the Solar Corona. In addition, the relevant (endogenous) collective modes can produce high energy particle populations. An endogenous reconnection process is defined as being driven by factors internal to the region where reconnection takes place. *Sponsored in part by the U.S. D.O.E. and the Kavli Foundation* [1] Beafume, P., Coppi, B. and Golub, L., (1992) Ap. J. 393, 396. [2] Coppi, B. and Basu, B. (2017) MIT-LNS Report HEP 17/01. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPA11A3870C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPA11A3870C">Reading The Sun: A Three Dimensional Visual Model of The Solar Environment During Solar Cycle 24</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Carranza-fulmer, T. L.; Moldwin, M. 2014-12-01 The sun is a powerful force that has proven to our society that it has a large impact on our lives. Unfortunately, there is still a lack of awareness on how the sun is capable of affecting Earth. The over all idea of "Reading The Sun" installation is to help demonstrate how the sun impacts the Earth, by compiling various data sources from satellites (SOHO, SDO, and STERO) with solar and solar wind models (MAS and ENLIL) to create a comprehensive three dimensional display of the solar environment. It focuses on the current solar maximum of solar cycle 24 and a CME that impacted Earth's magnetic field on February 27, 2014, which triggered geomagnetic storms around the Earth's poles. The CME was an after-effect of a class X4.9 solar flare, which was released from the sun on February 25, 2014. "Reading The Sun" is a 48" x 48" x 48" hanging model of the sun with color coded open opposing magnetic field lines along with various layers of the solar atmosphere, the heliospheric current sheet, and the inner planets. At the center of the xyz axis is the sun with the open magnetic field lines and the heliospheric current sheet permeating inner planetary space. The xyz axes are color coded to represent various types of information with corresponding visual images for the viewer to be able to read the model. Along the z-axis are three colors (yellow, orange, and green) that represent the different layers of the solar atmosphere (photosphere, chromosphere, and corona) that correspond to three satellite images in various spectrums related to a CME and Solar Flare and the xy-plane shows where the inner planets are in relation to the sun. The exhibit in which "Reading The Sun "is being displayed is called, The Rotation of Language at the Wheather Again Gallery in Rockaway, New York. The intent of the exhibit is to both celebrate as well as present a cautionary tale on the ability of human language to spark and ignite the individual and collective imagination towards an experience </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950029330&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOpen%2BField','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950029330&hterms=Open+Field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DOpen%2BField">Disruption of coronal magnetic field arcades</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Mikic, Zoran; Linker, Jon A. 1994-01-01 The ideal and resistive properties of isolated large-scale coronal magnetic arcades are studied using axisymmetric solutions of the time-dependent magnetohydrodynamic (MHD) equations in spherical geometry. We examine how flares and coronal mass ejections may be initiated by sudden disruptions of the magnetic field. The evolution of coronal arcades in response to applied shearing photospheric flows indicates that disruptive behavior can occur beyond a critical shear. The disruption can be traced to ideal MHD magnetic nonequilibrium. The magnetic field expands outward in a process that opens the field lines and produces a tangential discontinuity in the magnetic field. In the presence of plasma resistivity, the resulting current sheet is the site of rapid reconnection, leading to an impulsive release of magnetic energy, fast flows, and the ejection of a plasmoid. We relate these results to previous studies of force-free fields and to the properties of the open-field configuration. We show that the field lines in an arcade are forced open when the magnetic energy approaches (but is still below) the open-field energy, creating a partially open field in which most of the field lines extend away from the solar surface. Preliminary application of this model to helmet streamers indicates that it is relevant to the initiation of coronal mass ejections. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...792L..40S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...792L..40S">Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Song, H. Q.; Zhang, J.; Chen, Y.; Cheng, X. 2014-09-01 Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are the results of eruptions of magnetic flux ropes (MFRs). However, there is heated debate on whether MFRs exist prior to the eruptions or if they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures, and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre-existing MFR scenario. There is almost no reported observation of MFR formation during the eruption. In this Letter, we present an intriguing observation of a solar eruptive event that occurred on 2013 November 21 with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows the formation process of the MFR during the eruption in detail. The process began with the expansion of a low-lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~10 MK), presumably an MFR, producing a CME. We suggest that two spatially separated magnetic reconnections occurred in this event, which were responsible for producing the flare and the hot blob (CME). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSH43B4203S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSH43B4203S">Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Song, H.; Zhang, J.; Chen, Y.; Cheng, X. 2014-12-01 Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are results of eruptions of magnetic flux ropes (MFRs). However, a heated debate is on whether MFRs pre-exist before the eruptions or they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre existing MFR scenario. There is almost no reported observation about MFR formation during the eruption. In this presentation, we present an intriguing observation of a solar eruptive event with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows a detailed formation process of the MFR during the eruption. The process started with the expansion of a low lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly-formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved-in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~ 10 MK), presumably a MFR, producing a CME. We suggest that two spatially-separated magnetic reconnections occurred in this event, responsible for producing the flare and the hot blob (CME), respectively. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22130727-solar-cycle-propagation-memory-prediction-insights-from-century-magnetic-proxies','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22130727-solar-cycle-propagation-memory-prediction-insights-from-century-magnetic-proxies">SOLAR CYCLE PROPAGATION, MEMORY, AND PREDICTION: INSIGHTS FROM A CENTURY OF MAGNETIC PROXIES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Munoz-Jaramillo, Andres; DeLuca, Edward E.; Dasi-Espuig, Maria The solar cycle and its associated magnetic activity are the main drivers behind changes in the interplanetary environment and Earth's upper atmosphere (commonly referred to as space weather). These changes have a direct impact on the lifetime of space-based assets and can create hazards to astronauts in space. In recent years there has been an effort to develop accurate solar cycle predictions (with aims at predicting the long-term evolution of space weather), leading to nearly a hundred widely spread predictions for the amplitude of solar cycle 24. A major contributor to the disagreement is the lack of direct long-term databasesmore » covering different components of the solar magnetic field (toroidal versus poloidal). Here, we use sunspot area and polar faculae measurements spanning a full century (as our toroidal and poloidal field proxies) to study solar cycle propagation, memory, and prediction. Our results substantiate predictions based on the polar magnetic fields, whereas we find sunspot area to be uncorrelated with cycle amplitude unless multiplied by area-weighted average tilt. This suggests that the joint assimilation of tilt and sunspot area is a better choice (with aims to cycle prediction) than sunspot area alone, and adds to the evidence in favor of active region emergence and decay as the main mechanism of poloidal field generation (i.e., the Babcock-Leighton mechanism). Finally, by looking at the correlation between our poloidal and toroidal proxies across multiple cycles, we find solar cycle memory to be limited to only one cycle.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4421823','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4421823">Witnessing magnetic twist with high-resolution observation from the 1.6-m New Solar Telescope</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Wang, Haimin; Cao, Wenda; Liu, Chang; Xu, Yan; Liu, Rui; Zeng, Zhicheng; Chae, Jongchul; Ji, Haisheng 2015-01-01 Magnetic flux ropes are highly twisted, current-carrying magnetic fields. They are crucial for the instability of plasma involved in solar eruptions, which may lead to adverse space weather effects. Here we present observations of a flaring using the highest resolution chromospheric images from the 1.6-m New Solar Telescope at Big Bear Solar Observatory, supplemented by a magnetic field extrapolation model. A set of loops initially appear to peel off from an overall inverse S-shaped flux bundle, and then develop into a multi-stranded twisted flux rope, producing a two-ribbon flare. We show evidence that the flux rope is embedded in sheared arcades and becomes unstable following the enhancement of its twists. The subsequent motion of the flux rope is confined due to the strong strapping effect of the overlying field. These results provide a first opportunity to witness the detailed structure and evolution of flux ropes in the low solar atmosphere. PMID:25919706 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.1628L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.1628L">Flow Sources of The Solar Wind Stream Structieres</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lotova, N. A.; Obridko, V. N.; Vladimirskii, K. V. The large-scale stream structure of the solar wind flow was studied at the main acceler- ation area of 10 to 40 solar radii from the Sun. Three independent sets of experimental data were used: radio astronomy observations of radio wave scattering on near-solar plasmas (large radio telescopes of the P.N.Lebedev Physical Institute were used); mor- phology of the WLC as revealed by the SOHO optical solar corona observations; solar magnetic field strength and configuration computed using the Wilcox Solar Observa- tory data. Experimental data of 1997-1998 years on the position of the transition, tran- sonic region of the solar wind flow were used as a parameter reflecting the intensity of the solar plasmas acceleration process. Correlation studies of these data combined with the magnetic field strength at the solar corona level revealed several types of the solar wind streams differing in the final result, the velocity at large distances from the Sun. Besides of the well-known flows stemming from the polar coronal holes, high-speed streams were observed arising in lateral areas of the streamer structures in contrast to the main body of the streamers, being a known source of the slow solar wind. The slowest streams arise at areas of mixed magnetic field structure compris- ing both open and closed (loop-like) filed lines. In the white-light corona images this shows extensive areas of bright amorphous luminosity. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22660967-heating-mechanisms-low-solar-atmosphere-through-magnetic-reconnection-current-sheets','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22660967-heating-mechanisms-low-solar-atmosphere-through-magnetic-reconnection-current-sheets">HEATING MECHANISMS IN THE LOW SOLAR ATMOSPHERE THROUGH MAGNETIC RECONNECTION IN CURRENT SHEETS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Ni, Lei; Lin, Jun; Roussev, Ilia I. 2016-12-01 We simulate several magnetic reconnection processes in the low solar chromosphere/photosphere; the radiation cooling, heat conduction and ambipolar diffusion are all included. Our numerical results indicate that both the high temperature (≳8 × 10{sup 4} K) and low temperature (∼10{sup 4} K) magnetic reconnection events can happen in the low solar atmosphere (100–600 km above the solar surface). The plasma β controlled by plasma density and magnetic fields is one important factor to decide how much the plasma can be heated up. The low temperature event is formed in a high β magnetic reconnection process, Joule heating is the mainmore » mechanism to heat plasma and the maximum temperature increase is only several thousand Kelvin. The high temperature explosions can be generated in a low β magnetic reconnection process, slow and fast-mode shocks attached at the edges of the well developed plasmoids are the main physical mechanisms to heat the plasma from several thousand Kelvin to over 8 × 10{sup 4} K. Gravity in the low chromosphere can strongly hinder the plasmoid instability and the formation of slow-mode shocks in a vertical current sheet. Only small secondary islands are formed; these islands, however, are not as well developed as those in the horizontal current sheets. This work can be applied to understand the heating mechanism in the low solar atmosphere and could possibly be extended to explain the formation of common low temperature Ellerman bombs (∼10{sup 4} K) and the high temperature Interface Region Imaging Spectrograph (IRIS) bombs (≳8 × 10{sup 4}) in the future.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SoPh..292..122K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SoPh..292..122K">Solar-Cycle Variation of Subsurface-Flow Divergence: A Proxy of Magnetic Activity?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Komm, R.; Howe, R.; Hill, F. 2017-09-01 We study the solar-cycle variation of subsurface flows from the surface to a depth of 16 Mm. We have analyzed Global Oscillation Network Group (GONG) Dopplergrams with a ring-diagram analysis covering about 15 years and Helioseismic and Magnetic Imager (HMI) Dopplergrams covering more than 6 years. After subtracting the average rotation rate and meridional flow, we have calculated the divergence of the horizontal residual flows from the maximum of Solar Cycle 23 through the declining phase of Cycle 24. The subsurface flows are mainly divergent at quiet regions and convergent at locations of high magnetic activity. The relationship is essentially linear between divergence and magnetic activity at all activity levels at depths shallower than about 10 Mm. At greater depths, the relationship changes sign at locations of high activity; the flows are increasingly divergent at locations with a magnetic activity index (MAI) greater than about 24 G. The flows are more convergent by about a factor of two during the rising phase of Cycle 24 than during the declining phase of Cycle 23 at locations of medium and high activity (about 10 to 40 G MAI) from the surface to at least 10 Mm. The subsurface divergence pattern of Solar Cycle 24 first appears during the declining phase of Cycle 23 and is present during the extended minimum. It appears several years before the magnetic pattern of the new cycle is noticeable in synoptic maps. Using linear regression, we estimate the amount of magnetic activity that would be required to generate the precursor pattern and find that it should be almost twice the amount of activity that is observed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016usc..confE.112C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016usc..confE.112C">Emergence of magnetic flux generated in a solar convective dynamo</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, Feng; Rempel, Feng, Matthias; Fan, Yuhong 2016-10-01 We present a realistic numerical model of sunspot and active region formation through the emergence of flux tubes generated in a solar convective dynamo. The magnetic and velocity fields in a horizontal layer near the top boundary of the solar convective dynamo simulation are used as a time-dependent bottom boundary to drive the radiation magnetohydrodynamic simulations of the emergence of the flux tubes through the upper most layer of the convection zone to the photosphere. The emerging flux tubes interact with the convection and break into small scale magnetic elements that further rise to the photosphere. At the photosphere, several bipolar pairs of sunspots are formed through the coalescence of the small scale magnetic elements. The sunspot pairs in the simulation successfully reproduce the fundamental observed properties of solar active regions, including the more coherent leading spots with a stronger field strength, and the correct tilts of the bipolar pairs. These asymmetries originate from the intrinsic asymmetries in the emerging fields imposed at the bottom boundary, where the horizontal fields are already tilted. The leading sides of the emerging flux tubes are up against the downdraft lanes of the giant cells and strongly sheared downward. This leads to the stronger field strength of the leading polarity fields. We find a prograde flow in the emerging flux tube, which is naturally inherited from the solar convective dynamo simulation. The prograde flow gradually becomes a diverging flow as the flux tube rises. The emerging speed is similar to upflow speed of convective motions. The azimuthal average of the flows around a (leading) sunspot reveals a predominant down flow inside the sunspots and a large-scale horizontal inflow at the depth of about 10 Mm. The inflow pattern becomes an outflow in upper most convection zone in the vicinity of the sunspot, which could be considered as moat flows. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JMagR.282...10K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JMagR.282...10K">Transport-related triplet states and hyperfine couplings in organic tandem solar cells probed by pulsed electrically detected magnetic resonance spectroscopy</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kraffert, Felix; Bahro, Daniel; Meier, Christoph; Denne, Maximilian; Colsmann, Alexander; Behrends, Jan 2017-09-01 Tandem solar cells constitute the most successful organic photovoltaic devices with power conversion efficiencies comparable to thin-film silicon solar cells. Especially their high open-circuit voltage - only achievable by a well-adjusted layer stacking - leads to their high efficiencies. Nevertheless, the microscopic processes causing the lossless recombination of charge carriers within the recombination zone are not well understood yet. We show that advanced pulsed electrically detected magnetic resonance techniques such as electrically detected (ED)-Rabi nutation measurements and electrically detected hyperfine sublevel correlation (ED-HYSCORE) spectroscopy help to understand the role of triplet excitons in these microscopic processes. We investigate fully working miniaturised organic tandem solar cells and detect current-influencing doublet states in different layers as well as triplet excitons located on the fullerene-based acceptor. We apply ED-HYSCORE in order to study the nuclear spin environment of the relevant electron/hole spins and detect a significant amount of the low abundant 13C nuclei coupled to the observer spins. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AnGeo..36..527R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AnGeo..36..527R">Three-dimensional density and compressible magnetic structure in solar wind turbulence</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Roberts, Owen W.; Narita, Yasuhito; Escoubet, C.-Philippe 2018-03-01 The three-dimensional structure of both compressible and incompressible components of turbulence is investigated at proton characteristic scales in the solar wind. Measurements of the three-dimensional structure are typically difficult, since the majority of measurements are performed by a single spacecraft. However, the Cluster mission consisting of four spacecraft in a tetrahedral formation allows for a fully three-dimensional investigation of turbulence. Incompressible turbulence is investigated by using the three vector components of the magnetic field. Meanwhile compressible turbulence is investigated by considering the magnitude of the magnetic field as a proxy for the compressible fluctuations and electron density data deduced from spacecraft potential. Application of the multi-point signal resonator technique to intervals of fast and slow wind shows that both compressible and incompressible turbulence are anisotropic with respect to the mean magnetic field direction P⟂ ≫ P∥ and are sensitive to the value of the plasma beta (β; ratio of thermal to magnetic pressure) and the wind type. Moreover, the incompressible fluctuations of the fast and slow solar wind are revealed to be different with enhancements along the background magnetic field direction present in the fast wind intervals. The differences in the fast and slow wind and the implications for the presence of different wave modes in the plasma are discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850026776','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850026776">Dynamics of the penetration boundaries of solar protons during a strong magnetic storm</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Glukhov, G. A.; Kratenko, Y. P.; Mineev, Y. V. 1985-01-01 The variations in the equatorial penetration boundary of solar protons with E sub p = 0.9 to 8.0 MeV during a strong magnetic storm of April 3 to 5, were analyzed. The dynamics of this boundary is compared with the dynamics of the outer trapping boundary of electrons with E sub e = - 0.3 to 0.6 MeV. The solar-proton penetration and the structure of the real magnetic field are studied. The unique data on the thin structure of development of a magnetospheric substorm were obtained for the first time. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SoPh..282..379B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SoPh..282..379B">Multiscale Magnetic Underdense Regions on the Solar Surface: Granular and Mesogranular Scales</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Berrilli, F.; Scardigli, S.; Giordano, S. 2013-02-01 The Sun is a non-equilibrium, dissipative system subject to an energy flow that originates in its core. Convective overshooting motions create temperature and velocity structures that show a temporal and spatial multiscale evolution. As a result, photospheric structures are generally considered to be a direct manifestation of convective plasma motions. The plasma flows in the photosphere govern the motion of single magnetic elements. These elements are arranged in typical patterns, which are observed as a variety of multiscale magnetic patterns. High-resolution magnetograms of the quiet solar surface revealed the presence of multiscale magnetic underdense regions in the solar photosphere, commonly called voids, which may be considered to be a signature of the underlying convective structure. The analysis of such patterns paves the way for the investigation of all turbulent convective scales, from granular to global. In order to address the question of magnetic structures driven by turbulent convection at granular and mesogranular scales, we used a voids-detection method. The computed distribution of void length scales shows an exponential behavior at scales between 2 and 10 Mm and the absence of features at mesogranular scales. The absence of preferred scales of organization in the 2 - 10 Mm range supports the multiscale nature of flows on the solar surface and the absence of a mesogranular convective scale. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19960021377&hterms=method+magnetic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmethod%2Bmagnetic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19960021377&hterms=method+magnetic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmethod%2Bmagnetic">A new method of presentation the large-scale magnetic field structure on the Sun and solar corona</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ponyavin, D. I. 1995-01-01 The large-scale photospheric magnetic field, measured at Stanford, has been analyzed in terms of surface harmonics. Changes of the photospheric field which occur within whole solar rotation period can be resolved by this analysis. For this reason we used daily magnetograms of the line-of-sight magnetic field component observed from Earth over solar disc. We have estimated the period during which day-to-day full disc magnetograms must be collected. An original algorithm was applied to resolve time variations of spherical harmonics that reflect time evolution of large-scale magnetic field within solar rotation period. This method of magnetic field presentation can be useful enough in lack of direct magnetograph observations due to sometimes bad weather conditions. We have used the calculated surface harmonics to reconstruct the large-scale magnetic field structure on the source surface near the sun - the origin of heliospheric current sheet and solar wind streams. The obtained results have been compared with spacecraft in situ observations and geomagnetic activity. We tried to show that proposed technique can trace shon-time variations of heliospheric current sheet and short-lived solar wind streams. We have compared also our results with those obtained traditionally from potential field approximation and extrapolation using synoptic charts as initial boundary conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AIPC.1953e0025S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AIPC.1953e0025S">Open circuit voltage-decay behavior in amorphous p-i-n solar due to injection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Smrity, Manu; Dhariwal, S. R. 2018-05-01 The paper deals with the basic recombination processes at the dangling bond and the band tail states at various levels of injection, expressed in terms of short-circuit current density and their role in the behavior of amorphous solar cells. As the level of injection increases the fill factor decreases whereas the open circuit voltage increases very slowly, showing a saturation tendency. Calculations have been done for two values of tail state densities and shows that with an increase in tail state densities both, the fill factor and open circuit voltage decreases, results an overall degradation of the solar cell. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1342748-correlation-energy-disorder-open-circuit-voltage-hybrid-perovskite-solar-cells','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1342748-correlation-energy-disorder-open-circuit-voltage-hybrid-perovskite-solar-cells">Correlation of energy disorder and open-circuit voltage in hybrid perovskite solar cells</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Shao, Yuchuan; Yuan, Yongbo; Huang, Jinsong 2016-01-11 Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focussed on optimisation of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron-transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH 3NH 3PbI 3 planar-heterojunction photovoltaic cells increases from 17.1% to 19.4% when the energy disorder in the fullerene electron-transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result ofmore » the enhancement in open-circuit voltage from 1.04 V to 1.13 V without sacrificing the short-circuit current and fill factor. Finally, these results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a new path to further increase their efficiency« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM43E..09C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM43E..09C">The influence of Mars' magnetic topology on atmospheric escape</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Curry, S.; Luhmann, J. G.; DiBraccio, G. A.; Dong, C.; Xu, S.; Mitchell, D.; Gruesbeck, J.; Espley, J. R.; Connerney, J. E. P.; McFadden, J. P.; Ma, Y. J.; Brain, D. 2017-12-01 At weakly magnetized planets such as Mars and Venus, the solar wind directly interacts with the upper atmosphere where ions can be picked up and swept away by the background convection electric field. These pick-up ions have a gyroradius on the planetary scale that is largely dominated by the interplanetary magnetic field (IMF). But at Mars, their trajectory is also influenced by the existence of remanent crustal magnetic fields, which are thought to create a shielding effect for escaping planetary ions when they are on the dayside. Consequently, the magnetic topology changes at Mars as magnetic reconnection occurs between the draped (IMF) and the crustal magnetic fields (closed). The resulting topology includes open field lines in the solar wind with one footprint attached to the planet. Using magnetohydrodynamic (MHD) and test particle simulations, we will explore the influence of the magnetic topology on ion escape. We will present escape rates for planetary ions for different crustal field positions during different IMF configurations, with +/-BY and +/-BZ components in the Mars Sun Orbit (MSO) coordinate system. We will also compare global maps of ion outflow and escape with open / closed magnetic field line maps and compare our results with ion fluxes and magnetic field data from the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission. Our results relating the dynamic magnetic field topology at Mars and planetary ion escape are an important aspect of magnetospheric physics and planetary evolution, both of which have applications to our own solar system and the increasing number of exoplanets discovered every year. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22486411-magnetic-field-configuration-small-scale-reconnection-events-solar-plasma-atmosphere','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22486411-magnetic-field-configuration-small-scale-reconnection-events-solar-plasma-atmosphere">3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Shimizu, T., E-mail: shimizu@solar.isas.jaxa.jp; Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 2015-10-15 The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at themore » photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first group, two anti-parallel magnetic fields reconnect to each other, yielding a 2D emerging flux configuration. In the second group, helical or twisted magnetic flux tubes are parallel or at a relative angle to each other. Reconnection can occur only between anti-parallel components of the magnetic flux tubes and may be referred to as component reconnection. The latter configuration type may be more important for the larger class of small-scale reconnection events. The two types of magnetic configurations can be compared to counter-helicity and co-helicity configurations, respectively, in laboratory plasma collision experiments.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840021328','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840021328">Cosmic rays, solar activity, magnetic coupling, and lightning incidence</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ely, J. T. A. 1984-01-01 A theoretical model is presented and described that unifies the complex influence of several factors on spatial and temporal variation of lightning incidence. These factors include the cosmic radiation, solar activity, and coupling between geomagnetic and interplanetary (solar wind) magnetic fields. Atmospheric electrical conductivity in the 10 km region was shown to be the crucial parameter altered by these factors. The theory reconciles several large scale studies of lightning incidence previously misinterpreted or considered contradictory. The model predicts additional strong effects on variations in lightning incidence, but only small effects on the morphology and rate of thunderstorm development. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SoPh..293...34S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SoPh..293...34S">Probing Twisted Magnetic Field Using Microwave Observations in an M Class Solar Flare on 11 February, 2014</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sharykin, I. N.; Kuznetsov, A. A.; Myshyakov, I. I. 2018-02-01 This work demonstrates the possibility of magnetic-field topology investigations using microwave polarimetric observations. We study a solar flare of GOES M1.7 class that occurred on 11 February, 2014. This flare revealed a clear signature of spatial inversion of the radio-emission polarization sign. We show that the observed polarization pattern can be explained by nonthermal gyrosynchrotron emission from the twisted magnetic structure. Using observations of the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Observatory, Radio Solar Telescope Network, and Solar Dynamics Observatory, we have determined the parameters of nonthermal electrons and thermal plasma and identified the magnetic structure where the flare energy release occurred. To reconstruct the coronal magnetic field, we use nonlinear force-free field (NLFFF) and potential magnetic-field approaches. Radio emission of nonthermal electrons is simulated by the GX Simulator code using the extrapolated magnetic field and the parameters of nonthermal electrons and thermal plasma inferred from the observations; the model radio maps and spectra are compared with observations. We have found that the potential-magnetic-field approach fails to explain the observed circular polarization pattern; on the other hand, the Stokes-V map is successfully explained by assuming nonthermal electrons to be distributed along the twisted magnetic structure determined by the NLFFF extrapolation approach. Thus, we show that the radio-polarization maps can be used for diagnosing the topology of the flare magnetic structures where nonthermal electrons are injected. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122.1831X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122.1831X">Martian low-altitude magnetic topology deduced from MAVEN/SWEA observations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xu, Shaosui; Mitchell, David; Liemohn, Michael; Fang, Xiaohua; Ma, Yingjuan; Luhmann, Janet; Brain, David; Steckiewicz, Morgane; Mazelle, Christian; Connerney, Jack; Jakosky, Bruce 2017-02-01 The Mars Atmosphere and Volatile Evolution mission has obtained comprehensive particle and magnetic field measurements. The Solar Wind Electron Analyzer provides electron energy-pitch angle distributions along the spacecraft trajectory that can be used to infer magnetic topology. This study presents pitch angle-resolved electron energy shape parameters that can distinguish photoelectrons from solar wind electrons, which we use to deduce the Martian magnetic topology and connectivity to the dayside ionosphere. Magnetic topology in the Mars environment is mapped in three dimensions for the first time. At low altitudes (<400 km) in sunlight, the northern hemisphere is found to be dominated by closed field lines (both ends intersecting the collisional atmosphere), with more day-night connections through cross-terminator closed field lines than in the south. Although draped field lines with 100 km amplitude vertical fluctuations that intersect the electron exobase ( 160-220 km) in two locations could appear to be closed at the spacecraft, a more likely explanation is provided by crustal magnetic fields, which naturally have the required geometry. Around 30% of the time, we observe open field lines from 200 to 400 km, which implies three distinct topological layers over the northern hemisphere: closed field lines below 200 km, open field lines with foot points at lower latitudes that pass over the northern hemisphere from 200 to 400 km, and draped interplanetary magnetic field above 400 km. This study also identifies open field lines with one end attached to the dayside ionosphere and the other end connected with the solar wind, providing a path for ion outflow. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667481-charged-dust-grain-dynamics-subject-solar-wind-poyntingrobertson-drag-interplanetary-magnetic-field','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667481-charged-dust-grain-dynamics-subject-solar-wind-poyntingrobertson-drag-interplanetary-magnetic-field">CHARGED DUST GRAIN DYNAMICS SUBJECT TO SOLAR WIND, POYNTING–ROBERTSON DRAG, AND THE INTERPLANETARY MAGNETIC FIELD</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Lhotka, Christoph; Bourdin, Philippe; Narita, Yasuhito, E-mail: christoph.lhotka@oeaw.ac.at, E-mail: philippe.bourdin@oeaw.ac.at, E-mail: yasuhito.narita@oeaw.ac.at We investigate the combined effect of solar wind, Poynting–Robertson drag, and the frozen-in interplanetary magnetic field on the motion of charged dust grains in our solar system. For this reason, we derive a secular theory of motion by the means of an averaging method and validate it with numerical simulations of the unaveraged equations of motions. The theory predicts that the secular motion of charged particles is mainly affected by the z -component of the solar magnetic axis, or the normal component of the interplanetary magnetic field. The normal component of the interplanetary magnetic field leads to an increase ormore » decrease of semimajor axis depending on its functional form and sign of charge of the dust grain. It is generally accepted that the combined effects of solar wind and photon absorption and re-emmision (Poynting–Robertson drag) lead to a decrease in semimajor axis on secular timescales. On the contrary, we demonstrate that the interplanetary magnetic field may counteract these drag forces under certain circumstances. We derive a simple relation between the parameters of the magnetic field, the physical properties of the dust grain, as well as the shape and orientation of the orbital ellipse of the particle, which is a necessary conditions for the stabilization in semimajor axis.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Nanot..28Q4001L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Nanot..28Q4001L">Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Limpert, Steven; Burke, Adam; Chen, I.-Ju; Anttu, Nicklas; Lehmann, Sebastian; Fahlvik, Sofia; Bremner, Stephen; Conibeer, Gavin; Thelander, Claes; Pistol, Mats-Erik; Linke, Heiner 2017-10-01 Compared to traditional pn-junction photovoltaics, hot carrier solar cells offer potentially higher efficiency by extracting work from the kinetic energy of photogenerated ‘hot carriers’ before they cool to the lattice temperature. Hot carrier solar cells have been demonstrated in high-bandgap ferroelectric insulators and GaAs/AlGaAs heterostructures, but so far not in low-bandgap materials, where the potential efficiency gain is highest. Recently, a high open-circuit voltage was demonstrated in an illuminated wurtzite InAs nanowire with a low bandgap of 0.39 eV, and was interpreted in terms of a photothermoelectric effect. Here, we point out that this device is a hot carrier solar cell and discuss its performance in those terms. In the demonstrated devices, InP heterostructures are used as energy filters in order to thermoelectrically harvest the energy of hot electrons photogenerated in InAs absorber segments. The obtained photovoltage depends on the heterostructure design of the energy filter and is therefore tunable. By using a high-resistance, thermionic barrier, an open-circuit voltage is obtained that is in excess of the Shockley-Queisser limit. These results provide generalizable insight into how to realize high voltage hot carrier solar cells in low-bandgap materials, and therefore are a step towards the demonstration of higher efficiency hot carrier solar cells. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780068596&hterms=1607&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D%2526%25231607','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780068596&hterms=1607&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D%2526%25231607">Sources of magnetic fields in recurrent interplanetary streams</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Burlaga, L. F.; Behannon, K. W.; Hansen, S. F.; Pneuman, G. W.; Feldman, W. C. 1978-01-01 The paper examines sources of magnetic fields in recurrent streams observed by the Imp 8 and Heos spacecraft at 1 AU and by Mariner 10 en route to Mercury between October 31, 1973 and February 9, 1974, during Carrington rotations 1607-1610. Although most fields and plasmas at 1 AU were related to coronal holes and the magnetic field lines were open in those holes, some of the magnetic fields and plasmas at 1 AU were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines may be more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes, certain photospheric magnetic fields, and the coronal footprints of the sector boundaries on the source surface are characterized. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060036372&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060036372&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS">(abstract) The Distant Tail Behavior During High Speed Solar Wind Streams and Magnetic Storms</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ho, C. M.; Tsurutani, B. T. 1996-01-01 We have examined the ISEE-3 distant tail data during three intense magnetic storms and have identified the tail response to high speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171393','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171393">The Fraction of Interplanetary Coronal Mass Ejections That Are Magnetic Clouds: Evidence for a Solar Cycle Variation</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Richardson, I. G.; Cane, H. V. 2004-01-01 "Magnetic clouds" (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized by enhanced magnetic fields with an organized rotation in direction, and low plasma beta. Though intensely studied, MCs only constitute a fraction of all the ICMEs that are detected in the solar wind. A comprehensive survey of ICMEs in the near- Earth solar wind during the ascending, maximum and early declining phases of solar cycle 23 in 1996 - 2003 shows that the MC fraction varies with the phase of the solar cycle, from approximately 100% (though with low statistics) at solar minimum to approximately 15% at solar maximum. A similar trend is evident in near-Earth observations during solar cycles 20 - 21, while Helios 1/2 spacecraft observations at 0.3 - 1.0 AU show a weaker trend and larger MC fraction. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH42A..05L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH42A..05L">Predicting the La Niña of 2020-21: Termination of Solar Cycles and Correlated Variance in Solar and Atmospheric Variability</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Leamon, R. J.; McIntosh, S. W. 2017-12-01 observed and physical processes to be studied. This result potentially opens the door to a broader understanding of solar variability on our planet and its weather. Ongoing tracking of solar magnetic band migration indicates that Cycle 24 will terminate in the 2020 timeframe and thus we may expect to see an attendant shift to La Niña conditions at that time. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhDT.........3U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhDT.........3U">Brightness and magnetic evolution of solar coronal bright points</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ugarte Urra, Ignacio This thesis presents a study of the brightness and magnetic evolution of several Extreme ultraviolet (EUV) coronal bright points (hereafter BPs). The study was carried out using several instruments on board the Solar and Heliospheric Observatory, supported by the high resolution imaging from the Transition Region And Coronal Explorer. The results confirm that, down to 1" resolution, BPs are made of small loops with lengths of [approximate]6 Mm and cross-sections of ≈2 Mm. The loops are very dynamic, evolving in time scales as short as 1 - 2 minutes. This is reflected in a highly variable EUV response with fluctuations highly correlated in spectral lines at transition region temperatures, but not always at coronal temperatures. A wavelet analysis of the intensity variations reveals the existence of quasi-periodic oscillations with periods ranging 400--1000s, in the range of periods characteristic of the chromospheric network. The link between BPs and network bright points is discussed, as well as the interpretation of the oscillations in terms of global acoustic modes of closed magnetic structures. A comparison of the magnetic flux evolution of the magnetic polarities to the EUV flux changes is also presented. Throughout their lifetime, the intrinsic EUV emission of BPs is found to be dependent on the total magnetic flux of the polarities. In short time scales, co-spatial and co-temporal coronal images and magnetograms, reveal the signature of heating events that produce sudden EUV brightenings simultaneous to magnetic flux cancellations. This is interpreted in terms of magnetic reconnection events. Finally, a electron density study of six coronal bright points produces values of ≈1.6×10 9 cm -3 , closer to active region plasma than to quiet Sun. The analysis of a large coronal loop (half length of 72 Mm) introduces the discussion on the prospects of future plasma diagnostics of BPs with forthcoming solar missions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940033532&hterms=magnetic+particles&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmagnetic%2Bparticles','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940033532&hterms=magnetic+particles&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmagnetic%2Bparticles">Simultaneous observations of solar MeV particles in a magnetic cloud and in the earth's northern tail lobe - Implications for the global field line topology of magnetic clouds and for the entry of solar particles into the magnetosphere during cloud passage</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Farrugia, C. J.; Richardson, I. G.; Burlaga, L. F.; Lepping, R. P.; Osherovich, V. A. 1993-01-01 Simultaneous ISEE 3 and IMP 8 spacecraft observations of magnetic fields and flow anisotropies of solar energetic protons and electrons during the passage of an interplanetary magnetic cloud show various particle signature differences at the two spacecraft. These differences are interpretable in terms of the magnetic line topology of the cloud, the connectivity of the cloud field lines to the solar surface, and the interconnection between the magnetic fields of the magnetic clouds and of the earth. These observations are consistent with a magnetic cloud model in which these mesoscale configurations are curved magnetic flux ropes attached at both ends to the sun's surface, extending out to 1 AU. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...860...35D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...860...35D">A Study of a Compound Solar Eruption with Two Consecutive Erupting Magnetic Structures</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dhakal, Suman K.; Chintzoglou, Georgios; Zhang, Jie 2018-06-01 We report a study of a compound solar eruption that was associated with two consecutively erupting magnetic structures and correspondingly two distinct peaks, during impulsive phase, of an M-class flare (M8.5). Simultaneous multi-viewpoint observations from SDO, GOES and STEREO-A show that this compound eruption originated from two pre-existing sigmoidal magnetic structures lying along the same polarity inversion line. Observations of the associated pre-existing filaments further show that these magnetic structures are lying one on top of the other, separated by 12 Mm in height, in a so-called “double-decker” configuration. The high-lying magnetic structure became unstable and erupted first, appearing as an expanding hot channel seen at extreme ultraviolet wavelengths. About 12 minutes later, the low-lying structure also started to erupt and moved at an even faster speed compared to the high-lying one. As a result, the two erupting structures interacted and merged with each other, appearing as a single coronal mass ejection in the outer corona. We find that the double-decker configuration is likely caused by the persistent shearing motion and flux cancellation along the source active region’s strong-gradient polarity inversion line. The successive destabilization of these two separate but closely spaced magnetic structures, possibly in the form of magnetic flux ropes, led to a compound solar eruption. The study of the compound eruption provides a unique opportunity to reveal the formation process, initiation, and evolution of complex eruptive structures in solar active regions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910006658','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910006658">Numerical simulation of solar coronal magnetic fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Dahlburg, Russell B.; Antiochos, Spiro K.; Zang, T. A. 1990-01-01 Many aspects of solar activity are believed to be due to the stressing of the coronal magnetic field by footpoint motions at the photosphere. The results are presented of a fully spectral numerical simulation which is the first 3-D time dependent simulation of footpoint stressing in a geometry appropriate for the corona. An arcade is considered that is initially current-free and impose a smooth footpoint motion that produces a twist in the field of approx 2 pi. The footprints were fixed and the evolution was followed until the field relaxes to another current-free state. No evidence was seen for any instability, either ideal or resistive and no evidence for current sheet formation. The most striking feature of the evolution is that in response to photospheric motions, the field expands rapidly upward to minimize the stress. The expansion has two important effects. First, it suppresses the development of dips in the field that could support dense, cool material. For the motions assumed, the magnetic field does not develop a geometry suitable for prominence formation. Second, the expansion inhibits ideal instabilities such as kinking. The results indicate that simple stearing of a single arcade is unlikely to lead to solar activity such as flares or prominences. Effects are discussed that might possibly lead to such activity. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22130978-two-novel-parameters-evaluate-global-complexity-sun-magnetic-field-track-solar-cycle','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22130978-two-novel-parameters-evaluate-global-complexity-sun-magnetic-field-track-solar-cycle">TWO NOVEL PARAMETERS TO EVALUATE THE GLOBAL COMPLEXITY OF THE SUN'S MAGNETIC FIELD AND TRACK THE SOLAR CYCLE</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Zhao, L.; Landi, E.; Gibson, S. E., E-mail: lzh@umich.edu 2013-08-20 Since the unusually prolonged and weak solar minimum between solar cycles 23 and 24 (2008-2010), the sunspot number is smaller and the overall morphology of the Sun's magnetic field is more complicated (i.e., less of a dipole component and more of a tilted current sheet) compared with the same minimum and ascending phases of the previous cycle. Nearly 13 yr after the last solar maximum ({approx}2000), the monthly sunspot number is currently only at half the highest value of the past cycle's maximum, whereas the polar magnetic field of the Sun is reversing (north pole first). These circumstances make itmore » timely to consider alternatives to the sunspot number for tracking the Sun's magnetic cycle and measuring its complexity. In this study, we introduce two novel parameters, the standard deviation (SD) of the latitude of the heliospheric current sheet (HCS) and the integrated slope (SL) of the HCS, to evaluate the complexity of the Sun's magnetic field and track the solar cycle. SD and SL are obtained from the magnetic synoptic maps calculated by a potential field source surface model. We find that SD and SL are sensitive to the complexity of the HCS: (1) they have low values when the HCS is flat at solar minimum, and high values when the HCS is highly tilted at solar maximum; (2) they respond to the topology of the HCS differently, as a higher SD value indicates that a larger part of the HCS extends to higher latitude, while a higher SL value implies that the HCS is wavier; (3) they are good indicators of magnetically anomalous cycles. Based on the comparison between SD and SL with the normalized sunspot number in the most recent four solar cycles, we find that in 2011 the solar magnetic field had attained a similar complexity as compared to the previous maxima. In addition, in the ascending phase of cycle 24, SD and SL in the northern hemisphere were on the average much greater than in the southern hemisphere, indicating a more tilted and wavier HCS in the </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4394680','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4394680">The role of turbulence in coronal heating and solar wind expansion</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Cranmer, Steven R.; Asgari-Targhi, Mahboubeh; Miralles, Mari Paz; Raymond, John C.; Strachan, Leonard; Tian, Hui; Woolsey, Lauren N. 2015-01-01 Plasma in the Sun's hot corona expands into the heliosphere as a supersonic and highly magnetized solar wind. This paper provides an overview of our current understanding of how the corona is heated and how the solar wind is accelerated. Recent models of magnetohydrodynamic turbulence have progressed to the point of successfully predicting many observed properties of this complex, multi-scale system. However, it is not clear whether the heating in open-field regions comes mainly from the dissipation of turbulent fluctuations that are launched from the solar surface, or whether the chaotic ‘magnetic carpet’ in the low corona energizes the system via magnetic reconnection. To help pin down the physics, we also review some key observational results from ultraviolet spectroscopy of the collisionless outer corona. PMID:25848083 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...855...84X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...855...84X">North–South Asymmetry of the Rotation of the Solar Magnetic Field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xie, Jinglan; Shi, Xiangjun; Qu, Zhining 2018-03-01 Using the rotation rates of the solar magnetic field during solar cycles 21 to 23 obtained by Chu et al. by analyzing the synoptic magnetic maps produced by the NSO/Kitt Peak and SOHO/MDI during the years 1975 to 2008, the temporal variation of the equatorial rotation rate (A) and the latitude gradient of rotation (B) in the northern and southern hemispheres are studied separately. The results indicate that the rotation is more differential (about 4.3%) in the southern hemisphere in the considered time frame. It is found that the north–south asymmetry of A and the asymmetry of B show increasing trends in the considered time frame, while the north–south asymmetry of the solar activity shows a decreasing trend. There exists a significant negative correlation (at 95% confidence level) between the asymmetry of B and the asymmetry of the solar activity, and this may be due to stronger magnetic activity in a certain hemisphere that may suppress the differential rotation to some extent. The periodicities in the variation of A and B are also studied, and periods of about 5.0 and 10.5 yr (5.5 and 10.4 yr) can be found for the variation of the northern (southern) hemisphere B. Moreover, the north–south asymmetry of A and the asymmetry of B have similar periods of about 2.6–2.7 and 5.2–5.3 yr. Further, cross-correlation analysis indicates that there exists a phase difference (about eight months) between the northern and southern hemisphere B, and this means that the northern hemisphere B generally leads by about eight months. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22518594-direct-observation-solar-coronal-magnetic-fields-vector-tomography-coronal-emission-line-polarizations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22518594-direct-observation-solar-coronal-magnetic-fields-vector-tomography-coronal-emission-line-polarizations">DIRECT OBSERVATION OF SOLAR CORONAL MAGNETIC FIELDS BY VECTOR TOMOGRAPHY OF THE CORONAL EMISSION LINE POLARIZATIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kramar, M.; Lin, H.; Tomczyk, S., E-mail: kramar@cua.edu, E-mail: lin@ifa.hawaii.edu, E-mail: tomczyk@ucar.edu We present the first direct “observation” of the global-scale, 3D coronal magnetic fields of Carrington Rotation (CR) Cycle 2112 using vector tomographic inversion techniques. The vector tomographic inversion uses measurements of the Fe xiii 10747 Å Hanle effect polarization signals by the Coronal Multichannel Polarimeter (CoMP) and 3D coronal density and temperature derived from scalar tomographic inversion of Solar Terrestrial Relations Observatory (STEREO)/Extreme Ultraviolet Imager (EUVI) coronal emission lines (CELs) intensity images as inputs to derive a coronal magnetic field model that best reproduces the observed polarization signals. While independent verifications of the vector tomography results cannot be performed, wemore » compared the tomography inverted coronal magnetic fields with those constructed by magnetohydrodynamic (MHD) simulations based on observed photospheric magnetic fields of CR 2112 and 2113. We found that the MHD model for CR 2112 is qualitatively consistent with the tomography inverted result for most of the reconstruction domain except for several regions. Particularly, for one of the most noticeable regions, we found that the MHD simulation for CR 2113 predicted a model that more closely resembles the vector tomography inverted magnetic fields. In another case, our tomographic reconstruction predicted an open magnetic field at a region where a coronal hole can be seen directly from a STEREO-B/EUVI image. We discuss the utilities and limitations of the tomographic inversion technique, and present ideas for future developments.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667486-relationship-between-chromospheric-evaporation-magnetic-field-topology-class-solar-flare','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667486-relationship-between-chromospheric-evaporation-magnetic-field-topology-class-solar-flare">RELATIONSHIP BETWEEN CHROMOSPHERIC EVAPORATION AND MAGNETIC FIELD TOPOLOGY IN AN M-CLASS SOLAR FLARE</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Sadykov, Viacheslav M; Kosovichev, Alexander G; Sharykin, Ivan N 2016-09-01 Chromospheric evaporation is observed as Doppler blueshift during solar flares. It plays a key role in the dynamics and energetics of solar flares; however, its mechanism is still unknown. In this paper, we present a detailed analysis of spatially resolved multi-wavelength observations of chromospheric evaporation during an M 1.0-class solar flare (SOL2014-06-12T21:12) using data from NASA’s Interface Region Imaging Spectrograph and HMI/ SDO (the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory), and high-resolution observations from VIS/NST (the Visible Imaging Spectrometer at the New Solar Telescope). The results show that the averaged over the flare region Fe xximore » blueshift of the hot (10{sup 7} K) evaporating plasma is delayed relative to the C ii redshift of the relatively cold (10{sup 4} K) chromospheric plasma by about one minute. The spatial distribution of the delays is not uniform across the region and can be as long as two minutes in several zones. Using vector magnetograms from HMI, we reconstruct the magnetic field topology and the quasi-separatrix layer, and find that the blueshift delay regions as well as the H α flare ribbons are connected to the region of the magnetic polarity inversion line (PIL) and an expanding flux rope via a system of low-lying loop arcades with a height of ≲4.5 Mm. As a result, the chromospheric evaporation may be driven by the energy release in the vicinity of PIL, and has the observed properties due to a local magnetic field topology.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH43C..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH43C..01S">Multi-wavelength Observations and Modeling of Solar Flares: Magnetic Structures</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Su, Y. 2017-12-01 We present a review of our recent investigations on multi-wavelength observations and magnetic field modeling of solar flares. High-resolution observations taken by NVST and BBSO/NST reveal unprecedented fine structures of the flaring regions. Observations by SDO, IRIS, and GOES provide the complementary information. The magnetic field models are constructed using either non-linear force free field extrapolations or flux rope insertion method. Our studies have shown that the flaring regions often consist of double or multiple flux ropes, which often exist at different heights. The fine flare ribbon structures may be due to the magnetic reconnection in the complex quasi separatrix layers. The magnetic field modeling of several large flares suggests that the so called hot-channel structure is corresponding to the erupting flux rope above the X-point in a magnetic configuration with Hyperbolic Flux Tube. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22047970-role-background-overlying-magnetic-field-solar-eruptions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22047970-role-background-overlying-magnetic-field-solar-eruptions">ON THE ROLE OF THE BACKGROUND OVERLYING MAGNETIC FIELD IN SOLAR ERUPTIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Nindos, A.; Patsourakos, S.; Wiegelmann, T., E-mail: anindos@cc.uoi.gr 2012-03-20 The primary constraining force that inhibits global solar eruptions is provided by the overlying background magnetic field. Using magnetic field data from both the Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory and the spectropolarimeter of the Solar Optical Telescope aboard Hinode, we study the long-term evolution of the background field in active region AR11158 that produced three major coronal mass ejections (CMEs). The CME formation heights were determined using EUV data. We calculated the decay index -(z/B)({partial_derivative}B/{partial_derivative}z) of the magnetic field B (i.e., how fast the field decreases with height, z) related to each event from the timemore » of the active region emergence until well after the CMEs. At the heights of CME formation, the decay indices were 1.1-2.1. Prior to two of the events, there were extended periods (of more than 23 hr) where the related decay indices at heights above the CME formation heights either decreased (up to -15%) or exhibited small changes. The decay index related to the third event increased (up to 118%) at heights above 20 Mm within an interval that started 64 hr prior to the CME. The magnetic free energy and the accumulated helicity into the corona contributed the most to the eruptions by their increase throughout the flux emergence phase (by factors of more than five and more than two orders of magnitude, respectively). Our results indicate that the initiation of eruptions does not depend critically on the temporal evolution of the variation of the background field with height.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170003051&hterms=Mysteries&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DMysteries','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170003051&hterms=Mysteries&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DMysteries">Implications of L1 Observations for Slow Solar Wind Formation by Solar Reconnection</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Kepko, L.; Viall, N. M.; Antiochos, S. K.; Lepri, S. T.; Kasper, J. C.; Weberg, M. 2016-01-01 While the source of the fast solar wind is known to be coronal holes, the source of the slow solar wind has remained a mystery. Long time scale trends in the composition and charge states show strong correlations between solar wind velocity and plasma parameters, yet these correlations have proved ineffective in determining the slow wind source. We take advantage of new high time resolution (12 min) measurements of solar wind composition and charge state abundances at L1 and previously identified 90 min quasi periodic structures to probe the fundamental timescales of slow wind variability. The combination of new high temporal resolution composition measurements and the clearly identified boundaries of the periodic structures allows us to utilize these distinct solar wind parcels as tracers of slowwind origin and acceleration. We find that each 90 min (2000 Mm) parcel of slow wind has near-constant speed yet exhibits repeatable, systematic charge state and composition variations that span the entire range of statistically determined slow solar wind values. The classic composition-velocity correlations do not hold on short, approximately hour long, time scales. Furthermore, the data demonstrate that these structures were created by magnetic reconnection. Our results impose severe new constraints on slow solar wind origin and provide new, compelling evidence that the slow wind results from the sporadic release of closed field plasma via magnetic reconnection at the boundary between open and closed flux in the Sun's atmosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IAUGA..2250036P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IAUGA..2250036P">Two-fluid 2.5D code for simulations of small scale magnetic fields in the lower solar atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Piantschitsch, Isabell; Amerstorfer, Ute; Thalmann, Julia Katharina; Hanslmeier, Arnold; Lemmerer, Birgit 2015-08-01 Our aim is to investigate magnetic reconnection as a result of the time evolution of magnetic flux tubes in the solar chromosphere. A new numerical two-fluid code was developed, which will perform a 2.5D simulation of the dynamics from the upper convection zone up to the transition region. The code is based on the Total Variation Diminishing Lax-Friedrichs method and includes the effects of ion-neutral collisions, ionisation/recombination, thermal/resistive diffusivity as well as collisional/resistive heating. What is innovative about our newly developed code is the inclusion of a two-fluid model in combination with the use of analytically constructed vertically open magnetic flux tubes, which are used as initial conditions for our simulation. First magnetohydrodynamic (MHD) tests have already shown good agreement with known results of numerical MHD test problems like e.g. the Orszag-Tang vortex test, the Current Sheet test or the Spherical Blast Wave test. Furthermore, the single-fluid approach will also be applied to the initial conditions, in order to compare the different rates of magnetic reconnection in both codes, the two-fluid code and the single-fluid one. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9727969','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9727969">Lunar surface magnetic fields and their interaction with the solar wind: results from lunar prospector</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lin; Mitchell; Curtis; Anderson; Carlson; McFadden; Acuna; Hood; Binder 1998-09-04 The magnetometer and electron reflectometer experiment on the Lunar Prospector spacecraft has obtained maps of lunar crustal magnetic fields and observed the interaction between the solar wind and regions of strong crustal magnetic fields at high selenographic latitude (30 degreesS to 80 degreesS) and low ( approximately 100 kilometers) altitude. Electron reflection maps of the regions antipodal to the Imbrium and Serenitatis impact basins, extending to 80 degreesS latitude, show that crustal magnetic fields fill most of the antipodal zones of those basins. This finding provides further evidence for the hypothesis that basin-forming impacts result in magnetization of the lunar crust at their antipodes. The crustal magnetic fields of the Imbrium antipode region are strong enough to deflect the solar wind and form a miniature (100 to several hundred kilometers across) magnetosphere, magnetosheath, and bow shock system. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdSpR..61..617S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdSpR..61..617S">Model of a fluxtube with a twisted magnetic field in the stratified solar atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sen, S.; Mangalam, A. 2018-01-01 We build a single vertical straight magnetic fluxtube spanning the solar photosphere and the transition region which does not expand with height. We assume that the fluxtube containing twisted magnetic fields is in magnetohydrostatic equilibrium within a realistic stratified atmosphere subject to solar gravity. Incorporating specific forms of current density and gas pressure in the Grad-Shafranov equation, we solve the magnetic flux function, and find it to be separable with a Coulomb wave function in radial direction while the vertical part of the solution decreases exponentially. We employ improved fluxtube boundary conditions and take a realistic ambient external pressure for the photosphere to transition region, to derive a family of solutions for reasonable values of the fluxtube radius and magnetic field strength at the base of the axis that are the free parameters in our model. We find that our model estimates are consistent with the magnetic field strength and the radii of Magnetic bright points (MBPs) as estimated from observations. We also derive thermodynamic quantities inside the fluxtube. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..12110520C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..12110520C">Changes in solar quiet magnetic variations since the Maunder Minimum: A comparison of historical observations and model simulations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cnossen, Ingrid; Matzka, Jürgen 2016-10-01 Magnetic measurements going back to the eighteenth century offer a unique opportunity to study multicentennial changes in the upper atmosphere. We analyzed measurements from Rome and Mannheim from May 1782 to May 1783 and measurements from Greenwich, St. Helena, Cape of Good Hope, and Singapore from May 1841 to May 1842. A comparison of the daily magnetic variations in these historical data with modern-day observations from 2010 at nearby stations (where available) showed notable differences in the amplitude and/or phase of the X and Y components. Model simulations indicated that these can be explained at least to some extent by changes in the Earth's main magnetic field. Changes in the main field strength and the northwestward movement of the magnetic equator, in particular in the region of the South Atlantic Anomaly, have caused changes in the positioning, shape, and strength of the equivalent current vortices in the ionosphere that result in the magnetic perturbations on the ground. Differences in solar activity between the historical and modern epochs, which were all near solar minima, were too small to have a notable effect on the ground magnetic perturbations. However, in regions where main magnetic field changes have been relatively small for the last 400 years, e.g., in Singapore, the effects of a long-term increase in solar activity from Maunder Minimum conditions to normal solar minimum conditions (an increase in F10.7 of 35 solar flux units) were comparable to the effects of geomagnetic main field changes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22493833-transport-solar-electrons-turbulent-interplanetary-magnetic-field','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22493833-transport-solar-electrons-turbulent-interplanetary-magnetic-field">Transport of solar electrons in the turbulent interplanetary magnetic field</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Ablaßmayer, J.; Tautz, R. C., E-mail: robert.c.tautz@gmail.com; Dresing, N., E-mail: dresing@physik.uni-kiel.de 2016-01-15 The turbulent transport of solar energetic electrons in the interplanetary magnetic field is investigated by means of a test-particle Monte-Carlo simulation. The magnetic fields are modeled as a combination of the Parker field and a turbulent component. In combination with the direct calculation of diffusion coefficients via the mean-square displacements, this approach allows one to analyze the effect of the initial ballistic transport phase. In that sense, the model complements the main other approach in which a transport equation is solved. The major advancement is that, by recording the flux of particles arriving at virtual detectors, intensity and anisotropy-time profilesmore » can be obtained. Observational indications for a longitudinal asymmetry can thus be explained by tracing the diffusive spread of the particle distribution. The approach may be of future help for the systematic interpretation of observations for instance by the solar terrestrial relations observatory (STEREO) and advanced composition explorer (ACE) spacecrafts.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21464720-intermittency-multifractality-spectra-magnetic-field-solar-active-regions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21464720-intermittency-multifractality-spectra-magnetic-field-solar-active-regions">INTERMITTENCY AND MULTIFRACTALITY SPECTRA OF THE MAGNETIC FIELD IN SOLAR ACTIVE REGIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Abramenko, Valentyna; Yurchyshyn, Vasyl We present the results of a study of intermittency and multifractality of magnetic structures in solar active regions (ARs). Line-of-sight magnetograms for 214 ARs of different flare productivity observed at the center of the solar disk from 1997 January until 2006 December are utilized. Data from the Michelson Doppler Imager (MDI) instrument on board the Solar and Heliospheric Observatory operating in the high resolution mode, the Big Bear Solar Observatory digital magnetograph, and the Hinode SOT/SP instrument were used. Intermittency spectra were derived from high-order structure functions and flatness functions. The flatness function exponent is a measure of the degreemore » of intermittency. We found that the flatness function exponent at scales below approximately 10 Mm is correlated with flare productivity (the correlation coefficient is -0.63). The Hinode data show that the intermittency regime is extended toward small scales (below 2 Mm) as compared to the MDI data. The spectra of multifractality, derived from the structure functions and flatness functions, are found to be broader for ARs of higher flare productivity as compared to those of low flare productivity. The magnetic structure of high-flaring ARs consists of a voluminous set of monofractals, and this set is much richer than that for low-flaring ARs. The results indicate the relevance of the multifractal organization of the photospheric magnetic fields to the flaring activity. The strong intermittency observed in complex and high-flaring ARs is a hint that we observe a photospheric imprint of enhanced sub-photospheric dynamics.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH11B2444S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH11B2444S">Kinetic-Scale Electric and Magnetic Field Fluctuations in the Solar Wind at 1 AU: THEMIS/ARTEMIS Observations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Salem, C. S.; Hanson, E.; Bonnell, J. W.; Chaston, C. C.; Bale, S. D.; Mozer, F. 2017-12-01 We present here an analysis of kinetic-scale electromagnetic fluctuations in the solar wind using data from THEMIS and ARTEMIS spacecraft. We use high-time resolution electric and magnetic field measurements, as well as density fluctuations, up to 128 samples per second, as well as particle burst plasma data during carefully selected solar wind intervals. We focus our analysis on a few such intervals spanning different values of plasma beta and angles between the local magnetic field and the radial Sun-Earth direction. We discuss the careful analysis process of characterizing and removing the different instrumental effects and noise sources affecting the electric and magnetic field data at those scales, above 0.1 Hz or so, above the breakpoint marking the start of the so-called dissipation range of solar wind turbulence. We compute parameters such as the electric to magnetic field ratio, the magnetic compressibility, magnetic helicity, and other relevant quantities in order to diagnose the nature of the fluctuations at those scales between the ion and electron cyclotron frequencies, extracting information on the dominant modes composing the fluctuations. We also discuss the presence and role of coherent structures in the measured fluctuations. The nature of the fluctuations in the dissipation or dispersive scales of solar wind turbulence is still debated. This observational study is also highly relevant to the current Turbulent Dissipation Challenge. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PPCF...56f4008E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PPCF...56f4008E">On the signatures of magnetic islands and multiple X-lines in the solar wind as observed by ARTEMIS and WIND</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Eriksson, S.; Newman, D. L.; Lapenta, G.; Angelopoulos, V. 2014-06-01 We report the first observation consistent with a magnetic reconnection generated magnetic island at a solar wind current sheet that was observed on 10 June 2012 by the two ARTEMIS satellites and the upstream WIND satellite. The evidence consists of a core magnetic field within the island which is formed by enhanced Hall magnetic fields across a solar wind reconnection exhaust. The core field at ARTEMIS displays a local dip coincident with a peak plasma density enhancement and a locally slower exhaust speed which differentiates it from a regular solar wind exhaust crossing. Further indirect evidence of magnetic island formation is presented in the form of a tripolar Hall magnetic field, which is supported by an observed electron velocity shear, and plasma density depletion regions which are in general agreement with multiple reconnection X-line signatures at the same current sheet on the basis of predicted signatures of magnetic islands as generated by a kinetic reconnection simulation for solar wind-like conditions. The combined ARTEMIS and WIND observations of tripolar Hall magnetic fields across the same exhaust and Grad-Shrafranov reconstructions of the magnetic field suggest that an elongated magnetic island was encountered which displayed a 4RE normal width and a 43RE extent along the exhaust between two neighboring X-lines. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930036990&hterms=surface+equipotential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsurface%2Bequipotential','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930036990&hterms=surface+equipotential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsurface%2Bequipotential">A scenario for solar wind penetration of earth's magnetic tail based on ion composition data from the ISEE 1 spacecraft</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Lennartsson, W. 1992-01-01 Based on He(2+) and H(-) ion composition data from the Plasma Composition Experiment on ISEE 1, a scenario is proposed for the solar wind penetration of the earth's magnetic tail, which does not require that the solar wind plasma be magnetized. While this study does not take issue with the notion that earth's magnetic field merges with the solar wind magnetic field on a regular basis, it focuses on certain aspects of interaction between the solar wind particles and the earth's field, e.g, the fact that the geomagnetic tail always has a plasma sheet, even during times when the physical signs of magnetic merging are weak or absent. It is argued that the solar plasma enters along slots between the tail lobes and the plasma sheet, even quite close to earth, convected inward along the plasma sheet boundary layer or adjacent to it, by the electric fringe field of the ever present low-latitude magnetopause boundary layer (LLBL). The required E x B drifts are produced by closing LLBL equipotential surfaces through the plasma sheet. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654221-solar-multiple-eruptions-from-confined-magnetic-structure','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654221-solar-multiple-eruptions-from-confined-magnetic-structure">SOLAR MULTIPLE ERUPTIONS FROM A CONFINED MAGNETIC STRUCTURE</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Lee, Jeongwoo; Chae, Jongchul; Liu, Chang 2016-09-20 How eruption can recur from a confined magnetic structure is discussed based on the Solar Dynamics Observatory observations of the NOAA active region 11444, which produced three eruptions within 1.5 hr on 2012 March 27. The active region (AR) had the positive-polarity magnetic fields in the center surrounded by the negative-polarity fields around. Since such a distribution of magnetic polarity tends to form a dome-like magnetic fan structure confined over the AR, the multiple eruptions were puzzling. Our investigation reveals that this event exhibits several properties distinct from other eruptions associated with magnetic fan structures: (i) a long filament encirclingmore » the AR was present before the eruptions; (ii) expansion of the open–closed boundary (OCB) of the field lines after each eruption was suggestive of the growing fan-dome structure, and (iii) the ribbons inside the closed magnetic polarity inversion line evolved in response to the expanding OCB. It thus appears that in spite of multiple eruptions the fan-dome structure remained undamaged, and the closing back field lines after each eruption rather reinforced the fan-dome structure. We argue that the multiple eruptions could occur in this AR in spite of its confined magnetic structure because the filament encircling the AR was adequate for slipping through the magnetic separatrix to minimize the damage to its overlying fan-dome structure. The result of this study provides a new insight into the productivity of eruptions from a confined magnetic structure.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010068927&hterms=Mass+standards&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DMass%2Bstandards','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010068927&hterms=Mass+standards&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DMass%2Bstandards">Onset of the Magnetic Explosion in Solar Flames and Coronal Mass Ejections</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Moore, Ronald L.; Sterling, Alphonse C.; Hudson, Hugh S.; Lemen, James R. 2001-01-01 We present observations of the magnetic field configuration and its transformation in six solar eruptive events that show good agreement with the standard bipolar model for eruptive flares. The observations are X-ray images from the Yohkoh soft X-ray telescope (SXT) and magnetograms from Kitt Peak National Solar Observatory, interpreted together with the 1-8 Angstrom X-ray flux observed by Geostationary Operational Environmental Satellites (GOES). The observations yield the following interpretations: (1) Each event is a magnetic explosion that occurs in an initially closed single bipole in which the core field is sheared and twisted in the shape of a sigmoid, having an oppositely curved elbow on each end. The arms of the opposite elbows are sheared past each other so that they overlap and are crossed low above the neutral line in the middle of the bipole. The elbows and arms seen in the SXT images are illuminated strands of the sigmoidal core field, which is a continuum of sheared/twisted field that fills these strands as well as the space between and around them; (2) Although four of the explosions are ejective (appearing to blow open the bipole) and two are confined (appearing to be arrested within the closed bipole), all six begin the same way. In the SXT images, the explosion begins with brightening and expansion of the two elbows together with the appearance of short bright sheared loops low over the neutral line under the crossed arms and, rising up from the crossed arms, long strands connecting the far ends of the elbows; and (3) All six events are single-bipole events in that during the onset and early development of the explosion they show no evidence for reconnection between the exploding bipole and any surrounding magnetic fields. We conclude that in each of our events the magnetic explosion was unleashed by runaway tether-cutting via implosive/explosive reconnection in the middle of the sigmoid, as in the standard model. The similarity of the onsets of </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21452870-distribution-magnetic-bipoles-sun-over-three-solar-cycles','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21452870-distribution-magnetic-bipoles-sun-over-three-solar-cycles">DISTRIBUTION OF MAGNETIC BIPOLES ON THE SUN OVER THREE SOLAR CYCLES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Tlatov, Andrey G.; Vasil'eva, Valerya V.; Pevtsov, Alexei A., E-mail: tlatov@mail.r, E-mail: apevtsov@nso.ed We employ synoptic full disk longitudinal magnetograms to study latitudinal distribution and orientation (tilt) of magnetic bipoles in the course of sunspot activity during cycles 21, 22, and 23. The data set includes daily observations from the National Solar Observatory at Kitt Peak (1975-2002) and Michelson Doppler Imager on board the Solar and Heliospheric Observatory (MDI/SOHO, 1996-2009). Bipole pairs were selected on the basis of proximity and flux balance of two neighboring flux elements of opposite polarity. Using the area of the bipoles, we have separated them into small quiet-Sun bipoles (QSBs), ephemeral regions (ERs), and active regions (ARs). Wemore » find that in their orientation, ERs and ARs follow Hale-Nicholson polarity rule. As expected, AR tilts follow Joy's law. ERs, however, show significantly larger tilts of opposite sign for a given hemisphere. QSBs are randomly oriented. Unlike ARs, ERs also show a preference in their orientation depending on the polarity of the large-scale magnetic field. These orientation properties may indicate that some ERs may form at or near the photosphere via the random encounter of opposite polarity elements, while others may originate in the convection zone at about the same location as ARs. The combined latitudinal distribution of ERs and ARs exhibits a clear presence of Spoerer's butterfly diagram (equatorward drift in the course of a solar cycle). ERs extend the ARs' 'wing' of the butterfly diagram to higher latitudes. This high latitude extension of ERs suggests an extended solar cycle with the first magnetic elements of the next cycle developing shortly after the maximum of the previous cycle. The polarity orientation and tilt of ERs may suggest the presence of poloidal fields of two configurations (new cycle and old cycle) in the convection zone at the declining phase of the sunspot cycle.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820043852&hterms=fossils&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dfossils','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820043852&hterms=fossils&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dfossils">Oscillating dynamo in the presence of a fossil magnetic field - The solar cycle</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Levy, E. H.; Boyer, D. 1982-01-01 Hydromagnetic dynamo generation of oscillating magnetic fields in the presence of an external, ambient magnetic field introduces a marked polarity asymmetry between the two halves of the magnetic cycle. The principle of oscillating dynamo interaction with external fields is developed, and a tentative application to the sun is described. In the sun a dipole moment associated with the stable fluid beneath the convection zone would produce an asymmetrical solar cycle. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SoPh..292...82L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SoPh..292...82L">EUV and Magnetic Activities Associated with Type-I Solar Radio Bursts</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, C. Y.; Chen, Y.; Wang, B.; Ruan, G. P.; Feng, S. W.; Du, G. H.; Kong, X. L. 2017-06-01 Type-I bursts ( i.e. noise storms) are the earliest-known type of solar radio emission at the meter wavelength. They are believed to be excited by non-thermal energetic electrons accelerated in the corona. The underlying dynamic process and exact emission mechanism still remain unresolved. Here, with a combined analysis of extreme ultraviolet (EUV), radio and photospheric magnetic field data of unprecedented quality recorded during a type-I storm on 30 July 2011, we identify a good correlation between the radio bursts and the co-spatial EUV and magnetic activities. The EUV activities manifest themselves as three major brightening stripes above a region adjacent to a compact sunspot, while the magnetic field there presents multiple moving magnetic features (MMFs) with persistent coalescence or cancelation and a morphologically similar three-part distribution. We find that the type-I intensities are correlated with those of the EUV emissions at various wavelengths with a correlation coefficient of 0.7 - 0.8. In addition, in the region between the brightening EUV stripes and the radio sources there appear consistent dynamic motions with a series of bi-directional flows, suggesting ongoing small-scale reconnection there. Mainly based on the induced connection between the magnetic motion at the photosphere and the EUV and radio activities in the corona, we suggest that the observed type-I noise storms and the EUV brightening activities are the consequence of small-scale magnetic reconnection driven by MMFs. This is in support of the original proposal made by Bentley et al. ( Solar Phys. 193, 227, 2000). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011A%26A...531A...6V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011A%26A...531A...6V">Evolution of the solar irradiance during the Holocene</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vieira, L. E. A.; Solanki, S. K.; Krivova, N. A.; Usoskin, I. 2011-07-01 Context. Long-term records of solar radiative output are vital for understanding solar variability and past climate change. Measurements of solar irradiance are available for only the last three decades, which calls for reconstructions of this quantity over longer time scales using suitable models. Aims: We present a physically consistent reconstruction of the total solar irradiance for the Holocene. Methods: We extend the SATIRE (Spectral And Total Irradiance REconstruction) models to estimate the evolution of the total (and partly spectral) solar irradiance over the Holocene. The basic assumption is that the variations of the solar irradiance are due to the evolution of the dark and bright magnetic features on the solar surface. The evolution of the decadally averaged magnetic flux is computed from decadal values of cosmogenic isotope concentrations recorded in natural archives employing a series of physics-based models connecting the processes from the modulation of the cosmic ray flux in the heliosphere to their record in natural archives. We then compute the total solar irradiance (TSI) as a linear combination of the jth and jth + 1 decadal values of the open magnetic flux. In order to evaluate the uncertainties due to the evolution of the Earth's magnetic dipole moment, we employ four reconstructions of the open flux which are based on conceptually different paleomagnetic models. Results: Reconstructions of the TSI over the Holocene, each valid for a different paleomagnetic time series, are presented. Our analysis suggests that major sources of uncertainty in the TSI in this model are the heritage of the uncertainty of the TSI since 1610 reconstructed from sunspot data and the uncertainty of the evolution of the Earth's magnetic dipole moment. The analysis of the distribution functions of the reconstructed irradiance for the last 3000 years, which is the period that the reconstructions overlap, indicates that the estimates based on the virtual axial dipole </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM12A..06M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM12A..06M">Asymmetric Magnetic Reconnection in the Solar Atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Murphy, N. A.; Miralles, M. P.; Ranquist, D. A.; Pope, C. L.; Raymond, J. C.; Lukin, V. S.; McKillop, S.; Shen, C.; Winter, H. D.; Reeves, K. K.; Lin, J. 2013-12-01 Models of solar flares and coronal mass ejections typically predict the development of an elongated current sheet in the wake behind the rising flux rope. In reality, reconnection in these current sheets will be asymmetric along the inflow, outflow, and out-of-plane directions. We perform resistive MHD simulations to investigate the consequences of asymmetry during solar reconnection. We predict several observational signatures of asymmetric reconnection, including flare loops with a skewed candle flame shape, slow drifting of the current sheet into the strong field upstream region, asymmetric footpoint speeds and hard X-ray emission, and rolling motions within the erupting flux rope. There is net plasma flow across the magnetic field null along both the inflow and outflow directions. We compare simulations to SDO/AIA, Hinode/XRT, and STEREO observations of flare loop shapes, current sheet drifting, and rolling motions during prominence eruptions. Simulations of the plasmoid instability with different upstream magnetic fields show that the reconnection rate remains enhanced even during the asymmetric case. The islands preferentially grow into the weak field upstream region. The islands develop net vorticity because the outflow jets impact them obliquely rather than directly. Asymmetric reconnection in the chromosphere occurs when emerging flux interacts with pre-existing overlying flux. We present initial results on asymmetric reconnection in partially ionized chromospheric plasmas. Finally, we discuss how comparisons to observations are necessary to understand the role of three-dimensional effects. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM12A0006M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM12A0006M">Asymmetric Magnetic Reconnection in the Solar Atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Murphy, N. A.; Miralles, M. P.; Ranquist, D. A.; Pope, C. L.; Raymond, J. C.; Lukin, V. S.; McKillop, S. C.; Shen, C.; Winter, H. D.; Reeves, K. K.; Lin, J. 2013-12-01 Models of solar flares and coronal mass ejections typically predict the development of an elongated current sheet in the wake behind the rising flux rope. In reality, reconnection in these current sheets will be asymmetric along the inflow, outflow, and out-of-plane directions. We perform resistive MHD simulations to investigate the consequences of asymmetry during solar reconnection. We predict several observational signatures of asymmetric reconnection, including flare loops with a skewed candle flame shape, slow drifting of the current sheet into the strong field upstream region, asymmetric footpoint speeds and hard X-ray emission, and rolling motions within the erupting flux rope. There is net plasma flow across the magnetic field null along both the inflow and outflow directions. We compare simulations to SDO/AIA, Hinode/XRT, and STEREO observations of flare loop shapes, current sheet drifting, and rolling motions during prominence eruptions. Simulations of the plasm! oid instability with different upstream magnetic fields show that the reconnection rate remains enhanced even during the asymmetric case. The islands preferentially grow into the weak field upstream region. The islands develop net vorticity because the outflow jets impact them obliquely rather than directly. Asymmetric reconnection in the chromosphere occurs when emerging flux interacts with pre-existing overlying flux. We present initial results on asymmetric reconnection in partially ionized chromospheric plasmas. Finally, we discuss how comparisons to observations are necessary to understand the role of three-dimensional effects. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017IAUS..327...67P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017IAUS..327...67P">Photospheric magnetic field of an eroded-by-solar-wind coronal mass ejection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Palacios, J.; Cid, C.; Saiz, E.; Guerrero, A. 2017-10-01 We have investigated the case of a coronal mass ejection that was eroded by the fast wind of a coronal hole in the interplanetary medium. When a solar ejection takes place close to a coronal hole, the flux rope magnetic topology of the coronal mass ejection (CME) may become misshapen at 1 AU as a result of the interaction. Detailed analysis of this event reveals erosion of the interplanetary coronal mass ejection (ICME) magnetic field. In this communication, we study the photospheric magnetic roots of the coronal hole and the coronal mass ejection area with HMI/SDO magnetograms to define their magnetic characteristics. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMSH51A1458M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMSH51A1458M">A model for the behaviour of the Solar Energetic Particle Events inside Magnetic Clouds</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Medina, J.; Hidalgo, M. A. 2006-12-01 The modulation effects of the solar ejecta over the solar energetic particle event SEPe fluxes (0,5-100 MeV) provided by solar flares have recently been highlighted. Especially important is the behaviour of these fluxes inside MCs where, in spite of the low magnetic field intensities of these interplanetary structures (about 30 nT), a decrease in the population of the energetic particles is observed. In the present work it is shown a simple theoretical model we have developed to analyse the behaviour of those fluxes inside the magnetic clouds (MCs) using, as a starting point, our previous magnetic field model for MCs. The experimental data from ACE, GOES, SAMPEX, SOHO, Ulysses and WIND satellites are presented, both from MC coincident with SEPe and not coincident. This work has been supported by the Spanish Comisión Internacional de Ciencia y Tecnología (CICYT), grant ESP2005-07290-C02-01 and ESP2006-08459 and Madrid Autonomous Community / University of Alcala grant CAM-UAH 2005/007. This work is performed inside COST Action 724. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5948437-slow-twists-solar-magnetic-flux-tubes-polar-magnetic-field-sun','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5948437-slow-twists-solar-magnetic-flux-tubes-polar-magnetic-field-sun">Slow twists of solar magnetic flux tubes and the polar magnetic field of the sun</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Lee, M.A.; Hollweg, J.V. The solar wind model of Weber and Davis (1967) is generalized to compute the heliospheric magnetic field resulting from solar rotation or a steady axisymmetric twist including a geometrical expansion which is more rapid than spherical. The calculated increase in the ratio of the toroidal to poloidal field components with heliocentric radial distance r clarifies an expression derived recently by Jokipii and Kota (1989). Magnetic field components transverse to r do not in general grow to dominate the radial component at large r. The analysis also yield expressions for the Poynting flux associated with the steady twists. These results aremore » regarded as indicative of the Poynting flux associated with very low frequency Alfven waves, and it is shown how the Poynting flux and the spatial evolution of the wave amplitude differ from the usual WKB result. It is found that the low-frequency Poynting flux at the base of a coronal hole can be about 50 percent larger than the WKB flux inferred from spectral observations of coronal motions (e.g. Hassler et al., 1988).« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011SoPh..269....3R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011SoPh..269....3R">Cross Helicity and Turbulent Magnetic Diffusivity in the Solar Convection Zone</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rüdiger, G.; Kitchatinov, L. L.; Brandenburg, A. 2011-03-01 In a density-stratified turbulent medium, the cross helicity < u'ṡ B'> is considered as a result of the interaction of the velocity fluctuations and a large-scale magnetic field. By means of a quasilinear theory and by numerical simulations, we find the cross helicity and the mean vertical magnetic field to be anti-correlated. In the high-conductivity limit the ratio of the helicity and the mean magnetic field equals the ratio of the magnetic eddy diffusivity and the (known) density scale height. The result can be used to predict that the cross helicity at the solar surface will exceed the value of 1 gauss km s-1. Its sign is anti-correlated to that of the radial mean magnetic field. Alternatively, we can use our result to determine the value of the turbulent magnetic diffusivity from observations of the cross helicity. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667337-role-repetitive-magnetic-reconnections-evolution-magnetic-flux-ropes-solar-corona','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667337-role-repetitive-magnetic-reconnections-evolution-magnetic-flux-ropes-solar-corona">ON THE ROLE OF REPETITIVE MAGNETIC RECONNECTIONS IN EVOLUTION OF MAGNETIC FLUX ROPES IN SOLAR CORONA</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kumar, Sanjay; Bhattacharyya, R.; Joshi, Bhuwan Parker's magnetostatic theorem, extended to astrophysical magnetofluids with large magnetic Reynolds number, supports ceaseless regeneration of current sheets and, hence, spontaneous magnetic reconnections recurring in time. Consequently, a scenario is possible where the repeated reconnections provide an autonomous mechanism governing emergence of coherent structures in astrophysical magnetofluids. In this work, such a scenario is explored by performing numerical computations commensurate with the magnetostatic theorem. In particular, the computations explore the evolution of a flux rope governed by repeated reconnections in a magnetic geometry resembling bipolar loops of solar corona. The revealed morphology of the evolution process—including onset and ascent ofmore » the rope, reconnection locations, and the associated topology of the magnetic field lines—agrees with observations, and thus substantiates physical realizability of the advocated mechanism.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140007405','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140007405">Design and Ground Calibration of the Helioseismic and Magnetic Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Schou, J.; Scherrer, P. H.; Bush, R. I.; Wachter, R.; Couvidat, S.; Rabello-Soares, M. C.; Bogart, R. S.; Hoeksema, J. T.; Liu, Y.; Duvall, T. L., Jr.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140007405'); toggleEditAbsImage('author_20140007405_show'); toggleEditAbsImage('author_20140007405_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140007405_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140007405_hide"> 2012-01-01 The Helioseismic and Magnetic Imager (HMI) investigation will study the solar interior using helioseismic techniques as well as the magnetic field near the solar surface. The HMI instrument is part of the Solar Dynamics Observatory (SDO) that was launched on 11 February 2010. The instrument is designed to measure the Doppler shift, intensity, and vector magnetic field at the solar photosphere using the 6173 Fe I absorption line. The instrument consists of a front-window filter, a telescope, a set of wave plates for polarimetry, an image-stabilization system, a blocking filter, a five-stage Lyot filter with one tunable element, two wide-field tunable Michelson interferometers, a pair of 4096(exo 2) pixel cameras with independent shutters, and associated electronics. Each camera takes a full-disk image roughly every 3.75 seconds giving an overall cadence of 45 seconds for the Doppler, intensity, and line-of-sight magnetic-field measurements and a slower cadence for the full vector magnetic field. This article describes the design of the HMI instrument and provides an overview of the pre-launch calibration efforts. Overviews of the investigation, details of the calibrations, data handling, and the science analysis are provided in accompanying articles. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.P13C..02U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.P13C..02U">Effects of variation in solar conditions and crustal sources' orientation on the Martian magnetic field topology</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ulusen, D.; Luhmann, J. G.; Ma, Y.; Brain, D. A. 2013-12-01 Strong crustal magnetic sources on the surface of Mars directly interact with the solar magnetic field and plasma, resulting a very dynamic environment near the planet. Effects of the orientation of these remnant magnetic sources with respect to the sun and variation of the solar conditions on the Martian plasma interaction have been investigated in a previous paper. In this previous study, magnetic topology maps obtained from ~7 years of Mars Global Surveyor (MGS) directional electron observations (obtained by Dave Brain) were compared with the topology maps obtained from a set of BATS-R-US MHD simulations for Mars. One conclusion from this study was that although the MHD model is consistent with the data and provides insight about the global magnetic field topology variation with changing crustal field orientation and solar parameters, detailed investigation of local effects is difficult due to MGS orbital bias. Moreover, proper comparison of the observations with the model requires more careful data selection rather than using 7 years time averages. In this paper, we readdress the study to tackle the problems of our previous work by performing more detailed data analysis and present the results of the updated model-data comparison. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850002589','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850002589">Structure and evolution of the large scale solar and heliospheric magnetic fields. Ph.D. Thesis</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hoeksema, J. T. 1984-01-01 Structure and evolution of large scale photospheric and coronal magnetic fields in the interval 1976-1983 were studied using observations from the Stanford Solar Observatory and a potential field model. The solar wind in the heliosphere is organized into large regions in which the magnetic field has a componenet either toward or away from the sun. The model predicts the location of the current sheet separating these regions. Near solar minimum, in 1976, the current sheet lay within a few degrees of the solar equator having two extensions north and south of the equator. Soon after minimum the latitudinal extent began to increase. The sheet reached to at least 50 deg from 1978 through 1983. The complex structure near maximum occasionally included multiple current sheets. Large scale structures persist for up to two years during the entire interval. To minimize errors in determining the structure of the heliospheric field particular attention was paid to decreasing the distorting effects of rapid field evolution, finding the optimum source surface radius, determining the correction to the sun's polar field, and handling missing data. The predicted structure agrees with direct interplanetary field measurements taken near the ecliptic and with coronameter and interplanetary scintillation measurements which infer the three dimensional interplanetary magnetic structure. During most of the solar cycle the heliospheric field cannot be adequately described as a dipole. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930062362&hterms=Envision&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DEnvision','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930062362&hterms=Envision&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DEnvision">The thermal structure of the magnetized solar transition region</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Mok, Y.; Van Hoven, G. 1993-01-01 The detailed thermal structure of the magnetized solar transition region, as measured by its differential emission measure DEM(T), is unknown. Proposals have been made that envision a significant lower-temperature contribution to the energy balance from cross-field (ion) heat flux. In this paper, we describe a self-consistent 2D MHD simulation (including the full effects of anisotropic thermal conduction) of a conceptual model due to Athay (1990). We display the detailed irregular thermal and magnetic structure of the transition region and demonstrate that the predicted DEM agrees with observations, particularly in the T less than 10 exp 5 K regime where previous theories had difficulty. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017DPS....4950502D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017DPS....4950502D">The complex magnetic field configuration of the Martian magnetotail as observed by MAVEN</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> DiBraccio, Gina A.; Luhmann, Janet; Curry, Shannon; Espley, Jared R.; Gruesbeck, Jacob; Xu, Shaosui; Mitchell, David; Soobiah, Yasir; Connerney, John E. P.; Dong, Chuanfei; Harada, Yuki; Ruhunusiri, Suranga; Halekas, Jasper; Hara, Takuya; Ma, Yingjuan; Brain, David; Jakosky, Bruce 2017-10-01 The Martian magnetosphere forms as the solar wind directly interacts with the planet’s upper atmosphere. During this interaction, the Sun’s interplanetary magnetic field (IMF) drapes around the planet and local crustal magnetic fields, creating a magnetosphere configuration that has attributes of both an induced magnetosphere like that of Venus, and a complex, small-scale magnetosphere like the Moon. In addition to the closed crustal fields and draped IMF at Mars, open magnetic fields are created when magnetic reconnection occurs between the planetary fields and the IMF. These various field topologies present a complex magnetotail structure that we are now able to explore using a combination of MAVEN observations and magnetohydrodynamic (MHD) simulations. Preliminary MHD results have suggested that the Martian magnetotail includes a dual-lobe component, composed of open crustal fields, enveloped by an induced comet-like tail. These simulated open-field lobes are twisted by roughly 45°, either clockwise or counterclockwise, from the ecliptic plane. This rotation depends on the east-west component of the IMF. We utilize MAVEN Magnetometer and Solar Wind Ion Analyzer (SWIA) measurements collected over two Earth years to analyze the tail magnetic field configuration as a function of IMF direction. Cross-tail views of the average measured magnetic field components directed toward and away from the planet are compared for a variety of solar wind parameters. We find that, in agreement with simulation results, the east-west IMF component strongly affects the magnetotail structure, twisting its sunward-antisunward polarity patterns in response to changing IMF orientation. Through a data-model comparison we are able to infer that regions of open magnetic fields in the tail are likely reconnected crustal fields. Futhermore, these open fields in the tail may contribute to atmospheric escape to space. From this investigation we are able to confirm that the Martian </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150016374','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150016374">Magnetic Untwisting in Solar Jets that Go into the Outer Corona in Polar Coronal Holes</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Moore, Ronald L.; Sterling, Alphonse C.; Falconer, David A. 2014-01-01 We present results from 14 exceptionally high-reaching large solar jets observed in the polar coronal holes. EUV movies from SDO/AIA show that each jet is similar to many other similar-size and smaller jets that erupt in coronal holes, but each is exceptional in that it goes higher than most other jets, so high that it is observed in the outer corona beyond 2.2 R(sub Sun) in images from the SOHO/LASCO/C2 coronagraph. For these high-reaching jets, we find: (1) the front of the jet transits the corona below 2.2 R(sub Sun) at a speed typically several times the sound speed; (2) each jet displays an exceptionally large amount of spin as it erupts; (3) in the outer corona, most jets display oscillatory swaying having an amplitude of a few degrees and a period of order 1 hour. We conclude that these jets are magnetically driven, propose that the driver is a magnetic-untwisting wave that is grossly a large-amplitude (i.e., nonlinear) torsional Alfven wave that is put into the reconnected open magnetic field in the jet by interchange reconnection as the jet erupts, and estimate from the measured spinning and swaying that the magnetic-untwisting wave loses most of its energy in the inner corona below 2.2 R(sub Sun). From these results for these big jets, we reason that the torsional magnetic waves observed in Type-II spicules should dissipate in the corona in the same way and could thereby power much of the coronal heating in coronal holes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006ihy..workE.146S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006ihy..workE.146S">Fast Solar Wind from Slowly Expanding Magnetic Flux Tubes (P54)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Srivastava, A. K.; Dwivedi, B. N. 2006-11-01 aks.astro.itbhu@gmail.com We present an empirical model of the fast solar wind, emanating from radially oriented slowly expanding magnetic flux tubes. We consider a single-fluid, steady state model in which the flow is driven by thermal and non-thermal pressure gradients. We apply a non-Alfvénic energy correction at the coronal base and find that specific relations correlate solar wind speed and non-thermal energy flux with the aerial expansion factor. The results are compared with the previously reported ones. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...840...37P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...840...37P">Magnetohydrodynamic Modeling of Solar Coronal Dynamics with an Initial Non-force-free Magnetic Field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Prasad, A.; Bhattacharyya, R.; Kumar, Sanjay 2017-05-01 The magnetic fields in the solar corona are generally neither force-free nor axisymmetric and have complex dynamics that are difficult to characterize. Here we simulate the topological evolution of solar coronal magnetic field lines (MFLs) using a magnetohydrodynamic model. The simulation is initialized with a non-axisymmetric non-force-free magnetic field that best correlates with the observed vector magnetograms of solar active regions (ARs). To focus on these ideas, simulations are performed for the flaring AR 11283 noted for its complexity and well-documented dynamics. The simulated dynamics develops as the initial Lorentz force pushes the plasma and facilitates successive magnetic reconnections at the two X-type null lines present in the initial field. Importantly, the simulation allows for the spontaneous development of mass flow, unique among contemporary works, that preferentially reconnects field lines at one of the X-type null lines. Consequently, a flux rope consisting of low-lying twisted MFLs, which approximately traces the major polarity inversion line, undergoes an asymmetric monotonic rise. The rise is attributed to a reduction in the magnetic tension force at the region overlying the rope, resulting from the reconnection. A monotonic rise of the rope is in conformity with the standard scenario of flares. Importantly, the simulated dynamics leads to bifurcations of the flux rope, which, being akin to the observed filament bifurcation in AR 11283, establishes the appropriateness of the initial field in describing ARs. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663649-magnetohydrodynamic-modeling-solar-coronal-dynamics-initial-non-force-free-magnetic-field','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663649-magnetohydrodynamic-modeling-solar-coronal-dynamics-initial-non-force-free-magnetic-field">Magnetohydrodynamic Modeling of Solar Coronal Dynamics with an Initial Non-force-free Magnetic Field</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Prasad, A.; Bhattacharyya, R.; Kumar, Sanjay The magnetic fields in the solar corona are generally neither force-free nor axisymmetric and have complex dynamics that are difficult to characterize. Here we simulate the topological evolution of solar coronal magnetic field lines (MFLs) using a magnetohydrodynamic model. The simulation is initialized with a non-axisymmetric non-force-free magnetic field that best correlates with the observed vector magnetograms of solar active regions (ARs). To focus on these ideas, simulations are performed for the flaring AR 11283 noted for its complexity and well-documented dynamics. The simulated dynamics develops as the initial Lorentz force pushes the plasma and facilitates successive magnetic reconnections atmore » the two X-type null lines present in the initial field. Importantly, the simulation allows for the spontaneous development of mass flow, unique among contemporary works, that preferentially reconnects field lines at one of the X-type null lines. Consequently, a flux rope consisting of low-lying twisted MFLs, which approximately traces the major polarity inversion line, undergoes an asymmetric monotonic rise. The rise is attributed to a reduction in the magnetic tension force at the region overlying the rope, resulting from the reconnection. A monotonic rise of the rope is in conformity with the standard scenario of flares. Importantly, the simulated dynamics leads to bifurcations of the flux rope, which, being akin to the observed filament bifurcation in AR 11283, establishes the appropriateness of the initial field in describing ARs.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970022027&hterms=Theory+constraints&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTheory%2Bconstraints','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970022027&hterms=Theory+constraints&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DTheory%2Bconstraints">Solar Nebula Magnetohydrodynamic Dynamos: Kinematic Theory, Dynamical Constraints, and Magnetic Transport of Angular Momentum</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Stepinski, Tomasz F.; Reyes-Ruiz, Mauricio; Vanhala, Harri A. T. 1993-01-01 A hydromagnetic dynamo provides the best mechanism for contemporaneously producing magnetic fields in a turbulent solar nebula. We investigate the solar nebula in the framework of a steady-state accretion disk model and establish the criteria for a viable nebular dynamo. We have found that typically a magnetic gap exists in the nebula, the region where the degree of ionization is too small for the magnetic field to couple to the gas. The location and width of this gap depend on the particular model; the supposition is that gaps cover different parts of the nebula at different evolutionary stages. We have found, from several dynamical constraints, that the generated magnetic field is likely to saturate at a strength equal to equipartition with the kinetic energy of turbulence. Maxwell stress arising from a large-scale magnetic field may significantly influence nebular structure, and Maxwell stress due to small-scale fields can actually dominate other stresses in the inner parts of the nebula. We also argue that the bulk of nebular gas, within the scale height from the midplane, is stable against Balbus-Hawley instability. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJS..236....7H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJS..236....7H">Activity Analyses for Solar-type Stars Observed with Kepler. II. Magnetic Feature versus Flare Activity</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> He, Han; Wang, Huaning; Zhang, Mei; Mehrabi, Ahmad; Yan, Yan; Yun, Duo 2018-05-01 The light curves of solar-type stars present both periodic fluctuation and flare spikes. The gradual periodic fluctuation is interpreted as the rotational modulation of magnetic features on the stellar surface and is used to deduce magnetic feature activity properties. The flare spikes in light curves are used to derive flare activity properties. In this paper, we analyze the light curve data of three solar-type stars (KIC 6034120, KIC 3118883, and KIC 10528093) observed with Kepler space telescope and investigate the relationship between their magnetic feature activities and flare activities. The analysis shows that: (1) both the magnetic feature activity and the flare activity exhibit long-term variations as the Sun does; (2) unlike the Sun, the long-term variations of magnetic feature activity and flare activity are not in phase with each other; (3) the analysis of star KIC 6034120 suggests that the long-term variations of magnetic feature activity and flare activity have a similar cycle length. Our analysis and results indicate that the magnetic features that dominate rotational modulation and the flares possibly have different source regions, although they may be influenced by the magnetic field generated through a same dynamo process. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20180001284','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20180001284">Solar Activity Across the Scales: From Small-Scale Quiet-Sun Dynamics to Magnetic Activity Cycles</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Kitiashvili, Irina N.; Collins, Nancy N.; Kosovichev, Alexander G.; Mansour, Nagi N.; Wray, Alan A. 2017-01-01 Observations as well as numerical and theoretical models show that solar dynamics is characterized by complicated interactions and energy exchanges among different temporal and spatial scales. It reveals magnetic self-organization processes from the smallest scale magnetized vortex tubes to the global activity variation known as the solar cycle. To understand these multiscale processes and their relationships, we use a two-fold approach: 1) realistic 3D radiative MHD simulations of local dynamics together with high resolution observations by IRIS, Hinode, and SDO; and 2) modeling of solar activity cycles by using simplified MHD dynamo models and mathematical data assimilation techniques. We present recent results of this approach, including the interpretation of observational results from NASA heliophysics missions and predictive capabilities. In particular, we discuss the links between small-scale dynamo processes in the convection zone and atmospheric dynamics, as well as an early prediction of Solar Cycle 25. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH13A2466K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH13A2466K">Solar activity across the scales: from small-scale quiet-Sun dynamics to magnetic activity cycles</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kitiashvili, I.; Collins, N.; Kosovichev, A. G.; Mansour, N. N.; Wray, A. A. 2017-12-01 Observations as well as numerical and theoretical models show that solar dynamics is characterized by complicated interactions and energy exchanges among different temporal and spatial scales. It reveals magnetic self-organization processes from the smallest scale magnetized vortex tubes to the global activity variation known as the solar cycle. To understand these multiscale processes and their relationships, we use a two-fold approach: 1) realistic 3D radiative MHD simulations of local dynamics together with high-resolution observations by IRIS, Hinode, and SDO; and 2) modeling of solar activity cycles by using simplified MHD dynamo models and mathematical data assimilation techniques. We present recent results of this approach, including the interpretation of observational results from NASA heliophysics missions and predictive capabilities. In particular, we discuss the links between small-scale dynamo processes in the convection zone and atmospheric dynamics, as well as an early prediction of Solar Cycle 25. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.3046K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.3046K">Radio studies of the magnetic connection between solar particle acceleration sites and the Earth</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Klein, Karl-Ludwig The magnetic connection from the Sun to the Earth is a crucial problem of SEP propagation in space. While the Parker spiral often provides a plausible configuration, there are also examples where simple impulsive SEP events are observed at Earth even when the parent active region is several tens of degrees in heliographic longitude away from the root of the nominal Parker spiral. In previous work radio spectrography and imaging, together with PFSS magnetic field extrapolations from photospheric measurements, have been shown to provide a consistent ex-planation of this observation in terms of open flux tubes that rapidly fan out with inceasing height and connect the root of the Parker spiral at the source surface to the remote solar active region. Other work, however, has challenged this view and concluded that PFSS models often do not provide adequate connections. The problem is re-examined in this contribution. It is shown that at least in several cases the claimed failure of the PFSS model is in fact due to the assumption that high-latitude active regions must connect to the Parker spiral in the ecliptic plane in order that the SEP be able to reach Earth. This means that the PFSS field lines have to care for the particle transport from high to low heliographic latitudes in these events. However, this contribution presents evidence from radio observations from metre to kilometre wavelengths that even when particles leave the Sun towards high ecliptic latitudes, interplan-etary field lines may bend down to the ecliptic between a few solar radii and 1 AU and guide the particles to the vicinity of the Earth. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...828...12V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...828...12V">Comparison of Magnetic Properties in a Magnetic Cloud and Its Solar Source on 2013 April 11-14</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vemareddy, P.; Möstl, C.; Amerstorfer, T.; Mishra, W.; Farrugia, C.; Leitner, M. 2016-09-01 In the context of the Sun-Earth connection of coronal mass ejections and magnetic flux ropes (MFRs), we studied the solar active region (AR) and the magnetic properties of magnetic cloud (MC) event during 2013 April 14-15. We use in situ observations from the Advanced Composition Explorer and source AR measurements from the Solar Dynamics Observatory. The MCs magnetic structure is reconstructed from the Grad-Shafranov method, which reveals a northern component of the axial field with left handed helicity. The MC invariant axis is highly inclined to the ecliptic plane pointing northward and is rotated by 117° with respect to the source region PIL. The net axial flux and current in the MC are comparatively higher than from the source region. Linear force-free alpha distribution (10-7-10-6 m-1) at the sigmoid leg matches the range of twist number in the MC of 1-2 au MFR. The MFR is nonlinear force-free with decreasing twist from the axis (9 turns/au) toward the edge. Therefore, a Gold-Hoyle (GH) configuration, assuming a constant twist, is more consistent with the MC structure than the Lundquist configuration of increasing twist from the axis to boundary. As an indication of that, the GH configuration yields a better fitting to the global trend of in situ magnetic field components, in terms of rms, than the Lundquist model. These cylindrical configurations improved the MC fitting results when the effect of self-similar expansion of MFR was considered. For such twisting behavior, this study suggests an alternative fitting procedure to better characterize the MC magnetic structure and its source region links. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970017210&hterms=Six+Sigma&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DSix%2BSigma','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970017210&hterms=Six+Sigma&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DSix%2BSigma">Solar and Magnetic Attitude Determination for Small Spacecraft</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Woodham, Kurt; Blackman, Kathie; Sanneman, Paul 1997-01-01 During the Phase B development of the NASA New Millennium Program (NMP) Earth Orbiter-1 (EO-1) spacecraft, detailed analyses were performed for on-board attitude determination using the Sun and the Earth's magnetic field. This work utilized the TRMM 'Contingency Mode' as a starting point but concentrated on implementation for a small spacecraft without a high performance mechanical gyro package. The analyses and simulations performed demonstrate a geographic dependence due to diurnal variations in the Earth magnetic field with respect to the Sun synchronous, nearly polar orbit. Sensitivity to uncompensated residual magnetic fields of the spacecraft and field modeling errors is shown to be the most significant obstacle for maximizing performance. Performance has been evaluated with a number of inertial reference units and various mounting orientations for the two-axis Fine Sun Sensors. Attitude determination accuracy using the six state Kalman Filter executing at 2 Hz is approximately 0.2 deg, 3-sigma, per axis. Although EO-1 was subsequently driven to a stellar-based attitude determination system as a result of tighter pointing requirements, solar/magnetic attitude determination is demonstrated to be applicable to a range of small spacecraft with medium precision pointing requirements. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930067661&hterms=background+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbackground%2Bwind','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930067661&hterms=background+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dbackground%2Bwind">Dynamics of aging magnetic clouds. [interacted with solar wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Osherovich, V. A.; Farrugia, C. J.; Burlaga, L. F. 1993-01-01 The dynamics of radially expanding magnetic clouds is rigorously analyzed within the framework of ideal MHD. The cloud is modelled as a cylindrically symmetric magnetic flux rope. In the force balance we include the gas pressure gradient and the Lorentz force. Interaction with the ambient solar wind due to expansion of the magnetic cloud is represented by a drag force proportional to the bulk velocity. We consider the self-similar expansion of a polytrope, and reduce the problem to an ordinary nonlinear differential equation for the evolution function. Analyzing the asymptotic behavior of the evolution function, we formulate theoretical expectations for the long-term behavior of cloud parameters. We focus on the temporal evolution of (1) the magnetic field strength; (2) the twist of the field lines; (3) the asymmetry of the total field profile; and (4) the bulk flow speed. We present data from two magnetic clouds observed at 1 AU and 2 AU, respectively, and find good agreement with theoretical expectations. For a peak magnetic field strength at 1 AU of 25 nT and a polytropic index of 0.5, we find that a magnetic cloud can be distinguished from the background interplanetary field up to a distance of about 5 AU. Taking larger magnetic fields and bigger polytropic indices this distance can double. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170010257','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170010257">Flux Cancelation: The Key to Solar Eruptions</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald; Chakrapani, Prithi; Innes, Davina; Schmit, Don; Tiwari, Sanjiv 2017-01-01 Solar coronal jets are magnetically channeled eruptions that occur in all types of solar environments (e.g. active regions, quiet-Sun regions and coronal holes). Recent studies show that coronal jets are driven by the eruption of small-scare filaments (minifilaments). Once the eruption is underway magnetic reconnection evidently makes the jet spire and the bright emission in the jet base. However, the triggering mechanism of these eruptions and the formation mechanism of the pre-jet minifilaments are still open questions. In this talk, mainly using SDO/AIA (Solar Dynamics Observatory / Atmospheric Imaging Assembly) and SDO/HIM (Solar Dynamics Observatory / Helioseismic and Magnetic Imager) data, first I will address the question: what triggers the jet-driving minifilament eruptions in different solar environments (coronal holes, quiet regions, active regions)? Then I will talk about the magnetic field evolution that produces the pre-jet minifilaments. By examining pre-jet evolutionary changes in line-of-sight HMI magnetograms while examining concurrent EUV (Extreme Ultra-Violet) images of coronal and transition-region emission, we find clear evidence that flux cancelation is the main process that builds pre-jet minifilaments, and is also the main process that triggers the eruptions. I will also present results from our ongoing work indicating that jet-driving minifilament eruptions are analogous to larger-scare filament eruptions that make flares and CMEs (Coronal Mass Ejections). We find that persistent flux cancellation at the neutral line of large-scale filaments often triggers their eruptions. From our observations we infer that flux cancelation is the fundamental process from the buildup and triggering of solar eruptions of all sizes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1364611-open-problems-magnetic-island-control-electron-cyclotron-current-drive','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1364611-open-problems-magnetic-island-control-electron-cyclotron-current-drive">Open problems of magnetic island control by electron cyclotron current drive</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Grasso, Daniela; Lazzaro, E.; Borgogno, D.; ... 2016-11-17 This study reviews key aspects of the problem of magnetic islands control by electron cyclotron current drive in fusion devices. On the basis of the ordering of the basic spatial and time scales of the magnetic reconnection physics, we present the established results, highlighting some of the open issues posed by the small-scale structures that typically accompany the nonlinear evolution of the magnetic islands and constrain the effect of the control action. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840005037','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840005037">The average solar wind in the inner heliosphere: Structures and slow variations</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Schwenn, R. 1983-01-01 Measurements from the HELIOS solar probes indicated that apart from solar activity related disturbances there exist two states of the solar wind which might result from basic differences in the acceleration process: the fast solar wind (v 600 kms(-)1) emanating from magnetically open regions in the solar corona and the "slow" solar wind (v 400 kms(-)1) correlated with the more active regions and its mainly closed magnetic structures. In a comprehensive study using all HELIOS data taken between 1974 and 1982 the average behavior of the basic plasma parameters were analyzed as functions of the solar wind speed. The long term variations of the solar wind parameters along the solar cycle were also determined and numerical estimates given. These modulations appear to be distinct though only minor. In agreement with earlier studies it was concluded that the major modulations are in the number and size of high speed streams and in the number of interplanetary shock waves caused by coronal transients. The latter ones usually cause huge deviations from the averages of all parameters. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM43A..07E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM43A..07E">Sub-solar Magnetopause Observation and Simulation of a Tripolar Guide-Magnetic Field Perturbation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Eriksson, S.; Cassak, P.; Retino, A.; Mozer, F. 2015-12-01 The Polar satellite recorded two reconnection exhausts within 6 min on 1 April 2001 at a rather symmetric sub-solar magnetopause that displayed different out-of-plane signatures for similar solar wind conditions. The first case was reported by Mozer et al. [2002] and displayed a bipolar guide field supporting a quadrupole Hall field consistent with a single X-line. The second case, however, shows the first known example of a tripolar guide-field perturbation at Earth's magnetopause reminiscent of the types of solar wind exhausts that Eriksson et al. [2014; 2015] have reported to be in agreement with multiple X-lines. A dedicated particle-in-cell simulation is performed for the prevailing conditions across the magnetopause. We propose an explanation in terms of asymmetric Hall magnetic fields due to a presence of a magnetic island between two X-lines, and discuss how higher resolution MMS observations can be used to further study this problem at the magnetopause. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.A12D..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.A12D..07S">Integration of Ground-Based Solar FT-IR Absorption Spectroscopy and Open-Path Systems for Atmospheric Analysis</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Steill, J. D.; Hager, J. S.; Compton, R. N. 2005-12-01 Air quality issues in the Knoxville and East Tennessee region are of great concern, particularly as regards the nearby Great Smoky Mountains National Park. Integration of a Bomem DA8 FT-IR spectrometer with rooftop sun-tracking optics and an open-path system provides a unique opportunity to analyze the local atmospheric chemical composition. Many trace atmospheric constituents are open to this analysis, such as O3, CO, CH4, and N2O. Boundary layer concentrations as well as total column abundances and vertical concentration profiles are derived. Vertical concentration profiles are determined by fitting solar absorbance lines with the SFIT2 algorithm. Improved fitting of solar spectra has been demonstrated by incorporating the tropospheric concentrations as determined by open-path measurements. In addition to providing a means to improve the analysis of solar spectra, the open-path data is useful for elucidation of diurnal trends in the trace gas concentrations. Anthropogenic influences are of special interest, and seasonal and daily trends in amounts of tropospheric pollutants such as ozone correlate with other sources such as the EPA. Although obviously limited by weather considerations, the technique is suited to the regional climate and a body of data of more than two years extent is available for analysis. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SoPh..292..120K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SoPh..292..120K">The Relation Between Magnetic Fields and X-ray Emission for Solar Microflares and Active Regions</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kirichenko, A. S.; Bogachev, S. A. 2017-09-01 We present the result of a comparison between magnetic field parameters and the intensity of X-ray emission for solar microflares with Geosynchronous Operational Environmental Satellites (GOES) classes from A0.02 to B5.1. For our study, we used the monochromatic MgXII Imaging Spectroheliometer (MISH), the Full-disk EUV Telescope (FET), and the Solar PHotometer in X-rays (SphinX) instruments onboard the Complex Orbital Observations Near-Earth of Activity of the Sun-Photon CORONAS- Photon spacecraft because of their high sensitivity in soft X-rays. The peak flare flux (PFF) for solar microflares was found to depend on the strength of the magnetic field and on the total unsigned magnetic flux as a power-law function. In the spectral range 2.8 - 36.6 Å, which shows very little increase related to microflares, the power-law index of the relation between the X-ray flux and magnetic flux for active regions is 1.48 ±0.86, which is close to the value obtained previously by Pevtsov et al. ( Astrophys. J. 598, 1387, 2003) for different types of solar and stellar objects. In the spectral range 1 - 8 Å, the power-law indices for PFF(B) and PFF(Φ) for microflares are 3.87 ±2.16 and 3 ±1.6, respectively. We also make suggestions on the heating mechanisms in active regions and microflares under the assumption of loops with constant pressure and heating using the Rosner-Tucker-Vaiana scaling laws. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JMagR.208...27W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JMagR.208...27W">A portable Halbach magnet that can be opened and closed without force: The NMR-CUFF</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Windt, Carel W.; Soltner, Helmut; Dusschoten, Dagmar van; Blümler, Peter 2011-01-01 Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5 mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017A%26A...601A..47B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017A%26A...601A..47B">Confinement of the solar tachocline by a cyclic dynamo magnetic field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Barnabé, Roxane; Strugarek, Antoine; Charbonneau, Paul; Brun, Allan Sacha; Zahn, Jean-Paul 2017-05-01 Context. The surprising thinness of the solar tachocline is still not understood with certainty today. Among the numerous possible scenarios suggested to explain its radial confinement, one hypothesis is based on Maxwell stresses that are exerted by the cyclic dynamo magnetic field of the Sun penetrating over a skin depth below the turbulent convection zone. Aims: Our goal is to assess under which conditions (turbulence level in the tachocline, strength of the dynamo-generated field, spreading mechanism) this scenario can be realized in the solar tachocline. Methods: We develop a simplified 1D model of the upper tachocline under the influence of an oscillating magnetic field imposed from above. The turbulent transport is parametrized with enhanced turbulent diffusion (or anti-diffusion) coefficients. Two main processes that thicken the tachocline are considered; either turbulent viscous spreading or radiative spreading. An extensive parameter study is carried out to establish the physical parameter regimes under which magnetic confinement of the tachocline that is due to a surface dynamo field can be realized. Results: We have explored a large range of magnetic field amplitudes, viscosities, ohmic diffusivities and thermal diffusivities. We find that, for large but still realistic magnetic field strengths, the differential rotation can be suppressed in the upper radiative zone (and hence the tachocline confined) if weak turbulence is present (with an enhanced ohmic diffusivity of η> 107-8 cm2/ s), even in the presence of radiative spreading. Conclusions: Our results show that a dynamo magnetic field can, in the presence of weak turbulence, prevent the inward burrowing of a tachocline subject to viscous diffusion or radiative spreading. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ApJ...796...72J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ApJ...796...72J">Five-minute Oscillation Power within Magnetic Elements in the Solar Atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jain, Rekha; Gascoyne, Andrew; Hindman, Bradley W.; Greer, Benjamin 2014-12-01 It has long been known that magnetic plage and sunspots are regions in which the power of acoustic waves is reduced within the photospheric layers. Recent observations now suggest that this suppression of power extends into the low chromosphere and is also present in small magnetic elements far from active regions. In this paper we investigate the observed power suppression in plage and magnetic elements, by modeling each as a collection of vertically aligned magnetic fibrils and presuming that the velocity within each fibril is the response to buffeting by incident p modes in the surrounding field-free atmosphere. We restrict our attention to modeling observations made near the solar disk center, where the line-of-sight velocity is nearly vertical and hence, only the longitudinal component of the motion within the fibril contributes. Therefore, we only consider the excitation of axisymmetric sausage waves and ignore kink oscillations as their motions are primarily horizontal. We compare the vertical motion within the fibril with the vertical motion of the incident p mode by constructing the ratio of their powers. In agreement with observational measurements we find that the total power is suppressed within strong magnetic elements for frequencies below the acoustic cut-off frequency. However, further physical effects need to be examined for understanding the observed power ratios for stronger magnetic field strengths and higher frequencies. We also find that the magnitude of the power deficit increases with the height above the photosphere at which the measurement is made. Furthermore, we argue that the area of the solar disk over which the power suppression extends increases as a function of height. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA616953','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA616953">Exploiting the Magnetic Origin of Solar Activity in Forecasting Thermospheric Density Variations</a> <a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a> 2014-09-01 computed daily sums of Φr integrated over the disk using synoptic maps from both MDI and the Helioseismic and Magnetic Imager ( HMI ) on the Solar Dynamics...generally well understood, making a proxy derived from measured magnetic fields potentially much easier 2010 2011 2012 2013 2014 0 1 2 3 HMI /SDO Φ r (1...200 250 300 F10.7 0 1 2 3 Φ r (1 02 3 M X ) r = 0.90 Figure 5: The same as Fig. 4, but for Φr derived from HMI observations of the magnetic field </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667275-stellar-magnetic-cycles-solar-like-stars-kepler-kepler','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667275-stellar-magnetic-cycles-solar-like-stars-kepler-kepler">STELLAR MAGNETIC CYCLES IN THE SOLAR-LIKE STARS KEPLER-17 AND KEPLER-63</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Estrela, Raissa; Valio, Adriana, E-mail: rlf.estrela@gmail.com, E-mail: avalio@craam.mackenzie.br 2016-11-01 The stellar magnetic field plays a crucial role in the star internal mechanisms, as in the interactions with its environment. The study of starspots provides information about the stellar magnetic field and can characterize the cycle. Moreover, the analysis of solar-type stars is also useful to shed light onto the origin of the solar magnetic field. The objective of this work is to characterize the magnetic activity of stars. Here, we studied two solar-type stars, Kepler-17 and Kepler-63, using two methods to estimate the magnetic cycle length. The first one characterizes the spots (radius, intensity, and location) by fitting themore » small variations in the light curve of a star caused by the occultation of a spot during a planetary transit. This approach yields the number of spots present in the stellar surface and the flux deficit subtracted from the star by their presence during each transit. The second method estimates the activity from the excess in the residuals of the transit light curves. This excess is obtained by subtracting a spotless model transit from the light curve and then integrating all the residuals during the transit. The presence of long-term periodicity is estimated in both time series. With the first method, we obtained P {sub cycle} = 1.12 ± 0.16 year (Kepler-17) and P {sub cycle} = 1.27 ± 0.16 year (Kepler-63), and for the second approach the values are 1.35 ± 0.27 year and 1.27 ± 0.12 year, respectively. The results of both methods agree with each other and confirm their robustness.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070035893&hterms=corona&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dcorona','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070035893&hterms=corona&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dcorona">Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Titov, V. S. 2007-01-01 The study of magnetic connectivity in the solar corona reveals a need to generalize the field line mapping technique to arbitrary geometry of the boundaries and systems of coordinates. Indeed, the global description of the connectivity in the corona requires the use of the photospheric and solar wind boundaries. Both are closed surfaces and therefore do not admit a global regular system of coordinates. At least two overlapping regular systems of coordinates for each of the boundaries are necessary in this case to avoid spherical-pole-like singularities in the coordinates of the footpoints. This implies that the basic characteristic of magnetic connectivity-the squashing degree or factor Q of elemental flux tubes, according to Titov and coworkers-must be rewritten in covariant form. Such a covariant expression of Q is derived in this work. The derived expression is very flexible and highly efficient for describing the global magnetic connectivity in the solar corona. In addition, a general expression for a new characteristic Q1, which defines a squashing of the flux tubes in the directions perpendicular to the field lines, is determined. This new quantity makes it possible to filter out the quasi-separatrix layers whose large values of Q are caused by a projection effect at the field lines nearly touching the photosphere. Thus, the value Q1 provides a much more precise description of the volumetric properties of the magnetic field structure. The difference between Q and Q1 is illustrated by comparing their distributions for two configurations, one of which is the Titov-Demoulin model of a twisted magnetic field. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ASPC..478..145S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ASPC..478..145S">Differences of the Solar Magnetic Activity Signature in Velocity and Intensity Helioseismic Observations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Salabert, D.; García, R. A.; Jiménez, A. 2013-12-01 The high-quality, full-disk helioseismic observations continuously collected by the spectrophotometer GOLF and the three photometers VIRGO/SPMs onboard the SoHO spacecraft for 17 years now (since April 11, 1996, apart from the SoHO “vacations”) are absolutely unique for the study of the interior of the Sun and its variability with magnetic activity. Here, we look at the differences in the low-degree oscillation p-mode frequencies between radial velocity and intensity measurements taking into account all the known features of the p-mode profiles (e.g., the opposite peak asymmetry), and of the power spectrum (e.g., the presence of the higher degrees ℓ = 4 and 5 in the signal). We show that the intensity frequencies are higher than the velocity frequencies during the solar cycle with a clear temporal dependence. The response between the individual angular degrees is also different. Time delays are observed between the temporal variations in GOLF and VIRGO frequencies. Such analysis is important in order to put new constraints and to better understand the mechanisms responsible for the temporal variations of the oscillation frequencies with the solar magnetic activity as well as their height dependences in the solar atmosphere. It is also important for the study of the stellar magnetic activity using asteroseismic data. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMSH53B..06B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMSH53B..06B">High Resolution Observations of Solar Quiescent Prominences with the Hinode Solar Optical Telescope: an Open Challenge to 21st Century Ground-based Solar Telescopes (Invited)</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Berger, T. E. 2009-12-01 is vector magnetic field in prominences at high spatial and temporal resolution and the thermodynamic and magnetic characteristics of the new plume and bubble flows. It is hoped that the new generation of adaptive-optics ground-based telescopes such as the 1.6-m NST can make progress in these areas while we await the next solar space telescope missions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4873661','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4873661">Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Jiang, Chaowei; Wu, S. T.; Feng, Xuesheng; Hu, Qiang 2016-01-01 Solar eruptions are well-recognized as major drivers of space weather but what causes them remains an open question. Here we show how an eruption is initiated in a non-potential magnetic flux-emerging region using magnetohydrodynamic modelling driven directly by solar magnetograms. Our model simulates the coronal magnetic field following a long-duration quasi-static evolution to its fast eruption. The field morphology resembles a set of extreme ultraviolet images for the whole process. Study of the magnetic field suggests that in this event, the key transition from the pre-eruptive to eruptive state is due to the establishment of a positive feedback between the upward expansion of internal stressed magnetic arcades of new emergence and an external magnetic reconnection which triggers the eruption. Such a nearly realistic simulation of a solar eruption from origin to onset can provide important insight into its cause, and also has the potential for improving space weather modelling. PMID:27181846 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110007840','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110007840">A Model for the Sources of the Slow Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Antiochos, Spiro K.; Mikic, Z.; Titov, V. S.; Lionello, R.; Linker, J. A. 2010-01-01 Models for the origin of the slow solar wind must account for two seemingly contradictory observations: The slow wind has the composition of the closed-field corona, implying that it originates from the continuous opening and closing of flux at the boundary between open and closed field. On the other hand, the slow wind has large angular width, up to approximately 60 degrees, suggesting that its source extends far from the open-closed boundary. We propose a model that can explain both observations. The key idea is that the source of the slow wind at the Sun is a network of narrow (possibly singular) open-field corridors that map to a web of separatrices and quasi-separatrix layers in the heliosphere. We compute analytically the topology of an open-field corridor and show that it produces a quasi-separatrix layer in the heliosphere that extends to angles far front the heliospheric current sheet. We then use an MHD code and MIDI/SOHO observations of the photospheric magnetic field to calculate numerically, with high spatial resolution, the quasi-steady solar wind and magnetic field for a time period preceding the August 1, 2008 total solar eclipse. Our numerical results imply that, at least for this time period, a web of separatrices (which we term an S-web) forms with sufficient density and extent in the heliosphere to account for the observed properties of the slow wind. We discuss the implications of our S-web model for the structure and dynamics of the corona and heliosphere, and propose further tests of the model. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ApJ...731..112A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ApJ...731..112A">A Model for the Sources of the Slow Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Antiochos, S. K.; Mikić, Z.; Titov, V. S.; Lionello, R.; Linker, J. A. 2011-04-01 Models for the origin of the slow solar wind must account for two seemingly contradictory observations: the slow wind has the composition of the closed-field corona, implying that it originates from the continuous opening and closing of flux at the boundary between open and closed field. On the other hand, the slow wind also has large angular width, up to ~60°, suggesting that its source extends far from the open-closed boundary. We propose a model that can explain both observations. The key idea is that the source of the slow wind at the Sun is a network of narrow (possibly singular) open-field corridors that map to a web of separatrices and quasi-separatrix layers in the heliosphere. We compute analytically the topology of an open-field corridor and show that it produces a quasi-separatrix layer in the heliosphere that extends to angles far from the heliospheric current sheet. We then use an MHD code and MDI/SOHO observations of the photospheric magnetic field to calculate numerically, with high spatial resolution, the quasi-steady solar wind, and magnetic field for a time period preceding the 2008 August 1 total solar eclipse. Our numerical results imply that, at least for this time period, a web of separatrices (which we term an S-web) forms with sufficient density and extent in the heliosphere to account for the observed properties of the slow wind. We discuss the implications of our S-web model for the structure and dynamics of the corona and heliosphere and propose further tests of the model. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013SoPh..286..157S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013SoPh..286..157S">Signatures of Slow Solar Wind Streams from Active Regions in the Inner Corona</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Slemzin, V.; Harra, L.; Urnov, A.; Kuzin, S.; Goryaev, F.; Berghmans, D. 2013-08-01 The identification of solar-wind sources is an important question in solar physics. The existing solar-wind models ( e.g., the Wang-Sheeley-Arge model) provide the approximate locations of the solar wind sources based on magnetic field extrapolations. It has been suggested recently that plasma outflows observed at the edges of active regions may be a source of the slow solar wind. To explore this we analyze an isolated active region (AR) adjacent to small coronal hole (CH) in July/August 2009. On 1 August, Hinode/EUV Imaging Spectrometer observations showed two compact outflow regions in the corona. Coronal rays were observed above the active-region coronal hole (ARCH) region on the eastern limb on 31 July by STEREO-A/EUVI and at the western limb on 7 August by CORONAS- Photon/TESIS telescopes. In both cases the coronal rays were co-aligned with open magnetic-field lines given by the potential field source surface model, which expanded into the streamer. The solar-wind parameters measured by STEREO-B, ACE, Wind, and STEREO-A confirmed the identification of the ARCH as a source region of the slow solar wind. The results of the study support the suggestion that coronal rays can represent signatures of outflows from ARs propagating in the inner corona along open field lines into the heliosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910001519','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910001519">Coaligned observations of solar magnetic fields at different heights: MSFC Center director's discretionary fund final report (Project No. 88-10)</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hagyard, M. J.; West, E. A.; Gary, G. A.; Smith, J. E. 1990-01-01 The objective was to develop the capability for and coaligned observations of the structure and evolution of the Sun's magnetic field at two different heights in the solar atmosphere: the photosphere, which is the lowest region observable with optical telescopes; and the chromosphere, which lies just above the photosphere and is the region where the magnetic field dominates the gas motion so that a well-ordered structure governed by the field is observed. By obtaining this three-dimensional picture of the solar magnetic field, a better understanding can be developed of the magnetic forces that produce and control the dynamic, high-energy phenomena occurring in the solar atmosphere that can affect the entire heliosphere, including the terrestrial environment. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22521777-recurrent-solar-jets-induced-satellite-spot-moving-magnetic-features','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22521777-recurrent-solar-jets-induced-satellite-spot-moving-magnetic-features">RECURRENT SOLAR JETS INDUCED BY A SATELLITE SPOT AND MOVING MAGNETIC FEATURES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Chen, Jie; Su, Jiangtao; Yin, Zhiqiang 2015-12-10 Recurrent and homologous jets were observed to the west edge of active region NOAA 11513 at the boundary of a coronal hole. We find two kinds of cancellations between opposite polarity magnetic fluxes, inducing the generation of recurrent jets. First, a satellite spot continuously collides with a pre-existing opposite polarity magnetic field and causes recurrent solar jets. Second, moving magnetic features, which emerge near the sunspot penumbra, pass through the ambient plasma and eventually collide with the opposite polarity magnetic field. Among these recurrent jets, a blowout jet that occurred around 21:10 UT is investigated. The rotation of the pre-existingmore » magnetic field and the shear motion of the satellite spot accumulate magnetic energy, which creates the possibility for the jet to experience blowout right from the standard.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21076031','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21076031">Synchronized Northern Hemisphere climate change and solar magnetic cycles during the Maunder Minimum.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yamaguchi, Yasuhiko T; Yokoyama, Yusuke; Miyahara, Hiroko; Sho, Kenjiro; Nakatsuka, Takeshi 2010-11-30 The Maunder Minimum (A.D. 1645-1715) is a useful period to investigate possible sun-climate linkages as sunspots became exceedingly rare and the characteristics of solar cycles were different from those of today. Here, we report annual variations in the oxygen isotopic composition (δ(18)O) of tree-ring cellulose in central Japan during the Maunder Minimum. We were able to explore possible sun-climate connections through high-temporal resolution solar activity (radiocarbon contents; Δ(14)C) and climate (δ(18)O) isotope records derived from annual tree rings. The tree-ring δ(18)O record in Japan shows distinct negative δ(18)O spikes (wetter rainy seasons) coinciding with rapid cooling in Greenland and with decreases in Northern Hemisphere mean temperature at around minima of decadal solar cycles. We have determined that the climate signals in all three records strongly correlate with changes in the polarity of solar dipole magnetic field, suggesting a causal link to galactic cosmic rays (GCRs). These findings are further supported by a comparison between the interannual patterns of tree-ring δ(18)O record and the GCR flux reconstructed by an ice-core (10)Be record. Therefore, the variation of GCR flux associated with the multidecadal cycles of solar magnetic field seem to be causally related to the significant and widespread climate changes at least during the Maunder Minimum. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2996431','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2996431">Synchronized Northern Hemisphere climate change and solar magnetic cycles during the Maunder Minimum</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Yamaguchi, Yasuhiko T.; Yokoyama, Yusuke; Miyahara, Hiroko; Sho, Kenjiro; Nakatsuka, Takeshi 2010-01-01 The Maunder Minimum (A.D. 1645–1715) is a useful period to investigate possible sun–climate linkages as sunspots became exceedingly rare and the characteristics of solar cycles were different from those of today. Here, we report annual variations in the oxygen isotopic composition (δ18O) of tree-ring cellulose in central Japan during the Maunder Minimum. We were able to explore possible sun–climate connections through high-temporal resolution solar activity (radiocarbon contents; Δ14C) and climate (δ18O) isotope records derived from annual tree rings. The tree-ring δ18O record in Japan shows distinct negative δ18O spikes (wetter rainy seasons) coinciding with rapid cooling in Greenland and with decreases in Northern Hemisphere mean temperature at around minima of decadal solar cycles. We have determined that the climate signals in all three records strongly correlate with changes in the polarity of solar dipole magnetic field, suggesting a causal link to galactic cosmic rays (GCRs). These findings are further supported by a comparison between the interannual patterns of tree-ring δ18O record and the GCR flux reconstructed by an ice-core 10Be record. Therefore, the variation of GCR flux associated with the multidecadal cycles of solar magnetic field seem to be causally related to the significant and widespread climate changes at least during the Maunder Minimum. PMID:21076031 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPD....4730106S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPD....4730106S">An Airborne Infrared Spectrometer for Solar Eclipse Observations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Samra, Jenna; DeLuca, Edward E.; Golub, Leon; Cheimets, Peter; Philip, Judge 2016-05-01 The airborne infrared spectrometer (AIR-Spec) is an innovative solar spectrometer that will observe the 2017 solar eclipse from the NSF/NCAR High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER). AIR-Spec will image five infrared coronal emission lines to determine whether they may be useful probes of coronal magnetism.The solar magnetic field provides the free energy that controls coronal heating, structure, and dynamics. Energy stored in coronal magnetic fields is released in flares and coronal mass ejections and ultimately drives space weather. Therefore, direct coronal field measurements have significant potential to enhance understanding of coronal dynamics and improve solar forecasting models. Of particular interest are observations of field lines in the transitional region between closed and open flux systems, providing important information on the origin of the slow solar wind.While current instruments routinely observe only the photospheric and chromospheric magnetic fields, AIR-Spec will take a step toward the direct observation of coronal fields by measuring plasma emission in the infrared at high spatial and spectral resolution. During the total solar eclipse of 2017, AIR-Spec will observe five magnetically sensitive coronal emission lines between 1.4 and 4 µm from the HIAPER Gulfstream V at an altitude above 14.9 km. The instrument will measure emission line intensity, width, and Doppler shift, map the spatial distribution of infrared emitting plasma, and search for waves in the emission line velocities.AIR-Spec consists of an optical system (feed telescope, grating spectrometer, and infrared detector) and an image stabilization system, which uses a fast steering mirror to correct the line-of-sight for platform perturbations. To ensure that the instrument meets its research goals, both systems are undergoing extensive performance modeling and testing. These results are shown with reference to the science requirements. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH23C2675C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH23C2675C">Intermittency Statistics in the Expanding Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cuesta, M. E.; Parashar, T. N.; Matthaeus, W. H. 2017-12-01 The solar wind is observed to be turbulent. One of the open questions in solar wind research is how the turbulence evolves as the solar wind expands to great distances. Some studies have focused on evolution of the outer scale but not much has been done to understand how intermittency evolves in the expanding wind beyond 1 AU (see [1,2]). We use magnetic field data from Voyager I spacecraft from 1 to 10AU to study the evolution of statistics of magnetic discontinuities. We perform various statistical tests on these discontinuities and make connections to the physical processes occurring in the expanding wind.[1] Tsurutani, Bruce T., and Edward J. Smith. "Interplanetary discontinuities: Temporal variations and the radial gradient from 1 to 8.5 AU." Journal of Geophysical Research: Space Physics 84.A6 (1979): 2773-2787.[2] Greco, A., et al. "Evidence for nonlinear development of magnetohydrodynamic scale intermittency in the inner heliosphere." The Astrophysical Journal 749.2 (2012): 105. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013enss.confE..19Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013enss.confE..19Z">Evidences on the Existence of Magnetic Flux Rope Before and During a Solar Eruption</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhang, Jie; Cheng, Xin; Liu, Kai 2013-03-01 We report the observational evidences from the advanced SDO observations that magnetic flux ropes exist before and during solar eruptions. The solar eruption is defined as coronal mass ejection, whether or not associated with a solar flare. Magnetic flux ropes are directly observed as hot EUV channels as seen in the hot AIA 131 (10 MK) and/or AIA 94 (6.4 MK) passbands, but are absent in cool AIA passbands. The fact that flux ropes are only seen in hot temperatures explains their evasion of detection from previous EUV observations, such as SOHO/EIT, TRACE and STEREO/EUVI. The hot channel usually appears as a writhed sigmoidal shape and slowly rises prior to the onset of the impulsive acceleration as well as the onset of the flare. The hot channel transforms into a CME-like semi-circular shape in a continuous way, indicating its trapping or organization by a coherent magnetic structure. The dynamic and thermal properties of flux ropes will also be presented. We further discuss the critical role of flux ropes in CME initiation and subsequent acceleration, in light of contrasting the standard eruptive flare models. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatCo...6E6491M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatCo...6E6491M">The solar magnetic activity band interaction and instabilities that shape quasi-periodic variability</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McIntosh, Scott W.; Leamon, Robert J.; Krista, Larisza D.; Title, Alan M.; Hudson, Hugh S.; Riley, Pete; Harder, Jerald W.; Kopp, Greg; Snow, Martin; Woods, Thomas N.; Kasper, Justin C.; Stevens, Michael L.; Ulrich, Roger K. 2015-04-01 Solar magnetism displays a host of variational timescales of which the enigmatic 11-year sunspot cycle is most prominent. Recent work has demonstrated that the sunspot cycle can be explained in terms of the intra- and extra-hemispheric interaction between the overlapping activity bands of the 22-year magnetic polarity cycle. Those activity bands appear to be driven by the rotation of the Sun's deep interior. Here we deduce that activity band interaction can qualitatively explain the `Gnevyshev Gap'--a well-established feature of flare and sunspot occurrence. Strong quasi-annual variability in the number of flares, coronal mass ejections, the radiative and particulate environment of the heliosphere is also observed. We infer that this secondary variability is driven by surges of magnetism from the activity bands. Understanding the formation, interaction and instability of these activity bands will considerably improve forecast capability in space weather and solar activity over a range of timescales. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4396379','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4396379">The solar magnetic activity band interaction and instabilities that shape quasi-periodic variability</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> McIntosh, Scott W.; Leamon, Robert J.; Krista, Larisza D.; Title, Alan M.; Hudson, Hugh S.; Riley, Pete; Harder, Jerald W.; Kopp, Greg; Snow, Martin; Woods, Thomas N.; Kasper, Justin C.; Stevens, Michael L.; Ulrich, Roger K. 2015-01-01 Solar magnetism displays a host of variational timescales of which the enigmatic 11-year sunspot cycle is most prominent. Recent work has demonstrated that the sunspot cycle can be explained in terms of the intra- and extra-hemispheric interaction between the overlapping activity bands of the 22-year magnetic polarity cycle. Those activity bands appear to be driven by the rotation of the Sun's deep interior. Here we deduce that activity band interaction can qualitatively explain the ‘Gnevyshev Gap'—a well-established feature of flare and sunspot occurrence. Strong quasi-annual variability in the number of flares, coronal mass ejections, the radiative and particulate environment of the heliosphere is also observed. We infer that this secondary variability is driven by surges of magnetism from the activity bands. Understanding the formation, interaction and instability of these activity bands will considerably improve forecast capability in space weather and solar activity over a range of timescales. PMID:25849045 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654254-controlling-influence-magnetic-field-solar-wind-outflow-investigation-using-current-sheet-source-surface-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654254-controlling-influence-magnetic-field-solar-wind-outflow-investigation-using-current-sheet-source-surface-model">CONTROLLING INFLUENCE OF MAGNETIC FIELD ON SOLAR WIND OUTFLOW: AN INVESTIGATION USING CURRENT SHEET SOURCE SURFACE MODEL</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Poduval, B., E-mail: bpoduval@spacescience.org 2016-08-10 This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle 23 and beginning of solar cycle 24, we found that the coefficients of the fitted quadratic equation representing the FTE–SWS inverse relation exhibited significantmore » temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008–2010 (CRs 2073–2092), which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060036834&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060036834&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS">The Distant Tail Behavior During High Speed Solar Wind Streams and Magnetic Storms</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ho, C. M.; Tsurutani, B. T. 1996-01-01 We have examined the ISEE-3 distant tail data during three intense (Dst< -100(sub n)T) magnetic storms and have identified the tail response to high speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms. The three storms have a peak Dst ranging from -150 to -220 nT, and occur on Jan. 9, Feb. 4, and Aug. 8, 1993. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20150010745&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DG%2526T','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20150010745&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DG%2526T">Anisotropic Solar Wind Sputtering of the Lunar Surface Induced by Crustal Magnetic Anomalies</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Poppe, A. R.; Sarantos, M.; Halekas, J. S.; Delory, G. T.; Saito, Y.; Nishino, M. 2014-01-01 The lunar exosphere is generated by several processes each of which generates neutral distributions with different spatial and temporal variability. Solar wind sputtering of the lunar surface is a major process for many regolith-derived species and typically generates neutral distributions with a cosine dependence on solar zenith angle. Complicating this picture are remanent crustal magnetic anomalies on the lunar surface, which decelerate and partially reflect the solar wind before it strikes the surface. We use Kaguya maps of solar wind reflection efficiencies, Lunar Prospector maps of crustal field strengths, and published neutral sputtering yields to calculate anisotropic solar wind sputtering maps. We feed these maps to a Monte Carlo neutral exospheric model to explore three-dimensional exospheric anisotropies and find that significant anisotropies should be present in the neutral exosphere depending on selenographic location and solar wind conditions. Better understanding of solar wind/crustal anomaly interactions could potentially improve our results. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SSRv..210....5S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SSRv..210....5S">History of Solar Magnetic Fields Since George Ellery Hale</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Stenflo, J. O. 2017-09-01 As my own work on the Sun's magnetic field started exactly 50 years ago at Crimea in the USSR, I have been a participant in the field during nearly half the time span since Hale's discovery in 1908 of magnetic fields in sunspots. The present historical account is accompanied by photos from my personal slide collection, which show a number of the leading personalities who advanced the field in different areas: measurement techniques, from photographic to photoelectric and imaging methods in spectro-polarimetry; theoretical foundations of MHD and the origin of cosmic magnetic fields (birth of dynamo theory); the quest for increased angular resolution from national projects to international consortia (for instruments both on ground and in space); introduction of the Hanle effect in astrophysics and the Second Solar Spectrum as its playground; small-scale nature of the field, the fundamental resolution limit, and transcending it by resolution-independent diagnostics. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663650-magnetic-helicity-estimations-models-observations-solar-magnetic-field-iii-twist-number-method','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663650-magnetic-helicity-estimations-models-observations-solar-magnetic-field-iii-twist-number-method">Magnetic Helicity Estimations in Models and Observations of the Solar Magnetic Field. III. Twist Number Method</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Guo, Y.; Pariat, E.; Moraitis, K. We study the writhe, twist, and magnetic helicity of different magnetic flux ropes, based on models of the solar coronal magnetic field structure. These include an analytical force-free Titov–Démoulin equilibrium solution, non-force-free magnetohydrodynamic simulations, and nonlinear force-free magnetic field models. The geometrical boundary of the magnetic flux rope is determined by the quasi-separatrix layer and the bottom surface, and the axis curve of the flux rope is determined by its overall orientation. The twist is computed by the Berger–Prior formula, which is suitable for arbitrary geometry and both force-free and non-force-free models. The magnetic helicity is estimated by the twistmore » multiplied by the square of the axial magnetic flux. We compare the obtained values with those derived by a finite volume helicity estimation method. We find that the magnetic helicity obtained with the twist method agrees with the helicity carried by the purely current-carrying part of the field within uncertainties for most test cases. It is also found that the current-carrying part of the model field is relatively significant at the very location of the magnetic flux rope. This qualitatively explains the agreement between the magnetic helicity computed by the twist method and the helicity contributed purely by the current-carrying magnetic field.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1734c0007C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1734c0007C">Numerical evaluation of an innovative cup layout for open volumetric solar air receivers</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cagnoli, Mattia; Savoldi, Laura; Zanino, Roberto; Zaversky, Fritz 2016-05-01 This paper proposes an innovative volumetric solar absorber design to be used in high-temperature air receivers of solar power tower plants. The innovative absorber, a so-called CPC-stacked-plate configuration, applies the well-known principle of a compound parabolic concentrator (CPC) for the first time in a volumetric solar receiver, heating air to high temperatures. The proposed absorber configuration is analyzed numerically, applying first the open-source ray-tracing software Tonatiuh in order to obtain the solar flux distribution on the absorber's surfaces. Next, a Computational Fluid Dynamic (CFD) analysis of a representative single channel of the innovative receiver is performed, using the commercial CFD software ANSYS Fluent. The solution of the conjugate heat transfer problem shows that the behavior of the new absorber concept is promising, however further optimization of the geometry will be necessary in order to exceed the performance of the classical absorber designs. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008cosp...37.2150M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008cosp...37.2150M">Bashful Ballerina: The asymmetric global solar magnetic field viewed from the heliosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mursula, Kalevi Long-term observations of the heliospheric magnetic field (HMF) at 1 AU have depicted interesting systematic hemispheric and longitudinal asymmetries that have far-reaching implications for the understanding of solar magnetism. It has been found that the HMF sector of the northern solar hemisphere dominates the observed HMF sector occurrence in the heliosphere for about three years during the late declining to minimum phase of the solar cycle. This leads to a persistent southward shift or coning of the heliospheric current sheet at these times, which has been described by the concept of the bashful ballerina. Measurements of the solar surface fields have verified that, at these times, the average field intensity is smaller and the area larger in the northern than in the southern solar hemisphere. They have also shown that a persistent global quadrupole moment, oppositely oriented with respect to the dipole moment, appears at these times. Long-term observations of the geomagnetic field can yield information on the HMF sector structure in the pre-satellite era, and show that the ballerina was bashful at least since 1930s. In addition to the hemispheric asymmetries, the Sun is systematically asymmetric in longitude. The HMF has persistent active longitudes whose dominance depicts an oscillation with a period of about 3.2 years. Similar flip-flopping is also seen in the longitudinal distribution of sunspots and stellar observations show that this is a general pattern for sun-like cool stars. We describe these phenomena and discuss their theoretical implications. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUSMSH44A..05M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUSMSH44A..05M">Bashful Ballerina: The asymmetric global solar magnetic field viewed from the heliosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mursula, K. 2008-05-01 Long-term observations of the heliospheric magnetic field (HMF) at 1 AU have depicted interesting systematic hemispheric and longitudinal asymmetries that have far-reaching implications for the understanding of solar magnetism. It has been found that the HMF sector of the northern solar hemisphere dominates the observed HMF sector occurrence in the heliosphere for about three years during the late declining to minimum phase of the solar cycle. This leads to a persistent southward shift or coning of the heliospheric current sheet at these times, which has been described by the concept of the bashful ballerina. Measurements of the solar surface fields have verified that, at these times, the average field intensity is smaller and the area larger in the northern than in the southern solar hemisphere. They have also shown that a persistent global quadrupole moment, oppositely oriented with respect to the dipole moment, appears at these times. Long-term observations of the geomagnetic field can yield information on the HMF sector structure in the pre- satellite era, and show that the ballerina was bashful at least since 1930s. In addition to the hemispheric asymmetries, the Sun is systematically asymmetric in longitude. The HMF has persistent active longitudes whose dominance depicts an oscillation with a period of about 3.2 years. Similar flip-flopping is also seen in the longitudinal distribution of sunspots and stellar observations show that this is a general pattern for sun-like cool stars. We describe these phenomena and discuss their theoretical implications. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSH23A4148T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSH23A4148T">Magnetic Topology of the Global MHD Configuration on 2010 August 1-2</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Titov, V. S.; Mikic, Z.; Torok, T.; Linker, J.; Panasenco, O. 2014-12-01 It appears that the global magnetic topology of the solar corona predetermines to a large extent the magnetic flux transfer during solar eruptions. We have recently analyzed the global topology for a source-surface model of the background magnetic field at the time of the 2010 August 1-2 sympathetic CMEs (Titov et al. 2012). Now we extend this analysis to a more accurate thermodynamic MHD model of the solar corona. As for the source-surface model, we find a similar triplet of pseudo-streamers in the source regions of the eruptions. The new study confirms that all these pseudo-streamers contain separatrix curtains that fan out from a basic magnetic null point, individual for each of the pseudo-streamers. In combination with the associated separatrix domes, these separatrix curtains fully isolate adjacent coronal holes of the like polarity from each other. However, the size and shape of the coronal holes, as well as their open magnetic fluxes and the fluxes in the lobes of the separatrix domes, are very different for the two models. The definition of the open separator field lines, where the (interchange) reconnection between open and closed magnetic flux takes place, is also modified, since the structurally unstable source-surface null lines do not exist anymore in the MHD model. In spite of all these differences, we reassert our earlier hypothesis that magnetic reconnection at these nulls and the associated separators likely plays a key role in coupling the successive eruptions observed by SDO and STEREO. The results obtained provide further validation of our recent simplified MHD model of sympathetic eruptions (Török et al. 2011). Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990PDHO....7...80G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990PDHO....7...80G">The role of activity complexes in the distribution of solar magnetic fields.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> García de La Rosa, J. I.; Reyes, R. C. Using published data on the large-scale distribution of solar activity, the authors conclude that the longlived coronal holes are formed and maintained by the unbalanced magnetic flux which developes at both extremes of the complexes of activity. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22664028-electron-acceleration-contracting-magnetic-islands-during-solar-flares','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22664028-electron-acceleration-contracting-magnetic-islands-during-solar-flares">ELECTRON ACCELERATION IN CONTRACTING MAGNETIC ISLANDS DURING SOLAR FLARES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Borovikov, D.; Tenishev, V.; Gombosi, T. I. Electron acceleration in solar flares is well known to be efficient at generating energetic particles that produce the observed bremsstrahlung X-ray spectra. One mechanism proposed to explain the observations is electron acceleration within contracting magnetic islands formed by magnetic reconnection in the flare current sheet. In a previous study, a numerical magnetohydrodynamic simulation of an eruptive solar flare was analyzed to estimate the associated electron acceleration due to island contraction. That analysis used a simple analytical model for the island structure and assumed conservation of the adiabatic invariants of particle motion. In this paper, we perform the first-ever rigorous integrationmore » of the guiding-center orbits of electrons in a modeled flare. An initially isotropic distribution of particles is seeded in a contracting island from the simulated eruption, and the subsequent evolution of these particles is followed using guiding-center theory. We find that the distribution function becomes increasingly anisotropic over time as the electrons’ energy increases by up to a factor of five, in general agreement with the previous study. In addition, we show that the energized particles are concentrated on the Sunward side of the island, adjacent to the reconnection X-point in the flare current sheet. Furthermore, our analysis demonstrates that the electron energy gain is dominated by betatron acceleration in the compressed, strengthened magnetic field of the contracting island. Fermi acceleration by the shortened field lines of the island also contributes to the energy gain, but it is less effective than the betatron process.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010094541','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010094541">Solar Physics</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wu, S. T. 2000-01-01 The areas of emphasis are: (1) develop theoretical models of the transient release of magnetic energy in the solar atmosphere, e.g., in solar flares, eruptive prominences, coronal mass ejections, etc.; (2) investigate the role of the Sun's magnetic field in the structuring of solar corona by the development of three-dimensional numerical models that describe the field configuration at various heights in the solar atmosphere by extrapolating the field at the photospheric level; (3) develop numerical models to investigate the physical parameters obtained by the ULYSSES mission; (4) develop numerical and theoretical models to investigate solar activity effects on the solar wind characteristics for the establishment of the solar-interplanetary transmission line; and (5) develop new instruments to measure solar magnetic fields and other features in the photosphere, chromosphere transition region and corona. We focused our investigation on the fundamental physical processes in solar atmosphere which directly effect our Planet Earth. The overall goal is to establish the physical process for the Sun-Earth connections. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711384A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711384A">Interaction of Solar Wind and Magnetic Anomalies - Modelling from Moon to Mars</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Alho, Markku; Kallio, Esa; Wedlund, Cyril Simon; Wurz, Peter 2015-04-01 The crustal magnetic anomalies on both the Moon and Mars strongly affect the local plasma environment. On the Moon, the impinging solar wind is decelerated or deflected when interacting with the magnetic field anomaly, visible in the lunar surface as energetic neutral atom (ENA) emissions or as reflected protons, and may play a part in the space weathering of the lunar soil. At Mars, the crustal magnetic fields have been shown to be associated with, e.g., enhanced electron scale heights and modified convection of ionospheric plasma, resulting in the plasma environment being dominated by crustal magnetic fields up to altitudes of 400km. Our previous modelling work suggested that Hall currents are a dominant feature in a Moon-like magnetic anomaly interaction at scales at or below the proton inertial length. In this work we study the solar wind interaction with magnetic anomalies and compare the plasma environments of a Moon-like anomaly with a Mars-like anomaly by introducing an ionosphere and an exosphere to probe the transition from an atmosphere-less anomaly interaction to an ionospheric one. We utilize a 3D hybrid plasma model, in which ions are modelled as particles while electrons form a charge-neutralizing massless fluid. The hybrid model gives a full description of ion kinetics and associated plasma phenomena at the simulation region ranging from instabilities to possible reconnection. The model can thus be used to interpret both in-situ particle and field observations and remotely-sensed ENA emissions. A self-consistent ionosphere package for the model is additionally in development. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790012789','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790012789">Contributions to the Fourth Solar Wind Conference. [interplanetary magnetic fields and medium</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Acuna, M. H.; Behannon, K. W.; Burlaga, L. F.; Lepping, R.; Ness, N.; Ogilvie, K.; Pizzo, J. 1979-01-01 Recent results in interplanetary physics are examined. These include observations of shock waves and post-shock magnetic fields made by Voyager 1, 2; observations of the electron temperature as a function of distance between 1.36 AU and 2.25 AU; and observations of the structure of sector boundaries observed by Helios 1. A theory of electron energy transport in the collisionless solar wind is presented, and compared with observations. Alfven waves and Alvenic fluctuations in the solar wind are also discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011A%26A...528A.104M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011A%26A...528A.104M">Budget of energetic electrons during solar flares in the framework of magnetic reconnection</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mann, G.; Warmuth, A. 2011-04-01 Context. Among other things, solar flares are accompanied by the production of energetic electrons as seen in the nonthermal radio and X-ray radiation of the Sun. Observations of the RHESSI satellite show that 1032-1036 nonthermal electrons are produced per second during flares. They are related to an energy flux in the range 1018-1022 W. These electrons play an important role, since they carry a substantial part of the energy released during a flare. Aims: In which way so many electrons are accelerated up to high energies during a fraction of a second is still an open question. By means of radio and hard X-ray data, we investigate under which conditions this acceleration happens in the corona. Methods: The flare is considered in the framework of magnetic reconnection. The conditions in the acceleration region in the corona are deduced by using the conservation of the total electron number and energy. Results: In the inflow region of the magnetic reconnection site, there are typical electron number densities of about 2.07 × 109 cm-3 and magnetic fields of about 46 G. These are regions with high Alfvén speeds of about 2200 km s-1. Then, sufficient energetic electrons (as required by the RHESSI observations) are only generated if the plasma inflow towards the reconnection site has Alfvén-Mach numbers in the range 0.1-1, which can lead to a super-Alfvénic outflow with speeds up to 3100 km s-1. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...856..179Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...856..179Z">Three-dimensional MHD Simulations of Solar Prominence Oscillations in a Magnetic Flux Rope</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhou, Yu-Hao; Xia, C.; Keppens, R.; Fang, C.; Chen, P. F. 2018-04-01 Solar prominences are subject to all kinds of perturbations during their lifetime, and frequently demonstrate oscillations. The study of prominence oscillations provides an alternative way to investigate their internal magnetic and thermal structures because the characteristics of the oscillations depend on their interplay with the solar corona. Prominence oscillations can be classified into longitudinal and transverse types. We perform three-dimensional ideal magnetohydrodynamic simulations of prominence oscillations along a magnetic flux rope, with the aim of comparing the oscillation periods with those predicted by various simplified models and examining the restoring force. We find that the longitudinal oscillation has a period of about 49 minutes, which is in accordance with the pendulum model where the field-aligned component of gravity serves as the restoring force. In contrast, the horizontal transverse oscillation has a period of about 10 minutes and the vertical transverse oscillation has a period of about 14 minutes, and both of them can be nicely fitted with a two-dimensional slab model. We also find that the magnetic tension force dominates most of the time in transverse oscillations, except for the first minute when magnetic pressure overwhelms it. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840020134','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840020134">Solar energy modulator</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hale, R. R. (Inventor); Mcdougal, A. R. 1984-01-01 A module is described with a receiver having a solar energy acceptance opening and supported by a mounting ring along the optic axis of a parabolic mirror in coaxial alignment for receiving solar energy from the mirror, and a solar flux modulator plate for varying the quantity of solar energy flux received by the acceptance opening of the module. The modulator plate is characterized by an annular, plate-like body, the internal diameter of which is equal to or slightly greater than the diameter of the solar energy acceptance opening of the receiver. Slave cylinders are connected to the modulator plate for supporting the plate for axial displacement along the axis of the mirror, therby shading the opening with respect to solar energy flux reflected from the surface of the mirror to the solar energy acceptance opening. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19458864','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19458864">Fundamentals of magnet-actuated droplet manipulation on an open hydrophobic surface.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Long, Zhicheng; Shetty, Abhishek M; Solomon, Michael J; Larson, Ronald G 2009-06-07 We systematically investigate droplet movement, coalescence, and splitting on an open hydrophobic surface. These processes are actuated by magnetic beads internalized in an oil-coated aqueous droplet using an external magnet. Results are organized into an 'operating diagram' that describes regions of droplet stable motion, breakage, and release from the magnet. The results are explained theoretically with a simple model that balances magnetic, friction, and capillary-induced drag forces and includes the effects of particle type, droplet size, surrounding oil layer, surface tension, and viscosity. Finally, we discuss the implications of the results for the design of magnet-actuated droplet systems for applications such as nucleic acid purification, immunoassay and drug delivery. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2932710','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2932710">Fundamentals of magnet-actuated droplet manipulation on an open hydrophobic surface†</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Long, Zhicheng; Shetty, Abhishek M.; Solomon, Michael J.; Larson, Ronald G. 2010-01-01 We systematically investigate droplet movement, coalescence, and splitting on an open hydrophobic surface. These processes are actuated by magnetic beads internalized in an oil-coated aqueous droplet using an external magnet. Results are organized into an ‘operating diagram’ that describes regions of droplet stable motion, breakage, and release from the magnet. The results are explained theoretically with a simple model that balances magnetic, friction, and capillary-induced drag forces and includes the effects of particle type, droplet size, surrounding oil layer, surface tension, and viscosity. Finally, we discuss the implications of the results for the design of magnet-actuated droplet systems for applications such as nucleic acid purification, immunoassay and drug delivery. PMID:19458864 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017hst..prop15299A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017hst..prop15299A">Weaving the history of the solar wind with magnetic field lines</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Alvarado Gomez, Julian 2017-08-01 Despite its fundamental role for the evolution of the solar system, our observational knowledge of the wind properties of the young Sun comes from a single stellar observation. This unexpected fact for a field such as astrophysics arises from the difficulty of detecting Sun-like stellar winds. Their detection relies on the appearance of an astrospheric signature (from the stellar wind-ISM interaction region), visible only with the aid of high-resolution HST Lyman-alpha spectra. However, observations and modelling of the present day Sun have revealed that magnetic fields constitute the main driver of the solar wind, providing guidance on how such winds would look like back in time. In this context we propose observations of four young Sun-like stars in order to detect their astrospheres and characterise their stellar winds. For all these objects we have recovered surface magnetic field maps using the technique of Zeeman Doppler Imaging, and developed detailed wind models based on these observed field distributions. Even a single detection would represent a major step forward for our understanding of the history of the solar wind, and the outflows in more active stars. Mass loss rate estimates from HST will be confronted with predictions from realistic models of the corona/stellar wind. In one of our objects the comparison would allow us to quantify the wind variability induced by the magnetic cycle of a star, other than the Sun, for the first time. Three of our targets are planet hosts, thus the HST spectra would also provide key information on the high-energy environment of these systems, guaranteeing their legacy value for the growing field of exoplanet characterisation. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SoPh..293...47R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SoPh..293...47R">The "FIP Effect" and the Origins of Solar Energetic Particles and of the Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Reames, Donald V. 2018-03-01 We find that the element abundances in solar energetic particles (SEPs) and in the slow solar wind (SSW), relative to those in the photosphere, show different patterns as a function of the first ionization potential (FIP) of the elements. Generally, the SEP and SSW abundances reflect abundance samples of the solar corona, where low-FIP elements, ionized in the chromosphere, are more efficiently conveyed upward to the corona than high-FIP elements that are initially neutral atoms. Abundances of the elements, especially C, P, and S, show a crossover from low to high FIP at {≈} 10 eV in the SEPs but {≈} 14 eV for the solar wind. Naively, this seems to suggest cooler plasma from sunspots beneath active regions. More likely, if the ponderomotive force of Alfvén waves preferentially conveys low-FIP ions into the corona, the source plasma that eventually will be shock-accelerated as SEPs originates in magnetic structures where Alfvén waves resonate with the loop length on closed magnetic field lines. This concentrates FIP fractionation near the top of the chromosphere. Meanwhile, the source of the SSW may lie near the base of diverging open-field lines surrounding, but outside of, active regions, where such resonance does not exist, allowing fractionation throughout the chromosphere. We also find that energetic particles accelerated from the solar wind itself by shock waves at corotating interaction regions, generally beyond 1 AU, confirm the FIP pattern of the solar wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017reph.conf20005B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017reph.conf20005B">Lessons from our Own Solar System: Generation Mechanisms of Radio Emissions from Earth, Saturn and Jupiter and Atmospheric Loss from Magnetized versus non-magnetized planets</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Brandt, Pontus 2017-05-01 The understanding of the engines and mechanisms behind kilometric and decametric radio emissions from the planets in our own solar system have taken great leaps with missions such as the NASA/Cassini, IMAGE and Galileo missions. The periodic Saturn Kilometric Radiation (SKR), the Auroral Kilometric Radiation (AKR) at Earth and the periodic decametric radio emissions from Jupiter all point to the same generation mechanisms: very large-scale explosive plasma heating events in the magnetotail of each of the planets. The character and periodicity of the associated radio emissions not only tells us about the presence of a magnetic field but also about the plasma content and size of the planetary magnetosphere, and the nature of the interaction with the solar wind.The presence of a planetary magnetic field, as could be established for exoplanets by the positive detection of low-frequency exoplanetary radio emissions, has been thought to shield a planet from atmospheric loss to space. However, recent data from Mars Express, MAVEN, and Venus Express, together with the wealth of terrestrial measurements of atmospheric escape to space has brought a surprising question in to light: Does a planetary magnetic field suppress or enhance atmospheric loss? While at the non-magnetized planets such as Mars and Venus, the solar wind has a more direct access to the ionized upper atmosphere, these planets do set up self shielding currents that do limit escape. Furthermore, it is not clear if Mars have lost the majority of its atmosphere by condensation in to surface and sub-surface frost, or through atmospheric escape. At Earth, the geomagnetic field sets up a relatively large cross section to the solar wind, that allows the induced solar-wind electric field to transfer substantial energy to the upper ionosphere and atmosphere resulting in substantial loss. It is therefore not clear how a planetary magnetic field correlates to the atmospheric loss, or if it does at all.In this </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770035711&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DMagnetic%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770035711&hterms=Magnetic+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DMagnetic%2Benergy">On build-up of magnetic energy in the solar atmosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Nakagawa, Y.; Steinolfson, R. S.; Wu, S. T. 1976-01-01 The dynamic response of the solar atmosphere is examined with the use of self-consistent numerical solutions to the complete set of nonlinear two-dimensional hydromagnetic equations. Of particular interest are the magnetic-energy buildup and the velocity field established by emerging flux at the base of an existing magnetic loop structure in a stationary atmosphere. For a plasma with a relatively low beta (0.03), the magnetic-energy buildup is approximately twice that of the kinetic energy, while the buildup in magnetic energy first exceeds but is eventually overtaken by the kinetic energy for a plasma with an intermediate beta (3). The increased magnetic flux causes the plasma to flow upward near the loop center and downward near the loop edges for the low-beta plasma. The plasma eventually flows downward throughout the lower portion of the loop carrying the magnetic field with it for the intermediate beta plasma. It is hypothesized that this latter case, and possibly the other case as well, may provide a reasonable simulation of the disappearance of prominences by flowing down into the chromosphere (a form of disparition brusque). </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900023756&hterms=solar+two&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dsolar%2Btwo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900023756&hterms=solar+two&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dsolar%2Btwo">Two-dimensional magnetohydrodynamic model of emerging magnetic flux in the solar atmosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Shibata, K.; Tajima, T.; Steinolfson, R. S.; Matsumoto, R. 1989-01-01 The nonlinear undular mode of the magnetic buoyancy instability in an isolated horizontal magnetic flux embedded in a two-temperature layered atmosphere (solar corona-chromosphere/photosphere) is investigated using a two-dimensional magnetohydrodynamic code. The results show that the flux sheet with beta of about 1 is initially located at the bottom of the photosphere, and that the gas slides down the expanding loop as the instability develops, with the evacuated loop rising as a result of enhanced magnetic buoyancy. The expansion of the magnetic loop in the nonlinear regime displays self-similar behavior. The rise velocity of the magnetic loop in the high chromosphere (10-15 km/s) and the velocity of downflow noted along the loop (30-50 km/s) are consistent with observed values for arch filament systems. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750052795&hterms=solar+pumping&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dsolar%2Bpumping','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750052795&hterms=solar+pumping&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dsolar%2Bpumping">Measuring the magnetic fields of Jupiter and the outer solar system</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Smith, E. J.; Connor, B. V.; Foster, G. T., Jr. 1975-01-01 The vector helium magnetometer, one of the Pioneer-Jupiter experiments, has measured the magnetic field of Jupiter and the interplanetary magnetic field in the outer solar system. The comprehensive scientific objectives of the investigations are explained and are then translated into the major instrument requirements. The principles of operation of the magnetometer, which involve the optical pumping of metastable helium, are discussed and the Pioneer instrument is described. The in-flight performance of the magnetometer is discussed and principal scientific results obtained thus far by the Pioneer investigation are summarized. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890058319&hterms=magnetic+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dmagnetic%2Bcooling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890058319&hterms=magnetic+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dmagnetic%2Bcooling">Steady hydromagnetic flows in open magnetic fields. II - Global flows with static zones</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Tsinganos, K.; Low, B. C. 1989-01-01 A theoretical study of an axisymmetric steady stellar wind with a static zone is presented, with emphasis on the situation where the global magnetic field is symmetrical about the stellar equator and is partially open. In this scenario, the wind escapes in open magnetic fluxes originating from a region at the star pole and a region at an equatorial belt of closed magnetic field in static equilibrium. The two-dimensional balance of the pressure gradient and the inertial, gravitational, and Lorentz forces in different parts of the flow are studied, along with the static interplay between external sources of energy (heating and/or cooling) distributed in the flow and the pressure distribution. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170005821&hterms=corona&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcorona','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170005821&hterms=corona&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcorona">The Role of Magnetic Helicity in Structuring the Solar Corona</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Knizhnik, K. J.; Antiochos, S. K.; DeVore, C. R. 2017-01-01 Two of the most widely observed and striking features of the Suns magnetic field are coronal loops, which are smooth and laminar, and prominences or filaments, which are strongly sheared. Loops are puzzling because they show little evidence of tangling or braiding, at least on the quiet Sun, despite the chaotic nature of the solar surface convection. Prominences are mysterious because the origin of their underlying magnetic structure filament channels is poorly understood at best. These two types of features would seem to be quite unrelated and wholly distinct. We argue that, on the contrary, they are inextricably linked and result from a single process: the injection of magnetic helicity into the corona by photospheric motions and the subsequent evolution of this helicity by coronal reconnection. In this paper, we present numerical simulations of the response of a Parker (1972) corona to photospheric driving motions that have varying degrees of helicity preference. We obtain four main conclusions: (1) in agreement with the helicity condensation model of Antiochos (2013), the inverse cascade of helicity by magnetic reconnection in the corona results in the formation of filament channels localized about polarity inversion lines; (2) this same process removes most complex fine structure from the rest of the corona, resulting in smooth and laminar coronal loops; (3) the amount of remnant tangling in coronal loops is inversely dependent on the net helicity injected by the driving motions; and (4) the structure of the solar corona depends only on the helicity preference of the driving motions and not on their detailed time dependence. We discuss the implications of our results for high-resolution observations of the corona. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663822-role-magnetic-helicity-structuring-solar-corona','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663822-role-magnetic-helicity-structuring-solar-corona">THE ROLE OF MAGNETIC HELICITY IN STRUCTURING THE SOLAR CORONA</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Knizhnik, K. J.; Antiochos, S. K.; DeVore, C. R. Two of the most widely observed and striking features of the Sun's magnetic field are coronal loops, which are smooth and laminar, and prominences or filaments, which are strongly sheared. Loops are puzzling because they show little evidence of tangling or braiding, at least on the quiet Sun, despite the chaotic nature of the solar surface convection. Prominences are mysterious because the origin of their underlying magnetic structure—filament channels—is poorly understood at best. These two types of features would seem to be quite unrelated and wholly distinct. We argue that, on the contrary, they are inextricably linked and result frommore » a single process: the injection of magnetic helicity into the corona by photospheric motions and the subsequent evolution of this helicity by coronal reconnection. In this paper, we present numerical simulations of the response of a Parker (1972) corona to photospheric driving motions that have varying degrees of helicity preference. We obtain four main conclusions: (1) in agreement with the helicity condensation model of Antiochos (2013), the inverse cascade of helicity by magnetic reconnection in the corona results in the formation of filament channels localized about polarity inversion lines; (2) this same process removes most complex fine structure from the rest of the corona, resulting in smooth and laminar coronal loops; (3) the amount of remnant tangling in coronal loops is inversely dependent on the net helicity injected by the driving motions; and (4) the structure of the solar corona depends only on the helicity preference of the driving motions and not on their detailed time dependence. We discuss the implications of our results for high-resolution observations of the corona.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA562846','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA562846">The Floor in the Solar Wind Magnetic Field Revisited</a> <a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a> 2012-05-07 index of geomagnetic activity (Svalgaard and Cliver, 2005). This empir- ical/historical evidence for a lower limit or floor in B was substantiated by...with the model of Fisk and Schwadron (2001) for the reversal of the polar magnetic fields at solar maximum. The Fisk and Schwadron model, based on the...interdiurnal variability [IDV] index of geomagnetic activity (Svalgaard and Cliver, 2005, 2010). DM, for minima preceding cycles 22 – 24, is the absolute </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPD....47.0324P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPD....47.0324P">Morphology of Pseudostreamers and Solar Wind Properties</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Panasenco, Olga; Velli, Marco 2016-05-01 The solar dynamo and photospheric convection lead to three main types of structures extending from the solar surface into the corona - active regions, solar filaments (prominences when observed at the limb) and coronal holes. These structures exist over a wide range of scales, and are interlinked with each other in evolution and dynamics. Active regions can form clusters of magnetic activity and the strongest overlie sunspots. In the decay of active regions, the boundaries separating opposite magnetic polarities (neutral lines) develop the specific structures called filament channels above which filaments form. In the presence of flux imbalance decaying active regions can also give birth to lower latitude coronal holes. The accumulation of magnetic flux at coronal hole boundaries also creates the conditions for filament formation: polar crown filaments are permanently present at the boundaries of the polar coronal holes. Middle-latitude and equatorial coronal holes - the result of active region evolution - can create pseudostreamers (PSs) if other coronal holes of the same polarity are present. While helmet streamers form between open fields of opposite polarities, the pseudostreamer, characterized by a smaller coronal imprint, typically shows a more prominent straight ray or stalk extending from the corona. The pseudostreamer base at photospheric heights is multipolar; often one observes tripolar magnetic configurations with two neutral lines - where filaments can form - separating the coronal holes. Here we discuss the specific role of filament channels on pseudostreamer topology and on solar wind properties. 1D numerical analysis of PSs shows that the properties of the solar wind from around PSs depend on the presence/absence of filament channels, number of channels and chirality at the PS base low in the corona. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...850L..28L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...850L..28L">Magnetic Pumping as a Source of Particle Heating and Power-law Distributions in the Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lichko, E.; Egedal, J.; Daughton, W.; Kasper, J. 2017-12-01 Based on the rate of expansion of the solar wind, the plasma should cool rapidly as a function of distance to the Sun. Observations show this is not the case. In this work, a magnetic pumping model is developed as a possible explanation for the heating and the generation of power-law distribution functions observed in the solar wind plasma. Most previous studies in this area focus on the role that the dissipation of turbulent energy on microscopic kinetic scales plays in the overall heating of the plasma. However, with magnetic pumping, particles are energized by the largest-scale turbulent fluctuations, thus bypassing the energy cascade. In contrast to other models, we include the pressure anisotropy term, providing a channel for the large-scale fluctuations to heat the plasma directly. A complete set of coupled differential equations describing the evolution, and energization, of the distribution function are derived, as well as an approximate closed-form solution. Numerical simulations using the VPIC kinetic code are applied to verify the model’s analytical predictions. The results of the model for realistic solar wind scenario are computed, where thermal streaming of particles are important for generating a phase shift between the magnetic perturbations and the pressure anisotropy. In turn, averaged over a pump cycle, the phase shift permits mechanical work to be converted directly to heat in the plasma. The results of this scenario show that magnetic pumping may account for a significant portion of the solar wind energization. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060037983&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060037983&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS">Solar Wind Features Responsible for Magnetic Storms and Substorms During the Declining Phase of the Solar Cycle: 197</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Tsurutani, B.; Arballo, J. 1994-01-01 We examine interplanetary data and geomagnetic activity indices during 1974 when two long-lasting solar wind corotating streams existed. We find that only 3 major storms occurred during 1974, and all were associated with coronal mass ejections. Each high speed stream was led by a shock, so the three storms had sudden commencements. Two of the 1974 major storms were associated with shock compression of preexisting southward fields and one was caused by southward fields within a magnetic cloud. Corotating streams were responsible for recurring moderate to weak magnetic storms. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28226210','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28226210">Real-Time Nanoscale Open-Circuit Voltage Dynamics of Perovskite Solar Cells.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Garrett, Joseph L; Tennyson, Elizabeth M; Hu, Miao; Huang, Jinsong; Munday, Jeremy N; Leite, Marina S 2017-04-12 Hybrid organic-inorganic perovskites based on methylammonium lead (MAPbI 3 ) are an emerging material with great potential for high-performance and low-cost photovoltaics. However, for perovskites to become a competitive and reliable solar cell technology their instability and spatial variation must be understood and controlled. While the macroscopic characterization of the devices as a function of time is very informative, a nanoscale identification of their real-time local optoelectronic response is still missing. Here, we implement a four-dimensional imaging method through illuminated heterodyne Kelvin probe force microscopy to spatially (<50 nm) and temporally (16 s/scan) resolve the voltage of perovskite solar cells in a low relative humidity environment. Local open-circuit voltage (V oc ) images show nanoscale sites with voltage variation >300 mV under 1-sun illumination. Surprisingly, regions of voltage that relax in seconds and after several minutes consistently coexist. Time-dependent changes of the local V oc are likely due to intragrain ion migration and are reversible at low injection level. These results show for the first time the real-time transient behavior of the V oc in perovskite solar cells at the nanoscale. Understanding and controlling the light-induced electrical changes that affect device performance are critical to the further development of stable perovskite-based solar technologies. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH31C2439U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH31C2439U">Reconnection-Driven Solar Polar Jets to be Encountered by Solar Probe Plus: Simulated In Situ Measurements and Data Analysis</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Uritsky, V. M.; Roberts, M. A.; Karpen, J. T.; DeVore, C. R. 2015-12-01 Solar polar jets are observed to originate in regions within the open field of solar coronal holes. These so called "anemone" regions are associated with an embedded dipole topology, consisting of a fan-separatrix and a spine line emanating from a null point occurring at the top of the dome shaped fan surface (Antiochos 1996). In this study, we analyze simulations using the Adaptively Refined MHD Solver (ARMS) that take into account gravity, solar wind, and spherical geometry to generate polar jets by reconnection between a twisted embedded bipole and the surrounding open field (Karpen et al. 2015). These simulations confirm and extend previous Cartesian studies of polar jets based on this mechanism (Pariat et al. 2009, 2010, 2015), as well as extending the analyses from our previous work (Roberts et al. 2014,2015) out to radial distances that will be sampled by Solar Probe Plus. Focusing on the plasma density, velocity, magnetic field, and current density, we interpolate the adaptively gridded simulation data onto a regular grid, and analyze the signatures that the jet produces as it propagates outward from the solar surface into the inner heliosphere. We also conduct simulated spacecraft fly-throughs of the jet in several different velocity regimes, illustrating the signatures that Solar Probe Plus may encounter in situ as the jet propagates into the heliosphere. The trans-Alfvénic nature of the jet front is confirmed by temporally differencing the plasma mass density and comparing the result with the local Alfvén speed. Our analysis confirms the presence of a reconnection driven magnetic turbulence in the simulated plasma jet, finding spatial correlations of magnetic fluctuations inside the jet to be in agreement with the scaling model of MHD turbulence. The turbulence cascade is supported by multiscale current sheets combined with filamentary structures representing fluid vorticies. The spatial orientation of these current sheets, combined with the anisotropy </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850021585&hterms=vector+fields&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dvector%2Bfields','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850021585&hterms=vector+fields&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dvector%2Bfields">Solar monochromatic images in magneto-sensitive spectral lines and maps of vector magnetic fields</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Shihui, Y.; Jiehai, J.; Minhan, J. 1985-01-01 A new method which allows by use of the monochromatic images in some magneto-sensitive spectra line to derive both the magnetic field strength as well as the angle between magnetic field lines and line of sight for various places in solar active regions is described. In this way two dimensional maps of vector magnetic fields may be constructed. This method was applied to some observational material and reasonable results were obtained. In addition, a project for constructing the three dimensional maps of vector magnetic fields was worked out. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4820001T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4820001T">Magnetic Properties of Solar Active Regions that Govern Large Solar Flares and Eruptions</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Toriumi, Shin; Schrijver, Carolus J.; Harra, Louise; Hudson, Hugh S.; Nagashima, Kaori 2017-08-01 Strong flares and CMEs are often produced from active regions (ARs). In order to better understand the magnetic properties and evolutions of such ARs, we conducted statistical investigations on the SDO/HMI and AIA data of all flare events with GOES levels >M5.0 within 45 deg from the disk center for 6 years from May 2010 (from the beginning to the declining phase of solar cycle 24). Out of the total of 51 flares from 29 ARs, more than 80% have delta-sunspots and about 15% violate Hale’s polarity rule. We obtained several key findings including (1) the flare duration is linearly proportional to the separation of the flare ribbons (i.e., scale of reconnecting magnetic fields) and (2) CME-eruptive events have smaller sunspot areas. Depending on the magnetic properties, flaring ARs can be categorized into several groups, such as spot-spot, in which a highly-sheared polarity inversion line is formed between two large sunspots, and spot-satellite, where a newly-emerging flux next to a mature sunspot triggers a compact flare event. These results point to the possibility that magnetic structures of the ARs determine the characteristics of flares and CMEs. In the presentation, we will also show new results from the systematic flux emergence simulations of delta-sunspot formation and discuss the evolution processes of flaring ARs. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750049947&hterms=density+buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddensity%2Bbuoyancy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750049947&hterms=density+buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddensity%2Bbuoyancy">The generation of magnetic fields in astrophysical bodies. X - Magnetic buoyancy and the solar dynamo</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Parker, E. N. 1975-01-01 The magnetic field appearing as bipolar magnetic regions at the surface of the sun represents the lines of force from a general azimuthal field of the order of 100 gauss somewhere beneath the surface. The amplification time, as a consequence of the nonuniform rotation, is of the order of 10 years. But magnetic buoyancy brings the azimuthal field up through much of the convective zone in a time rather less than 10 years, raising the question of where the azimuthal field can be retained long enough to be amplified. We show that magnetic fields can be retained for long periods of time in the stable radiative region beneath the convective zone, but unfortunately the solar dynamo cannot function there because turbulent diffusion is an essential part of its operation. The only possible conclusion appears to be that the dynamo operates principally in the very lowest levels of the convective zone at depths of 150,000 km or more, where the gas density is 0.1 g/cu cm, and the fields are limited to 50 gauss. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH51A2442W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH51A2442W">High-frequency Plasma Waves Associated with Magnetic Reconnection in the Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, Y. 2015-12-01 Activities of high-frequency plasma waves associated with magnetic reconnection in the solar wind observed by Time Domain Sampler (TDS) experiments on STEREO/WAVES are preliminarily analyzed. The TDS instrument can provide burst mode electric fields data with as long as 16384 sample points at 250 kHz sampling rate. In all 1120 suspected reconnection events, it is found that the most commonly occurred waves are neither ion acoustic waves, electrostatic solitary waves, nor Langmuir/upper hybrid waves, but Bernstein-like waves with harmonics of the electron cyclotron frequency. In addition, to each type of waves, Langmuir/upper hybrid waves reveal the largest occurrence rate in the reconnection region than in the ambient solar wind. These results indicate that Bernstein-like waves and Langmuir/upper hybrid waves might play important roles in the reconnection associated particle heating processes and they might also influence the dissipation of magnetic reconnection. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Ge%26Ae..56..393K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Ge%26Ae..56..393K">Skin-layer of the eruptive magnetic flux rope in large solar flares</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kichigin, G. N.; Miroshnichenko, L. I.; Sidorov, V. I.; Yazev, S. A. 2016-07-01 The analysis of observations of large solar flares made it possible to propose a hypothesis on existence of a skin-layer in magnetic flux ropes of coronal mass ejections. On the assumption that the Bohm coefficient determines the diffusion of magnetic field, an estimate of the skin-layer thickness of ~106 cm is obtained. According to the hypothesis, the electric field of ~0.01-0.1 V/cm, having the nonzero component along the magnetic field of flux rope, arises for ~5 min in the surface layer of the eruptive flux rope during its ejection into the upper corona. The particle acceleration by the electric field to the energies of ~100 MeV/nucleon in the skin-layer of the flux rope leads to their precipitation along field lines to footpoints of the flux rope. The skin-layer presence induces helical or oval chromospheric emission at the ends of flare ribbons. The emission may be accompanied by hard X-ray radiation and by the production of gamma-ray line at the energy of 2.223 MeV (neutron capture line in the photosphere). The magnetic reconnection in the corona leads to a shift of the skin-layer of flux rope across the magnetic field. The area of precipitation of accelerated particles at the flux-rope footpoints expands in this case from the inside outward. This effect is traced in the chromosphere and in the transient region as the expanding helical emission structures. If the emission extends to the spot, a certain fraction of accelerated particles may be reflected from the magnetic barrier (in the magnetic field of the spot). In the case of exit into the interplanetary space, these particles may be recorded in the Earth's orbit as solar proton events. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSH13C2268L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSH13C2268L">On the Cause of Solar Differential Rotations in the Solar Interior and Near the Solar Surface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lyu, L. 2012-12-01 A theoretical model is proposed to explain the cause of solar differential rotations observed in the solar interior and near the solar surface. We propose that the latitudinal differential rotation in the solar convection zone is a manifestation of an easterly wind in the mid latitude. The speed of the easterly wind is controlled by the magnitude of the poleward temperature gradient in the lower part of the solar convection zone. The poleward temperature gradient depends on the orientation and strength of the magnetic fields at different latitudes in the solar convection zone. The north-south asymmetry in the wind speed can lead to north-south asymmetry in the evolution of the solar cycle. The easterly wind is known to be unstable for a west-to-east rotating star or planet. Based on the observed differential rotations in the solar convection zone, we can estimate the easterly wind speed at about 60-degree latitude and determine the azimuthal wave number of the unstable wave modes along the zonal flow. The lowest azimuthal wave number is about m=7~8. This result is consistent with the average width of the elephant-trunk coronal hole shown in the solar X-ray images. The nonlinear evolution of the unstable easterly wind can lead to transpolar migration of coronal holes and can change the poloidal magnetic field in a very efficient way. In the study of radial differential rotation near the solar surface, we propose that the radial differential rotation depends on the radial temperature gradient. The radial temperature gradient depends on the magnetic field structure above the solar surface. The non-uniform magnetic field distribution above the solar surface can lead to non-uniform radial convections and formation of magnetic flux rope at different spatial scales. The possible cause of continuous formation and eruption of prominences near an active region will also be discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AIPC.1942n0046M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AIPC.1942n0046M">Magnetic and optical effects in TiO2 based dye sensitized solar cells</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kannan U., M.; Jammalamadaka, S. Narayana 2018-04-01 We report on the magnetic effects on the solar cell efficiency of TiO2 based dye sensitized solar cells (DSSC). The strong spin orbit coupling of rare earth Ho3+ ions introduced by the addition of Ho2O3 into the photoanode resulted in a 28% enhancement in the power conversion efficiency of DSSC. Such an enhancement in the efficiency may be attributed to the improved lifetime of photo generated excitons as a result of the accelerated intersystem crossing phenomenon. This observation is supported by our photoluminescence (PL) measurements where we could observe a decrease in the photo emission intensity with the addition of Ho2O3. In addition, we have used a low magnetic field of 100 Oe to further enhance the overall efficiency to 5.6%, which in turn proves that the Lorentz force plays a significant role in magnetic field controlled charge transport in DSSC. Finally, we have carried out a transfer matrix model based theoretical simulation for studying the optical properties of the multilayer device stack. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSH51C2510W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSH51C2510W">A Solar Eruption from a Weak Magnetic Field Region with Relatively Strong Geo-Effectiveness</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, R. 2017-12-01 A moderate flare eruption giving rise to a series of geo-effectiveness on 2015 November 4 caught our attentions, which originated from a relatively weak magnetic field region. The associated characteristics near the Earth are presented, which indicates that the southward magnetic field in the sheath and the ICME induced a geomagnetic storm sequence with a Dst global minimum of 90 nT. The ICME is indicated to have a small inclination angle by using a Grad-Shafranov technique, and corresponds to the flux rope (FR) structure horizontally lying on the solar surface. A small-scale magnetic cancelling feature was detected which is beneath the FR and is co-aligned with the Atmospheric Imaging Assembly (AIA) EUV brightening prior to the eruption. Various magnetic features for space-weather forecasting are computed by using a data product from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) called Space-weather HMI Active Region Patches (SHARPs), which help us identify the changes of the photospheric magnetic fields during the magnetic cancellation process and prove that the magnetic reconnection associated with the flux cancellation is driven by the magnetic shearing motion on the photosphere. An analysis on the distributions at different heights of decay index is carried out. Combining with a filament height estimation method, the configurations of the FR is identified and a decay index critical value n = 1 is considered to be more appropriate for such a weak magnetic field region. Through a comprehensive analysis to the trigger mechanisms and conditions of the eruption, a clearer scenario of a CME from a relatively weak region is presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ARep...62..281P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ARep...62..281P">The Nature of Variations in Anomalies of the Chemical Composition of the Solar Corona with the 11-Year Cycle</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pipin, V. V.; Tomozov, V. M. 2018-04-01 Evidence that the distribution of the abundances of admixtures with low first-ionization potentials (FIP < 10 eV) in the lower solar corona could be associated with the typology of the largescale magnetic field is presented. Solar observations show an enhancement in the abundances of elements with low FIPs compared to elements with high FIPs (>10 eV) in active regions and closed magnetic configurations in the lower corona. Observations with the ULYSSES spacecraft and at the Stanford Solar Observatory have revealed strong correlations between the manifestation of the FIP effect in the solar wind, the strength of the open magnetic flux (without regard to sign), and the ratio of the large-scale toroidal and poloidal magnetic fields at the solar surface. Analyses of observations of the Sun as a star show that the enhancement of the abundances of admixtures with low FIPs in the corona compared to their abundances in the photosphere (the FIP effect) is closely related to the solar-activity cycle and also with variations in the topology of the large-scale magnetic field. A possible mechanism for the relationship between the FIP effect and the spectral type of a star is discussed in the framework of solar-stellar analogies. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22667485-comparison-magnetic-properties-magnetic-cloud-its-solar-source-april','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22667485-comparison-magnetic-properties-magnetic-cloud-its-solar-source-april">COMPARISON OF MAGNETIC PROPERTIES IN A MAGNETIC CLOUD AND ITS SOLAR SOURCE ON 2013 APRIL 11–14</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Vemareddy, P.; Möstl, C.; Amerstorfer, T. 2016-09-01 In the context of the Sun–Earth connection of coronal mass ejections and magnetic flux ropes (MFRs), we studied the solar active region (AR) and the magnetic properties of magnetic cloud (MC) event during 2013 April 14–15. We use in situ observations from the Advanced Composition Explorer and source AR measurements from the Solar Dynamics Observatory . The MCs magnetic structure is reconstructed from the Grad–Shafranov method, which reveals a northern component of the axial field with left handed helicity. The MC invariant axis is highly inclined to the ecliptic plane pointing northward and is rotated by 117° with respect tomore » the source region PIL. The net axial flux and current in the MC are comparatively higher than from the source region. Linear force-free alpha distribution (10{sup −7}–10{sup −6} m{sup −1}) at the sigmoid leg matches the range of twist number in the MC of 1–2 au MFR. The MFR is nonlinear force-free with decreasing twist from the axis (9 turns/au) toward the edge. Therefore, a Gold–Hoyle (GH) configuration, assuming a constant twist, is more consistent with the MC structure than the Lundquist configuration of increasing twist from the axis to boundary. As an indication of that, the GH configuration yields a better fitting to the global trend of in situ magnetic field components, in terms of rms, than the Lundquist model. These cylindrical configurations improved the MC fitting results when the effect of self-similar expansion of MFR was considered. For such twisting behavior, this study suggests an alternative fitting procedure to better characterize the MC magnetic structure and its source region links.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150018311','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150018311">Time Delay Between Dst Index and Magnetic Storm Related Structure in the Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Osherovich, Vladimir A.; Fainberg, Joseph 2015-01-01 Benson et al. (2015, this volume) selected 10 large magnetic storms, with associated Dst minimum values less than or equal to -100 nT, for which high-latitude topside ionospheric electron density profiles are available from topside-sounder satellites. For these 10 storms, we performed a superposition of Dst and interplanetary parameters B, v, N(sub p) and T(sub p). We have found that two interplanetary parameters, namely B and v, are sufficient to reproduce Dst with correlation coefficient cc approximately 0.96 provided that the interplanetary parameter times are taken 0.15 days earlier than the associated Dst times. Thus we have found which part of the solar wind is responsible for each phase of the magnetic storm. This result is also verified for individual storms as well. The total duration of SRS (storm related structure in the solar wind) is 4 - 5 days which is the same as the associated Dst interval of the magnetic storm. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663224-large-scale-plume-class-solar-flare','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663224-large-scale-plume-class-solar-flare">A Large-scale Plume in an X-class Solar Flare</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Fleishman, Gregory D.; Nita, Gelu M.; Gary, Dale E. Ever-increasing multi-frequency imaging of solar observations suggests that solar flares often involve more than one magnetic fluxtube. Some of the fluxtubes are closed, while others can contain open fields. The relative proportion of nonthermal electrons among those distinct loops is highly important for understanding energy release, particle acceleration, and transport. The access of nonthermal electrons to the open field is also important because the open field facilitates the solar energetic particle (SEP) escape from the flaring site, and thus controls the SEP fluxes in the solar system, both directly and as seed particles for further acceleration. The large-scale fluxtubes aremore » often filled with a tenuous plasma, which is difficult to detect in either EUV or X-ray wavelengths; however, they can dominate at low radio frequencies, where a modest component of nonthermal electrons can render the source optically thick and, thus, bright enough to be observed. Here we report the detection of a large-scale “plume” at the impulsive phase of an X-class solar flare, SOL2001-08-25T16:23, using multi-frequency radio data from Owens Valley Solar Array. To quantify the flare’s spatial structure, we employ 3D modeling utilizing force-free-field extrapolations from the line of sight SOHO /MDI magnetograms with our modeling tool GX-Simulator. We found that a significant fraction of the nonthermal electrons that accelerated at the flare site low in the corona escapes to the plume, which contains both closed and open fields. We propose that the proportion between the closed and open fields at the plume is what determines the SEP population escaping into interplanetary space.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...854...80H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...854...80H">Magnetic Braids in Eruptions of a Spiral Structure in the Solar Atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Huang, Zhenghua; Xia, Lidong; Nelson, Chris J.; Liu, Jiajia; Wiegelmann, Thomas; Tian, Hui; Klimchuk, James A.; Chen, Yao; Li, Bo 2018-02-01 We report on high-resolution imaging and spectral observations of eruptions of a spiral structure in the transition region, which were taken with the Interface Region Imaging Spectrograph, and the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The eruption coincided with the appearance of two series of jets, with velocities comparable to the Alfvén speeds in their footpoints. Several pieces of evidence of magnetic braiding in the eruption are revealed, including localized bright knots, multiple well-separated jet threads, transition region explosive events, and the fact that all three of these are falling into the same locations within the eruptive structures. Through analysis of the extrapolated 3D magnetic field in the region, we found that the eruptive spiral structure corresponded well to locations of twisted magnetic flux tubes with varying curl values along their lengths. The eruption occurred where strong parallel currents, high squashing factors, and large twist numbers were obtained. The electron number density of the eruptive structure is found to be ∼3 × 1012 cm‑3, indicating that a significant amount of mass could be pumped into the corona by the jets. Following the eruption, the extrapolations revealed a set of seemingly relaxed loops, which were visible in the AIA 94 Å channel, indicating temperatures of around 6.3 MK. With these observations, we suggest that magnetic braiding could be part of the mechanisms explaining the formation of solar eruption and the mass and energy supplement to the corona. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22370566-nonlinear-force-free-field-modeling-solar-magnetic-carpet-comparison-sdo-hmi-sunrise-imax-observations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22370566-nonlinear-force-free-field-modeling-solar-magnetic-carpet-comparison-sdo-hmi-sunrise-imax-observations">Nonlinear force-free field modeling of the solar magnetic carpet and comparison with SDO/HMI and Sunrise/IMAX observations</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Chitta, L. P.; Kariyappa, R.; Van Ballegooijen, A. A. 2014-10-01 In the quiet solar photosphere, the mixed polarity fields form a magnetic carpet that continuously evolves due to dynamical interaction between the convective motions and magnetic field. This interplay is a viable source to heat the solar atmosphere. In this work, we used the line-of-sight (LOS) magnetograms obtained from the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory, and the Imaging Magnetograph eXperiment instrument on the Sunrise balloon-borne observatory, as time-dependent lower boundary conditions, to study the evolution of the coronal magnetic field. We use a magneto-frictional relaxation method, including hyperdiffusion, to produce a time series of three-dimensional nonlinearmore » force-free fields from a sequence of photospheric LOS magnetograms. Vertical flows are added up to a height of 0.7 Mm in the modeling to simulate the non-force-freeness at the photosphere-chromosphere layers. Among the derived quantities, we study the spatial and temporal variations of the energy dissipation rate and energy flux. Our results show that the energy deposited in the solar atmosphere is concentrated within 2 Mm of the photosphere and there is not sufficient energy flux at the base of the corona to cover radiative and conductive losses. Possible reasons and implications are discussed. Better observational constraints of the magnetic field in the chromosphere are crucial to understand the role of the magnetic carpet in coronal heating.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22518570-forming-chondrites-solar-nebula-magnetically-induced-turbulence','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22518570-forming-chondrites-solar-nebula-magnetically-induced-turbulence">FORMING CHONDRITES IN A SOLAR NEBULA WITH MAGNETICALLY INDUCED TURBULENCE</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Hasegawa, Yasuhiro; Turner, Neal J.; Masiero, Joseph Chondritic meteorites provide valuable opportunities to investigate the origins of the solar system. We explore impact jetting as a mechanism of chondrule formation and subsequent pebble accretion as a mechanism of accreting chondrules onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is ≤5 times more massive than the minimum-mass solar nebula at a ≃ 2–3 au and parent bodies of chondrites are ≤10{sup 24} g (≤500 km in radius) in the solar nebula, impact jetting and subsequent pebble accretion can reproduce a number ofmore » properties of the meteoritic data. The properties include the present asteroid belt mass, the formation timescale of chondrules, and the magnetic field strength of the nebula derived from chondrules in Semarkona. Since this scenario requires a first generation of planetesimals that trigger impact jetting and serve as parent bodies to accrete chondrules, the upper limit of parent bodies’ masses leads to the following implications: primordial asteroids that were originally ≥10{sup 24} g in mass were unlikely to contain chondrules, while less massive primordial asteroids likely had a chondrule-rich surface layer. The scenario developed from impact jetting and pebble accretion can therefore provide new insights into the origins of the solar system.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980151083','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980151083">Study of Magnetic Structure in the Solar Photosphere and Chromosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Noyes, Robert W.; Avrett, Eugene; Nisenson, Peter; Uitenbroek, Han; vanBallegooijen, Adriaan 1998-01-01 This grant funded an observational and theoretical program to study the structure and dynamics of the solar photosphere and low chromosphere, and the spectral signatures that result. The overall goal is to learn about mechanisms that cause heating of the overlying atmosphere, and produce variability of solar emission in spectral regions important for astrophysics and space physics. The program exploited two new ground-based observational capabilities: one using the Swedish Solar Telescope on La Palma for very high angular resolution observations of the photospheric intensity field (granulation) and proxies of the magnetic field (G-band images); and the other using the Near Infrared Magnetograph at the McMath-Pierce Solar Facility to map the spatial variation and dynamic behavior of the solar temperature minimum region using infrared CO lines. We have interpreted these data using a variety of theoretical and modelling approaches, some developed especially for this project. Previous annual reports cover the work done up to 31 May 1997. This final report summarizes our work for the entire period, including the period of no-cost extension from 1 June 1997 through September 30 1997. In Section 2 we discuss observations and modelling of the photospheric flowfields and their consequences for heating of the overlying atmosphere, and in Section 3 we discuss imaging spectroscopy of the CO lines at 4.67 mu. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4354106','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4354106">Full-Sun observations for identifying the source of the slow solar wind</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Brooks, David H.; Ugarte-Urra, Ignacio; Warren, Harry P. 2015-01-01 Fast (>700 km s−1) and slow (~400 km s−1) winds stream from the Sun, permeate the heliosphere and influence the near-Earth environment. While the fast wind is known to emanate primarily from polar coronal holes, the source of the slow wind remains unknown. Here we identify possible sites of origin using a slow solar wind source map of the entire Sun, which we construct from specially designed, full-disk observations from the Hinode satellite, and a magnetic field model. Our map provides a full-Sun observation that combines three key ingredients for identifying the sources: velocity, plasma composition and magnetic topology and shows them as solar wind composition plasma outflowing on open magnetic field lines. The area coverage of the identified sources is large enough that the sum of their mass contributions can explain a significant fraction of the mass loss rate of the solar wind. PMID:25562705 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM13E4214E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM13E4214E">Ulysses Observations of Tripolar Guide-Magnetic Field Perturbations Across Solar Wind Reconnection Exhausts</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Eriksson, S.; Peng, B.; Markidis, S.; Gosling, J. T.; McComas, D. J.; Lapenta, G.; Newman, D. L. 2014-12-01 We report observations from 15 solar wind reconnection exhausts encountered along the Ulysses orbit beyond 4 AU in 1996-1999 and 2002-2005. The events, which lasted between 17 and 45 min, were found at heliospheric latitudes between -36o and 21o with one event detected as high as 58o. All events shared a common characteristic of a tripolar guide-magnetic field perturbation being detected across the observed exhausts. The signature consists of an enhanced guide field magnitude within the exhaust center and two regions of significantly depressed guide-fields adjacent to the center region. The events displayed magnetic field shear angles as low as 37o with a mean of 89o. This corresponds to a strong external guide field relative to the anti-parallel reconnecting component of the magnetic field with a mean ratio of 1.3 and a maximum ratio of 3.1. A 2-D kinetic reconnection simulation for realistic solar wind conditions reveals that tripolar guide fields form at current sheets in the presence of multiple X-lines as two magnetic islands interact with one another for such strong guide fields. The Ulysses observations are also compared with the results of a 3-D kinetic simulation of multiple flux ropes in a strong guide field. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSM41C..07Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSM41C..07Y">Experimental Simulation of Solar Wind Interaction with MagneticDipole Fields above Insulating Surfaces</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Yeo, L. H.; Han, J.; Wang, X.; Werner, G.; Deca, J.; Munsat, T.; Horanyi, M. 2017-12-01 Magnetic anomalies on the surfaces of airless bodies such as the Moon interact with the solar wind, resulting in both magnetic and electrostatic deflection/reflection of thecharged particles. Consequently, surface charging in these regions will be modified. Using the Colorado Solar Wind Experiment facility, this interaction is investigated with high-energy flowing plasmas (100-800 eV beam ions) that are incident upon a magnetic dipole (0.13 T) embedded under various insulating surfaces. The dipole moment is perpendicular to the surface. Using an emissive probe, 2D plasma potential profiles are obtained above the surface. In the dipole lobe regions, the surfaces are charged to significantly positive potentials due to the impingement of the unmagnetized ions while the electrons are magnetically shielded. At low ion beam energies, the results agree with the theoretical predictions, i.e., the surface potential follows the energy of the beam ions in eV. However, at high energies, the surface potentials in the electron-shielded regions are significantly lower than the beam energies. A series of investigations have been conducted and indicate that the surface properties (e.g., modified surface conductance, ion induced secondary electrons and electron-neutral collision at the surface) are likely to play a role in determining the surface potential. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830016163','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830016163">Solar maximum mission: Ground support programs at the Harvard Radio Astronomy Station</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Maxwell, A. 1983-01-01 Observations of the spectral characteristics of solar radio bursts were made with new dynamic spectrum analyzers of high sensitivity and high reliability, over the frequency range 25-580 MHz. The observations also covered the maximum period of the current solar cycle and the period of international cooperative programs designated as the Solar Maximum Year. Radio data on shock waves generated by solar flares were combined with optical data on coronal transients, taken with equipment on the SMM and other satellites, and then incorporated into computer models for the outward passage of fast-mode MHD shocks through the solar corona. The MHD models are non-linear, time-dependent and for the most recent models, quasi-three-dimensional. They examine the global response of the corona for different types of input pulses (thermal, magnetic, etc.) and for different magnetic topologies (for example, open and closed fields). Data on coronal shocks and high-velocity material ejected from solar flares have been interpreted in terms of a model consisting of three main velocity regimes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110007246&hterms=sol&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsol','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110007246&hterms=sol&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsol">Erratum to "Solar Sources and Geospace Consequences of Interplanetary Magnetic Clouds Observed During Solar Cycle 23-Paper 1" [J. Atmos. Sol.-Terr. Phys. 70(2-4) (2008) 245-253</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Gopalswamy, N.; Akiyama, S.; Yashiro, S.; Michalek, G.; Lepping, R. P. 2009-01-01 One of the figures (Fig. 4) in "Solar sources and geospace consequences of interplanetary magnetic Clouds observed during solar cycle 23 -- Paper 1" by Gopalswamy et al. (2008, JASTP, Vol. 70, Issues 2-4, February 2008, pp. 245-253) is incorrect because of a software error in t he routine that was used to make the plot. The source positions of various magnetic cloud (MC) types are therefore not plotted correctly. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009A%26A...508..979I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009A%26A...508..979I">Flow instabilities of magnetic flux tubes. IV. Flux storage in the solar overshoot region</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Işık, E.; Holzwarth, V. 2009-12-01 Context: Flow-induced instabilities of magnetic flux tubes are relevant to the storage of magnetic flux in the interiors of stars with outer convection zones. The stability of magnetic fields in stellar interiors is of importance to the generation and transport of solar and stellar magnetic fields. Aims: We consider the effects of material flows on the dynamics of toroidal magnetic flux tubes located close to the base of the solar convection zone, initially within the overshoot region. The problem is to find the physical conditions in which magnetic flux can be stored for periods comparable to the dynamo amplification time, which is of the order of a few years. Methods: We carry out nonlinear numerical simulations to investigate the stability and dynamics of thin flux tubes subject to perpendicular and longitudinal flows. We compare the simulations with the results of simplified analytical approximations. Results: The longitudinal flow instability induced by the aerodynamic drag force is nonlinear in the sense that the growth rate depends on the perturbation amplitude. This result is consistent with the predictions of linear theory. Numerical simulations without friction show that nonlinear Parker instability can be triggered below the linear threshold of the field strength, when the difference in superadiabaticity along the tube is sufficiently large. A localised downflow acting on a toroidal tube in the overshoot region leads to instability depending on the parameters describing the flow, as well as the magnetic field strength. We determined ranges of the flow parameters for which a linearly Parker-stable magnetic flux tube is stored in the middle of the overshoot region for a period comparable to the dynamo amplification time. Conclusions: The longitudinal flow instability driven by frictional interaction of a flux tube with its surroundings is relevant to determining the storage time of magnetic flux in the solar overshoot region. The residence time for </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......314C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......314C">Non-Potential Magnetic Fields and Magnetic Reconnection In Low Collisional Plasmas-Discovery of Solar EUV Mini-Sigmoids and Development of Novel In-Space Propulsion Systems</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chesny, David Magnetic reconnection is the source of many of the most powerful explosions of astrophysical plasmas in the universe. Blazars, magnetars, stellar atmospheres, and planetary magnetic fields have all been shown to be primary sites of strong reconnection events. For studying the fundamental physics behind this process, the solar atmosphere is our most accessible laboratory setting. Magnetic reconnection resulting from non-potential fields leads to plasma heating and particle acceleration, often in the form of explosive activity, contributing to coronal heating and the solar wind. Large-scale non-potential (sigmoid) fields in the solar atmosphere are poorly understood due to their crowded neighborhoods. For the first time, small-scale, non-potential loop structures have been observed in quiet Sun EUV observations. Fourteen unique mini-sigmoid events and three diffuse non-potential loops have been discovered, suggesting a multi-scaled self-similarity in the sigmoid formation process. These events are on the order of 10 arcseconds in length and do not appear in X-ray emissions, where large-scale sigmoids are well documented. We have discovered the first evidence of sigmoidal structuring in EUV bright point phenomena, which are prolific events in the solar atmosphere. Observations of these mini-sigmoids suggest that they are being formed via tether-cutting reconnection, a process observed to occur at active region scales. Thus, tether-cutting is suggested to be ubiquitous throughout the solar atmosphere. These dynamics are shown to be a function of the free magnetic energy in the quiet Sun network. Recently, the reconnection process has been reproduced in Earth-based laboratory tokamaks. Easily achievable magnetic field configurations can induce reconnection and result in ion acceleration. Here, magnetic reconnection is utilized as the plasma acceleration mechanism for a theoretical propulsion system. The theory of torsional spine reconnection is shown to result in ion </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1440480-magnetic-pumping-source-particle-heating-power-law-distributions-solar-wind','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1440480-magnetic-pumping-source-particle-heating-power-law-distributions-solar-wind">Magnetic Pumping as a Source of Particle Heating and Power-Law Distributions in the Solar Wind</a> <a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a> Lichko, Emily Rose; Egedal, Jan; Daughton, William Scott; ... 2017-11-27 Based on the rate of expansion of the solar wind, the plasma should cool rapidly as a function of distance to the Sun. Observations show this is not the case. In this work, a magnetic pumping model is developed as a possible explanation for the heating and the generation of power-law distribution functions observed in the solar wind plasma. Most previous studies in this area focus on the role that the dissipation of turbulent energy on microscopic kinetic scales plays in the overall heating of the plasma. However, with magnetic pumping, particles are energized by the largest-scale turbulent fluctuations, thusmore » bypassing the energy cascade. In contrast to other models, we include the pressure anisotropy term, providing a channel for the large-scale fluctuations to heat the plasma directly. A complete set of coupled differential equations describing the evolution, and energization, of the distribution function are derived, as well as an approximate closed-form solution. Numerical simulations using the VPIC kinetic code are applied to verify the model's analytical predictions. The results of the model for realistic solar wind scenario are computed, where thermal streaming of particles are important for generating a phase shift between the magnetic perturbations and the pressure anisotropy. In turn, averaged over a pump cycle, the phase shift permits mechanical work to be converted directly to heat in the plasma. Here, the results of this scenario show that magnetic pumping may account for a significant portion of the solar wind energization.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1440480-magnetic-pumping-source-particle-heating-power-law-distributions-solar-wind','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1440480-magnetic-pumping-source-particle-heating-power-law-distributions-solar-wind">Magnetic Pumping as a Source of Particle Heating and Power-Law Distributions in the Solar Wind</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Lichko, Emily Rose; Egedal, Jan; Daughton, William Scott Based on the rate of expansion of the solar wind, the plasma should cool rapidly as a function of distance to the Sun. Observations show this is not the case. In this work, a magnetic pumping model is developed as a possible explanation for the heating and the generation of power-law distribution functions observed in the solar wind plasma. Most previous studies in this area focus on the role that the dissipation of turbulent energy on microscopic kinetic scales plays in the overall heating of the plasma. However, with magnetic pumping, particles are energized by the largest-scale turbulent fluctuations, thusmore » bypassing the energy cascade. In contrast to other models, we include the pressure anisotropy term, providing a channel for the large-scale fluctuations to heat the plasma directly. A complete set of coupled differential equations describing the evolution, and energization, of the distribution function are derived, as well as an approximate closed-form solution. Numerical simulations using the VPIC kinetic code are applied to verify the model's analytical predictions. The results of the model for realistic solar wind scenario are computed, where thermal streaming of particles are important for generating a phase shift between the magnetic perturbations and the pressure anisotropy. In turn, averaged over a pump cycle, the phase shift permits mechanical work to be converted directly to heat in the plasma. Here, the results of this scenario show that magnetic pumping may account for a significant portion of the solar wind energization.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900049544&hterms=organization+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dorganization%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900049544&hterms=organization+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dorganization%2Bstructure">The structure of the white-light corona and the large-scale solar magnetic field</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Sime, D. G.; Mccabe, M. K. 1990-01-01 The large-scale density structure of the white-light solar corona is compared to the organization of the solar magnetic field as identified by the appearance of neutral lines in the photosphere to examine whether any consistent relationship exists between the two. During the period covering Carrington rotations 1717 to 1736 brightness enhancements in the low corona tend to lie over the global neutral sheet identified in the photospheric magnetic field. The brightest of these enhancements are associated with neutral lines throguh active regions. These associations are not 1-1, but do hold both in stable and evolving conditions of the corona. A significant number of long-lived neutral lines is found, including filaments seen in H-alpha, for which there are not coronal enhancements. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21460113-magnetic-energy-spectra-solar-active-regions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21460113-magnetic-energy-spectra-solar-active-regions">MAGNETIC ENERGY SPECTRA IN SOLAR ACTIVE REGIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Abramenko, Valentyna; Yurchyshyn, Vasyl Line-of-sight magnetograms for 217 active regions (ARs) with different flare rates observed at the solar disk center from 1997 January until 2006 December are utilized to study the turbulence regime and its relationship to flare productivity. Data from the SOHO/MDI instrument recorded in the high-resolution mode and data from the BBSO magnetograph were used. The turbulence regime was probed via magnetic energy spectra and magnetic dissipation spectra. We found steeper energy spectra for ARs with higher flare productivity. We also report that both the power index, {alpha}, of the energy spectrum, E(k) {approx} k{sup -}{alpha}, and the total spectral energy,more » W = {integral}E(k)dk, are comparably correlated with the flare index, A, of an AR. The correlations are found to be stronger than those found between the flare index and the total unsigned flux. The flare index for an AR can be estimated based on measurements of {alpha} and W as A = 10{sup b}({alpha}W){sup c}, with b = -7.92 {+-} 0.58 and c = 1.85 {+-} 0.13. We found that the regime of the fully developed turbulence occurs in decaying ARs and in emerging ARs (at the very early stage of emergence). Well-developed ARs display underdeveloped turbulence with strong magnetic dissipation at all scales.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730058132&hterms=generation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeneration%2By','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730058132&hterms=generation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeneration%2By">The generation and dissipation of solar and galactic magnetic fields.</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Parker, E. N. 1973-01-01 Turbulent diffusion of magnetic field plays an essential role in the generation of magnetic field in most astrophysical bodies. Review of what can be proved and what can be believed about the turbulent diffusion of magnetic field. Observations indicate the dissipation of magnetic field at rates that can be understood only in terms of turbulent diffusion. Theory shows that a large-scale weak magnetic field diffuses in a turbulent flow in the same way that smoke is mixed throughout the fluid by the turbulence. The small-scale fields (produced from the large-scale field by the turbulence) are limited in their growth by reconnection of field lines at neutral points, so that the turbulent mixing of field and fluid is not halted by them. Altogether, it appears that the mixing of field and fluid in the observed turbulent motions in the sun and in the Galaxy is unavoidable. Turbulent diffusion causes decay of the general solar fields in a decade or so, and of the galactic field in 100 m.y. to 1 b.y. It is concluded that continual dynamo action is implied by the observed existence of the fields. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160006713&hterms=magnetic+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmagnetic%2Bcooling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160006713&hterms=magnetic+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmagnetic%2Bcooling">An MHD Code for the Study of Magnetic Structures in the Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Allred, J. C.; MacNeice, P. J. 2015-01-01 We have developed a 2.5D MHD code designed to study how the solar wind influences the evolution of transient events in the solar corona and inner heliosphere. The code includes thermal conduction, coronal heating and radiative cooling. Thermal conduction is assumed to be magnetic field-aligned in the inner corona and transitions to a collisionless formulation in the outer corona. We have developed a stable method to handle field-aligned conduction around magnetic null points. The inner boundary is placed in the upper transition region, and the mass flux across the boundary is determined from 1D field-aligned characteristics and a 'radiative energy balance' condition. The 2.5D nature of this code makes it ideal for parameter studies not yet possible with 3D codes. We have made this code publicly available as a tool for the community. To this end we have developed a graphical interface to aid in the selection of appropriate options and a graphical interface that can process and visualize the data produced by the simulation. As an example, we show a simulation of a dipole field stretched into a helmet streamer by the solar wind. Plasmoids periodically erupt from the streamer, and we perform a parameter study of how the frequency and location of these eruptions changed in response to different levels of coronal heating. As a further example, we show the solar wind stretching a compact multi-polar flux system. This flux system will be used to study breakout coronal mass ejections in the presence of the solar wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840005021','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840005021">Solar cycle variations of the solar wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Crooker, N. U. 1983-01-01 Throughout the course of the past one and a half solar cycles, solar wind parameters measured near the ecliptic plane at 1 AU varied in the following way: speed and proton temperature have maxima during the declining phase and minima at solar minimum and are approximately anti-correlated with number density and electron temperature, while magnetic field magnitude and relative abundance of helium roughly follow the sunspot cycle. These variations are described in terms of the solar cycle variations of coronal holes, streamers, and transients. The solar wind signatures of the three features are discussed in turn, with special emphasis on the signature of transients, which is still in the process of being defined. It is proposed that magnetic clouds be identified with helium abundance enhancements and that they form the head of a transient surrounded by streamer like plasma, with an optional shock front. It is stressed that relative values of a parameter through a solar cycle should be compared beginning with the declining phase, especially in the case of magnetic field magnitude. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170007773&hterms=solar+geometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsolar%2Bgeometry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170007773&hterms=solar+geometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dsolar%2Bgeometry">Formation of Heliospheric Arcs of Slow Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Higginson, A. K.; Antiochos, S. K.; Devore, C. R.; Wyper, P. F.; Zurbuchen, T. H. 2017-01-01 A major challenge in solar and heliospheric physics is understanding the origin and nature of the so-called slow solar wind. The Sun's atmosphere is divided into magnetically open regions, known as coronal holes, where the plasma streams out freely and fills the solar system, and closed regions, where the plasma is confined to coronal loops. The boundary between these regions extends outward as the heliospheric current sheet (HCS). Measurements of plasma composition strongly imply that much of the slow wind consists of plasma from the closed corona that escapes onto open field lines, presumably by field-line opening or by interchange reconnection. Both of these processes are expected to release closed-field plasma into the solar wind within and immediately adjacent to the HCS. Mysteriously, however, slow wind with closed-field plasma composition is often observed in situ far from the HCS. We use high-resolution, three-dimensional, magnetohydrodynamic simulations to calculate the dynamics of a coronal hole with a geometry that includes a narrow corridor flanked by closed field and is driven by supergranule-like flows at the coronal-hole boundary. These dynamics produce giant arcs of closed-field plasma that originate at the open-closed boundary in the corona, but extend far from the HCS and span tens of degrees in latitude and longitude at Earth. We conclude that such structures can account for the long-puzzling slow-wind observations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654484-formation-heliospheric-arcs-slow-solar-wind','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654484-formation-heliospheric-arcs-slow-solar-wind">Formation of Heliospheric Arcs of Slow Solar Wind</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Higginson, A. K.; Zurbuchen, T. H.; Antiochos, S. K. A major challenge in solar and heliospheric physics is understanding the origin and nature of the so-called slow solar wind. The Sun’s atmosphere is divided into magnetically open regions, known as coronal holes, where the plasma streams out freely and fills the solar system, and closed regions, where the plasma is confined to coronal loops. The boundary between these regions extends outward as the heliospheric current sheet (HCS). Measurements of plasma composition strongly imply that much of the slow wind consists of plasma from the closed corona that escapes onto open field lines, presumably by field-line opening or by interchangemore » reconnection. Both of these processes are expected to release closed-field plasma into the solar wind within and immediately adjacent to the HCS. Mysteriously, however, slow wind with closed-field plasma composition is often observed in situ far from the HCS. We use high-resolution, three-dimensional, magnetohydrodynamic simulations to calculate the dynamics of a coronal hole with a geometry that includes a narrow corridor flanked by closed field and is driven by supergranule-like flows at the coronal-hole boundary. These dynamics produce giant arcs of closed-field plasma that originate at the open-closed boundary in the corona, but extend far from the HCS and span tens of degrees in latitude and longitude at Earth. We conclude that such structures can account for the long-puzzling slow-wind observations.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Ap%26SS.363...98X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Ap%26SS.363...98X">Modulations of the surface magnetic field on the intra-cycle variability of total solar irradiance</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xu, J. C.; Kong, D. F.; Li, F. Y. 2018-05-01 Solar photospheric magnetic field plays a dominant role in the variability of total solar irradiance (TSI). The modulation of magnetic flux at six specific ranges on TSI is characterized for the first time. The daily flux values of magnetic field at four ranges are extracted from MDI/ SOHO, together with daily flux of active regions (MF_{ar}) and quiet regions (MF_{qr}); the first four ranges (MF_{1-4}) are: 1.5-2.9, 2.9-32.0, 32.0-42.7, and 42.7-380.1 (× 10^{18} Mx per element), respectively. Cross-correlograms show that MF4, MF_{qr}, and MF_{ ar} are positively correlated with TSI, while MF2 is negatively correlated with TSI; the correlations between MF1, MF3 and TSI are insignificant. The bootstrapping tests confirm that the impact of MF4 on TSI is more significant than that of MF_{ar} and MF_{qr}, and MF_{ar} leads TSI by one rotational period. By extracting the rotational variations in the MFs and TSI, the modulations of the former on the latter at the solar rotational timescale are clearly illustrated and compared during solar maximum and minimum times, respectively. Comparison of the relative amplitudes of the long-term variation show that TSI is in good agreement with the variation of MF4 and MF_{ar}; besides, MF2 is in antiphase with TSI, and it lags the latter by about 1.5 years. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.2839S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.2839S">Triggering of solar magnetic eruptions on various size scales</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sterling, Alphonse A solar eruption that produces a coronal mass ejection (CME) together with a flare is driven by the eruption of a closed-loop magnetic arcade that has a sheared-field core. Before eruption, the sheared core envelops a polarity inversion line along which cool filament material may reside. The sheared-core arcade erupts when there is a breakdown in the balance between the confining downward-directed magnetic tension of the overall arcade field and the upward-directed force of the pent-up magnetic pressure of the sheared field in the core of the arcade. What triggers the breakdown in this balance in favor of the upward-directed force is still an unsettled question. We consider several eruption examples, using imaging data from the SoHO, TRACE and Hinode satellites, and other sources, along with information about the magnetic field of the erupting regions. In several cases, observations of large-scale eruptions, where the magnetic neutral line spans ˜ few ×10,000 km, are consistent with magnetic flux cancelation being the trigger to the eruption's onset, even though the amount of flux canceled is only ˜ few percent of the total magnetic flux of the erupting region. In several other cases, an initial compact (small size-scale) eruption occurs embedded inside of a larger closed magnetic loop system, so that the smaller eruption destabilizes and causes the eruption of the much larger system. In this way, small-scale eruptive events can result in eruption of much larger-scale systems. This work was funded by NASA's Science Mission Directorate thought the Living With a Star Targeted Research and Technology Program, the Supporting Research and Program, and the Hinode project. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.3356F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.3356F">The Morphology of the Solar Wind Magnetic Field Draping on the Dayside of Mars and Its Variability</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fang, Xiaohua; Ma, Yingjuan; Luhmann, Janet; Dong, Yaxue; Brain, David; Hurley, Dana; Dong, Chuanfei; Lee, Christina O.; Jakosky, Bruce 2018-04-01 The magnetic field draping pattern in the magnetosheath of Mars is of interest for what it tells us about both the solar wind interaction with the Mars obstacle and the use of the field measured there as a proxy for the upstream interplanetary magnetic field (IMF) clock angle. We apply a time-dependent, global magnetohydrodynamic model toward quantifying the spatial and temporal variations of the magnetic field draping direction on the Martian dayside above 500-km altitude. The magnetic field and plasma are self-consistently solved over one Mars rotation period, with the dynamics of the field morphology considered as the result of the rotation of the crustal field orientation. Our results show how the magnetic field direction on the plane perpendicular to the solar wind flow direction gradually departs from the IMF as the solar wind penetrates toward the obstacle and into the tail region. This clock angle departure occurs mainly inside the magnetic pileup region and tailward of the terminator plane, exhibiting significant dawn-dusk and north-south asymmetries. Inside the dayside sheath region, the field direction has the greatest departure from the IMF-perpendicular component direction downstream of the quasi-parallel bow shock, which for the nominal Parker spiral is over the dawn quadrant. Thus, the best region to obtain an IMF clock angle proxy is within the dayside magnetosheath at sufficiently high altitudes, particularly over subsolar and dusk sectors. Our results illustrate that the crustal field has only a mild influence on the magnetic field draping direction within the magnetosheath region. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhPl...25f3511U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhPl...25f3511U">Evolution of space open electric arc burning in the external axial magnetic field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Urusova, I. R.; Urusova, T. E. 2018-06-01 The calculation was made for open DC electric arc burning in an external uniform axial magnetic field. It was performed within the framework of a nonstationary three-dimensional mathematical model in approximation of partial local thermodynamic equilibrium of plasma. A "schematic" analog of electron temperature fluctuations was proposed for numerical realization of the open electric arc column of a helical shape. According to calculations, it was established that the column of the open electric arc takes a helical space shape. Plasma rotates around a longitudinal axis of the arc, at that the directions of plasma rotation near the cathode and the anode are opposite. In the arc cross-sections, the velocity of plasma rotation is unequal and the deviation value of the same part of the arc from the central axis varies in time. A helical shape of the open arc is not stable and varies in time. Apparently, the open arc cannot remain stable and invariable in the time helical shape in the external axial magnetic field. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PFR.....2S1012S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PFR.....2S1012S">Multi-Wavelength Imaging of Solar Plasma - High-Beta Disruption Model of Solar Flares -</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shibasaki, Kiyoto Solar atmosphere is filled with plasma and magnetic field. Activities in the atmosphere are due to plasma instabilities in the magnetic field. To understand the physical mechanisms of activities / instabilities, it is necessary to know the physical conditions of magnetized plasma, such as temperature, density, magnetic field, and their spatial structures and temporal developments. Multi-wavelength imaging is essential for this purpose. Imaging observations of the Sun at microwave, X-ray, EUV and optical ranges are routinely going on. Due to free exchange of original data among solar physics and related field communities, we can easily combine images covering wide range of spectrum. Even under such circumstances, we still do not understand the cause of activities in the solar atmosphere well. The current standard model of solar activities is based on magnetic reconnection: release of stored magnetic energy by reconnection is the cause of solar activities on the Sun such as solar flares. However, recent X-ray, EUV and microwave observations with high spatial and temporal resolution show that dense plasma is involved in activities from the beginning. Based on these observations, I propose a high-beta model of solar activities, which is very similar to high-beta disruptions in magnetically confined fusion experiments. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19970019636','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19970019636">The Solar-B Mission</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Antiochos, Spiro; Acton, Loren; Canfield, Richard; Davila, Joseph; Davis, John; Dere, Kenneth; Doschek, George; Golub, Leon; Harvey, John; Hathaway, David; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_19970019636'); toggleEditAbsImage('author_19970019636_show'); toggleEditAbsImage('author_19970019636_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_19970019636_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_19970019636_hide"> 1997-01-01 Solar-B, the next ISAS mission (with major NASA participation), is designed to address the fundamental question of how magnetic fields interact with plasma to produce solar variability. The mission has a number of unique capabilities that will enable it to answer the outstanding questions of solar magnetism. First, by escaping atmospheric seeing, it will deliver continuous observations of the solar surface with unprecedented spatial resolution. Second, Solar-B will deliver the first accurate measurements of all three components of the photospheric magnetic field. Solar-B will measure both the magnetic energy driving the photosphere and simultaneously its effects in the corona. Solar-B offers unique programmatic opportunities to NASA. It will continue an effective collaboration with our most reliable international partner. It will deliver images and data that will have strong public outreach potential. Finally, the science of Solar-B is clearly related to the themes of origins and plasma astrophysics, and contributes directly to the national space weather and global change programs. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004APS..SES.DC006H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004APS..SES.DC006H">Open Path and Solar Sourced Atmospheric Spectra are Analyzed Yielding Concentration Profiles and Temporal Variation Results</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hager, John; Steill, Jeff; Compton, Robert 2004-11-01 A high-resolution FTIR Bomem DA8 spectrometer has been installed at the University of Tennessee and has been successfully coupled with a suntracker and open path optics. Solar absorption spectra were recorded on 75 days in the last 18 months over a large spectral range. The high-resolution spectra provide information on the vertical concentration profiles of trace gases in the atmosphere. The HITRAN data base was used along with SFIT2 in order to retrieve concentration profiles of different trace gases. Many atmospheric constituents are open to this analysis. Tropospheric Ozone in the Knoxville area is rated as the worst in the nation by the American Lung Association. Sunlight, pollutants and hot weather cause ground-level ozone to form in harmful concentrations in the air. Seasonal and daily trends of ozone show correlation with other sources such as the EPA, and recent efforts to correlate solar spectra with open-path spectra will be discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6176280-solar-coronal-magnetic-field-topology-inferred-from-high-resolution-optical-ray-movies','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6176280-solar-coronal-magnetic-field-topology-inferred-from-high-resolution-optical-ray-movies">Solar coronal magnetic field topology inferred from high resolution optical and x-ray movies</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Tarbell, T.; Frank, Z.; Hurlburt, N. 1993-01-01 The authors are using high resolution digital movies of solar active regions in optical and X-ray wavelengths to study solar flares and other transients. The optical movies were collected at the Swedish Solar Observatory on La Palma using the Lockheed tunable filtergraph system, in May-July, 1992. They include longitudinal and transverse magnetograms, H-alpha Doppler and intensity images at many wavelengths, Ca K, Na D, and white light images. Simultaneous X-ray images from Yohkoh are available much of the time. Several ways to establish the connectivity of some coronal magnetic field lines are being explored. Some of the clues available are:more » magnetic footpoint polarities and transverse field direction; H-alpha fibrils and loops seen in several wavelengths; proper motion and Dopper shifts of blobs moving along field lines; footprint brightening in micro-flares; spreading of flare ribbons during gradual phases of flares; X-ray morphology and correlations with H-alpha; and draining of flare loops. Examples of each of these will be shown on video.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18046399','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18046399">Little or no solar wind enters Venus' atmosphere at solar minimum.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhang, T L; Delva, M; Baumjohann, W; Auster, H-U; Carr, C; Russell, C T; Barabash, S; Balikhin, M; Kudela, K; Berghofer, G; Biernat, H K; Lammer, H; Lichtenegger, H; Magnes, W; Nakamura, R; Schwingenschuh, K; Volwerk, M; Vörös, Z; Zambelli, W; Fornacon, K-H; Glassmeier, K-H; Richter, I; Balogh, A; Schwarzl, H; Pope, S A; Shi, J K; Wang, C; Motschmann, U; Lebreton, J-P 2007-11-29 Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...853L..26H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...853L..26H">A Magnetic Reconnection Event in the Solar Atmosphere Driven by Relaxation of a Twisted Arch Filament System</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Huang, Zhenghua; Mou, Chaozhou; Fu, Hui; Deng, Linhua; Li, Bo; Xia, Lidong 2018-02-01 We present high-resolution observations of a magnetic reconnection event in the solar atmosphere taken with the New Vacuum Solar Telescope, Atmospheric Imaging Assembly (AIA), and Helioseismic and Magnetic Imager (HMI). The reconnection event occurred between the threads of a twisted arch filament system (AFS) and coronal loops. Our observations reveal that the relaxation of the twisted AFS drives some of its threads to encounter the coronal loops, providing inflows of the reconnection. The reconnection is evidenced by flared X-shape features in the AIA images, a current-sheet-like feature apparently connecting post-reconnection loops in the Hα + 1 Å images, small-scale magnetic cancelation in the HMI magnetograms and flows with speeds of 40–80 km s‑1 along the coronal loops. The post-reconnection coronal loops seen in the AIA 94 Å passband appear to remain bright for a relatively long time, suggesting that they have been heated and/or filled up by dense plasmas previously stored in the AFS threads. Our observations suggest that the twisted magnetic system could release its free magnetic energy into the upper solar atmosphere through reconnection processes. While the plasma pressure in the reconnecting flux tubes are significantly different, the reconfiguration of field lines could result in transferring of mass among them and induce heating therein. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22364617-solar-flare-prediction-using-sdo-hmi-vector-magnetic-field-data-machine-learning-algorithm','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22364617-solar-flare-prediction-using-sdo-hmi-vector-magnetic-field-data-machine-learning-algorithm">SOLAR FLARE PREDICTION USING SDO/HMI VECTOR MAGNETIC FIELD DATA WITH A MACHINE-LEARNING ALGORITHM</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Bobra, M. G.; Couvidat, S., E-mail: couvidat@stanford.edu 2015-01-10 We attempt to forecast M- and X-class solar flares using a machine-learning algorithm, called support vector machine (SVM), and four years of data from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager, the first instrument to continuously map the full-disk photospheric vector magnetic field from space. Most flare forecasting efforts described in the literature use either line-of-sight magnetograms or a relatively small number of ground-based vector magnetograms. This is the first time a large data set of vector magnetograms has been used to forecast solar flares. We build a catalog of flaring and non-flaring active regions sampled from a databasemore » of 2071 active regions, comprised of 1.5 million active region patches of vector magnetic field data, and characterize each active region by 25 parameters. We then train and test the machine-learning algorithm and we estimate its performances using forecast verification metrics with an emphasis on the true skill statistic (TSS). We obtain relatively high TSS scores and overall predictive abilities. We surmise that this is partly due to fine-tuning the SVM for this purpose and also to an advantageous set of features that can only be calculated from vector magnetic field data. We also apply a feature selection algorithm to determine which of our 25 features are useful for discriminating between flaring and non-flaring active regions and conclude that only a handful are needed for good predictive abilities.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800014287','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800014287">Study program to improve the open-circuit voltage of low resistivity single crystal silicon solar cells</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Minnucci, J. A.; Matthei, K. W. 1980-01-01 The results of a 14 month program to improve the open circuit voltage of low resistivity silicon solar cells are described. The approach was based on ion implantation in 0.1- to 10.0-ohm-cm float-zone silicon. As a result of the contract effort, open circuit voltages as high as 645 mV (AMO 25 C) were attained by high dose phosphorus implantation followed by furnace annealing and simultaneous SiO2 growth. One key element was to investigate the effects of bandgap narrowing caused by high doping concentrations in the junction layer. Considerable effort was applied to optimization of implant parameters, selection of furnace annealing techniques, and utilization of pulsed electron beam annealing to minimize thermal process-induced defects in the completed solar cells. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820039098&hterms=magnetic+vector+potential&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmagnetic%2Bvector%2Bpotential','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820039098&hterms=magnetic+vector+potential&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dmagnetic%2Bvector%2Bpotential">Determination of magnetic helicity in the solar wind and implications for cosmic ray propagation</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Matthaeus, W. M.; Goldstein, M. L. 1981-01-01 Magnetic helicity (Hm) is the mean value of the correlation between a turbulent magnetic field and the magnetic vector potential. A technique is described for determining Hm and its 'reduced' spectrum from the two point magnetic correlation matrix. The application of the derived formalism to solar wind magnetic fluctuations is discussed, taking into account cases for which only single point measurements are available. The application procedure employs the usual 'frozen in approximation' approach. The considered method is applied to an analysis of several periods of Voyager 2 interplanetary magnetometer data near 2.8 AU. During these periods the correlation length, or energy containing length, was found to be approximately 3 x 10 to the 11th cm </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AJ....153..171X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AJ....153..171X">Temporal Variation of the Rotation of the Solar Mean Magnetic Field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xie, J. L.; Shi, X. J.; Xu, J. C. 2017-04-01 Based on continuous wavelet transformation analysis, the daily solar mean magnetic field (SMMF) from 1975 May 16 to 2014 July 31 is analyzed to reveal its rotational behavior. Both the recurrent plot in Bartels form and the continuous wavelet transformation analysis show the existence of rotational modulation in the variation of the daily SMMF. The dependence of the rotational cycle lengths on solar cycle phase is also studied, which indicates that the yearly mean rotational cycle lengths generally seem to be longer during the rising phase of solar cycles and shorter during the declining phase. The mean rotational cycle length for the rising phase of all of the solar cycles in the considered time is 28.28 ± 0.67 days, while for the declining phase it is 27.32 ± 0.64 days. The difference of the mean rotational cycle lengths between the rising phase and the declining phase is 0.96 days. The periodicity analysis, through the use of an auto-correlation function, indicates that the rotational cycle lengths have a significant period of about 10.1 years. Furthermore, the cross-correlation analysis indicates that there exists a phase difference between the rotational cycle lengths and solar activity. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850046194&hterms=magnetic+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmagnetic%2Bcooling','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850046194&hterms=magnetic+cooling&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dmagnetic%2Bcooling">On the heating mechanism of magnetic flux loops in the solar atmosphere</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Song, M. T.; Wu, S. T. 1984-01-01 An investigation is conducted of physical heating mechanisms due to the ponderomotive forces exerted by turbulent waves along the solar atmosphere's curved magnetic flux loops. Results indicate that the temperature difference between the inside and outside of the flux loop can be classified into three parts, two of which represent the cooling or heating effect exerted by the ponderomotive force, while the third is the heating effect due to turbulent energy conversion from the localized plasma. This heating mechanism is used to illustrate solar atmospheric heating by means of an example that leads to the formulation of plages. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvB..89t5313S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvB..89t5313S">Derivation of the open-circuit voltage of organic solar cells</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Staple, Douglas B.; Oliver, Patricia A. K.; Hill, Ian G. 2014-05-01 Organic photovoltaic cells have improved in efficiency from 1% two decades ago to over 10% today. Continued improvement necessitates a theoretical understanding of the factors determining efficiency. Organic photovoltaic efficiency can be parameterized in terms of open-circuit voltage, short-circuit current, and fill factor. Here we present a theory that explains the dependencies of open-circuit voltage on semiconductor energy levels, light intensity, solar cell and light-source temperatures, charge-carrier recombination, and external fluorescence efficiency. The present theory also explains why recombination at the donor-acceptor heterointerface is a dominant process in heterojunction-based cells. Furthermore, the Carnot efficiency appears, highlighting the connection to basic thermodynamics. The theory presented here is consistent with and builds on the experimental and theoretical observations already in the literature. Crucially, the present theory can be straightforwardly derived in a line-by-line fashion using standard tools from statistical physics. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740046559&hterms=Krieger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DKrieger','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740046559&hterms=Krieger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DKrieger">A coronal hole and its identification as the source of a high velocity solar wind stream</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Krieger, A. S.; Timothy, A. F.; Roelof, E. C. 1973-01-01 X-ray images of the solar corona showed a magnetically open structure in the low corona which extended from N20W20 to the south pole. Analysis of the measured X-ray intensities shows the density scale heights within the structure to be typically a factor of two less than that in the surrounding large scale magnetically closed regions. The structure is identified as a coronal hole. Wind measurements for the appropriate period were traced back to the sun by the method of instantaneous ideal spirals. A striking agreement was found between the Carrington longitude of the solar source of a recurrent high velocity solar wind stream and the position of the hole. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...856..139W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...856..139W">Opening a Window on ICME-driven GCR Modulation in the Inner Solar System</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Winslow, Reka M.; Schwadron, Nathan A.; Lugaz, Noé; Guo, Jingnan; Joyce, Colin J.; Jordan, Andrew P.; Wilson, Jody K.; Spence, Harlan E.; Lawrence, David J.; Wimmer-Schweingruber, Robert F.; Mays, M. Leila 2018-04-01 Interplanetary coronal mass ejections (ICMEs) often cause Forbush decreases (Fds) in the flux of galactic cosmic rays (GCRs). We investigate how a single ICME, launched from the Sun on 2014 February 12, affected GCR fluxes at Mercury, Earth, and Mars. We use GCR observations from MESSENGER at Mercury, ACE/LRO at the Earth/Moon, and MSL at Mars. We find that Fds are steeper and deeper closer to the Sun, and that the magnitude of the magnetic field in the ICME magnetic ejecta as well as the “strength” of the ICME sheath both play a large role in modulating the depth of the Fd. Based on our results, we hypothesize that (1) the Fd size decreases exponentially with heliocentric distance, and (2) that two-step Fds are more common closer to the Sun. Both hypotheses will be directly verifiable by the upcoming Parker Solar Probe and Solar Orbiter missions. This investigation provides the first systematic study of the changes in GCR modulation as a function of distance from the Sun using nearly contemporaneous observations at Mercury, Earth/Moon, and Mars, which will be critical for validating our physical understanding of the modulation process throughout the heliosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhPl...25d2903N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhPl...25d2903N">Magnetic reconnection in the low solar chromosphere with a more realistic radiative cooling model</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ni, Lei; Lukin, Vyacheslav S.; Murphy, Nicholas A.; Lin, Jun 2018-04-01 Magnetic reconnection is the most likely mechanism responsible for the high temperature events that are observed in strongly magnetized locations around the temperature minimum in the low solar chromosphere. This work improves upon our previous work [Ni et al., Astrophys. J. 852, 95 (2018)] by using a more realistic radiative cooling model computed from the OPACITY project and the CHIANTI database. We find that the rate of ionization of the neutral component of the plasma is still faster than recombination within the current sheet region. For low β plasmas, the ionized and neutral fluid flows are well-coupled throughout the reconnection region resembling the single-fluid Sweet-Parker model dynamics. Decoupling of the ion and neutral inflows appears in the higher β case with β0=1.46 , which leads to a reconnection rate about three times faster than the rate predicted by the Sweet-Parker model. In all cases, the plasma temperature increases with time inside the current sheet, and the maximum value is above 2 ×104 K when the reconnection magnetic field strength is greater than 500 G. While the more realistic radiative cooling model does not result in qualitative changes of the characteristics of magnetic reconnection, it is necessary for studying the variations of the plasma temperature and ionization fraction inside current sheets in strongly magnetized regions of the low solar atmosphere. It is also important for studying energy conversion during the magnetic reconnection process when the hydrogen-dominated plasma approaches full ionization. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040047164&hterms=topology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtopology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040047164&hterms=topology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtopology">Coronal Magnetic Field Topology and Source of Fast Solar Wind</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Guhathakurta, M.; Sittler, E.; Fisher, R.; McComas, D.; Thompson, B. 1999-01-01 We have developed a steady state, 2D semi-empirical MHD model of the solar corona and the solar wind with many surprising results. This model for the first time shows, that the boundary between the fast and the slow solar wind as observed by Ulysses beyond 1 AU, is established in the low corona. The fastest wind observed by Ulysses (680-780 km/s) originates from the polar coronal holes at 70 -90 deg. latitude at the Sun. Rapidly diverging magnetic field geometry accounts for the fast wind reaching down to a latitude of +/- 30 deg. at the orbit of Earth. The gradual increase in the fast wind observed by Ulysses, with latitude, can be explained by an increasing field strength towards the poles, which causes Alfven wave energy flux to increase towards the poles. Empirically, there is a direct relationship between this gradual increase in wind speed and the expansion factor, f, computed at r greater than 20%. This relationship is inverse if f is computed very close to the Sun. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...856...86M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...856...86M">Evolution of Magnetic Rayleigh–Taylor Instability into the Outer Solar Corona and Low Interplanetary Space</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mishra, Sudheer K.; Singh, Talwinder; Kayshap, P.; Srivastava, A. K. 2018-03-01 We analyze the observations from Solar TErrestrial RElations Observatory (STEREO)-A and B/COR-1 of an eruptive prominence in the intermediate corona on 2011 June 7 at 08:45 UT, which consists of magnetic Rayleigh–Taylor (MRT) unstable plasma segments. Its upper-northward segment shows spatio-temporal evolution of MRT instability in form of finger structures up to the outer corona and low interplanetary space. Using the method of Dolei et al., It is estimated that the density in each bright finger is greater than the corresponding dark region lying below it in the surrounding intermediate corona. The instability is evolved due to wave perturbations that are parallel to the magnetic field at the density interface. We conjecture that the prominence plasma is supported by tension component of the magnetic field against gravity. Through the use of linear stability theory, the magnetic field is estimated as 21–40 mG to suppress growth of MRT instability in the observed finger structures. In the southward plasma segment, a horn-like structure is observed at 11:55 UT in the intermediate corona that also indicates MRT instability. Falling blobs are also observed in both of the plasma segments. In the outer corona, up to 6–13 solar radii, the mushroom-like plasma structures have been identified in the upper-northward MRT unstable plasma segment using STEREO-A/COR-2. These structures most likely grew due to the breaking and twisting of fingers at large spatial scales in weaker magnetic fields. In the lower interplanetary space up to 20 solar radii, these structures are fragmented into various small-scale localized plasma spikes, most likely due to turbulent mixing. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22020517-dynamics-solar-magnetic-field-polarity-reversals-butterfly-diagram-quasi-biennial-oscillations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22020517-dynamics-solar-magnetic-field-polarity-reversals-butterfly-diagram-quasi-biennial-oscillations">THE DYNAMICS OF THE SOLAR MAGNETIC FIELD: POLARITY REVERSALS, BUTTERFLY DIAGRAM, AND QUASI-BIENNIAL OSCILLATIONS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Vecchio, A.; Meduri, D.; Carbone, V. 2012-04-10 The spatio-temporal dynamics of the solar magnetic field has been investigated by using NSO/Kitt Peak magnetic synoptic maps covering the period 1976 August-2003 September. The field radial component, for each heliographic latitude, has been decomposed in intrinsic mode functions through the Empirical Mode Decomposition in order to investigate the time evolution of the various characteristic oscillating modes at different latitudes. The same technique has also been applied on synoptic maps of the meridional and east-west components, which were derived from the observed line-of-sight projection of the field by using the differential rotation. Results obtained for the {approx}22 yr cycle, relatedmore » to the polarity inversions of the large-scale dipolar field, show an antisymmetric behavior with respect to the equator in all the field components and a marked poleward flux migration in the radial and meridional components (from about -35 Degree-Sign and +35 Degree-Sign in the southern and northern hemispheres, respectively). The quasi-biennial oscillations (QBOs) are also identified as a fundamental timescale of variability of the magnetic field and associated with poleward magnetic flux migration from low latitudes around the maximum and descending phase of the solar cycle. Moreover, signs of an equatorward drift, at a {approx}2 yr rate, seem to appear in the radial and toroidal components. Hence, the QBO patterns suggest a link to a dynamo action. Finally, the high-frequency component of the magnetic field, at timescales less than 1 yr, provides the most energetic contribution and it is associated with the outbreaks of the bipolar regions on the solar surface.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780030814&hterms=bright+hour&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dbright%2Bhour','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780030814&hterms=bright+hour&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dbright%2Bhour">Bright X-ray arcs and the emergence of solar magnetic flux</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Chapman, G. A.; Broussard, R. M. 1977-01-01 The Skylab S-056 and S-082A experiments and ground-based magnetograms have been used to study the role of bright X-ray arcs and the emergence of solar magnetic flux in the McMath region 12476. The S-056 X-ray images show a system of one or sometimes two bright arcs within a diffuse emitting region. The arcs seem to directly connect regions of opposite magnetic polarity in the photosphere. Magnetograms suggest the possible emergence of a magnetic flux. The width of the main arc is approximately 6 arcsec when most clearly defined, and the length is approximately 30-50 arcsec. Although the arc system is observed to vary in brightness over a period exceeding 24 hours, it remains fixed in orientation. The temperature of the main arc is approximately 3 x 10 to the 6th K. It is suggested that merging magnetic fields may provide the primary energy source, perhaps accompanied by resistive heating from a force-free current. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMSA51A2381A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMSA51A2381A">NmF2 Morphology during four-classes of solar and magnetic activity conditions at an African station around the EIA trough and comparison with IRI-2016 Map</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Adebesin, B.; Rabiu, B.; Obrou, O. K. 2017-12-01 Better understanding of the electrodynamics between parameters used in describing the ionospheric layer and their solar and geomagnetic influences goes a long way in furthering the expansion of space weather knowledge. Telecommunication and scientific radar launch activities can however be interrupted either on a larger/smaller scales by geomagnetic activities which is susceptible to changes in solar activity and effects. Consequently, the ionospheric NmF2 electrodynamics was investigated for a station near the magnetic dip in the African sector (Korhogo, Geomagnetic: -1.26°N, 67.38°E). Data covering years 1996 and 2000 were investigated for four categories of magnetic and solar activities viz (i) F10.7 < 85 sfu, ap ≤ 7 nT (low solar quiet, LSQ); (ii) F10.7 < 85 sfu, ap > 7 nT (low solar disturbed, LSD); (iii) F10.7 > 150 sfu, ap ≤ 7 nT (high solar quiet, HSQ); and (iv) F10.7 > 150 sfu, ap > 7 nT (high solar disturbed, HSD). NmF2 revealed a pre-noon peak higher than the post-noon peak during high solar activity irrespective of magnetic activity condition and overturned during low solar activity. Higher NmF2 peak amplitude however characterise disturbed magnetic activity than quiet magnetic condition for any solar activity. The maximum pre-/post-noon peaks appeared in equinox season. June solstice noon-time bite out lagged other seasons by 1-2 h. Daytime variability increases with increasing magnetic activity. Equinox/June solstice recorded the highest pre-sunrise/post-sunset peak variability magnitudes with the lowest emerging in June solstice/equinox for all solar and magnetic conditions. The nighttime annual variability amplitude is higher during disturbed than quiet condition regardless of solar activity period; while the range is similar for daytime observations. The noon-time trough characteristics is not significant in the IRI NmF2 pattern during high solar activity but evident during low solar conditions. IRI-2016 map performed best during disturbed </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26062509','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26062509">Small-scale dynamo magnetism as the driver for heating the solar atmosphere.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Amari, Tahar; Luciani, Jean-François; Aly, Jean-Jacques 2015-06-11 The long-standing problem of how the solar atmosphere is heated has been addressed by many theoretical studies, which have stressed the relevance of two specific mechanisms, involving magnetic reconnection and waves, as well as the necessity of treating the chromosphere and corona together. But a fully consistent model has not yet been constructed and debate continues, in particular about the possibility of coronal plasma being heated by energetic phenomena observed in the chromosphere. Here we report modelling of the heating of the quiet Sun, in which magnetic fields are generated by a subphotospheric fluid dynamo intrinsically connected to granulation. We find that the fields expand into the chromosphere, where plasma is heated at the rate required to match observations (4,500 watts per square metre) by small-scale eruptions that release magnetic energy and drive sonic motions. Some energetic eruptions can even reach heights of 10 million metres above the surface of the Sun, thereby affecting the very low corona. Extending the model by also taking into account the vertical weak network magnetic field allows for the existence of a mechanism able to heat the corona above, while leaving unchanged the physics of chromospheric eruptions. Such a mechanism rests on the eventual dissipation of Alfvén waves generated inside the chromosphere and that carry upwards the required energy flux of 300 watts per square metre. The model shows a topologically complex magnetic field of 160 gauss on the Sun's surface, agreeing with inferences obtained from spectropolarimetric observations, chromospheric features (contributing only weakly to the coronal heating) that can be identified with observed spicules and blinkers, and vortices that may be possibly associated with observed solar tornadoes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170009484','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170009484">Flux Cancelation: The Key to Solar Eruptions</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald; Chakrapani, Prithi; Innes, Davina; Schmit, Don; Tiwari, Sanjiv 2017-01-01 Solar coronal jets are magnetically channeled eruptions that occur in all types of solar environments (e.g. active regions, quiet-Sun regions and coronal holes). Recent studies show that coronal jets are driven by the eruption of small-scare filaments (minifilaments). Once the eruption is underway magnetic reconnection evidently makes the jet spire and the bright emission in the jet base. However, the triggering mechanism of these eruptions and the formation mechanism of the pre-jet minifilaments are still open questions. In this talk, mainly using SDOAIA and SDOHIM data, first I will address the question: what triggers the jet-driving minifilament eruptions in different solar environments (coronal holes, quiet regions, active regions)? Then I will talk about the magnetic field evolution that produces the pre-jet minifilaments. By examining pre-jet evolutionary changes in line-of-sight HMI magnetograms while examining concurrent EUV images of coronal and transition-region emission, we find clear evidence that flux cancelation is the main process that builds pre-jet minifilaments, and is also the main process that triggers the eruptions. I will also present results from our ongoing work indicating that jet-driving minifilament eruptions are analogous to larger-scare filament eruptions that make flares and CMEs. We find that persistent flux cancellation at the neutral line of large-scale filaments often triggers their eruptions. From our observations we infer that flux cancelation is the fundamental process from the buildup and triggering of solar eruptions of all sizes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170010226','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170010226">Flux Cancelation: The Key to Solar Eruptions</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald; Chakrapani, Prithi; Innes, Davina; Schmit, Don; Tiwari, Sanjiv 2017-01-01 Solar coronal jets are magnetically channeled eruptions that occur in all types of solar environments (e.g. active regions, quiet-Sun regions and coronal holes). Recent studies show that coronal jets are driven by the eruption of small-scale filaments (minifilaments). Once the eruption is underway magnetic reconnection evidently makes the jet spire and the bright emission in the jet base. However, the triggering mechanism of these eruptions and the formation mechanism of the pre-jet minifilaments are still open questions. In this talk, mainly using SDO/AIA and SDO/HMI data, first I will address the question: what triggers the jet-driving minifilament eruptions in different solar environments (coronal holes, quiet regions, active regions)? Then I will talk about the magnetic field evolution that produces the pre-jet minifilaments. By examining pre-jet evolutionary changes in line-of-sight HMI magnetograms while examining concurrent EUV images of coronal and transition-region emission, we find clear evidence that flux cancellation is the main process that builds pre-jet minifilaments, and is also the main process that triggers the eruptions. I will also present results from our ongoing work indicating that jet-driving minifilament eruptions are analogous to larger-scale filament eruptions that make flares and CMEs. We find that persistent flux cancellation at the neutral line of large-scale filaments often triggers their eruptions. From our observations we infer that flux cancellation is the fundamental process for the buildup and triggering of solar eruptions of all sizes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSH51B2227S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSH51B2227S">Nature of Kinetic Scale Fluctuations in Solar Wind Turbulence</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Salem, C. S.; Chen, C. H.; Sundkvist, D. J.; Chaston, C. C.; Bale, S. D.; Mozer, F. 2012-12-01 We present an investigation of the nature of small-scale turbulent fluctuations in the solar wind. The nature of the dissipation range fluctuations of solar wind turbulence remains a major open question in heliospheric physics. The steepening of the observed (magnetic field) spectra at ion scales was originally attributed to ion cyclotron damping, but it was later suggested that it could well be due to the dispersive nature of fluctuations at these scales. The nature of the dispersive cascade at and below the ion scales is still debated, two leading hypothesis being that these fluctuations have characteristics of Kinetic Alfven Waves (KAW) or whistler waves. Other possible contributions from current sheets and/or kinetic instabilities have been suggested. There is mounting evidence that the fluctuations at these scales are KAW-like. In this study, we analyze several carefully selected unperturbed solar wind intervals, using magnetic field, electric field as well as density measurements from the Cluster spacecraft in order to identify the nature of the wave modes present, how frequent they are and try to determine whether one or more wave modes at different times. We examine the electric to magnetic field fluctuation ratio (δ E/δd B), the magnetic compressibility (δ B∥ /δ B) as well as density fluctuations using newly developed diagnostic techniques by Salem et al (2012) and Chen et al (2012). We look for variations of the nature and properties of these kinetic scale fluctuations with solar wind conditions, such as the plasma beta and the angle between the magnetic field and the flow velocity which controls the measured (spacecraft frame) frequency of the fluctuations. We discuss how these results would impact how the solar wind plasma is heated. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...853..197D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...853..197D">Response of Solar Irradiance to Sunspot-area Variations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dudok de Wit, T.; Kopp, G.; Shapiro, A.; Witzke, V.; Kretzschmar, M. 2018-02-01 One of the important open questions in solar irradiance studies is whether long-term variability (i.e., on timescales of years and beyond) can be reconstructed by means of models that describe short-term variability (i.e., days) using solar proxies as inputs. Preminger & Walton showed that the relationship between spectral solar irradiance and proxies of magnetic-flux emergence, such as the daily sunspot area, can be described in the framework of linear system theory by means of the impulse response. We significantly refine that empirical model by removing spurious solar-rotational effects and by including an additional term that captures long-term variations. Our results show that long-term variability cannot be reconstructed from the short-term response of the spectral irradiance, which questions the extension of solar proxy models to these timescales. In addition, we find that the solar response is nonlinear in a way that cannot be corrected simply by applying a rescaling to a sunspot area. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22356751-magnetar-giant-flares-multipolar-magnetic-fields-fully-partially-open-eruptions-flux-ropes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22356751-magnetar-giant-flares-multipolar-magnetic-fields-fully-partially-open-eruptions-flux-ropes">Magnetar giant flares in multipolar magnetic fields. I. Fully and partially open eruptions of flux ropes</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Huang, Lei; Yu, Cong, E-mail: muduri@shao.ac.cn, E-mail: cyu@ynao.ac.cn 2014-04-01 We propose a catastrophic eruption model for the enormous energy release of magnetars during giant flares, in which a toroidal and helically twisted flux rope is embedded within a force-free magnetosphere. The flux rope stays in stable equilibrium states initially and evolves quasi-statically. Upon the loss of equilibrium, the flux rope cannot sustain the stable equilibrium states and erupts catastrophically. During the process, the magnetic energy stored in the magnetosphere is rapidly released as the result of destabilization of global magnetic topology. The magnetospheric energy that could be accumulated is of vital importance for the outbursts of magnetars. We carefullymore » establish the fully open fields and partially open fields for various boundary conditions at the magnetar surface and study the relevant energy thresholds. By investigating the magnetic energy accumulated at the critical catastrophic point, we find that it is possible to drive fully open eruptions for dipole-dominated background fields. Nevertheless, it is hard to generate fully open magnetic eruptions for multipolar background fields. Given the observational importance of the multipolar magnetic fields in the vicinity of the magnetar surface, it would be worthwhile to explore the possibility of the alternative eruption approach in multipolar background fields. Fortunately, we find that flux ropes may give rise to partially open eruptions in the multipolar fields, which involve only partial opening of background fields. The energy release fractions are greater for cases with central-arcaded multipoles than those with central-caved multipoles that emerged in background fields. Eruptions would fail only when the centrally caved multipoles become extremely strong.« less </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...566A..46O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...566A..46O">The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He i 10 830 Å triplet</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Orozco Suárez, D.; Asensio Ramos, A.; Trujillo Bueno, J. 2014-06-01 Context. Determining the magnetic field vector in quiescent solar prominences is possible by interpreting the Hanle and Zeeman effects in spectral lines. However, observational measurements are scarce and lack high spatial resolution. Aims: We determine the magnetic field vector configuration along a quiescent solar prominence by interpreting spectropolarimetric measurements in the He i 1083.0 nm triplet obtained with the Tenerife Infrared Polarimeter installed at the German Vacuum Tower Telescope of the Observatorio del Teide. Methods: The He i 1083.0 nm triplet Stokes profiles were analyzed with an inversion code that takes the physics responsible for the polarization signals in this triplet into account. The results are put into a solar context with the help of extreme ultraviolet observations taken with the Solar Dynamic Observatory and the Solar Terrestrial Relations Observatory satellites. Results: For the most probable magnetic field vector configuration, the analysis depicts a mean field strength of 7 gauss. We do not find local variations in the field strength except that the field is, on average, lower in the prominence body than in the prominence feet, where the field strength reaches ~25 gauss. The averaged magnetic field inclination with respect to the local vertical is ~77°. The acute angle of the magnetic field vector with the prominence main axis is 24° for the sinistral chirality case and 58° for the dextral chirality. These inferences are in rough agreement with previous results obtained from the analysis of data acquired with lower spatial resolutions. A movie is available in electronic form at http://www.aanda.org </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22679850-direct-effect-toroidal-magnetic-fields-stellar-oscillations-analytical-expression-general-matrix-element','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22679850-direct-effect-toroidal-magnetic-fields-stellar-oscillations-analytical-expression-general-matrix-element">The Direct Effect of Toroidal Magnetic Fields on Stellar Oscillations: An Analytical Expression for the General Matrix Element</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kiefer, René; Schad, Ariane; Roth, Markus 2017-09-10 Where is the solar dynamo located and what is its modus operandi? These are still open questions in solar physics. Helio- and asteroseismology can help answer them by enabling us to study solar and stellar internal structures through global oscillations. The properties of solar and stellar acoustic modes are changing with the level of magnetic activity. However, until now, the inference on subsurface magnetic fields with seismic measures has been very limited. The aim of this paper is to develop a formalism to calculate the effect of large-scale toroidal magnetic fields on solar and stellar global oscillation eigenfunctions and eigenfrequencies.more » If the Lorentz force is added to the equilibrium equation of motion, stellar eigenmodes can couple. In quasi-degenerate perturbation theory, this coupling, also known as the direct effect, can be quantified by the general matrix element. We present the analytical expression of the matrix element for a superposition of subsurface zonal toroidal magnetic field configurations. The matrix element is important for forward calculations of perturbed solar and stellar eigenfunctions and frequency perturbations. The results presented here will help to ascertain solar and stellar large-scale subsurface magnetic fields, and their geometric configuration, strength, and change over the course of activity cycles.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...846..162K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...846..162K">The Direct Effect of Toroidal Magnetic Fields on Stellar Oscillations: An Analytical Expression for the General Matrix Element</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kiefer, René; Schad, Ariane; Roth, Markus 2017-09-01 Where is the solar dynamo located and what is its modus operandi? These are still open questions in solar physics. Helio- and asteroseismology can help answer them by enabling us to study solar and stellar internal structures through global oscillations. The properties of solar and stellar acoustic modes are changing with the level of magnetic activity. However, until now, the inference on subsurface magnetic fields with seismic measures has been very limited. The aim of this paper is to develop a formalism to calculate the effect of large-scale toroidal magnetic fields on solar and stellar global oscillation eigenfunctions and eigenfrequencies. If the Lorentz force is added to the equilibrium equation of motion, stellar eigenmodes can couple. In quasi-degenerate perturbation theory, this coupling, also known as the direct effect, can be quantified by the general matrix element. We present the analytical expression of the matrix element for a superposition of subsurface zonal toroidal magnetic field configurations. The matrix element is important for forward calculations of perturbed solar and stellar eigenfunctions and frequency perturbations. The results presented here will help to ascertain solar and stellar large-scale subsurface magnetic fields, and their geometric configuration, strength, and change over the course of activity cycles. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29109441','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29109441">Buildup of a highly twisted magnetic flux rope during a solar eruption.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wang, Wensi; Liu, Rui; Wang, Yuming; Hu, Qiang; Shen, Chenglong; Jiang, Chaowei; Zhu, Chunming 2017-11-06 The magnetic flux rope is among the most fundamental magnetic configurations in plasma. Although its presence after solar eruptions has been verified by spacecraft measurements near Earth, its formation on the Sun remains elusive, yet is critical to understanding a broad spectrum of phenomena. Here we study the dynamic formation of a magnetic flux rope during a classic two-ribbon flare. Its feet are identified unambiguously with conjugate coronal dimmings completely enclosed by irregular bright rings, which originate and expand outward from the far ends of flare ribbons. The expansion is associated with the rapid ribbon separation during the flare main phase. Counting magnetic flux through the feet and the ribbon-swept area reveals that the rope's core is more twisted than its average of four turns. It propagates to the Earth as a typical magnetic cloud possessing a similar twist profile obtained by the Grad-Shafranov reconstruction of its three dimensional structure. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840062453&hterms=browning&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbrowning','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840062453&hterms=browning&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbrowning">The magnetic non-equilibrium of buoyant flux tubes in the solar corona</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Browning, P. K.; Priest, E. R. 1984-01-01 The magnetic field in the convection zone and photosphere of the sun exists mostly as concentrated tubes of magnetic flux. It is, therefore, necessary to study the basic properties of magnetic flux tubes to obtain a basis for understanding the behavior of the sun's magnetic field. The present investigation is concerned with the global equilibrium shape of a flux tube in the stratified solar atmosphere. A fundamental property of isolated flux tubes is magnetic buoyancy. Attention is given to flux tubes with external field, and twisted flux tubes. It is shown that the analysis of Parker (1975, 1979) and Spruit (1981) for calculating the equilibrium of a slender flux tube in a stratified atmosphere may be extended to more general situations. The slender tube approximation provides a method of solving the problem of modeling the overall curvature of flux tubes. It is found that for a twisted flux tube, there can be two possible equilibrium values of the height. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...8.1330W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...8.1330W">Buildup of a highly twisted magnetic flux rope during a solar eruption</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, Wensi; Liu, Rui; Wang, Yuming; Hu, Qiang; Shen, Chenglong; Jiang, Chaowei; Zhu, Chunming 2017-11-01 The magnetic flux rope is among the most fundamental magnetic configurations in plasma. Although its presence after solar eruptions has been verified by spacecraft measurements near Earth, its formation on the Sun remains elusive, yet is critical to understanding a broad spectrum of phenomena. Here we study the dynamic formation of a magnetic flux rope during a classic two-ribbon flare. Its feet are identified unambiguously with conjugate coronal dimmings completely enclosed by irregular bright rings, which originate and expand outward from the far ends of flare ribbons. The expansion is associated with the rapid ribbon separation during the flare main phase. Counting magnetic flux through the feet and the ribbon-swept area reveals that the rope's core is more twisted than its average of four turns. It propagates to the Earth as a typical magnetic cloud possessing a similar twist profile obtained by the Grad-Shafranov reconstruction of its three dimensional structure. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22519944-rotation-rate-differences-positive-negative-solar-magnetic-fields-between-latitudes','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22519944-rotation-rate-differences-positive-negative-solar-magnetic-fields-between-latitudes">ROTATION RATE DIFFERENCES OF POSITIVE AND NEGATIVE SOLAR MAGNETIC FIELDS BETWEEN ±60° LATITUDES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Shi, X. J.; Xie, J. L., E-mail: shixiangjun@ynao.ac.cn 2015-04-15 Based on a cross-correlation analysis of the Carrington synoptic maps of solar photospheric magnetic fields from Carrington Rotations Nos. 1625 to 2135 (from 1975 February to 2013 March), the sidereal rotation rates of the positive and negative magnetic fields in the latitude range of ±60° are obtained, and the rotation rate differences between them are investigated. The time–latitude distribution of the rate differences is shown, which looks like a butterfly diagram at the low and middle latitudes. For comparison, the time–latitude distribution of the longitudinally averaged photospheric magnetic fields is shown. We conclude that the magnetic fields having the samemore » polarity as the leading sunspots at a given hemisphere rotate faster than those exhibiting the opposite polarity at low and middle latitudes. However, at higher latitudes, the magnetic fields having the same polarity as the leading sunspots at a given hemisphere do not always rotate faster than those with the opposite polarity. Furthermore, the relationship between the rotation rate differences and solar magnetic fields is studied through a correlation analysis. Our result shows that the correlation coefficients between them reach maximum values at 13° (14°) latitude in the northern (southern) hemisphere, and change sign at 28° latitude in both hemispheres, then reach their minimum values at 58° (53°) latitude in the northern (southern) hemisphere.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982STIA...8327246G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982STIA...8327246G">Performance and operational analysis of a liquid desiccant open-flow solar collector</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Grodzka, P. G.; Rico, S. S. 1982-10-01 Theoretical predictions of the heat and mass transfer in an open flow solar collector used in conjunction with an absorption chiller are compared with performance data from a rooftop system. The study focuses on aqueous solutions of a hygroscopic salt, e.g., LiCl, flowing continuously over a solar absorbing surface. Water in the solution sublimes to a region of lower vapor pressure, i.e., the atmosphere. Direction of the water-depleted dessiccant to a storage volume and then to circulation around an evaporator unit permits operation of a solar-powered air conditioner. A closed form solution was defined for the heat and mass transfer, along with a finite difference solution. The system studied comprised a sloped roof top with 2500 sq ft of asphalt shingles, collector pipes beneath the shingles, and two 500 gal storage tanks. Relatively good agreement was found between the models and the recorded data, although some discrepancies were present when considering temperatures and performance at specific times of day. The measured 30-40% efficiencies indicated that further development of the system is warranted. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SSRv..214...61R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SSRv..214...61R">Abundances, Ionization States, Temperatures, and FIP in Solar Energetic Particles</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Reames, Donald V. 2018-04-01 The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding the physical processes that control populations of energetic particles. The early surprise in solar energetic particles (SEPs) was 1000-fold enhancements in {}3He/{}4He from resonant wave-particle interactions in the small "impulsive" SEP events that emit electron beams that produce type III radio bursts. Further studies found enhancements in Fe/O, then extreme enhancements in element abundances that increase with mass-to-charge ratio A/Q, rising by a factor of 1000 from He to Au or Pb arising in magnetic reconnection regions on open field lines in solar jets. In contrast, in the largest SEP events, the "gradual" events, acceleration occurs at shock waves driven out from the Sun by fast, wide coronal mass ejections (CMEs). Averaging many events provides a measure of solar coronal abundances, but A/Q-dependent scattering during transport causes variations with time; thus if Fe scatters less than O, Fe/O is enhanced early and depleted later. To complicate matters, shock waves often reaccelerate impulsive suprathermal ions left over or trapped above active regions that have spawned many impulsive events. Direct measurements of ionization states Q show coronal temperatures of 1-2 MK for most gradual events, but impulsive events often show stripping by matter traversal after acceleration. Direct measurements of Q are difficult and often unavailable. Since both impulsive and gradual SEP events have abundance enhancements that vary as powers of A/Q, we can use abundances to deduce the probable Q-values and the source plasma temperatures during acceleration, ≈3 MK for impulsive SEPs. This new technique also allows multiple spacecraft to measure temperature variations across the face of a shock wave, measurements otherwise unavailable and provides a new understanding of abundance variations in the element He. Comparing coronal abundances from SEPs </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22521418-magnetic-island-contraction-particle-acceleration-simulated-eruptive-solar-flares','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22521418-magnetic-island-contraction-particle-acceleration-simulated-eruptive-solar-flares">MAGNETIC-ISLAND CONTRACTION AND PARTICLE ACCELERATION IN SIMULATED ERUPTIVE SOLAR FLARES</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Guidoni, S. E.; DeVore, C. R.; Karpen, J. T. The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gainsmore » in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magnetohydrodynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002679&hterms=magnetic+particles&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmagnetic%2Bparticles','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002679&hterms=magnetic+particles&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmagnetic%2Bparticles">Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Guidoni, S. E.; Devore, C. R.; Karpen, J. T.; Lynch, B. J. 2016-01-01 The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSH53C..03C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSH53C..03C">Parametric Study of Preferential Ion Heating Due to Intermittent Magnetic Fields in the Solar Wind</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Carbajal Gomez, L.; Chapman, S. C.; Dendy, R. O.; Watkins, N. W. 2014-12-01 In situ observations and remote measurements of the solar wind show strong preferential heating of ions along the ambient magnetic field. Understanding the mechanism for this heating process is an open problem. The observed broad-band spectrum of Alfven waves permeating the fast solar wind provide a candidate mechanism for this preferential heating through wave-particle interactions on ion kinetic scales. Previous analytical and numerical studies have considered a single pump wave [1, 2] or a turbulent, broad-band spectra of Alfven waves [3, 4, 5] to drive the ion heating. The latter studies investigated the effects on ion heating due to different initial 1/fγpower spectral exponents and number of modes and the signals were random phase. However, the observed solar wind fluctuations are intermittent so that the phases of the modes comprising the power spectrum are not random. Non-Gaussian fluctuations are seen both on scales identified with the inertial range of Alfvenic turbulence [6], and on longer scales typified by '1/f' spectra [7]. We present results of the first parametric numerical simulations on the effects of different levels of intermittency of the broad-band spectra of Alfven waves on the preferential heating of ions in the solar wind. We performed hybrid simulations for the local heating of the solar wind, which resolves the full kinetic physics of the ions and treats the electrons as a charge-neutralizing fluid. Our simulations evolve the full vector velocities and electromagnetic fields in one configuration space coordinate and in time.We compare the efficiency of different levels of intermittency of the initial turbulent fields and their effect on the efficiency of the wave-particle interactions which are a mechanism for driving preferential ion heating in the solar wind. [1] J. A. Araneda, E. Marsh, A. F. Viñas, J. Geophys. Res. 112, A04104 (2007). [2] J. A. Araneda, E. Marsh, A. F. Viñas, Phys. Rev. Lett. 100, 125003 (2008) [3] Y. G. Maneva, A </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SFZ.....4a...3F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SFZ.....4a...3F">Radial distributions of magnetic field strength in the solar corona as derived from data on fast halo CMEs</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fainshtein, Victor; Egorov, Yaroslav 2018-03-01 In recent years, information about the distance between the body of rapid coronal mass ejection (CME) and the associated shock wave has been used to measure the magnetic field in the solar corona. In all cases, this technique allows us to find coronal magnetic field radial profiles B(R) applied to the directions almost perpendicular to the line of sight. We have determined radial distributions of magnetic field strength along the directions close to the Sun-Earth axis. For this purpose, using the "ice-cream cone" model and SOHO/LASCO data, we found 3D characteristics for fast halo coronal mass ejections (HCMEs) and for HCME-related shocks. With these data, we managed to obtain the B(R) distributions as far as ≈43 solar radii from the Sun's center, which is approximately twice as far as those in other studies based on LASCO data. We have concluded that to improve the accuracy of this method for finding the coronal magnetic field we should develop a technique for detecting CME sites moving in the slow and fast solar wind. We propose a technique for selecting CMEs whose central (paraxial) part actually moves in the slow wind. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhPl....5..792S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhPl....5..792S">Observations of two-dimensional magnetic field evolution in a plasma opening switch</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Shpitalnik, R.; Weingarten, A.; Gomberoff, K.; Krasik, Ya.; Maron, Y. 1998-03-01 The time dependent magnetic field distribution was studied in a coaxial 100-ns positive-polarity Plasma Opening Switch (POS) by observing the Zeeman effect in ionic line emission. Measurements local in three dimensions are obtained by doping the plasma using laser evaporation techniques. Fast magnetic field penetration with a relatively sharp magnetic field front (⩽1 cm) is observed at the early stages of the pulse (t≲25). Later in the pulse, the magnetic field is observed at the load-side edge of the plasma, leaving "islands" of low magnetic field at the plasma center that last for about 10 ns. The two-dimensional (2-D) structure of the magnetic field in the r,z plane is compared to the results of an analytical model based on electron-magneto-hydrodynamics, that utilizes the measured 2-D plasma density distribution and assumes fast magnetic field penetration along both POS electrodes. The model results provide quantitative explanation for the magnetic field evolution observed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19960021312&hterms=rust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Drust','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19960021312&hterms=rust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Drust">Escape of magnetic toroids from the Sun</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Bieber, John W.; Rust, David M. 1995-01-01 Analysis of heliospheric magnetic fields at 1 AU shows that 10(exp 24) Mx of net azimuthal flux escapes from the Sun per solar cycle. This rate is consistent with rates derived from other indicators of flux escape, including coronal mass ejections and filament eruptions. The toroidal flux escape rate is compared with the apparent rate of flux emergence at the solar surface, and it is concluded that escaping toroids will remove at least 20% of the emerging flux, and may remove as much as 100% of emerging flux if multiple eruptions occur on the toroids. The data imply that flux escapes the Sun with an efficiency far exceeding Parker's upper limit estimate of 3%. Toroidal flux escape is almost certainly the source of the observed overwinding of the interplanetary magnetic field spiral. Two mechanisms to facilitate net flux escape are discussed: helicity charging to push open the fields and flux transport with reconnection to close them off. We estimate the Sun will shed approximately 2 x 10(exp 45) of magnetic helicity per solar cycle, leading to a mean helicity density of 100 Mx(exp 2)cm(exp -3) at 1 AU, which agrees well with observations. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SoPh..292..164J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SoPh..292..164J">Statistical Properties of Photospheric Magnetic Elements Observed by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Javaherian, M.; Safari, H.; Dadashi, N.; Aschwanden, M. J. 2017-11-01 Magnetic elements of the solar surface are studied (using the 6173 Å Fe i line) in magnetograms recorded with the high-resolution Solar Dynamics Observatory (SDO)/ Helioseismic and Magnetic Imager (HMI). To extract some statistical and physical properties of these elements ( e.g. filling factors, magnetic flux, size, and lifetimes), we employed the region-based method called Yet Another Feature Tracking Algorithm ( YAFTA). An area of 400^''×400^'' was selected to investigate the magnetic characteristics in 2011. The correlation coefficient between filling factors of negative and positive polarities is 0.51. A broken power-law fit was applied to the frequency distribution of size and flux. Exponents of the power-law distributions for sizes smaller and greater than 16 arcsec2 were found to be -2.24 and -4.04, respectively. The exponents of power-law distributions for fluxes lower and greater than 2.63× 10^{19} Mx were found to be -2.11 and -2.51, respectively. The relationship between the size [S] and flux [F] of elements can be expressed by a power-law behavior of the form of S∝ F^{0.69}. The lifetime and its relationship with the flux and size of quiet-Sun (QS) elements during three days were studied. The code detected patches with lifetimes of about 15 hours, which we call long-duration events. We found that more than 95% of the magnetic elements have lifetimes shorter than 100 minutes. About 0.05% of the elements had lifetimes of more than six hours. The relationships between size [S], lifetime [T], and flux [F] for patches in the QS yield power-law relationships S∝ T^{0.25} and F∝ T^{0.38}, respectively. Executing a detrended-fluctuation analysis of the time series of new emerged magnetic elements, we found a Hurst exponent of 0.82, which implies a long-range temporal correlation in the system. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900001485','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900001485">The observation of possible reconnection events in the boundary changes of solar coronal holes</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Kahler, S. W.; Moses, J. Daniel 1989-01-01 Coronal holes are large scale regions of magnetically open fields which are easily observed in solar soft X-ray images. The boundaries of coronal holes are separatrices between large scale regions of open and closed magnetic fields where one might expect to observe evidence of solar magnetic reconnection. Previous studies by Nolte and colleagues using Skylab X-ray images established that large scale (greater than or equal to 9 x 10(4) km) changes in coronal hole boundaries were due to coronal processes, i.e., magnetic reconnection, rather than to photospheric motions. Those studies were limited to time scales of about one day, and no conclusion could be drawn about the size and time scales of the reconnection process at hole boundaries. Sequences of appropriate Skylab X-ray images were used with a time resolution of about 90 min during times of the central meridian passages of the coronal hole labelled Coronal Hole 1 to search for hole boundary changes which can yield the spatial and temporal scales of coronal magnetic reconnection. It was found that 29 of 32 observed boundary changes could be associated with bright points. The appearance of the bright point may be the signature of reconnection between small scale and large scale magnetic fields. The observed boundary changes contributed to the quasi-rigid rotation of Coronal Hole 1. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002434&hterms=getting+things+done&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgetting%2Bthings%2Bdone','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002434&hterms=getting+things+done&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgetting%2Bthings%2Bdone">The FIELDS Instrument Suite for Solar Probe Plus Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Choi, M. K.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20170002434'); toggleEditAbsImage('author_20170002434_show'); toggleEditAbsImage('author_20170002434_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20170002434_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20170002434_hide"> 2016-01-01 NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29755144','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29755144">The FIELDS Instrument Suite for Solar Probe Plus: Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bale, S D; Goetz, K; Harvey, P R; Turin, P; Bonnell, J W; de Wit, T Dudok; Ergun, R E; MacDowall, R J; Pulupa, M; Andre, M; Bolton, M; Bougeret, J-L; Bowen, T A; Burgess, D; Cattell, C A; Chandran, B D G; Chaston, C C; Chen, C H K; Choi, M K; Connerney, J E; Cranmer, S; Diaz-Aguado, M; Donakowski, W; Drake, J F; Farrell, W M; Fergeau, P; Fermin, J; Fischer, J; Fox, N; Glaser, D; Goldstein, M; Gordon, D; Hanson, E; Harris, S E; Hayes, L M; Hinze, J J; Hollweg, J V; Horbury, T S; Howard, R A; Hoxie, V; Jannet, G; Karlsson, M; Kasper, J C; Kellogg, P J; Kien, M; Klimchuk, J A; Krasnoselskikh, V V; Krucker, S; Lynch, J J; Maksimovic, M; Malaspina, D M; Marker, S; Martin, P; Martinez-Oliveros, J; McCauley, J; McComas, D J; McDonald, T; Meyer-Vernet, N; Moncuquet, M; Monson, S J; Mozer, F S; Murphy, S D; Odom, J; Oliverson, R; Olson, J; Parker, E N; Pankow, D; Phan, T; Quataert, E; Quinn, T; Ruplin, S W; Salem, C; Seitz, D; Sheppard, D A; Siy, A; Stevens, K; Summers, D; Szabo, A; Timofeeva, M; Vaivads, A; Velli, M; Yehle, A; Werthimer, D; Wygant, J R 2016-12-01 NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SSRv..204...49B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SSRv..204...49B">The FIELDS Instrument Suite for Solar Probe Plus. Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Andre, M.; Bolton, M.; Bougeret, J.-L.; Bowen, T. A.; Burgess, D.; Cattell, C. A.; Chandran, B. D. G.; Chaston, C. C.; Chen, C. H. K.; Choi, M. K.; Connerney, J. E.; Cranmer, S.; Diaz-Aguado, M.; Donakowski, W.; Drake, J. F.; Farrell, W. M.; Fergeau, P.; Fermin, J.; Fischer, J.; Fox, N.; Glaser, D.; Goldstein, M.; Gordon, D.; Hanson, E.; Harris, S. E.; Hayes, L. M.; Hinze, J. J.; Hollweg, J. V.; Horbury, T. S.; Howard, R. A.; Hoxie, V.; Jannet, G.; Karlsson, M.; Kasper, J. C.; Kellogg, P. J.; Kien, M.; Klimchuk, J. A.; Krasnoselskikh, V. V.; Krucker, S.; Lynch, J. J.; Maksimovic, M.; Malaspina, D. M.; Marker, S.; Martin, P.; Martinez-Oliveros, J.; McCauley, J.; McComas, D. J.; McDonald, T.; Meyer-Vernet, N.; Moncuquet, M.; Monson, S. J.; Mozer, F. S.; Murphy, S. D.; Odom, J.; Oliverson, R.; Olson, J.; Parker, E. N.; Pankow, D.; Phan, T.; Quataert, E.; Quinn, T.; Ruplin, S. W.; Salem, C.; Seitz, D.; Sheppard, D. A.; Siy, A.; Stevens, K.; Summers, D.; Szabo, A.; Timofeeva, M.; Vaivads, A.; Velli, M.; Yehle, A.; Werthimer, D.; Wygant, J. R. 2016-12-01 NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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Sample records for open solar magnetic