Sample records for solar-minimum corona unraveled

  1. A study of the background corona near solar minimum

    Microsoft Academic Search

    Kuniji Saito; Arthur I. Poland; Richard H. Munro

    1977-01-01

    The white light coronagraph data from Skylab is used to investigate the equatorial and polarK andF coronal components during the declining phase of the solar cycle near solar minimum. Measurements of coronal brightness and polarization brightness product between 2.5 and 5.5R? during the period of observation (May 1973 to February 1974) lead to the conclusions that: (1) the equatorial corona

  2. A study of the background corona near solar minimum

    NASA Technical Reports Server (NTRS)

    Saito, K.; Poland, A. I.; Munro, R. H.

    1977-01-01

    Equatorial and polar K and F coronal components during the declining phase of the solar cycle are studied through use of the white light coronagraph data obtained by Skylab. At this phase of the solar cycle, streams and holes dominate the equatorial corona (approximately 50 and 30% of the time, respectively) between 2.5 and 5.5 solar radii; however, two episodes are noted when equatorial background density of the corona could be distinguished. The derived background density is less than 15% below values predicted by the models of Newkirk (1967) and Saito (1970). The brightness of the F-corona is also discussed.

  3. Faraday Rotation Fluctuations of MESSENGER radio signals through the Corona during the 2009 Solar Minimum.

    NASA Astrophysics Data System (ADS)

    Wexler, David; Vierinen, Juha; Coster, Anthea; Jensen, Elizabeth A.

    2015-04-01

    Faraday rotation (FR) techniques have been used to probe variations of coronal plasma velocity, density and magnetic field. The plane of polarization for an electromagnetic wave rotates in proportion to the integrated product of parallel magnetic field components and electron density along the radio signal line-of-sight as directed towards the receiving antenna. Fluctuations in FR through the corona thus represent the evolution of these line-integrated plasma parameters, providing a unique measurement of regional corona physics. The MESSENGER spacecraft radio 8 GHz radio beacon, transmitting through the corona at offsets 1.6 to 1.9 solar radii and near-equatorial heliolatitude, was recorded on the Green Bank radio telescope during the solar minimum of 2009. Here we reanalyze at higher temporal resolution the data previously published (Jensen et al 2013, Solar Physics 285:83-95). Combinations of coherent and incoherent integration were used to estimate Stokes parameters, from which the FR phase differences were obtained for serial one-second frames. Results were concatenated and corrected for phase wrap-around to produce a continuous FR phase curve. The general FR phase curve was broad and sweeping, with greatest spectral power observed in periods of hours. Also, finer wave-like fluctuations were noted with periods on the order of 100’s of seconds. With the lowest-frequency components removed by detrending techniques, spectral analysis revealed a power spectrum of form P=k

  4. How unprecedented a solar minimum was it?

    PubMed

    Russell, C T; Jian, L K; Luhmann, J G

    2013-05-01

    The end of the last solar cycle was at least 3 years late, and to date, the new solar cycle has seen mainly weaker activity since the onset of the rising phase toward the new solar maximum. The newspapers now even report when auroras are seen in Norway. This paper is an update of our review paper written during the deepest part of the last solar minimum [1]. We update the records of solar activity and its consequent effects on the interplanetary fields and solar wind density. The arrival of solar minimum allows us to use two techniques that predict sunspot maximum from readings obtained at solar minimum. It is clear that the Sun is still behaving strangely compared to the last few solar minima even though we are well beyond the minimum phase of the cycle 23-24 transition. PMID:25685425

  5. How unprecedented a solar minimum was it?

    PubMed Central

    Russell, C.T.; Jian, L.K.; Luhmann, J.G.

    2012-01-01

    The end of the last solar cycle was at least 3 years late, and to date, the new solar cycle has seen mainly weaker activity since the onset of the rising phase toward the new solar maximum. The newspapers now even report when auroras are seen in Norway. This paper is an update of our review paper written during the deepest part of the last solar minimum [1]. We update the records of solar activity and its consequent effects on the interplanetary fields and solar wind density. The arrival of solar minimum allows us to use two techniques that predict sunspot maximum from readings obtained at solar minimum. It is clear that the Sun is still behaving strangely compared to the last few solar minima even though we are well beyond the minimum phase of the cycle 23–24 transition. PMID:25685425

  6. The unusual solar minimum: magnetic fields in the heliosphere

    NASA Astrophysics Data System (ADS)

    Balogh, Andre

    Solar cycle 23 has concluded with a minimum activity interval that was significantly longer than all recent cycles for which relatively comprehensive observations are available. In addition to a lack of sunspots, the sun's polar magnetic fields were significantly weaker than measured previously. The solar wind momentum flux was much reduced (by about 40 percent), and the magnetic flux density measured in the heliosphere also decreased by about a third with respect to the previous solar minimum. In this paper, primarily Ulysses magnetic field observations from the two solar minima, in 1996 and 2005-2008 are compared and related to the magnetic field structure in the corona, as diagnosed by the coronal temperatures indicated by the obser-vation of solar wind ion charge state distributions. Comparison is also made with equivalent observations near 1 AU. The weaker polar fields have led to a larger latitudinal excursion of the coronal neutral line, and therefore to the persistence of a more pronounced excursion of the Heliospheric Current Sheet. In the heliosphere, there was also a reduced absolute level of power in the magnetic fluctuations, although the weakness of the magnetic field led to comparable levels of relative magnetic fluctuation power. There was also even less evidence of any latitudi-nal asymmetry in the heliospheric magnetic field than during the previous minimum. Although the minimum appears to be over and solar cycle 24 has started with still a relatively small sunspot count, heliospheric observation during the unusual minimum can be used to probe the robustness of cosmic ray propagation and modulation models.

  7. NEWLY DISCOVERED GLOBAL TEMPERATURE STRUCTURES IN THE QUIET SUN AT SOLAR MINIMUM

    SciTech Connect

    Huang Zhenguang; Frazin, Richard A.; Landi, Enrico; Manchester, Ward B.; Gombosi, Tamas I. [Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Vasquez, Alberto M. [Instituto de Astronomia y Fisica del Espacio, CONICET-University of Buenos Aires, Ciudad de Buenos Aires, CC 67-Suc 28 (Argentina)

    2012-08-20

    Magnetic loops are building blocks of the closed-field corona. While active region loops are readily seen in images taken at EUV and X-ray wavelengths, quiet-Sun (QS) loops are seldom identifiable and are therefore difficult to study on an individual basis. The first analysis of solar minimum (Carrington Rotation 2077) QS coronal loops utilizing a novel technique called the Michigan Loop Diagnostic Technique (MLDT) is presented. This technique combines Differential Emission Measure Tomography and a potential field source surface (PFSS) model, and consists of tracing PFSS field lines through the tomographic grid on which the local differential emission measure is determined. As a result, the electron temperature T{sub e} and density N{sub e} at each point along each individual field line can be obtained. Using data from STEREO/EUVI and SOHO/MDI, the MLDT identifies two types of QS loops in the corona: so-called up loops in which the temperature increases with height and so-called down loops in which the temperature decreases with height. Up loops are expected, however, down loops are a surprise, and furthermore, they are ubiquitous in the low-latitude corona. Up loops dominate the QS at higher latitudes. The MLDT allows independent determination of the empirical pressure and density scale heights, and the differences between the two remain to be explained. The down loops appear to be a newly discovered property of the solar minimum corona that may shed light on the physics of coronal heating. The results are shown to be robust to the calibration uncertainties of the EUVI instrument.

  8. An equatorial coronal hole at solar minimum

    NASA Technical Reports Server (NTRS)

    Bromage, B. J. I.; DelZanna, G.; DeForest, C.; Thompson, B.; Clegg, J. R.

    1997-01-01

    The large transequatorial coronal hole that was observed in the solar corona at the end of August 1996 is presented. It consists of a north polar coronal hole called the 'elephant's trunk or tusk'. The observations of this coronal hole were carried out with the coronal diagnostic spectrometer onboard the Solar and Heliospheric Observatory (SOHO). The magnetic field associated with the equatorial coronal hole is strongly connected to that of the active region at its base, resulting in the two features rotating at almost the same rate.

  9. A model of the trapped electron population for solar minimum

    NASA Technical Reports Server (NTRS)

    Teague, M. J.; Vette, J. I.

    1974-01-01

    A model is presented of the trapped electron environment of solar minimum conditions. Solar maximum models have been presented for the inner radiation zone (AE-5 1967), and for the outer radiation zone (AE-4 1967). The present solar minimum model consists of an inner zone model (AE-5 1975 Projected) with an epoch of 1975, and an outer zone model with an epoch of 1964. With only minor modifications this latter model is identical to the AE-4 1964 model presented previous. The model, however, has not previously been issued in computer form. AE-4 1964 is based upon satellite data, while the inner zone solar minimum model AE-5 1975 Projected consists entirely of extrapolations from AE-5 1967. While the two components of the solar minimum model have epochs 11 years part, it is assumed that any differences between the successive solar minima are smaller than the model error, and the complete model is associated with an epoch of 1975.

  10. The heliospheric magnetic field at solar minimum as observed by ULYSSES

    NASA Astrophysics Data System (ADS)

    Forsyth, F. J.; Balogh, A.; Horbury, T. S.; Smith, E. J.

    1997-05-01

    Since February 1992 the Ulysses spacecraft has been in a polar orbit round the Sun, reaching 80 deg heliolatitude over the south pole in September 1994 and over the north pole in July 1995. During this time solar activity has been gradually declining towards its present minimum in mid-1996. We discuss how the large scale configuration of the heliospheric magnetic field and its embedded current sheet have evolved throughout this period, based upon measurements obtained by the magnetometer experiment on Ulysses, contrasting the snapshot of the field configuration obtained under solar minimum conditions during the fast transit from south pole to north pole with the results from earlier years where the slower traversal of latitude allowed efffects of the evolution of the corona with solar activity to be more apparent.

  11. Recent Studies of the Behavior of the Sun's White-Light Corona Over Time

    NASA Technical Reports Server (NTRS)

    SaintCyr, O. C.; Young, D. E.; Pesnell, W. D.; Lecinski, A.; Eddy, J.

    2008-01-01

    Predictions of upcoming solar cycles are often related to the nature and dynamics of the Sun's polar magnetic field and its influence on the corona. For the past 30 years we have a more-or-less continuous record of the Sun's white-light corona from groundbased and spacebased coronagraphs. Over that interval, the large scale features of the corona have varied in what we now consider a 'predictable' fashion--complex, showing multiple streamers at all latitudes during solar activity maximum; and a simple dipolar shape aligned with the rotational pole during solar minimum. Over the past three decades the white-light corona appears to be a better indicator of 'true' solar minimum than sunspot number since sunspots disappear for months (even years) at solar minimum. Since almost all predictions of the timing of the next solar maximum depend on the timing of solar minimum, the white-light corona is a potentially important observational discriminator for future predictors. In this contribution we describe recent work quantifying the large-scale appearance of the Sun's corona to correlate it with the sunspot record, especially around solar minimum. These three decades can be expanded with the HAO archive of eclipse photographs which, although sparse compared to the coronagraphic coverage, extends back to 1869. A more extensive understanding of this proxy would give researchers confidence in using the white-light corona as an indicator of solar minimum conditions.

  12. Analyzing the IAR with IRI During the Recent Solar Minimum

    NASA Technical Reports Server (NTRS)

    Ivanov, S.; Klenzing, J.; Simoes, F.

    2012-01-01

    The 2008-2009 solar minimum was deeper than any within the past century. As such, the performance of the empirical International Reference Ionosphere (IRI) model was impacted. This impact manifested as a disagreement between predicted and measured characteristic separation in frequency for a wave resonating within an Ionospheric Alfven Resonator (IAR). The predicted value of the characteristic was a factor of three lower than what was measured by the Communication/Navigation Outage Forecast System (C/NOFS). Analyzing the model performance and comparing output with measured ionospheric values showed that more than half of the inaccuracy could be explained by inaccuracies in the output of the model. The 2008-2009 solar minimum was outside of the bounds of the effectiveness of the empirical IRI model. Incorporating recent data measurements and new indices would increase the accuracy of IRI during this period.

  13. LANGMUIR WAVE ACTIVITY: COMPARING THE ULYSSES SOLAR MINIMUM AND SOLAR MAXIMUM ORBITS

    E-print Network

    California at Berkeley, University of

    ). The top three panels correspond to the southern segment of the solar minimum orbit; repeated passesLANGMUIR WAVE ACTIVITY: COMPARING THE ULYSSES SOLAR MINIMUM AND SOLAR MAXIMUM ORBITS R. J at the electron plasma frequency) during the solar minimum and solar maximum orbits of Ulysses. At high latitudes

  14. The asymmetrical features in electron density during extreme solar minimum

    NASA Astrophysics Data System (ADS)

    Zhang, Xuemin; Shen, Xuhui; Liu, Jing; Yao, Lu; Yuan, Guiping; Huang, Jianping

    2014-12-01

    The variations of plasma density in topside ionosphere during 23rd/24th solar cycle minimum attract more attentions in recently years. In this analysis, we use the data of electron density (Ne) from DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite at the altitude of 660-710 km to investigate the solstitial and equinoctial asymmetry under geomagnetic coordinate system at LT (local time) 1030 and 2230 during 2005-2010, especially in solar minimum years of 2008-2009. The results reveal that ?Ne (December-June) is always positive over Southern Hemisphere and negative over northern part whatever at LT 1030 or 2230, only at 0-10°N the winter anomaly occurs with ?Ne (December-June) > 0, and its amplitude becomes smaller with the declining of solar flux from 2005 to 2009. The ?Ne between September and March is completely negative during 2005-2008, but in 2009, it turns to be positive at latitudes of 20°S-40°N at LT 1030 and 10°S-20°N at LT 2230. Furthermore, the solstitial and equinoctial asymmetry index (AI) are calculated and studied respectively, which all depends on local time, latitude and longitude. The notable differences occur at higher latitudes in solar minimum year of 2009 with those in 2005-2008. The equinoctial AI at LT 2230 is quite consistent with the variational trend of solar flux with the lowest absolute AI occurring in 2009, the extreme solar minimum, but the solstitial AI exhibits abnormal enhancement during 2008 and 2009 with bigger AI than those in 2005-2007. Compared with the neutral compositions at 500 km altitude, it illustrates that [O/N2] and [O] play some roles in daytime and nighttime asymmetry of Ne at topside ionosphere.

  15. Transient flows of the solar wind associated with small-scale solar activity in solar minimum

    NASA Astrophysics Data System (ADS)

    Slemzin, Vladimir; Veselovsky, Igor; Kuzin, Sergey; Gburek, Szymon; Ulyanov, Artyom; Kirichenko, Alexey; Shugay, Yulia; Goryaev, Farid

    The data obtained by the modern high sensitive EUV-XUV telescopes and photometers such as CORONAS-Photon/TESIS and SPHINX, STEREO/EUVI, PROBA2/SWAP, SDO/AIA provide good possibilities for studying small-scale solar activity (SSA), which is supposed to play an important role in heating of the corona and producing transient flows of the solar wind. During the recent unusually weak solar minimum, a large number of SSA events, such as week solar flares, small CMEs and CME-like flows were observed and recorded in the databases of flares (STEREO, SWAP, SPHINX) and CMEs (LASCO, CACTUS). On the other hand, the solar wind data obtained in this period by ACE, Wind, STEREO contain signatures of transient ICME-like structures which have shorter duration (<10h), weaker magnetic field strength (<10 nT) and lower proton temperature than usual ICMEs. To verify the assumption that ICME-like transients may be associated with the SSA events we investigated the number of weak flares of C-class and lower detected by SPHINX in 2009 and STEREO/EUVI in 2010. The flares were classified on temperature and emission measure using the diagnostic means of SPHINX and Hinode/EIS and were confronted with the parameters of the solar wind (velocity, density, ion composition and temperature, magnetic field, pitch angle distribution of the suprathermal electrons). The outflows of plasma associated with the flares were identified by their coronal signatures - CMEs (only in few cases) and dimmings. It was found that the mean parameters of the solar wind projected to the source surface for the times of the studied flares were typical for the ICME-like transients. The results support the suggestion that weak flares can be indicators of sources of transient plasma flows contributing to the slow solar wind at solar minimum, although these flows may be too weak to be considered as separate CMEs and ICMEs. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement “eHeroes” (project n° 284461, www.eheroes.eu).

  16. UV solar irradiance low during recent solar minimum

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2011-10-01

    Solar irradiance, which varies with the 11-year solar cycle and on longer time scales, can affect temperatures and winds in the atmosphere, influencing Earth's climate. As the Sun currently wakes up from a period of low sunspot activity, researchers want to know how irradiance during the recent solar minimum compares to historical levels. In addition to understanding the total received power, it is important to know how various spectral bands behave, in particular, the ultraviolet, which causes heating and winds in the stratosphere. Lockwood analyzed solar ultraviolet spectral irradiance data from May 2003 to August 2005 from both the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) instrument on board the Upper Atmosphere Research Satellite (UARS) and the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) instrument on the Solar Radiation and Climate Experiment (SORCE) satellite. Using several different methods to intercalibrate the data, he developed a data composite that can be used to determine differences between the recent solar minimum and previous minima. The author found that solar irradiance during the recent sunspot minimum has been especially low. (Journal of Geophysical Research-Atmospheres, doi:10.1029/2010JD014746, 2011)

  17. Sources of Solar Wind at Solar Minimum: Constraints from Composition Data

    NASA Astrophysics Data System (ADS)

    Zurbuchen, Thomas H.; von Steiger, Rudolf; Gruesbeck, Jacob; Landi, Enrico; Lepri, Susan T.; Zhao, Liang; Hansteen, Viggo

    2012-11-01

    In this discussion of observational constraints on the source regions and acceleration processes of solar wind, we will focus on the ionic composition of the solar wind and the distribution of charge states of heavy elements such as oxygen and iron. We first focus on the now well-known bi-modal nature of solar wind, which dominates the heliosphere at solar minimum: Compositionally cool solar wind from polar coronal holes over-expands, filling a much larger solid angle than the coronal holes on the Sun. We use a series of remote and in-situ characteristics to derive a global geometric expansion factor of ˜5. Slower, streamer-associated wind is located near the heliospheric current sheet with a width of 10-20°, but in a well-defined band with a geometrically small transition width. We then compute charge states under the assumption of thermal electron distributions and temperature, velocity, and density profiles predicted by a recent solar wind model, and conclude that the solar wind originates from a hot source at around 1 million K, characteristic of the closed corona.

  18. MULTI-FLUID MODEL OF A STREAMER AT SOLAR MINIMUM AND COMPARISON WITH OBSERVATIONS

    SciTech Connect

    Ofman, Leon [Department of Physics, Catholic University of America, and NASA Goddard Space Flight Center, Code 671, Greenbelt, MD 20771 (United States); Abbo, Lucia; Giordano, Silvio, E-mail: Leon.Ofman@nasa.gov [INAF Astronomical Observatory of Turin (Italy)

    2011-06-10

    We present the results of a time-dependent 2.5-dimensional three-fluid magnetohydrodynamic model of the coronal streamer belt, which is compared with the slow solar wind plasma parameters obtained in the extended corona by the UV spectroscopic data from the Ultraviolet Coronagraph Spectrometer (UVCS) on board SOHO during the past minimum of solar activity (Carrington Rotation 1913). Our previous three-fluid streamer model has been improved by considering the solar magnetic field configuration relevant for solar minimum conditions, and preferential heating for O{sup 5+} ions. The model was run until a fully self-consistent streamer solution was obtained in the quasi-steady state. The plasma parameters from the multi-fluid model were used to compute the expected UV observables from H I Ly{alpha} 1216 A and O VI 1032 A spectral lines, and the results were compared in detail with the UVCS measurements. A good agreement between the model and the data was found. The results of the study provide insight into the acceleration and heating of the multi-ion slow solar wind.

  19. Ion Temperatures in the Low Solar Corona: Polar Coronal Holes at Solar Minimum

    E-print Network

    Enrico Landi; Steven R. Cranmer

    2008-09-30

    In the present work we use a deep-exposure spectrum taken by the SUMER spectrometer in a polar coronal hole in 1996 to measure the ion temperatures of a large number of ions at many different heights above the limb between 0.03 and 0.17 solar radii. We find that the measured ion temperatures are almost always larger than the electron temperatures and exhibit a non-monotonic dependence on the charge-to-mass ratio. We use these measurements to provide empirical constraints to a theoretical model of ion heating and acceleration based on gradually replenished ion-cyclotron waves. We compare the wave power required to heat the ions to the observed levels to a prediction based on a model of anisotropic magnetohydrodynamic turbulence. We find that the empirical heating model and the turbulent cascade model agree with one another, and explain the measured ion temperatures, for charge-to-mass ratios smaller than about 0.25. However, ions with charge-to-mass ratios exceeding 0.25 disagree with the model; the wave power they require to be heated to the measured ion temperatures shows an increase with charge-to-mass ratio (i.e., with increasing frequency) that cannot be explained by a traditional cascade model. We discuss possible additional processes that might be responsible for the inferred surplus of wave power.

  20. Earth's inner magnetosphere response to recent solar minimum

    NASA Astrophysics Data System (ADS)

    Ganushkina, Natalia

    Understanding the time-varying electromagnetic field configuration and the consequent charged particle dynamics in the Earth's space environment is fundamentally important both for sci-entific and space weather purposes. Recent solar minimum implied new aspects on the inner magnetosphere states. We have developed a time-evolving model for the inner magnetosphere magnetic field. Based on available in-situ observations of the magnetospheric magnetic field, the model gives a global representation of the magnetic field evolution during specified time periods. The main advantage of this event-oriented model is its ability to reproduce both the larger-scale and smaller-scale variations of the magnetic field during substorms and storms. We have incor-porated this model into our particle tracing procedure IMPTAM (Inner Magnetosphere Particle Transport and Acceleration Model), in which we trace particles with arbitrary pitch angles nu-merically in the drift approximation. From the other hand, we represent substorm-associated electromagnetic fields by adding electromagnetic pulses. There electric field is given by Gaus-sian pulse with azimuthal field component propagating inward with a velocity dependent on radial distance. The magnetic field from this pulse is calculated by Faraday's law. We model particle inward motion and energization by a series of electric field pulses representing substorm activations during storm events. We model several small storms occurred during 2006-2009 We study the role of small-scale variations of the electromagnetic field in the evolution of energetic particle populations in the near-Earth's magnetosphere.

  1. Estimates of galactic cosmic ray shielding requirements during solar minimum

    SciTech Connect

    Townsend, L.W.; Nealy, J.E.; Wilson, J.W.; Simonsen, L.C.

    1990-02-01

    Estimates of radiation risk from galactic cosmic rays are presented for manned interplanetary missions. The calculations use the Naval Research Laboratory cosmic ray spectrum model as input into the Langley Research Center galactic cosmic ray transport code. This transport code, which transports both heavy ions and nucleons, can be used with any number of layers of target material, consisting of up to five different arbitrary constituents per layer. Calculated galactic cosmic ray fluxes, dose and dose equivalents behind various thicknesses of aluminum, water and liquid hydrogen shielding are presented for the solar minimum period. Estimates of risk to the skin and the blood-forming organs (BFO) are made using 0-cm and 5-cm depth dose/dose equivalent values, respectively, for water. These results indicate that at least 3.5 g/sq cm (3.5 cm) of water, or 6.5 g/sq cm (2.4 cm) of aluminum, or 1.0 g/sq cm (14 cm) of liquid hydrogen shielding is required to reduce the annual exposure below the currently recommended BFO limit of 0.5 Sv. Because of large uncertainties in fragmentation parameters and the input cosmic ray spectrum, these exposure estimates may be uncertain by as much as a factor of 2 or more. The effects of these potential exposure uncertainties or shield thickness requirements are analyzed.

  2. Cosmic ray particles behavior during last solar minimum

    NASA Astrophysics Data System (ADS)

    Rockenbach, Marlos; Dal Lago, Alisson; Munakata, Kazuoki; Kato, Chihiro; Kuwabara, Takao; Bieber, John; Schuch, Nelson; Duldig, Marc; Humble, John; Jassar, Hala Al; Sharma, Madan; Sabbah, Ismail

    2013-04-01

    The work presents the Heliosphere characterization during the minimum solar activity. It is possible to identify phenomena caused by the Corrotating Interaction Regions - CIRs, during this solar activity phase. CIRs can be visualized in satellite data for each 27 days, approximately, and it is frequently accompanied by the Earth crossing through the Heliospheric Current Sheath - HCS. These crossing occur in a period of time lower than a day, and it is possible to study the behavior of cosmic rays particles in two different regions with opposite magnetic field polarities. The last solar minimum was special because their long duration and it was the first that the Global Muon Detector Network - GMDN operated in its full capacity. This cosmic ray detectors network is composed by muon scintillators installed in Nagoya - Japan, Hobart - Australia, São Martinho da Serra - Brazil and Kuwait City - Kuwait. Analyzing the GMDN data together with data from SOHO and/or ACE satellites it is possible to study the behavior of the cosmic ray particles and presents a Heliosphere characterization during the minimum solar activity, giving a better understanding of the cosmic ray particles modulation.

  3. Ion-neutral Coupling During Deep Solar Minimum

    NASA Technical Reports Server (NTRS)

    Huang, Cheryl Y.; Roddy, Patrick A.; Sutton, Eric K.; Stoneback, Russell; Pfaff, Robert F.; Gentile, Louise C.; Delay, Susan H.

    2013-01-01

    The equatorial ionosphere under conditions of deep solar minimum exhibits structuring due to tidal forces. Data from instruments carried by the Communication Navigation Outage Forecasting System (CNOFS) which was launched in April 2008 have been analyzed for the first 2 years following launch. The Planar Langmuir Probe (PLP), Ion Velocity Meter (IVM) and Vector Electric Field Investigation (VEFI) all detect periodic structures during the 20082010 period which appear to be tides. However when the tidal features detected by these instruments are compared, there are distinctive and significant differences between the observations. Tides in neutral densities measured by the Gravity Recovery and Climate Experiment (GRACE) satellite were also observed during June 2008. In addition, Broad Plasma Decreases (BPDs) appear as a deep absolute minimum in the plasma and neutral density tidal pattern. These are co-located with regions of large downward-directed ion meridional velocities and minima in the zonal drifts, all on the nightside. The region in which BPDs occur coincides with a peak in occurrence rate of dawn depletions in plasma density observed on the Defense Meterological Satellite Program (DMSP) spacecraft, as well as a minimum in radiance detected by UV imagers on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) and IMAGE satellites

  4. Solar Polar Coronal Hole Areas Through the Past Solar Minimum

    NASA Astrophysics Data System (ADS)

    Hess Webber, Shea; Karna, N.; Pesnell, W. D.; Kirk, M.

    2011-05-01

    We have used the perimeter tracking algorithm and analysis of EIT synoptic maps to extend our timeseries of polar coronal hole areas through solar minimum (through 2010). Both algorithms use 171, 195, and 304 Å images from the Extreme ultraviolet Imaging Telescope (EIT) on SOHO, the first to measure the perimeter of polar coronal holes as they appear on the limbs and the second the area of the polar coronal hole during each Carrington rotation. Line-of-sight magnetic field synoptic maps are also used to estimate the polar coronal hole area. We have updated the time series and we are analyzing uncertainties in EIT ephemeris data. We remain convinced that the northern polar hole area is measurably smaller in the recent minimum than it was at the beginning of cycle 23, while the southern polar hole area is roughly the same. Polar hole areas found via perimeter tracking agree within uncertainty with those determined using EIT synoptic map analysis. This work was supported by the Solar Dynamics Observatory.

  5. Radiation Environment on Mir Orbital Station During Solar Minimum

    NASA Technical Reports Server (NTRS)

    Badhwar, Gautam D.; McKay, Gordon A. (Technical Monitor)

    1999-01-01

    Space radiation poses a significant risk for the stay and rotation cycle of astronauts on the International Space Station (ISS). The ISS is in the same orbit as the Mir orbital station and as such, data acquired onboard the Mir station is of direct applicability to the ISS astronaut. During the seven NASA-Mir missions, data were acquired with a variety of both passive and active detectors, including measurements of astronaut doses. This paper describes these measurements and comparisons with measurements carried out by other groups. It is shown that trapped protons absorbed can be very well described by quadratic equation in In(p), where p is the atmospheric density. Similarly, the galactic cosmic ray absorbed dose is nearly exponentially related to the deceleration potential. The average radiation quality factor with the ICRP-60 definition is about 2.44. Using the measured quality factor, absorbed crew doses, and estimates of neutron dose equivalent, leads to crew stay times as short as 9 months during a deep solar minimum. The data are compared with in vivo dose estimates using chromosome aberrations (simple translocations and total exchange) on same astronauts.

  6. 3D Coronal Density Reconstruction and Retrieving the Magnetic Field Structure during Solar Minimum

    NASA Astrophysics Data System (ADS)

    Kramar, M.; Airapetian, V.; Miki?, Z.; Davila, J.

    2014-08-01

    Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal phenomena at all scales. We employed STEREO/COR1 data obtained during a deep minimum of solar activity in February 2008 (Carrington Rotation CR 2066) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from 1.5 to 4 R? using a tomography method. With this, we qualitatively deduced structures of the coronal magnetic field. The 3D electron-density analysis is complemented by the 3D STEREO/EUVI emissivity in the 195 Å band obtained by tomography for the same CR. A global 3D MHD model of the solar corona was used to relate the reconstructed 3D density and emissivity to open/closed magnetic-field structures. We show that the density-maximum locations can serve as an indicator of current-sheet position, while the locations of the density-gradient maximum can be a reliable indicator of coronal-hole boundaries. We find that the magnetic-field configuration during CR 2066 has a tendency to become radially open at heliocentric distances greater than 2.5 R?. We also find that the potential-field model with a fixed source surface is inconsistent with the boundaries between the regions with open and closed magnetic-field structures. This indicates that the assumption of the potential nature of the coronal global magnetic field is not satisfied even during the deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal-field models and test the accuracy of the magnetic-field approximations for coronal modeling.

  7. Cosmic rays during the unusual solar minimum of 2009

    NASA Astrophysics Data System (ADS)

    Gil, Agnieszka

    Examine the solar activity (SA) parameters during the quite long-lasting minimum epoch 23/24 shows that their values differ substantially in comparison with those measured in previous solar minimum epochs. The Sun was extremely quiet and there were nearly no sunspots (e.g. Smith, 2011). The averaged proton density was lower during this minimum (˜ 0.70) than in the three previous minimum epochs (Jian et al., 2011). The averaged strength of the interplanetary magnetic field during the last minimum was truly low (drop of ˜ 0.36) and the solar wind dynamic pressure decrease (˜ 0.22) was noticed (McComas et al., 2008). Solar polar magnetic fields were weaker (˜ 0.40) during this minimum in comparison with the last three minimum epochs of SA (Wang et al., 2009). Kirk et al. (2009) showed that EUV polar coronal holes area was less (˜ 0.15) than at the beginning of the Solar Cycle no. 23. The solar total irradiance at 1AU was lower more than 0.2Wm (-2) than in the last minimum in 1996 (Fröhlich, 2009). Values of the solar radio flux f10.7 were smaller than for the duration of the recent four minima (Jian et al., 2011). The tilt angle of the heliospheric current sheet declined much slower during the recent minimum in comparison with the previous two. The values of galactic cosmic rays (GCR) intensity measured by neutron monitors were the highest ever recorded (e.g. Moraal and Stoker, 2010). In 2007 neutron monitors achieved values measured during the last negative polarity minimum, 1987, and continued to grow throughout the beginning of 2010. In the same time, the level of anomalous cosmic ray intensities was comparable with the 1987 minimum (Leske et al., 2013). The average amplitude of the 27-days recurrence of the GCR intensity was as high as during the previous minimum epoch 1996 (positive polarity), much higher than during minimum one Hale cycle back (Gil et al., 2012). Modzelewska and Alania (2013) showed that 27-days periodicity of the GCR intensity stable during 2007-2008 evolved to longer period (up to 33-36 days) during 2009. Alania et al. (2014, submitted to JGR) have reported that the 2009 growth in the GCR intensity mostly was related with drop in the solar wind velocity, the strength of the interplanetary magnetic field, and the drift during the negative polarity epoch. Frohlich (2009) argued that the recent minimum was caused by a global temperature decline of 0.2 K in the effective temperature of the Sun. Dikpati (2013) suggested that the reason of the prolonged and deep minimum was somehow different operation of solar dynamo. On the other hand, revisions of the proxies showed that the Maunder Minimum was the latest, but not the only, of the grand minimum ages of solar activity that occurred in the past (e.g. Jones et al., 2010). It might be the case that the last 23/24 solar minimum was the precursor of the end of the Modern grand maximum (e.g. Usoskin, 2013). References: 1.Alania M.V, R. Modzelewska, A. Wawrzynczak, 2014, submitted to JGR 2.Dikpati M., SSRv 176, 279-287, 2013 3.Fröhlich C., A&A 501, L27-L30, 2009 4.Gil A., R. Modzelewska, M.V Alania, AdSpR 50, 712-715, 2012 5.Jian L.K., C.T. Russell, J.G. Luhmann, SoPh 274, 321-344, 2011 6.Jones Ch.A., M.J. Thompson, S.M. Tobias, SSRv 152, 591-616, 2010 7.Kirk M. S., W.D. Pesnell, C. A. Young, S.A. Hess Webber, SoPh 257, 99-112, 2009 8.Leske R. A., A.C. Cummings, R.A. Mewaldt, E.C. Stone, SSRv 176, 253-263, 2013 9.McComas D.J., R.W. Ebert, H.A. Elliott, et al., GeoRL 35, CiteID L18103, 2008 10.Modzelewska R, M.V. Alania, SoPh 286, 593-607, 2013 11.Moraal H., P.H. Stoker, JGR 115, CiteID A12109, 2010 12.Smith E.J, JASTP 73, 277-289, 2011 13.Usoskin I.G., LRSP 10, doi 10.12942/lrsp-2013-1, 2013 14.Wang Y.-M., E. Robbrecht, N.R. Sheeley, ApJ. 707, 1372-1386, 2009

  8. Elemental GCR Observations during the 2009-2010 Solar Minimum Period

    NASA Technical Reports Server (NTRS)

    Lave, K. A.; Israel, M. H.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

    2013-01-01

    Using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer (ACE), we present new measurements of the galactic cosmic ray (GCR) elemental composition and energy spectra for the species B through Ni in the energy range approx. 50-550 MeV/nucleon during the record setting 2009-2010 solar minimum period. These data are compared with our observations from the 1997-1998 solar minimum period, when solar modulation in the heliosphere was somewhat higher. For these species, we find that the intensities during the 2009-2010 solar minimum were approx. 20% higher than those in the previous solar minimum, and in fact were the highest GCR intensities recorded during the space age. Relative abundances for these species during the two solar minimum periods differed by small but statistically significant amounts, which are attributed to the combination of spectral shape differences between primary and secondary GCRs in the interstellar medium and differences between the levels of solar modulation in the two solar minima. We also present the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe for both solar minimum periods, and demonstrate that these ratios are reasonably well fit by a simple "leaky-box" galactic transport model that is combined with a spherically symmetric solar modulation model.

  9. Field-aligned currents during the extreme solar minimum between the solar cycles 23 and 24

    NASA Astrophysics Data System (ADS)

    Wing, S.; Ohtani, S.; Johnson, J.; Wilson, G. R.; Higuchi, T.

    2013-12-01

    The solar minimum between solar cycles 23 and 24 was unusually long and deep. The afternoon upward region-1 (R1) field-aligned current (FAC) response to this extreme solar minimum was examined and compared to that for the entire solar cycle 23. The responses on the dayside are different than those on the nightside. The field-aligned current density (J//) on the dayside, at 12 - 17 MLT appears to peak in the declining phase of the solar max, in 2003, when the solar wind speed peaks, whereas J// on the nightside, at 18 - 23 MLT, appears insensitive to the solar cycle. In the interval 1995 - 2010, J// at 15 - 17 MLT appears to reach the lowest value during the extreme solar minimum in 2009, when the solar wind speed also reaches the lowest value. The J// response is consistent with our previous study that shows that afternoon R1 at 12 - 17 MLT is located mostly on open field lines or at the boundary layer, where the current is driven by the velocity shear at magnetopause boundary. However, on the nightside, at 18 - 23 MLT, R1 is located mostly on the closed field lines where J// is not driven directly and immediately by the solar wind. The FAC latitudinal width (?), on the other hand, shows the opposite trend. The nightside ? exhibits a solar cycle effect such that ? is smaller at the solar minimum and smallest during the extreme solar minimum in 2009, consistent with a previous study. However, the dayside ? exhibits little solar cycle effect. As a result, the FAC intensity exhibits a solar cycle variation at all local times and the FAC intensity is lower during the extreme solar minimum that that of the previous solar minimum.

  10. Midrange periodicity of basal component of solar radio flux during the extended solar minimum of cycle 23-24

    NASA Astrophysics Data System (ADS)

    De, Barin Kumar; Chakraborty, Monti; Roy, Rakesh; Guha, Anirban

    2014-03-01

    Radio observations serve as a powerful tool to study the physical conditions of the radio emitting sources for understanding the characteristics of solar atmosphere. It is also a useful method for understanding the physical properties and the dynamics of the solar corona. It is evident from various experimental observations that the recent 23-24 solar cycle minimum was elongated for much longer time compared to previous minima. In this paper, the mid-range periodicity (in the range of 50-250 days) for non-magnetic components of solar radio flux at eight discrete frequencies viz. 245, 410, 610, 1415, 2695, 4995, 8800 and 15400 MHz during the extended solar minimum period (2007-2009) have been explored using Lomb-Scargle periodogram technique. The periodicities obtained in the mid range (50-250 days) for different frequencies during this minimum have been identified with the periodicities within the range of standard deviation obtained from different analysis for different time span with different phase of previous solar cycles by different workers. The observations of basal component (non magnetic component of solar radio flux) are interpreted in terms of the internal dynamics of the Sun. The obtained periodicities also provide physical information about the source region of the solar atmosphere.

  11. Field-aligned currents during the extreme solar minimum between the solar cycles 23 and 24

    NASA Astrophysics Data System (ADS)

    Wing, Simon; Ohtani, Shinichi; Johnson, Jay; Wilson, Gordon R.; Higuchi, Tomoyuki

    2014-04-01

    The solar minimum between solar cycles 23 and 24 was unusually long and deep. The upward region-1 (R1) field-aligned current (FAC) response to this extreme solar minimum was investigated using Defense Meteorological Satellite Program observations. The solar cycle responses on the dayside are different than those on the nightside. The field-aligned current density (J//) on the dayside, at 12-17 magnetic local time (MLT), peaks in the declining phase of the solar cycle, in 2003, when the solar wind speed also peaks, whereas J// on the nightside, at 18-23 MLT, appears insensitive to the solar cycle. In 1995-2010, J// at 15-17 MLT reaches the lowest value during the extreme solar minimum in 2009, when the solar wind speed also reaches the lowest value. At 12-17 MLT, R1 is located mostly on open field lines or at the boundary layer, where the current is driven mostly by the velocity shear at the magnetopause boundary. However, on the nightside, R1 is located mostly on the closed field lines where J// is not driven directly and immediately by the solar wind. The nightside current width (?) exhibits a solar cycle effect such that ? is smaller at the solar minimum and smallest in 2009. However, the dayside ? exhibits little solar cycle effect. As a result, the FAC intensity (latitudinally integrated J//) exhibits a solar cycle variation at all local times and the FAC intensity is lower during the extreme solar minimum than that of the previous solar minimum.

  12. THE TURBULENT CASCADE AND PROTON HEATING IN THE SOLAR WIND DURING SOLAR MINIMUM

    SciTech Connect

    Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, CA (United States); Forman, Miriam A., E-mail: jtu46@wildcats.unh.edu, E-mail: Charles.Smith@unh.edu, E-mail: Bernie.Vasquez@unh.edu, E-mail: Joshua.Stawarz@Colorado.edu, E-mail: Miriam.Forman@sunysb.edu [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY (United States)

    2012-08-01

    The recently protracted solar minimum provided years of interplanetary data that were largely absent in any association with observed large-scale transient behavior on the Sun. With large-scale shear at 1 AU generally isolated to corotating interaction regions, it is reasonable to ask whether the solar wind is significantly turbulent at this time. We perform a series of third-moment analyses using data from the Advanced Composition Explorer. We show that the solar wind at 1 AU is just as turbulent as at any other time in the solar cycle. Specifically, the turbulent cascade of energy scales in the same manner proportional to the product of wind speed and temperature. Energy cascade rates during solar minimum average a factor of 2-4 higher than during solar maximum, but we contend that this is likely the result of having a different admixture of high-latitude sources.

  13. Wind Observations of Anomalous Cosmic Rays from Solar Minimum to Maximum

    NASA Technical Reports Server (NTRS)

    Reames, D. V.; McDonald, F. B.

    2003-01-01

    We report the first observation near Earth of the time behavior of anomalous cosmic-ray N, O, and Ne ions through the period surrounding the maximum of the solar cycle. These observations were made by the Wind spacecraft during the 1995-2002 period spanning times from solar minimum through solar maximum. Comparison of anomalous and galactic cosmic rays provides a powerful tool for the study of the physics of solar modulation throughout the solar cycle.

  14. Galactic Cosmic-Ray Energy Spectra and Composition during the 2009-2010 Solar Minimum Period

    NASA Technical Reports Server (NTRS)

    Lave, K. A.; Wiedenbeck, Mark E.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Israel, M. H..; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; VonRosenvinge, T. T.

    2013-01-01

    We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 <= Z <= 28 in the energy range approx. 50-550 MeV / nucleon. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than approx. 7%, and the relative abundances changed by less than approx. 4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2sigma, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple "leaky-box" galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

  15. GALACTIC COSMIC-RAY ENERGY SPECTRA AND COMPOSITION DURING THE 2009-2010 SOLAR MINIMUM PERIOD

    SciTech Connect

    Lave, K. A.; Binns, W. R.; Israel, M. H. [Department of Physics and the McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130 (United States); Wiedenbeck, M. E. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Christian, E. R.; De Nolfo, G. A.; Von Rosenvinge, T. T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Cummings, A. C.; Davis, A. J.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C. [California Institute of Technology, Pasadena, CA 91125 (United States)

    2013-06-20

    We report new measurements of the elemental energy spectra and composition of galactic cosmic rays during the 2009-2010 solar minimum period using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer. This period of time exhibited record-setting cosmic-ray intensities and very low levels of solar activity. Results are given for particles with nuclear charge 5 {<=} Z {<=} 28 in the energy range {approx}50-550 MeV nucleon{sup -1}. Several recent improvements have been made to the earlier CRIS data analysis, and therefore updates of our previous observations for the 1997-1998 solar minimum and 2001-2003 solar maximum are also given here. For most species, the reported intensities changed by less than {approx}7%, and the relative abundances changed by less than {approx}4%. Compared with the 1997-1998 solar minimum relative abundances, the 2009-2010 abundances differ by less than 2{sigma}, with a trend of fewer secondary species observed in the more recent time period. The new 2009-2010 data are also compared with results of a simple ''leaky-box'' galactic transport model combined with a spherically symmetric solar modulation model. We demonstrate that this model is able to give reasonable fits to the energy spectra and the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe. These results are also shown to be comparable to a GALPROP numerical model that includes the effects of diffusive reacceleration in the interstellar medium.

  16. A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval

    NASA Technical Reports Server (NTRS)

    Thompson, Barbara J.; Gibson, Sarah E.; Schroeder, Peter C.; Webb, David F.; Arge, Charles N.; Bisi, Mario M.; de Toma, Giuliana; Emery, Barbara A.; Galvin, Antoinette B.; Haber, Deborah A.; Jackson, Bernard V.; Jensen, Elizabeth A.; Leamon, Robert J.; Lei, Jiuhou; Manoharan, Periasamy K.; Mays, M. Leila; McIntosh, Patrick S.; Petrie, Gordon J.D.; Plunkett, Simon P.; Qian, Liying

    2011-01-01

    We present an overview of the data and models collected for the Whole Heliosphere Interval, an international campaign to study the three-dimensional solar heliospheric planetary connected system near solar minimum. The data and models correspond to solar Carrington Rotation 2068 (20 March 16 April 2008) extending from below the solar photosphere, through interplanetary space, and down to Earth's mesosphere. Nearly 200 people participated in aspects of WHI studies, analyzing and interpreting data from nearly 100 instruments and models in order to elucidate the physics of fundamental heliophysical processes. The solar and inner heliospheric data showed structure consistent with the declining phase of the solar cycle. A closely spaced cluster of low-latitude active regions was responsible for an increased level of magnetic activity, while a highly warped current sheet dominated heliospheric structure. The geospace data revealed an unusually high level of activity, driven primarily by the periodic impingement of high-speed streams. The WHI studies traced the solar activity and structure into the heliosphere and geospace, and provided new insight into the nature of the interconnected heliophysical system near solar minimum.

  17. A Topside Equatorial Ionospheric Density and Composition Climatology During and After Extreme Solar Minimum

    NASA Technical Reports Server (NTRS)

    Klenzing, J. H.; Simoes, F.; Ivanov, S.; Heelis, R. A.; Bilitza, D.; Pfaff, R. F.; Rowland, D. E.

    2011-01-01

    During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth's ionosphere and thermosphere when compared to previous solar minima. Among these are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Climatological altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the C/NOFS satellite to characterize the shape of the top side ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI-2007 model. Building on initial results reported by Heelis et al. [2009], here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.

  18. The distribution of solar wind speeds during solar minimum: Calibration for numerical solar wind modeling constraints on the source of the slow solar wind

    NASA Astrophysics Data System (ADS)

    McGregor, S. L.; Hughes, W. J.; Arge, C. N.; Owens, M. J.; Odstrcil, D.

    2011-03-01

    It took the solar polar passage of Ulysses in the early 1990s to establish the global structure of the solar wind speed during solar minimum. However, it remains unclear if the solar wind is composed of two distinct populations of solar wind from different sources (e.g., closed loops which open up to produce the slow solar wind) or if the fast and slow solar wind rely on the superradial expansion of the magnetic field to account for the observed solar wind speed variation. We investigate the solar wind in the inner corona using the Wang-Sheeley-Arge (WSA) coronal model incorporating a new empirical magnetic topology-velocity relationship calibrated for use at 0.1 AU. In this study the empirical solar wind speed relationship was determined by using Helios perihelion observations, along with results from Riley et al. (2003) and Schwadron et al. (2005) as constraints. The new relationship was tested by using it to drive the ENLIL 3-D MHD solar wind model and obtain solar wind parameters at Earth (1.0 AU) and Ulysses (1.4 AU). The improvements in speed, its variability, and the occurrence of high-speed enhancements provide confidence that the new velocity relationship better determines the solar wind speed in the outer corona (0.1 AU). An analysis of this improved velocity field within the WSA model suggests the existence of two distinct mechanisms of the solar wind generation, one for fast and one for slow solar wind, implying that a combination of present theories may be necessary to explain solar wind observations.

  19. The turbulent cascade and proton heating in the solar wind during solar minimum

    SciTech Connect

    Coburn, Jesse T.; Smith, Charles W.; Vasquez, Bernard J. [Physics Department and Space Science Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire (United States); Stawarz, Joshua E. [Department of Astrophysical and Planetary Sciences, University of Colorado at Boulder, Boulder, Colorado (United States); Forman, Miriam A. [Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, New York (United States)

    2013-06-13

    Solar wind measurements at 1 AU during the recent solar minimum and previous studies of solar maximum provide an opportunity to study the effects of the changing solar cycle on in situ heating. Our interest is to compare the levels of activity associated with turbulence and proton heating. Large-scale shears in the flow caused by transient activity are a source that drives turbulence that heats the solar wind, but as the solar cycle progresses the dynamics that drive the turbulence and heat the medium are likely to change. The application of third-moment theory to Advanced Composition Explorer (ACE) data gives the turbulent energy cascade rate which is not seen to vary with the solar cycle. Likewise, an empirical heating rate shows no significan changes in proton heating over the cycle.

  20. GPS-DERIVED LOCAL TEC MAPPING OVER PENINSULA MALAYSIA DURING SOLAR MINIMUM OF SUNSPOT CYCLE 24

    E-print Network

    S. K. Leong; T. A. Musa; K. A. Abdullah; R. Othman; S. Lim; C. Rizos

    The ionosphere is the major contributor of errors in Global Positioning System (GPS), especially during the 11-year sunspot cycle. The incoming 11-year sunspot cycle is expected to peak in 2013. The ionosphere condition is distinctly severe during ionospheric disturbances caused by high solar activity, which raises the question of how will this affect the ionosphere in the equatorial region, especially Malaysia. This study monitors the changes of Total Electron Content (TEC) by generating local TEC maps over Peninsula Malaysia using GPS measurements. The TEC maps show insignificant morphological changes in TEC variations during the period of study. The findings have widened the understanding of TEC variations in equatorial region, particularly during solar minimum.

  1. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Linker, Jon A.

    1997-02-01

    Under this contract, we have continued our investigations of the large scale structure of the solar corona and inner heliosphere using global magnetohydrodynamic (MHD) simulations. These computations have also formed the basis for studies of coronal mass ejections (CMES) using realistic coronal configurations. We have developed a technique for computing realistic magnetohydrodynamic (MHD) computations of the solar corona and inner heliosphere. To perform computations that can be compared with specific observations, it is necessary to incorporate solar observations into the boundary conditions. We have used the Wilcox Solar Observatory synoptic maps (collected during a solar rotation by daily measurements of the line-of-sight magnetic field at central meridian) to specify the radial magnetic field (B,) at the photosphere. For the initial condition, we use a potential magnetic field consistent with the specified distribution of B, at the lower boundary, and a wind solution consistent with the specified plasma density and temperature at the solar surface. Together this initial condition forms a (non-equilibrium) approximation of the state of the solar corona for the time-dependent MHD computation. The MHD equations are then integrated in time to steady state. Here we describe solutions relevant to a recent solar eclipse, as well as Ulysses observations. We have also developed a model configuration of solar minimum, useful for studying CME initiation and propagation.

  2. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.

    1997-01-01

    Under this contract, we have continued our investigations of the large scale structure of the solar corona and inner heliosphere using global magnetohydrodynamic (MHD) simulations. These computations have also formed the basis for studies of coronal mass ejections (CMES) using realistic coronal configurations. We have developed a technique for computing realistic magnetohydrodynamic (MHD) computations of the solar corona and inner heliosphere. To perform computations that can be compared with specific observations, it is necessary to incorporate solar observations into the boundary conditions. We have used the Wilcox Solar Observatory synoptic maps (collected during a solar rotation by daily measurements of the line-of-sight magnetic field at central meridian) to specify the radial magnetic field (B,) at the photosphere. For the initial condition, we use a potential magnetic field consistent with the specified distribution of B, at the lower boundary, and a wind solution consistent with the specified plasma density and temperature at the solar surface. Together this initial condition forms a (non-equilibrium) approximation of the state of the solar corona for the time-dependent MHD computation. The MHD equations are then integrated in time to steady state. Here we describe solutions relevant to a recent solar eclipse, as well as Ulysses observations. We have also developed a model configuration of solar minimum, useful for studying CME initiation and propagation.

  3. The Solar Oblateness at Solar Minimum as Observed by RHESSI/SAS II

    NASA Astrophysics Data System (ADS)

    Fivian, M. D.; Hudson, H. S.; Lin, R. P.

    2012-12-01

    The Solar Aspect System (SAS) of the RHESSI satellite measures the optical solar limb in the red continuum with a cadence typically set at 32 samples/s in each of three linear CCD sensors. RHESSI has observed the Sun continuously now for more than 10 years, and we have acquired a unique data set ranging almost over a full solar cycle and consisting of about 25x10^9 single data points. For a three month period during the active phase of the last solar cycle in 2004, the shape of the solar disk has been measured discovering an apparent excess oblateness which we attributed to the enhanced network. These measurements have led to the most accurate oblateness measurement to date, 8.01+-0.14 milli arcsec (Fivian et al., 2008), a value consistent with models predicting an oblateness from surface rotation. In order to avoid confusion between magnetic activity and a correlated brightness enhancement in the SAS signal, the SAS data has been masked using the SOHO/EIT284A data, and SDO/AIA for more recent data. The measured oblateness as function of the masking level is then extrapolated for a value of the underlaying, presumably non-magnetic sun. A recent and significantly improved calibration of the SAS data have allowed a new access to a measurement of the solar oblateness during the last, extended solar minimum. Here, we present the analysis of the RHESSI/SAS data during the solar minimum with the inferred interpretation for the oblateness signal.

  4. The Tilted Solar Dipole as Observed and Modeled during the 1996 Solar Minimum

    NASA Astrophysics Data System (ADS)

    Norton, A. A.; Raouafi, N.-E.; Petrie, G. J. D.

    2008-08-01

    We examine the tilt of the solar magnetic dipole away from the rotational axis near the 1996 solar minimum. A persistent tilted dipole may result from an MHD instability acting on the toroidal bands in the solar interior. Nonaxisymmetric eruption of sunspots has been predicted by dynamo theory and observed in sunspot location patterns. The decay of follower spots and the poleward migration of flux could create polar caps that are slightly misaligned with the north-south rotational axis. To investigate this, we analyze the coronal streamer geometry observed with LASCO-C2 and the center of gravity of the polar caps defined by coronal hole boundaries in EIT images and the unipolar magnetic regions in KPVT magnetograms. We model the coronal hole boundaries and neutral line locations by potential field source surface (PFSS) modeling using Kitt Peak magnetograms. Our results are consistent with an observed tilt of 5°-10° in the heliospheric current sheet at solar minimum and the idea of persistent off-axis magnetic polar caps for CRs 1911-1919. The coronal holes show a stable azimuthal angle for CRs 1911-1919 with a rotation rate slightly less than the Carrington rate. The PFSS modeling is able to recreate the observed coronal hole geometry and predict the maximum extent of the heliospheric current sheet as observed by streamer locations. A 6° observed tilt of the polar caps during this time is consistent with the analytical value provided from the PFSS dipole terms. However, the determination of a tilt of the magnetic polar caps is dominated by noise. The LASCO coronal streamer geometry traces out an 10° tilt of the solar dipole from the equatorial plane during CRs 1915-1919.

  5. Comparative Study of foF2 Measurements with IRI-2007 Model Predictions During Extended Solar Minimum

    NASA Technical Reports Server (NTRS)

    Zakharenkova, I. E.; Krankowski, A.; Bilitza, D.; Cherniak, Iu.V.; Shagimuratov, I.I.; Sieradzki, R.

    2013-01-01

    The unusually deep and extended solar minimum of cycle 2324 made it very difficult to predict the solar indices 1 or 2 years into the future. Most of the predictions were proven wrong by the actual observed indices. IRI gets its solar, magnetic, and ionospheric indices from an indices file that is updated twice a year. In recent years, due to the unusual solar minimum, predictions had to be corrected downward with every new indices update. In this paper we analyse how much the uncertainties in the predictability of solar activity indices affect the IRI outcome and how the IRI values calculated with predicted and observed indices compared to the actual measurements.Monthly median values of F2 layer critical frequency (foF2) derived from the ionosonde measurements at the mid-latitude ionospheric station Juliusruh were compared with the International Reference Ionosphere (IRI-2007) model predictions. The analysis found that IRIprovides reliable results that compare well with actual measurements, when the definite (observed and adjusted) indices of solar activityare used, while IRI values based on earlier predictions of these indices noticeably overestimated the measurements during the solar minimum.One of the principal objectives of this paper is to direct attention of IRI users to update their solar activity indices files regularly.Use of an older index file can lead to serious IRI overestimations of F-region electron density during the recent extended solar minimum.

  6. Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar minimum determined by CHAMP satellite

    E-print Network

    Forbes, Jeffrey

    Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar minimum currents, the longitudinal and seasonal variation of the Sq currents are determined through the method in the African/European longitude sector reveals similar amplitudes and seasonal variations, indicating

  7. Galactic cosmic ray radiation hazard in the unusual extended solar minimum between solar cycles 23 and 24

    Microsoft Academic Search

    N. A. Schwadron; A. J. Boyd; K. Kozarev; M. Golightly; H. Spence; L. W. Townsend; M. Owens

    2010-01-01

    Galactic cosmic rays (GCRs) are extremely difficult to shield against and pose one of the most severe long-term hazards for human exploration of space. The recent solar minimum between solar cycles 23 and 24 shows a prolonged period of reduced solar activity and low interplanetary magnetic field strengths. As a result, the modulation of GCRs is very weak, and the

  8. Comprehensive Ionospheric Polar and Auroral Observations for Solar Minimum of Cycle 23/24

    NASA Astrophysics Data System (ADS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig

    Only the incoherent scatter radar (ISR) is able to simultaneously measure full profiles of elec-tron density, ion temperature, and electron temperatures through the E-and F-layers of the terrestrial ionosphere. Historically ISR's have been operated for periods much less than a month. Hence, their measurements do not constitute a continuous sequence from which quiet, disturbed, and storm periods can reliably be discerned. This is particularly true in the auroral and polar regions. During the International Polar Year (IPY) two ISRs achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the IRI with a fiduciary E-and F-region ionosphere descriptions for solar minimum conditions at auroral and polar cap locations. The ionospheric description being electron den-sity, ion temperature, electron temperature, and even molecular ion composition profiles from as low as 90 km extending several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.4° N, 147.5° W where the NSF's new Poker Flat Incoherent Scatter Radar (PFISR) is located. During solar minimum conditions this location is in the auroral region for most of the day and is at mid-latitudes, equatorward of the cusp, for about 4 to 8 hours per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78° N, 16° E where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap often with a noon sector passage through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be demarked between quiet and disturbed. During the IPY year, 1 March 2007 to 29 February 2008, a total of 50 solar wind corotating interaction regions (CIRs) impacted geospace. Each CIR has a one-to-three day geomagnetic disturbance that is observed in the ISR auroral and polar observations. Hence, this data set enables the quiet-background ionosphere to be established as a function of season and local time. This quiet-background ionosphere has the unique attribute that it has self-consistent altitude profiles of the density and the temper-ature. This we believe is a true fiduciary reference for the IRI in a high latitude region, that is otherwise particularly difficult to quantify.

  9. 24/7 Solar Minimum Polar Cap and Auroral Ion Temperature Observations

    NASA Technical Reports Server (NTRS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig; Bilitza, Dieter

    2011-01-01

    During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 N latitude, 212.5 E longitude where the NSF s new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at midlatitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 N latitude, 16.0 E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably with the quiet-background in temperature, both in magnitude and climatology.

  10. High-cadence observations of CME initiation and plasma dynamics in the corona with TESIS on board CORONAS-Photon

    NASA Astrophysics Data System (ADS)

    Bogachev, Sergey; Kuzin, Sergey; Zhitnik, I. A.; Bugaenko, O. I.; Goncharov, A. L.; Ignatyev, A. P.; Krutov, V. V.; Lomkova, V. M.; Mitrofanov, A. V.; Nasonkina, T. P.; Oparin, S. N.; Petzov, A. A.; Shestov, S. V.; Slemzin, V. A.; Soloviev, V. A.; Suhodrev, N. K.; Shergina, T. A.

    The TESIS is an ensemble of space instruments designed in Lebedev Institute of Russian Academy of Sciences for spectroscopic and imaging investigation of the Sun in EUV and soft X-ray spectral range with high spatial, temporal and spectral resolution. From 2009 January, when TESIS was launched onboard the Coronas-Photon satellite, it provided about 200 000 new images and spectra of the Sun, obtained during one of the deepest solar minimum in last century. Because of the wide field of view (4 solar radii) and high sensitivity, TESIS provided high-quality data on the origin and dynamics of eruptive prominences and CMEs in the low and intermediate solar corona. TESIS is also the first EUV instrument which provided high-cadence observations of coronal bright points and solar spicules with temporal resolution of a few seconds. We present first results of TESIS observations and discuss them from a scientific point of view.

  11. On the 27-day Variations of Cosmic Ray Intensity in Recent Solar Minimum 23/24

    E-print Network

    Modzelewska, R

    2015-01-01

    We have studied the 27-day variations and their harmonics of the galactic cosmic ray (GCR) intensity, solar wind velocity, and interplanetary magnetic field (IMF) components in the recent prolonged solar minimum 23 24. The time evolution of the quasi-periodicity in these parameters connected with the Suns rotation reveals that their synodic period is stable and is aprox 26-27 days. This means that the changes in the solar wind speed and IMF are related to the Suns near equatorial regions in considering the differential rotation of the Sun. However, the solar wind parameters observed near the Earths orbit provide only the conditions in the limited local vicinity of the equatorial region in the heliosphere (within in latitude). We also demonstrate that the observed period of the GCR intensity connected with the Suns rotation increased up to aprox 33-36 days in 2009. This means that the process driving the 27-day variations of the GCR intensity takes place not only in the limited local surroundings of the equato...

  12. Daytime ionospheric equatorial vertical drifts during the 2008-2009 extreme solar minimum

    NASA Astrophysics Data System (ADS)

    Rodrigues, F. S.; Smith, J. M.; Milla, M.; Stoneback, R. A.

    2015-02-01

    One of the most interesting observations made by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite mission was the detection of average equatorial ionospheric vertical drifts that largely differed from model predictions. C/NOFS measurements showed, in particular, downward drifts in the afternoon sector, and upward drifts around local midnight hours during the 2008 and 2009 extreme solar minimum. The unexpected behavior of the drifts has important implications for ionospheric modeling and suggests the necessity for a better understanding of the low-latitude electrodynamics. We used ground-based radar measurements to quantify the seasonal and solar flux variability of daytime equatorial drifts at lower altitudes (˜150 km) than those probed by C/NOFS (above ˜400 km). We found that average vertical drifts at 150 km altitude are in good agreement with model predictions of F region drifts and did not show the signatures of an enhanced semidiurnal pattern, as seen by C/NOFS. Comparison of the 150 km echo drifts with model predictions also shows that the increase (decrease) with height of the vertical drifts in the morning (afternoon) hours is a regular feature of the equatorial ionosphere. It occurred in all seasons and solar flux conditions between 2001 and 2011.

  13. 7Be atmospheric concentration at mid latitudes (40°N) during a year of solar minimum

    NASA Astrophysics Data System (ADS)

    Kotsopoulou, E.; Ioannidou, A.

    2012-04-01

    In this paper we present the variation of 7Be concentration in the surface air of Thessaloniki, Greece (40°62'N, 22°95'E) over the year 2009, a year of a deep solar minimum, and, as a consequence, a year of maximum concentration of 7Be in surface air. The mean annual activity concentration of 7Be for the year 2009 was 6.0 mBq m-3. The relative variability of 7Be surface concentration related to the solar cycle was calculated to be deviated by about 20% from maximum to mean. A positive correlation (R = 0.97) was revealed between the activity of 7Be and the temperature T (°C), confirming that the increased rate of vertical transport within the troposphere, especially during warmer months, that make descend air masses enriched in 7Be down to the surface layer. The anticorrelation (R = -0.65) with RH% is due to intense condensation during high relative humidity conditions, which results in increased aerosol particle sizes and as a consequence in higher scavenging rate of aerosols and lower concentration of 7Be in the atmosphere. The influence of precipitation on the 7Be atmospheric concentration variability was approximately 10%, with greater the influence of rainfall events of low precipitation rate e.g. drizzling.

  14. Physics of the weird solar minimum: New observations of the Sun

    NASA Astrophysics Data System (ADS)

    Zita, E.; Smith, C.; Ballou, C.; Friedman, B.; Showalter, C.; Rex, R.; Hurlburt, N.

    2010-10-01

    While solar physicists expected more sunspots, flares, and coronal mass ejections by now, the Sun has defied most predictions by persisting in a relatively quiet state for an unusually long time. Can we tell whether this solar minimum is likely to ease in the next decade, or if it may become a Maunder-type minimum? What evidence is there for mechanisms that might explain the observed delayed and low-amplitude magnetic activity? What effects could decreased solar activity have on Earth's climate? Evergreen undergraduates study the Sun with colleagues who built the new Solar Dynamics Observatory (SDO). Students analyzed flow velocities with respect to magnetic field tilts; analyzed waves of UV light in active regions; developed a software suite to enable the public to engage with solar dynamics; and cataloged movies of solar events for public release. We use data from the high-resolution HINODE satellite and from the new full-disk SDO. Zita studied the solar dynamo, and found that resistivity gradients can drive magnetic advection. We summarize our work and the light it may shed on questions such as those above.

  15. Comparison of Transport Codes, HZETRN, HETC and FLUKA, Using 1977 GCR Solar Minimum Spectra

    NASA Technical Reports Server (NTRS)

    Heinbockel, John H.; Slaba, Tony C.; Tripathi, Ram K.; Blattnig, Steve R.; Norbury, John W.; Badavi, Francis F.; Townsend, Lawrence W.; Handler, Thomas; Gabriel, Tony A.; Pinsky, Lawrence S.; Reddell, Brandon; Aumann, Aric R.

    2009-01-01

    The HZETRN deterministic radiation transport code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events (SPE) on mission planning, astronaut shielding and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC-HEDS and FLUKA, and the deterministic transport code, HZETRN. Each code is used to transport ions from the 1977 solar minimum GCR spectrum impinging upon a 20 g/cm2 Aluminum slab followed by a 30 g/cm2 water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton fluxes, and the forward, backward and total neutron fluxes at various depths in the water slab. Comparisons of the secondary light ion 2H, 3H, 3He and 4He fluxes are also examined.

  16. Corona physics and diagnostics

    Microsoft Academic Search

    Reidar Svein Sigmond

    1996-01-01

    The criterions for oscillations in DC-fed coronas are discussed, both for the well-understood negative Trichel pulse coronas and for the unexplained positive glow pulse coronas. Trichel-like pulses occur also in non-electron-attaching gases, due to the external circuit impedance, and this lowers the sensitivity of Trichel coronas as detectors for electronegative gas traces. Pulse excitation of positive glow coronas in argon

  17. Galactic cosmic ray radiation hazard in the unusual extended solar minimum between solar cycles 23 and 24

    NASA Astrophysics Data System (ADS)

    Schwadron, N. A.; Boyd, A. J.; Kozarev, K.; Golightly, M.; Spence, H.; Townsend, L. W.; Owens, M.

    2010-05-01

    Galactic cosmic rays (GCRs) are extremely difficult to shield against and pose one of the most severe long-term hazards for human exploration of space. The recent solar minimum between solar cycles 23 and 24 shows a prolonged period of reduced solar activity and low interplanetary magnetic field strengths. As a result, the modulation of GCRs is very weak, and the fluxes of GCRs are near their highest levels in the last 25 years in the fall of 2009. Here we explore the dose rates of GCRs in the current prolonged solar minimum and make predictions for the Lunar Reconnaissance Orbiter (LRO) Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which is now measuring GCRs in the lunar environment. Our results confirm the weak modulation of GCRs leading to the largest dose rates seen in the last 25 years over a prolonged period of little solar activity.

  18. Gyro-resonant scattering of radiation belt electrons during the solar minimum by fast magnetosonic waves

    NASA Astrophysics Data System (ADS)

    Shprits, Yuri Y.; Runov, Andrei; Ni, Binbin

    2013-02-01

    In the current study, we perform statistical analysis of the magnetosonic (MS) waves (also often referred to as extremely low frequency (ELF) equatorial noise) in the range between the ion cyclotron frequency and the lower hybrid resonance frequency within 10° of the magnetic equator. Observations were made between 2 and 9 RE using THEMIS Filter Bank (FBK) data. ELF waves with spectral power exceeding 10-6 nT2/Hz are registered in ~3% of all samples in the inner magnetosphere. The survey has shown that, during the solar minimum, the average amplitude of equatorial ELF waves is less than 0.025 nT. Interpreting ELF events as MS waves, we have evaluated the corresponding wave-induced resonant scattering coefficients of radiation belt energetic electrons. We also study the effect of heavy ions on the scattering rates. The analysis reveals that the scattering by magnetosonic waves for various plasma compositions during geomagnetically quiet times is by up to two orders of magnitude slower than was previously reported and cannot significantly contribute to the long-term dynamics of the radiation belts. Computed electron scattering rates by magnetosonic waves extends to higher ?eq when the fraction of H+ in the plasma decreases, while the range of pitch angles for which resonance occurs remains relatively insensitive to the plasma composition. While inclusion of multi-ion species into the wave dispersion relation produces noticeable changes in bounce-averaged scattering rates, the average rates are still significantly below typical scattering rates of chorus or hiss waves.

  19. Possible impacts of a descent into a Grand Solar Minimum on extratropical regional surface climate

    NASA Astrophysics Data System (ADS)

    Maycock, A. C.; Ineson, S.; Gray, L. J.; Scaife, A. A.; Lockwood, M. M.

    2012-12-01

    The Sun's output varies on a number of characteristic timescales, the most well-known of which is the approximately 11-year solar cycle. It has been shown that the Sun also exhibits cycles with a period of ~200 years, so-called Grand Solar Cycles. Reconstructions indicate that levels of solar activity have been relatively high for the past ~70 years, and it has been suggested that the Sun might be expected to evolve towards a state of lower output; however, the timescale and extent of such a 'Grand Solar Minimum' event is highly uncertain. This study presents sensitivity experiments with a state-of-the-art climate model to investigate the impact of reaching very low levels of solar output, similar to those thought to have occurred during the Maunder Minimum, by the middle of the 21st century. We investigate the effect of uncertainties in spectral solar irradiance by using both the semi-empirical model of Lean et al., which gives a relatively modest change in the ultraviolet (UV) spectral region and is commonly used to represent solar variability in climate models, as well as the recent measurements from the SORCE satellite, which suggest a much larger change in the UV across the solar cycle for the period 2004-07. Under the assumption of there being a large change in the UV derived from a linear extrapolation of the SORCE data, it is shown that a period of very low solar activity would be associated with a more negative North Atlantic Oscillation index. This signature in the large-scale circulation is associated with changes in regional surface climate, including cooler temperatures across the UK and western Europe. In the experiment which assumes a smaller change in UV irradiance, the extratropical circulation responses in the stratosphere and troposphere are found to be of a consistent sign but smaller in magnitude. This highlights the importance of one possible mechanism for solar-climate interactions, namely the impact of tropical upper stratospheric heating on extratropical stratospheric winds and the annular modes. As expected, changes in global-mean surface temperature are small in both sets of experiments, meaning that such a change in solar activity would have little effect on any greenhouse gas induced global warming.

  20. Preliminary Results Of the 2007 Flight of the Solar Bolometric Imager at Solar Minimum

    NASA Astrophysics Data System (ADS)

    Bernasconi, P. N.; Foukal, P. V.; Eaton, H. H.; Noble, M.

    2008-05-01

    On September 13 2007, the Solar Bolometric Imager (SBI) successfully observed the Sun for several hours while suspended from a balloon in the stratosphere above New Mexico. The SBI represents a totally new approach in finding the sources of the solar irradiance variation. The SBI detector is an array of 320x240 thermal IR elements whose spectral absorptance has been extended and flattened by a deposited layer of gold-black. The telescope is a 30-cm Dall-Kirkham with uncoated primary and secondary Pyrex mirrors. The combination of telescope and bolometric array provide an image of the Sun with a constant spectral response between ~ 280 and 2600 nm, over a field of view of 960 x 720 arcsec with a pixel size of 3 arcsec. This is the second successful flight of SBI, following a successful one on September 2003 which produced the first measurements in broad band of the center-to-limb variation of bolometric facular contrast (a flight attempt from Antarctica in 2006 was aborted). This latest flight provided bolometric (integrated light) maps of the solar photosphere during a time of minimum of solar activity. The SBI imagery will enable us to evaluate the photometric contribution of weak magnetic structures (e.g. network) more accurately than has been achievable with spectrally selective imaging over restricted wavebands. It will also enable us to investigate the presence, if any, of other thermal structures unrelated to magnetic activity, such as e.g. giant cells and pole-to-equator temperature gradients. During the 16 hour flight the SBI gathered several thousand bolometric images that are now being processed to produce full-disk maps of spatial variation in total solar output at solar minimum. The SBI flight is also providing important engineering data to validate the space worthiness of the novel gold-blackened thermal array detectors. In this paper we will briefly describe the characteristics of the SBI, its in-flight performance, and we will present the first results of the analysis of the bolometric images.

  1. Space weather effects on the low latitude D-region ionosphere during solar minimum

    NASA Astrophysics Data System (ADS)

    Kumar, Abhikesh; Kumar, Sushil

    2014-12-01

    The effects of the solar flares and the geomagnetic storms (disturbance storm time ( Dst) < -50 nT) during December 2006 to 2008, a period during the unprecedented solar minimum of solar cycles 23 and 24, have been examined on sub-ionospheric very low frequency (VLF) signals from NWC (19.8 kHz), NPM (21.4 kHz), VTX (18.2 kHz), and NLK (24.8 kHz) transmitters monitored at Suva (18.2° S, 178.4° E), Fiji. Apart from the higher class solar flares (C to X), a solar flare of class B8.5 also produced enhancements both on the amplitude and phase. The amplitude enhancements in NLK, NPM, and NWC signals as a function of peak solar flare X-ray flux in decibel (dB; relative to 1 ?W/m2) shows that the relationship curve is steeper and quite linear between the flare power levels of 0 to 15 dB; below 0 dB, the curve gets less steep and flattens towards -5 dB flare power level, while it also gets less steep above 15 dB and almost flattens above 20 dB. In general, the level of amplitude enhancement for NLK signal is higher than that for NPM and NWC signals for all solar flares. The enhancement in the amplitude and phase of VLF signals by solar flares is due to the increase in the D-region electron density by the solar flare-produced extra ionization. The modeling of VLF perturbations produced by B8.5 and C1.5 classes of solar flares on 29 January 2007 using LWPC (Long Wave Propagation Capability) V2.1 codes show that reflection height ( H') was reduced by 0.6 and 1.2 km and the exponential sharpness factor ( ?) was raised by 0.010 and 0.005 km-1, respectively. Out of seven storms with Dst < -50 nT, only the intense storm of 14 to 16 December 2006 with a minimum Dst of -145 nT has shown a clear reduction in the signal strength of NWC and NPM sub-ionospheric signals due to storm-induced reduction in the D-region electron density.

  2. Influence of projection effects on the observed differential rotation rate in the UV corona

    PubMed Central

    Mancuso, Salvatore; Giordano, Silvio

    2012-01-01

    Following previous investigations by Giordano and Mancuso [1] and Mancuso and Giordano [2,3] on the differential rotation of the solar corona as obtained through the analysis of the intensity time series of the O VI 1032 Å spectral line observed by the UVCS/SOHO telescope during solar cycle 23, we analysed the possible influence of projection effects of extended coronal structures on the observed differential rotation rate in the ultraviolet corona. Through a simple geometrical model, we found that, especially at higher latitudes, the differential rotation may be less rigid than observed, since features at higher latitudes could be actually linked to much lower coronal structures due to projection effects. At solar maximum, the latitudinal rigidity of the UV corona, with respect to the differential rotating photosphere, has thus to be considered as an upper limit of the possible rigidity. At solar minimum and near the equatorial region throughout the solar cycle, projection effects are negligible. PMID:25685430

  3. Influence of projection effects on the observed differential rotation rate in the UV corona.

    PubMed

    Mancuso, Salvatore; Giordano, Silvio

    2013-05-01

    Following previous investigations by Giordano and Mancuso [1] and Mancuso and Giordano [2,3] on the differential rotation of the solar corona as obtained through the analysis of the intensity time series of the O VI 1032 Å spectral line observed by the UVCS/SOHO telescope during solar cycle 23, we analysed the possible influence of projection effects of extended coronal structures on the observed differential rotation rate in the ultraviolet corona. Through a simple geometrical model, we found that, especially at higher latitudes, the differential rotation may be less rigid than observed, since features at higher latitudes could be actually linked to much lower coronal structures due to projection effects. At solar maximum, the latitudinal rigidity of the UV corona, with respect to the differential rotating photosphere, has thus to be considered as an upper limit of the possible rigidity. At solar minimum and near the equatorial region throughout the solar cycle, projection effects are negligible. PMID:25685430

  4. Ultrasonic corona sensor study

    NASA Technical Reports Server (NTRS)

    Harrold, R. T.

    1976-01-01

    The overall objective of this program is to determine the feasibility of using ultrasonic (above 20 kHz) corona detection techniques to detect low order (non-arcing) coronas in varying degrees of vacuum within large high vacuum test chambers, and to design, fabricate, and deliver a prototype ultrasonic corona sensor.

  5. The Peculiar Solar Minimum 23/24 Revealed by the Microwave Butterfly Diagram

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Natchimuthuk; Yashiro, Seiji; Makela, Pertti; Shibasaki, Kiyoto; Hathaway, David

    2010-01-01

    The diminished polar magnetic field strength during the minimum between cycles 23 and 24 is also reflected in the thermal radio emission originating from the polar chromosphere. During solar minima, the polar corona has extended coronal holes containing intense unipolar flux. In microwave images, the coronal holes appear bright, with a brightness enhancement of 500 to 2000 K with respect to the quiet Sun. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is approx.10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radioheliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approx.250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes..

  6. The Solar Corona

    NSDL National Science Digital Library

    David Hathaway

    This site describes the corona of the sun from three different points of view. In the first case, the white-light corona is the sight that is visible during total eclipses of the sun as a pearly white crown surrounding the sun and displays a variety of features including streamers, plumes, and loops. The emission line corona is explained on the basis of the extreme heat of the corona and the X-ray corona is described in terms of past and present research projects designed to study it. The site also contains an image for each of the three parts.

  7. Corona physics and diagnostics

    NASA Astrophysics Data System (ADS)

    Sigmond, Reidar Svein

    1996-03-01

    The criterions for oscillations in DC-fed coronas are discussed, both for the well-understood negative Trichel pulse coronas and for the unexplained positive glow pulse coronas. Trichel-like pulses occur also in non-electron-attaching gases, due to the external circuit impedance, and this lowers the sensitivity of Trichel coronas as detectors for electronegative gas traces. Pulse excitation of positive glow coronas in argon with added trace gases show that the corona stability and resonance frequency strongly depend on the trace gas type and concentration, but the physics involved is unknown. Finally, it is shown that the low-current U(I) curve of relaxation-pulsed coronas always must have a negative slope, equal to the negative of the series resistance.

  8. Corona physics and diagnostics

    SciTech Connect

    Sigmond, R.S. [The Electron and Ion Physics Research Group, Physics Department, The Norwegian Institute of Technology, N-7034 Trondheim (Norway)

    1996-03-01

    The criterions for oscillations in DC-fed coronas are discussed, both for the well-understood negative Trichel pulse coronas and for the unexplained positive glow pulse coronas. Trichel-like pulses occur also in non-electron-attaching gases, due to the external circuit impedance, and this lowers the sensitivity of Trichel coronas as detectors for electronegative gas traces. Pulse excitation of positive glow coronas in argon with added trace gases show that the corona stability and resonance frequency strongly depend on the trace gas type and concentration, but the physics involved is unknown. Finally, it is shown that the low-current U(I) curve of relaxation-pulsed coronas always must have a negative slope, equal to the negative of the series resistance. {copyright} {ital 1996 American Institute of Physics.}

  9. A theoretical study of the high-latitude winter F region at solar minimum for low magnetic activity

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Raitt, W. J.; Schunk, R. W.

    1981-01-01

    A simple plasma convection model is combined with an ionospheric-atmospheric composition model in order to study the high-latitude winter F region at the solar minimum for low magnetic activity. The high latitude ionospheric features, such as the main trough, the ionization hole, the tongue of ionization, the aurorally produced ionization peaks, and the universal time effects are a natural consequence of the competition between the various chemical and transport processes known to be operating in the high-latitude ionosphere. In the polar hole, the F region peak electron density is below 300 km, and the dominant process at 300 km for NO(+) ions is diffusion.

  10. Measurement of Cosmic-Ray Antiproton Spectrum at Solar Minimum with a Long-Duration Balloon Flight in Antarctica

    NASA Technical Reports Server (NTRS)

    Abe, K.; Fuke, H.; Haino, S.; Hams, T.; Hasegawa, M.; Horikoshi, A.; Kim, K. C.; Kusumoto, A.; Lee, M. H.; Makida, Y.; Matsuda, S.; Matsukawa, Y.; Mitchell, J. W.; Nishimura, J.; Nozaki, M.; Orito, R.; Ormes, J. F.; Sakai, K.; Sasaki, M.; Seo, E. S.; Shinoda, R.; Streitmatter, R. E.; Suzuki, J.; Tanaka, K.; Thakur, N.

    2011-01-01

    The energy spectrum of cosmic-ray antiprotons (p(raised bar)'s) collected by the BESS-Polar II instrument during a long-duration flight over Antarctica in the solar minimum period of December 2007 through January 2008. The p(raised bar) spectrum measured by BESS-Polar II shows good consistency with secondary p(raised bar) calculations. Cosmologically primary p(raised bar)'s have been searched for by comparing the observed and calculated p(raised bar) spectra. The BESSPolar II result shows no evidence of primary p(raised bar)'s originating from the evaporation of PBH.

  11. Measurement of cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight in Antarctica

    E-print Network

    Abe, K; Haino, S; Hams, T; Hasegawa, M; Horikoshi, A; Kim, K C; Kusumoto, A; Lee, M H; Makida, Y; Matsuda, S; Matsukawa, Y; Mitchell, J W; Nishimura, J; Nozaki, M; Orito, R; Ormes, J F; Sakai, K; Sasaki, M; Seo, E S; Shinoda, R; Streitmatter, R E; Suzuki, J; Tanaka, K; Thakur, N; Yamagami, T; Yamamoto, A; Yoshida, T; Yoshimura, K

    2011-01-01

    The energy spectrum of cosmic-ray antiprotons has been measured in the range 0.17 to 3.5 GeV, based on 7886 antiprotons collected by the BESS-Polar II instrument during a long-duration flight over Antarctica in the solar minimum period of December 2007 through January 2008. The antiproton spectrum measured by BESS-Polar II shows good consistency with secondary antiproton calculations. Cosmologically primary antiprotons have been searched for by comparing the observed and calculated antiproton spectra. The BESS-Polar II result shows no evidence of primary antiprotons originating from the evaporation of PBH.

  12. Measurement of the Cosmic-Ray Antiproton Spectrum at Solar Minimum with a Long-Duration Balloon Flight over Antarctica

    NASA Technical Reports Server (NTRS)

    Abe, K.; Fuke, H.; Haino, S.; Hams, T.; Hasegawa, M.; Horikoshi, A.; Kim, K. C.; Kusumoto, A.; Lee, M. H.; Makida, Y.; Matsuda, S.; Matsukawa, Y.; Mitchell, J. W.; Nishimura, J.; Nozaki, M.; Orito, R.; Ormes, J. F.; Sakai, K.; Sasaki, M.; Seo, E. S.; Shinoda, R.; Streitmatter, R. E.; Suzuki, J.; Tanaka, K.; Thakur, N.

    2012-01-01

    The energy spectrum of cosmic-ray antiprotons (p-bar's) from 0.17 to 3.5 GeV has been measured using 7886 p-bar's detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary p-bar calculations. Cosmologically primary p-bar's have been investigated by comparing measured and calculated p-bar spectra. BESS-Polar II data.show no evidence of primary p-bar's from the evaporation of primordial black holes.

  13. STRUCTURE AND DYNAMICS OF THE 2009 JULY 22 ECLIPSE WHITE-LIGHT CORONA

    SciTech Connect

    Pasachoff, J. M.; Babcock, B. A. [Williams College-Hopkins Observatory, Williamstown, MA 01267 (United States); Rusin, V.; Saniga, M. [Astronomical Institute, Slovak Academy of Sciences, 059 60 Tatranska Lomnica (Slovakia); Druckmuellerova, H., E-mail: eclipse@williams.edu, E-mail: bryce.a.babcock@williams.edu, E-mail: vrusin@ta3.sk, E-mail: msaniga@ta3.sk, E-mail: hanadruck@seznam.cz [Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, 616 69 Brno (Czech Republic)

    2011-11-20

    The white-light corona (WLC) during the total solar eclipse of 2009 July 22 was observed by several teams in the Moon's shadow stretching from India and China across the Pacific Ocean with its many isolated islands. We present a comparison of the WLC as observed by eclipse teams located in China (Shanghai region) and on the Enewetak Atoll in the Marshall Islands, with observations taken 112 minutes apart, combined with near-simultaneous space observations. The eclipse was observed at the beginning of solar cycle 24, during a deep solar minimum (officially estimated as 2008 December according to the smoothed sunspot number, but very extended). The solar corona shows several different types of features (coronal holes, polar rays, helmet streamers, faint loops, voids, etc.), though it was extremely sparse in streamers as shown from Large-Angle Spectroscopic Coronagraph data. No large-scale dynamical phenomena were seen when comparing the observations from the two sites, confirming that the corona was quiescent. We measure a Ludendorff flattening coefficient of 0.238, typical of solar minimum.

  14. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, Heather A.; Comfort, Richard H.; Craven, Paul D.; Chandler, Michael O.; Moore, Thomas E.

    2000-01-01

    We correlate solar wind and IMF properties with the properties of O(+) and H(+) in the polar cap in early 1996 during solar minimum conditions at altitudes between 5.5 and 8.9 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the POLAR satellite. Throughout the high altitude polar cap, we observe H(+) to be more abundant than O(+). H(+) is a significant fraction of both the ionosphere and the solar wind, and O(+) is not a significant species in the solar wind. O(+) is the major species in the ionosphere so the faction of O(+) present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. For these reasons, 0+ is of primary interest in this study. We observe O(+) to be most abundant at lower latitudes when the solar wind speed is low (and low Kp), and at higher solar wind speeds (and high Kp) O(+) is observed across most of the polar cap. We also find that O(+) density and parallel flux are well organized by solar wind dynamic pressure; they both increase with solar wind dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, but H(+) density and parallel flux have some negative correlation with IMF By, and some positive correlation with VswBIMF. In this solar minimum data set, H(+) is dominant so that contributions of this plasma to the plasma sheet would have a very low O(+) to H(+) ratio.

  15. Comparison of observations and multi-fluid models of streamers at solar minimum

    NASA Astrophysics Data System (ADS)

    Ofman, Leon; Abbo, Lucia; Giordano, Silvio; Kramar, Maxim

    We present the results comparison between the slow solar wind plasma parameters obtained in the extended corona by the UV spectroscopic data from the Ultraviolet Coronagraph Spectrom-eter (UVCS) on-board SOHO and STEREO during the past minima of solar activity (CR1913; and CR2066) and the results of a time-dependent 2.5D three-fluid MHD model of the coronal streamer belt. The previous three-fluid (e, p, and O5+ or He++ ) streamer model has been improved by considering real solar magnetic field obtained by Wilcox Solar Observatory as boundary condition, and PFSS model as initial state of the magnetic configuration. This is the first study that incorporates real magnetic field in the three-fluid model. The model was run until fully self consistent streamer was formed in the quasi-steady state. The electron density reconstructed from STEREO Cor1 observations was compared to the results of the three-fluid model to validate the model. The plasma parameters from the multi-fluid model were used to compute the expected UV observables from HI Ly-? and OVI 1032 spectral lines and the results were compared in details with the UVCS measurements.

  16. DECLINE AND RECOVERY OF THE INTERPLANETARY MAGNETIC FIELD DURING THE PROTRACTED SOLAR MINIMUM

    SciTech Connect

    Smith, Charles W.; Schwadron, Nathan A. [Physics Department, Space Science Center, University of New Hampshire, Durham, New Hampshire (United States); DeForest, Craig E., E-mail: Charles.Smith@unh.edu, E-mail: N.Schwadron@unh.edu, E-mail: DeForest@Boulder.SwRI.edu [Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, Colorado (United States)

    2013-09-20

    The interplanetary magnetic field (IMF) is determined by the amount of solar magnetic flux that passes through the top of the solar corona into the heliosphere, and by the dynamical evolution of that flux. Recently, it has been argued that the total flux of the IMF evolves over the solar cycle due to a combination of flux that extends well outside of 1 AU and is associated with the solar wind, and additionally, transient flux associated with coronal mass ejections (CMEs). In addition to the CME eruption rate, there are three fundamental processes involving conversion of magnetic flux (from transient to wind-associated), disconnection, and interchange reconnection that control the levels of each form of magnetic flux in the interplanetary medium. This is distinct from some earlier models in which the wind-associated component remains steady across the solar cycle. We apply the model of Schwadron et al. that quantifies the sources, interchange, and losses of magnetic flux to 50 yr of interplanetary data as represented by the Omni2 data set using the sunspot number as a proxy for the CME eruption rate. We do justify the use of that proxy substitution. We find very good agreement between the predicted and observed interplanetary magnetic flux. In the absence of sufficient CME eruptions, the IMF falls on the timescale of ?6 yr. A key result is that rising toroidal flux resulting from CME eruption predates the increase in wind-associated IMF.

  17. The Sun's X-ray Emission During the Recent Solar Minimum

    NASA Astrophysics Data System (ADS)

    Sylwester, Janusz; Kowalinski, Mirek; Gburek, Szymon; Siarkowski, Marek; Kuzin, Sergey; Farnik, Frantisek; Reale, Fabio; Phillips, Kenneth J. H.

    2010-02-01

    The Sun recently underwent a period of a remarkable lack of major activity such as large flares and sunspots, without equal since the advent of the space age a half century ago. A widely used measure of solar activity is the amount of solar soft X-ray emission, but until recently this has been below the threshold of the X-ray-monitoring Geostationary Operational Environmental Satellites (GOES). There is thus an urgent need for more sensitive instrumentation to record solar X-ray emission in this range. Anticipating this need, a highly sensitive spectrophotometer called Solar Photometer in X-rays (SphinX) was included in the solar telescope/spectrometer TESIS instrument package on the third spacecraft in Russia's Complex Orbital Observations Near-Earth of Activity of the Sun (CORONAS-PHOTON) program, launched 30 January 2009 into a near-polar orbit. SphinX measures X-rays in a band similar to the GOES longer-wavelength channel.

  18. Polar Chromospheric Signatures of the Subdued Cycle 23/24 Solar Minimum

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Yashiro, S.; Makela, P.; Shibasaki, K.; Hathaway, D.

    2010-01-01

    Coronal holes appear brighter than the quiet Sun in microwave images, with a brightness enhancement of 500 to 2000 K. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is about 10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radioheliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approximately 250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes.

  19. Chromospheric Signatures of the Subdued Cycle 23/24 Solar Minimum in Microwaves

    NASA Technical Reports Server (NTRS)

    Yashiro, S.; Makela, P.; Shibasaki, K.; Hathaway, D.

    2011-01-01

    Coronal holes appear brighter than the quiet Sun in microwave images, with a brightness enhancement of 500 to 2000 K. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is about 10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radio-heliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approx.250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes.

  20. Corona discharge processes

    Microsoft Academic Search

    J.-S. Chang; P. A. Lawless; T. Yamamoto

    1991-01-01

    Applications of corona discharge induced plasmas and unipolar ions are reviewed. Corona process applications emphasize one of two aspects of the discharge: the ions produced or the energetic electrons producing the plasma. The ion identities depend on the polarity of the discharge and the characteristics of the gas mixture, specifically on the electron attaching species. The electron energies depend on

  1. Spectra of coronae

    Microsoft Academic Search

    Cam McLeman; Erin McNicholas

    2011-01-01

    We introduce a new invariant, the coronal of a graph, and use it to compute the spectrum of the corona G?H of two graphs G and H. In particular, we show that this spectrum is completely determined by the spectra of G and H and the coronal of H. Previous work has computed the spectrum of a corona only in

  2. Simulating coronas in color.

    PubMed

    Gedzelman, Stanley D; Lock, James A

    2003-01-20

    Coronas are simulated in color by use of the Mie scattering theory of light by small droplets through clouds of finite optical thickness embedded in a Rayleigh scattering atmosphere. The primary factors that affect color, visibility, and number of rings of coronas are droplet size, width of the size distribution, and cloud optical thickness. The color sequence of coronas and iridescence varies when the droplet radius is smaller than approximately 6-microm. As radius increases to approximately 3.5 microm, new color bands appear at the center of the corona and fade as they move outward. As the radius continues to increase to approximately 6 microm, successively more inner rings become fixed in the manner described by classical diffraction theory, while outer rings continue their outward migration. Wave clouds or rippled cloud segments produce the brightest and most vivid multiple ringed coronas and iridescence because their integrated dropsize distributions along sunbeams are much narrower than in convective or stratiform clouds. The visibility of coronas and the appearance of the background sky vary with cloud optical depth tau. First the corona becomes visible as a white aureole in a blue sky when tau approximately 0.001. Color purity then rapidly increases to an almost flat maximum in the range 0.05 < or = tau < or = 0.5 and then decreases, so coronas are almost completely washed out by a bright gray background when tau > or = 4. PMID:12570272

  3. The annual asymmetry in the F2 layer during deep solar minimum (2008-2009): December anomaly

    NASA Astrophysics Data System (ADS)

    Mikhailov, A. V.; Perrone, L.

    2015-02-01

    Annual January/July midlatitude daytime asymmetry in monthly median NmF2 and model thermospheric parameters has been considered during deep solar minimum, (2008-2009), when solar and geomagnetic activities were at the lowest level, to analyze the background effect due to the Sun-Earth minimum distance, perihelion, in the vicinity of the December solstice. Averaged over 10 midlatitude station pairs, the NmF2 asymmetry was found to be ?1.23, while the average asymmetry for the annual component in NmF2 variations is ?1.17. Annual asymmetry in monthly median neutral composition and temperature predicted by Mass Spectrometer Incoherent Scatter 86 (MSIS86) and MSISE00 thermospheric models along with the 7% increase in solar EUV flux in the vicinity of the December solstice is sufficient to explain the observed annual asymmetry in NmF2. A hierarchy of aeronomic parameters responsible for the observed asymmetry in NmF2 has been established: the main contributor is atomic oxygen—about 50% of the total effect, [N2] contributes around 35% strongly compensating the [O] contribution, and solar EUV and Tn provide <10% each. The zonal mean annual asymmetry in MSIS86 atomic oxygen column density was shown to be 1.18 at low and middle latitudes, and this is close to the estimated asymmetry for the annual component in NmF2 variations. The earlier proposed mechanism of the December anomaly is considered as a plausible one to explain the 1.18 January/July asymmetry in the atomic oxygen variations and consequently the NmF2 annual daytime asymmetry at middle latitudes under the deep solar minimum.

  4. Westward traveling planetary wave events in the lower thermosphere during solar minimum conditions simulated by SD-WACCM-X

    NASA Astrophysics Data System (ADS)

    Sassi, Fabrizio; Liu, Han-Li

    2014-11-01

    We present numerical simulations with the Whole Atmosphere Community Climate Model, eXtended version (WACCM-X), whose dynamics is constrained by atmospheric specifications during recent and historical solar minimum conditions. The focus of this study is to describe how various dynamical conditions of boreal winter affect the dynamical behavior of the lower thermosphere (90-150 km). The model simulations are carried out during solar minimum conditions and the results shown here discuss the period January 1-March 30 for five years (1995, 1996, 2008, 2009, and 2010). These years were selected because they include boreal winters without stratospheric warming (1995 and 1996), with modest or normal stratospheric warming (2008 and 2010), and with a large and persistent stratospheric warming (2009). The ultimate goal of this study is to encapsulate the statistically significant dynamical behavior due to westward propagating, planetary-scale waves (wavenumber 1 and wavenumber 2) in the lower thermosphere that are associated with different stratospheric conditions. To this end we show that the westward zonal acceleration above about 80 km is by and large described by traveling waves with periods between 2 and 10 days. We show that the momentum carried by these waves is unlikely to affect directly the momentum budget of the extra-tropical lower thermosphere, where instead gravity-wave drag figures prominently. However, at the times leading to and following large stratospheric disturbances, we show prominent meridional propagation of wave activity from the mid-latitudes toward the tropics. In combination with strong eastward meridional wind shear, our results provide further evidence that such equatorward propagation of momentum in the lower thermosphere might influence the amplitude of equatorially trapped tides.

  5. Corona of Magnetars

    E-print Network

    Andrei M. Beloborodov; Christopher Thompson

    2006-08-15

    We develop a theoretical model that explains the formation of hot coronae around strongly magnetized neutron stars -- magnetars. The starquakes of a magnetar shear its external magnetic field, which becomes non-potential and is threaded by an electric current. Once twisted, the magnetosphere cannot untwist immediately because of its self-induction. The self-induction electric field lifts particles from the stellar surface, accelerates them, and initiates avalanches of pair creation in the magnetosphere. The created plasma corona maintains the electric current demanded by curl(B) and regulates the self-induction e.m.f. by screening. This corona persists in dynamic equilibrium: it is continually lost to the stellar surface on the light-crossing time of 10^{-4} s and replenished with new particles. In essence, the twisted magnetosphere acts as an accelerator that converts the toroidal field energy to particle kinetic energy. Using a direct numerical experiment, we show that the corona self-organizes quickly (on a millisecond timescale) into a quasi-steady state, with voltage ~1 GeV along the magnetic lines. The heating rate of the corona is ~10^{36} erg/s, in agreement with the observed persistent, high-energy output of magnetars. We deduce that a static twist that is suddenly implanted into the magnetosphere will decay on a timescale of 1-10 yrs. The particles accelerated in the corona impact the solid crust, knock out protons, and regulate the column density of the hydrostatic atmosphere of the star. The transition layer between the atmosphere and the corona is the likely source of the observed 100-keV emission from magnetars. The corona emits curvature radiation and can supply the observed IR-optical luminosity. (Abridged)

  6. The Solar Corona at the 2015 Total Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Pasachoff, Jay M.; Carter, Allison L.

    2015-04-01

    We report on our successful observations of the solar corona at the 20 March 2015 total solar eclipse from our site at a latitude of about 78° on the Svalbard archipelago, and related observations by colleagues aloft. Our equipment included cameras for imaging at a variety of scales for use in making high-contrast composites, as reported our Astrophysical Journal article (2015) about our 2012 total solar eclipse observations and similar articles about the corona and changes in it at previous total eclipses. Our Svalbard equipment also included a spectrograph, with which we continued our monitoring of the ratio of the Fe XIV and Fe X coronal lines, which has recently been >1 with the solar maximum, a reversal from <1 at earlier eclipses closer to the last solar minimum. Our 2013 observations from Gabon showed two coronal mass ejections and an erupting prominence; the 2015 eclipse showed an erupting prominence and some unusual coronal structure in an overall coronal shape typical of solar maximum. We use our ground-based eclipse observations to fill the gap in imaging between the SDO and SWAP (17.4 nm) EUV observations on the solar disk and the inner location of the LASCO C2 occultation disk, with STEREO observations providing the possibility of three-dimensional interpretations. Our expedition was supported by a grant (9616-14) from the Committee for Research and Exploration of the National Geographic Society.

  7. Change in the pulse regime of negative corona in air due to a small adjunct of SF6

    Microsoft Academic Search

    M. F. Frechette; S. Kamel; R. Bartnikas; R. Y. Larocque

    1996-01-01

    Corona discharge studies were continued concerning the effect of small amounts of SF6 in air. Further observations made on sequences of pulses are reported. Analysis made on each pulse sequence have unraveled distinct repetitive features by the pulse regimes. For air, where the distribution of the pulse amplitudes of the Trichel pulse train is normal in form and the variation

  8. Solar origins of solar wind properties during the cycle 23 solar minimum and rising phase of cycle 24.

    PubMed

    Luhmann, Janet G; Petrie, Gordon; Riley, Pete

    2013-05-01

    The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is 'typical' solar wind, even when the Sun is relatively inactive. PMID:25685422

  9. Solar origins of solar wind properties during the cycle 23 solar minimum and rising phase of cycle 24

    PubMed Central

    Luhmann, Janet G.; Petrie, Gordon; Riley, Pete

    2012-01-01

    The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is ‘typical’ solar wind, even when the Sun is relatively inactive. PMID:25685422

  10. Current Sheets in the Corona and the Complexity of Slow Wind

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro

    2010-01-01

    The origin of the slow solar wind has long been one of the most important problems in solar/heliospheric physics. Two observational constraints make this problem especially challenging. First, the slow wind has the composition of the closed-field corona, unlike the fast wind that originates on open field lines. Second, the slow wind has substantial angular extent, of order 30 degrees, which is much larger than the widths observed for streamer stalks or the widths expected theoretically for a dynamic heliospheric current sheet. We propose that the slow wind originates from an intricate network of narrow (possibly singular) open-field corridors that emanate from the polar coronal hole regions. Using topological arguments, we show that these corridors must be ubiquitous in the solar corona. The total solar eclipse in August 2008, near the lowest point of cycle 23 affords an ideal opportunity to test this theory by using the ultra-high resolution Predictive Science's (PSI) eclipse model for the corona and wind. Analysis of the PSI eclipse model demonstrates that the extent and scales of the open-field corridors can account for both the angular width of the slow wind and its closed-field composition. We discuss the implications of our slow wind theory for the structure of the corona and heliosphere at solar minimum and describe further observational and theoretical tests.

  11. Modeling the Climatology of Equatorial Plasma Bubbles at Solar Minimum Using Plasma Drifts Observed by C/NOFS

    NASA Astrophysics Data System (ADS)

    Retterer, J. M.; Su, Y.; Gentile, L. C.; de La Beaujardiere, O.; Stoneback, R. A.; Pfaff, R. F.

    2010-12-01

    The goal of the C/NOFS (Communication and Navigation Outage Forecast System) project is to further our understanding of the processes in the low-latitude ionosphere that lead to radio scintillation that can interfere with operational systems. Because the height of the F-layer of the ionospheric plasma at night largely controls whether scintillation occurs, the vertical plasma drift is a key parameter among the several quantities the C/NOFS satellite was instrumented to measure in predicting whether scintillation occurs or not. Based on the operation of the C/NOFS IVM Ion Driftmeter and VEFI Electric Field Instrument over the two years since its launch, a climatological model of the vertical plasma drift has been obtained using long-term averages of the measurements. These drifts have been used in PBMOD, the first-principles model of the low-latitude ionosphere, bubble formation, and scintillation developed for the C/NOFS program, to see whether these drifts are in accord with observations of these phenomena. The DMSP satellites, in circular near-polar orbits around 840 km altitude, occasionally observe depletions in plasma density when they cross the geomagnetic equator in the evening and dawn sectors. Statistics for the frequency of observation of these depletions have been collected over the period of the C/NOFS mission. Recall that this period was a remarkably low and extended solar minimum, and the pattern of scintillation occurrence then is notably different from the standard paradigm of post-sunset occurrence. We will present maps of the frequency of occurrence of depletions, calculated with the models using the C/NOFS drift climatology, as a function of season and longitude, and compare the results with DMSP and other observations.

  12. Relationship between vertical ExB drift and F2-layer characteristics in the equatorial ionosphere at solar minimum conditions

    NASA Astrophysics Data System (ADS)

    Oyekola, Oyedemi S.

    2012-07-01

    Equatorial and low-latitude electrodynamics plays a dominant role in determining the structure and dynamics of the equatorial and low-latitude ionospheric F-region. Thus, they constitute essential input parameters for quantitative global and regional modeling studies. In this work, hourly median value of ionosonde measurements namely, peak height F2-layer (hmF2), F2-layer critical frequency (foF2) and propagation factor M(3000)F2 made at near equatorial dip latitude, Ouagadougou, Burkina Faso (12oN, 1.5oW; dip: 1.5oN) and relevant F2-layer parameters such as thickness parameter (Bo), electron temperature (Te), ion temperature (Ti), total electron content (TEC) and electron density (Ne, at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial vertical plasma drift velocities on the diurnal structure of F2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. We show that month-by-month morphological patterns between vertical E×B drifts and F2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI-Bo, IRI-Te and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Assessment of the association between measured foF2, hmF2 and M(3000)F2 illustrates consistent much more smaller correlation coefficients with no systematic linkage. In general, our research indicates strong departure from simple electrodynamically controlled behavior.

  13. Study of maximum electron density N mF 2 at Karachi and Islamabad during solar minimum (1996) and solar maximum (2000) and its comparison with IRI

    Microsoft Academic Search

    M. Ayub; S. Iqbal; M. A. Ameen; B. W. Reinisch

    2009-01-01

    The monthly hourly medians of maximum electron density, NmF2, at two Pakistani ionospheric stations, Karachi and Islamabad, have been determined for solar minimum (1996) and solar maximum (2000) and compared with IRI predictions using the URSI coefficients. At night and pre-noon period the NmF2 values at both stations are almost equal during the 2years. However, at post-noon the values at

  14. Exploring the Prominence-Corona Connection and its Expansion into the Outer Corona Using Total Solar Eclipse Observations

    NASA Astrophysics Data System (ADS)

    Habbal, Shadia Rifai; Morgan, Huw; Druckmüller, Miloslav

    2014-10-01

    Prominences constitute the most complex magnetic structures in the solar corona. The ubiquitous presence of their seemingly confined dense and cool plasma in an otherwise million-degree environment remains a puzzle. Using a decade of white light total solar eclipse observations, we show how these images reveal an intricate relationship between prominences and coronal structures both in their immediate vicinity, known as coronal cavities, and in the extended corona out to several solar radii. Observations of suspended prominences and twisted helical structures spanning several solar radii are central to these findings. The different manifestations of the prominence-corona interface that emerge from this study underscore the fundamental role played by prominences in defining and controlling the complex expansion and dynamic behavior of the solar magnetic field in the neighborhood of magnetic polarity reversal regions. This study suggests that the unraveling of prominences and the outward expansion of the helical twisted field lines linked to them could be the solar origin of twisted magnetic flux ropes detected in interplanetary space, and of the mechanism by which the Sun sheds its magnetic helicity. This work also underscores the likely role of the prominence-corona interface as a source of the slow solar wind.

  15. The Sun's Corona, 1889

    Microsoft Academic Search

    David P. Todd

    1889-01-01

    A GENERAL statement of the successes of the Western Eclipse Expeditions on January 1 has already appeared in NATURE. More photographs of the corona were taken than ever before-many of them indifferent and worthless, but an unusually large number of great excellence. The best that I have so far seen were taken with 5-inch telescopes, by Mr. W. H. Pickering

  16. Inferring the Structure of the Solar Corona and Inner Heliosphere During the Maunder Minimum Using Global Thermodynamic Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Riley, Pete; Lionello, Roberto; Linker, Jon A.; Cliver, Ed; Balogh, Andre; Beer, Jürg; Charbonneau, Paul; Crooker, Nancy; DeRosa, Marc; Lockwood, Mike; Owens, Matt; McCracken, Ken; Usoskin, Ilya; Koutchmy, S.

    2015-04-01

    Observations of the Sun’s corona during the space era have led to a picture of relatively constant, but cyclically varying solar output and structure. Longer-term, more indirect measurements, such as from 10Be, coupled by other albeit less reliable contemporaneous reports, however, suggest periods of significant departure from this standard. The Maunder Minimum was one such epoch where: (1) sunspots effectively disappeared for long intervals during a 70 yr period; (2) eclipse observations suggested the distinct lack of a visible K-corona but possible appearance of the F-corona; (3) reports of aurora were notably reduced; and (4) cosmic ray intensities at Earth were inferred to be substantially higher. Using a global thermodynamic MHD model, we have constructed a range of possible coronal configurations for the Maunder Minimum period and compared their predictions with these limited observational constraints. We conclude that the most likely state of the corona during—at least—the later portion of the Maunder Minimum was not merely that of the 2008/2009 solar minimum, as has been suggested recently, but rather a state devoid of any large-scale structure, driven by a photospheric field composed of only ephemeral regions, and likely substantially reduced in strength. Moreover, we suggest that the Sun evolved from a 2008/2009-like configuration at the start of the Maunder Minimum toward an ephemeral-only configuration by the end of it, supporting a prediction that we may be on the cusp of a new grand solar minimum.

  17. Magnetic Clouds at/near the 2007 - 2009 Solar Minimum: Frequency of Occurrence and Some Unusual Properties

    NASA Technical Reports Server (NTRS)

    Lepping. R. P.; Wu, C.-C.; Berdichevsky, D. B.; Szabo, A.

    2011-01-01

    Magnetic clouds (MCs) have been identified for the period 2007 2009 (at/near the recent solar minimum) from Wind data, then confirmed through MC parameter fitting using a force-free model. A dramatic increase in the frequency of occurrence of these events took place from the two early years of 2007 (with five MCs) and 2008 (one MC) compared to 2009 (12 MCs). This pattern approximately mirrors the occurrence-frequency profile that was observed over a three-year interval 12 years earlier, with eight events in 1995, four in 1996, and 17 in 1997, but decreased overall by a factor of 0.62 in number. However, the average estimated axial field strength taken over all of the 18 events of 2007 - 2009 (called the "recent period" here) was only 11.0 nT, whereas |BO| for the 29 events of 1995 - 1997 (called the "earlier period" ) was 16.5 nT. This 33% average drop in |BO| is more or less consistent with the decreased three-year average interplanetary magnetic field intensity between these two periods, which shows a 23% drop. In the earlier period, the MCs were clearly of mixed types but predominantly of the South-to-North type, whereas those in the recent period are almost exclusively the North-to-South type; this change is consistent with global solar field changes predicted by Bothmer and Rust (Geophys. Monogr. Ser. 99, 139, 1997). As we have argued in earlier work (Lepping and Wu, J. Geophys. Res. 112, A10103, 2007), this change should make it possible to carry out (accurate short-term) magnetic storm forecasting by predicting the latter part of an MC from the earlier part, using a good MC parameter-fitting model with real-time data from a spacecraft at L1, for example. The recent set s average duration is 15.2 hours, which is a 27% decrease compared to that of the earlier set, which had an average duration of 20.9 hours. In fact, all physical aspects of the recent MC set are shown to drop with respect to the earlier set; e.g., as well as the average internal magnetic field drop, the recent set had a somewhat low average speed of 379 km/s (5% drop), and the average diameter had a 24% drop. Hence, compared to the earlier set, the recent set consists of events that are smaller, slightly slower, and weaker in every respect (and fewer in number), but in a relative sense the two three-year sets have similar frequency-of-occurrence profiles. It is also interesting that the two sets have almost the same average axial inclinations, i.e., axial latitude approx. = 31deg (in GSE). These MC characteristics are compared to relevant solar features and their changes. A preliminary assessment of the statistics on possible shocks and pressure pulses upstream of these recent MCs yields the following: About 28% of the MCs, at most, had shocks, and 33% had shocks and/or pressure pulses. These are low values, since typically the percentage of cases with shocks is about 50%, and the percentage with shocks and/or pressure pulses is usually about 75%.

  18. Polarization of the solar corona.

    NASA Technical Reports Server (NTRS)

    Feibelman, W. A.

    1972-01-01

    A method of obtaining polarized photographs of the solar corona during total eclipse is described. The required equipment is a reflex viewing type camera with a lens of adequate focal length to give an image of the corona a few millimeters in diameter at the focal plane. A sheet of linear polarizing filter material is placed directly in front of the lens. The filter is mounted in such a way so as to permit a set of four exposures of equal length to be taken after totality begins. Since the light of the corona is highly polarized, the resultant set of photographs will show marked differences in the shape of the corona.

  19. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High-Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

    2001-01-01

    We correlate solar wind and interplanetary magnetic field (IMF) properties with the properties of O(+) and H(+) during early 1996 (solar minimum) at altitudes between 5.5 and 8.9 R(sub E) geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. Throughout the high-altitude polar cap we observe H(+) to be more abundant than O(+). O(+) is found to be more abundant at lower latitudes when the solar wind speed is low (and Kp is low), while at higher solar wind speeds (and high Kp), O(+) is observed across most of the polar cap. The O(+) density and parallel flux are well organized by solar wind dynamic pressure, both increasing with solar wind dynamic pressure. Both the O(+) density and parallel flux have positive correlations with both V(sub SW)B(sub IMF) and E(sub SW). No correlation is found between O(+) density and IMF Bz, although a nonlinear relationship with IMF By is observed, possibly due to a strong linear correlation with the dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, although H(+) density and parallel flux are negatively correlated with IMF By and positively correlated with both V(sub SW)B(sub IMF) and E(sub SW). In this solar minimum data set, H(+) is dominant, so that contributions of this plasma to the plasma sheet would have very low O(+) to H(+) ratios.

  20. Accretion disk coronae

    NASA Technical Reports Server (NTRS)

    White, N. E.; Holt, S. S.

    1981-01-01

    Recent observations of partial X-ray eclipses from 4U1822-37 have shown that the central X-ray source in this system is diffused by a large Compton-thick accretion disk corona (ADC). Another binary, 4U2129-47, also displays a partial eclipse and contains an ADC. The possible origin of an ADC is discussed and a simple hydrostatic evaporated ADC model is developed which, when applied to 4U1822-37, 4U2129+47 and Cyg X-3, can explain their temporal and spectral properties. The quasi-sinusoidal modulation of all three sources can be reconciled with the partial occultation of the ADC by a bulge at the edge of the accretion disk which is caused by the inflowing material. The height of this bulge is an order of magnitude larger than the hydrostatic disk height and is the result of turbulence in the outer region of the disk. The spectral properties of all three sources can be understood in terms of Compton scattering of the original source spectrum by the ADC. Spectral variations with epoch in Cyg X-3 are probably caused by changes in the optical depth of the corona. A consequence of our model is that any accreting neutron star X-ray source in a semi-detached binary system which is close to its Eddington limit most likely contains an optically thick ADC.

  1. Ultraviolet corona detection sensor study

    NASA Technical Reports Server (NTRS)

    Schmitt, R. J.; MATHERN

    1976-01-01

    The feasibility of detecting electrical corona discharge phenomena in a space simulation chamber via emission of ultraviolet light was evaluated. A corona simulator, with a hemispherically capped point to plane electrode geometry, was used to generate corona glows over a wide range of pressure, voltage, current, electrode gap length and electrode point radius. Several ultraviolet detectors, including a copper cathode gas discharge tube and a UV enhanced silicon photodiode detector, were evaluated in the course of the spectral intensity measurements. The performance of both silicon target vidicons and silicon intensified target vidicons was evaluated analytically using the data generated by the spectroradiometer scans and the performance data supplied by the manufacturers.

  2. Properties of accretion disk coronae

    NASA Technical Reports Server (NTRS)

    Wilms, J.; Dove, J.; Staubert, R.; Begelman, M. C.

    1997-01-01

    The properties of accretion disk corona in a parameter regime suitable for Galactic black hole candidates are considered and the results of an analysis of these properties using a self-consistent Monte Carlo code are presented. Examples of the coronal temperature structure, the shape and angular dependency of the spectrum and the maximum temperature allowed for each optical depth of the corona are presented. It is shown that the observed spectrum of the Galactic black hole candidate Cygnus X-1 cannot be explained by accreting disk corona models with a slab geometry, where the accretion disk is sandwiched by the comptonizing medium.

  3. Changes in radial gradients of low-energy cosmic rays between solar minimum and maximum: - Observations from 1 to 31 AU

    NASA Technical Reports Server (NTRS)

    Mckibben, R. B.; Pyle, K. R.; Simpson, J. A.

    1985-01-01

    Observations of the fluxes and radial gradients of protons and helium (with energies of 10-70 Mev per n) between the period of minimum solar modulation ending in 1977 and the period of maximum modulation in 1981-1983 show that, over the radial range 1-31 AU, radial gradients decreased for both species from their solar minimum values (5-10 percent per AU for galactic protons and helium) to values of 2-4 percent per AU or less. For these low-energy cosmic rays it is found that the variation in modulation with the phase of the solar cycle is much stronger at radii of 20-30 AU than at 1 AU, and that at solar maximum, more than 99 percent of the total modulation takes place beyond 31 AU.

  4. Radiation Measured with Different Dosimeters for ISS-Expedition 18-19/ULF2 on Board International Space Station during Solar Minimum

    NASA Technical Reports Server (NTRS)

    Zhou, Dazhuang; Gaza, R.; Roed, Y.; Semones, E.; Lee, K.; Steenburgh, R.; Johnson, S.; Flanders, J.; Zapp, N.

    2010-01-01

    Radiation field of particles in low Earth orbit (LEO) is mainly composed of galactic cosmic rays (GCR), solar energetic particles and particles in SAA (South Atlantic Anomaly). GCR are modulated by solar activity, at the period of solar minimum activity, GCR intensity is at maximum and the main contributor for space radiation is GCR. At present for space radiation measurements conducted by JSC (Johnson Space Center) SRAG (Space Radiation Analysis Group), the preferred active dosimeter sensitive to all LET (Linear Energy Transfer) is the tissue equivalent proportional counter (TEPC); the preferred passive dosimeters are thermoluminescence dosimeters (TLDs) and optically stimulated luminescence dosimeters (OSLDs) sensitive to low LET as well as CR-39 plastic nuclear track detectors (PNTDs) sensitive to high LET. For the method using passive dosimeters, radiation quantities for all LET can be obtained by combining radiation results measured with TLDs/OSLDs and CR-39 PNTDs. TEPC, TLDs/OSLDs and CR-39 detectors were used to measure the radiation field for the ISS (International Space Station) - Expedition 18-19/ULF2 space mission which was conducted from 15 November 2008 to 31 July 2009 - near the period of the recent solar minimum activity. LET spectra (differential and integral fluence, absorbed dose and dose equivalent) and radiation quantities were measured for positions TEPC, TESS (Temporary Sleeping Station, inside the polyethylene lined sleep station), SM-P 327 and 442 (Service Module - Panel 327 and 442). This paper presents radiation LET spectra measured with TEPC and CR-39 PNTDs and radiation dose measured with TLDs/OSLDs as well as the radiation quantities combined from results measured with passive dosimeters.

  5. Statistical study of the night-time F-layer dynamics at the magnetic equator in West Africa during the solar minimum period 1995-1997

    NASA Astrophysics Data System (ADS)

    Tanoh, K. S.; Adohi, B. J.-P.; Coulibaly, I. S.; Amory-Mazaudier, C.; Kobea, A. T.; Assamoi, P.

    2015-01-01

    In this paper, we report on the night-time equatorial F-layer height behaviour at Korhogo (9.2° N, 5° W; 2.4° S dip lat), Ivory Coast, in the West African sector during the solar minimum period 1995-1997. The data were collected from quarter-hourly ionograms of an Ionospheric Prediction Service (IPS) 42-type vertical sounder. The main focus of this work was to study the seasonal changes in the F-layer height and to clarify the equinox transition process recently evidenced at Korhogo during 1995, the year of declining solar flux activity. The F-layer height was found to vary strongly with time, with up to three main phases. The night-to-night variability of these morphological phases was then analysed. The early post-sunset slow rise, commonly associated with rapid chemical recombination processes in the bottom part of the F layer, remained featureless and was observed regardless of the date. By contrast, the following event, either presented like the post-sunset height peak associated with the evening E × B drift, or was delayed to the midnight sector, thus involving another mechanism. The statistical analysis of the occurrence of these events throughout the solar minimum period 1995-1997 revealed two main F-layer height patterns, each characteristic of a specific season. The one with the post-sunset height peak was associated with the northern winter period, whereas the other, with the midnight height peak, characterized the northern summer period. The transition process from one pattern to the other took place during the equinox periods and was found to last only a few weeks. We discuss these results in the light of earlier works.

  6. A Determination of the North–South Heliospheric Magnetic Field Component from Inner Corona Closed-loop Propagation

    NASA Astrophysics Data System (ADS)

    Jackson, B. V.; Hick, P. P.; Buffington, A.; Yu, H.-S.; Bisi, M. M.; Tokumaru, M.; Zhao, X.

    2015-04-01

    A component of the magnetic field measured in situ near the Earth in the solar wind is present from north–south fields from the low solar corona. Using the Current-sheet Source Surface model, these fields can be extrapolated upward from near the solar surface to 1 AU. Global velocities inferred from a combination of interplanetary scintillation observations matched to in situ velocities and densities provide the extrapolation to 1 AU assuming mass and mass flux conservation. The north–south field component is compared with the same ACE in situ magnetic field component—the Normal (Radial Tangential Normal) Bn coordinate—for three years throughout the solar minimum of the current solar cycle. We find a significant positive correlation throughout this period between this method of determining the Bn field compared with in situ measurements. Given this result from a study during the latest solar minimum, this indicates that a small fraction of the low-coronal Bn component flux regularly escapes from closed field regions. The prospects for Space Weather, where the knowledge of a Bz field at Earth is important for its geomagnetic field effects, is also now enhanced. This is because the Bn field provides the major portion of the Geocentric Solar Magnetospheric Bz field coordinate that couples most closely to the Earth’s geomagnetic field.

  7. Structure and Dynamics of the 2010 July 11 Eclipse White-light Corona

    NASA Astrophysics Data System (ADS)

    Pasachoff, J. M.; Rušin, V.; Druckmüllerová, H.; Saniga, M.; Lu, M.; Malamut, C.; Seaton, D. B.; Golub, L.; Engell, A. J.; Hill, S. W.; Lucas, R.

    2011-06-01

    The white-light corona (WLC) during the total solar eclipse on 2010 July 11 was observed by several teams in the Moon's shadow stretching across the Pacific Ocean and a number of isolated islands. We present a comparison of the WLC as observed by eclipse teams located on the Tatakoto Atoll in French Polynesia and on Easter Island, 83 minutes later, combined with near-simultaneous space observations. The eclipse was observed at the beginning of the solar cycle, not long after solar minimum. Nevertheless, the solar corona shows a plethora of different features (coronal holes, helmet streamers, polar rays, very faint loops and radial-oriented thin streamers, a coronal mass ejection, and a puzzling "curtain-like" object above the north pole). Comparing the observations from the two sites enables us to detect some dynamic phenomena. The eclipse observations are further compared with a hairy-ball model of the magnetic field and near-simultaneous images from the Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory, the Extreme Ultraviolet Imager on NASA's Solar Terrestrial Relations Observatory, the Sun Watcher, using Active Pixel System Detector and Image Processing on ESA's PRoject for Onboard Autonomy, and the Naval Research Laboratory's Large Angle and Spectrometric Coronagraph on ESA's Solar and Heliospheric Observatory. The Ludendorff flattening coefficient is 0.156, matching the expected ellipticity of coronal isophotes at 2 R sun, for this rising phase of the solar-activity cycle.

  8. Spectroscopic investigation of protein corona

    NASA Astrophysics Data System (ADS)

    Choudhary, Poonam

    Nanotechnology has revolutionalized the landscape of modern science and technology, including materials, electronics, therapeutics, bioimaging, sensing, and the environment. Research in the past decade has examined the fate of nanomaterials in vitro and in vivo, as well as the interactions between nanoparticles and biological and ecosystems using primarily toxicological and ecotoxicological approaches. However, due to the versatility in the physical and physicochemical properties of nanoparticles, and due to the vast complexity of their hosting systems, the solubility, transformation, and biocompatibility of nanomaterials are still poorly understood. Nanotechnology has been undergoing tremendous development in recent decades, driven by realized perceived applications of nanomaterials in electronics, therapeutics, imaging, sensing, environmental remediation, and consumer products. Nanoparticles on entering the blood stream undergo an identity change, they become coated with proteins. There are different kind of proteins present in blood. Proteins compete for getting coated over the surface of nanoparticle and this whole entity of proteins coated over nanoparticle surface is called Protein Corona. Proteins tightly bound to the surface of nanoparticle form hard corona and the ones loosely bound on the outer surface form soft corona. This dissertation is aimed at spectroscopic investigation of Protein Corona. Chapter I of this dissertation offers a comprehensive review of the literature based on nanomaterials with the focus on carbon based nanomaterilas and introduction to Protein Corona. Chapter II is based different methods used for Graphene Synthesis,different types of defects and doping. In Chapter III influence of defects on Graphene Protein Corona was investigated. Chapter IV is based on the study of Apoptosis induced cell death by Gold and silver nanoparticles. In vitro study of effect of Protein Corona on toxicity of cells was done.

  9. Insights into Corona Formation through Statistical Analyses

    NASA Technical Reports Server (NTRS)

    Glaze, L. S.; Stofan, E. R.; Smrekar, S. E.; Baloga, S. M.

    2002-01-01

    Statistical analysis of an expanded database of coronae on Venus indicates that the populations of Type 1 (with fracture annuli) and 2 (without fracture annuli) corona diameters are statistically indistinguishable, and therefore we have no basis for assuming different formation mechanisms. Analysis of the topography and diameters of coronae shows that coronae that are depressions, rimmed depressions, and domes tend to be significantly smaller than those that are plateaus, rimmed plateaus, or domes with surrounding rims. This is consistent with the model of Smrekar and Stofan and inconsistent with predictions of the spreading drop model of Koch and Manga. The diameter range for domes, the initial stage of corona formation, provides a broad constraint on the buoyancy of corona-forming plumes. Coronae are only slightly more likely to be topographically raised than depressions, with Type 1 coronae most frequently occurring as rimmed depressions and Type 2 coronae most frequently occuring with flat interiors and raised rims. Most Type 1 coronae are located along chasmata systems or fracture belts, while Type 2 coronas are found predominantly as isolated features in the plains. Coronae at hotspot rises tend to be significantly larger than coronae in other settings, consistent with a hotter upper mantle at hotspot rises and their active state.

  10. Energy release in the solar corona from spatially resolved magnetic braids.

    PubMed

    Cirtain, J W; Golub, L; Winebarger, A R; De Pontieu, B; Kobayashi, K; Moore, R L; Walsh, R W; Korreck, K E; Weber, M; McCauley, P; Title, A; Kuzin, S; DeForest, C E

    2013-01-24

    It is now apparent that there are at least two heating mechanisms in the Sun's outer atmosphere, or corona. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000?K (refs 1-3). The active corona needs additional heating to reach 2,000,000-4,000,000?K; this heat has been theoretically proposed to come from the reconnection and unravelling of magnetic 'braids'. Evidence favouring that process has been inferred, but has not been generally accepted because observations are sparse and, in general, the braided magnetic strands that are thought to have an angular width of about 0.2?arc seconds have not been resolved. Fine-scale braiding has been seen in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2?arc seconds, of magnetic braids in a coronal active region that are reconnecting, relaxing and dissipating sufficient energy to heat the structures to about 4,000,000?K. Although our 5-minute observations cannot unambiguously identify the field reconnection and subsequent relaxation as the dominant heating mechanism throughout active regions, the energy available from the observed field relaxation in our example is ample for the observed heating. PMID:23344359

  11. MODELING THE LINE-OF-SIGHT INTEGRATED EMISSION IN THE CORONA: IMPLICATIONS FOR CORONAL HEATING

    SciTech Connect

    Viall, Nicholeen M.; Klimchuk, James A. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2013-07-10

    One of the outstanding problems in all of space science is uncovering how the solar corona is heated to temperatures greater than 1 MK. Though studied for decades, one of the major difficulties in solving this problem has been unraveling the line-of-sight (LOS) effects in the observations. The corona is optically thin, so a single pixel measures counts from an indeterminate number (perhaps tens of thousands) of independently heated flux tubes, all along that pixel's LOS. In this paper we model the emission in individual pixels imaging the active region corona in the extreme ultraviolet. If LOS effects are not properly taken into account, erroneous conclusions regarding both coronal heating and coronal dynamics may be reached. We model the corona as an LOS integration of many thousands of completely independently heated flux tubes. We demonstrate that despite the superposition of randomly heated flux tubes, nanoflares leave distinct signatures in light curves observed with multi-wavelength and high time cadence data, such as those data taken with the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. These signatures are readily detected with the time-lag analysis technique of Viall and Klimchuk in 2012. Steady coronal heating leaves a different and equally distinct signature that is also revealed by the technique.

  12. Theory of accretion disk coronae

    NASA Technical Reports Server (NTRS)

    Kallman, T. R.

    1990-01-01

    Accretion disk coronae are likely to be the dominant site for X-ray absorption and reprocessed emission in low mass X-ray binaries, and may be present in other classes of compact X-ray sources such as active galactic nuclei and cataclysmic variables. In spite of this fact, and in spite of the observational evidence for their existence, there remain many uncertainties about the structure of accretion disk coronae. This paper will discuss the coronal structure and dynamics, their X-ray spectral signatures including coupling to the variability behavior of compact X-ray sources, and the major unsolved theoretical issues surrounding them.

  13. Hot oxygen corona of Mars

    SciTech Connect

    Ip, W.H.

    1988-10-01

    Electron dissociative recombination of O2(+) ions in the Venus ionosphere, which may be an important source of suprathermal atomic oxygen, is presently considered as a factor in the Mars exosphere; due to the weaker surface gravitational attraction of Mars, a hot oxygen corona thus formed would be denser than that of Venus at altitudes greater than 2000 km despite Mars' lower ionospheric content. If such an extended oxygen corona does exist on Mars, its collisional interaction with Phobos would lead to the formation of an oxygen gas torus whose average number density is of the order of only 1-2/cu cm along the Phobos orbit. 51 references.

  14. Nonlocal Unified Type-I and Type-II Model of the Low-Latitude E-region Irregularities at Solar Minimum and Solar Maximum

    NASA Astrophysics Data System (ADS)

    Hassan, E.; Horton, W.; Smolyakov, A.; Litt, S.; Hatch, D.

    2013-12-01

    The onset of the small-scale irregularities at the E-region are due to both Farley-Buneman and gradient-drift instabilities. Those instabilities were detected at Jicamarca Radar Observatory at 50-MHz and differentiated according their Doppler-Shifts and called Type-I and Type-II, respectively. We developed a nonlocal unified model to study the characteristics of these two instabilities in the linear a nonlinear regimes. The simulation results are based on data of the charged-carrier densities from IRI2012, neutral densities from NMSIS00, electric potential from TIEGCM-1.94, and magnetic field from IGRF-like model. In this model, which based on quasi-neutrality and isothermal approximations, we study the perturbations in the electron carrier density, the electric potential, and ion velocity to show how the instabilities are evolving due to the mode-interactions among these three fields. We compare the simulation results of this model under the conditions of solar minimum and solar maximum. W.H. is supported by NSF Grant 0964692 to the University of Texas at Austin. W.H. and A. S. are partially supported by Aix-Marseille/CNRS and the International Space Science Institute in Bern, Switzerland through the Grant on on "Vortices and zonal winds in planetary atmospheres/ionospheres."

  15. Theoretical predictions for ion composition in the high-latitude winter F-region for solar minimum and low magnetic activity

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Raitt, W. J.; Schunk, R. W.

    1981-01-01

    A simple plasma convection model is combined with an ionospheric-atmospheric density model in order to study the ion composition in the high-latitude winter F-region at solar minimum for low geomagnetic activity. The numerical study produces time-dependent, three-dimensional ion density distributions for the ions NO(+), O2(+), N2(+), O(+), N(+), and He(+). The high-latitude ionosphere above 54 deg N magnetic latitude is covered at altitudes between 160 and 800 km for one complete day. Among the conclusions are the following: the ion composition varies significantly with latitude, local time, altitude, and universal time; the variations in the ion composition with latitude and local time are in good agreement with the Atmosphere Explorer measurements both quantitatively and qualitatively; and at times and at certain locations the molecular ion density can be comparable to the O(+) density at 300 km, and at 200 km the O(+) density can be comparable to the molecular ion density.

  16. HEATING OF CHROMOSPHERES AND CORONAE P. ULMSCHNEIDER

    E-print Network

    Ulmschneider, Peter

    HEATING OF CHROMOSPHERES AND CORONAE P. ULMSCHNEIDER Institut [iir Theoretische Astrophysik-mail:ulm@ita.uni-heidelberg.de \\Abstract. Almost all nondegenerate stars have chromospheres and coronae. These hot outer layers are produced by mechanical heating. The heating mechanisms of chromospheres and coronae, clas- sified

  17. Non-Markovian Diffusive Unravellings of Entanglement

    E-print Network

    Brittany Corn; Jun Jing; Ting Yu

    2011-05-06

    The fully quantized model of two qubits coupled to a common bath is solved using the quantum state diffusion (QSD) approach in the non-Markovian regime. We have established an explicit time-local non-Markovian QSD equation for the two-qubit dissipative model. Diffusive quantum trajectories are applied to the entanglement estimation of two-qubit systems in a non-Markovian regime. In another interesting example, we have also considered exact entanglement unravellings for a dephasing model. In both cases, non-Markovian features of entanglement evolution are revealed through quantum diffusive unravellings in the qubit state space.

  18. LABORATORY ANALYSES OF CORONA DISCHARGES

    EPA Science Inventory

    The paper discusses an experimental research program to characterize corona generation from different electrode geometries in a range of conditions comparable to those found in electrostatic precipitators (ESPs). A wire-parallel plate device and a wire-cylinder device were used t...

  19. Interferometry of the e corona.

    PubMed

    Henderson, G

    1970-12-01

    Descriptions are given of Fabry-Perot spectrometer systems used in the total eclipses of 1965, 1966, and 1970 to observe the emission lines 5303 A, Fe XIV and 6374 A, Fe x at different points in the solar corona. Some results of coronal temperature measurements for the 12 November 1966 eclipse are presented. PMID:20094331

  20. Ultraviolet Corona Discharge Detection Based on Photomultiplier

    NASA Astrophysics Data System (ADS)

    Yongli, Liao; Liming, Wang; Ke, Wang; Canlin, Wang; Zhicheng, Guan

    High voltage equipments, especially polymer insulators may be getting into aging conditions due to the existence of corona discharge on the surface after a long term of running, which would accelerate the deterioration of the surface insulation performance, and even make equipments step into calamity ultimately. So it is significant to detect corona discharge on surface to ensure insulators' stable running. This paper presents the development of a novel corona discharge detection system based on photomultiplier tube (PMT), which has good functions of distance detection for corona discharge in determined region from surface of high voltage equipment and corona characteristics data analysis. In the verification experiments, it was shown that UV corona light can be also taken as characteristic for detecting corona discharge, other than corona leakage current detection, and a linear relationship was shown between the light magnitude and the current magnitude. Furthermore, mean peak value and number of pulses whose peak value is above threshold are extracted from the basic data, which can be used to quantify the development of corona discharge. The results of investigation on polymer insulators suggested that detection of the region between metal end fitting and first shed should be emphasized. The measurements of corona discharge distribution along insulators can be used to learn about the degradation conditions. Detection of polymer insulators in lab and field inspection experience are both soundly verifying the usefulness of the corona detection system.

  1. Equilibrium Information Disclosure: Grade Inflation and Unraveling

    Microsoft Academic Search

    Michael Ostrovsky; Michael A. Schwarz

    2003-01-01

    This paper explores information disclosure in matching markets, e. g. the informativeness of transcripts given out by universities. We show that the same amount of information is disclosed in all equilibria. We then demonstrate that if universities disclose the equilibrium amount of information, students and employers will not find it profitable to contract early; if they disclose more, unraveling will

  2. Equatorial vertical plasma drifts and the measured and IRI model-predicted F 2-layer parameters above Ouagadougou during solar minimum

    NASA Astrophysics Data System (ADS)

    Oyekola, O. S.

    2012-06-01

    In this paper, hourly median value of ionosonde measurements: peak height F 2-layer ( h m F 2), F 2-layer critical frequency ( f o F 2) and propagation factor M(3000) F 2 made at near-equatorial dip latitude, Ouagadougou, Burkina Faso (12°N, 1.5°W; dip: 1.5°N) and relevant F 2-layer parameters: thickness parameter ( B o), electron temperature ( T e), ion temperature ( T i), total electron content (TEC) and electron density ( N e) (at the fixed altitude of 300 km) provided by the International Reference Ionosphere (IRI) model for the longitude of Ouagadougou are contrasted with the IRI vertical drift model to explore in detail the monthly climatological behavior of equatorial ionosphere and the effects of equatorial electrodynamics on the diurnal structure of F 2-layer parameters. The analysis period covers four months representative of solstitial and equinoctial seasonal periods during solar minimum year of 1987 for geomagnetically quiet-day. It is demonstrated that the month-by-month morphological patterns between vertical E × B drifts and F 2-layer parameters range from worst to reasonably good and are largely seasonally dependent. A cross-correlation analysis conducted between equatorial drift and F 2-layer characteristics yield statistically significant correlations for equatorial vertical drift and IRI- B o, IRI- T e and IRI-TEC, whereas little or no acceptable correlation is obtained with observational evidence. Examination of the association between measured f o F 2, h m F 2 and M(3000) F 2 illustrates consistent much more smaller correlation coefficients with no systematic linkage.

  3. Structures of Binary Star Coronae

    NASA Astrophysics Data System (ADS)

    Brickhouse, N. S.

    2004-01-01

    Stellar coronae in binary star systems offer both a puzzle and an opportunity. While one might expect that large magnetic loop structures on close binaries such as RS CVn systems and contact binaries would show evidence for interactions. While some radio studies support this scenario there is surprisingly little evidence from EUV and X-ray observations for differences between binary and single star systems. Meanwhile the binary systems offer observational opportunities through rotational modulation and eclipses of flaring and non-flaring regions. Localizing the sources of coronal emission is key to making the magnetic connection to the underlying photosphere. We discuss the structure of stellar coronae from the perspective of studies of binary systems.

  4. Chromospheres, transition regions, and coronas.

    PubMed

    Böhm-Vitense, E

    1984-02-24

    The increase in temperature outward from the surface of a stellar photosphere can be understood by looking at the local energy balance. The relatively high-density stellar photosphere is cooled effectively by radiative energy loss penetrating the optically thin corona. For the low-density chromosphere and corona, if the energy input cannot be balanced by radiative energy losses, the temperature will rise steeply, possibly up to 1 million degrees or more. Coronal heating and emission appear to be strongly influenced by magnetic fields, leading to large differences in x-ray emission for otherwise similar stars. Comparatively small variations are seen in the overall chromospheric emission of stars. Chromospheres are probably mainly heated by shock-wave energy dissipation, modified by magnetic fields. PMID:17737739

  5. Artemis Corona (C2-MIDR)

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This spectacular Magellan image is centered on 30 degrees south latitude, 135 degrees east longitude, spans 3500 kilometers (2170 miles) from east to west (left to right), and shows the near-circular trough of Artemis Chasma. Its circular shape and size (2100 km or 1302 miles in diameter) make Artemis the largest corona identified to date on the surface of Venus. Artemis could encompass most of the U.S. from the Front Range of the Rockies (near Denver) to the West Coast and is approximately twice the diameter of the next-smaller corona Heng-O. Coronae are characterized by a ring of concentric features surrounding an interior which typically contains fractures of varying orientations and volcanic features ranging from individual flows and small ( 100 kilometers [62 mile]) shield volcanoes. Artemis contains complex systems of fractures, numerous flows and small volcanoes, and at least two impact craters, the larger of which is located in the lower left (southwest) quadrant of the feature. The ring of fractures that defines Artemis forms a steep trough with raised rims approximately 120 kilometers (74 miles) wide and with as much as 2.5 kilometers (1.6 miles) of relief from the rim crest to the bottom of the trough. Most coronae are thought to be related to upwelling of hot material from the interior of Venus in the form of plumes or diapirs, and Artemis may be an extensional trough related to such an upwelling event. Raised-rim troughs are most commonly found to be extensional features (those formed by forces which tend to pull apart the crust and lithosphere of a planet) but the unusual size and circularity of Artemis have led to the alternate suggestion that it may be a zone of intense compression and underthrusting, similar to oceanic subduction zones on Earth. Magellan scientists are currently examining this feature in detail to determine which, if either, of these hypotheses is correct.

  6. Tectonics of Neyterkob corona on Venus

    NASA Technical Reports Server (NTRS)

    Kauhanen, K.

    1993-01-01

    Neyterkob double corona (50 deg N 202 deg) presents an area of corona-related interfering tectonic patterns which are formed in different phases of evolution of the corona and modified by regional stresses. Analyzing the patterns can reveal something about the coronal formation. Tectonic features form distinct units on topographic depressions, slopes, and volcanic flows extending over one radius of the corona. A remarkable amount of compressional features were found near the rim and related to interaction between adjacent coronae. Radial extension was mainly observed on a peculiar NE-SW trending high crossing the corona. Concentric fractures were found to the east partly connected to the lithospheric flexure. Tectonic features indicate movements of volcanic activity and modification of the area by more regional stresses.

  7. Corona-vacuum failure mechanism test facilities

    NASA Technical Reports Server (NTRS)

    Lalli, V. R.; Mueller, L. A.; Koutnik, E. A.

    1975-01-01

    A nondestructive corona-vacuum test facility for testing high-voltage power system components has been developed using commercially available hardware. The facility simulates operating temperature and vacuum while monitoring coronal discharges with residual gases. Corona threshold voltages obtained from statorette tests with various gas-solid dielectric systems and comparison with calculated data support the following conclusions: (1) air gives the highest corona threshold voltage and helium the lowest, with argon and helium-xenon mixtures intermediate; (2) corona threshold voltage increases with gas pressure; (3) corona threshold voltage for an armature winding can be accurately calculated by using Paschen curves for a uniform field; and (4) Paschen curves for argon can be used to calculate the corona threshold voltage in He-Xe mixtures, for which Paschen curves are unavailable.-

  8. Corona Discharge Influences Ozone Concentrations Near Rats

    SciTech Connect

    Goheen, Steven C.; Gaither, Kari A.; Anantatmula, Shantha M.; Mong, Gary M.; Sasser, Lyle B.; Lessor, Delbert L.

    2004-02-26

    Ozone is produced by corona discharge in air. Its production is enhanced near grounded water. Whether grounded animals behave like grounded water, producing more ozone was investigated. Rats were exposed to corona discharge in a plastic cage. The concentration of ozone in the gas phase was monitored. The ozone concentration exceeded ambient levels only in the presence of corona discharge and either rats or water. When water or rats were exposed to corona discharge, ozone levels were more than 10 times higher than controls. Ozone levels increased rapidly with applied voltage. There was also a correlation between the distance of the corona needle to the rats and the amount of ozone produced. As the distance increased, ozone production decreased. These results are discussed in relation to the potential exposure of mammals to ozone in the vicinity of corona discharge and electric fields.

  9. Gravity over coronae and chasmata on Venus

    NASA Technical Reports Server (NTRS)

    Schubert, Gerald; Moore, William B.; Sandwell, David T.

    1994-01-01

    The global spherical harmonic model of Venus' gravity field MGNP60FSAAP, with horizontal resolution of about 600 km, shows that most coronae have little or no signature in the gravity field. Nevertheless, some coronae and some segments of chasmata are associated with distinct positive gravity anomalies. No corona has been found to have a negative gravity anomaly. The spatial coincidence of the gravity highs over four closely spaced 300- to 400-km-diameter coronae in Eastern Eistla Regio with the structures themselves is remarkable and argues for a near-surface or lithospheric origin of the gravity signals over such relatively small features. Apparent depths of compensation (ADCs) of the prominent gravity anomalies at Artemis, Latona, and Heng-o Coronae are about 150 to 200 km. The geoid/topography ratios (GTRs) at Artemis, Latona, and Heng-o Coronae lie in the range 32 to 35 m/km. The large ADCs and GTRs of Artemis, Latona, and Heng-o Coronae are consistent with topographically related gravity and a thick Venus lithosphere or shallowly compensated topography and deep positive mass anomalies due to subduction of underthrusting at these coronae. At arcuate segments of Hecate and Parga Chasmata ADCs are about 125 to 150 km, while those at Fauta Corona, four coronae in Eastern Eistla Regio, and an arcuate segment of Wester Parga Chasmata are about 75 km. The GTRs at Fauta Corona, the four coronae in eastern Eistla Regio, and the accurate segments of Hecate, Parga, and Western Parga Chasmata are about 12 to 21 m/km. By analogy with gravity anomalies of similar horizontal scale (600 km-several thousand kilometers) on the concave sides of terrestrial subduction zone arcs, which are due in large part to subducted lithosphere, it is inferred that the gravity anomalies on Venus are consistent with retrograde subduction at Artemis Chasma, along the northern and southern margins of Latona Coronam, and elsewhere along Parga and Hecate Chasmata.

  10. Point-to-Plane Impulse Corona

    Microsoft Academic Search

    Donald Baker Moore; William N. English

    1949-01-01

    The characteristics of impulse corona have been studied in a point-to-plane gap. Both positive and negative square voltage pulses of one- and two-microsecond duration were used with various voltages and pulse repetition rates. The impulse corona in air is found to be quite similar to the d.c. corona, except that the phenomena are exaggerated by the relative absence of space

  11. Negative ions in Trichel corona in air

    Microsoft Academic Search

    P. S. Gardiner; J. D. Craggs

    1977-01-01

    The negative ions formed in Trichel corona in air (10-30 Torr pressure) have been identified and their times of flight in the corona gap measured. It is confirmed that the Trichel pulse frequency, at or near threshold, involves a full transit of the negative-ion space-charge layer.

  12. The pulsed corona discharge in liquid argon

    Microsoft Academic Search

    N. Bonifaci; A. Denat; V. Atrazhev; N. Kim

    2000-01-01

    DC negative corona discharge was studied in liquid Ar near the triple point. A regular current pulse regime was observed. Pulse duration and frequency depended on liquid purification (i.e. oxygen content) and their values determined the corona current. Pulses had triangle-like shape with a very fast rise time. The results of numerical simulation of Trichel pulses in low pressure gases

  13. Parga Chasma: Coronae and Rifting on Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, S. E.; Stofan, E. R.; Buck, W. R.; Martin, P.

    2005-01-01

    The majority of coronae (quasicircular volcano-tectonic features) are found along rifts or fracture belts, and the majority of rifts have coronae [e.g. 1,2]. However, the relationship between coronae and rifts remains unclear [3-6]. There is evidence that coronae can form before, after, or synchronously with rifts [3,4]. The extensional fractures in the rift zones have been proposed to be a result of broad scale upwelling and traction on the lower lithosphere [7]. However, not all rift systems have a significant positive geoid anomaly, as would be expected for an upwelling site [8]. This could be explained if the rifts lacking anomalies are no longer active. Coronae are generally accepted to be sites of local upwelling [e.g. 1], but the observed rifting is frequently not radial to the coronae and extends well beyond the coronae into the surrounding plains. Thus the question remains as to whether the rifts represent regional extension, perhaps driven by mantle tractions, or if the coronae themselves create local thinning and extension of the lithosphere. In the first case, a regional extension model should be consistent with the observed characteristics of the rifts. In the latter case, a model of lithospheric loading and fracturing would be more appropriate. A good analogy may be the propagation of oceanic intraplate volcanoes [9].

  14. Streamer mechanism for negative corona current pulses

    NASA Astrophysics Data System (ADS)

    ?ernák, Mirko; Hosokawa, Tatsuzo; Kobayashi, Shigeo; Kaneda, Teruo

    1998-06-01

    Current wave forms of initial stages of breakdown and corona formation in a short negative point-to-plane gap have been measured with a nanosecond time resolution in air, O2, and N2 at pressures 13.33-100 kPa, and at various overvoltages. The experiments revealed the existence of a stepped form of negative corona Trichel pulses in O2 at atmospheric pressure. To test existing models for the negative corona pulse formation, effects of changing cathode secondary electron emission were studied using a brass cathode coated by CuI and graphite. It is concluded that a negative corona (Trichel) pulse is associated with the ignition of a cathode-directed streamer in the immediate vicinity of the cathode and the subsequent formation of a glow-discharge-type cathode region at the streamer arrival to the cathode. The implications of these results to negative corona applications are discussed.

  15. Global Magnetohydrodynamic Modeling of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Linker, Jon A.; Wagner, William (Technical Monitor)

    2001-01-01

    The solar corona, the hot, tenuous outer atmosphere of the Sun, exhibits many fascinating phenomena on a wide range of scales. One of the ways that the Sun can affect us here at Earth is through the large-scale structure of the corona and the dynamical phenomena associated with it, as it is the corona that extends outward as the solar wind and encounters the Earth's magnetosphere. The goal of our research sponsored by NASA's Supporting Research and Technology Program in Solar Physics is to develop increasingly realistic models of the large-scale solar corona, so that we can understand the underlying properties of the coronal magnetic field that lead to the observed structure and evolution of the corona. We describe the work performed under this contract.

  16. Interplanetary Fast Shocks and Associated Drivers Observed through the Twenty-Third Solar Minimum by WIND Over its First 2.5 Years

    NASA Technical Reports Server (NTRS)

    Mariani, F.; Berdichevsky, D.; Szabo, A.; Lepping, R. P.; Vinas, A. F.

    1999-01-01

    A list of the interplanetary (IP) shocks observed by WIND from its launch (in November 1994) to May 1997 is presented. Forty two shocks were identified. The magnetohydrodynamic nature of the shocks is investigated, and the associated shock parameters and their uncertainties are accurately computed using a practical scheme which combines two techniques. These techniques are a combination of the "pre-averaged" magnetic-coplanarity, velocity-coplanarity, and the Abraham-Schrauner-mixed methods, on the one hand, and the Vinas and Scudder [1986] technique for solving the non-linear least-squares Rankine-Hugoniot shock equations, on the other. Within acceptable limits these two techniques generally gave the same results, with some exceptions. The reasons for the exceptions are discussed. It is found that the mean strength and rate of occurrence of the shocks appears to correlated with the solar cycle. Both showed a decrease in 1996 coincident with the time of the lowest ultraviolet solar radiance, indicative of solar minimum and start of solar cycle 23, which began around June 1996. Eighteen shocks appeared to be associated with corotating interaction regions (CIRs). The distribution of their shock normals showed a mean direction peaking in the ecliptic plane and with a longitude (phi(sub n)) in that plane between perpendicular to the Parker spiral and radial from the Sun. When grouped according to the sense of the direction of propagation of the shocks the mean azimuthal (longitude) angle in GSE coordinates was approximately 194 deg for the fast-forward and approximately 20 deg for the fast-reverse shocks. Another 16 shocks were determined to be driven by solar transients, including magnetic clouds. These shocks had a broader distribution of normal directions than those of the CIR cases with a mean direction close to the Sun-Earth line. Eight shocks of unknown origin had normal orientation well off the ecliptic plane. No shock propagated with longitude phi(sub n) >= 220 +/- 10 deg, this would suggest strong hindrance to the propagation of shocks contra a rather tightly winding Parker spiral. Examination of the obliquity angle theta(sub Bn) (that between the shock normal and the upstream interplanetary magnetic field) for the full set of shocks revealed that about 58% was quasi-perpendicular, and some were very nearly perpendicular. About 32% of the shocks were oblique, and the rest (only 10%) were quasi-parallel, with one on Dec. 9, 1996 that showed field pulsations. Small uncertainty in the estimated angle theta(sub Bn) was obtained for about 10 shocks with magnetosonic Mach numbers between 1 and 2, hopefully significantly contributing to studies researching particle acceleration mechanisms at IP shocks, and to investigations where accurate values of theta(sub Bn) are crucial.

  17. Unraveling Flow Patterns through Nonlinear Manifold Learning

    PubMed Central

    Tauro, Flavia; Grimaldi, Salvatore; Porfiri, Maurizio

    2014-01-01

    From climatology to biofluidics, the characterization of complex flows relies on computationally expensive kinematic and kinetic measurements. In addition, such big data are difficult to handle in real time, thereby hampering advancements in the area of flow control and distributed sensing. Here, we propose a novel framework for unsupervised characterization of flow patterns through nonlinear manifold learning. Specifically, we apply the isometric feature mapping (Isomap) to experimental video data of the wake past a circular cylinder from steady to turbulent flows. Without direct velocity measurements, we show that manifold topology is intrinsically related to flow regime and that Isomap global coordinates can unravel salient flow features. PMID:24614890

  18. Science Nation: Unraveling the Mysteries of Tornadoes

    NSDL National Science Digital Library

    To better understand tornadoes, scientists, with the help of the National Science Foundation, are embarking on a quest to unravel the mysteries of tornadoes. The project is called VORTEX2, but it could also be called the amazing chase. For five weeks in the spring of 2009, and again in spring 2010, 100 researchers and scientists from 16 universities will deploy about 40 vehicles armed with high tech equipment to measure and probe tornadoes and tornado development. The researchers will span across the Midwest in search of tornadoes--all to better understand how, when and why they form.

  19. Unravelling the Value Chain in Construction Proceedings IGLC `98

    E-print Network

    Tommelein, Iris D.

    Unravelling the Value Chain in Construction Proceedings IGLC `98 UNRAVELLING THE VALUE CHAIN Process modelling, functional modelling, design, supply chain, value chain, IT. 1 Professor different project scenarios so that non-value added activities can be isolated and eliminated. KEY WORDS

  20. Elastic thickness estimates for coronae associated with chasmata on Venus

    Microsoft Academic Search

    Trudi Hoogenboom; Greg Houseman; Paula Martin

    2005-01-01

    In this study we investigate the relationship between the local elastic lithospheric thickness and the relative ages of coronae on Venus in an attempt to further understand corona and chasmata formation\\/evolution. We use Magellan gravity and topography data to estimate the elastic lithospheric thickness in the vicinity of coronae associated with chasmata. The relative timing of corona formation with respect

  1. The helium shells of HeI and HeII at solar minimum: New results from eclipse flash spectra of 2008- 2010

    NASA Astrophysics Data System (ADS)

    Bazin, C.; Koutchmy, S.; Lamy, P.

    2011-12-01

    Flash spectra taken at high frame rate during the total solar eclipse of August 1st 2008 in Siberia and during the July 11th 2010 in French Polynesia are compared in the context of the quiet Sun near the minimum of activity. They both reveal the weak Paschen ? 468.6 nm ionized helium line, seen as a helium shell in layers up to the 8 Mm heights. The preliminary evaluated effective height of the He I 4713 shell is 1.8 Mm and it is approximately 2.0 Mm for the He II 4686 emissions outside polar regions. These lines can be measured only in eclipse conditions, when the parasitic scattered light is negligible for very low solar fluxes corresponding to the coronal levels. Many faint lines are also seen in emission such as Ba +, Ti +, Fe +, but with a much lower radial extension. They were observed to be superposed to F-lines when defining the solar limb using the continuum background. A cartoon is proposed to describe the structuration of these low layers and to illustrate the contribution of the magnetic field. These observations are important new insights for understanding (i) the magnetic field inference in the very low layers of the solar transition region and (ii) the ionisation mechanisms producing the big jump of the temperature towards the corona, including the source of heating.

  2. Models for Stellar Coronae - Comparison with the Minimum Flux Corona Theory

    NASA Astrophysics Data System (ADS)

    Vardavas, I. M.; Hearn, A. G.

    1981-05-01

    Coronal models calculated using the iterative two boundary value method of solution (Hearn and Vardavas, 1981) are compared with the predictions of the minimum flux corona theory applied to an isothermal, spherically symmetric corona (Hearn, 1975). For those coronal models for which an isothermal corona is a reasonable approximation, the minimum flux corona theory predicts the pressure of the transition region for a given flux of mechanical energy to within 30%. It predicts average coronal temperatures which are within 11% of the energy weighted average coronal temperatures calculated for the models. The minimum flux corona theory overestimates the mechanical flux needed to yield a given mass loss from the corona by a factor of 3. Although these calculations are somewhat limited in range they show that the minimum flux corona theory is consistent with a corona heated by a mechanism which is specified in detail, contrary to the criticisms of Endler et al. (1979) and Mangeney and Souffrin (1979). Further, these calculations show that for a dissipation mechanism which is specified in detail, the minimum flux corona theory may be used to predict to within 30% the flux of mechanical energy at the transition region.

  3. Corona-A Brief Status Report

    Microsoft Academic Search

    C. F. Gallo

    1977-01-01

    Relevant to many practical applications [1] including xerography [2]-[9], the various forms of gas discharge which can occur in asymmetrical gaps (for example, needle-to-plane geometry) have been briefly summarized in this status report. Due to its engineering importance, emphasis have been placed upon corona in atmospheric air, particularly l) the positive glow corona, especially the emerging controversy concerning the role

  4. Streamer mechanism for negative corona current pulses

    Microsoft Academic Search

    Mirko Cernák; Tatsuzo Hosokawa; Shigeo Kobayashi; Teruo Kaneda

    1998-01-01

    Current wave forms of initial stages of breakdown and corona formation in a short negative point-to-plane gap have been measured with a nanosecond time resolution in air, O2, and N2 at pressures 13.33-100 kPa, and at various overvoltages. The experiments revealed the existence of a stepped form of negative corona Trichel pulses in O2 at atmospheric pressure. To test existing

  5. Corona Associations and Their Implications for Venus

    USGS Publications Warehouse

    Chapman, M.G.; Zimbelman, J.R.

    1998-01-01

    Geologic mapping principles were applied to determine genetic relations between coronae and surrounding geomorphologic features within two study areas in order to better understand venusian coronae. The study areas contain coronae in a cluster versus a contrasting chain and are (1) directly west of Phoebe Regio (quadrangle V-40; centered at latitude 15??S, longitude 250??) and (2) west of Asteria and Beta Regiones (between latitude 23??N, longitude 239?? and latitude 43??N, longitude 275??). Results of this research indicate two groups of coronae on Venus: (1) those that are older and nearly coeval with regional plains, and occur globally; and (2) those that are younger and occur between Beta, Atla, and Themis Regiones or along extensional rifts elsewhere, sometimes showing systematic age progressions. Mapping relations and Earth analogs suggest that older plains coronae may be related to a near-global resurfacing event perhaps initiated by a mantle superplume or plumes. Younger coronae of this study that show age progression may be related to (1) a tectonic junction of connecting rifts resulting from local mantle upwelling and spread of a quasi-stationary hotspot plume, and (2) localized spread of post-plains volcanism. We postulate that on Venus most of the young, post-resurfacing coronal plumes may be concentrated within an area defined by the bounds of Beta, Atla, and Themis Regiones. ?? 1998 Academic Press.

  6. Unraveling the miswired connectome: a developmental perspective.

    PubMed

    Di Martino, Adriana; Fair, Damien A; Kelly, Clare; Satterthwaite, Theodore D; Castellanos, F Xavier; Thomason, Moriah E; Craddock, R Cameron; Luna, Beatriz; Leventhal, Bennett L; Zuo, Xi-Nian; Milham, Michael P

    2014-09-17

    The vast majority of mental illnesses can be conceptualized as developmental disorders of neural interactions within the connectome, or developmental miswiring. The recent maturation of pediatric in vivo brain imaging is bringing the identification of clinically meaningful brain-based biomarkers of developmental disorders within reach. Even more auspicious is the ability to study the evolving connectome throughout life, beginning in utero, which promises to move the field from topological phenomenology to etiological nosology. Here, we scope advances in pediatric imaging of the brain connectome as the field faces the challenge of unraveling developmental miswiring. We highlight promises while also providing a pragmatic review of the many obstacles ahead that must be overcome to significantly impact public health. PMID:25233316

  7. Heating of the stellar corona

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1986-01-01

    The present state of development of the theory of coronal heating is summarized. Coronal heating is the general cause of stellar X-ray emission, and it is also the cause of stellar mass loss in most stars. Hence a quantitive theory of coronal heating is an essential part of X-ray astronomy, and the development of a correct theory of coronal heating should be a primary concern of X-ray astronomers. The magnetohydrodynamical effects involved in coronal heating are not without interest in their own right, representing phenomena largely unknown in the terrestrial laboratory. Until these effects can be evaluated and assembled into a comprehensive theory of coronal heating for at least one star, the interpretation of the X-ray emissions of all stars is a phenomenological study at best, based on arbitrary organization and display of X-ray luminosity against bolometric luminosity, rotation rate, etc. The sun provides the one opportunity to pursue the exotic physical effects that combine to heat a stellar corona.

  8. Influence of aged conductor surface conditions on AC corona discharge with a corona cage

    Microsoft Academic Search

    Xingming Bian; Deming Yu; Lan Chen; J. M. K. MacAlpine; Liming Wang; Zhicheng Guan; Fangdong Chen

    2011-01-01

    Relatively little investigation has previously been done on the effects of aging on conductor surface conditions, or on the ac corona discharges from these conductors. In the present work these were investigated by means of comparing corona on typical aged conductors with that on new ones. The aged conductors from the ac power transmission lines had been in service for

  9. Mapping the Solar Wind from its Source Region into the Outer Corona

    NASA Technical Reports Server (NTRS)

    Esser, Ruth; Wagner, William J. (Technical Monitor)

    2000-01-01

    The solar wind not only forms the space environment of Earth and other planets, but is also the cause of many phenomena observed in the Earth's atmosphere, such as aurorae. The expansion of the coronal plasma of the Sun is characteristic to many main sequence stars, and thus provides an example for understanding stellar winds as well. In spite of its importance for both space science and stellar physics, basic solar wind properties remain essentially unresolved. Since its discovery about 50 years ago, the complexity of the Sun corona - solar wind system has complicated the interpretation of observations. Recent progress in remote sensing observations as provided for example by YOHKOH, SOHO, SPARTAN and ULYSSES as well as some ground based techniques such as Interplanetary Scintillation observations, offer a compelling opportunity to unravel the 50 year old puzzle regarding the heat source or sources that cause the expansion of the solar corona. The new era of solar wind observations initiated by SOHO and ULYSSES, have also led to a wealth of new theoretical approaches. The goal of the proposed research was to carry out an integrated study of the coronal and solar wind plasma making use of the opportunities provided by the above spacecraft, as well as plasma emission calculations and new ideas on solar wind expansion theory.

  10. Complementary analysis of the hard and soft protein corona: sample preparation critically effects corona composition

    NASA Astrophysics Data System (ADS)

    Winzen, S.; Schoettler, S.; Baier, G.; Rosenauer, C.; Mailaender, V.; Landfester, K.; Mohr, K.

    2015-02-01

    Here we demonstrate how a complementary analysis of nanocapsule-protein interactions with and without application media allows gaining insights into the so called hard and soft protein corona. We have investigated how both human plasma and individual proteins (human serum albumin (HSA), apolipoprotein A-I (ApoA-I)) adsorb and interact with hydroxyethyl starch (HES) nanocapsules possessing different functionalities. To analyse the hard protein corona we used sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and a protein quantitation assay. No significant differences were observed with regards to the hard protein corona. For analysis of the soft protein corona we characterized the nanocapsule-protein interaction with isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). DLS and ITC measurements revealed that a high amount of plasma proteins were adsorbed onto the capsules' surface. Although HSA was not detected in the hard protein corona, ITC measurements indicated the adsorption of an HSA amount similar to plasma with a low binding affinity and reaction heat. In contrast, only small amounts of ApoA-I protein adsorb to the capsules with high binding affinities. Through a comparison of these methods we have identified ApoA-I to be a component of the hard protein corona and HSA as a component of the soft corona. We demonstrate a pronounced difference in the protein corona observed depending on the type of characterization technique applied. As the biological identity of a particle is given by the protein corona it is crucial to use complementary characterization techniques to analyse different aspects of the protein corona.Here we demonstrate how a complementary analysis of nanocapsule-protein interactions with and without application media allows gaining insights into the so called hard and soft protein corona. We have investigated how both human plasma and individual proteins (human serum albumin (HSA), apolipoprotein A-I (ApoA-I)) adsorb and interact with hydroxyethyl starch (HES) nanocapsules possessing different functionalities. To analyse the hard protein corona we used sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and a protein quantitation assay. No significant differences were observed with regards to the hard protein corona. For analysis of the soft protein corona we characterized the nanocapsule-protein interaction with isothermal titration calorimetry (ITC) and dynamic light scattering (DLS). DLS and ITC measurements revealed that a high amount of plasma proteins were adsorbed onto the capsules' surface. Although HSA was not detected in the hard protein corona, ITC measurements indicated the adsorption of an HSA amount similar to plasma with a low binding affinity and reaction heat. In contrast, only small amounts of ApoA-I protein adsorb to the capsules with high binding affinities. Through a comparison of these methods we have identified ApoA-I to be a component of the hard protein corona and HSA as a component of the soft corona. We demonstrate a pronounced difference in the protein corona observed depending on the type of characterization technique applied. As the biological identity of a particle is given by the protein corona it is crucial to use complementary characterization techniques to analyse different aspects of the protein corona. Electronic supplementary information (ESI) available: Pierce 660 nm protein assay, ITC data evaluation, DLS data evaluation, autocorrelation functions of protein - HES capsule mixtures. See DOI: 10.1039/c4nr05982d

  11. Unraveling environmental histories from skeletal diaries --Advances in sclerochronology

    E-print Network

    Schöne, Bernd R.

    Preface Unraveling environmental histories from skeletal diaries -- Advances in sclerochronology and INCREMENTS Research Group, Earth System Science Research Center, Institute of Geosciences, University formed skeletal hard parts provide a means to place the proxy record in a precise temporal context

  12. Solar cycle variations in F-region Te in the vicinity of the midlatitude trough based on AE-C measurements at solar minimum and DE-2 measurements at solar maximum

    NASA Technical Reports Server (NTRS)

    Brace, Larry H.

    1990-01-01

    Magnetospheric energy deposited in the plasmasphere produces large enhancements in the electron temperature in the nightside ionosphere at the foot of the geomagnetic L shell that traverses the plasmapause. This temperature peak, which is associated with the midlatitude trough in electron density, often has a great enough amplitude to produce 630 nm emission known as a Sar-arc. The Atmosphere Explorer-C measurements made at solar minimum and the Dynamics Explorer-2 measurements made at solar maximum are used to illustrate how this signature of F-region electron heating changes with solar activity. Global empirical models of the electron temperature and density have not been able to resolve these features thus far because of their large movements with geomagnetic activity and because of the large bin sizes used in the models. It is not yet clear how this major feature of the F-region temperature structure could be included easily in the IRI model.

  13. Dynamics of the coronas of open star clusters

    NASA Astrophysics Data System (ADS)

    Danilov, V. M.; Putkov, S. I.; Seleznev, A. F.

    2014-12-01

    A method for distinguishing coronas in models of open star clusters is proposed. The method uses trajectories of stars that do not leave the coronas over time intervals t comparable to the mean lifetime ? of the clusters. Corona models are constructed for six numerical cluster models, and the direction and character of the dynamical evolution of the coronas are determined. Retrograde stellar motions are dominant in the coronas. In spite of some signs of dynamical instability of the coronas (small densities compared to the critical density and accelerated expansion of the coronas), the formation of close-toequilibrium density and phase-density distributions at distances from one to three cluster tidal radii from the cluster center can be seen. Approximations are constructed for the corona and cluster phase density using distributions that depend on three parameters (the parameters of the stellar motion in the Lindblad rotating coordinate system). This temporary equilibrium of the corona is due to balance in the number of starsmoving from the central areas of the cluster to the corona, and from the corona to the corona periphery or beyond. Evidence that corona stars can be gravitationally bound at distances out to four tidal radii from the cluster center is found: the presence of nearly periodic retrograde mean motions of a large number of corona stars in the Galactic plane; 91-99% of corona stars satisfy the gravitational binding criterion of Ross, Mennim and Heggie over time intervals that are close to the mean cluster lifetime. The escape rate from the corona is estimated for t ? ?, and found to be from 0.03 to 0.23 of the number of corona stars per violent relaxation time.

  14. Coronas and iridescence in mountain wave clouds.

    PubMed

    Shaw, Joseph A; Neiman, Paul J

    2003-01-20

    We use Fraunhofer diffraction theory and meterological data to determine the nature of cloud-particle distributions and the mean particle sizes required for interpreting photographs of coronas and iridescence in mountain wave clouds. Traditional descriptions of coronas and iridescence usually explain these optical phenomena as diffraction by droplets of liquid water. Our analysis shows that the photographed displays have mean particle sizes from 7.6 to 24.3 microm, with over half the cases requiring diffraction by small (approximatley 20 microm) quasispherical ice particles rather than liquid water droplets. Previous documentation of coronas produced by ice particles are limited to observations in cirrus clouds that appear to be composed of small ice crystals, whereas our observations suggest that coronas and iridescence quite often can be created by tiny quasispherical ice particles that might be unique to mountain wave clouds. Furthermore, we see that the dominant colors in mountain wave-cloud coronas are red and blue, rather than the traditionally described red and green. PMID:12570269

  15. CITY OF CORONA OFFICE OF THE CITY CLERK

    E-print Network

    FOR CORONA DEPARTMENT OF WATER AND POWER IN FURTHERANCE OF RESOLUTION NO. 2012-013 AND AUTHORIZING THE TAKING call the Corona Department of Water and Power (DWP) at (951) 736-2232. Lisa Mobley, Chief Deputy City

  16. TRIANGLE-SHAPED DC CORONA DISCHARGE DEVICE FOR MOLECULAR DECOMPOSITION

    EPA Science Inventory

    The paper discusses the evaluation of electrostatic DC corona discharge devices for the application of molecular decomposition. A point-to-plane geometry corona device with a rectangular cross section demonstrated low decomposition efficiencies in earlier experimental work. The n...

  17. Unraveling the complex metabolic nature of astrocytes

    PubMed Central

    Bouzier-Sore, Anne-Karine; Pellerin, Luc

    2013-01-01

    Since the initial description of astrocytes by neuroanatomists of the nineteenth century, a critical metabolic role for these cells has been suggested in the central nervous system. Nonetheless, it took several technological and conceptual advances over many years before we could start to understand how they fulfill such a role. One of the important and early recognized metabolic function of astrocytes concerns the reuptake and recycling of the neurotransmitter glutamate. But the description of this initial property will be followed by several others including an implication in the supply of energetic substrates to neurons. Indeed, despite the fact that like most eukaryotic non-proliferative cells, astrocytes rely on oxidative metabolism for energy production, they exhibit a prominent aerobic glycolysis capacity. Moreover, this unusual metabolic feature was found to be modulated by glutamatergic activity constituting the initial step of the neurometabolic coupling mechanism. Several approaches, including biochemical measurements in cultured cells, genetic screening, dynamic cell imaging, nuclear magnetic resonance spectroscopy and mathematical modeling, have provided further insights into the intrinsic characteristics giving rise to these key features of astrocytes. This review will provide an account of the different results obtained over several decades that contributed to unravel the complex metabolic nature of astrocytes that make this cell type unique. PMID:24130515

  18. Stellar Coronae: The First Twenty - Five Years

    NASA Technical Reports Server (NTRS)

    Drake, Jeremy

    2000-01-01

    Hot X-ray emitting coronae were detected on stars other than the Sun about twenty-five years ago. Within only a few years of the first detections, the Einstein Observatory had mapped out coronal activity across the HR diagram. These observations provided the foundations for a coarse theoretical understanding of the physical mechanisms responsible for hot coronae on stars that has changed relatively little in the intervening years: plasma trapped in magnetic structures generated by dynamo processes somewhere beneath the photosphere is heated by as yet unidentified mechanisms that appear to transfer kinetic energy from underlying convective regions of the stellar envelope into the outer atmosphere. This review will describe the observational advances that have lead to some further theoretical understanding of stellar coronae, including the first results from high resolution X-ray spectroscopy obtained by Chandra and XMM-Newton, and will highlight the observational directions needed to make further progress.

  19. Double streamer phenomena in atmospheric pressure low frequency corona plasma

    SciTech Connect

    Kim, Dan Bee; Jung, H.; Gweon, B.; Choe, Wonho [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2010-07-15

    Time-resolved images of an atmospheric pressure corona discharge, generated at 50 kHz in a single pin electrode source, show unique positive and negative corona discharge features: a streamer for the positive period and a glow for the negative period. However, unlike in previous reports of dc pulse and low frequency corona discharges, multistreamers were observed at the initial time stage of the positive corona. A possible physical mechanism for the multistreamers is suggested.

  20. Device for generation of pulsed corona discharge

    DOEpatents

    Gutsol, Alexander F. (San Ramon, CA); Fridman, Alexander (Marlton, NJ); Blank, Kenneth (Philadelphia, PA); Korobtsev, Sergey (Moscow, RU); Shiryaevsky, Valery (Moscow, RU); Medvedev, Dmitry (Moscow, RU)

    2012-05-08

    The invention is a method and system for the generation of high voltage, pulsed, periodic corona discharges capable of being used in the presence of conductive liquid droplets. The method and system can be used, for example, in different devices for cleaning of gaseous or liquid media using pulsed corona discharge. Specially designed electrodes and an inductor increase the efficiency of the system, permit the plasma chemical oxidation of detrimental impurities, and increase the range of stable discharge operations in the presence of droplets of water or other conductive liquids in the discharge chamber.

  1. System for increasing corona inception voltage of insulating oils

    DOEpatents

    Rohwein, G.J.

    1998-05-19

    The Corona Inception Voltage of insulating oils is increased by repetitive cycles of prestressing the oil with a voltage greater than the corona inception voltage, and either simultaneously or serially removing byproducts of corona by evacuation and heating the oil. 5 figs.

  2. Original article Bovine cumulus expansion and corona-oocyte

    E-print Network

    Boyer, Edmond

    Original article Bovine cumulus expansion and corona-oocyte disconnection during culture in vitro J into 2 groups: complexes in which a dark rim of corona cells were visible around the zona pellucida (group 1and those in which the corona displayed the same density as the rest of the cumulus cell mass

  3. Unravelling the enigma of Perthes disease.

    PubMed

    Perry, D C

    2013-07-01

    Perthes disease is an idiopathic avascular necrosis of a juvenile hip. Although 2010 marked a century since it was first described, the aetiology remains unknown. It is suggested that adverse socioeconomic circumstances may be a key precipitant. This work describes recent studies that explore the disease epidemiology. Descriptive studies include a case register from Merseyside, hospital discharge data from Scotland, analysis of the world's largest community disease register (General Practice Research Database [GPRD]) and a systematic review of incidence. Analytical studies include a nested case-controlled study in the GPRD and a hospital case-controlled study. The studies demonstrated a striking north-south divide in the UK incidence of Perthes disease, similar to that seen in many adult diseases. There was a sustained fall in disease frequency in all studies, with a narrowing of the north-south divide. There was a strong association with area deprivation, independent of living in an urban environment. Internationally, equatorial regions were unaffected by disease and northern Europe had the highest incidence, which was primarily a function of race although latitude was an independent predictor. Individual characteristics associated with the disease were congenital anomalies of the genitourinary tract and a structural abnormality of arterial calibre. Despite a falling incidence, Perthes disease remains an important cause of child morbidity and exemplifies socioeconomic inequalities. A deprivation-related exposure, acting early in development, appears critical. The aetiological factor in Perthes disease remains elusive but it is likely that unravelling this enigma may unlock additional secrets pertaining to the developmental origins of this and other diseases. PMID:23838491

  4. Corona Discharge in Nuclear Excited Dusty Plasma

    SciTech Connect

    Deputatova, L. V.; Fortov, V. E.; Filinov, V. S.; Vladimirov, V. I.; Meshakin, V. I.; Rykov, V. A. [Joint Institute for High Temperatures RAS, Izhorskaya str. 13, bd. 2, Moscow (Russian Federation); Sinkevich, O. A. [Moscow Power Engineering Institute (Technical University) Krasnokazarmennaya str. 14, Moscow (Russian Federation)

    2011-11-29

    We considered the possibility of using a corona discharge in a nuclear excited dusty plasma to provide the stability of well ordered dusty plasma structures from a fissionable material and to accomplish a more efficient conversion of nuclear energy into radiation.

  5. The quiet corona: Temperature and temperature gradient

    Microsoft Academic Search

    S. J. Bame; J. R. Asbridge; W. C. Feldman; P. D. Kearney

    1974-01-01

    A study of the lower corona thermal properties was made using the best examples of solar wind heavy ion spectra obtained with Vela 5 and 6 plasma analyzers at times of quiet solar wind (low speed, low temperature). The multiple Si and Fe ion species peaks in the spectra were fit with solutions of the ionization equilibrium equations to determine

  6. Point-to-Plane Corona Onsets

    Microsoft Academic Search

    William N. English; Leonard B. Loeb

    1949-01-01

    The effect of point material and point radius of curvature on positive and negative intermittent corona onset potentials has been studied with a point-to-plane gap in air at atmospheric pressure. The negative Trichel pulse onset strangely is independent of point material but does depend on point history and radius. This surprising result is shown to come from the circumstance that

  7. LABORATORY ANALYSIS OF BACK-CORONA DISCHARGE

    EPA Science Inventory

    The paper discusses an experimental research program to characterize back-corona generation and behavior in a range of environments and geometries common to electrostatic precipitators (ESPs). A wire-parallel plate device was used to monitor the intensity and distribution of back...

  8. PEGylated nanoparticles: protein corona and secondary structure

    NASA Astrophysics Data System (ADS)

    Runa, Sabiha; Hill, Alexandra; Cochran, Victoria L.; Payne, Christine K.

    2014-09-01

    Nanoparticles have important biological and biomedical applications ranging from drug and gene delivery to biosensing. In the presence of extracellular proteins, a "corona" of proteins adsorbs on the surface of the nanoparticles, altering their interaction with cells, including immune cells. Nanoparticles are often functionalized with polyethylene glycol (PEG) to reduce this non-specific adsorption of proteins. To understand the change in protein corona that occurs following PEGylation, we first quantified the adsorption of blood serum proteins on bare and PEGylated gold nanoparticles using gel electrophoresis. We find a threefold decrease in the amount of protein adsorbed on PEGylated gold nanoparticles compared to the bare gold nanoparticles, showing that PEG reduces, but does not prevent, corona formation. To determine if the secondary structure of corona proteins was altered upon adsorption onto the bare and PEGylated gold nanoparticles, we use CD spectroscopy to characterize the secondary structure of bovine serum albumin following incubation with the nanoparticles. Our results show no significant change in protein secondary structure following incubation with bare or PEGylated nanoparticles. Further examination of the secondary structure of bovine serum albumin, ?2-macroglobulin, and transferrin in the presence of free PEG showed similar results. These findings provide important insights for the use of PEGylated gold nanoparticles under physiological conditions.

  9. The solar corona on 31 July, 1981

    NASA Astrophysics Data System (ADS)

    Fisher, R. R.; Lacey, L. R.; Rock, K. A.; Yasukawa, E. A.; Sheeley, N. R., Jr.; Michels, D. J.; Howard, R. A.; Koomen, M. J.; Bagrov, A.

    1983-03-01

    Results of observations of the solar corona near or at the time of total eclipse, 31 July 1981, are presented. The High Altitude Observatory coronal eclipse camera and the MK-III K-coronameter were employed to record the lower portions of the corona, while the distribution of white light material above 3 solar radii was observed with the Naval Research Laboratory satellite coronagraph on P78-1. The coronal structure is described and the coronal active regions are identified using these data sets. It is found that the polar coronal holes, as developed at this time in the solar cycle, were offset from the poles of rotation and both were seen displaced eastward on the eclipse day. High altitude streamers are found in all three data sets, extending from the base of the corona outward to at least eight solar radii from the center of the sun. In addition, at least two transients were observed on the eclipse day, but it is likely that no transient was in progress during any observation along the eclipse path. A distribution of the white-light corona, derived from synoptic K-coronameter data, is also presented.

  10. Pulsed Corona in Air for Water PROEFSCHRIFT

    E-print Network

    Eindhoven, Technische Universiteit

    / waste water treatment / advanced oxidation processes / ozone / phenol / oxidation This research has been......................................................................22 2.2.1.4. Ozone for waste water treatmentPulsed Corona in Air for Water Treatment PROEFSCHRIFT ter verkrijging van de graad van doctor aan

  11. Recycling of the Solar Corona's Magnetic Field

    NASA Astrophysics Data System (ADS)

    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.

  12. Black hole accretion disks with coronae

    NASA Technical Reports Server (NTRS)

    Svensson, Roland; Zdziarski, Andrzej A.

    1994-01-01

    Observations suggest the existence of both hot and cold dark matter in the centers of active galactic nuclei. Recent spectral models require a major fraction of power to be dissipated in the hot matter. We study the case when the hot matter forms a corona around a standard cold alpha-disk. In particular, we investigate the case when a major fraction, f, of the power released when the cold matter accretes is transported to and dissipated in the corona. This has major effects on the cold disk, making it colder, more geometrically thin, denser, and having larger optical depths. One important consequence is the disappearance of the effectively optically thin zone as well as of the radiation pressure dominated zone for values of f sufficiently closed to unity. The disappearance of the radiation pressure dominated zone will result in a cold disk with only a gas pressure dominated zone that is stable against thermal and viscous instabilities. We also show that the pressure ( and the radiation) from the corona will only affect the surface layers of the cold disk. Our results disagree with those of other recent work on accretion disks with coronae. We find those works to be based on unphysical assumptions.

  13. Solar Corona Explorer: A mission for the physical diagnosis of the solar corona

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Mission objectives and spacecraft requirements for the Solar Corona Explorer (SCE), a proposed free flying, unmanned solar research craft to be tenatively launched in 1987, were defined. The SCE's purpose is to investigate structure, dynamics and evolution of the corona, globally and in the required physical detail, to study the close coupling between the inner corona and the heliosphere. Investigative objectives are: (1) to understand the corona as the source of varying interplanetary plasma and of varying solar X-ray and extreme ultraviolet fluxes; (2) to develop the capabilities to model the corona with sufficient precision to forecast the Earth's variable environment in space, on the scales from weeks to years; (3) to develop an understanding of the physical processes that determine the dynamics and physical state of the coronal plasma, particularly acceleration processes; and (4) to develop insight and test theory on the Sun applicable to stellar coronae and winds, and in particular, to understand why cool stars put such a large fraction of their energy into X-rays. Considered related factors are: (1) duration of the mission; (2) onboard measuring instrumentation; (3) ground support equipment and procedures; and (4) programs of interpretation and modeling.

  14. MASC: Magnetic Activity of the Solar Corona

    NASA Astrophysics Data System (ADS)

    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 orientation is primarily based on extrapolations from photospheric observations, not from direct measurements. These extrapolations require strong assumptions on critical but unobserved quantities and thus fail to accurately reproduce the complex topologies inferred from remote-sensing observations of coronal structures in white light, EUV, and X-rays. Direct measurements of the coronal magnetic field are also clearly identified by the international heliophysics community as a key element susceptible to lead to major breakthroughs in the understanding of our star. MASC is thus designed to answer the following top-level scientific questions: 1. What is the global magnetic field configuration in the corona? 2. What is the role of the magnetic field in the triggering of flares and CMEs? 3. What is the role of the magnetic field in the acceleration mechanisms of the solar winds? 4. What is the energy spectrum and in particular what are the highest energies to which charged particles can be accelerated in the solar corona? MASC will address these fundamental questions with a suite of instruments composed of an X-ray spectrometer, a UV / EUV imager, and a coronagraph working in the visible and at Lyman alpha. The spectrometer will provide information on the energetics of solar flares, in particular at very high energies of accelerated particles. The UV / EUV imager will provide constraints on the temperature of the flaring and non-flaring corona. The coronagraph will provide the number density of free electrons in the corona, maps of the outflow velocity of neutral hydrogen, and measurements of the coronal magnetic field, via the Hanle effect. These measurements will be performed at all steps of the flare-CME processes, thus providing a detailed picture of the solar coronal dynamics in the quiet and eruptive periods.

  15. Corona and Motor Voltage Interim Report

    SciTech Connect

    Hsu, J.S.

    2005-05-06

    It has been suggested that to meet the FreedomCAR objectives for cost, size, weight, efficiency, and reliability higher buss voltages be utilized in HEV and FC automotive applications. The reasoning is that since electric power is equal to the product of voltage and current for a given power a higher voltage and lower current would result in smaller cable and inverter switching components. Consequently, the system can be lighter and smaller. On the other hand, higher voltages are known to require better and thicker electrical insulation that reduce the available slot area for motor windings. One cause of slow insulation breakdown is corona that gradually erodes the insulation and shortens the life expectancy of the motor. This study reports on the results of a study on corona initiating voltages for mush-wound and bobbin-wound stators. A unique testing method is illustrated.

  16. Helium corona-assisted air discharge

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Gao, Lei; Ji, Ailing; Cao, Zexian

    2011-10-01

    Operation of atmospheric discharge of electronegative gases including air at low voltages yet without consuming any inert gas will enormously promote the application of non-thermal plasmas. By taking advantage of the low onset voltage for helium corona, air discharge was successfully launched at much reduced voltages with a needle-plate system partly contained in a helium-filled glass bulb—for a needle-plate distance of 12 mm, 1.0 kV suffices. Ultraviolet emission from helium corona facilitates the discharging of air, and the discharge current manifests distinct features such as relatively broad Trichel pulses in both half periods. This design allows safe and economic implementation of atmospheric discharge of electronegative gases, which will find a broad palette of applications in surface modification, plasma medicine and gas treatment, etc.

  17. Towards understanding of nanoparticle-protein corona.

    PubMed

    Ge, Cuicui; Tian, Jian; Zhao, Yuliang; Chen, Chunying; Zhou, Ruhong; Chai, Zhifang

    2015-04-01

    With the rapid developments of nanotechnology, chances of exposing nanoscale particles to humans (e.g., workers and consumers) also increase correspondingly, which raises serious concerns on their biosafety. Entrance of nanoparticles into diverse biological environment endows them with new and dynamic biological identities as the so-called nanoparticle-protein corona. Therefore, understanding the role of these nanoparticle-protein coronas and resulting biological responses is crucial, as it helps to clarify the biological mechanism and prevent the potential adverse effects of nanoparticles. In this review, we summarize the latest developments relating to the nanoparticle-protein interaction and corresponding biological responses, with an emphasis on the characterization methods, induced biological effects and possible molecular mechanisms. In addition, we overview both the challenges and opportunities (particularly in nanomedicine) raised by this entrance of nanoparticles into the living creatures, especially human beings, with some future perspectives based on our understanding. PMID:25637415

  18. Helium corona-assisted air discharge

    SciTech Connect

    Jiang Nan; Gao Lei; Ji Ailing; Cao Zexian [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2011-10-15

    Operation of atmospheric discharge of electronegative gases including air at low voltages yet without consuming any inert gas will enormously promote the application of non-thermal plasmas. By taking advantage of the low onset voltage for helium corona, air discharge was successfully launched at much reduced voltages with a needle-plate system partly contained in a helium-filled glass bulb--for a needle-plate distance of 12 mm, 1.0 kV suffices. Ultraviolet emission from helium corona facilitates the discharging of air, and the discharge current manifests distinct features such as relatively broad Trichel pulses in both half periods. This design allows safe and economic implementation of atmospheric discharge of electronegative gases, which will find a broad palette of applications in surface modification, plasma medicine and gas treatment, etc.

  19. Are Coronae Restricted to Venus?: Corona-Like Tectonovolcanic Structures on Earth

    NASA Astrophysics Data System (ADS)

    Lopez, Ivan; Marquez, Alvaro; Oyarzun, Roberto

    1997-04-01

    Coronae may not be tectonovolcanic features ‘unique to Venus’ because both the processes that lead to corona formation, and their final tectonovolcanic output (formation of domes, plateaus, extensional rings, etc.), are also found on Earth. Large-scale corona formation processes on Earth may be restricted (because of plate motion) but not absent. The same applies to resurfacing processes. We here suggest that at least, the early stages of corona formation can be recognized in intraplate tectonic settings on Earth. The African plate displays many Cenozoic examples of plume-related domal uplifts and volcanism (e.g., Hoggar, Tibesti, Darfur, Ethiopia). Furthermore, the east African rift system (EARS) around lake Victoria displays many striking features that resemble those of the Venus coronae associated with extensional belts. Among these are the following: (1) an overall elliptical shape; (2) the existence of a mantle plume (Kenya plume) centered beneath lake Victoria; (3) a central plateau (east African plateau); (4) an external extensional belt (the EARS east and west branches); (5) doming processes (Kenya dome); and last but not least (6) volcanism.

  20. Negative corona discharges: A fundamental study

    Microsoft Academic Search

    Bastiaan Gravendeel

    1987-01-01

    Negative corona discharge in air in the Trichel regime was studied using fast current measurements (resolution 0.7 ns), mass spectrometry, and fast light intensity measurements resolved with time resolution 0.7 ns, in space resolution 0.05 mm, and wavelength resolution 0.16 nm. A theoretical expression which relates the externally measured current with the movement of charges inside an inhomogeneous field gap

  1. Unraveling "Braid": Puzzle Games and Storytelling in the Imperative Mood

    ERIC Educational Resources Information Center

    Arnott, Luke

    2012-01-01

    "Unraveling Braid" analyzes how unconventional, non-linear narrative fiction can help explain the ways in which video games signify. Specifically, this essay looks at the links between the semiotic features of Jonathan Blow's 2008 puzzle-platform video game Braid and similar elements in Georges Perec's 1978 novel "Life A User's Manual," as well as…

  2. Unraveling Nanotubes: Field Emission from an Atomic Wire

    E-print Network

    · REPORTS Unraveling Nanotubes: Field Emission from an Atomic Wire A G. Rinzler, J. H. Hafner, P of electrons from individually mounted carbon nanotubes has been found to be dramatically enhanced when the nanotube tips are opened by laser evaporation or oxidative etching. Emission currents of 0.1 to 1

  3. Unraveling the racial disparities associated with kidney disease1

    Microsoft Academic Search

    Keith C. Norris; Lawrence Y. Agodoa

    2005-01-01

    Unraveling the racial disparities associated with kidney disease. In the United States, chronic kidney disease (CKD), and in particular end-stage renal disease (ESRD), represent a growing problem. Many other countries also have an increasing number of ESRD cases. Racial\\/ethnic disparities have been documented globally in the prevalence, incidence, and treatment of CKD, most extensively in the United States, but also

  4. COLD ACCRETION DISKS WITH CORONAE AND ADVECTION

    E-print Network

    Xingming Chen

    1995-02-03

    Cold optically thick accretion disks with hot coronae and radial advection have been investigated. Within the framework of $\\alpha$-viscosity models, we assume that all the mass accretion and angular momentum transport take place in the cold disk, but that a fraction of the gravitational energy released is dissipated in the corona. Both the coronal energy dissipation and the advection heat transport have a stabilization effect on the thermal and viscous instabilities of the disk. If that more than $\\sim 95$ percent of the total power is dissipated in the corona, then the locally unstable behavior of the disk is restricted to a relatively narrow spatial region and is found to lie in a small range of mass accretion rates. The global temporal variability of the disk can be very mild or may disappear, and which may be applicable to the low-frequency ($\\sim 0.04$~Hz) quasi-periodic oscillations observed in black hole candidates Cyg X--1 and GRO J0422+32.

  5. Turbulent photospheric drivers of multiscale solar corona

    NASA Astrophysics Data System (ADS)

    Uritsky, Vadim M.; Ofman, Leon; Davila, Joseph M.

    2015-04-01

    We investigate the collective dynamics of transient photospheric and coronal events detected using high-resolution solar magnetograms and coronal emission images. We focus on statistical, ensemble-averaged properties of the interacting solar regions [Uritsky et al., 2011, 2013, 2014; Uritsky and Davila, 2012], as opposed to case-oriented methodologies recruited in some previous studies. The behavior of solar events is studied in the three-dimensional space-time enabling accurate representation of the event evolution. By applying advanced data analysis methods including feature tracking algorithms, multiscale correlation analysis and scaling analysis techniques, we identify leading physical scenarios of the photosphere - corona coupling in quiet and active solar regions, and strive to identify new statistical precursors of coronal eruptions. We also discuss the possibility of modeling multiscale photosphere - corona interactions using idealized three-dimensional MHD models. The obtained results shed a new light on the origin of multiscale dissipation in the solar corona by enabling quantitative validation of several popular statistical physical scenarios, such as e.g. intermittent turbulence, self-organized criticality, and topological complexity.

  6. The Sparking Characteristics of Needle-To-Plane Coronas

    Microsoft Academic Search

    W. L. Lama; C. F. Gallo

    1976-01-01

    The sparking voltage (Vs) and maximum presparking corona current (Imax) of needle-to-plane coronas have been measured as independent functions of polarity, tip radius (r), and needle-to-plane spacing (S). For a negative needle, Vs and Imax increase with S but are independent of r. For positive polarity, Vs and Imax increase with both S and r. Thus to increase the corona

  7. Action of corona discharges on bacteria and spores

    Microsoft Academic Search

    R. S. Sigmond; B. Kurdelova; M. Kurdel

    1999-01-01

    We have measured the E.coli bactericidal efficiency of DC and AC point-to-plane coronas in air and in argon in the corona modes positive glow, positive streamer, negative Trichel pulse and negative glow. Negative Trichel pulse and positive streamer coronas are the most efficient for production of bactericidal agents in air. Less than 5 minute exposure to the products from 30

  8. Polarization studies of the solar corona on July 31, 1981.

    NASA Astrophysics Data System (ADS)

    Kulidzhanishvili, V. I.; Nikol'Skij, G. M.; Stepanov, A. I.; Suladze, A. S.; Khutsishvili, Eh. V.

    The solar corona continuous emission polarization features were studied on the basis of the measurements during the 31 July 1981 eclipse. During the total phase (74 s) the total radiation of the solar corona, the intensity of the linearly polarized component, the orientation of the polarization plane at 1700 points of the corona from 0.1 R_sun; to 6.5 R_sun; were investigated.

  9. Action of corona discharges on bacteria and spores

    NASA Astrophysics Data System (ADS)

    Sigmond, R. S.; Kurdelova, B.; Kurdel, M.

    1999-03-01

    We have measured the E.coli bactericidal efficiency of DC and AC point-to-plane coronas in air and in argon in the corona modes positive glow, positive streamer, negative Trichel pulse and negative glow. Negative Trichel pulse and positive streamer coronas are the most efficient for production of bactericidal agents in air. Less than 5 minute exposure to the products from 30 A of these coronas will sterilize the E.coli covered agar surfaces in a 3l volume to a survival ratio of 10-5. Positive glow coronas are two orders of magnitude less efficient. 50 Hz AC coronas seem to mainly work during the negative half cycles. The bactericidal agent(s) produced by the coronas have not all been identified, but ozone O3 with concentration 35-40 ppm is probably the most important one. We show that charged particles and photons can play only a minor role, so the agent(s) must be neutral particles. The main part of them must have a lifetime in the vessel of more than 3 minutes. The much smaller, and volume/distance dependent, efficiency of coronas in humid argon indicates that metastable neutrals or radicals from H2O can play only a minor role. A preliminary test showed negligible effects of the corona treatment on the spores of Bacillus subtilis.

  10. Deep solar minimum and global climate changes

    PubMed Central

    Hady, Ahmed A.

    2013-01-01

    This paper examines the deep minimum of solar cycle 23 and its potential impact on climate change. In addition, a source region of the solar winds at solar activity minimum, especially in the solar cycle 23, the deepest during the last 500 years, has been studied. Solar activities have had notable effect on palaeoclimatic changes. Contemporary solar activity are so weak and hence expected to cause global cooling. Prevalent global warming, caused by building-up of green-house gases in the troposphere, seems to exceed this solar effect. This paper discusses this issue. PMID:25685420

  11. Corona radiata density as a non-invasive marker of bovine cumulus-corona-oocyte complexes selected for in vitro embryo production

    Microsoft Academic Search

    J. Laurin?ík; P. Hyttel; V. Baran; F. Schmoll; H. Niemann; G. Brem; K. Schellander

    1996-01-01

    The density of the corona radiata as a marker for the quality of cumulus-corona-oocyte complexes (CCOC's) for in vitro embryo production was tested. The CCOC's in which the corona radiata appeared as a dark rim surrounding the zona pellucida (Group 1) and CCOC's in which the corona had the same density as the rest of the cumulus investment (Group 2)

  12. Observational Study of the Tridimensional Trajectory of Small White-Light Transients in the Inner Solar Corona

    NASA Astrophysics Data System (ADS)

    Lopez-Portela, C.; Blanco-Cano, X.; Stenborg, G.; Vourlidas, A.

    2013-05-01

    The physical mechanisms responsible for the low corona origin and subsequent interplanetary development of the small scale white-light transients, known as blobs, is relevant to the formation and acceleration mechanisms of the slow solar wind (Sheeley et al., 1997). Since they are considered to be reliable tracers of the slow solar wind, a statistical kinematical characterization of these faint features should provide to the understanding of its origins and acceleration. The vantage observing points provided by the SECCHI and LASCO imagers aboard the STEREO and SOHO missions, respectively, allows us to get a good estimation of their trajectory in the 3D space and hence perform a detailed analysis of their unprojected kinematical parameters. To address this issue, we have surveyed the SOHO/LASCO C2 and C3, and the STEREO/SECCHI COR 1 and COR 2 databases for the year 2007 through 2010 (i.e., a period comprising the declining phase of the extended past solar minimum and the ascending phase of cycle 24) and selected about 100 blob-like features. The selection of events was facilitated by the scarce presence of coronal mass ejection events during this period, and it was limited to ±30° from the Sun's equator. The restricted latitudinal range is inspired by the work of Wang et al. (1998), who proposed that blobs are liberated from the cusp of helmet steamers. Two methods have been considered for the determination of the 3D kinematical parameters: (1) the tie-pointing and triangulation technique (Thompson W.T., 2008) and (2) the Height-Time analysis as developed by Mierla et al. (2008). In this work, we report on the set of transients studied by both techniques, discuss the limitations encountered on the determination of the 3D trajectories, and explore their significance on understanding the physical mechanisms behind the generation/propagation of the slow solar wind.

  13. Igneous and tectonic evolution of Venusian and terrestrial coronae

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.; Komatsu, G.

    1992-01-01

    A great variety of tectonic and volcanic features have been documented on Venus. It is widely appreciated that there are close spatial associations among certain types of tectonic structures and some classes of volcanic flows and constructs. Coronae are endowed with a particularly rich variety of volcanism. It is thought that coupled tectonic and volcanic aspects of coronae are cogenetic manifestations of mantle plumes. An outstanding feature of most venusian coronae is their circular or elliptical shape defined by peripheral zones of fracturing and/or folding. Some coronae are composite, consisting of two or more small coronae within a larger enclosing corona, suggesting complex histories of structured diapirism analogous in some ways to salt dome tectonics. Coronae range widely in size, from smaller than 100 km to over 1000 km in diameter. Volcanic features associated with venusian coronae include lunar-like sinuous rilles, thin lava flows, cinder cone-like constructs, shield volcanos, and pancake domes. Several types of volcanic features are often situated within or near a single corona, in many instances including land-forms indicating effusions of both low- and high-viscosity lavas. In some cases stratigraphic evidence brackets emplacement of pancake domes during the period of tectonic development of the corona, thus supporting a close link between the igneous and tectonic histories of coronae. These associations suggest emplacement of huge diapirs and massive magmatic intrusions, thus producing the tectonic deformations defining these structures. Igneous differentiation of the intrusion could yield a range of lava compositions. Head and Wilson suggested a mechanism that would cause development of neutral buoyancy zones in the shallow subsurface of Venus, thereby tending to promote development of massive igneous intrusions.

  14. Fluorine in R Coronae Borealis Stars

    E-print Network

    Gajendra Pandey; David L. Lambert; N. Kameswara Rao

    2007-11-15

    Neutral fluorine (F I) lines are identified in the optical spectra of several R Coronae Borealis stars (RCBs) at maximum light. These lines provide the first measurement of the fluorine abundance in these stars. Fluorine is enriched in some RCBs by factors of 800 to 8000 relative to its likely initial abundance. The overabundances of fluorine are evidence for the synthesis of fluorine. These results are discussed in the light of the scenario that RCBs are formed by accretion of an He white dwarf by a C-O white dwarf. Sakurai's object (V4334 Sgr), a final He-shell flash product, shows no detectable F I lines.

  15. Back-Corona Discharge Phenomenon in the Nonthermal Plasma System

    Microsoft Academic Search

    Tomasz Czapka

    2011-01-01

    most reactors allow relatively low discharge intensity and highpressure drop between their inlets and outlets for proceeding gas to be obtained. This is a major problem, particularly in the systems for decomposition of volatile organic compounds from air streams. Back-corona discharge phenomenon can be applied in the reactors to increase discharge current and, finally, plasma density. Back-corona discharge phenomenon was

  16. Turbulent heating of the corona and solar wind: the heliospheric

    E-print Network

    Turbulent heating of the corona and solar wind: the heliospheric dark energy problem Stuart D. Bale that the gas is highly ionized, i.e. a magnetized collisionless plasma ( solar wind model A `solar wind' is accelerated from the corona - Hydrostatic solution (similar to Bondi accretion

  17. A magmatic loading model for coronae on Venus

    Microsoft Academic Search

    Andrew J. Dombard; Catherine L. Johnson; Mark A. Richards; Sean C. Solomon

    2007-01-01

    Models for the formation of coronae, quasi-circular, volcanotectonic features on Venus, must explain four critical characteristics: coronae display (1) a wide range of diameters, (2) complex, varied topography, (3) fracture annuli, and (4) sometimes extensive volcanism. Previous models have difficulty simultaneously satisfying all four constraints. On the basis of observations and interpretations of features on Venus and Earth and experiments

  18. Theory of stepped pulses in negative corona discharges

    Microsoft Academic Search

    R. Morrow

    1985-01-01

    Theoretical calculations are presented which account for the development of the step observed on the leading edge of the current pulse in a negative point-plane corona (Trichel pulse). The theory explains the step in terms of independent photon and ion secondary processes at the cathode. It is applied specifically to describe the shape of an experimentally determined corona current pulse

  19. RAPID COMMUNICATION: Trichel pulses in negative corona discharge on trees

    Microsoft Academic Search

    L. Aubrecht; J. Koller; A. Zahoranova

    1999-01-01

    In this article we present the results of an experimental study of negative corona pulses in air at atmospheric pressure. New, more complex waveforms of pulses in discharge on trees and plants (pine, spruce) are found and compared with waveforms measured in a classical negative corona with metal electrodes. It is also found that the repetition rate of negative plant

  20. Onset voltage of negative corona on stranded conductors

    Microsoft Academic Search

    M. M. El-Bahy; M. Abouelsaad; N. Abdel-Gawad; M. Badawi

    2007-01-01

    Theoretical investigation of the onset voltage of negative corona on stranded conductors is described in this paper. The method of calculation is based on the criterion developed for the formation of repetitive negative corona Trichel pulses. This calls first for an accurate calculation of the electric field in the vicinity of stranded conductors. The investigated gap is a three-dimensional field

  1. Corona in atmospheric air between negative point and plane electrodes

    Microsoft Academic Search

    G. R. Gurumurthy; J. Amarnath; B. R. Natarajan

    2004-01-01

    The phenomena of corona between negative point and plane electrodes in atmospheric air have been found to consist of Trichel pulses above onset. Results of experimental investigations on negative point plane corona in air at atmospheric pressure for DC voltage applications are reported in this paper. The diameter of the hemispherical tip used in these investigations varied from 1.0 mm

  2. Multiple-needle corona electrodes for electrostatic processes application

    Microsoft Academic Search

    Lucian Dascalescu; Adrian Samuila; Dan Rafiroiu; Alexandru Iuga; Roman Morar

    1999-01-01

    Corona from high-voltage electrodes is employed in various electrostatic installations, such as ozonizers, air filters, powder sprayers and separators. Multiple-needle electrode designs are preferred whenever low corona onset voltage and good resistance to mechanical shocks are required. This paper aims at identifying a simple solution to overcome the main drawback of this type of electrode, the nonuniformity of the generated

  3. Rings Around the Sun and Moon: Coronae and Diffraction

    ERIC Educational Resources Information Center

    Cowley, Les; Laven, Philip; Vollmer, Michael

    2005-01-01

    Atmospheric optical effects can teach much about physics and especially optics. Coronae--coloured rings around the sun or moon--are large-scale consequences of diffraction, which is often thought of as only a small effect confined to the laboratory. We describe coronae, how they are formed and experiments that can be conducted on ones in the sky.…

  4. Electrical Characterization of a Corona Discharge for Surface Treatment

    Microsoft Academic Search

    Louis A. Rosenthal; Donald A. Davis

    1975-01-01

    Electrical characterization is based on a display of voltage and charge which appears as a simple parallelogram. The area is a measure of energy input per cycle and is independent of voltage waveform but very dependent on the maximum voltage. A useful model for such corona discharges employs a Zener diode to simulate the corona drop. The buffer dielectric plays

  5. On stabilization of multipoint negative corona by using ballast resistances

    NASA Astrophysics Data System (ADS)

    Baldanov, B. B.

    2009-08-01

    The I-V characteristics of a negative corona discharge initiated by a multipoint cathode in an argon flow are experimentally studied. It is found that adjustable ballast resistances connected to the corona points provide stable operation and uniform filling of the discharge gap by the plasma.

  6. Mass and energy flow in the solar chromosphere and corona

    Microsoft Academic Search

    G. L. Withbroe; R. W. Noyes

    1977-01-01

    Some results of investigations into the mass and energy flow in the solar chromosphere and corona are reviewed. The objective of these investigations is the development of a physical model that will not only account for the physical conditions in the outer atmosphere of the sun but also can be applied to the study of the chromospheres and coronae of

  7. Petrovay: Solar physics Chromosphere and corona THE SOLAR CHROMOSPHERE

    E-print Network

    Petrovay, Kristóf

    Petrovay: Solar physics Chromosphere and corona THE SOLAR CHROMOSPHERE Visible in eclipses as red.) The quiet chromosphere Lower boundary: T-minimum at z = 500 km (T = 4200K, = 10-13 g/cm3 ) Upper boundary brightness temperature at 10.7 cm: Tb 10 000 K. #12;Petrovay: Solar physics Chromosphere and corona Mean

  8. Analysis of Corona Discharge Interference on Antennas on Composite Airplanes

    Microsoft Academic Search

    Huan-Zhan Fu; Yong-Jun Xie; Jun Zhang

    2008-01-01

    Static electrification of the airframe can often cause electromagnetic interference on aircraft radios. Triboelectric charging, occurring when an aircraft is operated in precipitation, raises the aircraft potential until corona discharges occur from points of high dc field on the aircraft. These corona discharges generate noise that is coupled into antenna systems installed on the aircraft. The characteristics of electrostatic accumulation

  9. Coronae formation on Venus via extension and lithospheric instability

    NASA Astrophysics Data System (ADS)

    Piskorz, Danielle; Elkins-Tanton, Linda T.; Smrekar, Suzanne E.

    2014-12-01

    Over 500 quasi-circular volcano-tectonic features called coronae occur on Venus. They are believed to form via small-scale mantle upwellings, lithospheric instability, or a combination thereof. Coronae and rifts commonly occur together, including many coronae that lie outside of the fracture zone. However, the genetic link between the two has remained unclear. This paper proposes a mechanism for the formation of off-rift coronae due to the rifting process. We model the interaction of a rising mantle plume associated with a rift with a hypothetical preexisting layer of dense material in the lithosphere. We show that a rift and its associated off-rift coronae could be genetically linked by the process of development of secondary ringlike dripping instabilities initiating at the plume margins. We calculate the resulting surface topographies, melt volumes, and Bouguer gravity anomalies and compare them to observations.

  10. Development of ac corona discharge modes at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    El-Koramy, Reda Ahmed; Yehia, Ashraf; Omer, Mohamed

    2011-02-01

    Corona discharges in gases exist under several distinctive forms. In this paper, a survey study has been made of ac corona discharge modes generated in some different gases fed in a wire-duct reactor with a constant rate of flowing at atmospheric pressure. The properties of different corona modes are analyzed under some condition transitions from Trichel pulses to a steady glow. In the course of the presented experimental work, numerous apparent contradictions with earlier observations necessitated further study and are given to provide more information on the physical mechanisms of the ac corona discharges. Furthermore, we have gained insight into some new technologies and applications of the environmentally friendly corona and plasma discharges.

  11. Rapid formation of plasma protein corona critically affects nanoparticle pathophysiology

    NASA Astrophysics Data System (ADS)

    Tenzer, Stefan; Docter, Dominic; Kuharev, Jörg; Musyanovych, Anna; Fetz, Verena; Hecht, Rouven; Schlenk, Florian; Fischer, Dagmar; Kiouptsi, Klytaimnistra; Reinhardt, Christoph; Landfester, Katharina; Schild, Hansjörg; Maskos, Michael; Knauer, Shirley K.; Stauber, Roland H.

    2013-10-01

    In biological fluids, proteins bind to the surface of nanoparticles to form a coating known as the protein corona, which can critically affect the interaction of the nanoparticles with living systems. As physiological systems are highly dynamic, it is important to obtain a time-resolved knowledge of protein-corona formation, development and biological relevancy. Here we show that label-free snapshot proteomics can be used to obtain quantitative time-resolved profiles of human plasma coronas formed on silica and polystyrene nanoparticles of various size and surface functionalization. Complex time- and nanoparticle-specific coronas, which comprise almost 300 different proteins, were found to form rapidly (<0.5 minutes) and, over time, to change significantly in terms of the amount of bound protein, but not in composition. Rapid corona formation is found to affect haemolysis, thrombocyte activation, nanoparticle uptake and endothelial cell death at an early exposure time.

  12. Density Stratification of the Very Hot Corona of YY Mensae

    NASA Astrophysics Data System (ADS)

    Guedel, Manuel

    2001-09-01

    Chandra HETGS observations give access to a number of He-like line triplets that are sensitive to the density of hot coronal plasma. The present proposal requests observing time on an outstanding single star that has revealed an extremely hot and luminous corona. We aim at measuring the density structure of its corona together with its anomalous abundances. The target, YY Mensae, reveals a corona in which 90 percent of the emission measure resides at 30-40 MK. It has been suggested that such coronae are heated by statistical flares. A thorough spectroscopic study of this object could decide on whether its corona is indeed composed of numerous high-density compact flaring loops. The emission measure distribution will be studied to investigate whether it is generated by frequent flaring.

  13. Isothermal, Compton-heated coronae above accretion disks

    NASA Technical Reports Server (NTRS)

    Ostriker, Eve C.; Mckee, Christopher F.; Klein, Richard I.

    1991-01-01

    The structure of Compton-heated coronae above accretion disks is studied here by using analytic and numerical approaches are used here to determine the direct and scattered radiation reaching the base of the corona for a range of central source luminosities. It is found that the outer region of the corona is unaffected by multiple scattering in the interior, provided that the luminosity of the central source is sufficient below the Eddington limit. How attenuation and scattering by the corona affects the strength of chromospheric emission lines is determined, as is the condition for which the irradiation due to the central source exceeds the locally generated flux from the disk. Finally, it is shown that the stability analysis for irradiated accretion disks of Tuchman et al. is not substantially altered by the corona.

  14. R Coronae Australis: A Cosmic Watercolour

    NASA Astrophysics Data System (ADS)

    2010-06-01

    This magnificent view of the region around the star R Coronae Australis was created from images taken with the Wide Field Imager (WFI) at ESO's La Silla Observatory in Chile. R Coronae Australis lies at the heart of a nearby star-forming region and is surrounded by a delicate bluish reflection nebula embedded in a huge dust cloud. The image reveals surprising new details in this dramatic area of sky. The star R Coronae Australis lies in one of the nearest and most spectacular star-forming regions. This portrait was taken by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. The image is a combination of twelve separate pictures taken through red, green and blue filters. This image shows a section of sky that spans roughly the width of the full Moon. This is equivalent to about four light-years at the distance of the nebula, which is located some 420 light-years away in the small constellation of Corona Australis (the Southern Crown). The complex is named after the star R Coronae Australis, which lies at the centre of the image. It is one of several stars in this region that belong to the class of very young stars that vary in brightness and are still surrounded by the clouds of gas and dust from which they formed. The intense radiation given off by these hot young stars interacts with the gas surrounding them and is either reflected or re-emitted at a different wavelength. These complex processes, determined by the physics of the interstellar medium and the properties of the stars, are responsible for the magnificent colours of nebulae. The light blue nebulosity seen in this picture is mostly due to the reflection of starlight off small dust particles. The young stars in the R Coronae Australis complex are similar in mass to the Sun and do not emit enough ultraviolet light to ionise a substantial fraction of the surrounding hydrogen. This means that the cloud does not glow with the characteristic red colour seen in many star-forming regions. The huge dust cloud in which the reflection nebula is embedded is here shown in impressively fine detail. The subtle colours and varied textures of the dust clouds make this image resemble an impressionist painting. A prominent dark lane crosses the image from the centre to the bottom left. Here the visible light emitted by the stars that are forming inside the cloud is completely absorbed by the dust. These objects could only be detected by observing at longer wavelengths, by using a camera that can detect infrared radiation. R Coronae Australis itself is not visible to the unaided eye, but the tiny, tiara-shaped constellation in which it lies is easily spotted from dark sites due to its proximity on the sky to the larger constellation of Sagittarius and the rich star clouds towards the centre of our own galaxy, the Milky Way. More information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

  15. Ultraviolet spectroscopy of the extended solar corona

    NASA Astrophysics Data System (ADS)

    Kohl, John L.; Noci, Giancarlo; Cranmer, Steven R.; Raymond, John C.

    2006-04-01

    The first observations of ultraviolet spectral line profiles and intensities from the extended solar corona (i.e., more than 1.5 solar radii from Sun-center) were obtained on 13 April 1979 when a rocket-borne ultraviolet coronagraph spectrometer of the Harvard-Smithsonian Center for Astrophysics made direct measurements of proton kinetic temperatures, and obtained upper limits on outflow velocities in a quiet coronal region and a polar coronal hole. Following those observations, ultraviolet coronagraphic spectroscopy has expanded to include observations of over 60 spectral lines in coronal holes, streamers, coronal jets, and solar flare/coronal mass ejection (CME) events. Spectroscopic diagnostic techniques have been developed to determine proton, electron and ion kinetic temperatures and velocity distributions, proton and ion bulk flow speeds and chemical abundances. The observations have been made during three sounding rocket flights, four Shuttle deployed and retrieved Spartan 201 flights, and the Solar and Heliospheric Observatory (SOHO) mission. Ultraviolet spectroscopy of the extended solar corona has led to fundamentally new views of the acceleration regions of the solar wind and CMEs. Observations with the Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO revealed surprisingly large temperatures, outflow speeds, and velocity distribution anisotropies in coronal holes, especially for minor ions. Those measurements have guided theorists to discard some candidate physical processes of solar wind acceleration and to increase and expand investigations of ion cyclotron resonance and related processes. Analyses of UVCS observations of CME plasma properties and the evolution of CMEs have provided the following: temperatures, inflow velocities and derived values of resistivity and reconnection rates in CME current sheets, compression ratios and extremely high ion temperatures behind CME shocks, and three dimensional flow velocities and magnetic field chirality in CMEs. Ultraviolet spectroscopy has been used to determine the thermal energy content of CMEs allowing the total energy budget to be known for the first time. Such spectroscopic observations are capable of providing detailed empirical descriptions of solar energetic particle (SEP) source regions that allow theoretical models of SEP acceleration to be tailored to specific events, thereby enabling in situ measurements of freshly emitted SEPs to be used for testing and guiding the evolution of SEP acceleration theory. Here we review the history of ultraviolet coronagraph spectroscopy, summarize the physics of spectral line formation in the extended corona, describe the spectroscopic diagnostic techniques, review the advances in our understanding of solar wind source regions and flare/CME events provided by ultraviolet spectroscopy and discuss the scientific potential of next generation ultraviolet coronagraph spectrometers.

  16. Coronae as a result of giant magma intrusions in the lithosphere of Venus: insights from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Galland, Olivier; Polteau, Stephane; Werner, Stephanie C.

    2013-04-01

    Coronae on the surface of Venus are unique volcano-tectonic structures in the solar systems. Their circular morphology is associated with various topographic signatures, from bell-shape domes, flat-topped plateaus, to uplifted rings surrounding a subsided centre similar to caldera. Their extensive size and associated lava flows erupting from their periphery, indicate that they result from deep processes in the Venus mantle. Understanding their origin is thus essential for unraveling the dynamics of Venus through time. There are several scenarios explaining the formation of coronae, the most popular being the interaction between an upwelling mantle plume and the lithosphere, creating dynamic topography. In this contribution, we propose that coronae can result from the emplacement of giant magma intrusions below the Venus' lithosphere, on the basis of laboratory experiments. The experimental apparatus consists of a square box filled with compacted fine-grained silica flour (model crust), in which a low viscosity vegetable oil (model magma) is injected at constant flow rate. The initial conditions are such that magma initially flows horizontally, forming a sill-like body, to simulate magmatic underplating. During the experiments, oil injection triggers deformation of the model surface, which is monitored periodically using a moiré projection device, producing time series topographic maps of the model surface. Our results show that the surface evolution of the models follows three stages: (1) initial bell-shaped doming occurs above the injection inlet, producing radial open fractures at the model surfaces; (2) the bell-shape dome evolves to a flat-topped plateau, at the rim of which the oil erupts; (3) after the injection stops, the centre of the plateau subsides, and a positive topographic ring surrounding a depression, like a caldera, remains. The collapse of the plateau also generates concentric extensional fractures at the rims of the caldera. After the dynamic experiment, the oil solidifies and we extracted the intrusion, which exhibits a sill-shape, feeding outward circular inclined sheets at its external edges (i.e. a saucer-shaped sill). From a series of experiments in which the depth of injection h was varied, we show that the diameter of the intrusion and its associated topographic structure correlates linearly with h. The three evolutionary stages simulated in the experiments reproduce remarkably well (1) the three main corona morphologies observed on Venus, and (2) their established succession through time. In addition, the relationships between the structures and the oil flow in our experiments are also similar to those observed on Venus. Therefore, our experimental results suggest that corona structures are the result of giant magma intrusions in the lithosphere of Venus. In addition, our experiments suggest that the diameters of coronae are related to the depth of emplacement of the underlying intrusions, which might be controlled by the rheological architecture of the Venus' lithosphere. Therefore, the analysis of the dimensions and morphologies of coronae are likely to provide crucial information of the structure of the lithosphere of Venus.

  17. The photosphere-corona Interface: enrichement of the corona in low FIP elements and helium shells

    NASA Astrophysics Data System (ADS)

    Bazin, C.; Koutchmy, S.; Lamy, P.; Veselovski, I.

    2014-12-01

    Slitless consecutive spectra were obtained during the contacts of the last total solar eclipses (2008, 2009, 2010, 2012, et 2013). They allowed to show that the overabundance of low First Ionisation Potential (FIP) elements (Fe II, Ti II, Ba II) in the corona comes from the low layers of the solar atmosphere, just near and above the temperature minimum region of the high photosphere. All spectra are recorded with a fast CCD/CMOS camera, with an equivalent radial resolution of 60 milliarcseconds, or 45 km in the solar atmosphere, above a solar edge not affected by the parasitic light like it is outside of total eclipse conditions. Many emission lines of low FIP elements appear in regions situated between 200 to 600 km above the solar limb defined by the true continuum measured between the lines. This continuum appears at these altitudes where the beta of the plasma is near 1. The He I 4713 Å and He II 4686 Å (Paschen alpha line) shells appear at the height of 800 km above the solar edge and higher. The light curve I = f(h) of each ion is located at a particuliar altitude in the solar atmosphere. The scale height corresponds to a density variation, which allows to evaluate the temperature thanks to the hydrostatic equilibrium assumption. Moreover, with ionised Titanium lines taken as markers, we show a similarity between the photosphere-corona interface and the prominence-corona interface. We discuss the role of the magnetic field and the ambipolar diffusion for supplying the corona in mass, without taking into account the role of spicules. The photo-ionisation of the helium lines by the EUV coronal lines is illustrated thanks to an extract of SDO/AIA coronal stacked image simultaneously obtained.

  18. Charging of moving surfaces by corona discharges sustained in air

    NASA Astrophysics Data System (ADS)

    Wang, Jun-Chieh; Zhang, Daihua; Leoni, Napoleon; Birecki, Henryk; Gila, Omer; Kushner, Mark J.

    2014-07-01

    Atmospheric pressure corona discharges are used in electrophotographic (EP) printing technologies for charging imaging surfaces such as photoconductors. A typical corona discharge consists of a wire (or wire array) biased with a few hundred volts of dc plus a few kV of ac voltage. An electric discharge is produced around the corona wire from which electrons drift towards and charge the underlying dielectric surface. The surface charging reduces the voltage drop across the gap between the corona wire and the dielectric surface, which then terminates the discharge, as in a dielectric barrier discharge. In printing applications, this underlying surface is continuously moving throughout the charging process. For example, previously charged surfaces, which had reduced the local electric field and terminated the local discharge, are translated out of the field of view and are replaced with uncharged surface. The uncharged surface produces a rebound in the electric field in the vicinity of the corona wire which in turn results in re-ignition of the discharge. The discharge, so reignited, is then asymmetric. We found that in the idealized corona charging system we investigated, a negatively dc biased corona blade with a dielectric covered ground electrode, the discharge is initially sustained by electron impact ionization from the bulk plasma and then dominated by ionization from sheath accelerated secondary electrons. Depending on the speed of the underlying surface, the periodic re-ignition of the discharge can produce an oscillatory charging pattern on the moving surface.

  19. Relaxation oscillations and double temperature structures in stellar coronae

    NASA Astrophysics Data System (ADS)

    Hearn, A. G.; Kuin, N. P. M.; Martens, P. C. H.

    1983-08-01

    Further work using the iterative method of Hearn and Vardavas (1981) for calculating stationary models for stellar coronae has shown that the coronae of small extent obtained with large fluxes of mechanical energy are not stable. It is suggested that the corona undergoes a relaxation oscillation in which a single extended corona collapses to a double corona which in turn builds up to a single extended corona again. Such a coronal relaxation oscillation may be an explanation for the observed variations of mass loss from late B and early A type supergiants and perhaps from Be stars. The inclusion of radiative forces resulting from the absorption of photospheric radiation by resonance lines should increase the period of the oscillation. If these radiative forces are sufficiently strong they should stabilize the oscillation giving a double corona structure. Such a model could in principle explain the observed soft X-ray emission of OB supergiants and the discrepancy between mass loss rates deduced from the ultraviolet and radio measurements.

  20. Improved model for the analysis of back corona in pulse energised electrostatic precipitators

    Microsoft Academic Search

    Tamás Iváncsy; István Kiss; István Berta

    2009-01-01

    Formation of back corona and its effect on the voltage–current characteristics, etc., have been analysed by several authors. It has also been examined how the harmful effect of back corona can be reduced, for example by the application of pulse energisation. However, to find an optimal solution, modelling of the back corona effect is necessary. Different back corona models were

  1. High Energy Particles in the Solar Corona

    E-print Network

    A. Widom; Y. N. Srivastava; L. Larsen

    2008-04-16

    Collective Ampere law interactions producing magnetic flux tubes piercing through sunspots into and then out of the solar corona allow for low energy nuclear reactions in a steady state and high energy particle reactions if a magnetic flux tube explodes in a violent event such as a solar flare. Filamentous flux tubes themselves are vortices of Ampere currents circulating around in a tornado fashion in a roughly cylindrical geometry. The magnetic field lines are parallel to and largely confined within the core of the vortex. The vortices may thereby be viewed as long current carrying coils surrounding magnetic flux and subject to inductive Faraday and Ampere laws. These laws set the energy scales of (i) low energy solar nuclear reactions which may regularly occur and (ii) high energy electro-weak interactions which occur when magnetic flux coils explode into violent episodic events such as solar flares or coronal mass ejections.

  2. Negative corona discharges: A fundamental study

    NASA Astrophysics Data System (ADS)

    Gravendeel, Bastiaan

    Negative corona discharge in air in the Trichel regime was studied using fast current measurements (resolution 0.7 ns), mass spectrometry, and fast light intensity measurements resolved with time resolution 0.7 ns, in space resolution 0.05 mm, and wavelength resolution 0.16 nm. A theoretical expression which relates the externally measured current with the movement of charges inside an inhomogeneous field gap in the vicinity of space charge is derived. The rise time of Trichel pulses in atmospheric air is measured to be 1.15 ns. The cut-off of a Trichel pulse is due to the decrease of the local electric field in which the electron avalanche moves. A new Trichel pulse can occur only if the positive and negative ion clouds formed during the previous Trichel pulse disappear and the original field configuration is sufficiently restored.

  3. High Energy Particles in the Solar Corona

    E-print Network

    Widom, A; Larsen, L

    2008-01-01

    Collective Ampere law interactions producing magnetic flux tubes piercing through sunspots into and then out of the solar corona allow for low energy nuclear reactions in a steady state and high energy particle reactions if a magnetic flux tube explodes in a violent event such as a solar flare. Filamentous flux tubes themselves are vortices of Ampere currents circulating around in a tornado fashion in a roughly cylindrical geometry. The magnetic field lines are parallel to and largely confined within the core of the vortex. The vortices may thereby be viewed as long current carrying coils surrounding magnetic flux and subject to inductive Faraday and Ampere laws. These laws set the energy scales of (i) low energy solar nuclear reactions which may regularly occur and (ii) high energy electro-weak interactions which occur when magnetic flux coils explode into violent episodic events such as solar flares or coronal mass ejections.

  4. Corona-discharge-initiated mine explosions

    SciTech Connect

    Sacks, H.K.; Novak, T. [Virginia Polytechnic Institute & State University, Blacksburg, VA (United States). Dept. of Mining & Minerals Engineering

    2005-10-01

    Strong circumstantial evidence suggests that lightning has initiated methane explosions in abandoned and sealed areas of underground coal mines. The Mine Safety and Health Administration (MSHA) investigated several of these occurrences within recent years. The investigated explosions occurred at significant depths, ranging from 700 to 1200 ft. Data from the National Lightning Detection Network indicated a strong correlation between the times and locations of the explosions with those of specific lightning strikes. This paper proposes that corona discharge from a steel borehole casing is the most likely mechanism responsible for these ignitions. A recently investigated mine explosion and fire at a depth greater than 1000 ft was selected for this study. Computer simulations were performed, using data collected at the mine site. CDEGS software from Safe Engineering Services & Technologies, Ltd. and MaxwellSV from Ansoft Corporation were used for the simulations.

  5. Magnetohydrodynamic vortices in the solar corona

    NASA Astrophysics Data System (ADS)

    Nakariakov, Valery

    2012-07-01

    Interaction of coronal mass ejections with the plasma of the solar corona is accompanied with the generation of sharp shear flows that cause the induction of Alfvenic vortices. Numerical simulations revealed that for a broad range of parameters, the vortices are essentially compressible, with the perturbations of the density and the absolute value of the magnetic field in the vortex arms reaching 50% of the background density. The typical size of the vortex is about the size of the obstacle. The frequency of the vortex shedding is controlled by a dimensionless parameter known as the Strouhal number. We found that in collisionless low-beta plasma this number is about 0.2. Recent imaging observations with SDO/AIA revealed the generation of Alfvenic vortices at the flanks of emerging plasmoids. The vortices introduce a frictionless aerodynamic drag force, applied to the interacting plasmas. Implication of these findings for the excitation of kink oscillations of coronal loops and CME kinematics is discussed.

  6. The TESIS experiment on the CORONAS-PHOTON spacecraft

    NASA Astrophysics Data System (ADS)

    Kuzin, S. V.; Zhitnik, I. A.; Shestov, S. V.; Bogachev, S. A.; Bugaenko, O. I.; Ignat'ev, A. P.; Pertsov, A. A.; Ulyanov, A. S.; Reva, A. A.; Slemzin, V. A.; Sukhodrev, N. K.; Ivanov, Yu. S.; Goncharov, L. A.; Mitrofanov, A. V.; Popov, S. G.; Shergina, T. A.; Solov'ev, V. A.; Oparin, S. N.; Zykov, A. M.

    2011-04-01

    On February 26, 2009, the first data was obtained in the TESIS experiment on the research of the solar corona using imaging spectroscopy. The TESIS is a part of the scientific equipment of the CORONAS-PHO-TON spacecraft and is designed for imaging the solar corona in soft X-ray and extreme ultraviolet regions of the spectrum with high spatial, spectral, and temporal resolutions at altitudes from the transition region to three solar radii. The article describes the main characteristics of the instrumentation, management features, and operation modes.

  7. Unraveling the Genetic Basis of Asthma and Allergic Diseases

    PubMed Central

    Meng, Jian-Feng

    2010-01-01

    Asthma and allergic diseases are believed to be complex genetic diseases which may result from the interaction of multiple genetic factors and environmental stimuli. In past decades, great efforts have been exerted in unraveling their genetic basis. The strategies in discovering genes and genetic variants, confirming their importance in pathogenesis of asthma and allergic diseases, as well as their strengths and limitations are summarized comprehensively and concisely. The current consensus about the genetic basis of asthma and allergic diseases is briefly described as well. PMID:20885906

  8. The origins of hot plasma in the solar corona.

    PubMed

    De Pontieu, B; McIntosh, S W; Carlsson, M; Hansteen, V H; Tarbell, T D; Boerner, P; Martinez-Sykora, J; Schrijver, C J; Title, A M

    2011-01-01

    The Sun's outer atmosphere, or corona, is heated to millions of degrees, considerably hotter than its surface or photosphere. Explanations for this enigma typically invoke the deposition in the corona of nonthermal energy generated by magnetoconvection. However, the coronal heating mechanism remains unknown. We used observations from the Solar Dynamics Observatory and the Hinode solar physics mission to reveal a ubiquitous coronal mass supply in which chromospheric plasma in fountainlike jets or spicules is accelerated upward into the corona, with much of the plasma heated to temperatures between ~0.02 and 0.1 million kelvin (MK) and a small but sufficient fraction to temperatures above 1 MK. These observations provide constraints on the coronal heating mechanism(s) and highlight the importance of the interface region between photosphere and corona. PMID:21212351

  9. Expectation of ozone generation in alternating current corona discharges

    NASA Astrophysics Data System (ADS)

    Yehia, Ashraf; Mizuno, Akira

    2012-03-01

    An analytical study was made in this paper to calculate the ozone generation inside an ac corona discharge reactor. The corona discharges were formed in a coaxial wire-cylinder reactor. The reactor was fed by dry air flowing with constant rates at atmospheric pressure and room temperature and stressed by an ac voltage. Concentration of the ozone generated inside the reactor was measured as a function of the ac corona current under different discharge conditions. An empirical equation was derived from the experimental results for calculating the ozone concentration generated inside the reactor. The results, that have been calculated by using the derived equation, have agreed with the experimental results over the whole range of the investigated parameters. Therefore, the derived equation represents a suitable criterion for expecting the ozone concentration that will generate by ac coronas in dry air fed coaxial wire-cylinder reactors under any discharge conditions in range of the investigated parameters.

  10. Stepped form of negative corona current pulses in hydrogen

    NASA Astrophysics Data System (ADS)

    Zahoranová, Anna; ?ernák, Mirko; Štefe?ka, Miloslav; Wagner, Hans-Erich

    1999-12-01

    Current wave forms of initial stages of discharge formation in a short negative point-to-plane gap have been measured with a nanosecond time resolution in hydrogen at pressures (12.5 76) kPa and for various overvoltages and cathode point radii. The measurements revealed the existence of a stepped form of negative corona current pulses in hydrogen. To test existing models for negative corona pulse formation, effects of changing cathode secondary electron emission were studied using copper and brass cathodes coated by CuI and graphite. It is concluded that a negative corona pulse is associated with the ignition of a cathode-directed streamer in the vicinity of the cathode. We report what we believe are the first experimental observations of non-Trichel oscillations of negative corona current with a frequency of (1 10) MHz.

  11. Nanoparticles formation and deposition in the trichel pulse corona

    NASA Astrophysics Data System (ADS)

    Amirov, R. H.; Petrov, A. A.; Samoylov, I. S.

    2013-03-01

    Cathode erosion in the negative corona discharge has been studied in the point-to-plane electrode configuration with Cu cathodes in the Trichel pulse regime. Redeposition of erosion products has been found on the cathode surface in form of agglomerates of 10-nm nanoparticles. Nanocraters and nanoparticles formation in the negative corona discharge has been considered in frames of electro-explosive mechanism of cathode erosion. According to this mechanism the cathode erosion is performed as a consequence of elementary erosion events each of which is caused by a Trichel pulse. A 1-dimentional model of corona-produced nanoparticles dynamics in the gap was elaborated. According to results of the simulation, the redeposition is explained by charging of the nanoparticles due to positive ions adsorption and thermionic emission. The size, temperature and initial velocity of the aerosol nanoparticles have the decisive action on redeposition in the negative corona discharge.

  12. Experimental Tools to Study Molecular Recognition within the Nanoparticle Corona

    PubMed Central

    Landry, Markita P.; Kruss, Sebastian; Nelson, Justin T.; Bisker, Gili; Iverson, Nicole M.; Reuel, Nigel F.; Strano, Michael S.

    2014-01-01

    Advancements in optical nanosensor development have enabled the design of sensors using syntheticmolecular recognition elements through a recently developed method called Corona Phase MolecularRecognition (CoPhMoRe). The synthetic sensors resulting from these design principles are highly selective for specific analytes, and demonstrate remarkable stability for use under a variety of conditions. An essential element of nanosensor development hinges on the ability to understand the interface between nanoparticles and the associated corona phase surrounding the nanosensor, an environment outside of the range of traditional characterization tools, such as NMR. This review discusses the need for new strategies and instrumentation to study the nanoparticle corona, operating in both in vitro and in vivo environments. Approaches to instrumentation must have the capacity to concurrently monitor nanosensor operation and the molecular changes in the corona phase. A detailed overview of new tools for the understanding of CoPhMoRe mechanisms is provided for future applications. PMID:25184487

  13. Solar corona/prominence seen through the White Light Coronograph

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The solar corona and a solar prominence as seen through the White Light Coronograph, Skylab Experiment S052, on January 17, 1974. This view was reproduced from a television transmission made by a TV camera aboard the Skylab space station in Earth orbit. The bright spot is a burn in the vidicon. The solar corona is the halo around the Sun which is normally visible only at the time of solar eclipse by the Moon. The Skylab coronography uses an externally-mounted disk system which occults the brilliant solar surface while allowing the fainter radiation of the corona to enter an annulus and be photographed. A mirror system allows either TV viewing of the corona or photographic recording of the image.

  14. A Data-Driven Evolution Model for the Global Corona

    NASA Astrophysics Data System (ADS)

    Feng, X. S.; Jiang, C.; Xiang, C. Q.; Wu, S.

    2011-12-01

    In this work we have developed a new time-dependent global corona model for the study of dynamic evolution of the global corona that can respond continuously to the changing of the photospheric magnetogram. A surface flux transport (SFT) model is employed to produce the time-varying and self-consistent magnetogram with synoptic map as input. The global corona model is established with our newly-developed numerical code AMR-CESE-MHD on an overset grid of Yin-Yang overlapping structure. The SFT model and the three-dimensional global corona model is coupled through the boundary condition of projected-characteristic method. Numerical study of the coronal evolution from Carrington rotation 1913 to 1915 presents results comparable with multi-observed coronal images.

  15. Color photometry of the solar corona on July 31, 1981

    NASA Astrophysics Data System (ADS)

    Nikolskij, G. M.

    1983-12-01

    Photographs of the outer solar corona obtained by the Soviet-French expedition to Kazakhstan during the total eclipse of July 31, 1981, are investigated. An F = 300 mm/5.6 camera and 60-millimeter color reversal Ektachrome-64 film were used. The radial brightness distribution is obtained along radial cross sections passing through the south 'coronal hole' and a bright region of the corona in blue (450 nm) and red (630 nm) light. By comparison with the sun, the corona is redder (by at least 10 percent) at distances of 2-6 solar radii. Allowance is made for the emission of the sky and the aureole. Isophotes are constructed (r less than 10 solar radii) in blue and red light. The brightness of the corona averaged over all directions also points to reddening. The flattening of the outer isophotes increases with distance.

  16. Viscoelastic Relaxation of Topographic Highs on Venus to Produce Coronae

    NASA Technical Reports Server (NTRS)

    Janes, Daniel M.; Squyres, Steven W.

    1995-01-01

    Coronae on Venus are believed to result from the gravitationally driven relaxation of topography that was originally raised by mantle diapirs. We examine this relaxation using a viscoelastic finite element code, and show that an initially plateau shaped load will evolve to the characteristic corona topography of central raised bowl, annular rim, and surrounding moat. Stresses induced by the relaxation are consistent with the development of concentric extensional fracturing common on the outer margins of corona moats. However, relaxation is not expected to produce the concentric faulting often observed on the annular rim. The relaxation timescale is shorter than the diapir cooling timescale, so loss of thermal support controls the rate at which topography is reduced. The final corona shape is supported by buoyancy and flexural stresses and will persist through geologic time. Development of lower, flatter central bowls and narrower and more pronounced annular rims and moats enhanced by thicker crusts, higher thermal gradients, and crustal thinning over the diapir.

  17. Experimental Tools to Study Molecular Recognition within the Nanoparticle Corona

    E-print Network

    Kruss, Sebastian

    Advancements in optical nanosensor development have enabled the design of sensors using synthetic molecular recognition elements through a recently developed method called Corona Phase Molecular Recognition (CoPhMoRe). The ...

  18. CORONA DISCHARGE IN FLUID HELIUM: DRASTIC GROWTH OF ELECTRON MOBILITY

    Microsoft Academic Search

    Liquid Helium (LHe) at 4.2K was excited using a corona discharge for negative high voltages. The experiments were carried out with temperature increasing and different pressures. Current-voltage characteristics were measured and analyzed. The sharp increasing of the corona current was observed at temperatures 7K and 10K under pressure in the range 0.2-0.4 MPa. The analysis showed the electron mobility increasing

  19. Trichel pulse characteristics---negative corona discharge in air

    Microsoft Academic Search

    P. Sattari; C. F. Gallo; G. S. P. Castle; K. Adamiak

    2011-01-01

    In this paper a three-species two-dimensional model is used for the simulation of the Trichel pulse regime of corona discharge in air for a point-plane configuration. Effects of different parameters of the model on Trichel pulse characteristics (Trichel pulse period and the average corona current) are studied. The parameters of interest are external resistance of the circuit, secondary electron emission

  20. Explosive mechanism of cathode erosion in Trichel pulse negative corona

    Microsoft Academic Search

    A. A. Petrov; R. H. Amirov; I. S. Samoylov

    2009-01-01

    Summary form only given. Cathode erosion has been investigated in Trichel pulse negative corona discharge in air in point-to-plane electrode configuration on tungsten, copper, graphite and aluminum cathodes. It is found that negative corona causes erosion of the cathode surface in form of nanometer-size craters and fissures. Observed etching may be explained in terms of electro- explosive processes. In Trichel

  1. Negative DC Corona Discharges in Supercritical Carbon Dioxide

    Microsoft Academic Search

    C. H. Zhang; T. Kiyan; T. Namihira; A. Uemura; T. Fang; B. C. Roy; M. Sasaki; S. Katsuki; H. Akiyama; M. Goto

    In our previous work, positive dc discharge plasmas have been measured and analyzed. In present studies, the measurements for breakdown voltages were made with point-plane electrodes for high-pressure carbon dioxide (CO2) up to supercritical conditions under negative DC applied voltage. Negative dc corona (glow discharge) is Trichel pulses. Corona pulses, whether positive or negative, are streamers: each pulse is a

  2. Trichel Pulse Characteristics in Negative dc Corona Discharge

    Microsoft Academic Search

    Kefeng Shang; Xiangxin Xue; Xiaochen Wang

    2011-01-01

    Trichel pulse characteristics of needle-to-plate electrode were studied. The experimental results indicate that time-averaged corona current increased with the voltage, but the peak pulse current decreased with the voltage; when the averaged electric field strength reached about 7.6kV\\/cm, Trichel pulse was not steady and easily converted to pulseless corona. The curvature radius had influence on the current amplitude of Trichel

  3. Elastic Thickness Estimates for Coronae Associated with Chasmata on Venus

    NASA Technical Reports Server (NTRS)

    Hoogenboom, T.; Martin, P.; Housean, G. A.

    2005-01-01

    Coronae are large-scale circular tectonic features surrounded by annular ridges. They are generally considered unique to Venus and may offer insights into the differences in lithospheric structure or mantle convective pattern between Venus and Earth. 68% of all coronae are associated with chasmata or fracture belts. The remaining 32% are located at volcanic rises or in the plains. Chasmata are linear to arcuate troughs, with trough parallel fractures and faults which extend for 1000 s of kilometers. Estimates of the elastic thickness of the lithosphere (T(sub e)) have been calculated in a number of gravity/topography studies of Venus and for coronae specifically. None of these studies, however, have explored the dependence of T(sub e) on the tectonic history of the region, as implied from the interpretation of relative timing relationships between coronae and surrounding features. We examine the relationship between the local T(sub e) and the relative ages of coronae and chasmata with the aim of further constraining the origin and evolution of coronae and chasmata systems.

  4. Optimizing the properties of the protein corona surrounding nanoparticles for tuning payload release.

    PubMed

    Cifuentes-Rius, Anna; de Puig, Helena; Kah, James Chen Yong; Borros, Salvador; Hamad-Schifferli, Kimberly

    2013-11-26

    We manipulate the passive release rates of DNA payloads on protein coronas formed around nanoparticles (NPs) by varying the corona composition. The coronas are prepared using a mixture of hard and soft corona proteins. We form coronas around gold nanorods (NRs), nanobones (NBs), and carbon nanotubes (CNTs) from human serum (HS) and find that tuning the amount of human serum albumin (HSA) in the NR-coronas (NR-HS-DNA) changes the payload release profile. The effect of buffer strength, HS concentration, and concentration of the cetyltrimethylammonium bromide (CTAB) passivating the NP surfaces on passive release is explored. We find that corona properties play an important role in passive release, and concentrations of CTAB, HS, and phosphate buffer used in corona formation can tune payload release profiles. These advances in understanding protein corona properties bring us closer toward developing a set of basic design rules that enable their manipulation and optimization for particular biological applications. PMID:24128271

  5. The theory of positive glow corona

    NASA Astrophysics Data System (ADS)

    Morrow, R.

    1997-11-01

    A theory for the current and light pulses of positive glow corona from a point in air is presented; this phenomenon was first observed as an apparently continuous glow by Michael Faraday. Results are obtained, in concentric sphere geometry, for air at atmospheric pressure, by solving the continuity equations for electrons, positive ions, negative ions and metastable oxygen molecules, coupled with Poisson's equation. A series of `saw-toothed' current pulses of period about 0022-3727/30/22/008/img1 is predicted with a DC current level. Accompanying the current peaks are discrete pulses of light 30 ns wide. Successive `shells' of positive ions, from successive current pulses, carry 96% of the mean current. The mean current - voltage relationship has the classic square-law form. The seed electrons required for successive pulses are detached from negative ions by metastable oxygen molecules. Photo-ionization is crucial for the discharge at the anode and for the formation of negative ions throughout the gap. The pulse frequency varies with applied voltage and is found to be approximately proportional to the positive-ion mobility. The surface electric field at the central electrode remains close to Peek's onset field. The origin of onset streamers is explained and sub-microsecond voltage pulses are found to produce streamers. The results for concentric-cylinder electrodes are described briefly.

  6. Radio seismology of the outer solar corona

    E-print Network

    Zaqarashvili, T V; Brazhenko, A I; Panchenko, M; Konovalenko, A A; Franzuzenko, A V; Dorovskyy, V V; Rucker, H O

    2013-01-01

    Observed oscillations of coronal loops in EUV lines have been successfully used to estimate plasma parameters in the inner corona ( 0.2 R_0). We use the large Ukrainian radio telescope URAN-2 to observe type IV radio burst at the frequency range of 8-32 MHz during the time interval of 09:50-12:30 UT in April 14, 2011. The burst was connected to C2.3 flare, which occurred in AR 11190 during 09:38-09:49 UT. The dynamic spectrum of radio emission shows clear quasi-periodic variations in the emission intensity at almost all frequencies. Wavelet analysis at four different frequencies (29 MHz, 25 MHz, 22 MHz and 14 MHz) shows the quasi-periodic variation of emission intensity with periods of 34 min and 23 min. The periodic variations can be explained by the first and second harmonics of vertical kink oscillation of transequatorial coronal loops, which were excited by the same flare. The apex of transequatorial loops may reach up to 1.2 R_0 altitude. We derive and solve the dispersion relation of trapped MHD oscilla...

  7. Pre-Flare Flows in the Corona

    NASA Astrophysics Data System (ADS)

    Wallace, A. J.; Harra, L. K.; van Driel-Gesztelyi, L.; Green, L. M.; Matthews, S. A.

    2010-12-01

    Solar flares take place in regions of strong magnetic fields and are generally accepted to be the result of a resistive instability leading to magnetic reconnection. When new flux emerges into a pre-existing active region it can act as a flare and coronal mass ejection trigger. In this study we observed active region 10955 after the emergence of small-scale additional flux at the magnetic inversion line. We found that flaring began when additional positive flux levels exceeded 1.38×1020 Mx (maxwell), approximately 7 h after the initial flux emergence. We focussed on the pre-flare activity of one B-class flare that occurred on the following day. The earliest indication of activity was a rise in the non-thermal velocity one hour before the flare. 40 min before flaring began, brightenings and pre-flare flows were observed along two loop systems in the corona, involving the new flux and the pre-existing active region loops. We discuss the possibility that reconnection between the new flux and pre-existing loops before the flare drives the flows by either generating slow mode magnetoacoustic waves or a pressure gradient between the newly reconnected loops. The subsequent B-class flare originated from fast reconnection of the same loop systems as the pre-flare flows.

  8. UVCS\\/[ITAL]SOHO[\\/ITAL] Empirical Determinations of Anisotropic Velocity Distributions in the Solar Corona

    Microsoft Academic Search

    J. L. Kohl; G. Noci; E. Antonucci; G. Tondello; M. C. E. Huber; S. R. Cranmer; L. Strachan; A. V Panasyuk; L. D. Gardner; M. Romoli; S. Fineschi; D. Dobrzycka; J. C. Raymond; P. Nicolosi; O. H. W. Siegmund; D. Spadaro; C. Benna; A. Ciaravella; S. Giordano; S. R. Habbal; M. Karovska; X. Li; R. Martin; J. G. Michels; A. Modigliani; G. Naletto; R. H. O'Neal; C. Pernechele; G. Poletto; P. L. Smith; R. M. Suleiman

    1998-01-01

    We present a self-consistent empirical model for several plasma parameters of a polar coronal hole near solar minimum, derived from observations with the Solar and Heliospheric ObservatoryUltraviolet Coronagraph Spectrometer. The model describes the radial distribution of density for electrons, H , and O and the outflow 05 1

  9. Systems biology unravels interferon responses to respiratory virus infections

    PubMed Central

    Kroeker, Andrea L; Coombs, Kevin M

    2014-01-01

    Interferon production is an important defence against viral replication and its activation is an attractive therapeutic target. However, it has long been known that viruses perpetually evolve a multitude of strategies to evade these host immune responses. In recent years there has been an explosion of information on virus-induced alterations of the host immune response that have resulted from data-rich omics technologies. Unravelling how these systems interact and determining the overall outcome of the host response to viral infection will play an important role in future treatment and vaccine development. In this review we focus primarily on the interferon pathway and its regulation as well as mechanisms by which respiratory RNA viruses interfere with its signalling capacity. PMID:24600511

  10. Unraveling the Atomic Structure of Ultrafine Iron Clusters

    PubMed Central

    Wang, Hongtao; Li, Kun; Yao, Yingbang; Wang, Qingxiao; Cheng, Yingchun; Schwingenschlögl, Udo; Zhang, Xi Xiang; Yang, Wei

    2012-01-01

    Unraveling the atomic structures of ultrafine iron clusters is critical to understanding their size-dependent catalytic effects and electronic properties. Here, we describe the stable close-packed structure of ultrafine Fe clusters for the first time, thanks to the superior properties of graphene, including the monolayer thickness, chemical inertness, mechanical strength, electrical and thermal conductivity. These clusters prefer to take regular planar shapes with morphology changes by local atomic shuffling, as suggested by the early hypothesis of solid-solid transformation. Our observations differ from observations from earlier experimental study and theoretical model, such as icosahedron, decahedron or cuboctahedron. No interaction was observed between Fe atoms or clusters and pristine graphene. However, preferential carving, as observed by other research groups, can be realized only when Fe clusters are embedded in graphene. The techniques introduced here will be of use in investigations of other clusters or even single atoms or molecules. PMID:23251781

  11. Dyspraxia or developmental coordination disorder? Unravelling the enigma

    PubMed Central

    Gibbs, John; Appleton, Jeanette; Appleton, Richard

    2007-01-01

    Dyspraxia is an enigma to many people, both professional and lay alike—what is it, how does it relate to developmental coordination disorder and associated conditions, how common is it, how is it recognised and diagnosed and how should it be managed? This article attempts to unravel this enigma by: dealing with the terminology of coordination difficulties from the “clumsy child syndrome” through “dyspraxia” to “developmental coordination disorder (DCD)”; briefly examining the debate as to whether dyspraxia or DCD should be regarded as a medical or social disorder; discussing the differential diagnosis of dyspraxia or DCD; considering the assessment of children with dyspraxia or DCD; reviewing the range of current treatment approaches in the UK. PMID:17515623

  12. New Images of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Gurman, Joseph B.; Thompson, Barbara J.; Newmark, Jeffrey A.; Deforest, Craig E.

    In 1.5 years of operation, The Extreme Ultraviolet Imaging Telescope (EIT) on SOHO has obtained over 40,000 images of the Sun in four wavebands between 171 Angstroms and 304 Angstroms, with spatial resolution limited only by the pixel scale of 2.59 arcsec. These images, and in particular compilations of time series of images into digital movies, have changed several of our ideas about the corona at temperatures of 0.9 - 2.5 MK. For the first time, we are able to see outflow in polar plumes and microjets inputting momentum into the high-speed, polar wind flow. For the first time, in conjunction with the LASCO coronagraphs and ground-based He I imagers, we have been able to see all the structures involved in coronal mass ejections (CMEs), from the surface of the Sun to 30 solar radii above it. In several cases, we have been able to observe directly the dramatic Moreton waves emanating from the active region where the CMEs originate, and radiating across virtually the entire visible hemisphere of the Sun. We interpret these large-scale coronal disturbances as fast-mode waves. Such events appear in the SOHO-LASCO coronagraphs as earthward-directed, and several have been detected by solar wind monitoring experiments on SOHO and other spacecraft. We have been able to view a variety of small-scale phenomena as well, including motions in prominences and filaments, macrospicular and polar microjet eruptions, and fine structures in the polar crown filament belt. The multi-wavelength capability of EIT makes it possible to determine the temperature of the coronal plasma and, here, too, we have been afforded a novel view: the heating in coronal active regions occurs over a considerably larger area than the high-density loops structures alone (i.e., bright features) would indicate.

  13. Theory of negative corona in oxygen

    NASA Astrophysics Data System (ADS)

    Morrow, R.

    1985-09-01

    Theoretical predictions are given of the development of the current and the distributions of charge and electric field in negative corona, or Trichel current pulses [G. W. Trichel, Phys. Rev. 54, 1078 (1938)], in oxygen at a pressure of 6.67 kPa (50 Torr). For a 10-mm-diam negative sphere located 20 mm from a positive plane, the calculated current pulse has a rise time of 11 ns, a pulse width of 50 ns, and a peak amplitude of 13 mA. These results agree satisfactorily with experimental values. The predicted velocity of the cathode-directed light pulse also agrees well with observations. The theory is based on the accurate numerical solution of Poisson's equation in conjunction with the continuity equations for electrons, positive ions, and negative ions. The effects of ionization, attachment, recombination, electron diffusion, and photoemission and ion secondary-electron emission from the cathode are all included. The initial steep rise of the current pulse is largely due to rapid ionization and electron motion in the high Laplacian field near the cathode. As the discharge develops, a dense plasma forms near the cathode, leading to strong space-charge distortion of the field. A prominent cathode fall region is formed immediately adjacent to the cathode, an almost zero field is formed within the plasma and the field is enhanced over the region to the anode. The current pulse is quenched because the low electric field in the plasma immobilizes the majority of the electrons which then undergo three-body attachment; furthermore, the cathode fall region becomes reduced to such a short distance that insignificant current is produced from this region. Because of the low mobility of the negative ions, the current remains low and the structure of the space-charge fields changes only slowly with time between pulses.

  14. INTERCHANGE RECONNECTION IN A TURBULENT CORONA

    SciTech Connect

    Rappazzo, A. F.; Matthaeus, W. H. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Ruffolo, D. [Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Servidio, S. [Dipartimento di Fisica, Universita della Calabria, I-87036 Cosenza (Italy); Velli, M., E-mail: rappazzo@udel.edu [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-10-10

    Magnetic reconnection at the interface between coronal holes and loops, the so-called interchange reconnection, can release the hotter, denser plasma from magnetically confined regions into the heliosphere, contributing to the formation of the highly variable slow solar wind. The interchange process is often thought to develop at the apex of streamers or pseudo-streamers, near Y- and X-type neutral points, but slow streams with loop composition have been recently observed along fanlike open field lines adjacent to closed regions, far from the apex. However, coronal heating models, with magnetic field lines shuffled by convective motions, show that reconnection can occur continuously in unipolar magnetic field regions with no neutral points: photospheric motions induce a magnetohydrodynamic turbulent cascade in the coronal field that creates the necessary small scales, where a sheared magnetic field component orthogonal to the strong axial field is created locally and can reconnect. We propose that a similar mechanism operates near and around boundaries between open and closed regions inducing a continual stochastic rearrangement of connectivity. We examine a reduced magnetohydrodynamic model of a simplified interface region between open and closed corona threaded by a strong unipolar magnetic field. This boundary is not stationary, becomes fractal, and field lines change connectivity continuously, becoming alternatively open and closed. This model suggests that slow wind may originate everywhere along loop-coronal-hole boundary regions and can account naturally and simply for outflows at and adjacent to such boundaries and for the observed diffusion of slow wind around the heliospheric current sheet.

  15. Intermittency in the photosphere and corona above an active region

    E-print Network

    Abramenko, Valentyna; Wang, Haimin; 10.1086/588426

    2009-01-01

    Recent studies undoubtedly demonstrate that the magnetic field in the photosphere and corona is an intermittent structure, which offers new views on the underlying physics. In particular, such problems as the existence in the corona of localized areas with extremely strong resistivity (required to explain magnetic reconnection of all scales) and the interchange between small and large scales (required in study of the photosphere/corona coupling), to name a few, can be easily captured by the concept of intermittency. This study is focused on simultaneous time variations of intermittency properties derived in the photosphere, chromosphere and corona. We analyzed data for NOAA AR 10930 acquired between Dec 08, 2006 12:00 UT and Dec 13, 2006 18:45 UT. Photospheric intermittency was inferred from Hinode magnetic field measurements, while intermittency in the transition region and corona was derived from Nobeyama 9 GHz radio polarization measurements, high cadence Hinode/XRT/Be-thin data as well as GOES 1-8\\AA flux...

  16. CORONA DISCHARGE IGNITION FOR ADVANCED STATIONARY NATURAL GAS ENGINES

    SciTech Connect

    Dr. Paul D. Ronney

    2003-09-12

    An ignition source was constructed that is capable of producing a pulsed corona discharge for the purpose of igniting mixtures in a test chamber. This corona generator is adaptable for use as the ignition source for one cylinder on a test engine. The first tests were performed in a cylindrical shaped chamber to study the characteristics of the corona and analyze various electrode geometries. Next a test chamber was constructed that closely represented the dimensions of the combustion chamber of the test engine at USC. Combustion tests were performed in this chamber and various electrode diameters and geometries were tested. The data acquisition and control system hardware for the USC engine lab was updated with new equipment. New software was also developed to perform the engine control and data acquisition functions. Work is underway to design a corona electrode that will fit in the new test engine and be capable igniting the mixture in one cylinder at first and eventually in all four cylinders. A test engine was purchased for the project that has two spark plug ports per cylinder. With this configuration it will be possible to switch between corona ignition and conventional spark plug ignition without making any mechanical modifications.

  17. Measurement of Electrical Currents in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Spangler, Steven

    2007-11-01

    Some theories for heating of the solar corona invoke Joule heating by electrical currents. Observations of spatially-extended radio sources through the corona show times when there is a difference in the Faraday rotation between two lines of sight separated by about 33,000 km in the corona. Ampere's Law is used to relate these observations to the presence of electrical current flowing between the two lines of sight. I infer a current of 2.5 x10^9 Amperes in the case of the strongest signal, and a current of 2.3 x10^8 Amperes in another, marginally significant detection. A model of coronal current sheets is used to interpret the current measurements, and estimate the volumetric heating rate due to Joule dissipation. The model uses the Spitzer resistivity. The model heating rate is approximately 6 orders of magnitude less than independent, observational estimates in the relevant part of the corona. Either the currents detected play a negligible role in coronal heating, or the effective resistivity in the corona is 6 orders of magnitude larger than the Spitzer value.

  18. 3-D MHD Simulation of the Accretion Disk Corona

    NASA Astrophysics Data System (ADS)

    Pankin, A. Y.; Mikic, Z.; Titov, V.; Goodman, J.; Uzdensky, D. A.; Schnack, D. D.

    2006-10-01

    Evolution of a magnetic loop in an accretion disk corona is studied by using the resistive MHD code MAB. Axisymmetric corona and infinitesimally-thin accretion disk with the Keplerian velocity profile is used as the initial state. In the accretion disk, conservation of angular momentum prevents the accretion. The microscopic resistivity and viscosity are too small to explain the accretion rate inferred from observations. In this work, we test an idea that the evolution of coronal magnetic fields might make differential rotation flows in the disk to be unstable by leading to the development of coronal magneto- rotational instability (MRI) and enhancement of angular momentum transport in the disk. In our computer simulations, the MHD equations for the accretion disk and its corona are modeled separately. The poloidal component of magnetic field and the velocity field in the disk are used as a boundary condition to advance the coronal flows. The toroidal and radial components of magnetic field are computed in the corona simulation and their boundary values are used in turn to advance the accretion disk flows. This provides a feedback loop between the MHD flows in the accretion disk and its corona. In this report, the evolution of a single coronal magnetic loop and the corresponding angular momentum transport in the disk are considered.

  19. Evidence for wave heating in the solar corona.

    PubMed

    Hahn, Michael

    2013-07-01

    The temperature of the Sun increases over a short distance from a few thousand degrees in the photosphere to over a million degrees in the corona. To understand coronal heating is one of the major problems in astrophysics. There is general agreement that the energy source is convective motion in and below the photosphere. It remains to determine how this mechanical energy is transported outward into the corona and then deposited as heat. Two classes of models have been proposed, namely those that rely on magnetic reconnection and those that rely on waves, particularly Alfvén waves. There is increasing evidence that waves are ubiquitous in the corona. However, a difficulty for wave-driven models has been that most theories predict Alfvén waves to be undamped in the corona, and therefore they cannot dissipate their energy into heat. Our research has shown unambiguous observational evidence that the waves do damp at sufficiently low heights in the corona to be important for coronal heating. PMID:23676178

  20. Oxidative coupling of methane with ac and dc corona discharges

    SciTech Connect

    Liu, C.; Marafee, A.; Hill, B.; Xu, G.; Mallinson, R.; Lobban, L. [Univ. of Oklahoma, Norman, OK (United States). Inst. of Natural Gas Utilization] [Univ. of Oklahoma, Norman, OK (United States). Inst. of Natural Gas Utilization

    1996-10-01

    The oxidative coupling of methane (OCM) is being actively studied for the production of higher hydrocarbons from natural gas. The present study concentrated on the oxidative conversion of methane in an atmospheric pressure, nonthermal plasma formed by ac or dc corona discharges. Methyl radicals are formed by reaction with negatively-charged oxygen species created in the corona discharge. The selectivity to products ethane and ethylene is affected by electrode polarity, frequency, and oxygen partial pressure in the feed. Higher C{sub 2} yields were obtained with the ac corona. All the ac corona discharges are initiated at room temperature (i.e., no oven or other heat source is used), and the temperature increases to 300--500 C due to the exothermic reactions and the discharge itself. The largest C{sub 2} yield is 21% with 43.3% methane conversion and 48.3% C{sub 2} selectivity at a flowrate of 100 cm{sup 3}/min when the ac corona is at 30 Hz, 5 kV (rms) input power was used. The methane conversion may be improved to more than 50% by increasing the residence time, but the C{sub 2} selectivity decreases. A reaction mechanism including the oxidative dehydrogenation (OXD) of ethane to ethylene is presented to explain the observed phenomena. The results suggest that ac and/or dc gas discharge techniques have significant promise for improving the economics of OCM processes.

  1. Admittance Survey of Type 1 Coronae on Venus: Implications for Elastic Thickness

    NASA Technical Reports Server (NTRS)

    Hoogenboom, T.; Smrekar, S. E.; Anderson, F. S.; Houseman, G.

    2003-01-01

    Coronae are volcano-tectonic features on Venus which range from 60km to 2600km and are defined by their nearly circular patterns of fractures. Type 1 (regular) coronae are classified as having >50% complete fracture annuli. Previous work has examined the factors controlling the morphology, size, and fracture pattern of coronae, using lithospheric properties, loading signature and geologic characteristics. However, these studies have been limited to Type 2 (topographic) coronae (e.g. coronaes with <50% fracture annuli), and the factors controlling the formation of Type 1 coronae remain poorly understood. In this study, we apply the methodology of to survey the admittance signature for Type 1 coronae to determine the controlling parameters which govern Type 1 coronae formation.

  2. Probing the solar corona with very long baseline interferometry.

    PubMed

    Soja, B; Heinkelmann, R; Schuh, H

    2014-01-01

    Understanding and monitoring the solar corona and solar wind is important for many applications like telecommunications or geomagnetic studies. Coronal electron density models have been derived by various techniques over the last 45 years, principally by analysing the effect of the corona on spacecraft tracking. Here we show that recent observational data from very long baseline interferometry (VLBI), a radio technique crucial for astrophysics and geodesy, could be used to develop electron density models of the Sun's corona. The VLBI results agree well with previous models from spacecraft measurements. They also show that the simple spherical electron density model is violated by regional density variations and that on average the electron density in active regions is about three times that of low-density regions. Unlike spacecraft tracking, a VLBI campaign would be possible on a regular basis and would provide highly resolved spatial-temporal samplings over a complete solar cycle. PMID:24946791

  3. Alfvenically driven slow shocks in the solar chromosphere and corona

    NASA Technical Reports Server (NTRS)

    Hollweg, Joseph V.

    1992-01-01

    The nonlinear evolution of an Alfvenic impulse launched from the photosphere and its dynamical effects on the chromosphere, transition region (TR), and corona are investigated using a simple 1D model. It is found that the leading edge of the torsional pulse can steepen into a fast shock in the chromosphere if the pulse is of sufficiently large amplitude and short duration. A slow shock which develops behind the Alfvenic pulse can reflect downgoing Alfven waves back up to the corona. The upgoing reflected wave can induce a significant upward ejection of the TR. Nonlinear dynamics are found to lead to very impulsive behavior at later times. It is suggested that impulsive events occurring in the TR or corona need not be interpreted in terms of reconnection-driven microflares. It is also found that B(0) in the chromosphere can be amplified when the TR and chromosphere fall.

  4. Probing the solar corona with very long baseline interferometry

    PubMed Central

    Soja, B.; Heinkelmann, R.; Schuh, H.

    2014-01-01

    Understanding and monitoring the solar corona and solar wind is important for many applications like telecommunications or geomagnetic studies. Coronal electron density models have been derived by various techniques over the last 45 years, principally by analysing the effect of the corona on spacecraft tracking. Here we show that recent observational data from very long baseline interferometry (VLBI), a radio technique crucial for astrophysics and geodesy, could be used to develop electron density models of the Sun’s corona. The VLBI results agree well with previous models from spacecraft measurements. They also show that the simple spherical electron density model is violated by regional density variations and that on average the electron density in active regions is about three times that of low-density regions. Unlike spacecraft tracking, a VLBI campaign would be possible on a regular basis and would provide highly resolved spatial–temporal samplings over a complete solar cycle. PMID:24946791

  5. HIGH SPATIAL RESOLUTION OBSERVATIONS OF LOOPS IN THE SOLAR CORONA

    SciTech Connect

    Brooks, David H.; Ugarte-Urra, Ignacio [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States); Warren, Harry P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Winebarger, Amy R. [NASA Marshall Space Flight Center, ZP 13, Huntsville, AL 35812 (United States)

    2013-08-01

    Understanding how the solar corona is structured is of fundamental importance to determine how the Sun's upper atmosphere is heated to high temperatures. Recent spectroscopic studies have suggested that an instrument with a spatial resolution of 200 km or better is necessary to resolve coronal loops. The High Resolution Coronal Imager (Hi-C) achieved this performance on a rocket flight in 2012 July. We use Hi-C data to measure the Gaussian widths of 91 loops observed in the solar corona and find a distribution that peaks at about 270 km. We also use Atmospheric Imaging Assembly data for a subset of these loops and find temperature distributions that are generally very narrow. These observations provide further evidence that loops in the solar corona are often structured at a scale of several hundred kilometers, well above the spatial scale of many proposed physical mechanisms.

  6. The Structure and Dynamics of the Corona - Heliosphere Connection

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.; Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav; Zurbuchen, Thomas H.

    2011-01-01

    Determining the source at the Sun of the slow solar wind is one of the major unsolved problems in solar and heliospheric physics. First, we review the existing theories for the slow wind and argue that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory in which the slow wind originates from the continuous opening and closing of narrow open field corridors, the S-Web model, is described. Support for the S-Web model is derived from MHD solutions for the quasisteady corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona - heliosphere connection, in general.

  7. The Structure and Dynamics of the Corona - Heliosphere Connection

    NASA Technical Reports Server (NTRS)

    Antiochos, Spiro K.; Linker, Jon A.; Lionello, Roberto; Mikic, Zoran; Titov, Viacheslav; Zurbuchen, Thomas H.

    2010-01-01

    Determining the source at the Sun of the slow solar wind is one of the major unsolved problems in solar and heliospheric physics. First, we review the existing theories for the slow wind and argue that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory in which the slow wind originates from the continuous opening and closing of narrow open field corridors, the S-Web model, is described. Support for the S-Web model is derived from MHD solutions for the quasisteady corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona - heliosphere connection, in general.

  8. The Structure and Dynamics of the Corona—Heliosphere Connection

    NASA Astrophysics Data System (ADS)

    Antiochos, Spiro K.; Linker, Jon A.; Lionello, Roberto; Miki?, Zoran; Titov, Viacheslav; Zurbuchen, Thomas H.

    2012-11-01

    Determining how the heliospheric magnetic field and plasma connect to the Sun's corona and photosphere is, perhaps, the central problem in solar and heliospheric physics. For much of the heliosphere, this connection appears to be well understood. It is now generally accepted that so-called coronal holes, which appear dark in X-rays and are predominantly unipolar at the photosphere, are the sources of quasi-steady wind that is generally fast, >500 km/s, but can sometimes be slow. However, the connection to the Sun of the slow, non-steady wind is far from understood and remains a major mystery. We review the existing theories for the sources of the non-steady wind and demonstrate that they have difficulty accounting for both the observed composition of the wind and its large angular extent. A new theory is described in which this wind originates from the continuous opening and closing of narrow open field corridors in the corona, which give rise to a web of separatrices (the S-Web) in the heliosphere. Note that in this theory the corona—heliosphere connection is intrinsically dynamic, at least for this type of wind. Support for the S-Web model is derived from MHD solutions for the corona and wind during the time of the August 1, 2008 eclipse. Additionally, we perform fully dynamic numerical simulations of the corona and heliosphere in order to test the S-Web model as well as the interchange model proposed by Fisk and co-workers. We discuss the implications of our simulations for the competing theories and for understanding the corona—heliosphere connection, in general.

  9. Radio Remote Sensing of the Corona and the Solar Wind

    E-print Network

    Steven R. Spangler; Catherine A. Whiting

    2008-09-26

    Modern radio telescopes are extremely sensitive to plasma on the line of sight from a radio source to the antenna. Plasmas in the corona and solar wind produce measurable changes in the radio wave amplitude and phase, and the phase difference between wave fields of opposite circular polarization. Such measurements can be made of radio waves from spacecraft transmitters and extragalactic radio sources, using radio telescopes and spacecraft tracking antennas. Data have been taken at frequencies from about 80 MHz to 8000 MHz. Lower frequencies probe plasma at greater heliocentric distances. Analysis of these data yields information on the plasma density, density fluctuations, and plasma flow speeds in the corona and solar wind, and on the magnetic field in the solar corona. This paper will concentrate on the information that can be obtained from measurements of Faraday rotation through the corona and inner solar wind. The magnitude of Faraday rotation is proportional to the line of sight integral of the plasma density and the line-of-sight component of the magnetic field. Faraday rotation provides an almost unique means of estimating the magnetic field in this part of space. This technique has contributed to measurement of the large scale coronal magnetic field, the properties of electromagnetic turbulence in the corona, possible detection of electrical currents in the corona, and probing of the internal structure of coronal mass ejections (CMEs). This paper concentrates on the search for small-scale coronal turbulence and remote sensing of the structure of CMEs. Future investigations with the Expanded Very Large Array (EVLA) or Murchison Widefield Array (MWA) could provide unique observational input on the astrophysics of CMEs.

  10. Photometry and structure of the solar corona during the solar eclipse of July 31, 1981

    NASA Astrophysics Data System (ADS)

    Khetsuriani, Ts. S.; Dzhaparidze, D. R.

    The observational material taken by the Abastumani Astrophysical Observatory expedition at the total solar eclipse of July 31, 1981 has been used for the structural and photometric investigation of the corona. The photometry of the corona is made by the equidensity method. The intensities are expressed in absolute units. The structural peculiarities of the corona are described. The geometric shape and photometric data permit to assign the corona to the solar activity maximum type.

  11. Unraveling the mystery of compost teas used for organic disease and insect pest

    E-print Network

    Unraveling the mystery of compost teas used for organic disease and insect GilleN #12;What are compost teas? · Watery extracts (teas) made from placing compost in a mesh bag and soaking in water · Plant vs. animal (manure

  12. A theory of heating of quiet solar corona

    NASA Astrophysics Data System (ADS)

    Wu, C. S.; Yoon, P. H.; Wang, C. B.

    2015-03-01

    A theory is proposed to discuss the creation of hot solar corona. We pay special attention to the transition region and the low corona, and consider that the sun is quiet. The proposed scenario suggests that the protons are heated by intrinsic Alfvénic turbulence, while the ambient electrons are heated by the hot protons via collisions. The theory contains two prime components: the generation of the Alfvénic fluctuations by the heavy minor ions in the transition region and second, the explanation of the temperature profile in the low solar atmosphere. The proposed heating process operates continuously in time and globally in space.

  13. Effect of humidity on negative corona Trichel pulses

    NASA Astrophysics Data System (ADS)

    Deng, Fucheng; Ye, Lingyun; Song, Kaichen; Huang, Tiantian

    2014-08-01

    The effects of environmental parameters, e.g., humidity, on the corona discharges in practical applications are important. A two-dimensional (2D) hydrodynamic drift-diffusion model has been used to investigate the effects of humidity on the negative corona Trichel pulses (TPs). The simulations are performed with a conventional needle-to-plate configuration in humid air. It is found that the magnitude of TPs grows gradually with increasing humidity and the frequency of TPs increases with humidity. The movements and formations of charged particles are faster in higher humidity. The numerical results are consistent with the experimental observation.

  14. Theory of stepped pulses in negative corona discharges

    NASA Astrophysics Data System (ADS)

    Morrow, R.

    1985-12-01

    Theoretical calculations are presented which account for the development of the step observed on the leading edge of the current pulse in a negative point-plane corona (Trichel pulse). The theory explains the step in terms of independent photon and ion secondary processes at the cathode. It is applied specifically to describe the shape of an experimentally determined corona current pulse from a 2-mm-diam negative point located 20 mm from a positive plane in oxygen at 6.67 kPa. The secondary-emission coefficients are determined to be ?p=2×10-4 (photon secondaries) and ?i=0.12 (ion secondaries).

  15. RAPID COMMUNICATION: Trichel pulses in negative corona discharge on trees

    NASA Astrophysics Data System (ADS)

    Aubrecht, L.; Koller, J.; Zahoranova, A.

    1999-09-01

    In this article we present the results of an experimental study of negative corona pulses in air at atmospheric pressure. New, more complex waveforms of pulses in discharge on trees and plants (pine, spruce) are found and compared with waveforms measured in a classical negative corona with metal electrodes. It is also found that the repetition rate of negative plant pulses is much lower than in the case of classical `metal' Trichel pulses. The pulses are less regular and fluctuations of amplitudes and periods are large.

  16. Trichel pulse characteristics—negative corona discharge in air

    NASA Astrophysics Data System (ADS)

    Sattari, P.; Gallo, C. F.; Castle, G. S. P.; Adamiak, K.

    2011-04-01

    In this paper a three-species two-dimensional model is used for the simulation of the Trichel pulse regime of corona discharge in air for a point-plane configuration. Effects of different parameters of the model on Trichel pulse characteristics (Trichel pulse period and the average corona current) are studied. The parameters of interest are external resistance of the circuit, secondary electron emission coefficient and negative and positive ion mobilities. Moreover, the numerical simulation was performed for the configuration used in the experimental analysis reported in the literature and the results proved to be very compatible.

  17. Fabrication of Corona-Free Nanoparticles with Tunable Hydrophobicity

    PubMed Central

    2014-01-01

    A protein corona is formed at the surface of nanoparticles in the presence of biological fluids, masking the surface properties of the particle and complicating the relationship between chemical functionality and biological effects. We present here a series of zwitterionic NPs of variable hydrophobicity that do not adsorb proteins at moderate levels of serum protein and do not form hard coronas at physiological serum concentrations. These particles provide platforms to evaluate nanobiological behavior such as cell uptake and hemolysis dictated directly by chemical motifs at the nanoparticle surface. PMID:24971670

  18. Observational studies of reconnection in the solar corona

    SciTech Connect

    McKenzie, David E. [Department of Physics, Montana State University, P.O. Box 173840, Bozeman, Montana 59717-3840 (United States)

    2011-11-15

    In recent years, observational studies of the corona have shifted focus. Where they were once purely qualitative morphological explorations seeking to support the presence of reconnection, more investigations are providing empirical estimates of the physical conditions in the reconnecting corona. These studies are enabled and enhanced by orbiting telescopes with high angular and temporal resolution. In this article, some recent findings about the empirical quantities are reviewed, including recent estimates of the flux transferred in individual patchy reconnection episodes, the size distribution of post-reconnection flux tubes, and the energy released by the flux tubes as they shrink.

  19. Patchy reconnection in the solar corona

    NASA Astrophysics Data System (ADS)

    Guidoni, Silvina Esther

    2011-05-01

    Magnetic reconnection in plasmas, a process characterized by a change in connectivity of field lines that are broken and connected to other ones with different topology, owes its usefulness to its ability to unify a wide range of phenomena within a single universal principle. There are newly observed phenomena in the solar corona that cannot be reconciled with two-dimensional or steady-state standard models of magnetic reconnection. Supra-arcade downflows (SADs) and supra-arcade downflowing loops (SADLs) descending from reconnection regions toward solar post-flare arcades seem to be two different observational signatures of retracting, isolated reconnected flux tubes with irreducible three-dimensional geometries. This dissertation describes work in refining and improving a novel model of patchy reconnection, where only a small bundle of field lines is reconnected across a current sheet (magnetic discontinuity) and forms a reconnected thin flux tube. Traditional models have not been able to explain why some of the observed SADs appear to be hot and relatively devoid of plasma. The present work shows that plasma depletion naturally occurs in flux tubes that are reconnected across nonuniform current sheets and slide trough regions of decreasing magnetic field magnitude. Moreover, through a detailed theoretical analysis of generalized thin flux tube equations, we show that the addition to the model of pressure-driven parallel dynamics, as well as temperature-dependent, anisotropic viscosity and thermal conductivity is essential for self-consistently producing gas-dynamic shocks inside reconnected tubes that heat and compress plasma to observed temperatures and densities. The shock thickness can be as long as the entire tube and heat can be conducted along tube's legs, possibly driving chromospheric evaporation. We developed a computer program that solves numerically the thin flux tube equations that govern the retraction of reconnected tubes. Simulations carried out with this program corroborate our theoretical predictions. A comparison of these simulations with fully three-dimensional magnetohydrodynamic simulations is presented to assess the validity of the thin flux tube model. We also present an observational method based on total emission measure and mean temperature to determine where in the current sheet a tube was reconnected.

  20. A study of the lightning channel corona sheath Grzegorz Maslowski1,2

    E-print Network

    Florida, University of

    A study of the lightning channel corona sheath Grzegorz Maslowski1,2 and Vladimir A. Rakov1] Dynamics of lightning channel corona sheath surrounding thin channel core is examined on the basis of three vicinity of the lightning channel and measured channel base current. The corona sheath radius, velocity

  1. A waveguide model of the return stroke channel with a "metamaterial" corona

    E-print Network

    Lehtinen, Nikolai G.

    A waveguide model of the return stroke channel with a "metamaterial" corona Nikolai G. Lehtinen1) highly conducting thin core channel; (2) "metamaterial" corona, i.e., corona with an effective bulk measurements. When the second layer of the waveguide is filled with an isotropic material, the slowdown

  2. Off-limb EUV observations of the solar corona and transients with the CORONAS-F/SPIRIT telescope-coronagraph

    NASA Astrophysics Data System (ADS)

    Slemzin, V.; Bougaenko, O.; Ignatiev, A.; Kuzin, S.; Mitrofanov, A.; Pertsov, A.; Zhitnik, I.

    2008-10-01

    The SPIRIT telescope aboard the CORONAS-F satellite (in orbit from 26 July 2001 to 5 December 2005), observed the off-limb solar corona in the 175 Å (Fe IX, X and XI lines) and 304 Å (He II and Si XI lines) bands. In the coronagraphic mode the mirror was tilted to image the corona at the distance of 1.1...5 Rsun from the solar center, the outer occulter blocked the disk radiation and the detector sensitivity was enhanced. This intermediate region between the fields of view of ordinary extreme-ultraviolet (EUV) telescopes and most of the white-light (WL) coronagraphs is responsible for forming the streamer belt, acceleration of ejected matter and emergence of slow and fast solar wind. We present here the results of continuous coronagraphic EUV observations of the solar corona carried out during two weeks in June and December 2002. The images showed a "diffuse" (unresolved) component of the corona seen in both bands, and non-radial, ray-like structures seen only in the 175 Å band, which can be associated with a streamer base. The correlations between latitudinal distributions of the EUV brightness in the corona and at the limb were found to be high in 304 Å at all distances and in 175 Å only below 1.5 Rsun. The temporal correlation of the coronal brightness along the west radial line, with the brightness at the underlying limb region was significant in both bands, independent of the distance. On 2 February 2003 SPIRIT observed an expansion of a transient associated with a prominence eruption seen only in the 304 Å band. The SPIRIT data have been compared with the corresponding data of the SOHO LASCO, EIT and UVCS instruments.

  3. Simultaneous Observation of High Temperature Plasma of Solar Corona By TESIS CORONAS-PHOTON and XRT Hinode.

    NASA Astrophysics Data System (ADS)

    Reva, A.; Kuzin, S.; Bogachev, S.; Shestov, S.

    2012-05-01

    The Mg XII spectroheliograph is a part of instrumentation complex TESIS (satellite CORONAS-PHOTON). This instrument builds monochromatic images of hot plasma of the solar corona (? = 8.42 Å, T>5 MK). The Mg XII spectroheliograph observed hot plasma in the non-flaring active-region NOAA 11019 during nine days. We reconstructed DEM of this active region with the help of genetic algorithm (we used data of the Mg XII spectroheliograph, XRT and EIT). Emission measure of the hot component amounts 1 % of the emission measure of the cool component.

  4. Instrumentation for Pulsed Corona Discharge Generation Applied to Water

    Microsoft Academic Search

    Régulo Lopez-Callejas; Rosendo Pena-Eguiluz; Antonio Mercado-Cabrera; Samuel R. Barocio; Anibal de la Piedad-Beneitez; Jorge S. Benitez-Read; Joel O. Pacheco-Sotelo

    2008-01-01

    In this paper, we present a model (which is structured as an equivalent electric circuit whose elements are identified and deducted from the nature of the medium, the ionization and expansion process of the streamers that convey the prebreakdown current, and the energy associated to the electric breakdown in water) and a simulation of a pulsed corona discharge (PCD). Considering

  5. Asymptotic analysis of corona discharge from thin electrodes

    NASA Technical Reports Server (NTRS)

    Durbin, P. A.

    1986-01-01

    The steady discharge of a high-voltage corona is analyzed as a singular perturbation problem. The small parameter is the ratio of the length of the ionization region to the total gap length. By this method, current versus voltage characteristics can be calculated analytically.

  6. The role of electron attaching impurities in direct current coronae

    Microsoft Academic Search

    V A Garten; R B Head; J M Overbeek

    1968-01-01

    A study of the chemistry of pre-breakdown discharges in direct current coronae at both highly-stressed anodes and cathodes showed that the presence of electron attaching impurities is essential. Both positive streamers and negative discharges producing Trichel pulses were investigated and it was found that the amount of impurity required to produce positive streamers is one to several orders higher than

  7. Negative coronas: Low current mode – pulse mode transition

    Microsoft Academic Search

    V. Repän; M. Laan; J. Aarik; V. Sammelselg

    1999-01-01

    In the paper the results of experimental study of negative corona in a point – plane gap in a dust-free air flow at atmospheric pressure are presented. Both the low current mode (LCM) of the discharge and Trichel pulses are externally triggered by UV light. Close to the inception voltage of Trichel pulses short-duration current spikes appear besides the steady

  8. Transition from Trichel-pulse corona to dielectric barrier discharge

    Microsoft Academic Search

    S. V. Kulkarni; R. J. Van Brunt; V. K. Lakdawala

    1990-01-01

    An investigation was undertaken to examine the influence that thin circular solid dielectric barriers placed on the planar anode surface have on the stochastic behavior of Trichel pulses. It is shown that charging of the dielectric surface by the corona discharge introduces another memory effect that becomes increasingly significant as the point-to-plane gap spacing is reduced. At a sufficiently short

  9. Erosion of a copper cathode in a negative corona discharge

    NASA Astrophysics Data System (ADS)

    Asinovski?, É. I.; Petrov, A. A.; Samoylov, I. S.

    2008-02-01

    The pulsed-periodic regime of a negative corona (Trichel pulses) in atmospheric-pressure air, which leads to explosion emission mechanisms (ecton generation) of pointed cathode erosion, is investigated. The jet erosion process at the copper cathode is discovered, and micrometer dendritelike structures formed by erosion products returning to the cathode are detected.

  10. Rogelio Omar Corona Nez M. Sc Biological Sciences

    E-print Network

    Rogelio Omar Corona Núñez M. Sc Biological Sciences Specialty in Environmental Biology Rogelio Información en Geomática, SA de CV. Studies Bachelor on Chemistry Pharmacology Biology. Chemistry Faculty.V. since 2008. Profesional´s Profile Specialist in development of environmental projects GIS sofyware: Arc

  11. Hot Gaseous Coronae around Spiral Galaxies: Probing the Illustris Simulation

    E-print Network

    Bogdan, Akos; Kraft, Ralph P; Hernquist, Lars; Gilfanov, Marat; Torrey, Paul; Churazov, Eugene; Genel, Shy; Forman, William R; Murray, Stephen S; Vikhlinin, Alexey; Jones, Christine; Boehringer, Hans

    2015-01-01

    The presence of hot gaseous coronae around present-day massive spiral galaxies is a fundamental prediction of galaxy formation models. However, our observational knowledge remains scarce, since to date only four gaseous coronae were detected around spirals with massive stellar bodies ($\\gtrsim2\\times10^{11} \\ \\rm{M_{\\odot}}$). To explore the hot coronae around lower mass spiral galaxies, we utilized Chandra X-ray observations of a sample of eight normal spiral galaxies with stellar masses of $(0.7-2.0)\\times10^{11} \\ \\rm{M_{\\odot}}$. Although statistically significant diffuse X-ray emission is not detected beyond the optical radii ($\\sim20$ kpc) of the galaxies, we derive $3\\sigma$ limits on the characteristics of the coronae. These limits, complemented with previous detections of NGC 1961 and NGC 6753, are used to probe the Illustris Simulation. The observed $3\\sigma$ upper limits on the X-ray luminosities and gas masses exceed or are at the upper end of the model predictions. For NGC 1961 and NGC 6753 the o...

  12. Energy distribution of nanoflares in the quiet solar corona

    NASA Astrophysics Data System (ADS)

    Ulyanov, Artyom

    2012-07-01

    We present a detailed statistical analysis of flare-like events in low layer of solar corona detected with TESIS instrument onboard CORONAS-PHOTON satellite in 171 {Å} during high-cadence (5 sec) time-series. The estimated thermal energies of these small events amount to 10^{23} - 10^{26} erg. According to modern classification flare-like events with such energies are usually referred to as nanoflares. The big number of registered events (above 2000) allowed us to obtain precise distributions of geometric and physical parameters of nanoflares, the most intriguing being energy distribution. Following Aschwanden et al. (2000) and other authors we approximated the calculated energy distribution with a single power law slope: N(E)dE ˜ N^{-?}dE. The power law index was derived to be ? = 2.4 ± 0.2, which is very close to the value reported by Krucker & Benz (1998): ? ? 2.3 - 2.4. The total energy input from registered events constitute about 10^4 erg \\cdot cm^{-2} \\cdot s^{-1}, which is well beyond net losses in quiet corona (3 \\cdot 10^5 erg \\cdot cm^{-2} \\cdot s^{-1}). However, the value of ? > 2 indicates that nanoflares with lower energies dominate over nanoflares with bigger energies and could contribute considerably to quiet corona heating.

  13. SIMBA observations of the R Corona Australis molecular cloud

    Microsoft Academic Search

    K. Kampgen; B. Reipurth; M. Albrecht; E. Kreysa; R. Lemke; M. Nielbock; L. A. Reichertz; A. Sievers; R. Zylka

    2003-01-01

    We have mapped the R Corona Australis molecular cloud at 1.2 mm with SIMBA on SEST and detected 25 distinct dust emission peaks. While 7 of them coincide with positions of previously known young stars, 18 are seemingly not associated with any known stellar object. We discuss the nature of individual sources and conclude that there are at least four

  14. On the Size of Structures in the Solar Corona

    E-print Network

    C. E. DeForest

    2007-02-22

    Fine-scale structure in the corona appears not to be well resolved by current imaging instruments. Assuming this to be true offers a simple geometric explanation for several current puzzles in coronal physics, including: the apparent uniform cross-section of bright threadlike structures in the corona; the low EUV contrast (long apparent scale height) between the top and bottom of active region loops; and the inconsistency between loop densities derived by spectral and photometric means. Treating coronal loops as a mixture of diffuse background and very dense, unresolved filamentary structures address these problems with a combination of high plasma density within the structures, which greatly increases the emissivity of the structures, and geometric effects that attenuate the apparent brightness of the feature at low altitudes. It also suggests a possible explanation for both the surprisingly high contrast of EUV coronal loops against the coronal background, and the uniform ``typical'' height of the bright portion of the corona (about 0.3 solar radii) in full-disk EUV images. Some ramifications of this picture are discussed, including an estimate (10-100 km) of the fundamental scale of strong heating events in the corona.

  15. Charge trapping in corona-charge polyethylene films

    Microsoft Academic Search

    R. Toomer; T. J. Lewis

    1980-01-01

    A model for the process of surface potential decay of insulating films following charging by corona ions is developed. Account is taken of charge trapping and release at sites both in the surface and in the bulk where trapping can reduce the mobility significantly. The model is particularly applicable to polyethylene films and is used to interpret measurements of surface

  16. Imaging and Processing Images of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Espenak, Fred

    Of all astronomical phenomena visible to the naked eye, none is as spectacular, or as fleeting, as a total eclipse of the Sun. For a few brief minutes, the Moon blocks the Sun's blindingly bright photosphere to reveal the ethereal solar corona. This gossamer halo, forming the outer atmosphere of the Sun, can only be seen in the eerie twilight brought on by totality.

  17. Energy balance in the chromosphere-corona transition region

    Microsoft Academic Search

    Roger A. Kopp

    1972-01-01

    The classical picture of the transition region is that of a thin spherically symmetric shell maintained in a steady average thermodynamical state by a balance between conductive heating from the hot overlying corona and radiative losses. The further analysis of existing extreme ultraviolet flux data casts doubt on the correctness of this simple model. It is shown that the downward

  18. Acute hemichorea due to infarction in the corona radiata

    Microsoft Academic Search

    F. Barinagarrementeria; F. Vega; O. H. Del Brutto

    1989-01-01

    A 66-year-old hypertensive man presented with acute hemichorea. Magnetic resonance imaging disclosed an infarct, confined to the contralateral corona radiata, that interrupted excitatory corticostriate fibres. The movement disorder may have been caused by subcortical lesion without direct involvement of the basal ganglia.

  19. Astronomy and Astrophysics Review Xray astronomy of stellar coronae ?

    E-print Network

    Guedel, Manuel

    and evolution of stellar magnetic fields from the first days of a protostellar life to the latest stages of stellar evolution among giants and su­ pergiants. The discipline of stellar coronal X­ray astronomy hasAstronomy and Astrophysics Review in press X­ray astronomy of stellar coronae ? Manuel G Ë? udel

  20. A Technique for Measuring Electrical Currents in the Solar Corona

    E-print Network

    Steven R. Spangler

    2007-09-11

    A technique is described for measuring electrical currents in the solar corona. It uses radioastronomical polarization measurements of a spatially-extended radio source viewed through the corona. The observations yield the difference in the Faraday rotation measure between two closely-spaced lines of sight through the corona, a measurement referred to as {\\em differential Faraday rotation}. It is shown that the expression for differential Faraday rotation is proportional to the path integral $\\oint n \\vec{B}\\cdot \\vec{ds}$ where $n$ is the plasma density and $\\vec{B}$ is the coronal magnetic field. The integral is around a closed loop (Amperian Loop) in the corona. If the plasma density is assumed roughly constant, the differential Faraday rotation is proportional to the current within the loop, via Ampere's Law. The validity of the constant density approximation is discussed, and two test cases are presented in which the associated error in the inferred current is small, of order tens of percent or less. The method is illustrated with observations of the radio source 3C228 with the Very Large Array (VLA) in August, 2003. A measurement of a differential Faraday rotation ``event'' on August 16, 2003, yields an estimate of $2.5 \\times 10^9$ Amperes in the Amperian Loop. A smaller event on August 18 yields an enclosed current of $2.3 \\times 10^8$ Amperes. The implications of these currents for coronal heating are briefly discussed.

  1. Unraveling shock-induced chemistry using ultrafast lasers

    SciTech Connect

    Moore, David Steven [Los Alamos National Laboratory

    2010-12-06

    The exquisite time synchronicity between shock and diagnostics needed to unravel chemical events occurring in picoseconds has been achieved using a shaped ultrafast laser pulse to both drive the shocks and interrogate the sample via a multiplicity of optical diagnostics. The shaped laser drive pulse can produce well-controlled shock states of sub-ns duration with sub-10 ps risetimes, sufficient for investigation offast reactions or phase transformations in a thin layer with picosecond time resolution. The shock state is characterized using ultrafast dynamic ellipsometry (UDE) in either planar or Gaussian spatial geometries, the latter allowing measurements of the equation of state of materials at a range of stresses in a single laser pulse. Time-resolved processes in materials are being interrogated using UDE, ultrafast infrared absorption, ultrafast UV/visible absorption, and femtosecond stimulated Raman spectroscopy. Using these tools we showed that chemistry in an energetic thin film starts only after an induction time of a few tens of ps, an observation that allows differentiation between proposed shock-induced reaction mechanisms. These tools are presently being applied to a variety of energetic and reactive sample systems, from nitromethane and carbon disulfide, to microengineered interfaces in tunable energetic mixtures. Recent results will be presented, and future trends outlined.

  2. Unraveling shock-induced chemistry using ultrafast lasers

    SciTech Connect

    Moore, David S [Los Alamos National Laboratory

    2009-01-01

    The exquisite time synchronicity between shock and diagnostics needed to unravel chemical events occurring in picoseconds has been achieved using a shaped ultrafast laser pulse to both drive the shocks and interrogate the sample via a multiplicity of optical diagnostics. The shaped laser drive pulse can produce well-controlled shock states of sub-ns duration with sub-10 ps risetimes, sufficient for investigation of fast reactions or phase transformations in a thin layer with picosecond time resolution. The shock state is characterized using ultrafast dynamic ellipsometry (UDE) in either planar or Gaussian spatial geometries, the latter allowing measurements of the equation of state of materials at a range of stresses in a single laser pulse. Time-resolved processes in materials are being interrogated using UDE, ultrafast infrared absorption, ultrafast UV/visible absorption, and femtosecond stimulated Raman spectroscopy. Using these tools we showed that chemistry in an energetic thin film starts only after an induction time of a few tens of ps, an observation that allows differentiation between proposed shock-induced reaction mechanisms. These tools are presently being applied to a variety of energetic and reactive sample systems, from nitromethane and carbon disulfide, to micro-engineered interfaces in tunable energetic mixtures.

  3. Natural Light Harvesting Systems: Unraveling the quantum puzzles

    E-print Network

    A. Thilagam

    2014-11-23

    In natural light harvesting systems, the sequential quantum events of photon absorption by specialized biological antenna complexes, charge separation, exciton formation and energy transfer to localized reaction centers culminates in the conversion of solar to chemical energy. A notable feature in these processes is the exceptionally high efficiencies ($>$ 95\\%) at which excitation is transferred from the illuminated protein complex site to the reaction centers. The high speeds of excitation propagation within a system of interwoven biomolecular network structures, is yet to be replicated in artificial light harvesting complexes. A clue to unraveling the quantum puzzles of nature may lie in the observations of long lived coherences lasting several picoseconds in the electronic spectra of photosynthetic complexes which occurs even in noisy environmental baths. The exact nature of the association between the high energy propagation rates and strength of quantum coherences remains largely unsolved. This review presents recent developments in quantum theories, and links information-theoretic aspects with photosynthetic light-harvesting processes in biomolecular systems. There is examination of various attempts to pinpoint the processes that underpin coherence features arising from the light harvesting activities of biomolecular systems, with particular emphasis on the effects that factors such non-Markovianity, zeno mechanisms, teleportation, quantum predictability and the role of multipartite states have on the quantum dynamics of biomolecular systems. A discussion of how quantum thermodynamical principles and agent-based modeling and simulation approaches can improve our understanding of natural photosynthetic systems is included.

  4. An XMM-Newton Study of the Coronae of ?2 Coronae Borealis

    NASA Astrophysics Data System (ADS)

    Suh, Jin A.; Audard, Marc; Güdel, Manuel; Paerels, Frederik B. S.

    2005-09-01

    We present results of XMM-Newton Guaranteed Time observations of the RS CVn binary ?2 Coronae Borealis. The spectra obtained with the Reflection Grating Spectrometers and the European Photon Imaging Camera MOS2 were simultaneously fitted with collisional ionization equilibrium plasma models to determine coronal abundances of various elements. Contrary to the solar first ionization potential (FIP) effect, in which elements with a low FIP are overabundant in the corona compared to the solar photosphere, and contrary to the ``inverse'' FIP effect observed in several active RS CVn binaries, coronal abundance ratios in ?2 CrB show a complex pattern, as supported by similar findings in the Chandra HETGS analysis of ?2 CrB with a different methodology by Osten and coworkers in 2003. Low-FIP elements (<10 eV) have abundance ratios relative to Fe that are consistent with the solar photospheric ratios, whereas high-FIP elements have abundance ratios that increase with increasing FIP. We find that the coronal Fe abundance is consistent with the stellar photospheric value, indicating that there is no metal depletion in ?2 CrB. However, we obtain a higher Fe absolute abundance than Osten and coworkers did. Except for Ar and S, our absolute abundances are about 1.5 times larger than those reported by Osten and coworkers. However, a comparison of their model with our XMM-Newton data (and vice versa) shows that both models work adequately in general. We find, therefore, no preference for one methodology over the other for deriving coronal abundances. Despite the systematic discrepancy in absolute abundances, our abundance ratios are very close to those obtained by Osten and coworkers. Finally, we confirm the measurement of a low density in O VII (<4×1010 cm-3) but could not confirm the higher densities measured in spectral lines formed at higher temperatures that were derived by other studies of ?2 CrB due to the lower spectral resolution of the XMM-Newton grating spectrometers.

  5. Release timescales of solar energetic particles in the low corona

    NASA Astrophysics Data System (ADS)

    Agueda, N.; Klein, K.-L.; Vilmer, N.; Rodríguez-Gasén, R.; Malandraki, O. E.; Papaioannou, A.; Subirà, M.; Sanahuja, B.; Valtonen, E.; Dröge, W.; Nindos, A.; Heber, B.; Braune, S.; Usoskin, I. G.; Heynderickx, D.; Talew, E.; Vainio, R.

    2014-10-01

    Aims: We present a systematic study of the timing and duration of the release processes of near-relativistic (NR; >50 keV) electrons in the low corona. Methods: We analyze seven well-observed events using in situ measurements by both the ACE and Wind spacecraft and context electromagnetic observations in soft X-rays, radio, hard X-rays and white light. We make use of velocity dispersion analysis to estimate the release time of the first arriving electrons and compare with the results obtained by using a simulation-based approach, taking interplanetary transport effects into account to unfold the NR electron release time history from in situ measurements. Results: The NR electrons observed in interplanetary space appear to be released during either short (<30 min) or long (>2 h) periods. The observation of NR electron events showing beamed pitch-angle distributions (PADs) during several hours is the clearest observational signature of sustained release in the corona. On the other hand, the in situ observation of PADs isotropizing in less than a couple of hours is a clear signature of a prompt release of electrons in the low corona. Short release episodes appear to originate in solar flares, in coincidence with the timing of the observed type III radio bursts. Magnetic connectivity plays an important role. Only type III radio bursts reaching the local plasma line measured at 1 AU are found to be related with an associated release episode in the low corona. Other type III bursts may also have a release of NR electrons associated with them, but these electrons do not reach L1. Long release episodes appear associated with signatures of long acceleration processes in the low corona (long decay of the soft X-ray emission, type IV radio bursts, and time-extended microwave emission). Type II radio bursts are reported for most of the events and do not provide a clear discrimination between short and long release timescales.

  6. Intermittency in the Photosphere and Corona above an Active Region

    NASA Astrophysics Data System (ADS)

    Abramenko, Valentyna; Yurchyshyn, Vasyl; Wang, Haimin

    2008-07-01

    Recent studies have demonstrated without doubt that the magnetic field in the photosphere and corona is an intermittent structure, opening new views of the underlying physics. In particular, such problems as the existence in the corona of localized areas with extremely strong resistivity (required to explain magnetic reconnection at all scales) and the interchange between small and large scales (required in the study of photospheric-coronal coupling), to name a few, can be easily captured by the concept of intermittency. This study focuses on simultaneous time variations of intermittency properties derived in the photosphere, chromosphere, and corona. We analyze data for NOAA Active Region 10930 acquired between 2006 December 8, 12:00 UT, and December 13, 18:45 UT. Photospheric intermittency is inferred from Hinode magnetic field measurements, while intermittency in the transition region and corona is derived from Nobeyama 9 GHz radio polarization measurements and high-cadence Hinode XRT (thin-Be) data, as well as GOES 1-8 Å flux. The photospheric dynamics and its possible relationship with the intermittency variations are also analyzed by calculating the kinetic vorticity. In this case study, we find the following chain of events: The intermittency of the photospheric magnetic field peaked after the specific kinetic vorticity of plasma flows in the active region reached its maximum (4 hr time delay). In turn, a gradual increase of coronal intermittency occurred after the peak of the photospheric intermittency. The time delay between the peak of photospheric intermittency and the occurrence of the first strong (X3.4) flare was approximately 1.3 days. Our analysis seems to suggest that the enhancement of intermittency/complexity first occurs in the photosphere and is later transported toward the corona.

  7. Fast Time Analysis of Intermittent Point-to-Plane Corona in Air. III. The Negative Point Trichel Pulse Corona

    Microsoft Academic Search

    M. R. AMINt

    1954-01-01

    Fast oscilloscopic time analysis of the negative point Trichel pulse corona in room air at various pressures and gap geometries reveals the following data. The very short rise and quenching time of the pulse at atmospheric pressure observed by English is confirmed. Under these conditions the secondary action is a photoelectric liberation from the cathode and discharge extinguishes by dissociative

  8. Onset voltage of negative corona on stranded conductors

    NASA Astrophysics Data System (ADS)

    El-Bahy, M. M.; Abouelsaad, M.; Abdel-Gawad, N.; Badawi, M.

    2007-05-01

    Theoretical investigation of the onset voltage of negative corona on stranded conductors is described in this paper. The method of calculation is based on the criterion developed for the formation of repetitive negative corona Trichel pulses. This calls first for an accurate calculation of the electric field in the vicinity of stranded conductors. The investigated gap is a three-dimensional field problem. To solve this problem, a new modification of the charge simulation technique is presented, where the simulation charges are helical of infinite length. Laboratory measurements of the onset voltage on stranded conductors are carried out to check the accuracy of the present calculations. The effects of varying the field nonuniformity on the onset voltage values are investigated. The calculated onset voltage values for stranded conductors agree satisfactorily with those measured experimentally.

  9. The degradation of organic dyes by corona discharge

    SciTech Connect

    Goheen, S.C.; McCulloch, M.; Durham, D.E.; Heath, W.O.

    1992-02-01

    Several dyes in water were individually exposed to corona discharge. Light absorbance decreased for all organic dyes with time. Absorbance losses with methylene blue, malachite green, and new coccine were studied. The loss of color was followed using an in situ colorimeter and the effects of varying the current, voltage, gas phase, stirring rates, salinity, and electrode spacing were investigated. The highest reaction rates were observed using the highest current, highest voltage (up to 10kV), highest stirring rate, lowest salinity, smallest electrode spacing, and an environment containing enhanced levels of oxygen. Current was higher in the presence of nitrogen than in the presence of oxygen (for the same voltage), but the reaction of methylene blue did not proceed unless oxygen was present. These results help identify conditions using corona discharge in which dyes, and potentially other organics, can be destroyed. 22 refs., 5 figs.

  10. Corona method and apparatus for altering carbon containing compounds

    SciTech Connect

    Sharma, A.K.; Camaioni, D.M.; Josephson, G.B.

    1999-11-09

    The present invention is a method and apparatus for altering a carbon containing compound in an aqueous mixture. According to a first aspect of the present invention, it has been discovered that for an aqueous mixture having a carbon containing compound with an ozone reaction rate less than the ozone reaction rate of pentachlorophenol, use of corona discharge in a low or non-oxidizing atmosphere increases the rate of destruction of the carbon containing compound compared to corona discharge an oxidizing atmosphere. For an aqueous mixture containing pentachlorophenol, there was essentially no difference in destruction between atmospheres. According to a second aspect of the present invention, it has been further discovered that an aqueous mixture having a carbon containing compound in the presence of a catalyst and oxygen resulted in an increased destruction rate of the carbon containing compound compared to no catalyst.

  11. Compton heated winds and coronae above accretion disks. I Dynamics

    NASA Technical Reports Server (NTRS)

    Begelman, M. C.; Mckee, C. F.; Shields, G. A.

    1983-01-01

    X rays emitted in the inner part of an accretion disk system can heat the surface of the disk farther out, producing a corona and possibly driving off a strong wind. The dynamics of Compton-heated coronae and winds are analyzed using an approximate two-dimensional technique to estimate the mass loss rate as a function of distance from the source of X rays. The findings have important dynamical implications for accretion disks in quasars, active galactic nuclei, X ray binaries, and cataclysmic variables. These include: mass loss from the disk possibly comparable with or exceeding the net accretion rate onto the central compact object, which may lead to unstable accretion; sufficient angular momentum loss in some cases to truncate the disk in a semidetached binary at a smaller radius than that predicted by tidal truncation theories; and combined static plus ram pressure in the wind adequate to confine line-emitting clouds in quasars and Seyfert galaxies.

  12. Corona Method And Apparatus For Altering Carbon Containing Compounds

    DOEpatents

    Sharma, Amit K. (Plainsboro, NJ); Camaioni, Donald M. (Richland, WA); Josephson; Gary B. (Richland, WA)

    2004-05-04

    The present invention is a method and apparatus for altering a carbon-containing compound in an aqueous mixture. According to a first aspect of the present invention, it has been discovered that for an aqueous mixture having a carbon containing compound with an ozone reaction rate less than the ozone reaction rate of pentachlorophenol, use of corona discharge in a low or non-oxidizing atmosphere increases the rate of destruction of the carbon containing compound compared to corona discharge an oxidizing atmosphere. For an aqueous mixture containing pentachlorphenol, there was essentially no difference in destruction between atmospheres. According to a second aspect of the present invention, it has been further discovered that an aqueous mixture having a carbon-containing compound in the presence of a catalyst and oxygen resulted in an increased destruction rate of the carbon containing compound compared to no catalyst.

  13. Corona method and apparatus for altering carbon containing compounds

    DOEpatents

    Sharma, Amit K. (Richland, WA); Camaioni, Donald M. (Richland, WA); Josephson, Gary B. (Richland, WA)

    1999-01-01

    The present invention is a method and apparatus for altering a carbon containing compound in an aqueous mixture. According to a first aspect of the present invention, it has been discovered that for an aqueous mixture having a carbon containing compound with an ozone reaction rate less than the ozone reaction rate of pentachlorophenol, use of corona discharge in a low or non-oxidizing atmosphere increases the rate of destruction of the carbon containing compound compared to corona discharge an oxidizing atmosphere. For an aqueous mixture containing pentachlorphenol, there was essentially no difference in destruction between atmospheres. According to a second aspect of the present invention, it has been further discovered that an aqueous mixture having a carbon containing compound in the presence of a catalyst and oxygen resulted in an increased destruction rate of the carbon containing compound compared to no catalyst.

  14. The Effect of a Corona Discharge on a Lightning Attachment

    SciTech Connect

    Aleksandrov, N.L. [Moscow Institute of Physics and Technology, Institutskii pr. 9, Dolgoprudnyi, Moscow oblast, 141700 (Russian Federation); Bazelyan, E.M. [Krzhizhanovskii Rower Engineering Institute, Leninskii pr. 19, Moscow, 117927 (Russian Federation); Raizer, Yu.P. [Institute for Problems of Mechanics, Russian Academy of Sciences, pr. Vernadskogo 101, Moscow, 117526 (Russian Federation)

    2005-01-15

    The interaction between the lightning leader and the space charge accumulated near the top of a ground object in the atmospheric electric field is considered using analytical and numerical models developed earlier to describe spark discharges in long laboratory gaps. The specific features of a nonstationary corona discharge that develops in the electric field of a thundercloud and a downward lightning leader are analyzed. Conditions for the development of an upward lightning discharge from a ground object and for the propagation of an upward-connecting leader from the object toward a downward lightning leader (the process determining the point of strike to the ground) are investigated. Possible mechanisms for the interaction of the corona space charge with an upward leader and prospects of using it to control downward lightning discharges are analyzed.

  15. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    2000-01-01

    This report covers technical progress during the third year of the NASA Space Physics Theory contract "The Structure and Dynamics of the Solar Corona," between NASA and Science Applications International Corporation, and covers the period June 16, 1998 to August 15, 1999. This is also the final report for this contract. Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the three-year duration of this contract we have published 49 articles in the scientific literature. These publications are listed in Section 3 of this report. In the Appendix we have attached reprints of selected articles. We summarize our progress during the third year of the contract. Full descriptions of our work can be found in the cited publications, a few of which are attached to this report.

  16. THE CONNECTION OF TYPE II SPICULES TO THE CORONA

    SciTech Connect

    Judge, Philip G.; McIntosh, Scott W. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States); De Pontieu, Bart [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover Street, Org. A021S, Building 252, Palo Alto, CA 94304 (United States); Olluri, Kosovare [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway)

    2012-02-20

    We examine the hypothesis that plasma associated with 'Type II' spicules is heated to coronal temperatures, and that the upward moving hot plasma constitutes a significant mass supply to the solar corona. One-dimensional hydrodynamical models including time-dependent ionization are brought to bear on the problem. These calculations indicate that heating of field-aligned spicule flows should produce significant differential Doppler shifts between emission lines formed in the chromosphere, transition region, and corona. At present, observational evidence for the computed 60-90 km s{sup -1} differential shifts is weak, but the data are limited by difficulties in comparing the proper motion of Type II spicules with spectral and kinematic properties of an associated transition region and coronal emission lines. Future observations with the upcoming infrared interferometer spectrometer instrument should clarify if Doppler shifts are consistent with the dynamics modeled here.

  17. Coronal inflows as evidence for reconnection in the outer corona

    Microsoft Academic Search

    Y.-M. Wang

    2004-01-01

    We describe the inflows observed with the SOHO\\/LASCO white-light coronagraph and discuss their relevance to the closing-down of magnetic flux in the corona. The inflows are not seen above 6 R_&sun; from Sun center, which appears to be a point of no return for the Sun's plasmas and fields. Some inflows have characteristics (like fast, oppositely directed ejections) that are

  18. Observation of Ultrafine Channels of Solar Corona Heating

    NASA Astrophysics Data System (ADS)

    Ji, Haisheng; Cao, Wenda; Goode, Philip R.

    2012-05-01

    We report the first direct observations of dynamical events originating in the Sun's photosphere and subsequently lighting up the corona. Continuous small-scale, impulsive events have been tracked from their origin in the photosphere on through to their brightening of the local corona. We achieve this by combining high-resolution ground-based data from the 1.6 m aperture New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO), and satellite data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The NST imaging observations in helium I 10830 Å reveal unexpected complexes of ultrafine, hot magnetic loops seen to be reaching from the photosphere to the base of the corona. Most of these ultrafine loops are characterized by an apparently constant, but surprisingly narrow diameter of about 100 km all along each loop, and the loops originate on the solar surface from intense, compact magnetic field elements. The NST observations detect the signature of upward injections of hot plasma that excite the ultrafine loops from the photosphere to the base of the corona. The ejecta have their individual footpoints in the intergranular lanes between the Sun's ubiquitous, convectively driven granules. In many cases, AIA/SDO detects cospatial and cotemporal brightenings in the overlying, million degree coronal loops in conjunction with the upward injections along the ultrafine loops. Segments of some of the more intense upward injections are seen as rapid blueshifted events in simultaneous H? blue wing images observed at BBSO. In sum, the observations unambiguously show impulsive coronal heating events from upward energy flows originating from intergranular lanes on the solar surface accompanied by cospatial mass flows.

  19. Method and apparatus for processing exhaust gas with corona discharge

    DOEpatents

    Barlow, S.E.; Orlando, T.M.; Tonkyn, R.G.

    1999-06-22

    The present invention is placing a catalyst coating upon surfaces surrounding a volume containing corona discharge. In addition, the electrodes are coated with a robust dielectric material. Further, the electrodes are arranged so that at least a surface portion of each electrode extends into a flow path of the exhaust gas to be treated and there is only exhaust gas in the volume between each pair of electrodes. 12 figs.

  20. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    1998-01-01

    Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the period covered by this report we have published 17 articles in the scientific literature. These publications are listed in Section 4 of this report. In the Appendix we have attached reprints of selected articles.

  1. Estimation of winding insulation resistance to the corona discharges

    NASA Astrophysics Data System (ADS)

    Leonov, A.; Red'ko, V.; Soldatenko, E.

    2014-10-01

    This article presents test results of enameled winding wires, characterizing an insulation electrical and mechanical strength. Standard and original test methods were used. Note that existing standard test methods do not estimate enamel insulation resistance to the electrical loads under winding operation of variable-speed drive. We show that estimation of wire corona resistance can be done by high frequency electrical impulse testing. Wire insulation plays the main role of reliability of insulation system.

  2. Electrical Auxiliary Power Unit (EAPU) Corona Design Guideline. Revised

    NASA Technical Reports Server (NTRS)

    Hall, David K.; Kirkici, Hulya; Schweickart, Dan L.; Dunbar, William; Hillard, Barry

    2000-01-01

    This document is the result of a collaborative effort between NASA's Johnson Space Center, Marshall Space Flight Center, Glenn Research Center, and the United States Air Force Research Laboratory at Wright Patterson AFB in support of the Space Shuttle Orbiter Upgrades Program, specifically the Electric Auxiliary Power Unit Program. This document is intended as a guideline for design applications for corona and partial discharge avoidance and is not a requirements specification instrument.

  3. Method and apparatus for processing exhaust gas with corona discharge

    DOEpatents

    Barlow, Stephan E. (Richland, WA); Orlando, Thomas M. (Kennewick, WA); Tonkyn, Russell G. (Kennewick, WA)

    1999-01-01

    The present invention is placing a catalyst coating upon surfaces surrounding a volume containing corona discharge. In addition, the electrodes are coated with a robust dielectric material. Further, the electrodes are arranged so that at least a surface portion of each electrode extends into a flow path of the exhaust gas to be treated and there is only exhaust gas in the volume between each pair of electrodes.

  4. Collisional damping of surface waves in the solar corona

    NASA Technical Reports Server (NTRS)

    Gordon, B. E.; Hollweg, J. V.

    1982-01-01

    The damping of surface waves by viscosity and heat conduction is evaluated. For the solar corona, it is found that surface waves dissipate efficiently only if their periods are shorter than a few tens of seconds and only if the background magnetic field is less than about 10 Gauss. Heating of quiet coronal regions is possible if the coronal waves have short periods, but they cannot heat regions of strong magnetic field, such as coronal active region loops.

  5. Magnetic fields and the structure of the solar corona

    Microsoft Academic Search

    Martin D. Altschuler; Gordon Newkirk

    1969-01-01

    Several different mathematical methods are described which use the observed line-of-sight component of the photospheric magnetic field to determine the magnetic field of the solar corona in the current-free (or potential-field) approximation. Discussed are (1) a monopole method, (2) a Legendre polynomial expansion assuming knowledge of the radial photospheric magnetic field, (3) a Legendre polynomial expansion obtained from the line-of-sight

  6. ESTIMATING THE ''DARK'' ENERGY CONTENT OF THE SOLAR CORONA

    SciTech Connect

    McIntosh, Scott W. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); De Pontieu, Bart, E-mail: mscott@ucar.edu [Lockheed Martin Solar and Astrophysics Lab, 3251 Hanover St., Org. A021S, Bldg. 252, Palo Alto, CA 94304 (United States)

    2012-12-20

    The discovery of ubiquitous low-frequency (3-5 mHz) Alfvenic waves in the solar chromosphere (with Hinode/Solar Optical Telescope) and corona (with CoMP and SDO) has provided some insight into the non-thermal energy content of the outer solar atmosphere. However, many questions remain about the true magnitude of the energy flux carried by these waves. Here we explore the apparent discrepancy in the resolved coronal Alfvenic wave amplitude ({approx}0.5 km s{sup -1}) measured by the Coronal Multi-channel Polarimeter (CoMP) compared to those of the Hinode and the Solar Dynamics Observatory (SDO) near the limb ({approx}20 km s{sup -1}). We use a blend of observational data and a simple forward model of Alfvenic wave propagation to resolve this discrepancy and determine the Alfvenic wave energy content of the corona. Our results indicate that enormous line-of-sight superposition within the coarse spatio-temporal sampling of CoMP hides the strong wave flux observed by Hinode and SDO and leads to the large non-thermal line broadening observed. While this scenario has been assumed in the past, our observations with CoMP of a strong correlation between the non-thermal line broadening with the low-amplitude, low-frequency Alfvenic waves observed in the corona provide the first direct evidence of a wave-related non-thermal line broadening. By reconciling the diverse measurements of Alfvenic waves, we establish large coronal non-thermal line widths as direct signatures of the hidden, or ''dark'', energy content in the corona and provide preliminary constraints on the energy content of the wave motions observed.

  7. OBSERVATION OF ULTRAFINE CHANNELS OF SOLAR CORONA HEATING

    SciTech Connect

    Ji, Haisheng [Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, CAS, Nanjing 210008 (China); Cao, Wenda; Goode, Philip R. [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

    2012-05-01

    We report the first direct observations of dynamical events originating in the Sun's photosphere and subsequently lighting up the corona. Continuous small-scale, impulsive events have been tracked from their origin in the photosphere on through to their brightening of the local corona. We achieve this by combining high-resolution ground-based data from the 1.6 m aperture New Solar Telescope (NST) at Big Bear Solar Observatory (BBSO), and satellite data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The NST imaging observations in helium I 10830 A reveal unexpected complexes of ultrafine, hot magnetic loops seen to be reaching from the photosphere to the base of the corona. Most of these ultrafine loops are characterized by an apparently constant, but surprisingly narrow diameter of about 100 km all along each loop, and the loops originate on the solar surface from intense, compact magnetic field elements. The NST observations detect the signature of upward injections of hot plasma that excite the ultrafine loops from the photosphere to the base of the corona. The ejecta have their individual footpoints in the intergranular lanes between the Sun's ubiquitous, convectively driven granules. In many cases, AIA/SDO detects cospatial and cotemporal brightenings in the overlying, million degree coronal loops in conjunction with the upward injections along the ultrafine loops. Segments of some of the more intense upward injections are seen as rapid blueshifted events in simultaneous H{alpha} blue wing images observed at BBSO. In sum, the observations unambiguously show impulsive coronal heating events from upward energy flows originating from intergranular lanes on the solar surface accompanied by cospatial mass flows.

  8. Effects of absorbing particles on coronas and glories

    NASA Astrophysics Data System (ADS)

    Vollmer, Michael

    2005-09-01

    Light scattering from small particles changes if the particles are absorbing. Whereas the effect is small for coronas and Bishop's ring, glories show pronounced attenuation with increasing absorption. Results indicate suitable wavelength regions for studies of glory scattering from cloud tops. The behavior of core-shell particles could have applications for studying the atmosphere of Venus; in addition it provides more insight into the simple ray-path model of the glory.

  9. Kilometre-Scale Structures in the Sun's Corona

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1996-01-01

    Knowledge of the structure of the Sun's corona is important for our understanding of how this high-temperature plasma is heated, and of the processes involved in the acceleration of the solar wind. The structure can be investigated directly by imaging at optical and shorter wavelengths, or indirectly through the effects of changing electron density on the propagation of radio waves (scattering and scintillation). Radio measurements have established many of the characteristics of the density fluctuations in the corona and solar wind, but the fundamental nature of these structures is not yet fully understood. Two specific features that have proved difficult to explain are an abrupt increase in anisotropy of the irregularities close to the Sun, and a break in the power-law spectrum describing the density fluctuations. Here I argue that these features are the manifestation of a transition from small ray-like or filamentary structures in the corona that rotate with the Sun to turbulent density irregularities convecting with the solar wind. I estimate the size of the smallest filamentary structure within coronal holes to be about I km at the Sun, approximately three orders of magnitude smaller than the smallest filamentary structures observed in images of different wavelengths.

  10. Soot oxidation in a corona plasma-catalytic reactor

    NASA Astrophysics Data System (ADS)

    Ranji-Burachaloo, H.; Masoomi-Godarzi, S.; Khodadadi, A. A.; Vesali-Naseh, M.; Mortazavi, Y.

    2014-08-01

    Oxidation of soot by corona plasma was investigated at conditions of exhaust gases from diesel engines, both in the absence and presence of CoOx as a catalyst. The CoOx catalyst nanoparticles were synthesized by a precipitation method. The BET surface area of the catalyst was 50 m2/g, corresponding to 23 nm particles. An aluminum grid was sequentially dip-coated for several times by suspensions of the soot in toluene and/or fine catalyst powder in DI water. The grid was used as the plate of a pin-to-plate corona reactor. Air at 180 °C was passed through the corona reactor to oxidize the soot, oxidation products of which were analyzed by both gas chromatograph and FTIR with a gas cell. Soot oxidation rate linearly increased with an increase of input energy. When the soot was deposited on a layer of the CoOx catalyst, the soot oxidation rate increased up to 2 times. The only product of the plasma (catalytic) oxidation of soot was CO2 determined by FTIR. O produced in the plasma discharge oxidized the soot and the active surface oxygen enhanced its rate.

  11. Radiative-hydrodynamical simulations of accretion disk coronae

    NASA Technical Reports Server (NTRS)

    Melia, Fulvio; Zylstra, Gregory J.; Fryxell, Bruce

    1991-01-01

    An algorithm has been developed that will carry out detailed, two-dimensional, fully self-consistent radiative-hydrodynamical simulations of accretion disk coronae in X-ray-luminous compact sources. The calculation reported here, for an accreting neutron star radiating at 0.5 times the Eddington luminosity, reveals several striking features. (1) The corona is comprised of two main regions - an inner highly dynamic portion whose vertical structure varies cyclically on a dynamical time scale, and an outer, more stable zone in which the evaporated plasma rises to form a 'sheath' that gradually merges into a wind at large radii. (2) The coronal structure shows a density inversion that contrasts sharply with the Gaussian profiles of earlier hydrostatic models. (3) Interestingly, flow velocities as high as a few billion cm/s are not uncommon in portions of the corona. The relevance of this point to the large measured width of the emission features seen in low-mass X-ray binaries and the Galactic black hole candidates is discussed.

  12. Pair-density transitions in accretion disk coronae

    NASA Technical Reports Server (NTRS)

    Kusunose, Masaaki; Mineshige, Shin

    1991-01-01

    The thermal and e(+)e(-)-pair equilibrium structure of two-temperature disk coronae above a cool (about 10 exp 6 K) disk around a black hole of 10 solar masses are investigated. Soft photons are assumed to be amply supplied from the cool disk. Two-pair thermal equilibrium points are found for a given proton column density: the low state with very small pair density and the high state dominated by pairs. Both states are thermally unstable, while for perturbations in pair density the high state is unstable and the low state is stable. Two possible scenarios are discussed for the fate of a two-temperature corona. When the proton optical depth is relatively small (e.g., less than 1) and the temperature of input soft photons is low (e.g., less than 10 exp 6 K), the corona will undergo a limit cycle between the high state and the low state on a time scale of milliseconds. As a consequence of Compton scattering of the soft photons, the emergent spectrum in the high state is rather flat with a big Wien bump at about 100 keV, whereas it is composed of a power-law component in the low state. Some observational consequences are briefly discussed in connection with the high-low spectral transition in Cyg X-1.

  13. THE CYCLING OF MATERIAL BETWEEN THE SOLAR CORONA AND CHROMOSPHERE

    SciTech Connect

    Guerreiro, N.; Hansteen, Viggo [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); De Pontieu, B., E-mail: n.m.r.guerreiro@astro.uio.no [Lockheed Martin Solar and Astrophysics Laboratory, Org. A021S, Building 252, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

    2013-05-20

    Observations of transition region emission lines reveal the presence of redshifts in lines formed from the top of the chromosphere up to temperatures of about 2.5 Multiplication-Sign 10{sup 5} K and blueshifts for temperatures above that. However, it is doubtful that the apparent large downward flows in the lower transition region represents an emptying of the corona, so some mechanism must be responsible for maintaining the mass balance between the corona and the lower atmospheric layers. We use a three-dimensional magnetohydrodynamics code to study the cycling of mass between the corona, transition region, and chromosphere by adding a tracer fluid to the simulation in various temperature intervals in the transition region. We find that most of the material seen in transition region emission lines formed at temperatures below 3 Multiplication-Sign 10{sup 5} K is material that has been rapidly heated from chromospheric temperatures and thereafter is pushed down as it cools. This implies that the bulk of transition region material resides in small loops. In these loops, the density is high and radiative cooling is efficient.

  14. Current-voltage characteristics of dc corona discharges in air between coaxial cylinders

    NASA Astrophysics Data System (ADS)

    Zheng, Yuesheng; Zhang, Bo; He, Jinliang

    2015-02-01

    This paper presents the experimental measurement and numerical analysis of the current-voltage characteristics of dc corona discharges in air between coaxial cylinders. The current-voltage characteristics for both positive and negative corona discharges were measured within a specially designed corona cage. Then the measured results were fitted by different empirical formulae and analyzed by the fluid model. The current-voltage characteristics between coaxial cylinders can be expressed as I = C(U - U0)m, where m is within the range 1.5-2.0, which is similar to the point-plane electrode system. The ionization region has no significant effect on the current-voltage characteristic under a low corona current, while it will affect the distribution for the negative corona under a high corona current. The surface onset fields and ion mobilities were emphatically discussed.

  15. A numerical simulation of Trichel-pulse formation in a negative corona

    NASA Astrophysics Data System (ADS)

    Napartovich, A. P.; Akishev, Yu S.; Deryugin, A. A.; Kochetov, I. V.; Pan'kin, M. V.; Trushkin, N. I.

    1997-10-01

    A new quasi-one-dimensional model for a negative corona in air is formulated allowing for the quantitative description of the mechanism of Trichel-pulse formation. Detailed analysis of the processes controlling pulse dynamics is made. Comparison with experiment for a short-gap corona demonstrates a reasonable agreement with the shape of the pulse and in the average characteristics of the negative corona.

  16. A numerical simulation of Trichel-pulse formation in a negative corona

    Microsoft Academic Search

    A. P. Napartovich; Yu S. Akishev; A. A. Deryugin; I. V. Kochetov; M. V. Pan'kin; N. I. Trushkin

    1997-01-01

    A new quasi-one-dimensional model for a negative corona in air is formulated allowing for the quantitative description of the mechanism of Trichel-pulse formation. Detailed analysis of the processes controlling pulse dynamics is made. Comparison with experiment for a short-gap corona demonstrates a reasonable agreement with the shape of the pulse and in the average characteristics of the negative corona.

  17. Corona inception voltage in statorettes with various gas-solid dielectric systems

    NASA Technical Reports Server (NTRS)

    Bollenbacher, G.; Kempke, E. E., Jr.

    1972-01-01

    Corona inception voltage was calculated and measured for three statorettes in several gases and gas mixtures at pressures from 50.8 to 1270 torr. In helium the corona inception voltage was lowest, and in air it was highest. In argon and mixtures of helium and xenon the corona inception voltage was between that of air and helium. Correlation between experimental and calculated data was good.

  18. Coronas in olivine gabbros and iron ores from Susimäki and Riuttamaa, Finland

    Microsoft Academic Search

    Hans van Lamoen

    1979-01-01

    Coronas have been studied by petrographie and microprobe techniques in metamorphosed olivine gabbros and associated iron ores\\u000a from Susimäki and Riuttamaa in Southwest Finland. Three types of coronas are distinguished occurring between the following\\u000a primary minerals: (1) olivine-plagioclase, (2) opaque oxides-plagioclase, (3) opaque oxides-clinopy-roxene. Secondary corona\\u000a minerals are, in order of decreasing abundance, hornblende, orthopyroxene, spinel, olivine, ilmenite, and magnetite.

  19. Control of soot emission of a turbulent diffusion flame by DC or AC corona discharges

    Microsoft Academic Search

    Hiromichi Ohisa; Itsuro Kimura; Hideyuki Horisawa

    1999-01-01

    The effects of DC or AC (14 kHz) corona discharges, formed between tips of opposed needle electrodes, on soot emission of a propane turbulent diffusion flame were investigated experimentally. It is shown that when a DC corona discharge (e.g., 3.6 W; 0.06% of the combustion energy released by the flame) or a discharge system composed of three AC coronas (e.g.,

  20. Somatosensory evoked potential studies in internal capsule and corona radiata infarction

    Microsoft Academic Search

    J. Kalita; U. K. Misra

    1998-01-01

    To document the somatosensory evoked potential (SEP) changes in capsular and corona radiata infarction and correlate these\\u000a with clinical and radiological findings, 15 patients with corona radiata and 16 with internal capsular infarction were studied.\\u000a The mean age of the patients was 55 years (range 26–80), and 6 of them were female. In the patients with corona radiata infarction,\\u000a median

  1. Unveiling the nature of coronae in active galactic nuclei through submillimeter observations

    NASA Astrophysics Data System (ADS)

    Inoue, Yoshiyuki; Doi, Akihiro

    2014-12-01

    The heating mechanism of a corona above an accretion disk in active galactic nuclei (AGNs) is still unknown. One possible mechanism is magnetic reconnection heating requiring energy equipartition between magnetic energy and gas energy in the disk. Here, we investigate the expected observed properties in the radio band from such a magnetized corona. A magnetized corona can generate synchrotron radiation since a huge amount of electrons exists. Although most of the radiation would be absorbed by synchrotron self-absorption, high-frequency end of synchrotron emission can escape from a corona and appear at the submillimeter range. If only thermal electrons exist in a corona, the expected flux from nearby Seyferts is below the Atacama Large Millimeter/submillimeter Array (ALMA) sensitivity. However, if non-thermal electrons coexist in a corona, ALMA can measure the non-thermal tail of the synchrotron radiation from a corona. Such a non-thermal population is naturally expected to exist if the corona is heated by magnetic reconnections. Future ALMA observations will directly probe the coronal magnetic field strength and the existence of non-thermal electrons in coronae of AGNs.

  2. Unraveled mechanism in silk engineering: Fast reeling induced silk Xiang Wu,1,2

    E-print Network

    Li, Baowen

    Unraveled mechanism in silk engineering: Fast reeling induced silk toughening Xiang Wu,1,2 Xiang response of silkworm and spider silks against stretching and the relationship with the underlying and textile applications. © 2009 American Institute of Physics. DOI: 10.1063/1.3216804 Spider silk is superior

  3. Unravelling the Sources of Adolescent Substance Use: A Test of Rival Theories

    ERIC Educational Resources Information Center

    Jonson, Cheryl Lero; McArthur, Rachel; Cullen, Francis T.; Wilcox, Pamela

    2012-01-01

    Among any cohort of American youths, some will use drugs and alcohol whereas others will not. Further, some youngsters will not only use these illegal substances but also abuse them, at times wreaking havoc with their lives and ruining their futures. The purpose of this study is to attempt to unravel this heterogeneity of substance abuse; that is,…

  4. Mechanistic Studies Unravel the Complexity Inherent in Tau Aggregation Leading to Alzheimer's Disease and the Tauopathies

    E-print Network

    Mechanistic Studies Unravel the Complexity Inherent in Tau Aggregation Leading to Alzheimer of the protein tau into amyloid fibrils is known to be involved in the causation of the neurodegenerative tauopathies and the progression of cognitive decline in Alzheimer's disease. This review surveys the mechanism

  5. Unraveling the Relationship between Organizational Career Management and the Need for External Career Counseling

    ERIC Educational Resources Information Center

    Verbruggen, Marijke; Sels, Luc; Forrier, Anneleen

    2007-01-01

    This article unravels the relationship between organizational career management and the need for external career counseling. We conducted a path analysis using data of 803 Flemish employees. The results indicate a three-way relationship between organizational career management and external career counseling. First, experiencing organizational…

  6. The Mechanisms Involved in Seed Dormancy Alleviation by Hydrogen Cyanide Unravel the Role of Reactive

    E-print Network

    Leubner, Gerhard

    of the ethylene signaling pathway. We propose that ROS play a key role in the control of sunflower seed in the alleviation of embryo dormancy in sunflower seeds. Interestingly, this dormancy breaking effect of cyanideThe Mechanisms Involved in Seed Dormancy Alleviation by Hydrogen Cyanide Unravel the Role

  7. PHASES IN THE UNRAVELING OF THE SECRETS OF THE GEAR SYSTEM OF THE ANTIKYTHERA MECHANISM. 1

    E-print Network

    PHASES IN THE UNRAVELING OF THE SECRETS OF THE GEAR SYSTEM OF THE ANTIKYTHERA MECHANISM. 1 Teun Museum in Athens. Traces of gear- wheels were clearly visible as well. The pieces turned out to be parts of the gearing system. 1 This is the text of a lecture given at the International Symposium on the History

  8. Doing Class Analysis in Singapore's Elite Education: Unravelling the Smokescreen of "Meritocratic Talk"

    ERIC Educational Resources Information Center

    Koh, Aaron

    2014-01-01

    This paper examines the specificity of the education-class nexus in an elite independent school in Singapore. It seeks to unravel the puzzle that meritocracy is dogmatically believed in Singapore in spite of evidences that point to the contrary. The paper draws on discursive (analysis of media materials) and institutional (analysis of interview…

  9. The unravelling of metabolic dysfunctions linked to metal-associated diseases by blue native

    E-print Network

    Appanna, Vasu

    REVIEW The unravelling of metabolic dysfunctions linked to metal-associated diseases by blue native- turing of the analytes prior to their analysis, blue native poly- acrylamide gel electrophoresis (BN perturbations invoked by metal toxicity. In this review, we elaborate on how BN-PAGE has led to the discovery

  10. Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions Unraveling Relaxor Phase Transitions by

    E-print Network

    Osnabrück, Universität

    Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions Unraveling Relaxor 2009 WILLIAMSBURG WORKSHOP ON FUNDAMENTAL PHYSICS OF FERROELECTRICS #12;Introduction Strontium Barium ferroelectrics Introduction Strontium Barium Niobate k-Space Spectroscopy Results Conclusions SBN ­ SrxBa1-xNb2O6

  11. Symptoms of Eating Disorders Among Female Distance Runners: Can the Inconsistencies Be Unraveled?

    Microsoft Academic Search

    Donald H. Ryujin; Cynthia Breaux; Amanda D. Marks

    2000-01-01

    Research on eating disorders among female distance runners has produced a modest, but inconsistent body of findings. To unravel the confusion, we hypothesized a model whereby studies finding greater symptomatology have involved obligatory runners or elite national\\/international competitors. Studies not finding greater symptomatology have involved a more typical group of athletes. To test our hypothesis, we used the Eating Disorders

  12. Changes in clinical practice with the unravelling of diseases: Connective-tissue disorders

    Microsoft Academic Search

    J. Spranger; Gregor Mendel; Circle Greenwood

    2001-01-01

    Unravelling of diseases is achieved in steps by sequentially describing their phenotype, natural course, aetiology and pathogenesis. Through succinct clinical observation, conglomerates of heterogeneous connective-tissue disorders, such as various forms of disproportionate dwarfism, have been split into well-defined entities. They have often been confirmed by biochemical and molecular analysis. On the other hand, seemingly disparate disorders have been shown to

  13. Using genomic data to unravel the root of the placental mammal phylogeny

    E-print Network

    Miller, Webb

    Using genomic data to unravel the root of the placental mammal phylogeny William J. Murphy,1 Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College, University of California, Riverside, California 92521, USA; 4 Center for Comparative Genomics

  14. Viewpoint Paper Unraveling the defect chemistry and proton uptake of yttrium-doped

    E-print Network

    Viewpoint Paper Unraveling the defect chemistry and proton uptake of yttrium-doped barium zirconate Abstract--A review of the experimental literature documenting water uptake in yttrium-doped barium uptake; Defect chemistry; Fuel cells 1. Introduction Amongst proton-conducting oxides, yttrium

  15. Oxygen Isotopes Unravel the Role of Microorganisms in Phosphate Cycling in Soils

    E-print Network

    Gilli, Adrian

    Oxygen Isotopes Unravel the Role of Microorganisms in Phosphate Cycling in Soils Federica Tamburini analyzed the isotopic composition of oxygen in phosphate (18 O-Pi) from the parent material, soil for the temperature- dependent equilibrium between phosphate and water. In addition, the isotopic signature

  16. Unravelling the Cretaceous-Paleogene (KT) Turnover, Evidence from Flora, Fauna and

    E-print Network

    Vajda, Vivi

    Unravelling the Cretaceous-Paleogene (KT) Turnover, Evidence from Flora, Fauna and Geology Adriana and geological signatures left by the devastation, including information from new proximal KT boundary exposures well with the atmospheric radiative transfer models. The pattern of vertebrate extinctions revealed

  17. Unraveling the early steps of prokaryotic replication Erin L Cunningham and James M Berger

    E-print Network

    Berger, James M.

    Unraveling the early steps of prokaryotic replication Erin L Cunningham and James M Berger In prokaryotes, many of the physical mechanisms governing the process of initiating DNA replication are now studies have shown that prokaryotic initiator structures are both modular and conserved, and have begun

  18. Constant cross section of loops in the solar corona

    NASA Astrophysics Data System (ADS)

    Peter, H.; Bingert, S.

    2012-12-01

    Context. The corona of the Sun is dominated by emission from loop-like structures. When observed in X-ray or extreme ultraviolet emission, these million K hot coronal loops show a more or less constant cross section. Aims: In this study we show how the interplay of heating, radiative cooling, and heat conduction in an expanding magnetic structure can explain the observed constant cross section. Methods: We employ a three-dimensional magnetohydrodynamics (3D MHD) model of the corona. The heating of the coronal plasma is the result of braiding of the magnetic field lines through footpoint motions and subsequent dissipation of the induced currents. From the model we synthesize the coronal emission, which is directly comparable to observations from, e.g., the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (AIA/SDO). Results: We find that the synthesized observation of a coronal loop seen in the 3D data cube does match actually observed loops in count rate and that the cross section is roughly constant, as observed. The magnetic field in the loop is expanding and the plasma density is concentrated in this expanding loop; however, the temperature is not constant perpendicular to the plasma loop. The higher temperature in the upper outer parts of the loop is so high that this part of the loop is outside the contribution function of the respective emission line(s). In effect, the upper part of the plasma loop is not bright and thus the loop actually seen in coronal emission appears to have a constant width. Conclusions: From this we can conclude that the underlying field-line-braiding heating mechanism provides the proper spatial and temporal distribution of the energy input into the corona - at least on the observable scales. Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org

  19. Observational capabilities of solar satellite "Coronas-Photon"

    NASA Astrophysics Data System (ADS)

    Kotov, Yu.

    Coronas-Photon mission is the third satellite of the Russian Coronas program on solar activity observation The main goal of the Coronas-Photon is the study of solar hard electromagnetic radiation in the wide energy range from UV up to high energy gamma-radiation sim 2000MeV Scientific payload for solar radiation observation consists of three type of instruments 1 monitors Natalya-2M Konus-RF RT-2 Penguin-M BRM Phoka Sphin-X Sokol for spectral and timing measurements of full solar disk radiation with timing in flare burst mode up to one msec Instruments Natalya-2M Konus-RF RT-2 will cover the wide energy range of hard X-rays and soft Gamma rays 15keV to 2000MeV and will together constitute the largest area detectors ever used for solar observations Detectors of gamma-ray monitors are based on structured inorganic scintillators with energy resolution sim 5 for nuclear gamma-line band to 35 for GeV-band PSD analysis is used for gamma neutron separation for solar neutron registration T 30MeV Penguin-M has capability to measure linear polarization of hard X-rays using azimuth are measured by Compton scattering asymmetry in case of polarization of an incident flux For X-ray and EUV monitors the scintillation phoswich detectors gas proportional counter CZT assembly and Filter-covered Si-diodes are used 2 Telescope-spectrometer TESIS for imaging solar spectroscopy in X-rays with angular resolution up to 1 in three spectral lines and RT-2 CZT assembly of CZT

  20. Prediction of Dn-Resonances in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Osherovich, V. A.; Fainberg, J.; Benson, R. F.; MacDowall, R.; Reinisch, B. W.

    2006-05-01

    A new plasma wave mode has been proposed with quantized frequencies fDn = 3/?(fpefce)½ n½ , n = 1,2,... where fpe is the electron plasma frequency and fce is the electron gyrofrequency. These frequencies have been associated with a spectrum of emissions known as the Dn resonance stimulated by ionospheric topside sounders [Osherovich, 1987]. The foundations and observational support for this new electromagnetic mode have been summarized in the recent review by Osherovich et al. [2005] for three plasmas: the Earth's ionosphere (topside radio sounding from Alouette 2, ISIS 1 and ISIS 2 satellites), the Earth's magnetosphere (radio sounding from the IMAGE spacecraft) and in Jupiter's Io plasma torus (radio sounding from the Ulysses space probe). For these plasmas, the electron densities, magnetic fields and electron temperatures are quite different but in each of these plasmas there exists extended regions where the range of fpe/fce is roughly the same, namely 1? fpe/fce ? 8. From available observations of the solar corona and coronal loops, we conclude that the two-million degree corona is the fourth example of a magnetized plasma containing extended regions with fpe/fce in the same range. Therefore we predict the presence of Dn resonances with their distinctive ? n frequency spectrum, in the solar corona. References: Osherovich, V.A.,"Physical nature of diffuse plasma resonances in the ionosphere", J. Geophys. Res, 92, 316-320, 1987. Osherovich, V.A., R.F. Benson and J. Fainberg, "Electromagnetic bounded states and challenges of plasma spectroscopy", IEEE Transactions of Plasma Science, 33(2), 2005.

  1. Negative coronas: Low current mode pulse mode transition

    NASA Astrophysics Data System (ADS)

    Repän, V.; Laan, M.; Paris, P.; Aarik, J.; Sammelselg, V.

    1999-02-01

    In the paper the results of experimental study of negative corona in a point - plane gap in a dust-free air flow at atmospheric pressure are presented. Both the low current mode (LCM) of the discharge and Trichel pulses are externally triggered by UV light. Close to the inception voltage of Trichel pulses short-duration current spikes appear besides the steady component of the LCM which indicates to the switch-on of Fowler-Nordheim type emission mechanism. At the inception voltage spike - Trichel pulse transition is recorded. The influence of dielectric layers at the cathode on the discharge parameters is discussed.

  2. The Structure and Dynamics of the Solar Corona

    NASA Technical Reports Server (NTRS)

    Mikic, Zoran

    1998-01-01

    This report covers technical progress during the first year of the NASA Space Physics Theory contract between NASA and Science Applications International Corporation. Under this contract SAIC, the University of California, Irvine (UCI), and the Jet Propulsion Laboratory (JPL), have conducted research into theoretical modeling of active regions, the solar corona, and the inner heliosphere, using the MHD model. During the period covered by this report we have published 26 articles in the scientific literature. These publications are listed in Section 4 of this report. In the Appendix we have attached reprints of selected articles.

  3. Optical Spectroscopy at Deep Light Minimum of R Coronae Borealis

    NASA Astrophysics Data System (ADS)

    Howell, Steve B.; Rector, Travis A.; Walter, Donald

    2013-08-01

    We present optical spectroscopy late in a deep minimum for the quintessential hydrogen-deficient carbon star R Coronae Borealis. Starting 3.5 years into the current deep and long minimum, we have secured observations that reveal some of the oddest optical spectra ever obtained for any astronomical object. Helium emission lines from triplet transitions, strong Ca II H and K emission, and forbidden lines of oxygen and nitrogen are the only spectral features observed. The spectra can be interpreted as coming from a chromospheric-like region lying above a carbon shell ejection front combined with a large-scale nebular-like region surrounding the star.

  4. Ejection of cool plasma into the hot corona

    NASA Astrophysics Data System (ADS)

    Zacharias, P.; Peter, H.; Bingert, S.

    2011-08-01

    Context. The corona is highly dynamic and shows transient events on various scales in space and time. Most of these features are related to changes in the magnetic field structure or impulsive heating caused by the conversion of magnetic to thermal energy. Aims: We investigate the processes that lead to the formation, ejection and fall of a confined plasma ejection that was observed in a numerical experiment of the solar corona. By quantifying physical parameters such as mass, velocity, and orientation of the plasma ejection relative to the magnetic field, we provide a description of the nature of this particular plasma ejection. Methods: The time-dependent three-dimensional magnetohydrodynamic (3D MHD) equations are solved in a box extending from the chromosphere, which serves as a reservoir for mass and energy, to the lower corona. The plasma is heated by currents that are induced through field line braiding as a consequence of photospheric motions included in the model. Spectra of optically thin emission lines in the extreme ultraviolet range are synthesized, and magnetic field lines are traced over time. We determine the trajectory of the plasma ejection and identify anomalies in the profiles of the plasma parameters. Results: Following strong heating just above the chromosphere, the pressure rapidly increases, leading to a hydrodynamic explosion above the upper chromosphere in the low transition region. The explosion drives the plasma, which needs to follow the magnetic field lines. The ejection is then moving more or less ballistically along the loop-like field lines and eventually drops down onto the surface of the Sun. The speed of the ejection is in the range of the sound speed, well below the Alfvén velocity. Conclusions: The plasma ejection observed in a numerical experiment of the solar corona is basically a hydrodynamic phenomenon, whereas the rise of the heating rate is of magnetic nature. The granular motions in the photosphere lead (by chance) to a strong braiding of the magnetic field lines at the location of the explosion that in turn is causing strong currents which are dissipated. Future studies need to determine if this process is a ubiquitous phenomenon on the Sun on small scales. Data from the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (AIA/SDO) might provide the relevant information. Appendix and movie are available in electronic form at http://www.aanda.org

  5. Oxidation of aqueous pharmaceuticals by pulsed corona discharge.

    PubMed

    Panorel, Iris; Preis, Sergei; Kornev, Iakov; Hatakka, Henry; Louhi-Kultanen, Marjatta

    2013-01-01

    Oxidation of aromatic compounds of phenolic (paracetamol, beta-oestradiol and salicylic acid) and carboxylic (indomethacin and ibuprofen) structure used in pharmaceutics was studied. Aqueous solutions were treated with pulsed corona discharge (PCD) as a means for advanced oxidation. Pulse repetition frequency, delivered energy dose and oxidation media were the main parameters studied for their influence on the process energy efficiency. The PCD treatment appeared to be effective in oxidation of the target compounds: complete degradation of pollutant together with partial mineralization was achieved at moderate energy consumption; oxidation proceeds faster in alkaline media. Low-molecular carboxylic acids were identified as ultimate oxidation by-products formed in the reaction. PMID:23837343

  6. Interpretation of F-corona radial velocity observations

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.

    1987-03-01

    The observations made during the July 31, 1981 solar eclipse of the F-corona radial velocities between 3 and 7 solar radii are interpreted, assuming direct circular Keplerian motion of dust grains. Diffraction and isotropic scattering are considered. If the grains are assumed to be of silica, a best fit to observations is found for grain radii of about 0.4 micron, a border of dust-free zone from 6 to 14 solar radii, or a high concentration of grains at the same interval of heliocentric distances.

  7. Fluorine in R Coronae Borealis and Extreme Helium Stars

    E-print Network

    Gajendra Pandey; David L. Lambert; N. Kameswara Rao

    2007-12-24

    Neutral fluorine lines are identified in the optical spectra of several R Coronae Borealis stars (RCBs) at maximum light. These lines provide the first measurement of the fluorine abundance in these stars. Fluorine is enriched in some RCBs by factors of 800 to 8000 relative to its likely initial abundance. The overabundances of fluorine are evidence for the synthesis of fluorine. These results are discussed in the light of the scenario that RCBs are formed by accretion of an He white dwarf by a C-O white dwarf. Sakurai's object (V4334 Sgr), a final He-shell flash product, shows no detectable neutral fluorine lines.

  8. Heating of the solar corona by dissipative Alfvén solitons.

    PubMed

    Stasiewicz, K

    2006-05-01

    Solar photospheric convection drives myriads of dissipative Alfvén solitons (hereinafter called alfvenons) capable of accelerating electrons and ions to energies of hundreds of keV and producing the x-ray corona. Alfvenons are exact solutions of two-fluid equations for a collisionless plasma and represent natural accelerators for conversion of the electromagnetic energy flux driven by convective flows into kinetic energy of charged particles in space and astrophysical plasmas. Their properties have been experimentally verified in the magnetosphere, where they accelerate auroral electrons to tens of keV. PMID:16712308

  9. Heating of the Solar Corona by Dissipative Alfven Solitons

    E-print Network

    K. Stasiewicz

    2006-04-25

    Solar photospheric convection drives myriads of dissipative Alfven solitons (hereinafter called alfvenons) capable of accelerating electrons and ions to energies of hundreds of keV and producing the X-ray corona. Alfvenons are exact solutions of two-fluid equations for a collisionless plasma and represent natural accelerators for conversion of the electromagnetic energy flux driven by convective flows into kinetic energy of charged particles in space and astrophysical plasmas. Their properties have been experimentally verified in the magnetosphere, where they accelerate auroral electrons to tens of keV.

  10. Heating of the solar corona by the resonant absorption of Alfven waves

    NASA Technical Reports Server (NTRS)

    Davila, Joseph M.

    1986-01-01

    An improved method for calculating the resonance absorption heating rate is discussed and the results are compared with observations in the solar corona. The primary conclusion to be drawn from these calculations is that to the level of the approximation adopted, the observations of the heating rate and nonthermal line broadening in the solar corona are consistent with heating by the resonance absorption mechanism.

  11. Transient mantle convection on Venus: The paradoxical coexistence of highlands and coronae in the BAT region

    E-print Network

    Jellinek, Mark

    Transient mantle convection on Venus: The paradoxical coexistence of highlands and coronae on a timescale of thermal diffusion. Applied to Venus, our results support a hypothesis that the contemporaneous convection; Venus; coronae; highlands; mantle thermals and mantle plumes Earth and Planetary Science Letters

  12. Electrical Mobility Separation of Airborne Particles Using Integrated Microfabricated Corona Ionizer and Separator Electrodes

    Microsoft Academic Search

    Beelee Chua; Anthony S. Wexler; Norman C. Tien; Debbie A. Niemeier; Britt A. Holmen

    2009-01-01

    Airborne particles are separated according to their electrical mobilities using a microfabricated corona ionizer and separator electrodes. Oleic acid particles with sizes ranging from 30 to 300 nm are used to characterize the device. They are generated using a TSI 3075 constant output atomizer. These particles are electrically charged by a microfabricated corona ionizer, and the resultant particle electrical mobility

  13. Subduction on the margins of coronae on Venus: Evidence from radiothermal emissivity measurements

    NASA Technical Reports Server (NTRS)

    Robinson, C. A.

    1993-01-01

    Retrograde subduction has been suggested to occur at three coronae on Venus: Latona, Artemis, and Eithinoha. Using the mineralogical arguments of Klose to explain surface emissivity, a study of radio thermal emissivity of Venus coronae showed that emissivity changes associated with Latona, Artemis, and Ceres imply the same crustal movements predicted by the subduction model of Sandwell and Schubert.

  14. On the Intrinsic Difficulty of Producing Stellar Coronae With Acoustic Waves

    E-print Network

    Ulmschneider, Peter

    , however, severe empirical limits could be placed on the role that these waves play in heating the solar to heat the open corona, even though such waves are certainly abundant in the photosphere, Finally budget of a corona that is heated exclusively by acoustic waves of the given period. Solar coronal hole

  15. Multidimensional modeling of Trichel pulses in negative point-to-plane corona in air

    Microsoft Academic Search

    Yuri Akishev; Igor Kochetov; Alexander Loboiko; Anatoly Napartovich

    2002-01-01

    It is known that an electric current in a negative corona for pin-to-plane configuration in a wide range of parameters has a form of periodic pulses, which are called Trichel pulses. In this paper results of comprehensive numerical simulations of pulses evolution for a corona with axial symmetry are reported for a cathode in a form of a needle with

  16. Pulsed corona modelling of a wire-cylinder ESP under dust loading condition

    Microsoft Academic Search

    X. Liang; S. Jayaram; J. S. Chang; A. Berezein

    1999-01-01

    Modelling of the electrical conditions of an electrostatic precipitator (ESP) with dust loading under pulsed corona is difficult, and little progress has been made in this field. A method for the pulsed corona modelling of a wire-cylinder ESP based on the characteristics of Trichel pulses and the applied pulse voltage is developed and a novel way of dealing the particle

  17. Control of Trichel pulses of corona by geometric and gasdynamic factors

    Microsoft Academic Search

    Yu. S. Akishev; A. P. Napartovich; M. V. Pan'kin; N. I. Trushkin

    1997-01-01

    Summary form only given. Upon applying of step of high voltage that is over an inception one, the ignition of a negative corona is accompanied by a sharp splash of discharge current with a pulse duration of about 10-7. As a rule, for electropositive gases (N2 , Ar, etc.) the corona current falls after the splash and goes to the

  18. Negative corona discharge at a tip of water cone deformed under dc field

    Microsoft Academic Search

    Toshiyuki Sugimoto; Kazutoshi Asano; Yoshio Higashiyama

    2001-01-01

    The negative corona discharge phenomena occurring at a tip of water cone have been investigated focusing on the motion and the shape of the water surface using a high-speed video camera. The water cone is periodically formed from a water droplet located on a grounded electrode under dc field due to the electro-hydrodynamic instability. Negative corona discharge with trains of

  19. Recent Developments in Analysis of the Mechanisms of Positive and Negative Coronas in Air

    Microsoft Academic Search

    Leonard B. Loeb

    1948-01-01

    The nature of the detailed mechanism of the negative Trichel corona pulses in air at atmospheric pressures is reanalyzed on the basis of recent data of English giving the time duration of the pulse and details of its structure. The onset of corona from a negative point is shown to consist of pulses of about 4 ?sec. duration with a

  20. Chromophore Poling in Thin Films of Organic Glasses. 2. Two-Electrode Corona Discharge Setup

    NASA Astrophysics Data System (ADS)

    Vilitis, O.; Muzikante, I.; Rutkis, M.; Vembris, A.

    2012-01-01

    In Part 1 of the article we provided description of the corona discharge physics and overview of the methods used for corona poling in thin organic films. Subsequent sections describe comparatively simple technical methods for poling the organic nonlinear optical polymers using a two-electrode (point-to-plate or wire-to-plate) technique. The polarization build-up was studied by the DC positive corona method for poling the nonlinear optical (NLO) polymers. The experimental setup provides the corona discharge current from 0.5 ?A up to 3 ?A by applying 3 kV - 12 kV voltage to the corona electrode and makes possible selection among the types of corona electrodes (needle, multi-needle, wire, etc.). The results of experimental testing of the poling setup show that at fixed optimal operational parameters of poling - the sample orientation temperature and the discharge current - the corona charging of polymeric materials can successfully be performed applying the two-electrode technique. To study the dynamics of both poling and charge transport processes the three-electrode charging system - a corona triode - should be applied.

  1. CORONA DESTRUCTION: AN INNOVATIVE CONTROL TECHNOLOGY FOR VOCS AND AIR TOXICS

    EPA Science Inventory

    This paper discusses the work and results to date leading to the demonstration of the corona destruction process at pilot scale. The research effort in corona destruction of volatile organic compounds (VOCs) and air toxics has shown significant promise for providing a valuable co...

  2. Temperature determination and emission measure modeling of the coronae of ff Centauri and Procyon

    E-print Network

    Guedel, Manuel

    Temperature determination and emission measure modeling of the coronae of ff Centauri and Procyon A 4 , E. Behar 5 Abstract. We have obtained the spectra of the coronae of ff Centauri and Procyon measures EM have been obtained. For all three stars (Procyon, ff Cen (G2V), and ff Cen (K1V

  3. Impact Crater Densities on Volcanoes and Coronae on Venus: Implications for Volcanic Resurfacing

    Microsoft Academic Search

    Noriyuki Namiki; Sean C. Solomon

    1994-01-01

    The density of impact craters on large volcanoes on Venus is half the average crater density for the planet. The crater density on some classes of coronae is not significantly different from the global average density, but coronae with extensive associated volcanic deposits have lower crater densities. These results are inconsistent with both single-age and steady-state models for global resurfacing

  4. A comparison of the corona and interplanetary plasma during the solareclipse of July 31, 1981.

    NASA Astrophysics Data System (ADS)

    Vlasov, V. I.

    Similarity of the structural forms of the solar corona and interplanetary plasma was found by means of a comparison of a solar corona photograph and interplanetary plasma maps (radio images) obtained in the period including the solar eclipse of 31 July 1981 (29 July - 5 August 1981).

  5. Computation of Corona Space Charge, Electric Field, and VI Characteristic Using Equipotential Charge Shells

    Microsoft Academic Search

    Mark N. Horenstein

    1984-01-01

    A charge simulation technique incorporating discretized equipotential charge shells in the volume is used to approximate the electric field and space charge around a single conductor in corona and to compute the voltage-current relationship for the discharge. No iteration is required in the solution method. Results are compared to corona in coaxial geometry, for which analytical treatment is also possible,

  6. Self-consistent model of the quiet solar corona with a wave source of energy

    Microsoft Academic Search

    I. V. Chashej; V. I. Shishov

    1988-01-01

    A self-consistent, spherically symmetric model of the solar corona is considered with a heating source connected with linear damping of MHD waves propagating away from the strongly turbulized chromosphere. The regime of the corona is shown to be fully determined by one parameter: the induction B of the coronal magnetic field. If the magnetic field is sufficiently weak, B <

  7. Experimental study of a multipoint cathode corona in an argon flow

    NASA Astrophysics Data System (ADS)

    Baldanov, B. B.

    2009-07-01

    Results are presented from experimental studies of a multipoint negative corona in an atmospheric-pressure argon flow. It is shown that a decrease in the interpoint distance, gas circulation through the discharge gap, and the adjustment of ballast resistances in the corona supply circuit allow one to stabilize the discharge and enlarge the operating range of discharge currents.

  8. Magnetic fields and the temperature structure of the chromosphere-corona interface

    Microsoft Academic Search

    Roger A. Kopp; Max Kuperus

    1968-01-01

    The temperature structure of the transition region between the chromosphere and corona is discussed in the context of current ideas about magnetic fields in these layers. Magnetic channeling of the downward conductive heat flow from the corona into the regions of enhanced field at the supergranulation boundaries is proposed as a mechanism for explaining the measured intensities of solar ultraviolet

  9. Spectrum of single and multiple corona radiata infarcts: Clinical\\/MRI correlations

    Microsoft Academic Search

    Emre Kumral; Gamze Bayülkem

    2003-01-01

    We sought to determine the clinical pictures, topography and pathogenesis of patients with unilateral single or multiple corona radiata infarcts. We defined corona radiata ischemic stroke if the patient had a focal neurological deficit and a relevant non-hemorrhagic infarction confined to the vascular territory of a long medullary artery proved by CT and MRI with contrast. We compared risk factors

  10. NASA's Great Observatories May Unravel 400-Year Old Supernova Mystery

    NASA Astrophysics Data System (ADS)

    2004-10-01

    Four hundred years ago, sky watchers, including the famous astronomer Johannes Kepler, best known as the discoverer of the laws of planetary motion, were startled by the sudden appearance of a "new star" in the western sky, rivaling the brilliance of the nearby planets. Kepler's Supernova Remnant Multiple Images of Kepler's Supernova Remnant Modern astronomers, using NASA's three orbiting Great Observatories, are unraveling the mysteries of the expanding remains of Kepler's supernova, the last such object seen to explode in our Milky Way galaxy. When a new star appeared Oct. 9, 1604, observers could use only their eyes to study it. The telescope would not be invented for another four years. A team of modern astronomers has the combined abilities of NASA's Great Observatories, the Spitzer Space Telescope (SST), Hubble Space Telescope (HST), and Chandra X-ray Observatory, to analyze the remains in infrared radiation, visible light, and X-rays. Ravi Sankrit and William Blair of the Johns Hopkins University in Baltimore lead the team. The combined image unveils a bubble-shaped shroud of gas and dust, 14 light-years wide and expanding at 4 million mph. Observations from each telescope highlight distinct features of the supernova, a fast-moving shell of iron-rich material, surrounded by an expanding shock wave sweeping up interstellar gas and dust. Interview with Dr. Ravi Sankrit Interview with Dr. Ravi Sankrit "Multi-wavelength studies are absolutely essential for putting together a complete picture of how supernova remnants evolve," Sankrit said. Sankrit is an associate research scientist, Center for Astrophysical Sciences at Hopkins and lead for HST astronomer observations. "For instance, the infrared data are dominated by heated interstellar dust, while optical and X-ray observations sample different temperatures of gas," Blair added. Blair is a research professor, Physics and Astronomy Department at Hopkins and lead astronomer for SST observations. "A range of observations is needed to help us understand the complex relationship that exists among the various components," Blair said. The explosion of a star is a catastrophic event. The blast rips the star apart and unleashes a roughly spherical shock wave that expands outward at more than 22 million mph like an interstellar tsunami. The shock wave spreads out into surrounding space, sweeping up any tenuous interstellar gas and dust into an expanding shell. The stellar ejecta from the explosion initially trail behind the shock wave. It eventually catches up with the inner edge of the shell and is heated to X-ray temperatures. Kepler's Supernova Remnant Hubble Optical Image of Kepler's Supernova Remnant Visible-light images from Hubble's Advanced Camera for Surveys reveal where the supernova shock wave is slamming into the densest regions of surrounding gas. The bright glowing knots are dense clumps that form behind the shock wave. Sankrit and Blair compared their HST observations with those taken with ground-based telescopes to obtain a more accurate distance to the supernova remnant of about 13,000 light-years. Kepler's Supernova Remnant Spitzer Infrared Image of Kepler's Supernova Remnant The astronomers used the SST to probe for material that radiates in infrared light, which shows heated microscopic dust particles that have been swept up by the supernova shock wave. SST is sensitive enough to detect both the densest regions seen by HST and the entire expanding shock wave, a spherical cloud of material. Instruments on SST also reveal information about the chemical composition and physical environment of the expanding clouds of gas and dust ejected into space. This dust is similar to dust which was part of the cloud of dust and gas that formed the sun and planets in our solar system. Interview with Dr. William Blair Interview with Dr. William Blair The Chandra X-ray data show regions of very hot gas. The hottest gas, higher-energy X-rays, is located primarily in the regions directly behind the shock front. These regions also show up

  11. Development of a positive corona from a long grounded wire in a growing thunderstorm field

    NASA Astrophysics Data System (ADS)

    Mokrov, M. S.; Raizer, Yu P.; Bazelyan, E. M.

    2013-11-01

    The properties of a non-stationary corona initiated from a long grounded wire suspended horizontally above the ground and coronating in a slowly varying thundercloud electric field are studied. A two-dimensional (2D) model of the corona is developed. On the basis of this model, characteristics of the corona produced by a lightning protection wire are calculated under thunderstorm conditions. The corona characteristics are also found by using approximate analytical and quasi-one-dimensional numerical models. The results of these models agree reasonably well with those obtained from the 2D simulation. This allows one to estimate the corona parameters without recourse to the cumbersome simulation. This work was performed with a view to study the efficiency of lightning protection wires later on.

  12. Solar wind Acceleration from the Upper Chromosphere to the Corona in Coronal Hole Regions

    NASA Technical Reports Server (NTRS)

    Esser, Ruth

    1998-01-01

    The dynamic behavior of the plasma in the chromosphere/transition region /inner corona is vital for the acceleration of the solar wind. With new theoretical descriptions of the solar atmosphere and corona, and the increased observational possibilities provided by the SOHO spacecraft, it is possible to conduct an integrated study of the solar atmosphere and corona using observational and theoretical approaches. Over the past few years a series of observational techniques have been used to estimate the solar wind densities, temperatures and flow speed in the inner corona. These estimates suggest that the solar wind has higher outflow speeds in the inner corona and lower densities than previously assumed. A comparison with densities derived from atmospheric models support these lower densities.

  13. Measurement of positive direct current corona pulse in coaxial wire-cylinder gap

    SciTech Connect

    Yin, Han, E-mail: hanyin1986@gmail.com; Zhang, Bo, E-mail: shizbcn@mail.tsinghua.edu.cn; He, Jinliang, E-mail: hejl@tsinghua.edu.cn; Wang, Wenzhuo, E-mail: wwzhuo1990@gmail.com [Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China)] [Department of Electrical Engineering, Tsinghua University, Beijing 100084 (China)

    2014-03-15

    In this paper, a system is designed and developed to measure the positive corona current in coaxial wire-cylinder gaps. The characteristic parameters of corona current pulses, such as the amplitude, rise time, half-wave time, and repetition frequency, are statistically analyzed and a new set of empirical formulas are derived by numerical fitting. The influence of space charges on corona currents is tested by using three corona cages with different radii. A numerical method is used to solve a simplified ion-flow model to explain the influence of space charges. Based on the statistical results, a stochastic model is developed to simulate the corona pulse trains. And this model is verified by comparing the simulated frequency-domain responses with the measured ones.

  14. RXTE Observation of Cygnus X-1: III. Implications for Compton Corona and ADAF Models. Report 3; Implications for Compton Corona and ADAF Models

    NASA Technical Reports Server (NTRS)

    Nowak, Michael A.; Wilms, Joern; Vaughan, Brian A.; Dove, James B.; Begelman, Mitchell C.

    1999-01-01

    We have recently shown that a 'sphere + disk' geometry Compton corona model provides a good description of Rossi X-ray Timing Explorer (RXTE) observations of the hard/low state of Cygnus X-1. Separately, we have analyzed the temporal data provided by RXTE. In this paper we consider the implications of this timing analysis for our best-fit 'sphere + disk' Comptonization models. We focus our attention on the observed Fourier frequency-dependent time delays between hard and soft photons. We consider whether the observed time delays are: created in the disk but are merely reprocessed by the corona; created by differences between the hard and soft photon diffusion times in coronae with extremely large radii; or are due to 'propagation' of disturbances through the corona. We find that the time delays are most likely created directly within the corona; however, it is currently uncertain which specific model is the most likely explanation. Models that posit a large coronal radius [or equivalently, a large Advection Dominated Accretion Flow (ADAF) region] do not fully address all the details of the observed spectrum. The Compton corona models that do address the full spectrum do not contain dynamical information. We show, however, that simple phenomenological propagation models for the observed time delays for these latter models imply extremely slow characteristic propagation speeds within the coronal region.

  15. Diffusion coronas around quartz xenocrysts in andesite and basalt from Tertiary volcanic region in northeastern Shikoku, Japan

    Microsoft Academic Search

    Hiroaki Sato

    1975-01-01

    Coronas around quartz xenocrysts in andesite and basalt from Tertiary volcanics in northeastern Shikoku, Japan, have been described. The coronas are composed mainly of Ca-rich clinopyroxene and glass. Compositional profiles across the corona glass show monotonous variation of major elements except for alkalis. Preliminary experiment on the reaction between basaltic melt and quartz has shown that alkalis diffused against their

  16. Coupling from the photosphere to the chromosphere and the corona

    E-print Network

    S. Wedemeyer-Böhm; A. Lagg; Å. Nordlund

    2008-09-15

    The atmosphere of the Sun is characterized by a complex interplay of competing physical processes: convection, radiation, conduction, and magnetic fields. The most obvious imprint of the solar convection and its overshooting in the low atmosphere is the granulation pattern. Beside this dominating scale there is a more or less smooth distribution of spatial scales, both towards smaller and larger scales, making the Sun essentially a multi-scale object. Convection and overshooting give the photosphere its face but also act as drivers for the layers above, namely the chromosphere and corona. The magnetic field configuration effectively couples the atmospheric layers on a multitude of spatial scales, for instance in the form of loops that are anchored in the convection zone and continue through the atmosphere up into the chromosphere and corona. The magnetic field is also an important structuring agent for the small, granulation-size scales, although (hydrodynamic) shock waves also play an important role -- especially in the internetwork atmosphere where mostly weak fields prevail. Based on recent results from observations and numerical simulations, we attempt to present a comprehensive picture of the atmosphere of the quiet Sun as a highly intermittent and dynamic system.

  17. Decontamination of 2-Chloroethyl Ethyl Sulfide by Pulsed Corona Plasma

    NASA Astrophysics Data System (ADS)

    Li, Zhanguo; Hu, Zhen; Cao, Peng; Zhao, Hongjie

    2014-11-01

    Decontamination of 2-chloroethyl ethyl sulfide (2-CEES, CH3CH2SCH2CH2Cl) by pulsed corona plasma was investigated. The results show that 212.6 mg/m3 of 2-CEES, with the gas flow rate of 2 m3/h, can be decontaminated to 0.09 mg/m3. According to the variation of the inlet and outlet concentration of 2-CEES vapor with retention time, it is found that the reaction of 2-CEES in a pulsed corona plasma system follows the first order reaction, with the reaction rate constant of 0.463 s?1. The decontamination mechanism is discussed based on an analysis of the dissociation energy of chemical bonds and decontamination products. The C–S bond adjacent to the Cl atom will be destroyed firstly to form CH3CH2S· and ·CH2CH2Cl radicals. CH3CH2S· can be decomposed to ·C2H5 and ·S. ·S can be oxidized to SO2, while ·C2H5 can be finally oxidized to CO2 and H2O. The C–Cl bond in the ·CH2CH2Cl radical can be destroyed to form ·CH2CH2. and ·Cl, which can be mineralized to CO2, H2O and HCl. The H atom in the ·CH2CH2Cl radical can also be substituted by ·Cl to form CHCl2–CHCl2.

  18. A Corona Discharge Initiated Electrochemical Electrospray Ionization Technique

    PubMed Central

    Lloyd, John R.; Hess, Sonja

    2009-01-01

    We report here the development of a corona discharge (CD) initiated electrochemical (EC) electrospray ionization (ESI) technique using a standard electrospray ion source. This is a new ionization technique distinct from ESI, electrochemistry inherent to ESI, APCI, and techniques using hydroxyl radicals produced under atmospheric pressure conditions. By maximizing the observable CD at the tip of a stainless steel ESI capillary, efficient electrochemical oxidation of electrochemically active compounds is observed. For electrochemical oxidation to be observed, the ionization potential of the analyte must be lower than Fe. Ferrocene labeled compounds were chosen as the electrochemically active moiety. The electrochemical cell in the ESI source was robust and generated ions with selectivity according to the ionization potential of the analytes and up to zeptomolar sensitivity. Our results indicate that CD initiated electrochemical ionization has the potential to become a powerful technique to increase the dynamic range, sensitivity and selectivity of ESI experiments. Synopsis Using a standard ESI source a corona discharge initiated electrochemical ionization technique was established resulting from the electrochemistry occurring at the CD electrode surface. PMID:19747843

  19. Magnetic tornadoes as energy channels into the solar corona

    NASA Astrophysics Data System (ADS)

    Wedemeyer-Böhm, Sven; Scullion, Eamon; Steiner, Oskar; Rouppe van der Voort, Luc; de La Cruz Rodriguez, Jaime; Fedun, Viktor; Erdélyi, Robert

    2012-06-01

    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.

  20. Accretion disk corona line emission from X0614+091

    NASA Technical Reports Server (NTRS)

    Christian, D. J.; White, N. E.; Swank, J. H.

    1994-01-01

    The low-mass X-ray binary X0614+091 was observed on 3 days in 1979 with the Einstein Observatory solid state spectrometer and the monitor proportional counter. During the observation with the highest measured flux, corresponding to an X-ray luminosity of 8 x 10(exp 36) erg/s (in the 0.5-20 keV band for an assumed distance of 5 kpc), significant low-energy emission was detected, centered at 0.77 keV, possibly due to line emission for O VII-O VIII and Fe XVII-Fe XIX. The other observations, which were at fluxes lower by a factor of 2, are consistent with the presence of the emission feature. The equivalent width of the feature, 37 +/- 6 eV, is of the same order as equivalent widths previously reported for more luminous low-mass X-ray binaries using grating spectrometer data. The soft X-ray lines could be emitted by gas expected to arise in an accretion disk corona excited by the central source. But to explain the observed feature, most of the corona needs to contribute, or other sources of emission are required.

  1. Accretion disk coronae in high-luminosity systems

    NASA Technical Reports Server (NTRS)

    Murray, Stephen D.; Castor, John I.; Klein, Richard I.; Mckee, Christopher F.

    1994-01-01

    We present the results of self-consistent models of Compton-heated accretion disk coronae. The models are calculated using a new method for computing monochromatic radiative transfer n two dimensions. The method splits the radiation into direct and scattered components. The direct radiation is computed by calculating the optical depth along rays, while transfer of the scattered radiation is approximated by flux-limited diffusion. The resulting code agrees with more accurate treatments to within 50%, and is highly efficient, making it practical for use in large hydrodynamic simulations. The coronal models are used to confirm the results of earlier work, and to extend it to higher luminosities. In contrast to earlier work, which found the outer disks to be shadowed by the inner corona at high luminosities, we find our results to form an almost continuous extension of the models at lower luminosities. This is due to the presence of multiply scattered radiation, which acts to partially offset the loss of direct radiation from the central source. Although the analytic methods derived at lower luminosities cannot be used to derive the coronal structure for L/L(sub Edd) approx. greater than 0.1, the results of the models are amenable to semiempirical fits. We also discuss possible observational consequences of the results for coronal veiling and line fluorescence from the disk.

  2. The EUV Emission in Comet-Solar Corona Interactions

    NASA Technical Reports Server (NTRS)

    Bryans, Paul; Pesnell, William Dean; Schrijver, Carolus J.; Brown, John C.; Battams, Karl; Saint-Hilaire, Pasal; Liu, Wei; Hudson, Hugh S.

    2011-01-01

    The Atmospheric Imaging Assembly (AlA) on the Solar Dynamics Observatory (SDO) viewed a comet as it passed through the solar corona on 2011 July 5. This was the first sighting of a comet by a EUV telescope. For 20 minutes, enhanced emission in several of the AlA wavelength bands marked the path of the comet. We explain this EUV emission by considering the evolution of the cometary atmosphere as it interacts with the ambient solar atmosphere. Water ice in the comet rapidly sublimates as it approaches the Sun. This water vapor is then photodissociated, primarily by Ly-alpha, by the solar radiation field to create atomic Hand O. Other molecules present in the comet also evaporate and dissociate to give atomic Fe and other metals. Subsequent ionization of these atoms can be achieved by a number of means, including photoionization, electron impact, and charge exchange with coronal protons and other highly-charged species. Finally, particles from the cometary atmosphere are thermalized to the background temperature of the corona. Each step could cause emission in the AlA bandpasses. We will report here on their relative contribution to the emission seen in the AlA telescopes.

  3. Spatial and temporal relations between coronae and extensional belts, northern Lada Terra, Venus

    NASA Astrophysics Data System (ADS)

    Baer, G.; Schubert, G.; Bindschadler, D. L.; Stofan, E. R.

    1994-04-01

    Preliminary studies of the distribution of coronae and volcanic rises on Venus show that many of these features tend to cluster along zones of rifting and extension. The plains north of Lada Terra are crossed by two such extensional belts. Each belt is composed of grabens, ridges, faults, volcanic flows, coronae and coronalike features. The longer and more prominent belt is the NW trending Alpha-Lada extensional belt, which is over 6000 km long and 50-200 km wide, and includes the coronae Eve, Tamfana, Carpo, Selu, Derceto, Otygen, and an unnamed corona south of Otygen. The second belt is the NNE trending Derceto-Quetzalpetlatl extensional belt, which is about 2000 km long and in places over 300 km wide, and includes the coronae Sarpanitum, Eithinoha, and Quetzalpetlatl. The two belts intersect at the 1600 x 600 km wide Derceto volcanic plateau. It is apparent that deformation along the two belts overlapped in time, though deformation along the Alpha-Lada extensional belt probably continued after the deformation along the Derceto-Quetzalpetlatl extensional belt terminated. In certain areas, volcanism originated in grabens within the extensional belts, whereas in other areas, such as in Eve, Selu, Derceto, and Quetzalpetlatl, volcanism originated in the coronae and flowed into the lower parts of the extensional belts. Regional extension has affected the evolution of all the coronae at some stage of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha of their development. Regional deformation occurred before the initiation of Derceto and Eithinoha and after the initiation of Carpo, Tamfana, Otygen, and Sarpanitum. It is thus unlikely that coronae formation along the belts is solely a consequence of the regional extension, and it is also unlikely that regional extension has been caused solely by the coronae. No corona along the belts was formed subsequent to the cessation of the regional extension. We therefore suggest that the regional extension and the coronae are interrelated. Some of the coronae may have determined the location of the surface expression of the regional extension, whereas the locations of other coronae may have been influenced by the concentration of regional extensional stresses.

  4. 1997 and 2006 Solar Minimum Comparisons of Geocoronal Hydrogen Data

    Microsoft Academic Search

    S. M. Nossal; E. J. Mierkiewicz; F. L. Roesler; L. M. Haffner; R. J. Reynolds

    2007-01-01

    Ground-based Fabry-Perot observations of the hydrogen Balmer-alpha emission have been used since the late 1970s to investigate hydrogen in the geocorona, spanning the upper thermosphere and exosphere. Atomic hydrogen in this region is a byproduct of hydrogen-containing species below such as methane and water vapor. Models have predicted 50-75 % increases in upper atmospheric hydrogen as a consequence of a

  5. Bipolar climatology of GPS ionospheric scintillation at solar minimum

    NASA Astrophysics Data System (ADS)

    Alfonsi, Lucilla; Spogli, Luca; De Franceschi, Giorgiana; Romano, Vincenzo; Aquino, Marcio; Dodson, Alan; Mitchell, Cathryn N.

    2011-06-01

    High-rate sampling data of Global Navigation Satellite Systems ionospheric scintillation acquired by a network of GPS Ionospheric Scintillation and TEC Monitor receivers located in the Svalbard Islands, in Norway and in Antarctica have been analyzed. The aim is to describe the “scintillation climatology” of the high-latitude ionosphere over both the poles under quiet conditions of the near-Earth environment. For climatology we mean to assess the general recurrent features of the ionospheric irregularities dynamics and temporal evolution on long data series, trying to catch eventual correspondences with scintillation occurrence. In spite of the fact that the sites are not geomagnetically conjugate, long series of data recorded by the same kind of receivers provide a rare opportunity to draw a picture of the ionospheric features characterizing the scintillation conditions over high latitudes. The method adopted is the Ground Based Scintillation Climatology, which produces maps of scintillation occurrence and of total electron content relative variation to investigate ionospheric scintillations scenario in terms of geomagnetic and geographic coordinates, interplanetary magnetic field conditions and seasonal variability. By means of such a novel and original description of the ionospheric irregularities, our work provides insights to speculate on the cause-effect mechanisms producing scintillations, suggesting the roles of the high-latitude ionospheric trough, of the auroral boundaries and of the polar cap ionosphere in hosting those irregularities causing scintillations over both the hemispheres at high latitude. The method can constitute a first step toward the development of new algorithms to forecast the scintillations during space weather events.

  6. Measurements and IRI Model Predictions During the Recent Solar Minimum

    NASA Technical Reports Server (NTRS)

    Bilitza, Dieter; Brown, Steven A.; Wang, Mathew Y.; Souza, Jonas R.; Roddy, Patrick A.

    2012-01-01

    Cycle 23 was exceptional in that it lasted almost two years longer than its predecessors and in that it ended in an extended minimum period that proved all predictions wrong. Comparisons of the International Reference Ionosphere (IRI) with CHAMP and GRACE in-situ measurements of electron density during the minimum have revealed significant discrepancies at 400-500 km altitude. Our study investigates the causes for these discrepancies with the help of ionosonde and Planar Langmuir Probe (PLP) data from the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. Our C/NOFS comparisons confirm the earlier CHAMP and GRACE results. But the ionosonde measurements of the F-peak plasma frequency (foF2) show generally good agreement throughout the whole solar cycle. At mid-latitude stations yearly averages of the data-model difference are within 10% and at low latitudes stations within 20%. The 60-70% differences found at 400-500 km altitude are not seen at the F peak. We will discuss how these seemingly contradicting results from the ionosonde and in situ data-model comparisons can be explained and which parameters need to be corrected in the IRI model.

  7. Radiation environment on the MIR orbital station during solar minimum

    NASA Astrophysics Data System (ADS)

    Badhwar, G. D.; Atwell, W.; Cash, B.; Petrov, V. M.; Akatov, Yu. A.; Tchernykh, I. V.; Shurshakov, V. A.; Arkhangelsky, V. A.

    The Mir station has been in a 51.65 deg inclination orbit since March 1986. In March 1995, the first US astronaut flew on the Mir-18 mission and returned on the Space Shuttle in July 1995. Since then three additional US astronauts have stayed on orbit for up to 6 months. Since the return of the first US astronaut, both the Spektr and Priroda modules have docked with Mir station, altering the mass shielding distribution. Radiation measurements, including the direct comparison of US and Russian absorbed dose rates in the Base Block of the Mir station, were made during the Mir-18 and -19 missions. There is a significant variation of dose rates across the core module; the six locations sampled showed a variation of a factor of nearly two. A tissue equivalent proportional counter (TEPC) measured a total absorbed dose rate of 300 mu Gy/day, roughly equally divided between the rate due to trapped protons from the South Atlantic Anomaly (SAA) and galactic cosmic radiation (GCR). This dose rate is about a factor of two lower than the rate measured by the thinly shielded (0.5 g cm^-2 of Al) operational ion chamber (R-16), and about 3/2 of the rate of the more heavily shielded (3.5 g cm^-2 of Al) ion chamber. This is due to the differences in the mass shielding properties at the location of these detectors. A comparison of integral linear energy transfer (LET) spectra measured by TEPC and plastic nuclear track detectors (PNTDs) deployed side by side are in remarkable agreement in the LET region of 15 -1000 keV/mum, where the PNTDs are fully efficient. The average quality factor, using the ICRP-26 definition, was 2.6, which is higher than normally used. There is excellent agreement between the measured GCR dose rate and model calculations, but this is not true for trapped protons. The measured Mir-18 crew skin dose equivalent rate was 1133 muSv/day. Using the skin dose rate and anatomical models, we have estimated the blood-forming organ (BFO) dose rate and the maximum stay time in orbit for International Space Station crew members.

  8. Measurements and IRI model predictions during the recent solar minimum

    NASA Astrophysics Data System (ADS)

    Bilitza, Dieter; Brown, Steven A.; Wang, Mathew Y.; Souza, Jonas R.; Roddy, Patrick A.

    2012-09-01

    Cycle 23 was exceptional in that it lasted almost two years longer than its predecessors and in that it ended in an extended minimum period that proved all predictions wrong. Comparisons of the International Reference Ionosphere (IRI) with CHAMP and GRACE in-situ measurements of electron density during the minimum have revealed significant discrepancies at 400-500 km altitude (Lühr and Xiong, 2010). Our study investigates the causes for these discrepancies with the help of ionosonde and Planar Langmuir Probe (PLP) data from the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. Our C/NOFS comparisons confirm the earlier CHAMP and GRACE results. But the ionosonde measurements of the F-peak plasma frequency (foF2) show generally good agreement throughout the whole solar cycle. At mid-latitude stations yearly averages of the data-model difference are within 10% and at low latitudes stations within 20%. The 60-70% differences found at 400-500 km altitude are not seen at the F peak. We will discuss how these seemingly contradicting results from the ionosonde and insitu data-model comparisons can be explained and which parameters need to be corrected in the IRI model.

  9. Unraveling the commercial market for medicinal plants and plant parts on the witwatersrand, South Africa

    Microsoft Academic Search

    Vivienne L. Williams; Kevin Balkwill; Edward T. F. Witkowski

    2000-01-01

    To unravel the market for commercial medicinal plants on the Witwatersrand in South Africa, a semiquantitative approach was\\u000a taken. A stratified random sample of 50 herb-traders was surveyed, and an inventory of all plants and parts sold was compiled.\\u000a Research participants were questioned on the scarcity and popularity of the plants traded, as well as suppliers and origins.\\u000a The rarefaction

  10. Geology of coronae and domal structures on Venus and models of their origin

    SciTech Connect

    Stofan, E.R.

    1989-01-01

    Coronae (160 to 670 km across) and domal structures (greater than 1000 km across) are complex topographic highs on Venus that were affected by volcanic and topographic processes. The geology of coronae and a major domal structure, Beta Regio, are documented using Pioneer Venus, Arecibo, and Venera 15/16 data. The evolution and possible models of origin of these features are also investigated. Beta Regio is a 2000 x 2300 km topographic high located in the equatorial region of Venus that rises over 5 km above the surrounding region. Within Beta Regio lie two large volcanic shields, Theia and Rhea Mons. Coronae are circular to elongate structures on Venus, characterized by an annulus of concentric compressional ridges and relatively raised topography surrounded by a peripheral trough. Volcanic domes, flows and edifices, as well as tectonic lineaments characterize the interiors of coronae. Thirty one coronae were detected on Venus. Two analytical models were developed that are consistent with the general characteristics and evolution of coronae: hotspot or rising mantle diapir model and sinking mantle diapir model. Coronae appear to be part of a continuum of thermally produced features on Venus, along with volcanic complexes and domal structures such as Beta Regio.

  11. The Role of Magnetic Reconnection in Self-Organization of the Corona: Theory and Observations

    NASA Astrophysics Data System (ADS)

    Cassak, P. A.; Mullan, D. J.; Shay, M. A.

    2008-12-01

    Based on observations that solar flares obey power law statistics, it was suggested that the solar corona is in a state of self-organized criticality [1]. However, the physical mechanism underlying the dynamics is not well understood. A recent model [2] describing the catastrophic onset of fast (Hall) magnetic reconnection in weakly collisional plasmas may potentially contribute to this discussion. We suggest that the condition at which the catastrophic onset of reconnection occurs sets the critical state of the corona and the physics of reconnection organizes the corona into this critical state [3]. (See also [4].) The model makes a quantitative prediction for the conditions of the corona at the onset of eruptions, which is known to be consistent with observations of the solar corona. We present new observational evidence from stellar flares (107 events in 37 sun-like stars) that stellar coronae are near the same critical state at flare onset. This provides observational evidence in support of the model and suggests that magnetic reconnection plays an active role in constraining the conditions in solar and stellar coronae. Implications for self-organization in coronal heating and solar eruptions will be discussed. [1] E. T. Lu and R. J. Hamilton, Ap. J., 380, L89, 1991; [2] P. A. Cassak et al., Phys. Rev. Lett., 95, 235002, 2005; P. A. Cassak et al., Ap. J. Lett., 644, L145, 2006; [3] P. A. Cassak et al., Ap. J. Lett., 676, L69, 2008; [4] D. A. Uzdensky, Ap. J., 671, 2139, 2007.

  12. Ex situ evaluation of the composition of protein corona of intravenously injected superparamagnetic nanoparticles in rats.

    PubMed

    Sakulkhu, Usawadee; Maurizi, Lionel; Mahmoudi, Morteza; Motazacker, Mahdi; Vries, Marcel; Gramoun, Azza; Ollivier Beuzelin, Marie-Gabrielle; Vallée, Jean-Paul; Rezaee, Farhad; Hofmann, Heinrich

    2014-10-01

    It is now well recognized that the surfaces of nanoparticles (NPs) are coated with biomolecules (e.g., proteins) in a biological medium. Although extensive reports have been published on the protein corona at the surface of NPs in vitro, there are very few on the in vivo protein corona. The main reason for having very poor information regarding the protein corona in vivo is that separation of NPs from the in vivo environment has not been possible by using available techniques. Knowledge of the in vivo protein corona could lead to better understanding and prediction of the fate of NPs in vivo. Here, by using the unique magnetic properties of superparamagnetic iron oxide NPs (SPIONs), NPs were extracted from rat sera after in vivo interaction with the rat's physiological system. More specifically, the in vivo protein coronas of polyvinyl-alcohol-coated SPIONs with various surface charges are defined. The compositions of the corona at the surface of various SPIONs and their effects on the biodistribution of SPIONs were examined and compared with the corona composition of particles incubated for the same time in rat serum. PMID:25154771

  13. Characterization of Atmospheric Pressure DC Negative Corona Discharges for Thin Film Deposition

    NASA Astrophysics Data System (ADS)

    Antao, Dion; Fridman, Alexander; Farouk, Bakhtier

    2009-10-01

    The applicability of DC corona discharges with their lower temperatures and uniformity is investigated for the deposition of thin films. The deposition is done at atmospheric pressure and room temperature, which lowers the facility cost as no vacuum or low pressure facilities are required and also enables continuous processing rather than batch processing. We report on our studies the operating regimes and the structures of DC negative corona discharges for a point to plate electrode configuration for thin film deposition. Traditionally DC coronas have been operated at extremely low currents. By modifying the circuit, we have been able to operate the DC corona at higher currents without breakdown. We operated the DC negative corona discharge in new regimes where a stable and diffuse glow has been observed near the anode surface. This diffuse glow is observed in air and methane containing discharges. The discharge is characterized by voltage-current diagnostics. Optical emission spectroscopy (OES) is used to obtain spatially resolved temperature measurements. The DC negative corona discharge has been observed to deposit films on the anode surface. The deposition of films and particles on the anode surface has introduced the possibility of using corona discharges as a novel method of materials deposition or surface modification at atmospheric pressure.

  14. MESSENGER soft X-ray observations of the quiet solar corona

    NASA Astrophysics Data System (ADS)

    Schwartz, Richard A.; Hudson, Hugh S.; Tolbert, Anne K; Dennis, Brian R.

    2014-06-01

    In a remarkable result from their "SphinX" experiment, Sylwester et al. (2012) found a non-varying base level of soft X-ray emission at the quietest times in 2009. We describe comparable data from the soft X-ray monitor on board MESSENGER (en route to Mercury) which had excellent coverage both in 2009 and during the true solar minimum of 2008. These observations overlap SphinX's and also are often exactly at Sun-MESSENGER-Earth conjunctions. During solar minimum the Sun-MESSENGER distance varied substantially, allowing us to use the inverse-square law to help distinguish the aperture flux (ie, solar X-rays) from that due to sources of background in the 2-5 keV range. The MESSENGER data show a non-varying background level for many months in 2008 when no active regions were present. We compare these data in detail with those from SphinX. Both sets of data reveal a different behavior when magnetic active regions are present on the Sun, and when they are not.Reference: Sylwester et al., ApJ 751, 111 (2012)

  15. Control of soot emission of a turbulent diffusion flame by DC or AC corona discharges

    SciTech Connect

    Ohisa, Hiromichi; Kimura, Itsuro; Horisawa, Hideyuki [Tokai Univ., Hiratsuka, Kanagawa (Japan)] [Tokai Univ., Hiratsuka, Kanagawa (Japan)

    1999-03-01

    The effects of DC or AC (14 kHz) corona discharges, formed between tips of opposed needle electrodes, on soot emission of a propane turbulent diffusion flame were investigated experimentally. It is shown that when a DC corona discharge (e.g., 3.6 W; 0.06% of the combustion energy released by the flame) or a discharge system composed of three AC coronas (e.g., 25.5 W in total; 0.43% of the combustion energy) is applied across the lower part of the flame, with a gap width such that the electrode tips are located outside the reaction zone, a marked reduction in soot emission is observed, without noticeable change in the shape of flame luminous region. When corona discharges are applied, increases of the density of charged species and/or charged soot particles are observed in the flame over the whole length downstream of the corona application. It is suggested that, in the case of DC corona application, additional air and inorganic charged species and electrons, produced in the air near the tip of the positive electrode, are carried into the flame mainly by corona winds, whereas in the case of the AC corona application the inorganic charges species and electrons are carried into the flame by diffusion processes. The charged species and electrons carried into the flame may influence the state of charging of incipient soot particles and also reduce the concentration of growing ions, i.e., soot precursors, which directly relate to the soot emission of the flame. In TEM photographs it was found that separate soot particles, or those forming chains in the flame, decrease in mean size with the application of corona discharges. Smaller size soot particles burn faster than larger size particles in the high-temperature oxidizing atmosphere at the flame top region.

  16. The eclipse corona: reality and possible research during the 1999 eclipse

    NASA Astrophysics Data System (ADS)

    Rusin, V.; Rybansky, M.

    1999-03-01

    Solar eclipses provide a unique opportunity to observe the solar corona and to solve many open questions in solar coronal physics, e.g., heating of the corona, small-scale structures, dust particles, formation and distribution of coronal structures around the solar surface with respect to the photospheric activity centers, polarization, dust vaporization near the Sun, formation and spatial orientation of solar wind streamers, etc. The forthcoming 1999 eclipse will pass across many countries in Europe, the Middle East and Asia. This event will provide a good opportunity to perform observations of the corona with 'bigger' equipment to obtain high-resolution. We propose to focus scientific experiments on the following targets: THE WHITE-LIGHT AND EMISSION CORONA: exact photometry of the corona with telescopes of focal length 1-3 m; in detail, photometry around the poles and/or above active regions with a minimum focal length of 5 m; photoelectric detection of oscillations; co-ordinated observations with `smaller' telescopes, of 1 m focal length, along the umbral path (dynamics and large-scale structure), polarization in emission corona, etc. SPECTRAL OBSERVATIONS: detection of short-term oscillations (less than 0.1 s) in individual spectral emission coronal lines or in the white-light corona; polarization in emission coronal lines (the Hanle effect - direction of coronal magnetic field lines); spectral observations with small-scale resolution: colour of the solar corona, large-scale resolution: profiles of emission lines; depth of absorption lines (F-corona), etc. Moreover, high-precision timing of eclipse contacts can help us to obtain more accurate parameters of the Moon's orbit around the Earth and to measure the diameter of the Sun. Comets, if any, should be studied in the close vicinity of the Sun. We are of the opinion that the most important problems in solar coronal research during the 1999 eclipse will be supported by coordinated ground-based and satellite observations.

  17. Corona Mass Ejections: a Summary of Recent Results

    NASA Astrophysics Data System (ADS)

    Gopalswamy, N.

    2010-12-01

    Corona mass ejections (CMEs) have been Recognized as the most energetic phenomenon in the heliosphere, deriving their energy from the stressed magnetic fields on the Sun. This paper highlights some of the recent results obtained on CMEs from the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory (STEREO) missions. The summary of follows the talk. SOHO observations revealed that the CME rate is almost a factor of: Two larger than previously thought and varied with the solar activity cycle in a complex way (eg, high-latitude CMEs occurred in great abundance during the solar years maximum). CMEs were found to interact with other CMEs as well as with other large-scale structures (corona holes), Resulting in deflections and additional particle acceleration. STEREO observations have confirmed the three-dimensional nature of CMEs and shocks the surrounding them. The EUV signatures (flare arcades, Corona dimming, filament Eruption, and EUV waves) associated with CMEs have become vital in the identification of sources from Which solar CMEs erupt. CMEs with speeds exceeding the characteristic speeds of the corona and the interplanetary medium drive shocks, which produce type II radio bursts. The wavelength range of type II bursts depends on the CME kinetic energy: type II bursts with emission components at all wavelengths (metric to kilometric) due to CMEs are of the highest kinetic energy. Some CMEs, as fast as 1600 km / s do not produce type II bursts, while slow CMEs (400 km / s) occasionally produce type II bursts. These observations can be explained as the variation in the ambient flow speed (solar wind) speed and the Alfvén. Not all CME-driven shocks produce type II bursts because they are either subcritical Or do not have the appropriate geometry. The same shocks that produce type II bursts also produce solar energetic particles (SEPS), Whose release near the Sun seems to be delayed with respect to the onset of type II bursts. This may indicate a subtle difference in the acceleration of the ions and ~ 10 keV electrons needed to produce type II bursts. Surprisingly, some shocks lacking type II bursts are associated with energetic storm particle events (ESPs), pointing to the importance of electron escape from the shock for producing the radio emission. CMEs slow down or accelerate in the interplanetary medium because of the drag force, which modifies the transit time of CMEs and shocks. Halo CMEs that appear to surround the occulting disk were known before the SOHO era, and occasional events. During the SOHO era, they became very prominent because of their ability to impact Earth and producing geomagnetic storms. Halo CMEs are generally more energetic than ordinary CMEs, which means they can produce north of the impact on Earth's magnetosphere. Their origin close to the center disk of the Sun ensures direct impact on the magnetosphere, although their internal magnetic structure is crucial in causing storms. The solar sources of CMEs that produce SEP events at Earth, on the other hand, are generally in the western hemisphere because of the magnetic connectivity. Thus, CMEs are very interesting from the point of view of plasma physics as well as practical implications because of their space weather impact.

  18. Partial oxidation of methane by pulsed corona discharges

    NASA Astrophysics Data System (ADS)

    Hoeben, W. F. L. M.; Boekhoven, W.; Beckers, F. J. C. M.; van Heesch, E. J. M.; Pemen, A. J. M.

    2014-09-01

    Pulsed corona-induced partial oxidation of methane in humid oxygen or carbon dioxide atmospheres has been investigated for future fuel synthesis applications. The obtained product spectrum is wide, i.e. saturated, unsaturated and oxygen-functional hydrocarbons. The generally observed methane conversion levels are 6-20% at a conversion efficiency of about 100-250 nmol J-1. The main products are ethane, ethylene and acetylene. Higher saturated hydrocarbons up to C6 have been detected. The observed oxygen-functional hydrocarbons are methanol, ethanol and lower concentrations of aldehydes, ketones, dimethylether and methylformate. Methanol seems to be exclusively produced with CH4/O2 mixtures at a maximum production efficiency of 0.35 nmol J-1. CH4/CO2 mixtures appear to yield higher hydrocarbons. Carboxylic acids appear to be mainly present in the aqueous reactor phase, possibly together with higher molecular weight species.

  19. Psychosis post corona radiata and lentiform nucleus infarction.

    PubMed

    Abang Abdullah, Khadijah Hasanah; Mohamed Saini, Suriati; Sharip, Shalisah; Abdul Rahman, Abdul Hamid

    2015-01-01

    Complications of stroke can include neuropsychiatric symptoms. However, post-stroke psychosis is rare. We report a case where an acute presentation of psychosis, depression and fluctuating cognitive impairment in a middle-aged man turned out to be related to a silent brain infarction. The patient had a background of poorly controlled type 2 diabetes mellitus with glycated haemoglobin level of 9.0-11.0%, hypertension and ischaemic heart disease. His CT brain results showed multifocal infarct with hypodensities at bilateral lentiform nucleus and bilateral corona radiata. His strong genetic predisposition of psychosis and a history of brief psychotic disorder with complete remission 3?years prior to the current presentation might possibly contribute to his post-stroke atypical neuropsychiatric presentation, and posed diagnostic challenges. He showed marked improvement with risperidone 6?mg nocte, chlorpromazine 50?mg nocte and fluvoxamine of 200?mg nocte. The need of comprehensive treatments to modify his stroke risk factors was addressed. PMID:25837653

  20. Radiative transfer of X-rays in the solar corona

    NASA Technical Reports Server (NTRS)

    Acton, L. W.

    1978-01-01

    The problem of resonance scattering of X-ray emission lines in the solar corona is investigated. For the resonance lines of some helium-like ions, significant optical depths are reached over distances small compared with the size of typical coronal features. A general integral equation for the transfer of resonance-line radiation under solar coronal conditions is derived. This expression is in a form useful for modeling the complex three-dimensional temperature and density structure of coronal active regions. The transfer equation is then cast in a form illustrating the terms which give rise to the attenuation or enhancement of the resonance-line intensity. The source function for helium-like oxygen (O VII) under coronal conditions is computed and discussed in terms of the relative importance of scattering.

  1. Variable Winds and Dust Formation in R Coronae Borealis Stars

    NASA Astrophysics Data System (ADS)

    Clayton, Geoffrey C.; Geballe, T. R.; Zhang, Wanshu

    2013-08-01

    We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I ?10830 lines of 12 R Coronae Borealis stars over short (1 month) and long (3 yr) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities ~400 km s-1 appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the decline and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.

  2. Stellar coronae - What can be predicted with minimum flux models?

    NASA Technical Reports Server (NTRS)

    Hammer, R.; Endler, F.; Ulmschneider, P.

    1983-01-01

    In order to determine the possible errors of various minimum flux corona (MFC) predictions, MFC models are compared with a grid of detailed coronal models covering a range of two orders of magnitude in coronal heating and damping length values. The MFC concept is totally unreliable in the prediction of mass loss and the relative importance of various kinds of energy losses, and MFC predictions for the mass loss rate and energy losses due to stellar wind can be wrong by many orders of magnitude. It is suggested that for future applications, the unreliable MFC formulas should be replaced by a grid of related models accounting for the coronal dependence on damping length, such as the models underlying the present study.

  3. VARIABLE WINDS AND DUST FORMATION IN R CORONAE BOREALIS STARS

    SciTech Connect

    Clayton, Geoffrey C.; Zhang Wanshu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Geballe, T. R., E-mail: gclayton@fenway.phys.lsu.edu, E-mail: wzhan21@lsu.edu, E-mail: tgeballe@gemini.edu [Gemini Observatory, 670 N. A'ohoku Place, Hilo, HI 96720 (United States)

    2013-08-01

    We have observed P-Cygni and asymmetric, blue-shifted absorption profiles in the He I {lambda}10830 lines of 12 R Coronae Borealis stars over short (1 month) and long (3 yr) timescales to look for variations linked to their dust-formation episodes. In almost all cases, the strengths and terminal velocities of the line vary significantly and are correlated with dust formation events. Strong absorption features with blue-shifted velocities {approx}400 km s{sup -1} appear during declines in visible brightness and persist for about 100 days after recovery to maximum brightness. Small residual winds of somewhat lower velocity are present outside of the decline and recovery periods. The correlations support models in which recently formed dust near the star is propelled outward at high speed by radiation pressure and drags the gas along with it.

  4. Modelling the Corona of HD 189733 in 3D

    NASA Astrophysics Data System (ADS)

    Strugarek, A.; Brun, A. S.; Matt, S. P.; Reville, V.; Donati, J. F.; Moutou, C.; Fares, R.

    2014-12-01

    The braking of main sequence stars originates mainly from their stellar wind. The efficiency of this angular momentum extraction depends on the rotation rate of the star, the acceleration profile of the wind and the coronal magnetic field. The derivation of scaling laws parametrizing the stellar wind torque is important for our understanding of gyro-chronology and the evolution of the rotation rates of stars. In order to understand the impact of complex magnetic topologies on the stellar wind torque, we present three-dimensional, dynamical simulations of the corona of HD 189733. Using the observed complex topology of the magnetic field, we estimate how the torque associated with the wind scales with model parameters and compare those trends to previously published scaling laws.

  5. Mid-infrared variations of R Coronae Borealis stars

    NASA Astrophysics Data System (ADS)

    Rao, N. Kameswara; Lambert, David L.

    2015-03-01

    Mid-infrared (IR) photometry of R Coronae Borealis stars obtained from various satellites from Infrared Astronomical Satellite (IRAS) to Wide-field Infrared Survey Explorer (WISE) has been utilized in studying the variations of the circumstellar dust's contributions to the spectral energy distribution of these stars. The variation of the fractional coverage (R) of dust clouds and their blackbody temperatures (Td) have been used in trying to understand the dust cloud evolution over the three decades spanned by the satellite observations. In particular, it is shown that a prediction R ? T_d^4 developed in the paper is satisfied, especially by those stars for which a single collection of clouds dominates the IR fluxes.

  6. Multiphysics simulation of corona discharge induced ionic wind

    NASA Astrophysics Data System (ADS)

    Cagnoni, Davide; Agostini, Francesco; Christen, Thomas; Parolini, Nicola; Stevanovi?, Ivica; de Falco, Carlo

    2013-12-01

    Ionic wind devices or electrostatic fluid accelerators are becoming of increasing interest as tools for thermal management, in particular for semiconductor devices. In this work, we present a numerical model for predicting the performance of such devices; its main benefit is the ability to accurately predict the amount of charge injected from the corona electrode. Our multiphysics numerical model consists of a highly nonlinear, strongly coupled set of partial differential equations including the Navier-Stokes equations for fluid flow, Poisson's equation for electrostatic potential, charge continuity, and heat transfer equations. To solve this system we employ a staggered solution algorithm that generalizes Gummel's algorithm for charge transport in semiconductors. Predictions of our simulations are verified and validated by comparison with experimental measurements of integral physical quantities, which are shown to closely match.

  7. Is the galactic corona produced by galactic flares?

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Stern, R.

    1979-01-01

    The effect of the differential rotation of the disk of the Galaxy on magnetic field which penetrates the disk is considered. The magnetic field will be progressively distorted from a potential (current-free) form and will at some stage become unstable. It is expected that an MHD instability, a resistive instability, or a combination of the two, will result in the release of the excess magnetic energy and that part of the released energy will be converted into heat. By estimating the energy release and the rate at which this process will occur and by assuming that this energy input is balanced by radiation, estimates were obtained of the parameters of the resulting plasma. It appears that this process alone can heat a galactic corona to temperatures of order 10 to the 6th power K.

  8. A search for Class 0 protostars in Corona Australis

    NASA Astrophysics Data System (ADS)

    Harju, Jorma; Higdon, Jim; Lehtinen, Kimmo; Juvela, Mika

    1999-10-01

    The R Coronae Australis core was imaged with the Australia Telescope Compact Array (ATCA) in continuum at 3 and 6 cm. The aim was to investigate if any of the quiescent DCO+ clumps detected recently (Anderson et al. 1999) contain compact HII regions. Such a source in a dense clump without associated infrared emission may indicate the presence of a very young protostar. No continuum sources, except those previously detected with the VLA (Brown 1987) were found. In particular, no trace was found of the compact radio continuum source in the southern part of the core reported on by Brown & Zuckerman (1975). The properties of the detected continuum sources, their infrared counterparts and their relation to the surrounding molecular material are discussed. Anderson I.M., Caselli P., Haikala L.K., Harju J. 1999, A&A 347, 983 Brown A. 1987, ApJ 322, L31 Brown R.L., Zuckerman B. 1975, ApJ 202, L125

  9. Proton Implantation into Tungsten Phosphate Glass Using Corona Discharging

    NASA Astrophysics Data System (ADS)

    Shoji, T.; Ikeda, H.; Mayama, H.; Nishiyama, H.; Nishii, J.

    Phosphate glass with composition of 35NaO1/2-20WO3-45PO5/2 prepared by a conventional melt-quenching method was treated by a positive corona discharging at room temperature. It was found that the OH concentration in the top surface layer of the glass increased by the treatment of +6.0-7.5 kV, for 10 h in 5%H2-95%N2 atmosphere and 5.0 mm in positive electrode and glass surface distance. On the other hand, the Na ion in the same area of 15 ?m thickness diffused and precipitated to the bottom surface. It was found by the infrared and Raman spectra that the Na was replaced by implanted proton without notable structural change.

  10. Multiphysics simulation of corona discharge induced ionic wind

    SciTech Connect

    Cagnoni, Davide [ABB Switzerland Ltd., Corporate Research, CH-5405 Baden-Dättwil (Switzerland) [ABB Switzerland Ltd., Corporate Research, CH-5405 Baden-Dättwil (Switzerland); MOX - Dipartimento di Matematica “F. Brioschi,” Politecnico di Milano, 20133 Milano (Italy); Agostini, Francesco; Christen, Thomas [ABB Switzerland Ltd., Corporate Research, CH-5405 Baden-Dättwil (Switzerland)] [ABB Switzerland Ltd., Corporate Research, CH-5405 Baden-Dättwil (Switzerland); Parolini, Nicola [MOX - Dipartimento di Matematica “F. Brioschi,” Politecnico di Milano, 20133 Milano (Italy)] [MOX - Dipartimento di Matematica “F. Brioschi,” Politecnico di Milano, 20133 Milano (Italy); Stevanovi?, Ivica [ABB Switzerland Ltd., Corporate Research, CH-5405 Baden-Dättwil (Switzerland) [ABB Switzerland Ltd., Corporate Research, CH-5405 Baden-Dättwil (Switzerland); Laboratory of Electromagnetics and Acoustics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Falco, Carlo de [MOX - Dipartimento di Matematica “F. Brioschi,” Politecnico di Milano, 20133 Milano (Italy) [MOX - Dipartimento di Matematica “F. Brioschi,” Politecnico di Milano, 20133 Milano (Italy); CEN - Centro Europeo di Nanomedicina, 20133 Milano (Italy)

    2013-12-21

    Ionic wind devices or electrostatic fluid accelerators are becoming of increasing interest as tools for thermal management, in particular for semiconductor devices. In this work, we present a numerical model for predicting the performance of such devices; its main benefit is the ability to accurately predict the amount of charge injected from the corona electrode. Our multiphysics numerical model consists of a highly nonlinear, strongly coupled set of partial differential equations including the Navier-Stokes equations for fluid flow, Poisson's equation for electrostatic potential, charge continuity, and heat transfer equations. To solve this system we employ a staggered solution algorithm that generalizes Gummel's algorithm for charge transport in semiconductors. Predictions of our simulations are verified and validated by comparison with experimental measurements of integral physical quantities, which are shown to closely match.

  11. Large Scale Circumgalactic Coronae around Massive Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Li, Jiangtao

    2013-10-01

    Extended coronae around massive spiral galaxies is a key prediction of galaxy formation theory. There are very few such galaxies in the local Universe and even fewer deep X-ray observations of them. We propose to observe 5 luminous, fast rotating, isolated, SF quiescent, and massive spiral galaxies with a total effective exposure of 337ks with XMM-Newton. When combined with archival X-ray observations of 4 other galaxies, the proposal will enable us to compile a mini-sample optimized to constrain the mechanisms responsible for establishing the hot CGM. We will compare radial distributions of coronal properties to the state-of-the-art hydrodynamical simulations, measure the total baryon content, and establish scaling relations of the coronal and other galaxy properties.

  12. Burgulence and Alfven waves heating mechanism of solar corona

    E-print Network

    T. M. Mishonov; Y. G. Maneva

    2007-01-16

    Heating of magnetized turbulent plasma is calculated in the framework of Burgers turbulence [A.M. Polyakov, Phys. Rev. E. 52, 6183 (1995)]. Explicit formula for the energy flux of Alfven waves along the magnetic field is presented. The Alfven waves are considered as intermediary between the turbulent energy and the heat. The derived results are related to a wave channel of heating of the solar corona. If we incorporate amplification of Alfven waves by shear flow the suggested model of heating can be applied to analysis of the missing viscosity of accretion discs and to reveal why the quasars are the most powerful sources of light in the universe. We suppose that the Langevin-Burgers approach to turbulence we have applied in the current work can be also helpful for other systems where we have intensive interaction between a stochastic turbulent system and waves and can be used in many multidisciplinary researches in hydrodynamics and MHD.

  13. Is the galactic corona produced by galactic flares

    NASA Astrophysics Data System (ADS)

    Sturrock, P. A.; Stern, R.

    1980-05-01

    The effect of the differential rotation of the disk of the galaxy on magnetic field which penetrates the disk is considered. The magnetic field will be progressively distorted from a potential (current-free) form and will at some stage become unstable. We expect, from knowledge of solar flares, that an MHD instability, a resistive instability, or a combination of the two, will result in the release of the excess magnetic energy, and that part of the released energy will be converted into heat. By estimating the energy release and the rate at which this process will occur and by assuming that this energy input is balanced by radiation, we obtain estimates of the parameters of the resulting plasma. It appears that this process alone can heat a galactic corona to temperatures of order one-million K.

  14. Buoyant subduction on Venus: Implications for subduction around coronae

    NASA Technical Reports Server (NTRS)

    Burt, J. D.; Head, J. W.

    1993-01-01

    Potentially low lithospheric densities, caused by high Venus surface and perhaps mantle temperatures, could inhibit the development of negative buoyancy-driven subduction and a global system of plate tectonics/crustal recycling on that planet. No evidence for a global plate tectonic system was found so far, however, specific features strongly resembling terrestrial subduction zones in planform and topographic cross-section were described, including trenches around large coronae and chasmata in eastern Aphrodite Terra. The cause for the absence, or an altered expression, of plate tectonics on Venus remains to be found. Slab buoyancy may play a role in this difference, with higher lithospheric temperatures and a tendency toward positive buoyancy acting to oppose the descent of slabs and favoring under thrusting instead. The effect of slab buoyancy on subduction was explored and the conditions which would lead to under thrusting versus those allowing the formation of trenches and self-perpetuating subduction were defined. Applying a finite element code to assess the effects of buoyant forces on slabs subducting into a viscous mantle, it was found that mantle flow induced by horizontal motion of the convergent lithosphere greatly influences subduction angle, while buoyancy forces produce a lesser effect. Induced mantle flow tends to decrease subduction angle to near an under thrusting position when the subducting lithosphere converges on a stationary overriding lithosphere. When the overriding lithosphere is in motion, as in the case of an expanding corona, subduction angles are expected to increase. An initial stage involved estimating the changes in slab buoyancy due to slab healing and pressurization over the course of subduction. Modeling a slab, descending at a fixed angle and heated by conduction, radioactivity, and the heat released in phase changes, slab material density changes due to changing temperature, phase, and pressure were derived.

  15. THE EXPANSION OF ACTIVE REGIONS INTO THE EXTENDED SOLAR CORONA

    SciTech Connect

    Morgan, Huw; Jeska, Lauren; Leonard, Drew, E-mail: hmorgan@aber.ac.uk [Sefydliad Mathemateg a Ffiseg, Prifysgol Aberystwyth, Ceredigion SY23 3BZ (United Kingdom)

    2013-06-01

    Advanced image processing of Large Angle and Spectrometric Coronagraph Experiment (LASCO) C2 observations reveals the expansion of the active region closed field into the extended corona. The nested closed-loop systems are large, with an apparent latitudinal extent of 50 Degree-Sign , and expanding to heights of at least 12 R{sub Sun }. The expansion speeds are {approx}10 km s{sup -1} in the AIA/SDO field of view, below {approx}20 km s{sup -1} at 2.3 R{sub Sun }, and accelerate linearly to {approx}60 km s{sup -1} at 5 R{sub Sun }. They appear with a frequency of one every {approx}3 hr over a time period of around three days. They are not coronal mass ejections (CMEs) since their gradual expansion is continuous and steady. They are also faint, with an upper limit of 3% of the brightness of background streamers. Extreme ultraviolet images reveal continuous birth and expansion of hot, bright loops from a new active region at the base of the system. The LASCO images show that the loops span a radial fan-like system of streamers, suggesting that they are not propagating within the main coronal streamer structure. The expanding loops brighten at low heights a few hours prior to a CME eruption, and the expansion process is temporarily halted as the closed field system is swept away. Closed magnetic structures from some active regions are not isolated from the extended corona and solar wind, but can expand to large heights in the form of quiescent expanding loops.

  16. Current Sheet Formation and Reconnection Dynamics in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Edmondson, Justin K.; Antiochos, S. K.; DeVore, C.; Zurbuchen, T. H.

    2009-05-01

    Current sheet formation is a necessary consequence of the evolution of the multi-polar magnetic field topologies that are ubiquitous throughout the solar corona. We present a very high-resolution study of 3D MHD current sheet formation and the resulting reconnection dynamics in an environment appropriate for the corona. The initial field consists of a translationally invariant, potential field with a null-point topology (i.e., 4-flux systems) and a low-beta plasma. A finite-extent, 3D Syrovatskii-type current sheet forms as a result of stressing of this system by a uniform, incompressible flow applied at the line-tied photospheric boundary. The system is assumed to be ideal, except for the presence of numerical resistivity. The fully 3-D evolution is calculated with very high resolution (9x and 10x refinement across the full extent of the current sheet) using the Adaptively Refined MHD Solver (ARMS). The initial evolution of this computationally-intensive simulation results in a current sheet with a nearly 30-to-1 aspect ratio, a significant fraction of the system characteristic length, that unexpectedly appears to be stable. In addition, up to this point in the evolution any magnetic reconnection that we observe is of the slow Sweet-Parker type. We expect, however, that as we continue stressing the field, the current sheet will become unstable and develop explosive dynamics. We discuss the implications of our results on coronal structure and activity, such as heating and eruptions. This work has been supported, in part, by the NASA HTP and SR&T programs.

  17. Remote-sensing Observations of the Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Sheeley, Neil R., Jr.

    2009-05-01

    On June 25, 1908, George Ellery Hale used the 60-foot Tower Telescope on Mount Wilson to make the first measurements of magnetic fields in sunspots. This began a series of studies that led to Hale's Law of sunspot polarities and established the Mount Wilson Observatory as a leading center of solar magnetic field research. The magnetic aura was still present in 1962 when I began solar research there as a Caltech graduate student. Mount Wilson astronomer Horace Babcock and his father had invented the solar magnetograph, discovered the polar fields of the Sun, and observed their reversal near the 1958 sunspot maximum. Caltech physicist Robert Leighton had added new instrumentation to the Mount Wilson spectroheliograph and obtained high-resolution maps of the magnetic field. Babcock had just published his classic paper on the topology of the field and its 22-year cycle. The paper contained a sketch, illustrating the coronal field-line reconnection, which he thought must occur in response to changes of the photospheric field. Some loops flew away in the yet-to-be-discovered solar wind and other loops collapsed back to the Sun. In this talk, I will present new observations from the SOHO and STEREO spacecraft, which show such coronal changes. Loops stretch out in the expanding corona and tear away from the Sun like drops from a leaky faucet. Simultaneous observations with different perspectives show that the detached loops are really helices in 3-D. Off-pointed heliospheric imagers allow us to track these ejections outward past planets (including Earth) and comets, and to observe their compression into a heliospheric spiral, as a consequence of longitudinal speed gradients on the rotating Sun. And XUV observations of the solar disk show brightness changes associated with reconnections high in the corona, like auroral displays in the magnetosphere.

  18. Research on characteristics of electromagnetic radiation of corona discharges from high voltage transmission lines

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Liu, Shang-he; Wei, Ming; Hu, Xiao-feng

    2013-03-01

    With the development and application of ultra high voltage electric power transmitting technology, harmful effects of corona discharges to the safe and stable operation of the ultra high voltage (UHV) transmission lines should be considered. In this paper, the radiation law of corona discharges was studied by theoretical analysis and laboratory simulation. Correlated conclusions include that the waveform of corona discharges is in attenuated oscillation mode, the signal of the radiation field increases with increasing charging voltage, whereas the signal amplitude the antenna receives is attenuated with the distance from 3 m to 24 m.

  19. On the nature of the transition region between the solar corona and chromosphere

    NASA Astrophysics Data System (ADS)

    Ptitsyna, O. V.; Somov, B. V.

    2012-12-01

    We have calculated an equilibrium temperature distribution over the column depth of plasma in the transition region between the solar corona and chromosphere by assuming the plasma in the transition region and the chromosphere to be heated by the heat flux from the corona and the energy fluxes from the convective zone, respectively. The corona-chromosphere transition region is shown to be actually a stable, very thin layer in which, however, the standard collision approximation is well applicable for describing the heat flux. The solution we found explains well the currently available results of satellite observations of extreme ultraviolet (EUV) radiation from the transition region.

  20. Corona Formation and Heat Loss on Venus by Coupled Upwelling and Delamination

    NASA Technical Reports Server (NTRS)

    Smrekar, Suzanne E.; Stofan, Ellen R.

    1997-01-01

    Coronae are volcanotectonic features that are unique to Venus and are interpreted to be small-scale upwellings. A model in which upwelling causes delamination at the edge of the plume head, along with deformation of a pre-existing depleted mantel Layer, can produce the full range of topographic forms of coronae. If half of the coronae are active, delamination of the lower lithosphere could account for about 10% of venus's heat loss, with another 15% due to upwelling. Delamination may occur in other geologic enviroment and could help account for 'Venus' heat loss 'deficit'.

  1. Effect of configuration and dimensions of reactor electrodes on electrical and optical corona discharge characteristics

    SciTech Connect

    El-Koramy, Reda Ahmed; Yehia, Ashraf; Omer, Mohamed [Department of Physics, Faculty of Science, Assiut University, 71516 Assiut (Egypt)

    2010-05-15

    An experimental parametric study is made to investigate how the electrical corona discharge characteristics are influenced by the geometrical configuration and dimensions of the reactor and the electrode polarity of the applied voltage. Furthermore, features of the corona discharge plasma formed around the stressed electrode in some different gases are recorded photographically to provide more information on the physical mechanisms of the corona discharge in the investigated gases. The obtained results have been discussed in the light of gas discharge physics and its applications.

  2. Neutron Production in Black Hole Coronae and Proton Loading of Jets

    NASA Astrophysics Data System (ADS)

    Vila, Gabriela S.; Vieyro, Florencia L.; Romero, Gustavo E.

    2014-03-01

    We study the production of neutrons in the corona of an accreting black hole through the interaction of locally accelerated protons with matter and radiation. A fraction of these neutrons may escape and penetrate into the base of the jet, later decaying into protons. This is a possible mechanism for loading Poynting-dominated outflows with baryons. We characterize the spatial and energy distribution of neutrons in the corona and that of the protons injected in the jet by neutron decay. We assess the contribution of these protons to the radiative spectrum of the jet. We also investigate the fate of the neutrons that escape the corona into the external medium.

  3. Characteristics of corona impulses from insulated wires subjected to high ac voltages

    NASA Technical Reports Server (NTRS)

    Doreswamy, C. V.; Crowell, C. S.

    1976-01-01

    Corona discharges arise due to ionization of air or gas subject to high electric fields. The free electrons and ions contained in these discharges interact with molecules of insulating materials, resulting in chemical changes and destroying the electrical insulating properties. The paper describes some results of measurements aimed at determining corona pulse waveforms, their repetition rate, and amplitude distribution during various randomly-sampled identical time periods of a 60-Hz high-voltage wave. Described are properties of positive and negative corona impulses generated from typical conductors at various test high voltages. A possible method for calculating the energies, densities, and electromagnetic interferences by making use of these results is suggested.

  4. HEATING IN AN EXTENDED ACCRETION DISK CORONA ALONG THE Z-PATTERN IN CYG X-2

    E-print Network

    Schulz, Norbert S.

    We observed at very high spectral resolution the prototype Z-source Cyg X-2 twice along its entire X-ray spectral variation pattern. In this preliminary analysis, we find an extended accretion disk corona (ADC) exhibiting ...

  5. K-corona recording in the range < 1.4 Rsun

    E-print Network

    Kim, I S; Lisin, D V; Nasonova, L P

    2015-01-01

    Two approaches are suggested for recording the continuum corona in the range eclipses at near-Mercury orbits. The instrumental background is decreased at least 3 orders of magnitude. That allows using a more simplified optical sketch.

  6. IUE and the search for a lukewarm corona. [of cooler stars

    NASA Technical Reports Server (NTRS)

    Pasachoff, J. M.; Linsky, J. L.; Haisch, B. M.; Boggess, A.

    1979-01-01

    The use of the International Ultraviolet Explorer (IUE) to search for stars having neither a hot corona nor a cool outer atmosphere, but a lukewarm corona is outlined. An interactive computer system permits extensive analysis of the data immediately after transmission to earth, allowing the results of one exposure to influence the taking of subsequent exposures. The observation program is illustrated for the star HR 1099, noting that observations were taken while previous spectra were being analyzed. Observations of many stars of spectral types G and K lead to the construction of a border region on the Hertzsprung-Russell diagram between stars with hot coronas and those with cool outer atmospheres. Stars lying near this border region were then observed, however none with lukewarm coronas were found. The interactive control facility in the satellite control room is considered an important factor in the efficient implementation of the search procedure.

  7. Venusian Coronae with Variable Elastic Thickness as a Function of Wavelength

    NASA Technical Reports Server (NTRS)

    Anderson, F. S.; Smrekar, S. E.

    2000-01-01

    The gravity of approx. 30 coronae have been studied using 2 admittance methods to assess differences in elastic thickness and to see if they correlate with morphology or geologic setting, in addition to attempting to constrain subsurface structure.

  8. The 1981 total solar eclipse corona. II - Global absolute photometric analysis

    NASA Astrophysics Data System (ADS)

    Lebecq, C.; Koutchmy, S.; Stellmacher, G.

    1985-11-01

    Detailed results of the absolute photometry of the solar corona during the July 31, 1981 total eclipse are presented together with a morphological analysis. The basic calibration method uses the detailed photometry of images of stars present on the same coronal picture. Both sky intensity and coronal aureola variations over the field are carefully evaluated. The recent axi-symmetric non-spherical model of the F-corona is introduced and the relevant K-corona intensity variations are derived. The determinations of the Ludendorf index of flattening and the integrated total brightness of the K-corona alone are made and discussed in relation to the phase of the sunspot cycle of activity.

  9. Diagnostics of the Solar corona from Comparison Between Faraday Rotation Measurements and MHD Simulations

    NASA Astrophysics Data System (ADS)

    LE CHAT, G.; Kasper, J. C.; Cohen, O.; Spangler, S.

    2013-05-01

    Faraday rotation observations of natural radio sources allow remote diagnostics of the density and magnetic field of the solar corona. We use linear polarization observations made with the NRAO Very Large Array at frequencies of 1465 and 1665 MHz of 33 polarized radio sources occulted by the solar corona within 5 to 14 solar radii. The measurements were made during May 1997 (Mancuso and Spangler, 2000), March 2005 and april 2005 (Ingleby et al., 2005), corresponding to Carrington rotation number 1922, 1923, 2027 and 2028. We compare the observed Faraday rotation values with values extracted from MHD steady-state simulations of the solar corona using the BATS-R-US model. The simulations are driven by magnetogram data taken at the same time as the observed data. We present the agreement between the model and the Faraday rotation measurements, and we discuss the contraints imposed on models of the quiet corona and CMEs by these observations.

  10. Effect of the protein corona on nanoparticles for modulating cytotoxicity and immunotoxicity

    PubMed Central

    Lee, Yeon Kyung; Choi, Eun-Ju; Webster, Thomas J; Kim, Sang-Hyun; Khang, Dongwoo

    2015-01-01

    Although the cytotoxicity of nanoparticles (NPs) is greatly influenced by their interactions with blood proteins, toxic effects resulting from blood interactions are often ignored in the development and use of nanostructured biomaterials for in vivo applications. Protein coronas created during the initial reaction with NPs can determine the subsequent immunological cascade, and protein coronas formed on NPs can either stimulate or mitigate the immune response. Along these lines, the understanding of NP-protein corona formation in terms of physiochemical surface properties of the NPs and NP interactions with the immune system components in blood is an essential step for evaluating NP toxicity for in vivo therapeutics. This article reviews the most recent developments in NP-based protein coronas through the modification of NP surface properties and discusses the associated immune responses. PMID:25565807

  11. Transfer of electrical space charge from corona between ground and thundercloud: Measurements and modeling

    NASA Technical Reports Server (NTRS)

    Soula, Serge

    1994-01-01

    The evolution of the vertical electric field profile deduced from simultaneous field measurements at several levels below a thundercloud shows the development of a space charge layer at least up to 600 m. The average charge density in the whole layer from 0 m to 600 m can reach about 1 nC m(exp -3). The ions are generated at the ground by corona effect and the production rate is evaluated with a new method from the comparison of field evolutions at the ground and at altitude after a lightning flash. The modeling of the relevant processes shows tht ground corona accounts for the observed field evolutions and that the aerosol particles concentration has a very large effect on the evolution of corona ions. However, with a realistic value for this concentration a large amount of ground corona ions reach the level of 600 m.

  12. 75 FR 8395 - Bunker Hill Groundwater Basin, Riverside-Corona Feeder Project, San Bernardino and Riverside...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ...INTERIOR Bureau of Reclamation Bunker Hill Groundwater Basin, Riverside-Corona Feeder Project...recovery project. The project will install new groundwater wells at the Bunker Hill Groundwater Basin in San Bernardino County with...

  13. The nature of the corona around Beta Draconis (G2 Ib-II)

    NASA Astrophysics Data System (ADS)

    Hearn, A. G.

    The coronal model calculations for OB supergiants of Hearn and Vardavas (1981) have been scaled using the coronal scaling law of Hammer (1984) to study the corona around Beta Draconis. Beta Draconis lies close to the Linsky-Haisch dividing line on the H-R diagram. A comparison of the models with the interpretation of the observations by Brown et al. (1984) shows that the corona around Beta Draconis cannot be an open, spherically symmetric corona, and must be contained presumably by coronal loops. The Linsky-Haisch dividing line cannot be explained by the thermal instability of extended coronae. The explanation must presumably be sought in the physics of coronal loops as has been suggesed by Antiochos and Noci (1986).

  14. Ionization phenomenon in high-density gaseous and liquid argon in corona discharge experiments

    Microsoft Academic Search

    N. Bonifaci; A. Denat; V. Atrazhev

    1997-01-01

    Experimental investigations of corona discharge in Ar for a wide region of fluid density from a rare gas up to a liquid have been carried out. Corona current has been observed for a point cathode voltage above the threshold value 0022-3727\\/30\\/19\\/010\\/img6. Values of 0022-3727\\/30\\/19\\/010\\/img6 have been measured for a wide range of fluid density N and for different cathode radii

  15. The Effects of Geometry on the Corona-to-Streamer Discharge Transition

    E-print Network

    Humbird, Kelli D

    2013-01-31

    UNDERGRADUATE RESEARCH SCHOLAR THE EFFECTS OF GEOMETRY ON THE CORONA-TO- STREAMER DISCHARGE TRANSITION An Undergraduate Research Scholars Thesis by KELLI DENISE HUMBIRD Approved by Research Advisor: Dr. William Marlow... ........................................................................................................................24 2 ABSTRACT The Effects of Geometry on the Corona-to-Streamer Discharge Transition. (May 2013) Kelli Denise Humbird Department of Nuclear Engineering Texas A&M University Research Advisor: Dr. William Marlow Department of Nuclear...

  16. A GENERAL RELATIVISTIC MODEL OF ACCRETION DISKS WITH CORONAE SURROUNDING KERR BLACK HOLES

    SciTech Connect

    You Bei; Cao Xinwu [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Yuan Yefei, E-mail: youbei@shao.ac.cn, E-mail: cxw@shao.ac.cn, E-mail: yfyuan@ustc.edu.cn [Department of Astronomy, University of Sciences and Technology of China, Hefei, Anhui 230026 (China)

    2012-12-20

    We calculate the structure of a standard accretion disk with a corona surrounding a massive Kerr black hole in the general relativistic frame, in which the corona is assumed to be heated by the reconnection of the strongly buoyant magnetic fields generated in the cold accretion disk. The emergent spectra of accretion disk-corona systems are calculated by using the relativistic ray-tracing method. We propose a new method to calculate the emergent Comptonized spectra from the coronae. The spectra of disk-corona systems with a modified {alpha}-magnetic stress show that both the hard X-ray spectral index and the hard X-ray bolometric correction factor L{sub bol}/L{sub X,2-10keV} increase with the dimensionless mass accretion rate, which is qualitatively consistent with the observations of active galactic nuclei. The fraction of the power dissipated in the corona decreases with increasing black hole spin parameter a, which leads to lower electron temperatures of the coronae for rapidly spinning black holes. The X-ray emission from the coronae surrounding rapidly spinning black holes becomes weak and soft. The ratio of the X-ray luminosity to the optical/UV luminosity increases with the viewing angle, while the spectral shape in the X-ray band is insensitive to the viewing angle. We find that the spectral index in the infrared waveband depends on the mass accretion rate and the black hole spin a, which deviates from the f{sub {nu}}{proportional_to}{nu}{sup 1/3} relation expected by the standard thin disk model.

  17. HERSCHEL\\/SCORE, imaging the solar corona in visible and EUV light: CCD camera characterization

    Microsoft Academic Search

    M. Pancrazzi; M. Focardi; F. Landini; M. Romoli; S. Fineschi; A. Gherardi; E. Pace; G. Massone; E. Antonucci; D. Moses; J. Newmark; D. Wang; G. Rossi

    2010-01-01

    The HERSCHEL (helium resonant scattering in the corona and heliosphere) experiment is a rocket mission that was successfully\\u000a launched last September from White Sands Missile Range, New Mexico, USA. HERSCHEL was conceived to investigate the solar corona\\u000a in the extreme UV (EUV) and in the visible broadband polarized brightness and provided, for the first time, a global map of\\u000a helium

  18. New method for measuring the stochastic properties of corona and partial discharge pulses

    Microsoft Academic Search

    R. J. Van Brunt; S. V. Kulkarni

    1988-01-01

    A computer-based method for measuring the stochastic properties of corona and partial-discharge pulses is described. Application of the method to ultraviolet sustained negative-corona (Trichel) pulses in air has shown the existence of strong correlations between pulse amplitudes and subsequent pulse time intervals as well as between amplitudes of successive pulses. The observed correlations are consistent with existing models for Trichel-pulse

  19. Influence of a dielectric barrier on the stochastic behaviour of Trichel-pulse corona

    Microsoft Academic Search

    R. J. Van Brunt; M. Misakian; S. V. Kulkarni; V. K. Lakdawala

    1991-01-01

    The influence of a solid polytetrafluorethylene (PTFE) dielectric barrier on the stochastic behaviour of negative (Trichel) pulse corona discharges in air is examined. This behavior is revealed from measurement of conditional and unconditional corona pulse-amplitude and pulse-time--separation distributions. The results indicate that the presence of a dielectric surface on the anode effectively reduces the electric field at the point electrode,

  20. On the mechanism of the cathode erosion in negative corona discharge

    Microsoft Academic Search

    Alexey Petrov; Ravil Amirov; Igor Samoylov

    2009-01-01

    Negative corona discharge was investigated in atmospheric pressure air and SF6 in Trichel pulse and glow mode in point-to-plane electrode configuration. As a cathode pointed carbon, copper and aluminum pins with tip size 0.02-1 mm were used. It is found that negative corona causes the erosion of cathode surface in form of nanometer-size craters and fissures. Observed etching may be

  1. Hi-C Observations of an Active Region Corona, and Investigation of the Underlying Magnetic Structure

    NASA Technical Reports Server (NTRS)

    Tiwari, S. K.; Alexander, C. E.; Winebarger, A.; Moore, R. L.

    2014-01-01

    The solar corona is much hotter (>=10(exp 6) K) than its surface (approx 6000 K), puzzling astrophysicists for several decades. Active region (AR) corona is again hotter than the quiet Sun (QS) corona by a factor of 4-10. The most widely accepted mechanism that could heat the active region corona is the energy release by current dissipation via reconnection of braided magnetic field structure, first proposed by E. N. Parker three decades ago. The first observational evidence for this mechanism has only recently been presented by Cirtain et al. by using High-resolution Coronal Imager (Hi-C) observations of an AR corona at a spatial resolution of 0.2 arcsec, which is required to resolve the coronal loops, and was not available before the rocket flight of Hi-C in July 2012. The Hi-C project is led by NASA/MSFC. In the case of the QS, work done by convection/granulation on the inter-granular feet of the coronal field lines translates into the heat observed in the corona. In the case of the AR, as here, there could be flux emergence, cancellation/submergence, or shear flows generating large stress and tension in coronal field loops which is released as heat in the corona. We are currently investigating the changes taking place in photospheric feet of the magnetic field involved with brightenings in the Hi-C AR corona. For this purpose, we are also using SDO/AIA data of +/- 2 hours around the 5 minutes Hi-C flight. In the present talk, I will first summarize some of the results of the Hi-C observations and then present some results from our recent analysis on what photospheric processes feed the magnetic energy that dissipates into heat in coronal loops.

  2. Assimilative 3D Models of Density and Temperature in the Solar Corona

    Microsoft Academic Search

    F. Kamalabadi; M. Butala; R. Frazin; Y. Chen

    2007-01-01

    White-light and extreme ultraviolet images of the solar corona, as measured routinely by a variety of dedicated space- and ground-based instruments, offer an opportunity for empirical determination of the global, 3D distribution of density and temperature in the Sun's corona. In this work, we describe a 3D model for the estimation of coronal density from polarized brightness measurements and a

  3. Driving extreme variability: the evolving corona and evidence for jet launching in Markarian 335

    NASA Astrophysics Data System (ADS)

    Wilkins, D. R.; Gallo, L. C.

    2015-05-01

    Variations in the X-ray emission from the narrow-line Seyfert 1 galaxy, Markarian 335, are studied on both long and short time-scales through observations made between 2006 and 2013 with XMM-Newton, Suzaku and NuSTAR. Changes in the geometry and energetics of the corona that give rise to this variability are inferred through measurements of the relativistically blurred reflection seen from the accretion disc. On long time-scales, we find that during the high-flux epochs the corona has expanded, covering the inner regions of the accretion disc out to a radius of 26_{-7}^{+10} rg. The corona contracts to within 12rg and 5rg in the intermediate- and low-flux epochs, respectively. While the earlier high-flux observation made in 2006 is consistent with a corona extending over the inner part of the accretion disc, a later high-flux observation that year revealed that the X-ray source had become collimated into a vertically extended jet-like corona and suggested relativistic motion of material upwards. On short time-scales, we find that an X-ray flare during a low-flux epoch in 2013 corresponded to a reconfiguration from a slightly extended corona to one much more compact, within just 2 ˜ 3rg of the black hole. There is evidence that during the flare itself, the spectrum softened and the corona became collimated and slightly extended vertically as if a jet-launching event was aborted. Understanding the evolution of the X-ray emitting corona may reveal the underlying mechanism by which the luminous X-ray sources in AGN are powered.

  4. Formation of ozone and oxidation of methane in a direct current corona discharge

    E-print Network

    Tangirala, Umashanker

    1976-01-01

    FORMATION OF OZONE AND OXIDATION OF METHANE IN A DIRECT CURRENT CORONA DISCHARGE A Thesis by UMASHANKER TANGIRALA Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree of MASTER... OF SCIENCE May 1976 Major Subject: Chemical Engineering FORMATION OF OZONE AND OXIDATION OF METHANE IN A DIRECT CURRENT CORONA DISCHARGE A Thesis by UMASHANKER TANGIRALA Approved as to style and content by: (Chairman of Committee) ( ad of Department...

  5. Corona induced non-thermal plasmas: Fundamental study and industrial applications

    Microsoft Academic Search

    Keping Yan; Hexing Hui; Mi Cui; Jinsong Miao; Xiaoli Wu; Chongguang Bao; Ruinian Li

    1998-01-01

    Our investigations on corona induced non-thermal plasmas include both fundamental study and products development. This paper presents our recent work in following subjects: investigation on characteristics of pulsed corona discharge in relation with flue gas cleaning; evaluation of high voltage power supply; design of plasma reactor; experimental study on DeNOx and DeSO2; decomposition of VOCs and indoor air cleaning.

  6. Central motor conduction studies in internal capsule and corona radiata infarction

    Microsoft Academic Search

    U. K. Misra; J. Kalita

    1997-01-01

    Clinical and evoked-potential studies in internal capsule and corona radiata infarction are lacking. We report the results\\u000a of a clinical and central motor conduction time (CMCT) study in 16 patients with internal capsule and 17 with computed tomography\\u000a (CT)-proven corona radiata infarction. Patient’s outcome was defined at the end of 3 months on the basis of the Barthel Index\\u000a score.

  7. ApJ, in press On Heating of Solar Corona and Acceleration of Low-Speed Solar Wind by Acoustic Waves Generated in Corona

    E-print Network

    Takeru Ken Suzuki

    2002-01-01

    We investigate possibilities of solar coronal heating by acoustic waves generated not at the photosphere but in the corona, aiming at heating in the mid- to low-latitude corona where the low-speed wind is expected to come from. Acoustic waves of period ? ? 100s are triggered by chromospheric reconnection, one model of small scale magnetic reconnection events recently proposed by Sturrock. These waves having a finite amplitude eventually form shocks to shape sawtooth waves (N-waves), and directly heat the surrounding corona by dissipation of their wave energy. Outward propagation of the N-waves is treated based on the weak shock theory, so that the heating rate can be evaluated consistently with physical properties of the background coronal plasma without setting a dissipation length in an ad hoc manner. We construct coronal structures from the upper chromosphere to the outside of 1AU for various inputs of the acoustic waves having a range of energy flux of Fw,0 = (1 ? 20) × 10 5 erg cm ?2 s ?1 and a period of ? = 60 ? 300s. The heating by the N-wave dissipation effectively works in the inner corona and we find that the waves of Fw,0 ? 2×10 5 erg cm ?2 s ?1 and ? ? 60s could maintain peak coronal temperature, Tmax> 10 6 K. The model could also reproduce the density profile observed in the streamer region. However, due to its short dissipation length, the location of Tmax is closer to the surface than the observation, and the resultant flow velocity of the solar wind is lower than the observed profile of the low-speed wind. The cooperations with other heating and acceleration sources with the larger dissipation length are inevitable to reproduce the real solar corona. Subject headings: Sun: corona — solar wind — waves – 2 – 1.

  8. Iron Fluorescent Line Emission from Black Hole Accretion Disks with Magnetic Reconnection-Heated Corona

    E-print Network

    N. Kawanaka; S. Mineshige; K. Iwasawa

    2005-08-24

    We investigate the iron K$\\alpha$ fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. The hot corona with temperature being about $10^9$K can irradiate the underlying disk with a continuum X-ray spectrum produced via thermal Comptonization. Then the iron atoms in the disk photoelectrically absorb X-ray photons and radiate K$\\alpha$ line photons. Therefore, the activity of corona is responsible to the iron line emission from the underlying disk. In previous studies, oversimplified X-ray photon sources are often assumed above the disk in order to compute the iron line profile or power-law line emissivity profiles are assumed with an index being a free parameter. We adopt the more realistic corona model constructed by Liu et al. in which the corona is heated by magnetic energy released through the reconnection of magnetic flux loops and which has no free parameter. Then the accretion energy is dominantly dissipated in the corona, in which X-ray photons are efficiently produced and irradiate the underlying disk. We find the local emmisivity of iron line on the disk is approximated as $F_{{\\rm K}\\alpha}(r)\\propto r^{-5}$. The iron line profiles derived from this model give excellent fits to the observational data of MCG-6-30-15 with the profiles derived theoretically for $i\\sim 30^{\\circ}$ for energy band 4-7keV. Possible origins of line variability are briefly discussed.

  9. Characteristics of Discharge in a DC Corona Reactor for Removing Dilute SF6

    NASA Astrophysics Data System (ADS)

    Minamitani, Yasushi; Sugimoto, Toshiyuki; Higashiyama, Yoshio

    A DC corona reactor using electron attachment is utilized to remove dilute fluorocarbon in an air-conditioning unit or SF6 in a gas circuit breaker. By employing helium gas to purge the low concentrated gas in the unit, corona onset voltage in the corona reactor decreases. We observed the characteristics of corona discharge for the pure helium gas with flow and for the helium gas contained dilute SF6 gas at atmospheric pressure. In pure helium gas, luminous spots appeared along the discharging wire. The number of luminous spots without gas flow increased stepwise with the discharging current. In contrast, the luminous spots decreased as the gas flow rate increased. In the helium gas containing dilute SF6, corona discharge occurred uniformly along the discharging wire initially. As the time elapsed, the discharge aspects drastically changed: The discharge voltage gradually decreased to that in the pure helium gas and the uniform corona discharge along the discharging wire changed to a single spot.

  10. Corona discharges and their effect on lightning attachment revisited: Upward leader initiation and downward leader interception

    NASA Astrophysics Data System (ADS)

    Becerra, Marley

    2014-11-01

    Previous studies have suggested the possibility of using glow corona discharges to control the frequency of lightning flashes to grounded objects. In order to revisit the theoretical basis of this proposal, the self-consistent leader inception and propagation model - SLIM - is used together with a two-dimensional glow corona drift model. The analysis is performed to quantify the effect of glow corona generated at the tip of ground-based objects on the initiation and propagation of upward positive connecting leaders under the influence of downward lightning leaders. It is found that the presence of glow corona does not influence the performance of Franklin lightning rods shorter than 15 m, while it slightly reduces the lateral distance of rods up to 60 m tall by a maximum of 10%. Furthermore, the results indicate that it is not possible to suppress the initiation of upward connecting leaders by means of glow corona. It is found instead that unconventional lightning protection systems based on the generation of glow corona attract downward lightning flashes in a similar way as a standard lightning rod with the same height.

  11. TOWARD A REALISTIC THERMODYNAMIC MAGNETOHYDRODYNAMIC MODEL OF THE GLOBAL SOLAR CORONA

    SciTech Connect

    Downs, Cooper; Roussev, Ilia I.; Lugaz, Noe [Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Van der Holst, Bart; Sokolov, Igor V.; Gombosi, Tamas I., E-mail: cdowns@ifa.hawaii.ed [Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States)

    2010-04-01

    In this work, we describe our implementation of a thermodynamic energy equation into the global corona model of the Space Weather Modeling Framework and its development into the new lower corona (LC) model. This work includes the integration of the additional energy transport terms of coronal heating, electron heat conduction, and optically thin radiative cooling into the governing magnetohydrodynamic (MHD) energy equation. We examine two different boundary conditions using this model; one set in the upper transition region (the radiative energy balance model), as well as a uniform chromospheric condition where the transition region can be modeled in its entirety. Via observation synthesis from model results and the subsequent comparison to full Sun extreme ultraviolet and soft X-ray observations of Carrington rotation 1913 centered on 1996 August 27, we demonstrate the need for these additional considerations when using global MHD models to describe the unique conditions in the low corona. Through multiple simulations, we examine the ability of the LC model to assess and discriminate between coronal heating models, and find that a relative simple empirical heating model is adequate in reproducing structures observed in the low corona. We show that the interplay between coronal heating and electron heat conduction provides significant feedback onto the three-dimensional magnetic topology in the low corona as compared to a potential field extrapolation, and that this feedback is largely dependent on the amount of mechanical energy introduced into the corona.

  12. Primary and secondary tip coronae from splashing water drops in electric fields

    NASA Astrophysics Data System (ADS)

    Kinsey, P. B.

    2012-06-01

    An enquiry has been carried out into millimetre size water drops falling through vertical electric fields, at terminal and near terminal velocities, and impacting a water surface. A laboratory method was devised to electronically observe the splashing event, together with the onset, duration and magnitude of all ensuing coronae. The production of a secondary jet tip and the discovery of a previously unknown corona were originally recorded by Kinsey (1986) and are here described in detail. Emanating from the secondary jet tip, the corona is synonymous with the release and electrification of an airborne water drop and its nC range of charge transfer (being field/momentum dependant) offer low level luminosity to the dark adapted eye (mentioned by ur Rahman and Saunders, 1988). For terminal and near terminal velocity drops, the resulting water jets follow under-damped sinusoidal oscillation and, in fields above a critical value (Ec), their primary tips often support more than one corona, thus yielding charge to the aerosol and space charge below oceanic thunderstorms. Secondary tip, or jet drop, corona data show the phenomenon to occur in fields of 100 V cm- 1 and maybe even lower. The role of such drops, in oceanic thunderstorm electrification, being subject to drop size, ambient field, updraft and wind shear speeds. Oscilloscopic and photographic evidence is presented in support of the discovered corona and oscillographs, photographs and data are taken from P. B. Kinsey Ph.D. thesis (1986).

  13. Study on earthed atomizing corona discharge enhancing the biodegradability of waste water from oil extraction

    NASA Astrophysics Data System (ADS)

    Du, S.; Xu, J.; Mi, J.; Li, N.

    2012-10-01

    This paper studies the usage of earthed atomizing corona discharge to dispose waste water from oil extraction. The I-V characteristic curves of earthed atomizing positive and negative corona discharge are compared to study the influence of water flux and inter-electrode distance (which refers to the distance between line electrode and plate electrodes) on discharge characteristics, and to measure the turbidity, pH, biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and the variation tendency of BOD5/COD in the process of dealing with waste water from oil extraction by earthed atomizing corona discharge. Ultimately, the mechanism of earthed atomizing corona discharge is analyzed. Research results indicate that when using earthed atomizing corona discharge to dispose of waste water from oil extraction, as the processing time grows there is a maximum value of turbidity, the pH level increases gradually then stabilizes, COD appears to descend, and BOD5 as well as BOD5/COD both have minimum values. When the processing time attains 300 min, waste water from oil extraction is suitable for biochemical treatment, foreshadowing that earthed atomizing corona discharge technology demonstrates energy conservation characteristic in improving the biodegradability of waste water from oil extraction and has a brilliant application prospect waiting ahead.

  14. Alfvénic waves with sufficient energy to power the quiet solar corona and fast solar wind.

    PubMed

    McIntosh, Scott W; De Pontieu, Bart; Carlsson, Mats; Hansteen, Viggo; Boerner, Paul; Goossens, Marcel

    2011-07-28

    Energy is required to heat the outer solar atmosphere to millions of degrees (refs 1, 2) and to accelerate the solar wind to hundreds of kilometres per second (refs 2-6). Alfvén waves (travelling oscillations of ions and magnetic field) have been invoked as a possible mechanism to transport magneto-convective energy upwards along the Sun's magnetic field lines into the corona. Previous observations of Alfvénic waves in the corona revealed amplitudes far too small (0.5?km?s(-1)) to supply the energy flux (100-200?W?m(-2)) required to drive the fast solar wind or balance the radiative losses of the quiet corona. Here we report observations of the transition region (between the chromosphere and the corona) and of the corona that reveal how Alfvénic motions permeate the dynamic and finely structured outer solar atmosphere. The ubiquitous outward-propagating Alfvénic motions observed have amplitudes of the order of 20?km?s(-1) and periods of the order of 100-500?s throughout the quiescent atmosphere (compatible with recent investigations), and are energetic enough to accelerate the fast solar wind and heat the quiet corona. PMID:21796206

  15. Properties of vertically self-gravitating accretion discs with a dissipative corona

    E-print Network

    Fazeleh Khajenabi; Peter Duffy

    2008-05-30

    The steady-state structure of a disc with a corona is analyzed when the vertical component of the gravitational force due to the self-gravity of the disc is considered. For the energy exchange between the disc and the corona, we assume a fraction f of the dissipated energy inside the accretion disc is transported to the corona via the magnetic tubes. Analytical solutions corresponding to a prescription for f (in which this parameter directly depends on the ratio of the gas pressure to the total pressure) or free f are presented and their physical properties are studied in detail. We show that the existence of the corona not only decreases the temperature of the disc, but also increases the surface density.The vertical component of the gravitational force due to the self-gravity of the disc decreases the self-gravitating radius and the mass of the fragments at this radius. However, as more energy is transported from the disc to the corona, the effect of the vertical component of the gravitational force due to the self-gravity of the disc on the self-gravitating radius becomes weaker, though the mass of the fragments is reduced irrespective of the amount of the energy exchange from the disc to the corona.

  16. The Corona of the Young Solar Analog EK Draconis

    NASA Technical Reports Server (NTRS)

    Gudel, M.; Schmitt, J. H. M. M.; Benz, A. O.; Elias, N. M., II

    1995-01-01

    First coronal microwave and new soft X-ray observations of the very active, near-Zero-Age Main-Sequence (ZAMS) dGOe star EK Dra = HD 129333 show that this analog of the young Sun is more luminous in both emissions than most single M-dwarf flare stars. Variations in the 8.4 GHz flux include modulation with the optically determined rotation period of 2.7 days. This result points to a non-uniform filling of the corona with energetic electrons due to an incomplete coverage of the surface with active regions and a source volume that is not concentric with the star. The radio luminosity varying between log L(sub R) = 13.6 and 14.6 (L(sub R) in erg/s/Hz) shows evidence for unpolarized gyrosynchrotron flares, while strongly polarized flares were absent during the observations. This star is the first young, truly solar-like main sequence G star discovered in microwaves. Having just arrived on the main sequence, it conclusively proves that young, solar-like G stars can maintain very high levels of radio emission after their T Tau phase. The X-ray observations were obtained from the ROSAT All-Sky Survey (RASS). The average X-ray luminosity amounts to log L(sub x) = 29.9 (L(sub x) in erg/s). A Raymond-Smith type plasma model fit yields two plasma components at temperatures of 1.9 and 10 MK, with volume emission measures of 1.2 and 2.5 x 10 (exp 52)/cu cm, respectively. The X-ray light curve is significantly variable, with the photon count rate from the cooler plasma being strongly modulated by the rotation period; the emission from the hotter plasma is only weakly variable. Modeling of the source distribution in the stellar corona yields electron densities of the order of 4 x 10(exp 10)/cu cm or higher for the cool plasma component. It indicates that a considerable portion of EK Dra's high X-ray luminosity is due to high-density plasma rather than large emission volume. Parameters for an X-ray flare indicate an electron density of 1.75 x 10(exp 11)/cu cm and a source height of (1-2) x 10(exp 10) cm, compatible with a few times the scale height of the cooler plasma component.

  17. The interaction of antibodies with lipid membranes unraveled by fluorescence methodologies

    NASA Astrophysics Data System (ADS)

    Figueira, Tiago N.; Veiga, Ana Salomé; Castanho, Miguel A. R. B.

    2014-12-01

    The interest and investment in antibody therapies has reached an overwhelming scale in the last decade. Yet, little concern has been noticed among the scientific community to unravel important interactions of antibodies with biological structures other than their respective epitopes. Lipid membranes are particularly relevant in this regard as they set the stage for protein-protein recognition, a concept potentially inclusive of antibody-antigen recognition. Fluorescence techniques allow experimental monitoring of protein partition between aqueous and lipid phases, deciphering events of adsorption, insertion and diffusion. This review focuses on the available fluorescence spectroscopy methodologies directed to the study of antibody-membrane interactions.

  18. Mining R Coronae Borealis stars from Catalina surveys

    NASA Astrophysics Data System (ADS)

    Lee, C.-H.

    2015-03-01

    Aims: R Coronae Borealis stars (RCBs) are rare carbon stars that lack of hydrogen in their photospheresand are most likely products of white dwarf mergers. A census of RCBs can shed light on the progenitors of SNe Ia in the context of a double degenerate scenario. Methods: Traditionally, RCBs are identified by their unpredictable photometric variation with dimmings up to 9 mag, and thus discoveries of RCBs are heavily biased to the limited regions monitored by long-term microlensing experiments. However, recent studies of galactic RCBs have shown that they exhibit distinct mid-infrared colors originating from their cool circumstellar shells, and the all-sky WISE survey facilitates the identification of RCB candidates. Therefore, combining the WISE colors with large area time-domain surveys will enable us to discover more RCBs. Results: This study presents the results of 26 RCB candidates from the Catalina surveys, where five of them are spectroscopically confirmed RCBs and seven of them are previously known carbon stars. This demonstrates the efficacy of this kind of an approach and the potential to discover uncharted RCBs in ongoing and future synoptic surveys.

  19. DC corona discharge ozone production enhanced by magnetic field

    NASA Astrophysics Data System (ADS)

    Pekárek, S.

    2010-01-01

    We have studied the effect of a stationary magnetic field on the production of ozone from air at atmospheric pressure by a negative corona discharge in a cylindrical electrode configuration. We used a stainless steel hollow needle placed at the axis of the cylindrical discharge chamber as a cathode. The outer wall of the cylinder was used as an anode. The vector of magnetic induction was perpendicular to the vector of current density. We found that: (a) the magnetic field extends the current voltage range of the discharge; (b) for the discharge in the Trichel pulses regime and in the pulseless glow regime, the magnetic field has no substantial effect on the discharge voltage or on the concentration of ozone that is produced; (c) for the discharge in the filamentary streamer regime for a particular current, the magnetic field increases the discharge voltage and consequently an approximately 30% higher ozone concentration can be obtained; (d) the magnetic field does not substantially increase the maximum ozone production yield. A major advantage of using a magnetic field is that the increase in ozone concentration produced by the discharge can be obtained without additional energy requirements.

  20. Dynamic properties of the solar corona: SOHO/LASCO observations

    NASA Astrophysics Data System (ADS)

    Mierla, M.; Schwenn, R.; Stenborg, G.; Teriaca, L.; Podlipnik, B.

    With the launch of the SOHO spacecraft in December 1995, the quality of corona observations has improved significantly. The LASCO instruments with their field of view now extending from 1.1 Rs (C1) to 30 Rs (C3) offer sufficient sensitivity to make an almost continuous outflow in the streamer belt visible. We report on two different approaches to study the plasma motion, both in the plane of the sky and along the line of sight. 1. By means of a multi-resolution image processing technique based on wavelet packets the boundaries and the internal details of originally faint and diffuse structures are enhanced. This approach allows unambiguous image interpretation and provides a means for the quantification of stationary and dynamic coronal structures required for conducting morphological studies. 2. The LASCO/C1 telescope was designed to perform spectral analysis on coronal structures. The tunable Fabry-Perot interferometer allows to obtain images at different wavelengths. Results from spectral scans of the coronal green and red emission lines are presented. From the line profiles physical quantities like temperatures (from line widths), and flow velocities (from Doppler shifts) along the line of sight are deduced.

  1. Force-Free Magnetic Flux Ropes in the Solar Corona

    NASA Astrophysics Data System (ADS)

    Wolfson, R.

    2003-05-01

    In the course of an ongoing investigation of force-free magnetic fields in the spherical geometry appropriate to the solar corona, we have found solutions that represent magnetic flux ropes. The magnetic energy stored in these ropes and the surrounding field is larger than that which can be stored in simple magnetic arcades with the same boundary conditions, and in some cases exceeds slightly the Aly-Sturrock limit on the energy of a closed force-free magnetic field with all its magnetic flux connected to the coronal base. Flux-rope solutions with the highest energies tend to arise when a strong potential field overlies a region of sheared field containing field-aligned currents. These flux-rope solutions have an unusual topology; instead of a single twisted, disconnected flux system, there are two distinct rope structures. A two-dimensional slice through each rope contains an O-type magnetic neutral point, and the overall solution therefore correspondingly contains two X-type neutral points. We speculate on the relation of this unusual topology to observations of magnetic clouds as interplanetary signatures of coronal mass ejections. This work was supported by NASA grant NAG5-9733 to Middlebury College.

  2. Coronae of Stars with Super Solar Elemental Abundances

    E-print Network

    Peretz, Uria; Drake, Stephen A

    2015-01-01

    Coronal elemental abundances are known to deviate from the photospheric values of their parent star, with the degree of deviation depending on the First Ionization Potential (FIP). This study focuses on the coronal composition of stars with super-solar photospheric abundances. We present the coronal abundances of six such stars: 11 LMi, $\\iota$ Hor, HR 7291, $\\tau$ Boo, and $\\alpha$ Cen A and B. These stars all have high-statistics X-ray spectra, three of which are presented for the first time. The abundances measured in this paper are obtained using the line-resolved spectra of the Reflection Grating Spectrometer (RGS) in conjunction with the higher throughput EPIC-pn camera spectra on board the XMM-Newton observatory. A collisionally ionized plasma model with two or three temperature components is found to represent the spectra well. All elements are found to be consistently depleted in the coronae compared to their respective photospheres. For 11 LMi and $\\tau$ Boo no FIP effect is present, while $\\iota$ H...

  3. Solar cycle 24 in Photosphere, Chromosphere and Corona.

    NASA Astrophysics Data System (ADS)

    Benevolenskaya, Elena

    The solar cycle 24 shows an interesting behavior and it is a subject of current discussions. Comparison this cycle with previous ones displays relatively small activity which may be a consequence of the interaction of the long-tem variations of the solar activity and sunspot solar cycle. For example, the Solar Dynamics Observatory (SDO) provides us with multi-waves imagery from Extreme Ultraviolet (EUV) to visible light as well as magnetic field measurements. These data give us an opportunity to study the nature of solar activity in different regions of the Sun, from the interior to the corona. For solar cycle studies synoptic maps provide a useful way to represent global activity and evolution by extracting a central meridian band from sequences of full disk images over a full solar Carrington rotation (~ 27.3 days). Here, present the global evolution of solar cycle 24 from May 20, 2010 to up the present, using synoptic maps constructed from full disk line-of sight magnetic field imagery (HMI/SDO) and EUV imagery (171Å, 193Å, 211Å, 304Å and 335Å (AIA/SDO). The synoptic maps have a resolution of 0.1 degree in longitude and steps of 0.001 in sine of latitude. From the 'time-latitude' images we observe that during the ascending phase of cycle 24 a very strong North-South asymmetry of topology of emerging magnetic flux develops, resulting in a consequential asymmetry in the timing of the polar magnetic field reversals.

  4. How Many R Coronae Borealis Stars Are There Really? (Abstract)

    NASA Astrophysics Data System (ADS)

    Clayton, G. C.

    2014-12-01

    (Abstract only) The R Coronae Borealis (RCB) stars are rare hydrogen-deficient, carbon-rich supergiants. Two evolutionary scenarios have been suggested, a double degenerate merger of two white dwrfs (WDs), or a final helium shell flash in a planetary nebula central star. Only about 100 of the predicted 3,000 RCB stars in the Galaxy have been discovered. But the pace of discovery of new RCB stars in the Milky Way has been accelerating. We recently discovered over twenty new RCB stars by examining ASAS-e light curves. Using the recent release of the WISE All-Sky Catalog, a series of IR color-color cuts have produced a sample of candidates that may yield over 200 new RCB stars. We are trying to obtain spectra of these stars to confirm their identifications. The evidence pointing toward a WD merger or a final-flash origin for RCB stars is contradictory. Increasing the sample of known RCB stars, so that we can better study their spatial distribution in the Galaxy, can give us clues to their origins. Their number and distribution may be consistent with WD mergers. If so, this would be an exciting result since RCB stars may be low-mass analogs of Type Ia supernovae.

  5. Results of solar observations by the CORONAS-F payload

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. D.; Sobelman, I. I.; Zhitnik, I. A.; Kuzin, S. V.; Kotov, Yu. D.; Charikov, Yu. E.; Kuznetsov, S. N.; Mazets, E. P.; Nusinov, A. A.; Pankov, A. M.; Sylwester, J.

    2011-05-01

    The CORONAS-F mission experiments and results have been reviewed. The observations with the DIFOS multi-channel photometer in a broad spectral range from 350 to 1500 nm have revealed the dependence of the relative amplitudes of p-modes of the global solar oscillations on the wavelength that agrees perfectly well with the earlier data obtained in a narrower spectral ranges. The SPIRIT EUV observations have enabled the study of various manifestations of solar activity and high-temperature events on the Sun. The data from the X-ray spectrometer RESIK, gamma spectrometer HELICON, flare spectrometer IRIS, amplitude-temporal spectrometer AVS-F, and X-ray spectrometer RPS-1 have been used to analyze the X- and gamma-ray emission from solar flares and for diagnostics of the flaring plasma. The absolute and relative content of various elements (such as potassium, argon, and sulfur) of solar plasma in flares has been determined for the first time with the X-ray spectrometer RESIK. The Solar Cosmic Ray Complex monitored the solar flare effects in the Earth's environment. The UV emission variations recorded during solar flares in the vicinity of the 120-nm wavelength have been analyzed and the amplitude of relative variations has been determined.

  6. Peptide Fragmentation by Corona Discharge Induced Electrochemical Ionization

    PubMed Central

    Lloyd, John R.; Hess, Sonja

    2010-01-01

    Fundamental studies have greatly improved our understanding of electrospray, including the underlying electrochemical reactions. Generally regarded as disadvantageous, we have recently shown that corona discharge (CD) can be used as an effective method to create a radical cation species [M]+•, thus optimizing the electrochemical reactions that occur on the surface of the stainless steel (SS) electrospray capillary tip. This technique is known as CD initiated electrochemical ionization (CD-ECI). Here, we report on the fundamental studies using CD-ECI to induce analytically useful in-source fragmentation of a range of molecules that complex transition metals. Compounds that have been selectively fragmented using CD-ECI include enolate forming phenylglycine containing peptides, glycopeptides, nucleosides and phosphopeptides. Collision induced dissociation (CID) or other activation techniques were not necessary for CD-ECI fragmentation. A four step mechanism was proposed: 1. Complexation using either Fe in the SS capillary tip material or Cu(II) as an offline complexation reagent; 2. Electrochemical oxidation of the complexed metal and thus formation of a radical cation (e.g.; Fe - e? ? Fe +•); 3. Radical fragmentation of the complexed compound. 4. Electrospray ionization of the fragmented neutrals. Fragmentation patterns resembling b- and y-type ions were observed and allowed the localization of the phosphorylation sites. PMID:20869880

  7. Plasma Chemistry and Plasma Processing, Vol. 23, No. 1, March 2003 ( 2003) Model of the Negative DC Corona Plasma

    E-print Network

    Chen, Junhong

    Plasma Chemistry and Plasma Processing, Vol. 23, No. 1, March 2003 ( 2003) Model of the Negative DC Corona Plasma: Comparison to the Positive DC Corona Plasma Junhong Chen1 and Jane H. Davidson1,2 Receiûed March 26, 2002, reûised June 14, 2002 A numerical model of the negatiûe DC corona plasma along a thin

  8. Using an optical fibre anemometer to measure the speed of the electric wind in a negative polarity, atmospheric corona discharge

    Microsoft Academic Search

    A. Hooper; D. W. Lamb

    2005-01-01

    Coronas are partial discharges that occur in regions of non-uniform electric fields adjacent to conductors stressed to high voltages. Negative, Trichel-pulse coronas in air occur when a dc, negative-polarity, high voltage is applied to a conductor. Trichel pulses in atmospheric air generate significant amounts of ozone as well as electrical and acoustic noise. Under the right conditions these coronas can

  9. Use of a Multichannel Analyzer for Corona Pulse-Height Distribution Measurements on Cables and Other Electrical Apparatus

    Microsoft Academic Search

    R. Bartnikas

    1973-01-01

    A method in which use is made of a multichannel analyzer to measure the distribution of the corona pulse heights of insulating systems of various electrical apparatus such as transformers, capacitors, and cables is described. Suitable pulse-shaping circuitry is used in conjunction with an RCL-type corona pulse detector to provide a basic sensitivity level of 1 pC and corona pulse

  10. Numerical modelling of ozone production in a wire-cylinder corona discharge and comparison with a wire-plate corona discharge

    NASA Astrophysics Data System (ADS)

    Wang, Pengxiang; Chen, Junhong

    2009-02-01

    The effect of electrode configuration on ozone production in the direct-current corona discharge of dry and humid air is studied by a numerical model that combines the electron distribution in the corona plasma, plasma chemistry and transport phenomena. Two electrode configurations are considered: wire-cylinder discharge with air flowing along the wire axis and wire-plate discharge with air flowing transverse to the wire. The ozone distributions in both types of discharges are compared. For both electrode configurations, the ozone production rate is higher in the negative corona than in the positive corona and it decreases with an increase in relative humidity. More importantly, the detailed ozone distribution in the neighbourhood of the discharge wire, together with the ozone kinetics, reveals the possible difference in the ozone production from the two discharges. With the same operating conditions and sufficiently short flow residence time, the ozone production rate is nearly the same for both electrode configurations. When the flow residence time is longer than the characteristic time for homogeneous ozone destruction, the net ozone production is higher in the wire-cylinder discharge than in the wire-plate discharge due to relatively less ozone destruction.

  11. The fate of a designed protein corona on nanoparticles in vitro and in vivo.

    PubMed

    Bargheer, Denise; Nielsen, Julius; Gébel, Gabriella; Heine, Markus; Salmen, Sunhild C; Stauber, Roland; Weller, Horst; Heeren, Joerg; Nielsen, Peter

    2015-01-01

    A variety of monodisperse superparamagnetic iron oxide particles (SPIOs) was designed in which the surface was modified by PEGylation with mono- or bifunctional poly(ethylene oxide)amines (PEG). Using (125)I-labeled test proteins (transferrin, albumin), the binding and exchange of corona proteins was studied first in vitro. Incubation with (125)I-transferrin showed that with increasing grade of PEGylation the binding was substantially diminished without a difference between simply adsorbed and covalently bound protein. However, after incubation with excess albumin and subsequently whole plasma, transferrin from the preformed transferrin corona was more and more lost from SPIOs in the case of adsorbed proteins. If non-labeled transferrin was used as preformed corona and excess (125)I-labeled albumin was added to the reaction mixtures with different SPIOs, a substantial amount of label was bound to the particles with initially adsorbed transferrin but little or even zero with covalently bound transferrin. These in vitro experiments show a clear difference in the stability of a preformed hard corona with adsorbed or covalently bound protein. This difference seems, however, to be of minor importance in vivo when polymer-coated (59)Fe-SPIOs with adsorbed or covalently bound (125)I-labeled mouse transferrin were injected intravenously in mice. With both protein coronae the (59)Fe/(125)I-labelled particles were cleared from the blood stream within 30 min and appeared in the liver and spleen to a large extent (>90%). In addition, after 2 h already half of the (125)I-labeled transferrin from both nanodevices was recycled back into the plasma and into tissue. This study confirms that adsorbed transferrin from a preformed protein corona is efficiently taken up by cells. It is also highlighted that a radiolabelling technique described in this study may be of value to investigate the role of protein corona formation in vivo for the respective nanoparticle uptake. PMID:25671150

  12. The Soft X-Ray/Microwave Ratio of Solar and Stellar Flares and Coronae

    NASA Technical Reports Server (NTRS)

    Benz, A. O.; Guedel, M.

    1994-01-01

    We have carried out plasma diagnostics of solar flares using soft X-ray (SXR) and simultaneous microwave observations and have compared the ratio of X-ray to microwave luminosities of solar flares with various active late-type stars available in the published literature. Both the SXR low-level ('quiescent') emission from stellar coronae and the flaring emission from the Sun and stars are generally interpreted as thermal radiations of coronal plasmas. On the other hand, the microwave emission of stars and solar flares is generally attributed to an extremely hot or nonthermal population of electrons. Solar flare SXR are conventionally measured in a narrower and harder passband than the stellar sources. Observations of the GOES-2 satellite in two energy channels have been used to estimate the luminosity of solar flares as it would appear in the ROSAT satellite passband. The solar and stellar flare luminosities fit well at the lower end of the active stellar coronae. The flare SXR/microwave ratio is similar to the ratio for stellar coronae. The average ratio follows a power-law relation L(sub X) varies as L(sub R)(sup 0.73 +/- 0.03) over 10 orders of magnitude from solar microflares to RS CVn and FK Com-type coronae. Dwarf Me and Ke stars, and RS CVn stars are also compatible with a linear SXR/microwave relation, but the ratio is slightly different for each type of star. Considering the differences between solar flares, stellar flares and the various active stellar coronae, the similarity of the SXR/microwave ratios is surprising. It suggests that the energetic electrons in low-level stellar coronae observed in microwaves are related in a similar way to the coronal thermal plasma as flare electrons to the flare thermal plasma, and, consequently, that the heating mechanism of active stellar coronae is a flare-like process.

  13. The fate of a designed protein corona on nanoparticles in vitro and in vivo

    PubMed Central

    Bargheer, Denise; Nielsen, Julius; Gébel, Gabriella; Heine, Markus; Salmen, Sunhild C; Stauber, Roland; Weller, Horst; Heeren, Joerg

    2015-01-01

    Summary A variety of monodisperse superparamagnetic iron oxide particles (SPIOs) was designed in which the surface was modified by PEGylation with mono- or bifunctional poly(ethylene oxide)amines (PEG). Using 125I-labeled test proteins (transferrin, albumin), the binding and exchange of corona proteins was studied first in vitro. Incubation with 125I-transferrin showed that with increasing grade of PEGylation the binding was substantially diminished without a difference between simply adsorbed and covalently bound protein. However, after incubation with excess albumin and subsequently whole plasma, transferrin from the preformed transferrin corona was more and more lost from SPIOs in the case of adsorbed proteins. If non-labeled transferrin was used as preformed corona and excess 125I-labeled albumin was added to the reaction mixtures with different SPIOs, a substantial amount of label was bound to the particles with initially adsorbed transferrin but little or even zero with covalently bound transferrin. These in vitro experiments show a clear difference in the stability of a preformed hard corona with adsorbed or covalently bound protein. This difference seems, however, to be of minor importance in vivo when polymer-coated 59Fe-SPIOs with adsorbed or covalently bound 125I-labeled mouse transferrin were injected intravenously in mice. With both protein coronae the 59Fe/125I-labelled particles were cleared from the blood stream within 30 min and appeared in the liver and spleen to a large extent (>90%). In addition, after 2 h already half of the 125I-labeled transferrin from both nanodevices was recycled back into the plasma and into tissue. This study confirms that adsorbed transferrin from a preformed protein corona is efficiently taken up by cells. It is also highlighted that a radiolabelling technique described in this study may be of value to investigate the role of protein corona formation in vivo for the respective nanoparticle uptake. PMID:25671150

  14. Link between the chromospheric network and magnetic structures of the corona

    NASA Astrophysics Data System (ADS)

    Jendersie, S.; Peter, H.

    2006-12-01

    Context: . Recent work suggested that the traditional picture of the corona above the quiet Sun being rooted in the magnetic concentrations of the chromospheric network alone is strongly questionable. Aims: . Building on that previous study we explore the impact of magnetic configurations in the photosphere and the low corona on the magnetic connectivity from the network to the corona. Observational studies of this connectivity are often utilizing magnetic field extrapolations. However, it is open to which extent such extrapolations really represent the connectivity found on the Sun, as observations are not able to resolve all fine scale magnetic structures. The present numerical experiments aim at contributing to this question. Methods: . We investigated random salt-and-pepper-type distributions of kilo-Gauss internetwork flux elements carrying some 1015 to 1017 Mx, which are hardly distinguishable by current observational techniques. These photospheric distributions are then extrapolated into the corona using different sets of boundary conditions at the bottom and the top. This allows us to investigate the fraction of network flux which is connected to the corona, as well as the locations of those coronal regions which are connected to the network patches. Results: . We find that with current instrumentation one cannot really determine from observations, which regions on the quiet Sun surface, i.e. in the network and internetwork, are connected to which parts of the corona through extrapolation techniques. Future spectro-polarimetric instruments, such as with Solar B or Gregor, will provide a higher sensitivity, and studies like the present one could help to estimate to which extent one can then pinpoint the connection from the chromosphere to the corona. Conclusions: .

  15. On the Heating of the Solar Corona and the Acceleration of the Low-Speed Solar Wind by Acoustic Waves Generated in Corona

    E-print Network

    Takeru Ken Suzuki

    2002-08-06

    We investigate possibilities of solar coronal heating by acoustic waves generated not at the photosphere but in the corona, aiming at heating in the mid- to low-latitude corona where the low-speed wind is expected to come from. Acoustic waves of period tau ~ 100s are triggered by chromospheric reconnection, one model of small scale magnetic reconnection events recently proposed by Sturrock. These waves having a finite amplitude eventually form shocks to shape sawtooth waves (N-waves), and directly heat the surrounding corona by dissipation of their wave energy. Outward propagation of the N-waves is treated based on the weak shock theory, so that the heating rate can be evaluated consistently with physical properties of the background coronal plasma without setting a dissipation length in an ad hoc manner. We construct coronal structures from the upper chromosphere to the outside of 1AU for various inputs of the acoustic waves having a range of energy flux of F_{w,0} = (1-20) times 10^5 erg cm^{-2} s^{-1} and a period of tau = 60-300s. The heating by the N-wave dissipation effectively works in the inner corona and we find that the waves of F_{w,0} >= 2 times 10^5 erg cm^{-2} s^{-1} and tau >= 60s could maintain peak coronal temperature, T_{max} > 10^6 K. The model could also reproduce the density profile observed in the streamer region. However, due to its short dissipation length, the location of T_{max} is closer to the surface than the observation, and the resultant flow velocity of the solar wind is lower than the observed profile of the low-speed wind. The cooperations with other heating and acceleration sources with the larger dissipation length are inevitable to reproduce the real solar corona.

  16. Multi-wavelength Analysis to Solar Corona Heating Events

    NASA Astrophysics Data System (ADS)

    Yang, X.; Ji, H. S.; Li, H. C.

    2014-05-01

    With the advent and successful running of the 1.6 meter aperture New Solar Telescope at Big Bear Solar Observatory (BBSO/NST), solar observation has entered the era of 0.1 arc second. This permits us to carry out case studies for single coronal heating event, accumulating original high-resolution observational evidences for a final resolving of the coronal heating problem. By combining the high-resolution Helium I 10830 Å, TiO 7057 Å, and H_? - 0.7 Å imaging data from NST, and the satellite data from the Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO), we analyze the evolution of magnetic field in the roots of two tiny dynamical events originating from the Sun's intergranular lanes as seen from Helium I 10830 Å images. The two events caused subsequent brightening in the corona, but no obvious feature is found at H_? -0.7 Å images. We find that the two events are rooted at one side of magnetic polarity inversion line. One event is apparently accompanied by the disappearance of a tiny magnetic element, while, in another event, weakening of a magnetic concentration area is found. Changes for granules are also found during the two events. The results suggest that the two heating events are caused by small-scale magnetic activities in intergranular lanes driven by constant granule convection. It appears that ubiquitous small-scale magnetic activities produce outflow of cold matter as seen at 10830 Å and hot matter as seen at extreme ultraviolet bands.

  17. CHARACTERIZING TRANSITION TEMPERATURE GAS IN THE GALACTIC CORONA

    SciTech Connect

    Wakker, Bart P.; Savage, Blair D. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Fox, Andrew J. [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago (Chile); Benjamin, Robert A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218 (United States); Shapiro, Paul R., E-mail: wakker@astro.wisc.edu, E-mail: savage@astro.wisc.edu, E-mail: afox@stsci.edu, E-mail: benjamir@uww.edu, E-mail: shapiro@astro.as.utexas.edu [University of Texas at Austin, Department of Astronomy, Austin, TX 78712 (United States)

    2012-04-20

    We present a study of the properties of the transition temperature (T {approx} 10{sup 5} K) gas in the Milky Way corona, based on the measurements of O VI, N V, C IV, Si IV, and Fe III absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60 km s{sup -1}. On average the integrated column densities are log N(O VI) = 14.3, log N(N V) = 13.5, log N(C IV) = 14.2, log N(Si IV) = 13.6, and log N(Fe III) = 14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor {approx}2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions. We compare the column densities and ionic ratios to a series of theoretical predictions: collisional ionization equilibrium, shock ionization, conductive interfaces, turbulent mixing, thick disk supernovae, static non-equilibrium ionization (NIE) radiative cooling, and an NIE radiative cooling model in which the gas flows through the cooling zone. None of these models can fully reproduce the data, but it is clear that NIE radiative cooling is important in generating the transition temperature gas.

  18. The Writhe of Helical Structures in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Toeroek, T.; Berger, M. A.; Kliem, B.

    2010-01-01

    Context. Helicity is a fundamental property of magnetic fields, conserved in ideal MHD. In flux rope topology, it consists of twist and writhe helicity. Despite the common occurrence of helical structures in the solar atmosphere, little is known about how their shape relates to the writhe, which fraction of helicity is contained in writhe, and how much helicity is exchanged between twist and writhe when they erupt. Aims. Here we perform a quantitative investigation of these questions relevant for coronal flux ropes. Methods. The decomposition of the writhe of a curve into local and nonlocal components greatly facilitates its computation. We use it to study the relation between writhe and projected S shape of helical curves and to measure writhe and twist in numerical simulations of flux rope instabilities. The results are discussed with regard to filament eruptions and coronal mass ejections (CMEs). Results. (1) We demonstrate that the relation between writhe and projected S shape is not unique in principle, but that the ambiguity does not affect low-lying structures, thus supporting the established empirical rule which associates stable forward (reverse) S shaped structures low in the corona with positive (negative) helicity. (2) Kink-unstable erupting flux ropes are found to transform a far smaller fraction of their twist helicity into writhe helicity than often assumed. (3) Confined flux rope eruptions tend to show stronger writhe at low heights than ejective eruptions (CMEs). This argues against suggestions that the writhing facilitates the rise of the rope through the overlying field. (4) Erupting filaments which are S shaped already before the eruption and keep the sign of their axis writhe (which is expected if field of one chirality dominates the source volume of the eruption), must reverse their S shape in the course of the rise. Implications for the occurrence of the helical kink instability in such events are discussed.

  19. Unravelling DNA

    NASA Astrophysics Data System (ADS)

    Conroy, Rs; Danilowicz, C.

    2004-04-01

    The forces involved in the biology of life are carefully balanced between stopping thermal fluctuations ripping our DNA apart and having bonds weak enough to allow enzymes to function. The application of recently developed techniques for measuring piconewton forces and imaging at the nanometre scale on a molecule-by-molecule basis has dramatically increased the impact of single-molecule biophysics. This article describes the most commonly used techniques for imaging and manipulating single biomolecules. Using these techniques, the mechanical properties of DNA can be investigated, for example through measurements of the forces required to stretch and unzip the DNA double helix. These properties determine the ease with which DNA can be folded into the cell nucleus and the size and complexity of the accompanying cellular machinery. Part of this cellular machinery is enzymes, which manipulate, repair and transcribe the DNA helix. Enzymatic function is increasingly being investigated at the single molecule level to give better understanding of the forces and processes involved in the genetic cycle. One of the challenges is to transfer this understanding of single molecules into living systems. Already there have been some notable successes, such as the development of techniques for gene expression through the application of mechanical forces to cells, and the imaging and control of viral infection of a cell. This understanding and control of DNA has also been used to design molecules, which can self-assemble into a range of structures.

  20. Unraveling Traveling

    NSDL National Science Digital Library

    Charalambos Kyriacou (University of Leicester; )

    2009-09-25

    Access to the article is free, however registration and sign-in are required. There are few more awesome sights in the animal world than the seasonal mass migrations of the monarch butterfly, Danaus plexippus, from the northern United States and southern Canada to its overwintering grounds in central Mexico. As with other insect orientations, the monarch uses the position of the Sun to calculate where it should be going. However, as the Sun moves across the sky during the day, the monarch must continuously adjust its calculations, which it does by using its 24-hour circadian clock. So where is this time-compensated clock located? Merlin et al. reveal that it's in the antennae.