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Sample records for magnetic sector boundary

  1. The heliospheric sector boundary as a distented magnetic cloud

    NASA Technical Reports Server (NTRS)

    Crooker, N. U.; Intriligator, D. S.

    1995-01-01

    A magnetic cloud was detected both near Earth and by Pioneer 11 located 43 deg east of Earth at 4.8 AU. The magnetic field within the cloud rotated smoothly from toward to away polarity, marking sector boundary passage. Interpreted as a flux rope, the cloud had a vertical axis, implying that its cylindrical cross-section in the ecliptic plane was distended along the sector boundary by at least 43, forming an extensive occlusion in the heliospheric current sheet. At 1 AU the cloud had plasma signatures typical of a fast coronal mass ejection with low temperature and a leading shock. In contrast, at 4.8 AU, only the cloud signature remained. Its radial dimension was the same at both locations, consistent with little expansion beyond 1 AU. Energetic particle data at 4.8 AU show high fluxes preceding the cloud but not extending forward to the corotating shock that marked entry into the interaction region containing the cloud. The streaming direction was antisunward, consistent with possible acceleration in a low-beta region of field line draping around the cloud's western (upstream) end. The fluxes dropped upon entry into the cloud and became essentially isotropic one third of the way through it. On the basis of sector boundary characteristics published in the past, we suggest that distended clouds may be common heliospheric current sheet occlusions.

  2. The sun's magnetic sector structure

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.; Wilcox, J. M.; Scherrer, P. H.; Howard, R.

    1975-01-01

    The synoptic appearance of solar magnetic sectors is studied using 454 sector boundaries observed at earth during 1959-1973. The sectors are clearly visible in the photospheric magnetic field. Sector boundaries can be clearly identified as north-south running demarcation lines between regions of persistent magnetic polarity imbalances. These regions extend up to about 35 deg of latitude on both sides of the equator. They generally do not extend into the polar caps. The polar cap boundary can be identified as an east-west demarcation line marking the poleward limit of the sectors. The typical flux imbalance for a magnetic sector is about 4 x 10 to the 21st power Maxwells.

  3. Interplanetary sector boundaries, 1971 - 1973

    NASA Technical Reports Server (NTRS)

    Klein, L.; Burlaga, L. F.

    1979-01-01

    Eighteen interplanetary sector boundary crossings observed at 1 AU by the magnetometer on the IMP-6 spacecraft are discussed. The events were examined on many different time scales ranging from days on either side of the boundary to high resolution measurements of 12.5 vectors per second. Two categories of boundaries were found, one group being relatively thin and the other being thick. In many cases the field vector rotated in a plane from one polarity to the other. Only two of the transitions were null sheets. Using the minimum variance analysis to determine the normals to the plane of rotation, and assuming that this is the same as the normal to the sector boundary surface, it was found that the normals were close to the ecliptic plane. An analysis of tangential discontinuities contained in 4-day periods about the events showed that their orientations were generally not related to the orientations of the sector boundary surface, but rather their characteristics were about the same as those for discontinuities outside the sector boundaries.

  4. The interplanetary and solar magnetic field sector structures, 1962 - 1968

    NASA Technical Reports Server (NTRS)

    Jones, D. E.

    1972-01-01

    The interplanetary magnetic field sector structure was observed from late 1962 through 1968. During this time it has been possible to study the manner in which the sector pattern and its relation to the photospheric magnetic field configuration changes from solar minimum to solar maximum. Observations were also made relating sector boundaries to specific regions on the solar disk. These and other observations related to the solar origin of the interplanetary field are briefly reviewed.

  5. The shape and location of the sector boundary surface in the inner solar system. [Helios observations

    NASA Technical Reports Server (NTRS)

    Villante, U.; Bruno, R.; Mariani, F.; Burlaga, L. F.; Ness, N. F.

    1979-01-01

    Simultaneous observations by Helios-1 and Helios-2 over four solar rotations were used to determine the latitudinal dependence of the polarity of the interplanetary magnetic field within plus or minus 7.23 deg of the solar equator and within 1 AU. The longitudinal and latitudinal positions of the sector boundary crossing are consistent with a warped sector boundary which extended from the sun to 1 AU and was inclined approximately 10 deg with respect to the heliographic equator. This is consistent with simultaneous Pioneer 11 observations, which showed unipolar fields at latitude approximately 16 deg at heliocentric distances greater than 3.5 AU. Two sectors were observed at southern latitudes; however, four sectors were observed at northern latitudes on two rotations, indicating a distortion from planarity of the sectory boundary surface.

  6. Effect of Dynamic Sector Boundary Changes on Air Traffic Controllers

    NASA Technical Reports Server (NTRS)

    Jung, Jaewoo; Lee, Paul; Kessell, Angela; Homola, Jeff; Zelinski, Shannon

    2010-01-01

    The effect of dynamic sector boundary changes on air traffic controller workload was investigated with data from a human-in-the-loop simulation. Multiple boundary changes were made during simulated operations, and controller rating of workload was recorded. Analysis of these data showed an increase of 16.9% in controller workload due to boundary changes. This increased workload was correlated with the number of aircraft handoffs and change in sector volume. There was also a 12.7% increase in average workload due to the changed sector design after boundary changes. This increase was correlated to traffic flow crossing points getting closer to sector boundaries and an increase in the number of flights with short dwell time in a sector. This study has identified some of the factors that affect controller workload when sector boundaries are changed, but more research is needed to better understand their relationships.

  7. Structure of the photospheric magnetic field during sector crossings of the heliospheric magnetic field

    NASA Astrophysics Data System (ADS)

    Getachew, Tibebu; Virtanen, Ilpo; Mursula, Kalevi

    2017-04-01

    The photospheric magnetic field is the source of the coronal and heliospheric magnetic fields (HMF), but their mutual correspondence is non-trivial and depends on the phase of the solar cycle. The photospheric field during the HMF sector crossings observed at 1 AU has been found to contain enhanced field intensities and definite polarity ordering, forming regions called Hale boundaries. Here we study the structure of the photospheric field during the HMF sector crossings during solar cycles 21-24, separately for the four phases of each solar cycle. We use a refined version of Svalgaard's list of major HMF sector crossings, mapped to the Sun using the solar wind speed observed at the Earth, and the daily level-3 magnetograms of the photospheric field measured at the Wilcox Solar Observatory in 1976-2014. We find that the structure of the photospheric field corresponding to the HMF sector crossings, and the existence and properties of the corresponding Hale bipolar regions varies significantly with solar cycle and with solar cycle phase. We find evidence for Hale boundaries in many, but not all ascending, maximum and declining phases of solar cycles but no minimum phase. The most clear Hale boundaries are found during the (+,-) HMF crossings in the northern hemisphere of odd cycles 21 and 23, but less systematically during the (+,-) crossings in the southern hemisphere of even cycles 22 and 24. We also find that the Hale structure of cycles 23 and 24 is more systematic than during cycles 21 and 22. This may be due to the weakening activity, which reduces the complexity of the photospheric field and clarifies the Hale pattern. The photospheric field distribution also depicts a larger area for the field of the northern hemisphere during the declining and minimum phases, in a good agreement with the bashful ballerina phenomenon. The HMF sector crossings observed at 1AU have only a partial correspondence to Hale boundaries in the photosphere, indicating that the two HMF

  8. Temperature compensation for miniaturized magnetic sector

    NASA Technical Reports Server (NTRS)

    Sinha, Mahadeva P. (Inventor)

    2002-01-01

    Temperature compensation for a magnetic sector used in mass spectrometry. A high temperature dependant magnetic sector is used. This magnetic sector is compensated by a magnetic shunt that has opposite temperature characteristics to those of the magnet.

  9. Structure of the Photospheric Magnetic Field During Sector Crossings of the Heliospheric Magnetic Field

    NASA Astrophysics Data System (ADS)

    Getachew, Tibebu; Virtanen, Ilpo; Mursula, Kalevi

    2017-11-01

    The photospheric magnetic field is the source of the coronal and heliospheric magnetic fields (HMF), but their mutual correspondence is non-trivial and depends on the phase of the solar cycle. The photospheric field during the HMF sector crossings observed at 1 AU has been found to contain enhanced field intensities and definite polarity ordering, forming regions called Hale boundaries. Here we separately study the structure of the photospheric field during the HMF sector crossings during Solar Cycles 21 - 24 for the four phases of each solar cycle. We use a refined version of Svalgaard's list of major HMF sector crossings, mapped to the Sun using the solar wind speed observed at Earth, and the daily level-3 magnetograms of the photospheric field measured at the Wilcox Solar Observatory in 1976 - 2016. We find that the structure of the photospheric field corresponding to the HMF sector crossings and the existence and properties of the corresponding Hale bipolar regions varies significantly with solar cycle, solar cycle phase, and hemisphere. The Hale boundaries in more than half of the ascending, maximum, and declining phases are clear and statistically significant. The clearest Hale boundaries are found during the (+,-) HMF crossings in the northern hemisphere of odd Cycles 21 and 23, but less systematical during the (+,-) crossings in the southern hemisphere of even Cycles 22 and 24. No similar difference between odd and even cycles is found for the (-,+) crossings. This shows that the northern hemisphere has a more organized Hale pattern overall. The photospheric field distribution also depicts a larger area for the field of the northern hemisphere during the declining and minimum phases, in a good agreement with the bashful ballerina phenomenon.

  10. Is the Magnetic Field in the Heliosheath Sector Region and in the Outer Heliosheath Laminar?

    NASA Astrophysics Data System (ADS)

    Opher, M.; Drake, J. F.; Swisdak, M. M.; Toth, G.

    2010-12-01

    All the current global models of the heliosphere are based on the assumption that the magnetic field in the outer heliosheath close to the heliopause is laminar. We argue that in the outer heliosheath the heliospheric magnetic field is not laminar but instead consists of nested magnetic islands. Recently, we proposed (Drake et al. 2009) that the annihilation of the ``sectored'' magnetic field within the heliosheath as it is compressed on its approach to the heliopause produces the anomalous cosmic rays (ACRs) and also energetic electrons. As a product of the annihilation of the sectored magnetic field, densly-packed magnetic islands are produced. These magnetic islands will be convected with the ambient flows as the sector boundary is carried to higher latitudes filling the outer heliosheath. We further argue that the magnetic islands will develop upstream (but still within the heliosheath) where collisionless reconnection is unfavorable -- large perturbations of the sector structure near the heliopause will cause compressions of the current sheet upstream, triggering reconnection. As a result, the magnetic field in the heliosheath sector region will be disordered well upstream of the heliopause. We present a 3D MHD simulation with unprecedent numerical resolution that captures the sector boundary. We show that due to the high pressure of the interstellar magnetic field the disordered sectored region fills a large portion of the northern part of the heliosphere with a smaller extension in the southern hemisphere. We test these ideas with observations of energetic electrons, which because of their high velocity are most sensitive to the structure of the magnetic field. We suggest that within our scenario we can explain two significant anomalies in the observations of energetic electrons in the outer heliosphere: the sudden decrease in the intensity of low energy electrons (0.02-1.5MeV) from the LECP instrument on Voyager 2 in 2008 (Decker 2010); and the dramatic

  11. Solar wind composition from sector boundary crossings and coronal mass ejections

    NASA Technical Reports Server (NTRS)

    Ogilvie, K. W.; Coplan, M. A.; Geiss, J.

    1992-01-01

    Using the Ion Composition Instrument (ICI) on board the ISEE-3/ICE spacecraft, average abundances of He-4, He-3, O, Ne, Si, and Fe have been determined over extended periods. In this paper the abundances of He-4, O, Ne, Si, and Mg obtained by the ICI in the region of sector boundary crossings (SBCs), magnetic clouds and bidirectional streaming events (BDSs) are compared with the average abundances. Both magnetic clouds and BDSs are associated with coronal mass ejections (CMEs). No variation of abundance is seen to occur at SBCs except for helium, as has already been observed. In CME-related material, the abundance of neon appears to be high and variable, in agreement with recent analysis of spectroscopic observations of active regions. We find that our observations can be correlated with the magnetic topology in the corona.

  12. The Importance of Reconnection at Sector Boundaries: Another Space Weather Hazard?

    NASA Astrophysics Data System (ADS)

    Qi, Y.; Lai, H.; Russell, C. T.

    2017-12-01

    Sector Boundaries are interfaces between nearly oppositely directed magnetic flux in the solar wind. When the leading solar wind stream is moving more slowly than the following stream a high-pressure ridge appears at the interface, that compresses the plasma sometimes leading to a forward and reverse shock pair that slows the fast stream and accelerate the slow stream. If reconnection at the interface between the streams occurs part of the magnetic flux will be annihilated but the plasma once associated with that magnetic flux remains near the interface causing a sometimes significant short-lived dynamic pressure increase. The declining phase of solar cycle 24 exhibits several examples of the phenomenon with densities reaching over 80 protons cm-3 at speed of about 400 km sec-1. We examine the solar wind context of the phenomenon and the consequences at the magnetosphere using space-based and ground-based observations and comment on their possible generation of geomagnetically-induced currents.

  13. The Moho as a magnetic boundary. [Earth crust-mantle boundary

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.; Thomas, H. H.; Mayhew, M. A.

    1979-01-01

    Magnetism in the crust and the upper mantle and magnetic results indicating that the seismic Moho is a magnetic boundary are considered. Mantle derived rocks - peridotites from St. Pauls rocks, dunite xenoliths from the Kaupulehu flow, and peridotite, dunite, and eclogite xenoliths from Roberts Victor and San Carlos diatremes - are weakly magnetic with saturation magnetization values from 0.013 emu/gm to less than 0.001 emu/gm which is equivalent to 0.01 to 0.001 wt% Fe304. Literature on the minerals in mantle xenoliths shows that metals and primary Fe304 are absent, and that complex Cr, Mg, Al, and Fe spinels are dominant. These spinels are non-magnetic at mantle temperatures, and the crust/mantle boundary can be specified as a magnetic mineralogy discontinuity. The new magnetic results indicate that the seismic Moho is a magnetic boundary, the source of magnetization is in the crust, and the maximum Curie isotherm depends on magnetic mineralogy and is located at depths which vary with the regional geothermal gradient.

  14. The magnetic nature of umbra-penumbra boundary in sunspots

    NASA Astrophysics Data System (ADS)

    Jurčák, J.; Rezaei, R.; González, N. Bello; Schlichenmaier, R.; Vomlel, J.

    2018-03-01

    Context. Sunspots are the longest-known manifestation of solar activity, and their magnetic nature has been known for more than a century. Despite this, the boundary between umbrae and penumbrae, the two fundamental sunspot regions, has hitherto been solely defined by an intensity threshold. Aim. Here, we aim at studying the magnetic nature of umbra-penumbra boundaries in sunspots of different sizes, morphologies, evolutionary stages, and phases of the solar cycle. Methods: We used a sample of 88 scans of the Hinode/SOT spectropolarimeter to infer the magnetic field properties in at the umbral boundaries. We defined these umbra-penumbra boundaries by an intensity threshold and performed a statistical analysis of the magnetic field properties on these boundaries. Results: We statistically prove that the umbra-penumbra boundary in stable sunspots is characterised by an invariant value of the vertical magnetic field component: the vertical component of the magnetic field strength does not depend on the umbra size, its morphology, and phase of the solar cycle. With the statistical Bayesian inference, we find that the strength of the vertical magnetic field component is, with a likelihood of 99%, in the range of 1849-1885 G with the most probable value of 1867 G. In contrast, the magnetic field strength and inclination averaged along individual boundaries are found to be dependent on the umbral size: the larger the umbra, the stronger and more horizontal the magnetic field at its boundary. Conclusions: The umbra and penumbra of sunspots are separated by a boundary that has hitherto been defined by an intensity threshold. We now unveil the empirical law of the magnetic nature of the umbra-penumbra boundary in stable sunspots: it is an invariant vertical component of the magnetic field.

  15. Association of corotating magnetic sector structure with Jupiters decameter-wave radio emissions

    NASA Technical Reports Server (NTRS)

    Barrow, C. H.

    1979-01-01

    Chree (superposed epoch) analyses of Jupiter's decameter-wave radio emission taken from the new Thieman (1979) catalog show highly significant correlation with solar activity indicated by the geomagnetic Ap index. The correlation effects can be explained in terms of corotating interplanetary magnetic sector features. At times when the solar wind velocity is relatively low, about 300 to 350 km/s, a sector boundary can encounter the Earth and Jupiter almost simultaneously during the period immediately before opposition. After opposition this will not normally occur as the solar wind velocities necessary are too low. The correlation effects are much enhanced for the three apparitions of 1962-1964 during which a relatively stable and long-lived sector pattern was present. Chree analyses for this period indicate periodicities, approximately equal to half the solar rotation period, in the Jupiter data.

  16. Magnetization due to localized states on graphene grain boundary

    PubMed Central

    Dutta, Sudipta; Wakabayashi, Katsunori

    2015-01-01

    Magnetism in graphene has been found to originate from various defects, e.g., vacancy, edge formation, add-atoms etc. Here, we discuss about an alternate route of achieving magnetism in graphene via grain boundary. During chemical vapor deposition of graphene, several graphene nucleation centers grow independently and face themselves with unusual bonding environment, giving rise to the formation of grain boundaries. We investigate the origin of magnetism in such grain boundaries within first-principles calculations, by letting two nucleation centers interact with each other at their interface. We observe formation of unprecedented point defect, consisting of fused three-membered and larger carbon rings, which induces net magnetization to graphene quantum dots. In case of periodic lattices, the appearance of array of point defects leads to the formation of magnetic grain boundaries. The net magnetization on these defects arises due to the deviation from bipartite characteristics of pristine graphene. We observe magnetic grain boundary induced dispersion less flat bands near Fermi energy, showing higher localization of electrons. These flat bands can be accessed via small doping, leading to enhanced magnetism. Moreover, the grain boundaries can induce asymmetric spin conduction behavior along the cross boundary direction. These properties can be exploited for sensor and spin-filtering applications. PMID:26145161

  17. A magnetic boundary layer at the magnetopause

    NASA Astrophysics Data System (ADS)

    Kartalev, M. D.; Simeonov, G.

    A new approach in the boundary layer description of the magnetopause is proposed. The magnetopause is considered as a mixing region of two streams of plasma with different parameters. The assumption is made that wave-particle interactions cause the plasma to be resistive. Thus only the magnetic viscosity is supposed to be essential. Other dissipation effects are neglected. The plasma and magnetic field conditions at the outer boundary of the layer can be obtained from the solution of the nondissipative problem for the magnetosheath. The magnetic field is assumed to be known at the inner boundary. No further conditions are needed in our formulation of the problem. The variation of the flow parameters and the magnetic field can be obtained numerically.

  18. Boundary work for implementing adaptive management: A water sector application.

    PubMed

    Adem Esmail, Blal; Geneletti, Davide; Albert, Christian

    2017-09-01

    Boundary work, defined as effort to mediate between knowledge and action, is a promising approach for facilitating knowledge co-production for sustainable development. Here, we investigate a case study of knowledge co-production, to assess the applicability of boundary work as a conceptual framework to support implementing adaptive management in the water sector. We refer to a boundary work classification recently proposed by Clark et al., (2016), based on three types of knowledge uses, i.e. enlightenment, decision-, and negotiation-support, and three types of sources, i.e. personal expertise, single, and multiple communities of expertise. Our empirical results confirm boundary work has been crucial for the three types of knowledge use. For enlightenment and decision-support, effective interaction among knowledge producers and users was achieved through diverse boundary work practices, including joint agenda setting, and sharing of data and expertise. This initial boundary work eased subsequent knowledge co-production for decision-support and negotiations, in combination with stepping up of cooperation between relevant actors, suitable legislation and pressure for problem solving. Our analysis highlighted the temporal dimension matters - building trust around enlightenment first, and then using this as a basis for managing knowledge co-production for decision-, and negotiation support. We reconfirmed that boundary work is not a single time achievement, rather is a dynamic process, and we emphasized the importance of key actors driving the process, such as water utilities. Our results provide a rich case study of how strategic boundary work can facilitate knowledge co-production for adaptive management in the water sector. The boundary work practices employed here could also be transferred to other cases. Water utilities, as intermediaries between providers and beneficiaries of the important water-related ecosystem service of clean water provision, can indeed serve

  19. Mass spectrometer with magnetic pole pieces providing the magnetic fields for both the magnetic sector and an ion-type vacuum pump

    NASA Technical Reports Server (NTRS)

    Sieradski, L. M.; Giffin, C. E.; Nier, A. O. (Inventor)

    1976-01-01

    A mass spectrometer (MS) with unique magnetic pole pieces which provide a homogenous magnetic field across the gap of the MS magnetic sector as well as the magnetic field across an ion-type vacuum pump is disclosed. The pole pieces form the top and bottom sides of a housing. The housing is positioned so that portions of the pole pieces form part of the magnetic sector with the space between them defining the gap region of the magnetic sector, through which an ion beam passes. The pole pieces extend beyond the magnetic sector with the space between them being large enough to accommodate the electrical parts of an ion-type vacuum pump. The pole pieces which provide the magnetic field for the pump, together with the housing form the vacuum pump enclosure or housing.

  20. Transparency of a magnetic cloud boundary for cosmic rays

    NASA Astrophysics Data System (ADS)

    Petukhov, I. S.; Petukhov, S. I.

    2013-02-01

    We have suggested a model of magnetic cloud presented as a torus with magnetic flux rope structure situated inside the interplanetary corona mass ejecta expanding radially away from the Sun through the interplanetary medium. The magnetic field of the torus changing during its propagation has been obtained. The magnetic cloud — solar wind boundary transparency for cosmic rays with different energies depending on the cloud orientation and properties of the torus magnetic field has been determined by means of calculation of the particle trajectories at the boundary.

  1. Factors Controlling the Position of the Martian Magnetic Pileup Boundary

    NASA Technical Reports Server (NTRS)

    Crider, D. H.; Acuna, M.; Vignes, D.; Krymskii, A.; Breus, T.; Ness, N.

    2003-01-01

    The magnetic pileup boundary (MPB) at Mars is the position where the dominant ion of the plasma changes from solar wind protons to heavy ions of planetary origin. As such, it is the obstacle to solar wind ions. We investigate the factors that influence the shape and position of the magnetic pileup boundary at Mars in order to better understand the Martian obstacle to the solar wind. Employing MGS data, we determine how the Martian MPB moves in response to factors including solar wind pressure and crustal magnetic fields. We also study the factors affecting the thickness of the MPB. Further, we compare the magnetic pileup boundary to the magnetic barrier at Venus. Direct comparison aids in our interpretation of the physics involved in the solar wind interaction with planets lacking a significant intrinsic magnetic field.

  2. Numerical Simulation on a Possible Formation Mechanism of Interplanetary Magnetic Cloud Boundaries

    NASA Astrophysics Data System (ADS)

    Fan, Quan-Lin; Wei, Feng-Si; Feng, Xue-Shang

    2003-08-01

    The formation mechanism of the interplanetary magnetic cloud (MC) boundaries is numerically investigated by simulating the interactions between an MC of some initial momentum and a local interplanetary current sheet. The compressible 2.5D MHD equations are solved. Results show that the magnetic reconnection process is a possible formation mechanism when an MC interacts with a surrounding current sheet. A number of interesting features are found. For instance, the front boundary of the MCs is a magnetic reconnection boundary that could be caused by a driven reconnection ahead of the cloud, and the tail boundary might be caused by the driving of the entrained flow as a result of the Bernoulli principle. Analysis of the magnetic field and plasma data demonstrates that at these two boundaries appear large value of the plasma parameter β, clear increase of plasma temperature and density, distinct decrease of magnetic magnitude, and a transition of magnetic field direction of about 180 degrees. The outcome of the present simulation agrees qualitatively with the observational results on MC boundary inferred from IMP-8, etc. The project supported by National Natural Science Foundation of China under Grant Nos. 40104006, 49925412, and 49990450

  3. Changes in magnetic domain structure during twin boundary motion in single crystal Ni-Mn-Ga exhibiting magnetic shape memory effect

    NASA Astrophysics Data System (ADS)

    Kopecký, V.; Fekete, L.; Perevertov, O.; Heczko, O.

    2016-05-01

    The complexity of Ni-Mn-Ga single crystal originates from the interplay between ferromagnetic domain structure and ferroelastic twinned microstructure. Magnetic domain structure in the vicinity of single twin boundary was studied using magneto-optical indicator film and magnetic force microscopy technique. The single twin boundary of Type I was formed mechanically and an initial magnetization state in both variants were restored by local application of magnetic field (≈40 kA/m). The differently oriented variants exhibited either stripe or labyrinth magnetic domain pattern in agreement with the uniaxial magnetocrystalline anisotropy of the martensite. The twin boundary was then moved by compressive or tensile stress. The passage of the boundary resulted in the formation of granular or rake domains, respectively. Additionally, the specific magnetic domains pattern projected by twin boundary gradually vanished during twin boundary motion.

  4. Implications for Crustal Structures and Heat Fluxes from Depth-to-the-Bottom of the Magnetic Source Estimates in West Antarctica, Amundsen Sea Sector

    NASA Astrophysics Data System (ADS)

    Dziadek, R.; Ferraccioli, F.; Gohl, K.; Spiegel, C.; Kaul, N. E.

    2017-12-01

    The West Antarctic Rift System is one of the least understood rift systems on earth, but displays a unique coupled relationship between tectonic processes and ice sheet dynamics. Geothermal heat flux (GHF) is a poorly constrained parameter in Antarctica and suspected to affect basal conditions of ice sheets, i.e., basal melting and subglacial hydrology. Thermomechanical models demonstrate the influential boundary condition of geothermal heat flux for (paleo) ice sheet stability. Young, continental rift systems are regions with significantly elevated geothermal heat flux (GHF), because the transient thermal perturbation to the lithosphere caused by rifting requires 100 Ma to reach long-term thermal equilibrium. We discuss airborne, high-resolution magnetic anomaly data from the Amundsen Sea Sector, to provide additional insight into deeper crustal structures related to the West Antarctic Rift System in the Amundsen/Bellingshausen sector. With the depth-to-the-bottom of the magnetic source (DBMS) estimates we reveal spatial changes at the bottom of the igneous crust and the thickness of the magnetic layer, which can be further incorporated into tectonic interpretations. The DBMS also marks an important temperature transition zone of approximately 580°C and therefore serves as a boundary condition for our numerical FEM thermal models in 2D and 3D.

  5. The Moho as a magnetic boundary

    NASA Technical Reports Server (NTRS)

    Wasilewski, P. J.; Thomas, H. H.; Mayhew, M. A.

    1979-01-01

    Magnetic data are presented for mantle derived rocks: peridtites from St. Pauls rocks, dunite xenoliths from the kaupulehu flow in Hawaii, as well as peridolite, dunite and eclogite xenoliths from Roberts Victor, Dutoitspan, Kilbourne Hole, and San Carlos diatremes. The rocks are paramagnetic or very weakly ferromagnetic at room temperature. Saturation magnetization values range from 0.013 emu/gm to less than 0.001 emu/gm. A review of pertinent literature dealing with analysis of the minerals in mantle xenoliths provides evidence that metals and primary Fe3O4 are absent, and that complex CR, Mg, Al, and Fe spinels dominate the oxide mineralogy. All of the available evidence supports the magnetic results, indicating that the seismic MOHO is a magnetic boundary.

  6. Direct Determination of Atomic Structure and Magnetic Coupling of Magnetite Twin Boundaries.

    PubMed

    Chen, Chunlin; Li, Hongping; Seki, Takehito; Yin, Deqiang; Sanchez-Santolino, Gabriel; Inoue, Kazutoshi; Shibata, Naoya; Ikuhara, Yuichi

    2018-03-27

    Clarifying how the atomic structure of interfaces/boundaries in materials affects the magnetic coupling nature across them is of significant academic value and will facilitate the development of state-of-the-art magnetic devices. Here, by combining atomic-resolution transmission electron microscopy, atomistic spin-polarized first-principles calculations, and differential phase contrast imaging, we conduct a systematic investigation of the atomic and electronic structures of individual Fe 3 O 4 twin boundaries (TBs) and determine their concomitant magnetic couplings. We demonstrate that the magnetic coupling across the Fe 3 O 4 TBs can be either antiferromagnetic or ferromagnetic, which directly depends on the TB atomic core structures and resultant electronic structures within a few atomic layers. Revealing the one-to-one correspondence between local atomic structures and magnetic properties of individual grain boundaries will shed light on in-depth understanding of many interesting magnetic behaviors of widely used polycrystalline magnetic materials, which will surely promote the development of advanced magnetic materials and devices.

  7. Portable mass spectrometer with one or more mechanically adjustable electrostatic sectors and a mechanically adjustable magnetic sector all mounted in a vacuum chamber

    DOEpatents

    Andresen, B.D.; Eckels, J.D.; Kimmons, J.F.; Martin, W.H.; Myers, D.W.; Keville, R.F.

    1992-10-06

    A portable mass spectrometer is described having one or more electrostatic focusing sectors and a magnetic focusing sector, all of which are positioned inside a vacuum chamber, and all of which may be adjusted via adjustment means accessible from outside the vacuum chamber. Mounting of the magnetic sector entirely within the vacuum chamber permits smaller magnets to be used, thus permitting reductions in both weight and bulk. 13 figs.

  8. Magnetic field effect on the liquidus boundary of Bi-Mn binary system

    NASA Astrophysics Data System (ADS)

    Mitsui, Yoshifuru; Koyama, Keiichi; Oikawa, Katsunari; Watanabe, Kazuo

    2014-10-01

    The magnetic field effect (MFE) on liquidus boundary of Bi-Mn binary system was investigated by differential thermal analysis (DTA) and the computer coupling of phase diagram method (CALPHAD). The liquidus boundary for Bi-18at.%Mn and Bi-24at.%Mn rose clearly by the application of the magnetic fields. The MFE for liquidus boundary temperature Tliq changed from ΔTliq∝B2 to ΔTliq∝B because of the large increase of the peritectic temperature from BiMn and BiMn1.08 by the application of magnetic field.

  9. Study of magnetic field distribution in anisotropic single twin-boundary magnetic shape memory (MSM) element in actuators

    NASA Astrophysics Data System (ADS)

    Gabdullin, N.; Khan, S. H.

    2017-10-01

    Magnetic shape memory effect exhibited by certain alloys at room temperature is known for almost 20 years. The most studied MSM alloys are Ni-Mn-Ga alloys which exhibit up to 12% magnetic field-induced strain (change in shape) depending on microstructure. A multibillion cycle operation without malfunction along with their “smart” properties make them very promising for application in electromagnetic (EM) actuators and sensors. However, considerable twinning stress of MSM crystals resulting in magneto-mechanical hysteresis decreases the efficiency and output force of MSM actuators. Whereas twinning stress of conventional MSM crystals has been significantly decreased over the years, novel crystals with Type II twin boundaries (TBs) possess even lower twinning stress. Unfortunately, the microstructure of MSM crystals with very low twinning stress tends to be unstable leading to their rapid crack growth. Whilst this phenomenon has been studied experimentally, the magnetic field distribution in anisotropic single twin-boundary MSM elements has not been considered yet. This paper analyses the magnetic field distribution in two-variant single twin-boundary MSM elements and discusses its effects on magnetic field-induced stress acting on the twin boundary.

  10. The determination of interplanetary magnetic field polarities around sector boundaries using E greater than 2 keV electrons

    NASA Technical Reports Server (NTRS)

    Kahler, S.; Lin, R. P.

    1994-01-01

    The determination of the polarities of interplanetary magnetic fields (whether the field direction is outward from or inward toward the sun) has been based on a comparison of observed field directions with the nominal Parker spiral angle. These polarities can be mapped back to the solar source field polarities. This technique fails when field directions deviate substantially from the Parker angle or when fields are substantially kinked. We introduce a simple new technique to determine the polarities of interplanetary fields using E greater than 2 keV interplanetary electrons which stream along field lines away from the sun. Those electrons usually show distinct unidirectional pitch-angle anisotropies either parallel or anti-parallel to the field. Since the electron flow direction is known to be outward from the sun, the anisotropies parallel to the field indicate outward-pointing, positive-polarity fields, and those anti-parallel indicate inward-pointing, negative-polarity fields. We use data from the UC Berkeley electron experiment on the International Sun Earth Explorer 3 (ISSE-3) spacecraft to compare the field polarities deduced from the electron data, Pe (outward or inward), with the polarities inferred from field directions, Pd, around two sector boundaries in 1979. We show examples of large (greater than 100 deg) changes in azimuthal field direction Phi over short (less than 1 hr) time scales, some with and some without reversals in Pe. The latter cases indicate that such large directional changes can occur in unipolar structures. On the other hand, we found an example of a change in Pe during which the rotation in Phi was less than 30 deg, indicating polarity changes in nearly unidirectional structures. The field directions are poor guides to the polarities in these cases.

  11. Coercivity degradation caused by inhomogeneous grain boundaries in sintered Nd-Fe-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Chen, Hansheng; Yun, Fan; Qu, Jiangtao; Li, Yingfei; Cheng, Zhenxiang; Fang, Ruhao; Ye, Zhixiao; Ringer, Simon P.; Zheng, Rongkun

    2018-05-01

    Quantitative correlation between intrinsic coercivity and grain boundaries in three dimensions is critical to further improve the performance of sintered Nd-Fe-B permanent magnets. Here, we quantitatively reveal the local composition variation across and especially along grain boundaries using the powerful atomic-scale analysis technique known as atom probe tomography. We also estimate the saturation magnetization, magnetocrystalline anisotropy constant, and exchange stiffness of the grain boundaries on the basis of the experimentally determined structure and composition. Finally, using micromagnetic simulations, we quantify the intrinsic coercivity degradation caused by inhomogeneous grain boundaries. This approach can be applied to other magnetic materials for the analysis and optimization of magnetic properties.

  12. The Boundaries and Connections between the VET and Higher Education Sectors: "Confused, Contested and Collaborative." Occasional Paper

    ERIC Educational Resources Information Center

    Fowler, Craig

    2017-01-01

    Internationally, Australia's tertiary education system, comprising the higher education and vocational education and training (VET) sectors, is highly regarded, with both sectors subject to ongoing national review and reforms. This paper explores in detail the multiple issues that lie at what might be termed the "boundaries and…

  13. Investigation of a marine magnetic polarity reversal boundary in cross-section at the northern boundary of the Kane Megamullion, Mid-Atlantic Ridge 23°40'N

    NASA Astrophysics Data System (ADS)

    Xu, M.; Tivey, M.

    2016-12-01

    Near-bottom magnetic field measurements made by the submersible Nautile during the 1992 Kanaut Expedition define the cross-sectional geometry of magnetic polarity reversal boundaries and the vertical variation of crustal magnetization in lower oceanic crust exposed along the Kane Transform Fault (TF) at the northern boundary of the Kane Megamullion (KMM). The KMM exposes lower crust and upper mantle rocks on a low-angle normal fault that was active between 3.3 Ma and 2.1 Ma. The geometry of the polarity boundaries is estimated from an inversion of the submarine magnetic data for crustal magnetization. In general, the polarity boundaries dip away from the ridge axis along the Kane TF scarp, with a west-dipping angle of 45° in the shallow (<1 km) crust and <20° in the deeper crust. The existence of the magnetic polarity boundaries (e.g. C2r.2r/C2An.1n, 2.581 Ma) indicates that the lower crustal gabbros and upper mantle serpentinized peridotites are able to record a coherent magnetic signal. Our results support the conclusion of Williams [2007] that the lower crust cools through the Curie temperature of magnetite to become magnetic, with the polarity boundaries representing both frozen isotherms and isochrons. We also test the effects of the rotation of this isotherm structure and/or footwall rotation, and find that the magnetic polarity boundary geometry is not sensitive to these directional changes.

  14. Investigation of a marine magnetic polarity reversal boundary in cross section at the northern boundary of the Kane Megamullion, Mid-Atlantic Ridge, 23°40'N

    NASA Astrophysics Data System (ADS)

    Xu, Min; Tivey, M. A.

    2016-05-01

    Near-bottom magnetic field measurements made by the submersible Nautile during the 1992 Kanaut Expedition define the cross-sectional geometry of magnetic polarity reversal boundaries and the vertical variation of crustal magnetization in lower oceanic crust exposed along the Kane Transform Fault (TF) at the northern boundary of the Kane Megamullion (KMM). The KMM exposes lower crust and upper mantle rocks on a low-angle normal fault that was active between 3.3 Ma and 2.1 Ma. The geometry of the polarity boundaries is estimated from an inversion of the submarine magnetic data for crustal magnetization. In general, the polarity boundaries dip away from the ridge axis along the Kane TF scarp, with a west dipping angle of ~45° in the shallow (<1 km) crust and <20° in the deeper crust. The existence of the magnetic polarity boundaries (e.g., C2r.2r/C2An.1n, ~2.581 Ma) indicates that the lower crustal gabbros and upper mantle serpentinized peridotites are able to record a coherent magnetic signal. Our results support the conclusion of Williams (2007) that the lower crust cools through the Curie temperature of magnetite to become magnetic, with the polarity boundaries representing both frozen isotherms and isochrons. We also test the effects of the rotation of this isotherm structure and/or footwall rotation and find that the magnetic polarity boundary geometry is not sensitive to these directional changes.

  15. Evolution of relative magnetic helicity. New boundary conditions for the vector potential

    NASA Astrophysics Data System (ADS)

    Yang, Shangbin; Büchner, Jörg; Skála, Jan; Zhang, Hongqi

    2018-05-01

    Context. For a better understanding of the dynamics of the solar corona, it is important to analyse the evolution of the helicity of the magnetic field. Since the helicity cannot be directly determined by observations, we have recently proposed a method to calculate the relative magnetic helicity in a finite volume for a given magnetic field, which however required the flux to be balanced separately on all the sides of the considered volume. Aims: We developed a scheme to obtain the vector potential in a volume without the above restriction at the boundary. We studied the dissipation and escape of relative magnetic helicity from an active region. Methods: In order to allow finite magnetic fluxes through the boundaries, a Coulomb gauge was constructed that allows for global magnetic flux balance. The property of sinusoidal function was used to obtain the vector potentials at the 12 edges of the considered rectangular volume extending above an active region. We tested and verified our method in a theoretical fore-free magnetic field model. Results: We applied the new method to the former calculation data and found a difference of less than 1.2%. We also applied our method to the magnetic field above active region NOAA 11429 obtained by a new photospheric-data-driven magnetohydrodynamics (MHD) model code GOEMHD3. We analysed the magnetic helicity evolution in the solar corona using our new method. We find that the normalized magnetic helicity (H/Φ2) is equal to -0.038 when fast magnetic reconnection is triggered. This value is comparable to the previous value (-0.029) in the MHD simulations when magnetic reconnection happened and the observed normalized magnetic helicity (-0.036) from the eruption of newly emerging active regions. We find that only 8% of the accumulated magnetic helicity is dissipated after it is injected through the bottom boundary. This is in accordance with the Woltjer conjecture. Only 2% of the magnetic helicity injected from the bottom boundary

  16. Scattering of magnetized electrons at the boundary of low temperature plasmas

    NASA Astrophysics Data System (ADS)

    Krüger, Dennis; Trieschmann, Jan; Brinkmann, Ralf Peter

    2018-02-01

    Magnetized technological plasmas with magnetic fields of 10-200 mT, plasma densities of 1017-1019 m-3, gas pressures of less than 1 Pa, and electron energies from a few to (at most) a few hundred electron volts are characterized by electron Larmor radii r L, that are small compared to all other length scales of the system, including the spatial scale L of the magnetic field and the collisional mean free path λ. In this regime, the classical drift approximation applies. In the boundary sheath of these discharges, however, that approximation breaks down: The sheath penetration depth of electrons (a few to some ten Debye length λ D; depending on the kinetic energy; typically much smaller than the sheath thickness of tens/hundreds of λ D) is even smaller than r L. For a model description of the electron dynamics, an appropriate boundary condition for the plasma/sheath interface is required. To develop such, the interaction of magnetized electrons with the boundary sheath is investigated using a 3D kinetic single electron model that sets the larger scales L and λ to infinity, i.e. neglects magnetic field gradients, the electric field in the bulk, and collisions. A detailed comparison of the interaction for a Bohm sheath (which assumes a finite Debye length) and a hard wall model (representing the limit {λ }{{D}}\\to 0; also called the specular reflection model) is conducted. Both models are found to be in remarkable agreement with respect to the sheath-induced drift. It is concluded that the assumption of specular reflection can be used as a valid boundary condition for more realistic kinetic models of magnetized technological plasmas.

  17. Steady state toroidal magnetic field at earth's core-mantle boundary

    NASA Technical Reports Server (NTRS)

    Levy, Eugene H.; Pearce, Steven J.

    1991-01-01

    Measurements of the dc electrical potential near the top of earth's mantle have been extrapolated into the deep mantle in order to estimate the strength of the toroidal magnetic field component at the core-mantle interface. Recent measurements have been interpreted as indicating that at the core-mantle interface, the magnetic toroidal and poloidal field components are approximately equal in magnitude. A motivation for such measurements is to obtain an estimate of the strength of the toroidal magnetic field in the core, a quantity important to our understanding of the geomagnetic field's dynamo generation. Through the use of several simple and idealized calculation, this paper discusses the theoretical relationship between the amplitude of the toroidal magnetic field at the core-mantle boundary and the actual amplitude within the core. Even with a very low inferred value of the toroidal field amplitude at the core-mantle boundary, (a few gauss), the toroidal field amplitude within the core could be consistent with a magnetohydrodynamic dynamo dominated by nonuniform rotation and having a strong toroidal magnetic field.

  18. Inferring Lower Boundary Driving Conditions Using Vector Magnetic Field Observations

    NASA Technical Reports Server (NTRS)

    Schuck, Peter W.; Linton, Mark; Leake, James; MacNeice, Peter; Allred, Joel

    2012-01-01

    Low-beta coronal MHD simulations of realistic CME events require the detailed specification of the magnetic fields, velocities, densities, temperatures, etc., in the low corona. Presently, the most accurate estimates of solar vector magnetic fields are made in the high-beta photosphere. Several techniques have been developed that provide accurate estimates of the associated photospheric plasma velocities such as the Differential Affine Velocity Estimator for Vector Magnetograms and the Poloidal/Toroidal Decomposition. Nominally, these velocities are consistent with the evolution of the radial magnetic field. To evolve the tangential magnetic field radial gradients must be specified. In addition to estimating the photospheric vector magnetic and velocity fields, a further challenge involves incorporating these fields into an MHD simulation. The simulation boundary must be driven, consistent with the numerical boundary equations, with the goal of accurately reproducing the observed magnetic fields and estimated velocities at some height within the simulation. Even if this goal is achieved, many unanswered questions remain. How can the photospheric magnetic fields and velocities be propagated to the low corona through the transition region? At what cadence must we observe the photosphere to realistically simulate the corona? How do we model the magnetic fields and plasma velocities in the quiet Sun? How sensitive are the solutions to other unknowns that must be specified, such as the global solar magnetic field, and the photospheric temperature and density?

  19. Dipping Magnetic Reversal Boundaries at Endeavor Deep: Implications for Crustal Accretion

    NASA Astrophysics Data System (ADS)

    Pockalny, R. A.; Shields, A. C.; Larson, R. L.; Popham, C.

    2005-12-01

    Endeavor Deep, created by ongoing rifting along the northeastern boundary of the Juan Fernandez Microplate, provides a generous 75-km long view of the upper 1-3 km of oceanic crust created ~3 Ma at a fast-spreading ridge (~80 km/Myr, half-rate). Recent near-bottom surveys with the ROV Jason collected high-resolution video, rock samples, and 3-component magnetometer data along a 5 km-wide section of the southern wall of the deep. The video and rock samples define a crustal section with 300-500 m of primarily pillows and flows overlying a 400-500 m transition zone of extrusives and dykes. Forward modeling of the total magnetic intensity calculated from the 3-component magnetometer data identifies a magnetic polarity reversal that corresponds to a reversal boundary within magnetic anomaly 2a (C2An.2r - C2AN.3n , ~3.33 Ma). The location of the modeled polarity transition suggests the reversal boundary dips downward toward the original ridge axis with shallow dips (15 degrees) in the extrusive layer becoming increasingly steeper (25 degrees) in the deeper transition zone. The dipping character of the reversal boundary has also been observed along the walls of the Blanco Fracture Zone and is consistent with evolving crustal accretion models for seafloor created at intermediate- and fast-spreading rates, which predicts the rotation of the upper extrusive layer back toward the ridge axis. As a consequence of this rotation, originally horizontal flow boundaries will dip back toward the ridge axis and the magnitude of the dip will increase with depth into the crustal section. A small reversed magnetic polarity is also observed deeper within normally magnetized C2AN.3n chron, but with a very shallow dip (3-5 degrees). We doubt this is another normal-reverse-normal polarity transition, since the anomaly suspiciously coincides with the transition from dykes to extrusives. Therefore, we believe this anomaly is either the result of an edge-effect created by the different magnetic

  20. Effect of magnetization boundary condition on cavity magnon polariton of YIG thin film.

    PubMed

    Jiang, H H; Xiao, Y; Hu, C M; Guo, H; Xia, K

    2018-06-22

    Motivated by recent studies of cavity magnon polariton (CMP), we extended a previous theoretical work to generalize microwave transmission calculation with various magnetization boundary condition of YIG thin film embedded in cavity. It is found that numerical implementation given in this paper can be easily applied to other magnetization boundary condition and extended to magnetic multilayers. Numerical results show that ferromagnetic resonance mode of microwave transmission spectrum, which is absent in previous calculation, can be recovered by altering the pinning condition of surface spins. The demonstrated reliability of our theory opens attractive perspectives for studying CMP of thin film with complicated surface magnetization distribution and magnetic multilayers.

  1. Effect of magnetization boundary condition on cavity magnon polariton of YIG thin film

    NASA Astrophysics Data System (ADS)

    Jiang, H. H.; Xiao, Y.; Hu, C. M.; Guo, H.; Xia, K.

    2018-06-01

    Motivated by recent studies of cavity magnon polariton (CMP), we extended a previous theoretical work to generalize microwave transmission calculation with various magnetization boundary condition of YIG thin film embedded in cavity. It is found that numerical implementation given in this paper can be easily applied to other magnetization boundary condition and extended to magnetic multilayers. Numerical results show that ferromagnetic resonance mode of microwave transmission spectrum, which is absent in previous calculation, can be recovered by altering the pinning condition of surface spins. The demonstrated reliability of our theory opens attractive perspectives for studying CMP of thin film with complicated surface magnetization distribution and magnetic multilayers.

  2. Dynamics of the penetration boundaries of solar protons during a strong magnetic storm

    NASA Technical Reports Server (NTRS)

    Glukhov, G. A.; Kratenko, Y. P.; Mineev, Y. V.

    1985-01-01

    The variations in the equatorial penetration boundary of solar protons with E sub p = 0.9 to 8.0 MeV during a strong magnetic storm of April 3 to 5, were analyzed. The dynamics of this boundary is compared with the dynamics of the outer trapping boundary of electrons with E sub e = - 0.3 to 0.6 MeV. The solar-proton penetration and the structure of the real magnetic field are studied. The unique data on the thin structure of development of a magnetospheric substorm were obtained for the first time.

  3. Lithologic boundaries from gravity and magnetic anomalies over Proterozoic Dalma volcanics

    NASA Astrophysics Data System (ADS)

    Yadav, Pramod Kumar; Adhikari, P. K.; Srivastava, Shalivahan; Maurya, Ved P.; Tripathi, Anurag; Singh, Shailendra; Singh, Roshan K.; Bage, Ashish K.

    2018-03-01

    Dalma volcanics (DVs) has intruded the older Singhbhum Group of Metapelites. Despite DVs being rich in mineralisation, its boundaries are not clearly demarcated. Gravity and magnetic surveys have been attempted for mapping the boundaries in DVs. These surveys were made in the northern fringe of the DVs over an area of ˜ 0.70 km2 along 13 parallel lines at 50 m spacing. The data was acquired at ˜ 25 m spacing. The surveys were taken for determination of lithological boundaries, depths and nature of causative source using Euler depth solutions and radially averaged power spectrum (RAPS). Residual anomaly maps of gravity and magnetic intensity show the same trend as that of Bouguer gravity anomaly and total magnetic intensity anomaly map indicating towards shallow sources. The magnetic map in general follows the same pattern as that of gravity anomaly maps. The map shows coincident high gravity and magnetic anomalies. These anomalies together with resistivity signatures confirm that the northern fringe of DVs hosts volcanogenic massive sulphide settings. The Euler depth solution delineated the lateral boundaries and nature of the source. It seems that the source is of spherical nature lying within a depth range of 25-40 m. The obtained lithological (vertical) units from RAPS are between Lower DVs, Upper DVs and Singhbhum Group Metapelites at depths of ˜ 15, ˜ 25 and ˜ 40 m, respectively. The metallogeny is associated with the Upper DVs and the corresponding delineated lithological (vertical) unit is indicative of the top of the ore body. Good agreement is observed with the geological succession from the drilling data and resistivity data. The findings suggest that the northern fringe of DVs could be a preferred target for drilling.

  4. Observation of chiral currents at the magnetic domain boundary of a topological insulator

    DOE PAGES

    Wang, Y. H.; Kirtley, J. R.; Katmis, F.; ...

    2015-08-28

    A magnetic domain boundary on the surface of a three-dimensional topological insulator is predicted to host a chiral edge state, but direct demonstration is challenging. Here, we used a scanning superconducting quantum interference device to show that current in a magnetized EuS/Bi 2Se 3 heterostructure flows at the edge when the Fermi level is gate-tuned to the surface band gap. We further induced micron-scale magnetic structures on the heterostructure, and detected a chiral edge current at the magnetic domain boundary. The chirality of the current was determined by magnetization of the surrounding domain and its magnitude by the local chemicalmore » potential rather than the applied current. As a result, such magnetic structures, provide a platform for detecting topological magnetoelectric effects and may enable progress in quantum information processing and spintronics.« less

  5. Dirichlet boundary conditions for arbitrary-shaped boundaries in stellarator-like magnetic fields for the Flux-Coordinate Independent method

    NASA Astrophysics Data System (ADS)

    Hill, Peter; Shanahan, Brendan; Dudson, Ben

    2017-04-01

    We present a technique for handling Dirichlet boundary conditions with the Flux Coordinate Independent (FCI) parallel derivative operator with arbitrary-shaped material geometry in general 3D magnetic fields. The FCI method constructs a finite difference scheme for ∇∥ by following field lines between poloidal planes and interpolating within planes. Doing so removes the need for field-aligned coordinate systems that suffer from singularities in the metric tensor at null points in the magnetic field (or equivalently, when q → ∞). One cost of this method is that as the field lines are not on the mesh, they may leave the domain at any point between neighbouring planes, complicating the application of boundary conditions. The Leg Value Fill (LVF) boundary condition scheme presented here involves an extrapolation/interpolation of the boundary value onto the field line end point. The usual finite difference scheme can then be used unmodified. We implement the LVF scheme in BOUT++ and use the Method of Manufactured Solutions to verify the implementation in a rectangular domain, and show that it does not modify the error scaling of the finite difference scheme. The use of LVF for arbitrary wall geometry is outlined. We also demonstrate the feasibility of using the FCI approach in no n-axisymmetric configurations for a simple diffusion model in a "straight stellarator" magnetic field. A Gaussian blob diffuses along the field lines, tracing out flux surfaces. Dirichlet boundary conditions impose a last closed flux surface (LCFS) that confines the density. Including a poloidal limiter moves the LCFS to a smaller radius. The expected scaling of the numerical perpendicular diffusion, which is a consequence of the FCI method, in stellarator-like geometry is recovered. A novel technique for increasing the parallel resolution during post-processing, in order to reduce artefacts in visualisations, is described.

  6. 6% magnetic-field-induced strain by twin-boundary motion in ferromagnetic Ni-Mn-Ga

    SciTech Connect

    Murray, S. J.; Marioni, M.; Allen, S. M.

    2000-08-07

    Field-induced strains of 6% are reported in ferromagnetic Ni-Mn-Ga martensites at room temperature. The strains are the result of twin boundary motion driven largely by the Zeeman energy difference across the twin boundary. The strain measured parallel to the applied magnetic field is negative in the sample/field geometry used here. The strain saturates in fields of order 400 kA/m and is blocked by a compressive stress of order 2 MPa applied orthogonal to the magnetic field. The strain versus field curves exhibit appreciable hysteresis associated with the motion of the twin boundaries. A simple model accounts quantitatively for the dependencemore » of strain on magnetic field and external stress using as input parameters only measured quantities. (c) 2000 American Institute of Physics.« less

  7. Sector magnets or transverse electromagnetic fields in cylindrical coordinates

    DOE PAGES

    Zolkin, T.

    2017-04-10

    Laplace’s equation is considered for scalar and vector potentials describing electric or magnetic fields in cylindrical coordinates, with invariance along the azimuthal coordinate. In a series, we found special functions which, when expanded to lowest order in power series in radial and vertical coordinates, replicate harmonic polynomials in two variables. These functions are based on radial harmonics found by Edwin M. McMillan forty years ago. In addition to McMillan’s harmonics, a second family of radial harmonics is introduced to provide a symmetric description between electric and magnetic fields and to describe fields and potentials in terms of the same functions.more » Formulas are provided which relate any transverse fields specified by the coefficients in the power series expansion in radial or vertical planes in cylindrical coordinates with the set of new functions. Our result is important for potential theory and for theoretical study, design and proper modeling of sector dipoles, combined function dipoles and any general sector element for accelerator physics. All results are presented in connection with these problems.« less

  8. Sector magnets or transverse electromagnetic fields in cylindrical coordinates

    SciTech Connect

    Zolkin, T.

    Laplace’s equation is considered for scalar and vector potentials describing electric or magnetic fields in cylindrical coordinates, with invariance along the azimuthal coordinate. In a series, we found special functions which, when expanded to lowest order in power series in radial and vertical coordinates, replicate harmonic polynomials in two variables. These functions are based on radial harmonics found by Edwin M. McMillan forty years ago. In addition to McMillan’s harmonics, a second family of radial harmonics is introduced to provide a symmetric description between electric and magnetic fields and to describe fields and potentials in terms of the same functions.more » Formulas are provided which relate any transverse fields specified by the coefficients in the power series expansion in radial or vertical planes in cylindrical coordinates with the set of new functions. Our result is important for potential theory and for theoretical study, design and proper modeling of sector dipoles, combined function dipoles and any general sector element for accelerator physics. All results are presented in connection with these problems.« less

  9. On the fragmentation boundary in magnetized self-gravitating discs

    NASA Astrophysics Data System (ADS)

    Forgan, Duncan; Price, Daniel J.; Bonnell, Ian

    2017-04-01

    We investigate the role of magnetic fields in the fragmentation of self-gravitating discs using 3D global ideal magnetohydrodynamic simulations performed with the PHANTOM smoothed particle hydrodynamics code. For initially toroidal fields, we find two regimes. In the first, where the cooling time is greater than five times the dynamical time, magnetic fields reduce spiral density wave amplitudes, which in turn suppresses fragmentation. This is the case even if the magnetic pressure is only a 10th of the thermal pressure. The second regime occurs when the cooling time is sufficiently short that magnetic fields cannot halt fragmentation. We find that magnetized discs produce more massive fragments, due to both the additional pressure exerted by the magnetic field and the additional angular momentum transport induced by Maxwell stresses. The fragments are confined to a narrower range of initial semimajor axes than those in unmagnetized discs. The orbital eccentricity and inclination distributions of unmagnetized and magnetized disc fragments are similar. Our results suggest that the fragmentation boundary could be at cooling times a factor of 2 lower than predicted by purely hydrodynamical models.

  10. Analysis of suprathermal electron properties at the magnetic pile-up boundary of Comet P/Halley

    NASA Technical Reports Server (NTRS)

    Mazelle, C.; Reme, H.; Sauvaud, J. A.; D'Uston, C.; Carlson, C. W.

    1989-01-01

    Among the plasma discontinuities detected by the Giotto spacecraft around Comet P/Halley, the magnetic pile-up boundary, located at about 135,000 km from the nucleus, has a sharpness which was not foreseen by theoretical models. At this boundary, which marks the beginning of the region where the field lines draped around the nucleus have been piled up, the magnetic field jumps sharply. Electron measurements provided by the RPA experiment show that a clear plasma discontinuity coincides with this magnetic feature. Significant changes occur here in the suprathermal electron distribution function. A magneto-plasma sheet is clearly defined after the boundary. Inside this sheet, close correlations exist between the parameters describing the magnetic field and the electron population. The polytropic equation of state governing the suprathermal electrons in the sheet has been deduced from RPA measurements. Some implications of this law are discussed.

  11. Grain boundary diffusion of Dy films prepared by magnetron sputtering for sintered Nd–Fe–B magnets

    NASA Astrophysics Data System (ADS)

    Chen, W.; Luo, J. M.; Guan, Y. W.; Huang, Y. L.; Chen, M.; Hou, Y. H.

    2018-05-01

    Dy films, deposited on the surface of sintered Nd–Fe–B magnets by magnetron sputtering, were employed for grain boundary diffusion source. High coercivity sintered Nd–Fe–B magnets were successfully prepared. Effects of sputtering power and grain boundary diffusion processes (GBDP) on the microstructure and magnetic properties were investigated in detail. The dense and uniform Dy films were beneficial to prepare high coercivity magnets by GBDP. The maximum coercivity value of 1189 kA m‑1 could be shown, which was an amplification of 22.3%, compared with that of as-prepared Nd–Fe–B magnet. Furthermore, the improved remanence and maximum energy product were also achieved through tuning grain boundary diffusion processes. Our results demonstrated that the formation of (Nd, Dy)2Fe14B shell surrounding Nd2Fe14B grains and fine, uniform and continuous intergranular RE-rich phases jointly contribute to the improved coercivity.

  12. Interplanetary boundary layers at 1 AU. [magnetic field measurements from Explorer 34

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Lemaire, J. F.; Turner, J. M.

    1976-01-01

    The structure and nature of discontinuities in the interplanetary magnetic field at 1 AU in the period March 18, 1971 to April 9, 1971, is determined by using high-resolution magnetic field measurements from Explorer 34. The discontinuities that were selected for this analysis occurred under a variety of interplanetary conditions at an average rate of 0.5/hr. This set does not include all discontinuities that were present, but the sample is large and it is probably representative. Both tangential and rotational discontinuities were identified, the ratio of TD's to RD's being approximately 3 to 1. Tangential discontinuities were observed every day, even among Alfvenic fluctuations. The structure of most of the boundary layers was simple and ordered, i.e., the magnetic field usually changed smoothly and monotonically from one side of the boundary layer to the other.

  13. A study of the relationship between interplanetary parameters and large displacements of the nightside polar cap boundary

    SciTech Connect

    Lester, M.; Freeman, M.P.; Southwood, D.J.

    On July 14, 1982 the Sweden and Britain Radar-Aurora Experiment (SABRE) observed the ionospheric flow reversal boundary at {approximately} 0400 MLT to move equatorward across the radar field of view and then later to return poleward. The polar cap appeared to be considerably inflated at this time. Concurrent observations by ISEE-3 at the L1 libration point of the solar wind speed and density, and of the interplanetary magnetic field (IMF) indicated that the solar wind conditions were unusual throughout the interval under consideration. A mapping of the solar wind parameters from the L1 point to the subsolar magnetopause and thencemore » to the SABRE local time sector indicates that the equatorward motion of the polar cap boundary was controlled by a southward turning of the IMF. The inference of a concomitant increase in open magnetic flux is supported by a comparison of the magnetopause location observed by ISEE-1 on an inbound pass in the 2,100 MLT sector with a magnetopause model based upon the solar wind measurements made by ISEE-3. Some 20 minutes after the expansion of the polar cap boundary was first seen by SABRE, there was a rapid contraction of the boundary, the casue of which was independent of the INF and solar wind parameters, and which had a poleward velocity component in excess of 1,900 m s{sup {minus}1}. the boundary as it moved across the radar field of view was highly structured and oriented at a large angle to the ionospheric footprints of the magnetic L shells. Observations in the premidnight sector by the Air Force Geophysics Laboratory (AFGL) magnetometer array indicate that the polar cap contraction is caused by substorm draining of the polar cap flux and occurs without a clearly associated trigger in the interplanetary medium. The response time in the early morning local time sector to the substorm onset switch is approximately 20 minutes, equivalent to an ionospheric azimuthal phase velocity of some 5 km s{sup {minus}1}.« less

  14. Magnetic properties of Co/Ni grain boundaries after annealing

    NASA Astrophysics Data System (ADS)

    Coutts, Chris; Arora, Monika; Hübner, René; Heinrich, Bret; Girt, Erol

    2018-05-01

    Magnetic and microstructural properties of <111> textured Cu/N×[Co/Ni] films are studied as a function of the number of bilayer repeats N and annealing temperature. M(H) loop measurements show that coercivity, Hc, increases with annealing temperature and that the slope of the saturation curve at Hc has a larger reduction for smaller N. An increase of the magnetic anisotropy (Ku) to saturation magnetization (Ms) ratio after annealing N×[Co/Ni] with N < 15 only partially describes the increase to Hc. Energy-dispersive X-ray spectroscopy analyses performed in scanning transmission electron microscopy mode across cross-sections of as-deposited and annealed Cu/16×[Co/Ni] films show that Cu diffuses from the seed layer into grain boundaries of Co/Ni. Diffusion of Cu reduces exchange coupling (Hex) between the magnetic grains and explains the increase in Hc. Additionally, the difference in the slope of the M(H) curves at Hc between the thick (N = 16) and thin (N = 4) magnetic multilayers is due to Cu diffusion more effectively decoupling magnetic grains in the thinner multilayer.

  15. Change of magnetic domain structure by mechanically induced twin boundary motion in Ni-Mn-Ga single crystal

    NASA Astrophysics Data System (ADS)

    Kopecký, Vít; Heczko, Oleg

    2017-10-01

    The single variant state exhibits usual labyrinth and band magnetic domains depending on orientation of easy magnetization axis. By the passage of single twin boundary induced by mechanical stress the rake and granular domain patterns are formed. These domain patterns are further modified by repeated passage of the twin boundary resulting in similar domain patterns in the sample even though the orientation of the magnetization is different.

  16. VOYAGER OBSERVATIONS OF MAGNETIC SECTORS AND HELIOSPHERIC CURRENT SHEET CROSSINGS IN THE OUTER HELIOSPHERE

    SciTech Connect

    Richardson, J. D.; Burlaga, L. F.; Drake, J. F.

    Voyager 1 ( V1 ) has passed through the heliosheath and is in the local interstellar medium. Voyager 2 ( V2 ) has been in the heliosheath since 2007. The role of reconnection in the heliosheath is under debate; compression of the heliospheric current sheets (HCS) in the heliosheath could lead to rapid reconnection and a reconfiguration of the magnetic field topology. This paper compares the expected and actual amounts of time the Voyager spacecraft observe each magnetic sector and the number of HCS crossings. The predicted and observed values generally agree well. One exception is at Voyager 1 inmore » 2008 and 2009, where the distribution of sectors is more equal than expected and the number of HCS crossings is small. Two other exceptions are at V1 in 2011–2012 and at V2 in 2012, when the spacecraft are in the opposite magnetic sector less than expected and see fewer HCS crossings than expected. These features are consistent with those predicted for reconnection, and consequently searches for other reconnection signatures should focus on these times.« less

  17. Transition from the Sector Zone to the Unipolar Zone in the Heliosheath: Voyager 2 Magnetic Field Observations

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Ness, N. F.

    2011-01-01

    The magnetic polarity pattern observed by Voyager 2 (V2) evolved with time from a nearly equal mixture of positive and negative polarity sectors in the sector zone from 2007.00 to 2007.67 to nearly uniform positive polarity (magnetic fields directed away from the Sun) in the unipolar zone from 2009.6 to 2010.3. This change was caused by the decreasing latitudinal extent of the sector zone, when the minimum extent of the heliospheric current sheet moved northward toward the solar equator as the solar activity associated with solar cycle 23 decreased a minimum in 2010. In the heliosheath, the distribution of daily averages of the magnetic field strength B was lognormal in the sector zone from 2008.83 to 2009.57 and Gaussian in the unipolar zone from 2009.57 to 2010.27. The distribution of daily increments of B was a Tsallis distribution (q-Gaussian distribution) with q = 1.66 +/- 0.010 in the sector zone and . Gaussian (q = 1.01+/-0.29) in the unipolar zone. The unipolar region appears to be in a relatively undisturbed equilibrium state.

  18. Satellite tidal magnetic signals constrain oceanic lithosphere-asthenosphere boundary.

    PubMed

    Grayver, Alexander V; Schnepf, Neesha R; Kuvshinov, Alexey V; Sabaka, Terence J; Manoj, Chandrasekharan; Olsen, Nils

    2016-09-01

    The tidal flow of electrically conductive oceans through the geomagnetic field results in the generation of secondary magnetic signals, which provide information on the subsurface structure. Data from the new generation of satellites were shown to contain magnetic signals due to tidal flow; however, there are no reports that these signals have been used to infer subsurface structure. We use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. The model derived from more than 12 years of satellite data reveals a ≈72-km-thick upper resistive layer followed by a sharp increase in electrical conductivity likely associated with the lithosphere-asthenosphere boundary, which separates colder rigid oceanic plates from the ductile and hotter asthenosphere.

  19. Satellite tidal magnetic signals constrain oceanic lithosphere-asthenosphere boundary

    PubMed Central

    Grayver, Alexander V.; Schnepf, Neesha R.; Kuvshinov, Alexey V.; Sabaka, Terence J.; Manoj, Chandrasekharan; Olsen, Nils

    2016-01-01

    The tidal flow of electrically conductive oceans through the geomagnetic field results in the generation of secondary magnetic signals, which provide information on the subsurface structure. Data from the new generation of satellites were shown to contain magnetic signals due to tidal flow; however, there are no reports that these signals have been used to infer subsurface structure. We use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. The model derived from more than 12 years of satellite data reveals a ≈72-km-thick upper resistive layer followed by a sharp increase in electrical conductivity likely associated with the lithosphere-asthenosphere boundary, which separates colder rigid oceanic plates from the ductile and hotter asthenosphere. PMID:27704045

  20. Coercivity temperature dependence of Sm2Co17-type sintered magnets with different cell and cell boundary microchemistry

    NASA Astrophysics Data System (ADS)

    Yu, Nengjun; Zhu, Minggang; Song, Liwei; Fang, Yikun; Song, KuiKui; Wang, Qiang; Li, Wei

    2018-04-01

    High maximum energy product ((BH)max) Sm(CobalFe0.18Cu0.07Zr0.03)7.7 magnet (type-A) and high temperature Sm(CobalFe0.1Cu0.09Zr0.03)7.2 magnet (type-B) were prepared by a traditional powder metallurgical technology. A record (BH)max of 98.7 kJ/m3 with a coercivity (Hcj) of 501.5 kA/m at 773 K was achieved for the type-B magnet, which is much higher than that of type-A magnet (63.7 kJ/m3). The microstructures of the magnets were revealed by high-resolution transmission electron microscope. The average cell size of the type-A and B magnet are 110 nm and 90 nm, respectively. Moreover, the type-B magnet shows a wider cell boundary than the type-A magnet. Additionally, the element distribution of the cell/cell boundary interfaces was measured by energy-dispersive spectroscopy. The cell phase of the type-A magnet contains a higher Fe content as about 17 at%, comparing with that of the type-B magnet (∼8.9 at%). On the other hand, the Cu content of the cell boundary phase is 18 at% almost twice higher than the type-B magnet (8.6 at%). Theoretical Hcj temperature dependence of these two kinds of magnets indicates that the lower Cu content in the cell boundary phase and the appropriate Fe content in the cell phase are the key factors for the high Hcj for the type-B magnet at elevated temperature.

  1. Controlling the Topological Sector of Magnetic Solitons in Exfoliated Cr 1 / 3 NbS 2 Crystals

    DOE PAGES

    Wang, Lin; Chepiga, N.; Ki, D. -K.; ...

    2017-06-23

    Here, we investigate manifestations of topological order in monoaxial helimagnet Cr 1/3NbS 2 by performing transport measurements on ultrathin crystals. Upon sweeping the magnetic field perpendicularly to the helical axis, crystals thicker than one helix pitch (48 nm) but much thinner than the magnetic domain size (similar to 1 mu m) are found to exhibit sharp and hysteretic resistance jumps. We also show that these phenomena originate from transitions between topological sectors with a different number of magnetic solitons. This is confirmed by measurements on crystals thinner than 48 nm-in which the topological sector cannot change-that do not exhibit anymore » jump or hysteresis. These results show the ability to deterministically control the topological sector of finite-size Cr 1/3NbS 2 and to detect intersector transitions by transport measurements.« less

  2. Controlling the Topological Sector of Magnetic Solitons in Exfoliated Cr 1 / 3 NbS 2 Crystals

    SciTech Connect

    Wang, Lin; Chepiga, N.; Ki, D. -K.

    Here, we investigate manifestations of topological order in monoaxial helimagnet Cr 1/3NbS 2 by performing transport measurements on ultrathin crystals. Upon sweeping the magnetic field perpendicularly to the helical axis, crystals thicker than one helix pitch (48 nm) but much thinner than the magnetic domain size (similar to 1 mu m) are found to exhibit sharp and hysteretic resistance jumps. We also show that these phenomena originate from transitions between topological sectors with a different number of magnetic solitons. This is confirmed by measurements on crystals thinner than 48 nm-in which the topological sector cannot change-that do not exhibit anymore » jump or hysteresis. These results show the ability to deterministically control the topological sector of finite-size Cr 1/3NbS 2 and to detect intersector transitions by transport measurements.« less

  3. Magnetic Field Generation, Particle Energization and Radiation at Relativistic Shear Boundary Layers

    NASA Astrophysics Data System (ADS)

    Liang, Edison; Fu, Wen; Spisak, Jake; Boettcher, Markus

    2015-11-01

    Recent large scale Particle-in-Cell (PIC) simulations have demonstrated that in unmagnetized relativistic shear flows, strong transverse d.c. magnetic fields are generated and sustained by ion-dominated currents on the opposite sides of the shear interface. Instead of dissipating the shear flow free energy via turbulence formation and mixing as it is usually found in MHD simulations, the kinetic results show that the relativistic boundary layer stabilizes itself via the formation of a robust vacuum gap supported by a strong magnetic field, which effectively separates the opposing shear flows, as in a maglev train. Our new PIC simulations have extended the runs to many tens of light crossing times of the simulation box. Both the vacuum gap and supporting magnetic field remain intact. The electrons are energized to reach energy equipartition with the ions, with 10% of the total energy in electromagnetic fields. The dominant radiation mechanism is similar to that of a wiggler, due to oscillating electron orbits around the boundary layer.

  4. Boundary conditions at the gas sectors of superhydrophobic grooves

    NASA Astrophysics Data System (ADS)

    Dubov, Alexander L.; Nizkaya, Tatiana V.; Asmolov, Evgeny S.; Vinogradova, Olga I.

    2018-01-01

    The hydrodynamics of liquid flowing past gas sectors of unidirectional superhydrophobic surfaces is revisited. Attention is focused on the local slip boundary condition at the liquid-gas interface, which is equivalent to the effect of a gas cavity on liquid flow. The system is characterized by a large viscosity contrast between liquid and gas μ /μg≫1 . We interpret earlier results, namely, the dependence of the local slip length on the flow direction, in terms of a tensorial local slip boundary condition and relate the eigenvalues of the local local slip tensor to the texture parameters, such as the width of the groove δ and the local depth of the groove e (y ,α ) . The latter varies in the direction y , orthogonal to the orientation of stripes, and depends on the bevel angle of the groove's edges, π /2 -α , at the point where three phases meet. Our theory demonstrates that when grooves are sufficiently deep their eigenvalues of the local slip length tensor depend only on μ /μg ,δ , and α , but not on the depth. The eigenvalues of the local slip length of shallow grooves depend on μ /μg and e (y ,α ) , although the contribution of the bevel angle is moderate. In order to assess the validity of our theory we propose an approach to solve the two-phase hydrodynamic problem, which significantly facilitates and accelerates calculations compared to conventional numerical schemes. The numerical results show that our simple analytical description obtained for limiting cases of deep and shallow grooves remains valid for various unidirectional textures.

  5. Variation with interplanetary sector of the total magnetic field measured at the OGO 2, 4, and 6 satellites

    NASA Technical Reports Server (NTRS)

    Langel, R. A.

    1973-01-01

    Variations in the scalar magnetic field (delta B) from the polar orbiting OGO 2, 4, and 6 spacecraft are examined as a function of altitude for times when the interplanetary magnetic field is toward the sun and for times when the interplanetary magnetic field away from the sun. This morphology is basically the same as that found when all data, irrespective of interplanetary magnetic sector, are averaged together. Differences in delta B occur, both between sectors and between seasons, which are similar in nature to variations in the surface delta Z found by Langel (1973c). The altitude variation of delta B at sunlit local times, together with delta Z at the earth's surface, demonstrates that the delta Z and delta B which varies with sector has an ionospheric source. Langel (1973b) showed that the positive delta B region in the dark portion of the hemisphere is due to at least two sources, the westward electrojet and an unidentified non-ionospheric source(s). Comparison of magnetic variations between season/sector at the surface and at the satellite, in the dark portion of the hemisphere, indicates that these variations are caused by variations in the latitudinally narrow electrojet currents and not by variations in the non-ionospheric source of delta B.

  6. Boundary-value problem for plasma centrifuge at arbitrary magnetic Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Wilhelm, H. E.; Hong, S. H.

    1977-01-01

    We solve in closed form the boundary-value problem for the partial differential equations which describe the (azimuthal) rotation velocity and induced magnetic fields in a cylindrical plasma centrifuge with ring electrodes of different radii and an external, axial magnetic field. The electric field, current density, and velocity distributions are discussed in terms of the Hartmann number H and the magnetic Reynolds number R. For small Hall coefficients, the induced magnetic field does not affect the plasma rotation. As a result of the Lorentz forces, the plasma rotates with speeds as high as 100,000 cm/sec around its axis of symmetry at typical conditions, so that the lighter (heavier) ion and atom components are enriched at (off) the center of the discharge cylinder.

  7. Micromagnetic simulation of anisotropic grain boundary diffusion for sintered Nd-Fe-B magnets

    NASA Astrophysics Data System (ADS)

    Li, W.; Zhou, Q.; Zhao, L. Z.; Wang, Q. X.; Zhong, X. C.; Liu, Z. W.

    2018-04-01

    A systematic investigation on the anisotropic grain boundary diffusion in sintered Nd-Fe-B magnets is carried out by micromagnetic simulation. The results indicate that the critical reason for the anisotropic diffusion effect is not the difference in the amount of Dy diffused along different directions but the macroscopic demagnetizing field. The diffusion parallel to the easy axis from both pole surfaces of the magnet can increase the nucleation fields in the two major regions with large macroscopic demagnetizing fields, where the reverse domains can nucleate easily. As a consequence, the grain boundary diffusion along the directions parallel to the easy axis from two pole surfaces is more effective to improve the coercivity of the magnets than that along other directions. It is also found that, to enhance the coercivity, only a limited diffusion depth is required. The present result is in good agreement with the recent experimental findings.

  8. Suppression of large edge-localized modes in high-confinement DIII-D plasmas with a stochastic magnetic boundary.

    PubMed

    Evans, T E; Moyer, R A; Thomas, P R; Watkins, J G; Osborne, T H; Boedo, J A; Doyle, E J; Fenstermacher, M E; Finken, K H; Groebner, R J; Groth, M; Harris, J H; La Haye, R J; Lasnier, C J; Masuzaki, S; Ohyabu, N; Pretty, D G; Rhodes, T L; Reimerdes, H; Rudakov, D L; Schaffer, M J; Wang, G; Zeng, L

    2004-06-11

    A stochastic magnetic boundary, produced by an applied edge resonant magnetic perturbation, is used to suppress most large edge-localized modes (ELMs) in high confinement (H-mode) plasmas. The resulting H mode displays rapid, small oscillations with a bursty character modulated by a coherent 130 Hz envelope. The H mode transport barrier and core confinement are unaffected by the stochastic boundary, despite a threefold drop in the toroidal rotation. These results demonstrate that stochastic boundaries are compatible with H modes and may be attractive for ELM control in next-step fusion tokamaks.

  9. Three Dimensional Sector Design with Optimal Number of Sectors

    NASA Technical Reports Server (NTRS)

    Xue, Min

    2010-01-01

    In the national airspace system, sectors get overloaded due to high traffic demand and inefficient airspace designs. Overloads can be eliminated in some cases by redesigning sector boundaries. This paper extends the Voronoi-based sector design method by automatically selecting the number of sectors, allowing three-dimensional partitions, and enforcing traffic pattern conformance. The method was used to design sectors at Fort-Worth and Indianapolis centers for current traffic scenarios. Results show that new designs can eliminate overloaded sectors, although not in all cases, reduce the number of necessary sectors, and conform to major traffic patterns. Overall, the new methodology produces enhanced and efficient sector designs.

  10. Satellite Tidal Magnetic Signals Constrain Oceanic Lithosphere-Asthenosphere Boundary Earth Tomography with Tidal Magnetic Signals

    NASA Technical Reports Server (NTRS)

    Grayver, Alexander V.; Schnepf, Neesha R.; Kuvshinov, Alexey V.; Sabaka, Terence J.; Chandrasekharan, Manoj; Olsen, Niles

    2016-01-01

    The tidal flow of electrically conductive oceans through the geomagnetic field results in the generation of secondary magnetic signals, which provide information on the subsurface structure. Data from the new generation of satellites were shown to contain magnetic signals due to tidal flow; however, there are no reports that these signals have been used to infer subsurface structure. Here we use satellite-detected tidal magnetic fields to image the global electrical structure of the oceanic lithosphere and upper mantle down to a depth of about 250 km. The model derived from more than 12 years of satellite data reveals an Approximately 72 km thick upper resistive layer followed by a sharp increase in electrical conductivity likely associated with the lithosphere-asthenosphere boundary, which separates colder rigid oceanic plates from the ductile and hotter asthenosphere.

  11. Re-exchange of Fe and Cu at the interface in sintered Nd-Fe-B magnets: A method to eliminate Fe precipitation at grain boundaries

    NASA Astrophysics Data System (ADS)

    Yang, YuQi; Si, HengGang; Yang, Hao; Zhang, Lan; Huang, DongFang; Chen, BaiYi; Xu, Fang; Hu, YongMei; Han, BaoJun

    2018-01-01

    According to the decoupling hypothesis for magnetic grains, the coercivity in sintered Nd-Fe-B magnets is increased after Cu doping, which is due to the formation of non-magnetic grain boundaries. However, this method partially fails, and ferromagnetic Fe-segregation occurs at the grain boundary. We discovered both experimentally and through calculation that the Fe content at the grain boundaries can be tuned across a wide range by introducing another element of Ag. Segregated Fe at high temperature at the grain boundary re-dissolves into Nd2Fe14B grains during annealing at low temperature. Both configurable and magnetic entropies contribute a large driving force for the formation of nonmagnetic grain boundaries. Almost zero Fe content could be achieved at the grain boundaries of sintered Nd-Fe-B magnet.

  12. Topology of magnetic flux ropes and formation of fossil flux transfer events and boundary layer plasmas

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Ma, Z. W.; Fu, Z. F.; Otto, A.

    1993-01-01

    A mechanism for the formation of fossil flux transfer events and the low-level boundary layer within the framework of multiple X-line reconnection is proposed. Attention is given to conditions for which the bulk of magnetic flux in a flux rope of finite extent has a simple magnetic topology, where the four possible connections of magnetic field lines are: IMF to MSP, MSP to IMF, IMF to IMF, and MSP to MSP. For a sufficient relative shift of the X lines, magnetic flux may enter a flux rope from the magnetosphere and exit into the magnetosphere. This process leads to the formation of magnetic flux ropes which contain a considerable amount of magnetosheath plasma on closed magnetospheric field lines. This process is discussed as a possible explanation for the formation of fossil flux transfer events in the magnetosphere and the formation of the low-latitude boundary layer.

  13. Demonstration of magnetic domain boundary movement using an easily assembled videocam-microscope system

    NASA Technical Reports Server (NTRS)

    Patterson, John W.

    1992-01-01

    The objectives are to build and demonstrate a low cost and highly flexible TV microscope facility and then use it to view the motion of magnetic domain boundaries as the local magnetic field is varied. The expense of an optical microscope and the videocam adapters sold for them is largely avoided by using the facility described below. The equipment, supplies, and procedure are presented.

  14. Boundary value problem for the solution of magnetic cutoff rigidities and some special applications

    NASA Technical Reports Server (NTRS)

    Edmonds, Larry

    1987-01-01

    Since a planet's magnetic field can sometimes provide a spacecraft with some protection against cosmic ray and solar flare particles, it is important to be able to quantify this protection. This is done by calculating cutoff rigidities. An alternate to the conventional method (particle trajectory tracing) is introduced, which is to treat the problem as a boundary value problem. In this approach trajectory tracing is only needed to supply boundary conditions. In some special cases, trajectory tracing is not needed at all because the problem can be solved analytically. A differential equation governing cutoff rigidities is derived for static magnetic fields. The presense of solid objects, which can block a trajectory and other force fields are not included. A few qualititative comments, on existence and uniqueness of solutions, are made which may be useful when deciding how the boundary conditions should be set up. Also included are topics on axially symmetric fields.

  15. 3D measurements and simulations of ion and neutral velocity distribution functions in a magnetized plasma boundary

    NASA Astrophysics Data System (ADS)

    Thompson, Derek S.; Keniley, Shane; Curreli, Davide; Henriquez, Miguel F.; Caron, David D.; Jemiolo, Andrew J.; McLaughlin, Jacob W.; Dufor, Mikal T.; Neal, Luke A.; Scime, Earl E.; Siddiqui, M. Umair

    2017-10-01

    We present progress toward the first paired 3D laser induced fluorescence measurements of ion and neutral velocity distribution functions (I/NVDFs) in a magnetized plasma boundary. These measurements are performed in the presheath region of an absorbing boundary immersed in a background magnetic field that is obliquely incident to the boundary surface (ψ =74°). Parallel and perpendicular flow measurements demonstrate that cross-field ion flows occur and that ions within several gyro-radii of the surface are accelerated in the E-> × B-> direction. We present electrostatic probe measurements of electron temperature, plasma density, and electric potential in the same region. Ion, neutral and electron measurements are compared to Boltzmann simulations, allowing direct comparison between measured and theoretical distribution functions in the boundary region. NSF PHYS 1360278.

  16. Models, assumptions, and experimental tests of flows near boundaries in magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Siddiqui, M. Umair; Thompson, Derek S.; Jackson, Cory D.; Kim, Justin F.; Hershkowitz, Noah; Scime, Earl E.

    2016-05-01

    We present the first measurements of ion flows in three dimensions (3Ds) using laser-induced fluorescence in the plasma boundary region. Measurements are performed upstream from a grounded stainless steel limiter plate at various angles ( ψ=16 ° to 80 ° ) to the background magnetic field in two argon helicon experiments (MARIA at the University of Wisconsin-Madison and HELIX at West Virginia University). The Chodura magnetic presheath model for collisionless plasmas [R. Chodura, Phys. Fluids 25, 1628 (1982)] is shown to be inaccurate for systems with sufficient ion-neutral collisions and ionization such as tokamak scrape off layers. A 3D ion fluid model that accounts for ionization and charge-exchange collisions is found to accurately describe the measured ion flows in regions where the ion flux tubes do not intersect the boundary. Ion acceleration in the E →×B → direction is observed within a few ion Larmor radii of the grounded plate for ψ=80 ° . We argue that fully 3D ion and neutral acceleration in the plasma boundary are uniquely caused by the long-range presheath electric fields, and that models that omit presheath effects under-predict observed wall erosion in tokamak divertors and Hall thruster channel walls.

  17. The Tectonic Boundary Between Eastern Subbaisin and South-West Subbasin of the South China Sea Revealed from the Normalized Magnetic Source Strength

    NASA Astrophysics Data System (ADS)

    Guo, L.; Meng, X.

    2014-12-01

    The South China Sea (SCS), surrounded by the Eurasia, Pacific and India-Australia plates, is one of the largest marginal seas in the Western Pacific. It was formed by the interaction of the three plates and the seafloor spreading during Late Oligocene time to Early Miocene time. The boundary between Eastern Subbaisin and South-west Subbasin of the SCS has long been debated in the literature. Refining the boundary is one of the crucial tasks for correctly understanding the seafloor spreading model of the SCS. Due to few drills on the deep ocean basin of the SCS, magnetic data become important information for refining the boundary. However, the interpretation of magnetic data in the SCS suffers from the remanent magnetization of ocean crust as well as igneous rock and seamounts. The conventional reduction-to-pole anomalies at low latitudes usually neglect the remanent magnetization, making the interpretation incorrect. Here, we assembled high-resolution total magnetic intensity (TMI) data around the ocean basin of the SCS, and then did a special transformation of the TMI anomalies with a varying magnetic inclinations algorithm to obtain the normalized source strength (NSS). The NSS has advantage of insensitivity to remanent magnetization, benefitting correct interpretation. The NSS presents discriminative features from east to west in the ocean basin. The boundary of the discriminative features is clear and just ranges from the northeastern edge of the Zhongsha Islands running in the southeast direction to the northeastern edge of the Reed Bank. These imply that magnetic structure and tectonic features in the crust are discriminative between both sides of this boundary. It can be deduced that this boundary is the tectonic boundary between Eastern Subbaisin and South-west Subbasin. We acknowledge the financial support of the National Natural Science Foundation of China (41374093) and the SinoProbe-01-05 project.

  18. Dynamically Evolving Sectors for Convective Weather Impact

    NASA Technical Reports Server (NTRS)

    Drew, Michael C.

    2010-01-01

    A new strategy for altering existing sector boundaries in response to blocking convective weather is presented. This method seeks to improve the reduced capacity of sectors directly affected by weather by moving boundaries in a direction that offers the greatest capacity improvement. The boundary deformations are shared by neighboring sectors within the region in a manner that preserves their shapes and sizes as much as possible. This reduces the controller workload involved with learning new sector designs. The algorithm that produces the altered sectors is based on a force-deflection mesh model that needs only nominal traffic patterns and the shape of the blocking weather for input. It does not require weather-affected traffic patterns that would have to be predicted by simulation. When compared to an existing optimal sector design method, the sectors produced by the new algorithm are more similar to the original sector shapes, resulting in sectors that may be more suitable for operational use because the change is not as drastic. Also, preliminary results show that this method produces sectors that can equitably distribute the workload of rerouted weather-affected traffic throughout the region where inclement weather is present. This is demonstrated by sector aircraft count distributions of simulated traffic in weather-affected regions.

  19. Low-energy planar magnetic defects in BaFe2As2: Nanotwins, twins, antiphase, and domain boundaries

    SciTech Connect

    Khan, S. N.; Alam, A.; Johnson, Duane D.

    2013-01-01

    In BaFe2As2, structural and magnetic planar defects begin to proliferate below the structural phase transition, affecting descriptions of magnetism and superconductivity.We study, using density-functional theory, the stability and magnetic properties of competing antiphase and domain boundaries, twins and isolated nanotwins (twin nuclei), and spin excitations proposed and/or observed. These nanoscale defects have a very low surface energy (22 210 m Jm 2), with twins favorable to the mesoscale. Defects exhibit smaller moments confined near their boundaries making a uniform-moment picture inappropriate for long-range magnetic order in real samples. Nanotwins explain features in measured pair distribution functions so should be consideredmore » when analyzing scattering data. All these defects can be weakly mobile and/or can have fluctuations that lower« less

  20. Using sustainability as a collaboration magnet to encourage multi-sector collaborations for health.

    PubMed

    Khayatzadeh-Mahani, Akram; Labonté, Ronald; Ruckert, Arne; de Leeuw, Evelyne

    2017-03-01

    The World Health Organization Commission on Social Determinants of Health (SDH) places great emphasis on the role of multi-sector collaboration in addressing SDH. Despite this emphasis on this need, there is surprisingly little evidence for this to advance health equity goals. One way to encourage more successful multi-sector collaborations is anchoring SDH discourse around 'sustainability', subordinating within it the ethical and empirical importance of 'levelling up'. Sustainability, in contrast to health equity, has recently proved to be an effective collaboration magnet. The recent adoption of the Sustainable Development Goals (SDGs) provides an opportunity for novel ways of ideationally re-framing SDH discussions through the notion of sustainability. The 2030 Agenda for the SDGs calls for greater policy coherence across sectors to advance on the goals and targets. The expectation is that diverse sectors are more likely and willing to collaborate with each other around the SDGs, the core idea of which is 'sustainability'.

  1. The Formation of Magnetic Depletions and Flux Annihilation Due to Reconnection in the Heliosheath

    SciTech Connect

    Drake, J. F.; Swisdak, M.; Opher, M.

    The misalignment of the solar rotation axis and the magnetic axis of the Sun produces a periodic reversal of the Parker spiral magnetic field and the sectored solar wind. The compression of the sectors is expected to lead to reconnection in the heliosheath (HS). We present particle-in-cell simulations of the sectored HS that reflect the plasma environment along the Voyager 1 and 2 trajectories, specifically including unequal positive and negative azimuthal magnetic flux as seen in the Voyager data. Reconnection proceeds on individual current sheets until islands on adjacent current layers merge. At late time, bands of the dominant fluxmore » survive, separated by bands of deep magnetic field depletion. The ambient plasma pressure supports the strong magnetic pressure variation so that pressure is anticorrelated with magnetic field strength. There is little variation in the magnetic field direction across the boundaries of the magnetic depressions. At irregular intervals within the magnetic depressions are long-lived pairs of magnetic islands where the magnetic field direction reverses so that spacecraft data would reveal sharp magnetic field depressions with only occasional crossings with jumps in magnetic field direction. This is typical of the magnetic field data from the Voyager spacecraft. Voyager 2 data reveal that fluctuations in the density and magnetic field strength are anticorrelated in the sector zone, as expected from reconnection, but not in unipolar regions. The consequence of the annihilation of subdominant flux is a sharp reduction in the number of sectors and a loss in magnetic flux, as documented from the Voyager 1 magnetic field and flow data.« less

  2. Penetration boundary of solar cosmic rays into the earth's magnetosphere during magnetically quiet times

    SciTech Connect

    Biryukov, A.S.; Ivanova, T.A.; Kovrygina, L.M.

    1984-05-01

    Data is used from the satellites Interkosmos-17 and Kosmos-900 to determine penetration boundaries at high latitudes in the earth's magnetosphere. Considered are the results of observations of the penetration boundary of solar cosmic ray (SCR) protons and electrons during an SCR increase on November 22-25, 1977. The position of the SCR penetration boundary during a single increase at practically all values of MLT in quiet conditions is examined. Magnetospheric structure is determined in the region of closed drift shells where the magnetic field is asymmetric. The authors can estimate how the solar wind pressure affects the magnetosphere by using datamore » on the penetration boundaries of solar protons obtained during quiet geomagnetic conditions.« less

  3. Plasmapause Boundary Dynamics and the Interplanetary Magnetic Field Effect

    NASA Astrophysics Data System (ADS)

    Goldstein, J.

    2006-05-01

    The plasmapause is the outer boundary of the plasmasphere, the roughly toroidal region of cold, dense, corotating plasma that encircles the Earth and can extend several Earth radii (RE) out into space. The source of plasma in this region is ionospheric outflow (or upflow), which fills plasmaspheric field lines with a mixture of protons, helium ions, and oxygen ions on a timescale of several days. A distinct outer plasmapause boundary forms when plasmaspheric plasma is removed, a process known as erosion. Plasmaspheric erosion occurs most strongly during times of southward interplanetary magnetic field (IMF), when magnetospheric convection is greatly enhanced. Decades of theory and observation support the idea that enhanced sunward convection (during southward IMF) forms large plumes of dense plasma that stretch sunward from the main plasmasphere during erosion. The plasmapause during erosion events is distorted: reduced on the nightside, elongated on the dayside, and in general, overlapping the boundaries of regions of warmer plasmas (such as the ring current and radiation belts) that experience increased loss rates from wave-particle interactions in the overlap regions. Thus, the plasmapause boundary is of critical importance to the global dynamics of these warmer particles. In recent years, the southward IMF (i.e., convection) effect on the plasmapause has been fairly well characterized, but what has received less attention is the northward IMF effect. What happens at the plasmapause boundary following disturbances, when convection is reduced but ionospheric outflow has not yet had enough time to refill the plasmaspheric flux tubes? Observations by CRRES, Polar, IMAGE, Cluster, and other spacecraft have shown a bewildering variety of fine-scale plasmapause density structure during recovery and deep quiet phases. Many plasmapause features have been classified, sorted and named, but nonetheless, remain unexplained. This paper will present our current understanding

  4. Magnetic anomalies in East Antarctica: a window on major tectonic provinces and their boundaries

    USGS Publications Warehouse

    Golynsky, A.V.

    2007-01-01

    An analysis of aeromagnetic data compiled within the Antarctic Digital Magnetic Anomaly Project (ADMAP) yields significant new insight into major tectonic provinces of East Antarctica. Several previously unknown crustal blocks are imaged in the deep interior of the continent, which are interpreted as cratonic nuclei. These cratons are fringed by a large and continuous orogenic belt between Coats Land and Princess Elizabeth Land, with possible branches in the deeper interior of East Antarctica. Most of the crustal provinces and boundaries identified in this study are only in part exposed. More detailed analyses of these crustal provinces and their tectonic boundaries would require systematic acquisition of additional high-resolution magnetic data, because at present the ADMAP database is largely inadequate to address many remaining questions regarding Antarctica’s tectonic evolution.

  5. Influence of interplanetary solar wind sector polarity on the ionosphere

    NASA Astrophysics Data System (ADS)

    liu, jing

    2014-05-01

    Knowledge of solar sector polarity effects on the ionosphere may provide some clues in understanding of the ionospheric day-to-day variability. A solar-terrestrial connection ranging from solar sector boundary (SB) crossings, geomagnetic disturbance and ionospheric perturbations has been demonstrated. The increases in interplanetary solar wind speed within three days are seen after SB crossings, while the decreases in solar wind dynamic pressure and magnetic field intensity immediately after SB crossings are confirmed by the superposed epoch analysis results. Furthermore, the interplanetary magnetic field (IMF) Bz component turns from northward to southward in March equinox and June solstice as the Earth passes from a solar sector of outward to inward directed magnetic fields, whereas the reverse situation occurs for the transition from toward to away sectors. The F2 region critical frequency (foF2) covering about four solar cycles and total electron content (TEC) during 1998-2011 are utilized to extract the related information, revealing that they are not modified significantly and vary within the range of 15% on average. The responses of the ionospheric TEC to SB crossings exhibit complex temporal and spatial variations and have strong dependencies on season, latitude, and solar cycle. This effect is more appreciable in equinoctial months than in solstitial months, which is mainly caused by larger southward Bz components in equinox. In September equinox, latitudinal profile of relative variations of foF2 at noon is featured by depressions at high latitudes and enhancements in low-equatorial latitudes during IMF away sectors. The negative phase of foF2 is delayed at solar minimum relative to it during other parts of solar cycle, which might be associated with the difference in longevity of major interplanetary solar wind drivers perturbing the Earth's environment in different phases of solar cycle.

  6. The double layers in the plasma sheet boundary layer during magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Guo, J.; Yu, B.

    2014-11-01

    We studied the evolutions of double layers which appear after the magnetic reconnection through two-dimensional electromagnetic particle-in-cell simulation. The simulation results show that the double layers are formed in the plasma sheet boundary layer after magnetic reconnection. At first, the double layers which have unipolar structures are formed. And then the double layers turn into bipolar structures, which will couple with another new weak bipolar structure. Thus a new double layer or tripolar structure comes into being. The double layers found in our work are about several ten Debye lengths, which accords with the observation results. It is suggested that the electron beam formed during the magnetic reconnection is responsible for the production of the double layers.

  7. Maghemite-to-magnetite reduction across the Fe-redox boundary in a sediment core from the Ontong-Java Plateau: influence on relative palaeointensity estimation and environmental magnetic application

    NASA Astrophysics Data System (ADS)

    Yamazaki, Toshitsugu; Solheid, Peter

    2011-06-01

    During reduction diagenesis, production of dissolved Fe2+ by reduction of ferric oxide starts at the Fe-redox boundary. The associated magnetic property changes may influence palaeomagnetic and environmental magnetic records of marine sediments, however, this has not been evaluated thoroughly. In this study, using a gravity core from the Ontong-Java Plateau, we document in detail rock magnetic changes across the Fe-redox boundary, and investigate their influence on relative palaeointensity estimation and on a magnetic proxy for the proportion of terrigenous/biogenic magnetic minerals. The magnetic mineral assemblage above the Fe-redox boundary is characterized by a component with a mean coercivity of ˜100 mT in isothermal remanent magnetization (IRM) component analyses and low S-ratios (S-0.1T). Low-temperature IRM measurements and Mössbauer spectroscopy indicate that the degree of maghemitization is higher above the Fe-redox boundary. From these observations, we conclude that reduction of maghemite to magnetite occurs at the Fe-redox boundary, and we infer that a maghemite skin on magnetic grains is lost across the boundary. Relative palaeointensity variations obtained by normalizing NRM intensity with SIRM agree well with regional and global palaeointensity stacks, which suggests that relative palaeointensity estimation is not significantly affected by the Fe-redox boundary. Temporal variations of the ratio of anhysteretic remanent magnetization susceptibility and saturation IRM (χARM/SIRM) coincide with the regional pattern across the Ontong-Java Plateau. It is also possible to estimate variations in the proportion of terrigenous to biogenic components using the χARM/SIRM ratio across the Fe-redox boundary.

  8. Effect of oxygen content of Nd-Fe-B sintered magnet on grain boundary diffusion process of DyH2 dip-coating

    NASA Astrophysics Data System (ADS)

    Bae, Kyoung-Hoon; Lee, Seong-Rae; Kim, Hyo-Jun; Lee, Min-Woo; Jang, Tae-Suk

    2015-11-01

    We investigated the effect of oxygen content on the microstructural and magnetic properties of a DyH2 dip-coated Nd-Fe-B sintered magnet. When the magnet had a low oxygen content (1500 ppm), the volume and size of the rare-earth-rich oxide (Nd-Dy-O) phase was reduced, and a uniform and continuous thin Nd-rich grain boundary phase (GBP) was well developed. The grain boundary diffusion depth of Dy increased from 200 to 350 μm with decreasing oxygen content from ˜3000 to 1500 ppm. The coercivity of the low-oxygen magnet increased from 19.98 to 23.59 kOe after grain boundary diffusion process (GBDP) while the remanence reduction was minimized. The formation of an fcc-NdOx Nd-rich phase in the high-oxygen magnet hindered the formation of a Nd-rich triple-junction phase and GBP. In contrast, a metallic dhcp-Nd phase, which was closely related to coercivity enhancement after GBDP, was formed in the low-oxygen magnet.

  9. Analysis of the electrolyte convection inside the concentration boundary layer during structured electrodeposition of copper in high magnetic gradient fields.

    PubMed

    König, Jörg; Tschulik, Kristina; Büttner, Lars; Uhlemann, Margitta; Czarske, Jürgen

    2013-03-19

    To experimentally reveal the correlation between electrodeposited structure and electrolyte convection induced inside the concentration boundary layer, a highly inhomogeneous magnetic field, generated by a magnetized Fe-wire, has been applied to an electrochemical system. The influence of Lorentz and magnetic field gradient force to the local transport phenomena of copper ions has been studied using a novel two-component laser Doppler velocity profile sensor. With this sensor, the electrolyte convection within 500 μm of a horizontally aligned cathode is presented. The electrode-normal two-component velocity profiles below the electrodeposited structure show that electrolyte convection is induced and directed toward the rim of the Fe-wire. The measured deposited structure directly correlates to the observed boundary layer flow. As the local concentration of Cu(2+) ions is enhanced due to the induced convection, maximum deposit thicknesses can be found at the rim of the Fe-wire. Furthermore, a complex boundary layer flow structure was determined, indicating that electrolyte convection of second order is induced. Moreover, the Lorentz force-driven convection rapidly vanishes, while the electrolyte convection induced by the magnetic field gradient force is preserved much longer. The progress for research is the first direct experimental proof of the electrolyte convection inside the concentration boundary layer that correlates to the deposited structure and reveals that the magnetic field gradient force is responsible for the observed structuring effect.

  10. 3D ion flow measurements and simulations near a boundary at oblique incidence to a magnetic field

    NASA Astrophysics Data System (ADS)

    Thompson, Derek S.; Keniley, Shane; Khaziev, Rinat; Curreli, Davide; Good, Timothy N.; Henriquez, Miguel; McIlvain, Julianne; Siddiqui, M. Umair; Scime, Earl E.

    2016-10-01

    Boundaries at oblique incidence to magnetic fields are abundant in magnetic confinement plasmas. The ion dynamics near these boundaries has implications for applications such as tokamak divertor wall loading and Hall thruster channel erosion. We present 3D, non-perturbative measurements of ion velocity distribution functions (IVDFs), providing ion temperatures and flows upstream of a grounded stainless steel limiter plate immersed in an argon plasma, oriented obliquely to the background axial magnetic field (ψ = 74°). The spatial resolution of the measurements is sufficient to probe the kinetic details of magnetic presheath structures, which span several ion Larmor radii ( 1 cm). Furthermore, we report probe measurements of electron density and temperature, and of local electric potential. To complement these measurements, results from particle-in-cell and Boltzmann models of the same region are presented. These models allow for point-to-point comparison of simulated and measured electrostatic structures and IVDFs at high spatial resolution. NSF Award PHYS-1360278.

  11. Change in the magnetic structure of (Bi,Sm)FeO3 thin films at the morphotropic phase boundary probed by neutron diffraction

    NASA Astrophysics Data System (ADS)

    Maruyama, Shingo; Anbusathaiah, Varatharajan; Fennell, Amy; Enderle, Mechthild; Takeuchi, Ichiro; Ratcliff, William D.

    2014-11-01

    We report on the evolution of the magnetic structure of BiFeO3 thin films grown on SrTiO3 substrates as a function of Sm doping. We determined the magnetic structure using neutron diffraction. We found that as Sm increases, the magnetic structure evolves from a cycloid to a G-type antiferromagnet at the morphotropic phase boundary, where there is a large piezoelectric response due to an electric-field induced structural transition. The occurrence of the magnetic structural transition at the morphotropic phase boundary offers another route towards room temperature multiferroic devices.

  12. Grain boundary diffusion behaviors in hot-deformed Nd2Fe14B magnets by PrNd-Cu low eutectic alloys

    NASA Astrophysics Data System (ADS)

    Tang, Xu; Chen, Renjie; Li, Ming; Jin, Chaoxiang; Yin, Wenzong; Lee, Don; Yan, Aru

    2018-01-01

    High coercivity of hot-deformed Nd2Fe14B magnets was obtained by grain boundary diffusion. Comparable squareness and similar magnetic properties for samples diffusing from side and pole surfaces show little discrepancies if quantities of the infiltrated PrNd-Cu low eutectic alloys is enough to obtain sufficient diffusion. However, the microstructures and higher characteristic peak ratios show preferable orientation of grains near surfaces of the sample diffused from side surfaces than that from pole surfaces. Amorphous Nd-rich phases and crystal Fe-rich phases were both observed in the diffused magnets. The enhancement of coercivity is considered to be resulted from grain boundary optimization and magnetic isolation which is caused by the thickened nonmagnetic intergranular phases.

  13. An observational search for large-scale organization of five-minute oscillations on the sun. [coronal holes or sector structure relationships

    NASA Technical Reports Server (NTRS)

    Dittmer, P. H.; Scherrer, P. H.; Wilcox, J. M.

    1978-01-01

    The large-scale solar velocity field has been measured over an aperture of radius 0.8 solar radii on 121 days between April and September, 1976. Measurements are made in the line Fe I 5123.730 A, employing a velocity subtraction technique similar to that of Severny et al. (1976). Comparisons of the amplitude and frequency of the five-minute resonant oscillation with the geomagnetic C9 index and magnetic sector boundaries show no evidence of any relationship between the oscillations and coronal holes or sector structure.

  14. Direct comparison of neutral velocity distribution measurements and simulations in the vicinity of an absorbing boundary oblique to a magnetic field

    NASA Astrophysics Data System (ADS)

    Henriquez, Miguel F.; Thompson, Derek S.; Keniley, Shane; Curreli, Davide; Steinberger, Thomas E.; Caron, David D.; Jemiolo, Andrew J.; McLaughlin, Jacob W.; Dufor, Mikal T.; Neal, Luke A.; Scime, Earl E.; Siddiqui, M. Umair

    2017-10-01

    Plasma-boundary interactions are strongly affected by the sheath and presheath structures that form near the boundary surface. Recent measurements have observed ion transport across magnetic field lines in regions where the surface is oblique to the background magnetic field (ψ =74°) . In these boundary regions, charge exchange collisions may provide a mechanism through which neutral particles interact with the long distance presheath electric field. We report efforts to directly compare Boltzmann and particle-in-cell simulations with 3D neutral velocity distribution functions (NVDFs) using laser induced fluorescence (LIF) in a magnetized plasma boundary region. We present a novel LIF method for measuring Ar-II metastable velocity distributions, in which we observe the 738.6014 nm fluorescence (2p3 to 1s4 in Paschen's notation), that results from absorption of the 706.9167 nm (1s5 metastable to 2p3) pump laser, providing neutral temperatures and flows. We additionally describe electrostatic probe measurements in the same region.

  15. Interaction of solar wind with the magnetopause-boundary layer and generation of magnetic impulse events

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Wei, C. Q.

    1993-01-01

    The transport of mass, momentum, energy and waves from the solar wind to the Earth's magnetosphere takes place in the magnetopause-boundary layer region. Various plasma processes that may occur in this region have been proposed and studied. In this paper, we present a brief review of the plasma processes in the dayside magnetopause-boundary layer. These processes include (1) flux transfer events at the dayside magnetopause, (2) formation of plasma vortices in the low-latitude boundary layer by the Kelvin-Helmholtz instability and coupling to the polar ionosphere, (3) the response of the magnetopause to the solar wind dynamic pressure pulses, and (4) the impulsive penetration of solar wind plasma filaments through the dayside magnetopause into the magnetospheric boundary layer. Through the coupling of the magnetopause-boundary layer to the polar ionosphere, those above processes may lead to occurrence of magnetic impulse events observed in the high-latitude stations.

  16. Apparent relationship between solar-sector boundaries and 300-mb vorticity: Possible explanation in terms of upward propagation of planetary-scale waves

    NASA Technical Reports Server (NTRS)

    Deland, R. J.

    1974-01-01

    The selection process for sector structure boundary crossings used in vorticity correlation studies is examined and the possible influence of ascending planetary scale waves is assessed. It is proposed that some of the observed correlations between geomagnetic and meteorological variations may be due to meteorological effects on the geometric variables, rather than due to common solar origin.

  17. Characterization of a turbomolecular-pumped magnetic sector mass spectrometer

    NASA Technical Reports Server (NTRS)

    Mehta, Narinder K.

    1988-01-01

    A Perkin Elmer MGA-1200, turbomolecular-pumped, magnetic sector, multiple gas analyzer mass spectrometer with modified inlet for fast response was characterized for the analysis of hydrogen, helium, oxygen and argon in nitrogen and helium background gases. This instrument was specially modified for the Vanderberg AFB SLC-6 Hydrogen Disposal Test Program, as a part of the Hydrogen Sampling System (H2S2). Linearity, precision, drift, detection limits and accuracy among other analytical parameters for each of the background gas were studied to evaluate the performance of the instrument. The result demonstrates that H2S2 mass spectrometer is a stable instrument and can be utilized for the quantitative analytical determination of hydrogen, helium, oxygen and argon in nitrogen and helium background gases.

  18. The effect of guide-field and boundary conditions on collisionless magnetic reconnection in a stressed X-point collapse

    SciTech Connect

    Graf von der Pahlen, J.; Tsiklauri, D.

    2014-01-15

    Works of Tsiklauri and Haruki [Phys. Plasmas 15, 102902 (2008); 14, 112905 (2007)] are extended by inclusion of the out-of-plane magnetic (guide) field. In particular, magnetic reconnection during collisionless, stressed X-point collapse for varying out-of-plane guide-fields is studied using a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code. For zero guide-field, cases for both open and closed boundary conditions are investigated, where magnetic flux and particles are lost and conserved, respectively. It is found that reconnection rates, out-of-plane currents and density in the X-point increase more rapidly and peak sooner in the closed boundary case, but higher values are reachedmore » in the open boundary case. The normalized reconnection rate is fast: 0.10-0.25. In the open boundary case it is shown that an increase of guide-field yields later onsets in the reconnection peak rates, while in the closed boundary case initial peak rates occur sooner but are suppressed. The reconnection current changes similarly with increasing guide-field; however for low guide-fields the reconnection current increases, giving an optimal value for the guide-field between 0.1 and 0.2 times the in-plane field in both cases. Also, in the open boundary case, it is found that for guide-fields of the order of the in-plane magnetic field, the generation of electron vortices occurs. Possible causes of the vortex generation, based on the flow of decoupled particles in the diffusion region and localized plasma heating, are discussed. Before peak reconnection onset, oscillations in the out-of-plane electric field at the X-point are found, ranging in frequency from approximately 1 to 2 ω{sub pe} and coinciding with oscillatory reconnection. These oscillations are found to be part of a larger wave pattern in the simulation domain. Mapping the out-of-plane electric field along the central lines of the domain over time and applying a 2D Fourier transform

  19. Sources of magnetic fields in recurrent interplanetary streams

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Behannon, K. W.; Hansen, S. F.; Pneuman, G. W.; Feldman, W. C.

    1978-01-01

    The paper examines sources of magnetic fields in recurrent streams observed by the Imp 8 and Heos spacecraft at 1 AU and by Mariner 10 en route to Mercury between October 31, 1973 and February 9, 1974, during Carrington rotations 1607-1610. Although most fields and plasmas at 1 AU were related to coronal holes and the magnetic field lines were open in those holes, some of the magnetic fields and plasmas at 1 AU were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines may be more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes, certain photospheric magnetic fields, and the coronal footprints of the sector boundaries on the source surface are characterized.

  20. Formation of a three-dimensional plasma boundary after decay of the plasma response to resonant magnetic perturbation fields

    NASA Astrophysics Data System (ADS)

    Schmitz, O.; Evans, T. E.; Fenstermacher, M. E.; Lanctot, M. J.; Lasnier, C. L.; Mordijck, S.; Moyer, R. A.; Reimerdes, H.; the DIII-D Team

    2014-01-01

    First time experimental evidence is presented for a direct link between the decay of a n = 3 plasma response and the formation of a three-dimensional (3D) plasma boundary. We inspect a lower single-null L-mode plasma which first reacts at sufficiently high rotation with an ideal resonant screening response to an external toroidal mode number n = 3 resonant magnetic perturbation field. Decay of this response due to reduced bulk plasma rotation changes the plasma state considerably. Signatures such as density pump out and a spin up of the edge rotation—which are usually connected to formation of a stochastic boundary—are detected. Coincident, striation of the divertor single ionized carbon emission and a 3D emission structure in double ionized carbon at the separatrix is seen. The striated C II pattern follows in this stage the perturbed magnetic footprint modelled without a plasma response (vacuum approach). This provides for the first time substantial experimental evidence, that a 3D plasma boundary with direct impact on the divertor particle flux pattern is formed as soon as the internal plasma response decays. The resulting divertor structure follows the vacuum modelled magnetic field topology. However, the inward extension of the perturbed boundary layer can still not directly be determined from these measurements.

  1. Effect of self-consistent magnetic field on plasma sheet penetration to the inner magnetosphere under enhanced convection: RCM simulations combined with force-balance magnetic field solver

    NASA Astrophysics Data System (ADS)

    Gkioulidou, M.; Wang, C.; Lyons, L. R.; Wolf, R. A.

    2010-12-01

    Transport of plasma sheet particles into the inner magnetosphere is strongly affected by the penetration of the convection electric field, which is the result of the large-scale magnetosphere-ionosphere electromagnetic coupling. This transport, on the other hand, results in plasma heating and magnetic field stretching, which become very significant in the inner plasma sheet (inside 20 RE). We have previously run simulations with the Rice Convection Model (RCM) to investigate how the earthward penetration of convection electric field, and therefore plasma sheet population, depends on plasma sheet boundary conditions. Outer boundary conditions at r ~20 RE are a function of MLT and interplanetary conditions based on 11 years of Geotail data. In the previous simulations, Tsyganenko 96 magnetic field model (T96) was used so force balance between plasma pressure and magnetic fields was not maintained. We have now integrated the RCM with a magnetic field solver (Liu et al., 2006) to obtain the required force balance in the equatorial plane. We have run the self-consistent simulations under enhanced convection with different boundary conditions in which we kept different parameters (flux tube particle content, plasma pressure, plasma beta, or magnetic fields) at the outer boundary to be MLT-dependent but time independent. Different boundary conditions result in qualitatively similar plasma sheet profiles. The results show that magnetic field has a dawn dusk asymmetry with field lines being more stretched in the pre-midnight sector, due to relatively higher plasma pressure there. The asymmetry in the magnetic fields in turn affects the radial distance and MLT of plasma sheet penetration into the inner magnetosphere. In comparison with results using the T96, plasma transport under self-consistent magnetic field results in proton and electron plasma sheet inner edges that are located in higher latitudes, weaker pressure gradients, and more efficient shielding of the near

  2. The MHD simulation of interplanetary space and heliosphere by using the boundary conditions of time-varying magnetic field and IPS-based plasma

    NASA Astrophysics Data System (ADS)

    Hayashi, K.; Tokumaru, M.; Kojima, M.; Fujiki, K.

    2008-12-01

    We present our new boundary treatment to introduce the temporal variation of the observation-based magnetic field and plasma parameters on the inner boundary sphere (at 30 to 50 Rs) to the MHD simulation of the interplanetary space and the simulation results. The boundary treatment to induce the time-variation of the magnetic field including the radial component is essentially same as shown in our previous AGU meetings and newly modified so that the model can also include the variation of the plasma variables detected by IPS (interplanetary scintillation) observation, a ground-based remote sensing technique for the solar wind plasma. We used the WSO (Wilcox Solar Observatory at Stanford University) for the solar magnetic field input. By using the time-varying boundary condition, smooth variations of heliospheric MHD variables during the several Carrington solar rotation period are obtained. The simulation movie will show how the changes in the inner heliosphere observable by the ground-based instrument propagate outward and affects the outer heliosphere. The simulated MHD variables are compared with the Ulysses in-situ measurement data including ones made during its travel from the Earth to Jupiter for validation, and we obtain better agreements than with the simulation with fixed boundary conditions.

  3. Eastern boundary of the Siletz terrane in the Puget Lowland from gravity and magnetic modeling with implications for seismic hazard analysis

    NASA Astrophysics Data System (ADS)

    Anderson, M. L.; Blakely, R. J.; Wells, R. E.; Dragovich, J.

    2011-12-01

    The forearc of the Cascadia subduction zone in coastal Oregon and Washington is largely composed of a 15-30 km-thick stack of basalt flows comprising the Crescent Formation (WA) and Siletz River Volcanics (OR), and collectively termed the Siletz terrane. We are developing 3-D structural maps of the Puget Lowland to distinguish older and currently active structures for seismic hazard analysis. The boundaries of the Siletz terrane in particular may strongly influence crustal rheology and neotectonic structures of the region. Careful analysis of the areal extent of this terrane will also facilitate more accurate interpretation of seismic data and gravity anomalies, which will help define the extent and shape of overlying basins. Absence of extensive outcrop in the Lowland and a widespread veneer of Quaternary deposits require extensive subsurface geophysical studies to establish Lowland-wide crustal structure. Previous studies have used active seismic surveys and interpretation of existing industry seismic data, with several studies using gravity and magnetic data or passive-source tomography support. However, steeply dipping boundaries in the mid-crust are difficult targets for seismic study. We need to independently discriminate between potential models established by seismic data using gravity and magnetic datasets. In the Puget Lowland the Siletz is a region of high seismic wave speed, density, and magnetic susceptibility, and therefore its mid-crustal boundaries are good targets for definition by gravity and magnetic data. We present interpretations of gravity and magnetic anomalies for the Puget Lowland region that together establish the most likely position and structure of the Crescent Formation boundary in the mid-upper crust. Well-constrained physical properties of Crescent basalts inform our aeromagnetic map interpretation and give us baseline values for constructing three two-dimensional models by simultaneous forward modeling of aeromagnetic and isostatic

  4. Magnetic phase boundaries of CsMnF3: XY-to-Ising crossover and the virtual bicritical point

    NASA Astrophysics Data System (ADS)

    Shapira, Y.; Oliveira, N. F., Jr.; Chang, T. S.

    1980-02-01

    The ordering temperature Tc of the easy-plane hexagonal antiferromagnet CsMnF3 was measured as a function of magnetic field H, up to 120 kOe. Tc was determined from the thermal expansion anomaly at constant H. At H=0, TN≡Tc(0)=51.4 K. When H--> is in the hexagonal plane, the boundary Tc(H) is bow shaped: with increasing H, Tc first increases, then passes through a maximum, and later decreases. The maximum Tc is ~37 mK above TN, and it occurs at H≅29.5 kOe. The bow-shaped phase boundary is attributed to the XY-to-Ising crossover which is induced by the magnetic field, as discussed by Fisher, Nelson, and Kosterlitz. Fits to the phase boundary Tc(H) give a crossover exponent φ=1.185+/-0.03 for one sample and φ=1.184+/-0.025 for another, compared to the theoretical value φ(n=2)=1.175+/-0.015. When H--> is perpendicular to the hexagonal plane, Tc decreases monotonically with increasing H, but the decrease is not in accordance with mean-field theory, which predicts a decrease proportional to H2. The deviation from mean-field behavior is attributed to a virtual bicritical point (VBP) with Heisenberg symmetry, which exists mathematically at a negative value of H2. Although the VBP cannot be observed directly, it affects the behavior in the observable region of H2>=0. Physically, a magnetic field applied perpendicular to the easy plane enhances the Heisenberg-to-XY symmetry breaking, which at H=0 is solely due to the weak easy-plane uniaxial anisotropy. The enhanced symmetry breaking causes a non-mean-field dependence of Tc on H. An equation derived on this basis gives a good description of the phase boundary Tc(H). This equation contains three adjustable parameters, two of which can also be estimated without recourse to the phase boundary Tc(H). The values for these two parameters obtained from a best fit to Tc(H) agree with the independent estimates.

  5. Magnetic Fe, Si, Al-Rich Impact Spherules from the P-T Boundary Layer at Graphite Peak, Antarctica

    NASA Technical Reports Server (NTRS)

    Petaev, M. I.; Jacobsen, S. B.; Basu, A. R.; Becker, L.

    2004-01-01

    The geological boundary between Triassic and Permian strata coincides with the greatest life extinction in the Earth's history. Although the cause of the extinction is still the subject of intense debates, recent discoveries in the P-T boundary layer of shocked quartz grains, fullerenes with the extraterrestrial noble gases, Fe metal nuggets, and chondritic meteorite fragments all point to a powerful collision of Earth with a celestial body in the late Permian. Here we report the discovery of magnetic Fe, Si, Al-rich impact spherules which accompany the chondritic meteorite fragments in some samples from the P-T boundary layer at Graphite Peak, Antarctica.

  6. Unsteady magnetohydrodynamics micropolar fluid in boundary layer flow past a sphere influenced by magnetic fluid

    NASA Astrophysics Data System (ADS)

    Pratomo, Rizky Verdyanto; Widodo, Basuki; Adzkiya, Dieky

    2017-12-01

    Research about fluid flow was very interesting because have a lot of advantages and it can be applied in many aspects of life. The study on fluid flow which is now widely studied is on magnetohydrodynamic (MHD). Magnetohydrodynamic is a conductive and electrical in a magnetic field. This paper considers the effect of unsteady magnetic fields on the flow of magneto-hydrodynamic fluid on the boundary layer that flows past a sphere in micropolar fluid influenced by magnetic field. Our approach is as follows. First, we construct a mathematical model and then the system of equations obtained will be solved numerically using the Keller-Box scheme. Then the system is simulated to assess its effect on the fluid flow velocity profile and the profile of microrotation particles. The result of this research indicates, that when the magnetic parameters increase, then velocity profile increases. If material parameters increase, then velocity profile decreases and magnetic parameters increase for n = 0. For n = 0.5, if magnetic parameters increase, then microrotation profile decreases.

  7. The Formation of a Sunspot Penumbra Sector in Active Region NOAA 12574

    NASA Astrophysics Data System (ADS)

    Li, Qiaoling; Yan, Xiaoli; Wang, Jincheng; Kong, DeFang; Xue, Zhike; Yang, Liheng; Cao, Wenda

    2018-04-01

    We present a particular case of the formation of a penumbra sector around a developing sunspot in the active region NOAA 12574 on 2016 August 11 by using the high-resolution data observed by the New Solar Telescope at the Big Bear Solar Observatory and the data acquired by the Helioseismic and Magnetic Imager and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory satellite. Before the new penumbra sector formed, the developing sunspot already had two umbrae with some penumbral filaments. The penumbra sector gradually formed at the junction of two umbrae. We found that the formation of the penumbra sector can be divided into two stages. First, during the initial stage of penumbral formation, the region where the penumbra sector formed always appeared blueshifted in a Dopplergram. The area, mean transverse magnetic field strength, and total magnetic flux of the umbra and penumbra sector all increased with time. The initial penumbral formation was associated with magnetic emergence. Second, when the penumbra sector appeared, the magnetic flux and area of the penumbra sector increased after the umbra’s magnetic flux and area decreased. These results indicate that the umbra provided magnetic flux for penumbral development after the penumbra sector appeared. We also found that the newly formed penumbra sector was associated with sunspot rotation. Based on these findings, we suggest that the penumbra sector was the result of the emerging flux that was trapped in the photosphere at the initial stage of penumbral formation, and when the rudimentary penumbra formed, the penumbra sector developed at the cost of the umbra.

  8. Interaction of magnetized electrons with a boundary sheath: investigation of a specular reflection model

    NASA Astrophysics Data System (ADS)

    Krüger, Dennis; Brinkmann, Ralf Peter

    2017-11-01

    This publication reports analytical and numerical results concerning the interaction of gyrating electrons with a plasma boundary sheath, with focus on partially magnetized technological plasmas. It is assumed that the electron Debye length {λ }{{D}} is much smaller than the electron gyroradius {r}{{L}}, and {r}{{L}} in turn much smaller than the mean free path λ and the gradient length L of the fields. Focusing on the scale of the gyroradius, the sheath is assumed as infinitesimally thin ({λ }{{D}}\\to 0), collisions are neglected (λ \\to ∞ ), the magnetic field is taken as homogeneous, and electric fields (=potential gradients) in the bulk are neglected (L\\to ∞ ). The interaction of an electron with the electric field of the plasma boundary sheath is represented by a specular reflection {v}\\to {v}-2{v}\\cdot {{e}}z {{e}}z of the velocity {v} at the plane z = 0 of a naturally oriented Cartesian coordinate system (x,y,z). The electron trajectory is then given as sequences of helical sections, with the kinetic energy ɛ and the canonical momenta p x and p y conserved, but not the position of the axis (base point {{R}}0), the slope (pitch angle χ), and the phase (gyrophase φ). A ‘virtual interaction’ which directly maps the incoming electrons to the outgoing ones is introduced and studied in dependence of the angle γ between the field and the sheath normal {{e}}z. The corresponding scattering operator is constructed, mathematically characterized, and given as an infinite matrix. An equivalent boundary condition for a transformed kinetic model is derived.

  9. The turbulent plasmasphere boundary layer and the outer radiation belt boundary

    NASA Astrophysics Data System (ADS)

    Mishin, Evgeny; Sotnikov, Vladimir

    2017-12-01

    We report on observations of enhanced plasma turbulence and hot particle distributions in the plasmasphere boundary layer formed by reconnection-injected hot plasma jets entering the plasmasphere. The data confirm that the electron pressure peak is formed just outward of the plasmapause in the premidnight sector. Free energy for plasma wave excitation comes from diamagnetic ion currents near the inner edge of the boundary layer due to the ion pressure gradient, electron diamagnetic currents in the entry layer near the electron plasma sheet boundary, and anisotropic (sometimes ring-like) ion distributions revealed inside, and further inward of, the inner boundary. We also show that nonlinear parametric coupling between lower oblique resonance and fast magnetosonic waves significantly contributes to the VLF whistler wave spectrum in the plasmasphere boundary layer. These emissions represent a distinctive subset of substorm/storm-related VLF activity in the region devoid of substorm injected tens keV electrons and could be responsible for the alteration of the outer radiation belt boundary during (sub)storms.

  10. Sources of magnetic fields in recurrent interplanetary streams

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Behannon, K. W.; Hansen, S. F.; Pneuman, G. W.; Feldman, W. C.

    1977-01-01

    The sources of magnetic fields in recurrent streams were examined. Most fields and plasmas at 1 AU were related to coronal holes, and the magnetic field lines were open in those holes. Some of the magnetic fields and plasmas were related to open field line regions on the sun which were not associated with known coronal holes, indicating that open field lines are more basic than coronal holes as sources of the solar wind. Magnetic field intensities in five equatorial coronal holes ranged from 2G to 18G. Average measured photospheric magnetic fields along the footprints of the corresponding unipolar fields on circular equatorial arcs at 2.5 solar radii had a similar range and average, but in two cases the intensities were approximately three times higher than the projected intensities. The coronal footprints of the sector boundaries on the source surface at 2.5 solar radii, meandered between -45 deg and +45 deg latitude, and their inclination ranged from near zero to near ninety degrees.

  11. Thermal Simulations, Open Boundary Conditions and Switches

    NASA Astrophysics Data System (ADS)

    Burnier, Yannis; Florio, Adrien; Kaczmarek, Olaf; Mazur, Lukas

    2018-03-01

    SU(N) gauge theories on compact spaces have a non-trivial vacuum structure characterized by a countable set of topological sectors and their topological charge. In lattice simulations, every topological sector needs to be explored a number of times which reflects its weight in the path integral. Current lattice simulations are impeded by the so-called freezing of the topological charge problem. As the continuum is approached, energy barriers between topological sectors become well defined and the simulations get trapped in a given sector. A possible way out was introduced by Lüscher and Schaefer using open boundary condition in the time extent. However, this solution cannot be used for thermal simulations, where the time direction is required to be periodic. In this proceedings, we present results obtained using open boundary conditions in space, at non-zero temperature. With these conditions, the topological charge is not quantized and the topological barriers are lifted. A downside of this method are the strong finite-size effects introduced by the boundary conditions. We also present some exploratory results which show how these conditions could be used on an algorithmic level to reshuffle the system and generate periodic configurations with non-zero topological charge.

  12. Geochemistry and magnetic sediment distribution at the western boundary upwelling system of southwest Atlantic

    NASA Astrophysics Data System (ADS)

    Cruz, Anna P. S.; Barbosa, Catia F.; Ayres-Neto, Arthur; Munayco, Pablo; Scorzelli, Rosa B.; Amorim, Nívea Santos; Albuquerque, Ana L. S.; Seoane, José C. S.

    2018-02-01

    In order to investigate the chemical and magnetic characteristics of sediments of the western boundary upwelling system of Southwest Atlantic we analyzed magnetic susceptibility, grain size distribution, total organic carbon, heavy mineral abundance, Fe associated with Mössbauer spectra, and Fe and Mn of pore water to evaluate the deposition patterns of sediments. Four box-cores were collected along a cross-shelf transect. Brazil Current and coastal plume exert a primary control at the inner and outer shelf cores, which exhibited similar depositional patterns characterized by a high abundance of heavy minerals (mean 0.21% and 0.08%, respectively) and very fine sand, whereas middle shelf cores presented low abundances of heavy minerals (mean 0.03%) and medium silt. The inner shelf was dominated by sub-angular grains, while in middle and outer shelf cores well-rounded grains were found. The increasing Fe3+:Fe2+ ratio from the inner to the outer shelf reflects farther distance to the sediment source. The outer shelf presented well-rounded minerals, indicating abrasive processes as a result of transport by the Brazil Current from the source areas. In the middle shelf, cold-water intrusion of the South Atlantic Central Water contributes to the primary productivity, resulting in higher deposition of fine sediment and organic carbon accumulation. The high input of organic carbon and the decreased grain size are indicative of changes in the hydrodynamics and primary productivity fueled by the western boundary upwelling system, which promotes loss of magnetization due to the induction of diagenesis of iron oxide minerals.

  13. Survey of minor-to-moderate magnetic storm effects on ionosphere: American sector

    NASA Astrophysics Data System (ADS)

    Buresova, Dalia; Lastovicka, Jan; Chum, Jaroslav; Pezzopane, Michael; Staciarini Batista, Inez; Gularte, Erika; Novotna, Dagmar

    2014-05-01

    The paper is focused on ionospheric reaction to occasional minor-to-moderate magnetic storms above selected ionospheric stations located across the Northern and Southern America. Most of the storms analysed occurred under extremely low solar activity conditions of 2007-2009. We analysed variability of the F2 layer critical frequency foF2 and the F2 layer peak height hmF2 obtained for different latitudinal and longitudinal sectors of both hemispheres for the entire period of selected magnetic storms. Observations were compared with the effects of strong magnetic storms and with the IRI2000 outputs when STORM model option is activated. We analysed ionospheric reaction during each storm phase with main emphasis paid on the recovery phase. In general, storm recovery phase is characterized by an abatement of perturbations and a gradual return to the "ground state" of ionosphere. Magnetospheric substorms, typical for the main phase, as a rule cease during the storm recovery phase. However, observations of stormy ionosphere show significant departures from the climatology also within this phase, which are comparable with those usually observed during the storm main phase. Both positive and negative deviations of foF2 and hmF2 have been observed independent on season and location.

  14. Asteroid impact vs. Deccan eruptions: The origin of low magnetic susceptibility beds below the Cretaceous-Paleogene boundary revisited

    NASA Astrophysics Data System (ADS)

    Abrajevitch, Alexandra; Font, Eric; Florindo, Fabio; Roberts, Andrew P.

    2015-11-01

    The respective roles of an asteroid impact and Deccan Traps eruptions in biotic changes at the Cretaceous-Paleogene (K-Pg) boundary are still debated. In many shallow marine sediments from around the world, the K-Pg boundary is marked by a distinct clay layer that is often underlain by a several decimeter-thick low susceptibility zone. A previous study of the Gubbio section, Italy (Lowrie et al., 1990), attributed low magnetization intensity in this interval to post-depositional dissolution of ferrimagnetic minerals. Dissolution was thought to be a consequence of downward infiltration of reducing waters that resulted from rapid accumulation of organic matter produced by mass extinctions after the K-Pg event. We compare the magnetic properties of sediments from the Gubbio section with those of the Bidart section in southern France. The two sections are similar in their carbonate lithology and the presence of a boundary clay and low susceptibility zone. When compared to background Cretaceous sediments, the low susceptibility zone in both sections is marked by an absence of biogenic magnetite, a decrease in total ferrimagnetic mineral content, and a preferential loss of magnetite with respect to hematite - features that are consistent with reductive dissolution. However, unlike the Gubbio section, where the low susceptibility zone starts immediately below the boundary clay, the low susceptibility zone and the clay layer at Bidart are separated by a ∼4-cm carbonate interval that contains abundant biogenic magnetite. Such separation casts doubt on a causal link between the impact and sediment bleaching. More likely, the low susceptibility layer marks a different environmental event that preceded the impact. An episode of increased atmospheric and oceanic acidity associated with Deccan Traps volcanism that occurred well before the K-Pg impact is argued here to account for the distinct magnetic properties of the low susceptibility intervals.

  15. Recurrent active regions related to metric radio continuum emissions and the interplanetary magnetic sector structure

    NASA Technical Reports Server (NTRS)

    Sakurai, K.

    1972-01-01

    Active heliographic longitudes at the sun are investigated by using the observational data for long-lived metric continuum noise sources. It is shown that, for the period from 1963 to 1969, the number of such longitudes was four in general and these longitudes were very stable for this radio activity since 1963. A discussion is given on the relationship between those longitudes and the sector structure of the interplanetary magnetic field.

  16. Sector structure of the interplanetary magnetic field in the second half of the 19th century inferred from ground-based magnetometers

    NASA Astrophysics Data System (ADS)

    Vokhmyanin, M.; Ponyavin, D. I.

    2012-12-01

    Interplanetary magnetic field (IMF) polarities can be inferred in the pre-satellite era using Svalgaard-Mansurov effect, according to which different IMF directions lead to different geomagnetic variations at polar stations. Basing on this effect we propose a method to derive a sector structure of the IMF when only ground based data are available. Details of the method and results have been presented in our recent paper: Vokhmyanin, M. V., and D. I. Ponyavin (2012), Inferring interplanetary magnetic field polarities from geomagnetic variations, J. Geophys. Res., 117, A06102, doi:10.1029/2011JA017060. Using data from eight stations: Sitka, Sodankyla, Godhavn, Lerwick, Thule, Baker Lake, Vostok and Mirny, we reconstructed sector structure back to 1905. The quality of inferring from 1965 to 2005 ranges between 78% and 90% depending on the used set of stations. Our results show both high success rate and good agreement with the well-known Russell-McPherron and Rosenberg-Coleman effects. In the current study we applied the technique to historical data of Helsinki observatory where digital versions of hourly geomagnetic components are available from 1844 to 1897. Helsinki station stopped operates at the beginning of 20th century. Thus, to create a model describing the local Svalgaard-Mansurov effect we analyzed data from Nurmijarvi station located near the same region. The success rate of reconstruction from 1965 to 2005 is around 82%. So we assume that the IMF polarities obtained for the period 1869-1889 have sufficient quality. Inferred sector structure at this time consists of two sectors typically for all declining phases of solar activity cycle. Catalogue of IMF proxies seem to be important in analyzing structure and dynamics of solar magnetic fields in the past.; Left: Bartels diagram of IMF sector structure inferred from Helsinki data. Right: sunspot number indicating solar cycles.

  17. Master 3d bosonization duality with boundaries

    NASA Astrophysics Data System (ADS)

    Aitken, Kyle; Karch, Andreas; Robinson, Brandon

    2018-05-01

    We establish the action of the three-dimensional non-Abelian bosonization dualities in the presence of a boundary, which supports a non-anomalous two-dimensional theory. In particular, we generalize a prescriptive method for assigning duality consistent boundary conditions used originally for Abelian dualities to dual non-Abelian Chern-Simons-matter theories with SU and U gauge groups and fundamental matter sectors. The cases of single species matter sectors and those with both scalars and fermions in the dual theories are considered. Generalization of our methods to SO and USp Chern-Simons theories is also discussed.

  18. The magnetic field at the core-mantle boundary

    NASA Technical Reports Server (NTRS)

    Bloxham, J.; Gubbins, D.

    1985-01-01

    Models of the geomagnetic field are, in general, produced from a least-squares fit of the coefficients in a truncated spherical harmonic expansion to the available data. Downward continuation of such models to the core-mantle boundary (CMB) is an unstable process: the results are found to be critically dependent on the choice of truncation level. Modern techniques allow this fundamental difficulty to be circumvented. The method of stochastic inversion is applied to modeling the geomagnetic field. Prior information is introduced by requiring that the spectrum of spherical harmonic coefficients to fall-off in a particular manner which is consistent with the Ohmic heating in the core having a finite lower bound. This results in models with finite errors in the radial field at the CMB. Curves of zero radial field can then be determined and integrals of the radial field over patches on the CMB bounded by these null-flux curves calculated. With the assumption of negligible magnetic diffusion in the core; frozen-flux hypothesis, these integrals are time-invariant.

  19. From boundaries to boundary work: middle managers creating inter-organizational change.

    PubMed

    Oldenhof, Lieke; Stoopendaal, Annemiek; Putters, Kim

    2016-11-21

    Purpose In healthcare, organizational boundaries are often viewed as barriers to change. The purpose of this paper is to show how middle managers create inter-organizational change by doing boundary work: the dual act of redrawing boundaries and coordinating work in new ways. Design/methodology/approach Theoretically, the paper draws on the concept of boundary work from Science and Technology Studies. Empirically, the paper is based on an ethnographic investigation of middle managers that participate in a Dutch reform program across health, social care, and housing. Findings The findings show how middle managers create a sense of urgency for inter-organizational change by emphasizing "fragmented" service provision due to professional, sectoral, financial, and geographical boundaries. Rather than eradicating these boundaries, middle managers change the status quo gradually by redrawing composite boundaries. They use boundary objects and a boundary-transcending vocabulary emphasizing the need for societal gains that go beyond production targets of individual organizations. As a result, work is coordinated in new ways in neighborhood teams and professional expertise is being reconfigured. Research limitations/implications Since boundary workers create incremental change, it is necessary to follow their work for a longer period to assess whether boundary work contributes to paradigm change. Practical implications Organizations should pay attention to conditions for boundary work, such as legitimacy of boundary workers and the availability of boundary spaces that function as communities of practice. Originality/value By shifting the focus from boundaries to boundary work, this paper gives valuable insights into "how" boundaries are redrawn and embodied in objects and language.

  20. Dynamics of Coronal Hole Boundaries

    SciTech Connect

    Higginson, A. K.; Zurbuchen, T. H.; Antiochos, S. K.

    Remote and in situ observations strongly imply that the slow solar wind consists of plasma from the hot, closed-field corona that is released onto open magnetic field lines. The Separatrix Web theory for the slow wind proposes that photospheric motions at the scale of supergranules are responsible for generating dynamics at coronal-hole boundaries, which result in the closed plasma release. We use three-dimensional magnetohydrodynamic simulations to determine the effect of photospheric flows on the open and closed magnetic flux of a model corona with a dipole magnetic field and an isothermal solar wind. A rotational surface motion is used tomore » approximate photospheric supergranular driving and is applied at the boundary between the coronal hole and helmet streamer. The resulting dynamics consist primarily of prolific and efficient interchange reconnection between open and closed flux. The magnetic flux near the coronal-hole boundary experiences multiple interchange events, with some flux interchanging over 50 times in one day. Additionally, we find that the interchange reconnection occurs all along the coronal-hole boundary and even produces a lasting change in magnetic-field connectivity in regions that were not driven by the applied motions. Our results show that these dynamics should be ubiquitous in the Sun and heliosphere. We discuss the implications of our simulations for understanding the observed properties of the slow solar wind, with particular focus on the global-scale consequences of interchange reconnection.« less

  1. The magnetic toroidal sector: a broad-band electron-positron pair spectrometer

    NASA Astrophysics Data System (ADS)

    Hagmann, Siegbert; Hillenbrand, Pierre-Michel; Litvinov, Yuri; Spillmann, Uwe

    2016-05-01

    At the future relativistic storage-ring HESR at FAIR the study of electron-positron pairs from non-nuclear, atomic processes will be one of the goals of the experimental program with kinematically complete experiments focusing on momentum spectroscopy of coincident emission of electrons and positrons from free-free pairs and corresponding recoil ions. The underlying production mechanisms belong to central topics of QED in strong fields. We present first results on the electron-optical properties of a magnetic toroidal sector configuration enabling coincident detection of free-free electron-positron pairs; this spectrometer is suitable for implementation into a storage ring with a supersonic jet target and covering a wide range of lepton emission into the forward hemisphere. The simulation calculations are performed using the OPERA code.

  2. Simulating functional magnetic materials on supercomputers.

    PubMed

    Gruner, Markus Ernst; Entel, Peter

    2009-07-22

    The recent passing of the petaflop per second landmark by the Roadrunner project at the Los Alamos National Laboratory marks a preliminary peak of an impressive world-wide development in the high-performance scientific computing sector. Also, purely academic state-of-the-art supercomputers such as the IBM Blue Gene/P at Forschungszentrum Jülich allow us nowadays to investigate large systems of the order of 10(3) spin polarized transition metal atoms by means of density functional theory. Three applications will be presented where large-scale ab initio calculations contribute to the understanding of key properties emerging from a close interrelation between structure and magnetism. The first two examples discuss the size dependent evolution of equilibrium structural motifs in elementary iron and binary Fe-Pt and Co-Pt transition metal nanoparticles, which are currently discussed as promising candidates for ultra-high-density magnetic data storage media. However, the preference for multiply twinned morphologies at smaller cluster sizes counteracts the formation of a single-crystalline L1(0) phase, which alone provides the required hard magnetic properties. The third application is concerned with the magnetic shape memory effect in the Ni-Mn-Ga Heusler alloy, which is a technologically relevant candidate for magnetomechanical actuators and sensors. In this material strains of up to 10% can be induced by external magnetic fields due to the field induced shifting of martensitic twin boundaries, requiring an extremely high mobility of the martensitic twin boundaries, but also the selection of the appropriate martensitic structure from the rich phase diagram.

  3. Rethinking the Boundaries

    ERIC Educational Resources Information Center

    Schuller, Tom

    2011-01-01

    The splintering of the public domain makes the development of a coherent lifelong learning system less likely. But while people might want to resist plans to dissolve the boundaries between the public, private and voluntary sectors, debate about the relationship between professionals and volunteers in adult education suggests those boundaries…

  4. Boundary-field-driven control of discontinuous phase transitions on hyperbolic lattices

    NASA Astrophysics Data System (ADS)

    Lee, Yoju; Verstraete, Frank; Gendiar, Andrej

    2016-08-01

    The multistate Potts models on two-dimensional hyperbolic lattices are studied with respect to various boundary effects. The free energy is numerically calculated using the corner transfer matrix renormalization group method. We analyze phase transitions of the Potts models in the thermodynamic limit with respect to contracted boundary layers. A false phase transition is present even if a couple of the boundary layers are contracted. Its significance weakens, as the number of the contracted boundary layers increases, until the correct phase transition (deep inside the bulk) prevails over the false one. For this purpose, we derive a thermodynamic quantity, the so-called bulk excess free energy, which depends on the contracted boundary layers and memorizes additional boundary effects. In particular, the magnetic field is imposed on the outermost boundary layer. While the boundary magnetic field does not affect the second-order phase transition in the bulk if suppressing all the boundary effects on the hyperbolic lattices, the first-order (discontinuous) phase transition is significantly sensitive to the boundary magnetic field. Contrary to the phase transition on the Euclidean lattices, the discontinuous phase transition on the hyperbolic lattices can be continuously controlled (within a certain temperature coexistence region) by varying the boundary magnetic field.

  5. Statistical analysis of the location of the Martian magnetic pileup boundary and bow shock and the influence of crustal magnetic fields

    NASA Astrophysics Data System (ADS)

    Edberg, N. J. T.; Lester, M.; Cowley, S. W. H.; Eriksson, A. I.

    2008-08-01

    We use the data set from the magnetometer and electron reflectometer instruments on board the Mars Global Surveyor spacecraft to show that the crustal magnetic fields of Mars affect the location of the magnetic pileup boundary (MPB) and bow shock (BS) globally. We search for crossings of the MPB and BS in the data that were observed over the first 16 months of the mission. To identify the influence of the crustal magnetic fields, all crossings are extrapolated to the terminator plane in order to remove the solar zenith angle (SZA) dependence, and to make it possible to compare crossings independently of location. The MPB crossings that were observed over regions on Mars, which contain strong crustal magnetic fields, are on average located further out than crossings observed over regions with weak crustal fields. This is shown in three separate longitude intervals. We also find that the dayside BS crossings observed over the southern hemisphere of Mars are on average located further out than the BS crossings observed over the northern hemisphere, possibly because of the influence of the crustal fields. We also study the magnetic field strength and its variation at the inside of the MPB and their dependence on the SZA and altitude. We find that the magnitude of the magnetic field in the MPB is closely linked to the altitude of the MPB, with the magnitude increasing as the MPB is observed closer to the planet.

  6. Boundary-value problem for a counterrotating electrical discharge in an axial magnetic field. [plasma centrifuge for isotope separation

    NASA Technical Reports Server (NTRS)

    Hong, S. H.; Wilhelm, H. E.

    1978-01-01

    An electrical discharge between two ring electrodes embedded in the mantle of a cylindrical chamber is considered, in which the plasma in the anode and cathode regions rotates in opposite directions under the influence of an external axial magnetic field. The associated boundary-value problem for the coupled partial differential equations describing the azimuthal velocity and radial current-density fields is solved in closed form. The velocity, current density, induced magnetic induction, and electric fields are presented for typical Hartmann numbers, magnetic Reynolds numbers, and geometry parameters. The discharge is shown to produce anodic and cathodic plasma sections rotating at speeds of the order 1,000,000 cm/sec for conventional magnetic field intensities. Possible application of the magnetoactive discharge as a plasma centrifuge for isotope separation is discussed.

  7. Low-energy planar magnetic defects in BaFe 2 As 2 : Nanotwins, twins, antiphase, and domain boundaries

    SciTech Connect

    Khan, S. N.; Alam, Aftab; Johnson, Duane D.

    2013-11-27

    In BaFe 2As 2, structural and magnetic planar defects begin to proliferate below the structural phase transition, affecting descriptions of magnetism and superconductivity. We study, using density-functional theory, the stability and magnetic properties of competing antiphase and domain boundaries, twins and isolated nanotwins (twin nuclei), and spin excitations proposed and/or observed. These nanoscale defects have a very low surface energy (22–210 m Jm -2), with twins favorable to the mesoscale. Defects exhibit smaller moments confined near their boundaries—making a uniform-moment picture inappropriate for long-range magnetic order in real samples. Nanotwins explain features in measured pair distribution functions so should bemore » considered when analyzing scattering data. All these defects can be weakly mobile and/or can have fluctuations that lower assessed “ordered” moments from longer spatial and/or time averaging and should be considered directly.« less

  8. Twin-enhanced magnetic torque

    NASA Astrophysics Data System (ADS)

    Hobza, Anthony; García-Cervera, Carlos J.; Müllner, Peter

    2018-07-01

    Magnetic shape memory alloys experience magnetic-field-induced torque due to magnetocrystalline anisotropy and shape anisotropy. In a homogeneous magnetic field, torque results in bending of long samples. This study investigates the torque on a single crystal of Ni-Mn-Ga magnetic shape memory alloy constrained with respect to bending in an external magnetic field. The dependence of the torque on external magnetic field magnitude, strain, and twin boundary structure was studied experimentally and with computer simulations. With increasing magnetic field, the torque increased until it reached a maximum near 700 mT. Above 200 mT, the torque was not symmetric about the equilibrium orientation for a sample with one twin boundary. The torque on two specimen with equal strain but different twin boundary structures varied systematically with the spatial arrangement of crystallographic twins. Numerical simulations show that twin boundaries suppress the formation of 180° domains if the direction of easy magnetization between two twin boundaries is parallel to a free surface and the magnetic field is perpendicular to that surface. For a particular twin microstructure, the torque decreases with increasing strain by a factor of six due to the mutual compensation of magnetocrystalline and shape anisotropy. When free rotation is suppressed such as in transducers of magneto-mechanical actuators, magnetic-field-induced torque creates strong bending forces, which may cause friction and failure under cyclic loading.

  9. Parallel Tracks as Quasi-steady States for the Magnetic Boundary Layers in Neutron-star Low-mass X-Ray Binaries

    SciTech Connect

    Erkut, M. Hakan; Çatmabacak, Onur, E-mail: mherkut@gmail.com

    The neutron stars in low-mass X-ray binaries (LMXBs) are usually thought to be weakly magnetized objects accreting matter from their low-mass companions in the form of a disk. Albeit weak compared to those in young neutron-star systems, the neutron-star magnetospheres in LMXBs can play an important role in determining the correlations between spectral and temporal properties. Parallel tracks appearing in the kilohertz (kHz) quasi-periodic oscillation (QPO) frequency versus X-ray flux plane can be used as a tool to study the magnetosphere–disk interaction in neutron-star LMXBs. For dynamically important weak fields, the formation of a non-Keplerian magnetic boundary layer at themore » innermost disk truncated near the surface of the neutron star is highly likely. Such a boundary region may harbor oscillatory modes of frequencies in the kHz range. We generate parallel tracks using the boundary region model of kHz QPOs. We also present the direct application of our model to the reproduction of the observed parallel tracks of individual sources such as 4U 1608–52, 4U 1636–53, and Aql X-1. We reveal how the radial width of the boundary layer must vary in the long-term flux evolution of each source to regenerate the parallel tracks. The run of the radial width looks similar for different sources and can be fitted by a generic model function describing the average steady behavior of the boundary region over the long term. The parallel tracks then correspond to the possible quasi-steady states the source can occupy around the average trend.« less

  10. Parallel Tracks as Quasi-steady States for the Magnetic Boundary Layers in Neutron-star Low-mass X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Erkut, M. Hakan; Çatmabacak, Onur

    2017-11-01

    The neutron stars in low-mass X-ray binaries (LMXBs) are usually thought to be weakly magnetized objects accreting matter from their low-mass companions in the form of a disk. Albeit weak compared to those in young neutron-star systems, the neutron-star magnetospheres in LMXBs can play an important role in determining the correlations between spectral and temporal properties. Parallel tracks appearing in the kilohertz (kHz) quasi-periodic oscillation (QPO) frequency versus X-ray flux plane can be used as a tool to study the magnetosphere-disk interaction in neutron-star LMXBs. For dynamically important weak fields, the formation of a non-Keplerian magnetic boundary layer at the innermost disk truncated near the surface of the neutron star is highly likely. Such a boundary region may harbor oscillatory modes of frequencies in the kHz range. We generate parallel tracks using the boundary region model of kHz QPOs. We also present the direct application of our model to the reproduction of the observed parallel tracks of individual sources such as 4U 1608-52, 4U 1636-53, and Aql X-1. We reveal how the radial width of the boundary layer must vary in the long-term flux evolution of each source to regenerate the parallel tracks. The run of the radial width looks similar for different sources and can be fitted by a generic model function describing the average steady behavior of the boundary region over the long term. The parallel tracks then correspond to the possible quasi-steady states the source can occupy around the average trend.

  11. Solutions of the Helmholtz equation with boundary conditions for force-free magnetic fields

    NASA Technical Reports Server (NTRS)

    Rasband, S. N.; Turner, L.

    1981-01-01

    It is shown that the solution, with one ignorable coordinate, for the Taylor minimum energy state (resulting in a force-free magnetic field) in either a straight cylindrical or a toroidal geometry with arbitrary cross section can be reduced to the solution of either an inhomogeneous Helmholtz equation or a Grad-Shafranov equation with simple boundary conditions. Standard Green's function theory is, therefore, applicable. Detailed solutions are presented for the Taylor state in toroidal and cylindrical domains having a rectangular cross section. The focus is on solutions corresponding to the continuous eigenvalue spectra. Singular behavior at 90 deg corners is explored in detail.

  12. Quantifying the relationship between the plasmapause and the inner boundary of small-scale field-aligned currents, as deduced from Swarm observations

    NASA Astrophysics Data System (ADS)

    Heilig, Balázs; Lühr, Hermann

    2018-04-01

    This paper presents a statistical study of the equatorward boundary of small-scale field-aligned currents (SSFACs) and investigates the relation between this boundary and the plasmapause (PP). The PP data used for validation were derived from in situ electron density observations of NASA's Van Allen Probes. We confirmed the findings of a previous study by the same authors obtained from the observations of the CHAMP satellite SSFAC and the NASA IMAGE satellite PP detections, namely that the two boundaries respond similarly to changes in geomagnetic activity, and they are closely located in the near midnight MLT sector, suggesting a dynamic linkage. Dayside PP correlates with the delayed time history of the SSFAC boundary. We interpreted this behaviour as a direct consequence of co-rotation: the new PP, formed on the night side, propagates to the dayside by rotating with Earth. This finding paves the way toward an efficient PP monitoring tool based on an SSFAC index derived from vector magnetic field observations at low-Earth orbit.

  13. Dynamics of Coronal Hole Boundaries

    NASA Technical Reports Server (NTRS)

    Higginson, A. K.; Antiochos, S. K.; DeVore, C. R.; Wyper, Peter F.; Zurbuchen, T. H.

    2017-01-01

    Remote and in situ observations strongly imply that the slow solar wind consists of plasma from the hot, closed-field corona that is released onto open magnetic field lines. The Separatrix Web theory for the slow wind proposesthat photospheric motions at the scale of supergranules are responsible for generating dynamics at coronal-holeboundaries, which result in the closed plasma release. We use three-dimensional magnetohydrodynamicsimulations to determine the effect of photospheric flows on the open and closed magnetic flux of a model coronawith a dipole magnetic field and an isothermal solar wind. A rotational surface motion is used to approximatephotospheric supergranular driving and is applied at the boundary between the coronal hole and helmet streamer.The resulting dynamics consist primarily of prolific and efficient interchange reconnection between open andclosed flux. The magnetic flux near the coronal-hole boundary experiences multiple interchange events, with someflux interchanging over 50 times in one day. Additionally, we find that the interchange reconnection occurs allalong the coronal-hole boundary and even produces a lasting change in magnetic-field connectivity in regions thatwere not driven by the applied motions. Our results show that these dynamics should be ubiquitous in the Sun andheliosphere. We discuss the implications of our simulations for understanding the observed properties of the slowsolar wind, with particular focus on the global-scale consequences of interchange reconnection.

  14. Three-dimensional Features of the Outer Heliosphere Due to Coupling between the Interstellar and Heliospheric Magnetic Field. V. The Bow Wave, Heliospheric Boundary Layer, Instabilities, and Magnetic Reconnection

    SciTech Connect

    Pogorelov, N. V.; Heerikhuisen, J.; Roytershteyn, V.

    The heliosphere is formed due to interaction between the solar wind (SW) and local interstellar medium (LISM). The shape and position of the heliospheric boundary, the heliopause, in space depend on the parameters of interacting plasma flows. The interplay between the asymmetrizing effect of the interstellar magnetic field and charge exchange between ions and neutral atoms plays an important role in the SW–LISM interaction. By performing three-dimensional, MHD plasma/kinetic neutral atom simulations, we determine the width of the outer heliosheath—the LISM plasma region affected by the presence of the heliosphere—and analyze quantitatively the distributions in front of the heliopause. Itmore » is shown that charge exchange modifies the LISM plasma to such extent that the contribution of a shock transition to the total variation of plasma parameters becomes small even if the LISM velocity exceeds the fast magnetosonic speed in the unperturbed medium. By performing adaptive mesh refinement simulations, we show that a distinct boundary layer of decreased plasma density and enhanced magnetic field should be observed on the interstellar side of the heliopause. We show that this behavior is in agreement with the plasma oscillations of increasing frequency observed by the plasma wave instrument onboard Voyager 1. We also demonstrate that Voyager observations in the inner heliosheath between the heliospheric termination shock and the heliopause are consistent with dissipation of the heliospheric magnetic field. The choice of LISM parameters in this analysis is based on the simulations that fit observations of energetic neutral atoms performed by Interstellar Boundary Explorer .« less

  15. Role of magnetic fluctuations in mode selection of magnetically driven instabilities

    NASA Astrophysics Data System (ADS)

    Dan, Jia-Kun; Ren, Xiao-Dong; Huang, Xian-Bin; Ouyang, Kai; Chen, Guang-Hua

    2014-12-01

    The influences of magnetic fluctuations on quasiperiodic structure formation and fundamental wavelength selection of the instability have been studied using two 25-μm-diameter tungsten wires on a 100 ns rise time, 220 kA pulsed power facility. Two different load configurations were adopted to make end surfaces of electrodes approximately satisfy reflecting and absorbing boundary conditions, respectively. The experimental results that the fundamental wavelength in the case of absorbing boundary condition is about one half of that in the case of reflecting boundary condition have demonstrated that magnetic fluctuations appear to play a key role in mode selection of magnetically driven instabilities. The dominant wavelength should be proportional to magnetic field and inversely proportional to square root of mass density, provided that the magnetosonic wave propagating perpendicular to magnetic fields provides a leading candidate for magnetic fluctuations. Therefore, magnetic fluctuation is one of the three key perturbations, along with surface contaminants and surface roughness, that seeds magnetically driven instabilities.

  16. Contributions to the Fourth Solar Wind Conference. [interplanetary magnetic fields and medium

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Behannon, K. W.; Burlaga, L. F.; Lepping, R.; Ness, N.; Ogilvie, K.; Pizzo, J.

    1979-01-01

    Recent results in interplanetary physics are examined. These include observations of shock waves and post-shock magnetic fields made by Voyager 1, 2; observations of the electron temperature as a function of distance between 1.36 AU and 2.25 AU; and observations of the structure of sector boundaries observed by Helios 1. A theory of electron energy transport in the collisionless solar wind is presented, and compared with observations. Alfven waves and Alvenic fluctuations in the solar wind are also discussed.

  17. Magnetization reversal mechanism and coercivity enhancement in three-dimensional granular Nd-Fe-B magnets studied by micromagnetic simulations

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Hyeok; Choe, Jinhyeok; Hwang, Shinwon; Kim, Sang-Koog

    2017-08-01

    We studied the mechanism of magnetization reversals and coercivity enhancements in three-dimensional (3D) granular Nd-Fe-B permanent magnets using finite-element micromagnetic simulations. The magnetization reversals in the hard magnets consisting of hard-phase grains separated by relatively soft-phase grain boundaries were analyzed with reference to the simulation results for the magnetic field-dependent distributions of the local magnetizations. The saturation magnetization of the grain-boundary phase plays a crucial role in the transition between nucleation- and domain-wall-propagation-controlled reversal processes. The smaller the saturation magnetization of the grain-boundary phase is, the more preferable is the nucleation-controlled process, which results in a larger coercivity. The exchange stiffness of the grain-boundary phase determines the preferred paths of domain-wall propagations, whether inward into grains or along the grain boundaries for relatively small and large exchange stiffness, respectively. However, the exchange stiffness of the grain-boundary phase alone does not significantly contribute to coercivity enhancement in cases where the size of hard-phase grains is much greater than the exchange length. This work paves the way for the design of high-performance hard magnets of large coercivity and maximum-energy-product values.

  18. Parallel Electric Field on Auroral Magnetic Field Lines.

    NASA Astrophysics Data System (ADS)

    Yeh, Huey-Ching Betty

    1982-03-01

    The interaction of Birkeland (magnetic-field-aligned) current carriers and the Earth's magnetic field results in electrostatic potential drops along magnetic field lines. The statistical distributions of the field-aligned potential difference (phi)(,(PARLL)) were determined from the energy spectra of electron inverted "V" events observed at ionospheric altitude for different conditions of geomagnetic activity as indicated by the AE index. Data of 1270 electron inverted "V"'s were obtained from Low-Energy Electron measurements of the Atmosphere Explorer-C and -D Satellite (despun mode) in the interval January 1974-April 1976. In general, (phi)(,(PARLL)) is largest in the dusk to pre-midnight sector, smaller in the post-midnight to dawn sector, and smallest in the near noon sector during quiet and disturbed geomagnetic conditions; there is a steady dusk-dawn-noon asymmetry of the global (phi)(,(PARLL)) distribution. As the geomagnetic activity level increases, the (phi)(,(PARLL)) pattern expands to lower invariant latitudes, and the magnitude of (phi)(,(PARLL)) in the 13-24 magnetic local time sector increases significantly. The spatial structure and intensity variation of the global (phi)(,(PARLL)) distribution are statistically more variable, and the magnitudes of (phi)(,(PARLL)) have smaller correlation with the AE-index, in the post-midnight to dawn sector. A strong correlation is found to exist between upward Birkeland current systems and global parallel potential drops, and between auroral electron precipitation patterns and parallel potential drops, regarding their mophology, their intensity and their dependence of geomagnetic activity. An analysis of the fine-scale simultaneous current-voltage relationship for upward Birkeland currents in Region 1 shows that typical field-aligned potential drops are consistent with model predictions based on linear acceleration of the charge carriers through an electrostatic potential drop along convergent magnetic field

  19. The effects of a uniform axial magnetic field on the global stability of the rotating-disk boundary-layer

    NASA Astrophysics Data System (ADS)

    Davies, Christopher; Thomas, Christian

    2006-11-01

    Following on from the earlier discovery by Lingwood (1995) that the rotating-disk boundary-layer is absolutely unstable, Jasmine & Gajjar (2005) have shown that the application of a uniform axial magnetic field can raise the critical Reynolds number for the onset of absolute instability. As with Lingwood's analysis, a parallel-flow' type of approximation is needed in order to derive this locally-based stability result. The approximation amounts to a freezing out' of the underlying radial variation of the mean flow. Numerical simulations have been conducted to investigate the behaviour of linearized disturbances in the genuine rotating disk boundary layer, where the radial dependence of the mean flow is fully accounted for. This extends the work of Davies & Carpenter (2003), who studied the more usual rotating-disk problem, in the absence of any magnetic field. The simulation results suggest that globally unstable behaviour can be promoted when a uniform axial magnetic field is applied. Impulsively excited disturbances were found to display an increasingly rapid growth at the radial position of the impulse, albeit without any selection of a dominant frequency, as would be more usual for an unstable global mode. This is very similar to the behaviour to that was observed in a recent investigation by Davies & Thomas (2005) of the effects of mass transfer, where suction was also found to promote global instability.

  20. Auroral boundary movement rates during substorm onsets and their correspondence to solar wind and the AL index

    NASA Astrophysics Data System (ADS)

    Andriyas, Tushar

    2016-08-01

    A statistical analysis of the equatorward and poleward auroral boundary movement during substorm onsets, the related solar wind activity, GOES 8 and 10 magnetic field, and the westward auroral electrojet (AL) index is undertaken, during the years 2000-2002. Auroral boundary data were obtained from the British Antarctic Survey (BAS). These boundaries were derived using auroral images from the IMAGE satellite. The timing of the onsets was derived from the Frey et al. (2004) database. Data were also classified based on the peak AL around the onset and the onset latitude, in order to analyze the differences, if any, in the rates of movement. It was found that the absolute ratio of the rate of movement of the mean poleward and equatorward boundaries was slower than the rate of mean movement around the midnight sector. The stronger the onset (in terms of the peak AL around the onset) was, the faster the rate of movement for both the boundaries. This implies that the stronger the AL signature around the onset, the weaker the magnetic field was prior to the onset and the faster it increased after the onset at GOES 8 and 10 locations. The stronger the AL signature, the thicker the latitudinal width of the aurora was, prior to the onset and higher was the increase in the width after the onset, due to large poleward and average equatorward expansion. Magnetotail field line stretching and relaxation rates as measured by GOES were also found to lie in the same order of magnitude. It is therefore concluded that the rates of latitudinal descent prior to a substorm onset and ascent after the onset, of the mean auroral boundaries, corresponds to the rate at which the tail field lines stretch and relax before and after the onset, respectively.

  1. A plasmapause-like density boundary at high latitudes in Saturn's magnetosphere

    NASA Astrophysics Data System (ADS)

    Gurnett, D. A.; Persoon, A. M.; Kopf, A. J.; Kurth, W. S.; Morooka, M. W.; Wahlund, J.-E.; Khurana, K. K.; Dougherty, M. K.; Mitchell, D. G.; Krimigis, S. M.; Krupp, N.

    2010-08-01

    Here we report the discovery of a well-defined plasma density boundary at high latitudes in Saturn's magnetosphere. The boundary separates a region of relatively high density at L less than about 8 to 15 from a region with densities nearly three orders of magnitude lower at higher L values. Magnetic field measurements show that strong field-aligned currents, probably associated with the aurora, are located just inside the boundary. Analyses of the anisotropy of energetic electrons show that the magnetic field lines are usually closed inside the boundary and open outside the boundary, although exceptions sometimes occur. The location of the boundary is also modulated at the ˜10.6 to 10.8 hr rotational period of the planet. Many of these characteristics are similar to those predicted by Brice and Ioannidis for the plasmapause at a strongly magnetized, rapidly rotating planet such as Saturn.

  2. Magnetic storm inflation in the evening sector.

    NASA Technical Reports Server (NTRS)

    Cahill, L. J., Jr.

    1973-01-01

    Analysis of the different behavior of a double magnetic disturbance in November 1971, as observed by Explorer 45, and in December 1971, as shown by ground level magnetic observations. The time sequence of magnetic storm inflation in the evening quadrant of the magnetosphere, as determined by both series of observations, is used as the criterion of the analysis. Particular attention is given to the various phases of proton penetration into the evening quadrant of the magnetosphere during the magnetic disturbance.

  3. Notes on integrable boundary interactions of open SU(4) alternating spin chains

    NASA Astrophysics Data System (ADS)

    Wu, JunBao

    2018-07-01

    Ref. [J. High Energy Phys. 1708, 001 (2017)] showed that the planar flavored Ahanory-Bergman-Jafferis-Maldacena (ABJM) theory is integrable in the scalar sector at two-loop order using coordinate Bethe ansatz. A salient feature of this case is that the boundary reflection matrices are anti-diagonal with respect to the chosen basis. In this paper, we relax the coefficients of the boundary terms to be general constants to search for integrable systems among this class. We found that the only integrable boundary interaction at each end of the spin chain aside from the one in ref. [J. High Energy Phys. 1708, 001 (2017)] is the one with vanishing boundary interactions leading to diagonal reflection matrices. We also construct non-supersymmetric planar flavored ABJM theory which leads to trivial boundary interactions at both ends of the open chain from the two-loop anomalous dimension matrix in the scalar sector.

  4. By-controlled convection and field-aligned currents near midnight auroral oval for northward interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Taguchi, S.; Sugiura, M.; Iyemori, T.; Winningham, J. D.; Slavin, J. A.

    1994-01-01

    Using the Dynamics Explorer (DE) 2 magnetic and electric field and plasma data, B(sub y)- controlled convection and field-aligned currents in the midnight sector for northward interplanetary magnetic field (IMF) are examined. The results of an analysis of the electric field data show that when IMF is stable and when its magnitude is large, a coherent B(sub y)-controlled convection exists near the midnight auroral oval in the ionosphere having adequate conductivities. When B(sub y) is negative, the convection consists of a westward (eastward) plasma flow at the lower latitudes and an eastward (westward) plasma flow at the higher latitudes in the midnight sector in the northern (southern) ionosphere. When B(sub y) is positive, the flow directions are reversed. The distribution of the field-aligned currents associated with the B(sub y)-controlled convection, in most cases, shows a three-sheet structure. In accordance with the convection the directions of the three sheets are dependent on the sign of B(sub y). The location of disappearance of the precipitating intense electrons having energies of a few keV is close to the convection reversal surface. However, the more detailed relationship between the electron precipitation boundary and the convection reversal surface depends on the case. In some cases the precipitating electrons extend beyond the convection reversal surface, and in others the poleward boundary terminates at a latitude lower than the reversal surface. Previous studies suggest that the poleward boundary of the electrons having energies of a few keV is not necessarily coincident with an open/closed bounary. Thus the open/closed boundary may be at a latitude higher than the poleward boundary of the electron precipitation, or it may be at a latitude lower than the poleward boundary of the electron precipitation. We discuss relationships between the open/closed boundary and the convection reversal surface. When as a possible choice we adopt a view that the

  5. Optics of a Double Focussing Magnetic Sector by Fringe Effect; OPTIQUE D'UN SECTEUR MAGNETIQUE A DOUBLE FOCALISATION PAR EFFET DE FRANCES

    SciTech Connect

    Krafft, J.

    1960-01-01

    A general study is made of the optical elements of a double-fccusing magnetic sector by the fringe effect, with a view to its application to the monochromation of the proton, deuteron, or triton beam of the 1.4 Mev accelerator. (auth)

  6. Numerical study of compressible magnetoconvection with an open transitional boundary

    SciTech Connect

    Hanami, H.; Tajima, T.

    1990-08-01

    We study by computer simulation nonlinear evolution of magnetoconvection in a system with a dynamical open boundary between the convection region and corona of the sun. We study a model in which the fluid is subject to the vertical gravitation, magnetohydrodynamics (MHD), and high stratification, through an MHD code with the MacCormack-Donner cell hybrid scheme in order to well represent convective phenomena. Initially the vertical fluid flux penetrates from the convectively unstable zone at the bottom into the upper diffuse atmosphere. As the instability develops, the magnetic fields are twisted by the convection motion and the folding magnetic fields ismore » observed. When the magnetic pressure is comparable to the thermal pressure in the upper layer of convective zone, strong flux expulsion from the convective cell interior toward the cell boundary appears. Under appropriate conditions our simulation exhibits no shock formation incurred by the fluid convected to the photosphere, in contrast to earlier works with box boundaries. The magnetic field patterns observed are those of concentrated magnetic flux tubes, accumulation of dynamo flux near the bottom boundary, pinched flux near the downdraft region, and the surface movement of magnetic flux toward the downdraft region. Many of these computationally observed features are reminiscent of solar observations of the fluid and magnetic structures of their motions.« less

  7. The location and nature of the Telemzan High Ghadames basin boundary in southern Tunisia based on gravity and magnetic anomalies

    NASA Astrophysics Data System (ADS)

    Gabtni, H.; Jallouli, C.; Mickus, K. L.; Zouari, H.; Turki, M. M.

    2006-03-01

    Gravity and magnetic data were analyzed to add constraints on the location and nature of the Telemzan-Ghadames boundary (TGB) and structure of the Ghadames basin in southern Tunisia. TGB is the boundary between the thick sedimentary cover of the intracratonic Ghadames basin to the south and the thin sedimentary cover of the Saharan platform to the north. The upward continuation of the Bouguer gravity anomalies showed that the TGB is a regional geophysical feature that may have controlled the amount of sediment being deposited both north and south of the boundary and the tectonic environment in the region since Paleozoic time. To emphasize the shorter wavelength gravity and magnetic anomalies, a series of gray scale images of the directional horizontal gradients were constructed that determined a series of previously unknown east-west-trending gravity and magnetic anomalies south of 31.6°N that correspond to lineaments seen on a Landsat 7 image and the location of the TGB. Also, an edge-enhancement analysis illustrated the same linear gravity anomalies and showed the subbasins and uplifts within the Ghadames basin had source depths of between 0.5 and 3.4 km. A north-south trending gravity model showed that the TGB is a relatively gradual feature (possibly basement stepped down by relatively low-displacement faulting) controlling the subsidence of the main Ghadames basin and confirms the edge-enhancement analysis that subbasin S3 and uplift U1 are the main structural features within the Ghadames basin. The knowledge of basement architecture of the Ghadames basin is important for future petroleum exploration within this intracratonic basin.

  8. Performance evaluation of a miniature magnetic sector mass spectrometer onboard a satellite in space.

    PubMed

    Guo, Meiru; Li, Detian; Cheng, Yongjun; Wang, Yongjun; Sun, Wenjun; Pei, Xiaoqiang; Dong, Meng; Sheng, Xuemin; Zhao, Lan; Li, Yanwu

    2018-04-01

    With the rapid development of space technology in China, it is urgent to use mass spectrometer to detect the space environment. In this work, a space miniature magnetic sector mass spectrometer is evaluated, which consists of three subsystems: (1) physical unit, (2) electric control unit, (3) and high voltage power. It has 90° magnetic sector-field analyzer with double trajectory, in which a trajectory measurement range is from 1 to 12 amu, the other range is from 6 to 90 amu.The mass spectrometer has two work models, one is used to measure space neutral gas when the filament of mass spectrometer ion source turned on, the other is used to measure space charged ions when the filament turned off. The absolute resolution of this device is less than 1 amu, the minimum detectable ion current is about 10 -13  A, and the sensitivity is 10 -6  A/Pa (N 2 ). Its overall size is 170 mm × 165 mm × 170 mm, its weight is 4.5 kg, and its power consumption is 18 W. A series of environmental adaptability tests, including high and low temperature cycle, shock, vibration, thermal vacuum cycle, were carried out on the ground before launching, and sensitivity and peak position were also calibrated on the ground. In November 2012, the mass spectrometer was carried by an experimental satellite to 499 km sun synchronization and is still working right now. It successfully detected the atmosphere compositions both in the satellite orbit and gas-emitted from satellite, including O, He, 12 CO 2 , 13 CO 2 , H 2 , N 2 , O 2 , H 2 O, and so on.

  9. Comparison of 3D ion velocity distribution measurements and models in the vicinity of an absorbing boundary oriented obliquely to a magnetic field

    NASA Astrophysics Data System (ADS)

    Henriquez, Miguel F.; Thompson, Derek S.; Kenily, Shane; Khaziev, Rinat; Good, Timothy N.; McIlvain, Julianne; Siddiqui, M. Umair; Curreli, Davide; Scime, Earl E.

    2016-10-01

    Understanding particle distributions in plasma boundary regions is critical to predicting plasma-surface interactions. Ions in the presheath exhibit complex behavior because of collisions and due to the presence of boundary-localized electric fields. Complete understanding of particle dynamics is necessary for understanding the critical problems of tokamak wall loading and Hall thruster channel wall erosion. We report measurements of 3D argon ion velocity distribution functions (IVDFs) in the vicinity of an absorbing boundary oriented obliquely to a background magnetic field. Measurements were obtained via argon ion laser induced fluorescence throughout a spatial volume upstream of the boundary. These distribution functions reveal kinetic details that provide a point-to-point check on particle-in-cell and 1D3V Boltzmann simulations. We present the results of this comparison and discuss some implications for plasma boundary interaction physics.

  10. A Kp-based model of auroral boundaries

    NASA Astrophysics Data System (ADS)

    Carbary, James F.

    2005-10-01

    The auroral oval can serve as both a representation and a prediction of space weather on a global scale, so a competent model of the oval as a function of a geomagnetic index could conveniently appraise space weather itself. A simple model of the auroral boundaries is constructed by binning several months of images from the Polar Ultraviolet Imager by Kp index. The pixel intensities are first averaged into magnetic latitude-magnetic local time (MLT-MLAT) and local time bins, and intensity profiles are then derived for each Kp level at 1 hour intervals of MLT. After background correction, the boundary latitudes of each profile are determined at a threshold of 4 photons cm-2 s1. The peak locations and peak intensities are also found. The boundary and peak locations vary linearly with Kp index, and the coefficients of the linear fits are tabulated for each MLT. As a general rule of thumb, the UV intensity peak shifts 1° in magnetic latitude for each increment in Kp. The fits are surprisingly good for Kp < 6 but begin to deteriorate at high Kp because of auroral boundary irregularities and poor statistics. The statistical model allows calculation of the auroral boundaries at most MLTs as a function of Kp and can serve as an approximation to the shape and extent of the statistical oval.

  11. Nonlinear magnetic responses at the phase boundaries around helimagnetic and skyrmion lattice phases in MnSi: Evaluation of robustness of noncollinear spin texture

    NASA Astrophysics Data System (ADS)

    Tsuruta, K.; Mito, M.; Deguchi, H.; Kishine, J.; Kousaka, Y.; Akimitsu, J.; Inoue, K.

    2018-03-01

    The phase diagram of a cubic chiral magnet MnSi with multiple Dzyaloshinskii-Moriya (DM) vectors as a function of temperature T and dc magnetic field Hdc was investigated using intensity mapping of the odd-harmonic responses of ac magnetization (M1 ω and M3 ω), and the responses at phase boundaries were evaluated according to a prescription [J. Phys. Soc. Jpn. 84, 104707 (2015), 10.7566/JPSJ.84.104707]. By evaluating M3 ω/M1 ω appearing at phase boundaries, the robustness of noncollinear spin texture in both the helimagnetic (HM) and the skyrmion lattice (SkL) phases of MnSi was discussed. The robustness of vortices-type solitonic texture SkL in MnSi is smaller than those of both the single DM HM and chiral soliton lattice phases of a monoaxial chiral magnet Cr1 /3NbS2 , and furthermore the robustness of the multiple DM HM phase in MnSi is smaller than that of its SkL. Through magnetic diagnostics over the wide T -Hdc range, we found a new paramagnetic (PM) region with ac magnetic hysteresis, where spin fluctuations have been observed via electrical magnetochiral effect. The anomalies observed in the previous ultrasonic attenuation measurement correspond to the peak positions of out-of-phase M1 ω. The appearance of a new PM region occurs at a characteristic magnetic field, above which indeed the SkL phase appears. It has us suppose that the new PM region could be a phase with spin fluctuation like the skyrmion gas phase.

  12. Electrodynamic parameters in the nighttime sector during auroral substorms

    NASA Technical Reports Server (NTRS)

    Fujii, R.; Hoffman, R. A.; Anderson, P. C.; Craven, J. D.; Sugiura, M.; Frank, L. A.; Maynard, N. C.

    1994-01-01

    precipitation and aurora appearing in this western and poleward protion of the bulge. The convection reversal is sharp in the west of bulge and surge horn sectors, and near the high-latitude boundary of the upward region 1, with a near stagnation region often extending over a large interval of latitude. In the eastern bulge and east of bulge sectors, the region 1 and 2 FACs are located in the sunward convection region, while a spikelike electric field occasionally appears poleward of the aurora but usually not associated with a pair of FAC sheets. In the eastern bulge, magnetic field data show complicated FAC distributions which correspond to current segments and filamentary currents.

  13. Foreshock ULF wave boundary at Venus

    NASA Astrophysics Data System (ADS)

    Shan, L.; Mazelle, C. X.; Meziane, K.; Romanelli, N. J.; Ge, Y.; Du, A.; Zhang, T.

    2017-12-01

    Foreshock ULF waves are a significant physical phenomenon on the plasma environment for terrestrial planets. The occurrence of ULF waves, associated with backstreaming ions and accelerated at shocks, implies the conditions and properties of the shock and its foreshock. The location of ultra-low frequency (ULF) quasi-monochromatic wave onset upstream of Venus bow shock is explored using Venus Express magnetic field data. We report the existence of a spatial foreshock boundary behind which ULF waves are present. We have found that the ULF wave boundary is sensitive to the interplanetary magnetic field (IMF) direction and appears well defined for a cone angle larger than 30o. In the Venusian foreshock, the slope of the wave boundary with respect to the Sun-Venus direction increase with IMF cone angle. We also found that for the IMF nominal direction at Venus' orbit, the boundary makes an inclination of 70o. Moreover, we have found that the inferred velocity of an ion traveling along the ULF boundary is in a qualitative agreement with a quasi-adiabatic reflection of a portion of the solar wind at the bow shock.

  14. 75 FR 58304 - Navigation and Navigable Waters; Technical, Organizational, and Conforming Amendments, Sector...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-24

    ... [email protected] . If you have questions on viewing the docket, call Renee V. Wright, Program... Sec. 3.65-10 to read as follows: Sec. 3.65-10 Sector Puget Sound Marine Inspection Zone and Captain of the Port Zone. Sector Puget Sound's office is located in Seattle, WA. The boundaries of Sector Puget...

  15. LOCAL INTERSTELLAR MAGNETIC FIELD DETERMINED FROM THE INTERSTELLAR BOUNDARY EXPLORER RIBBON

    SciTech Connect

    Zirnstein, E. J.; Livadiotis, G.; McComas, D. J.

    2016-02-10

    The solar wind emanating from the Sun interacts with the local interstellar medium (LISM), forming the heliosphere. Hydrogen energetic neutral atoms (ENAs) produced by the solar-interstellar interaction carry important information about plasma properties from the boundaries of the heliosphere, and are currently being measured by NASA's Interstellar Boundary Explorer (IBEX). IBEX observations show the existence of a “ribbon” of intense ENA emission projecting a circle on the celestial sphere that is centered near the local interstellar magnetic field (ISMF) vector. Here we show that the source of the IBEX ribbon as a function of ENA energy outside the heliosphere, uniquelymore » coupled to the draping of the ISMF around the heliopause, can be used to precisely determine the magnitude (2.93 ± 0.08 μG) and direction (227.°28 ± 0.°69, 34.°62 ± 0.°45 in ecliptic longitude and latitude) of the pristine ISMF far (∼1000 AU) from the Sun. We find that the ISMF vector is offset from the ribbon center by ∼8.°3 toward the direction of motion of the heliosphere through the LISM, and their vectors form a plane that is consistent with the direction of deflected interstellar neutral hydrogen, thought to be controlled by the ISMF. Our results yield draped ISMF properties close to that observed by Voyager 1, the only spacecraft to directly measure the ISMF close to the heliosphere, and give predictions of the pristine ISMF that Voyager 1 has yet to sample.« less

  16. Local interstellar magnetic field determined from the interstellar boundary explorer ribbon

    DOE PAGES

    Zirnstein, E. J.; Heerikhuisen, J.; Funsten, H. O.; ...

    2016-02-08

    The solar wind emanating from the Sun interacts with the local interstellar medium (LISM), forming the heliosphere. Hydrogen energetic neutral atoms (ENAs) produced by the solar-interstellar interaction carry important information about plasma properties from the boundaries of the heliosphere, and are currently being measured by NASA's Interstellar Boundary Explorer (IBEX). IBEX observations show the existence of a “ribbon” of intense ENA emission projecting a circle on the celestial sphere that is centered near the local interstellar magnetic field (ISMF) vector. Here we show that the source of the IBEX ribbon as a function of ENA energy outside the heliosphere, uniquelymore » coupled to the draping of the ISMF around the heliopause, can be used to precisely determine the magnitude (2.93 ± 0.08 μG) and direction (227.°28 ± 0.°69, 34.°62 ± 0.°45 in ecliptic longitude and latitude) of the pristine ISMF far (~1000 AU) from the Sun. We find that the ISMF vector is offset from the ribbon center by ~8.°3 toward the direction of motion of the heliosphere through the LISM, and their vectors form a plane that is consistent with the direction of deflected interstellar neutral hydrogen, thought to be controlled by the ISMF. Lastly, our results yield draped ISMF properties close to that observed by Voyager 1, the only spacecraft to directly measure the ISMF close to the heliosphere, and give predictions of the pristine ISMF that Voyager 1 has yet to sample.« less

  17. Some Basic Aspects of Magnetohydrodynamic Boundary-Layer Flows

    NASA Technical Reports Server (NTRS)

    Hess, Robert V.

    1959-01-01

    An appraisal is made of existing solutions of magnetohydrodynamic boundary-layer equations for stagnation flow and flat-plate flow, and some new solutions are given. Since an exact solution of the equations of magnetohydrodynamics requires complicated simultaneous treatment of the equations of fluid flow and of electromagnetism, certain simplifying assumptions are generally introduced. The full implications of these assumptions have not been brought out properly in several recent papers. It is shown in the present report that for the particular law of deformation which the magnetic lines are assumed to follow in these papers a magnet situated inside the missile nose would not be able to take up any drag forces; to do so it would have to be placed in the flow away from the nose. It is also shown that for the assumption that potential flow is maintained outside the boundary layer, the deformation of the magnetic lines is restricted to small values. The literature contains serious disagreements with regard to reductions in heat-transfer rates due to magnetic action at the nose of a missile, and these disagreements are shown to be mainly due to different interpretations of reentry conditions rather than more complicated effects. In the present paper the magnetohydrodynamic boundary-layer equation is also expressed in a simple form that is especially convenient for physical interpretation. This is done by adapting methods to magnetic forces which in the past have been used for forces due to gravitational or centrifugal action. The simplified approach is used to develop some new solutions of boundary-layer flow and to reinterpret certain solutions existing in the literature. An asymptotic boundary-layer solution representing a fixed velocity profile and shear is found. Special emphasis is put on estimating skin friction and heat-transfer rates.

  18. Boundaries, Work and Identity Practices: Being "'Asian" Migrant Educational Workers

    ERIC Educational Resources Information Center

    Joseph, Cynthia

    2014-01-01

    This article draws on the concept of boundaries in understanding the identity practices of a group of Malaysian skilled migrant women working in the Australian education sector. Drawing on in-depth interviews with these women on their migration and work experiences, the author explores the concept of boundary work within an educational framework.…

  19. Origin and provenance of spherules and magnetic grains at the Younger Dryas boundary

    PubMed Central

    Wu, Yingzhe; Sharma, Mukul; LeCompte, Malcolm A.; Demitroff, Mark N.; Landis, Joshua D.

    2013-01-01

    One or more bolide impacts are hypothesized to have triggered the Younger Dryas cooling at ∼12.9 ka. In support of this hypothesis, varying peak abundances of magnetic grains with iridium and magnetic microspherules have been reported at the Younger Dryas boundary (YDB). We show that bulk sediment and/or magnetic grains/microspherules collected from the YDB sites in Arizona, Michigan, New Mexico, New Jersey, and Ohio have 187Os/188Os ratios ≥1.0, similar to average upper continental crust (= 1.3), indicating a terrestrial origin of osmium (Os) in these samples. In contrast, bulk sediments from YDB sites in Belgium and Pennsylvania exhibit 187Os/188Os ratios <<1.0 and at face value suggest mixing with extraterrestrial Os with 187Os/188Os of ∼0.13. However, the Os concentration in bulk sample and magnetic grains from Belgium is 2.8 pg/g and 15 pg/g, respectively, much lower than that in average upper continental crust (=31 pg/g), indicating no meteoritic contribution. The YDB site in Pennsylvania is remarkable in yielding 2- to 5-mm diameter spherules containing minerals such as suessite (Fe-Ni silicide) that form at temperatures in excess of 2000 °C. Gross texture, mineralogy, and age of the spherules appear consistent with their formation as ejecta from an impact 12.9 ka ago. The 187Os/188Os ratios of the spherules and their leachates are often low, but Os in these objects is likely terrestrially derived. The rare earth element patterns and Sr and Nd isotopes of the spherules indicate that their source lies in 1.5-Ga Quebecia terrain in the Grenville Province of northeastern North America. PMID:24009337

  20. Newborn Coronal Holes Associated with the Disappearance of Polarity Reversal Boundaries (P46)

    NASA Astrophysics Data System (ADS)

    Shelke, R.

    2006-11-01

    rajendra_shelke@yahoo.co.in Coronal holes play an important role in the occurrence of various kinds of solar events. The geomagnetic activity, coronal transients, type II radio bursts, and soft X ray blowouts have shown their strong association with coronal holes (Webb et al., 1978; Shelke and Pande, 1985; Bhatnagar, 1996; Hewish and Bravo, 1986). Recently, Shelke (2006) has linked the onset of interplanetary erupting stream disturbances with the evolutionary changes in the coronal holes. The present study reveals that there exists some physical relationship between the formation of new coronal holes and the disappearance of polarity reversal boundaries with or without the overlying prominences. About 124 new coronal holes are found to emerge at the locations where polarity reversal boundaries existed prior to their disappearance. Among them, nearly 66% and 18% newborn coronal holes have been associated with disappearing prominences and disappearing small unipolar magnetic regions (UMRs) with encircled polarity reversal boundaries respectively. Coronal holes and quiescent prominences are stable solar features that last for many solar rotations. A coronal hole is indicative of a radial magnetic field of a predominant magnetic polarity at the photosphere, whereas solar prominence overlying the polarity reversal boundary straddles both the polarities of a bipolar magnetic region. The new coronal hole emerges on the Sun, owing to the changes in magnetic field configuration leading to the opening of closed magnetic structure into the corona. The mechanism that leads to the eruption of polarity reversal boundaries with or without prominences seems to be interlinked with the mechanism that converts bipolar magnetic regions into unipolar magnetic regions characterizing coronal holes. The fundamental activity for the onset of erupting polarity reversal boundary seems to be the opening of preexisting closed magnetic structures into a new coronal hole, which can support mass

  1. 76 FR 13508 - Ninth Coast Guard District Sector Realignment; Northern Lake Michigan and Lake Huron

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-14

    ... Station Alpena from Group Sault Ste. Marie to Sectors Lake Michigan and Detroit, respectively. That... boundary adjustment is that Stations Charlevoix and Alpena will be reassigned to Sector Sault Ste. Marie...

  2. Hybrid simulations of Venus' ionospheric magnetization states

    NASA Astrophysics Data System (ADS)

    Wiehle, Stefan; Motschmann, Uwe; Fränz, Markus

    2013-04-01

    The solar wind interaction with the plasma environment of Venus is studied with focus on ionospheric magnetization states using a 3D hybrid simulation code. The plasma environment of Venus was investigated mainly by Pioneer Venus Orbiter (PVO) and the still ongoing Venus Express (VEX) mission. Unlike many other planets, Venus' ionosphere is not shielded by a strong magnetosphere. Hence, data measured by spacecraft like PVO and VEX close to the planet are highly sensitive to solar wind and IMF upstream conditions, which cannot be measured while the spacecraft is inside the magnetosheath region about one hour before and after the closest approach. However, solar wind and IMF are known to change within minutes; ionospheric magnetization states, found by PVO and VEX, are highly dependent on the solar wind upstream pressure and also the magnetic field direction may change rapidly in case of a magnetic sector boundary crossing. When these solar wind induced transition effects occur, the causal change in the solar wind cannot be determined from ionospheric in-situ data. Additionally, with an orbital period of 24 hours, measuring transition timescales of solar wind triggered events is not possible. Our self-consistent simulations aim to provide a global picture of the solar wind interaction with Venus focusing on the effects of upstream fluctuations to the magnetic field in the vicinity of the planet. We use the A.I.K.E.F. (Adaptive Ion Kinetic Electron Fluid) 3D hybrid simulation code to model the entire Venus plasma environment. The simulation grid is refined within the ionosphere in order to resolve strong small-scale gradients of the magnetic field and ion density, a necessity to describe the magnetic field depletion inside the Venus' ionosphere. In contrast to other simulation studies, we apply no boundary conditions for the magnetic field at the planetary surface. Furthermore, we include varying upstream conditions like solar wind velocity and density as well as IMF

  3. The observation of possible reconnection events in the boundary changes of solar coronal holes

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Moses, J. Daniel

    1989-01-01

    Coronal holes are large scale regions of magnetically open fields which are easily observed in solar soft X-ray images. The boundaries of coronal holes are separatrices between large scale regions of open and closed magnetic fields where one might expect to observe evidence of solar magnetic reconnection. Previous studies by Nolte and colleagues using Skylab X-ray images established that large scale (greater than or equal to 9 x 10(4) km) changes in coronal hole boundaries were due to coronal processes, i.e., magnetic reconnection, rather than to photospheric motions. Those studies were limited to time scales of about one day, and no conclusion could be drawn about the size and time scales of the reconnection process at hole boundaries. Sequences of appropriate Skylab X-ray images were used with a time resolution of about 90 min during times of the central meridian passages of the coronal hole labelled Coronal Hole 1 to search for hole boundary changes which can yield the spatial and temporal scales of coronal magnetic reconnection. It was found that 29 of 32 observed boundary changes could be associated with bright points. The appearance of the bright point may be the signature of reconnection between small scale and large scale magnetic fields. The observed boundary changes contributed to the quasi-rigid rotation of Coronal Hole 1.

  4. The effect of guide-field and boundary conditions on the features and signatures of collisionless magnetic reconnection in a stressed X-point collapse

    NASA Astrophysics Data System (ADS)

    Graf von der Pahlen, J.; Tsiklauri, D.

    2015-12-01

    Magnetic X-point collapse is investigated using a 2.5D fully relativistic particle-in-cell simulation, with varying strengths of guide-field as well as open and closed boundary conditions. In the zero guide-field case we discover a new signature of Hall-reconnection in the out-of-plane magnetic field, namely an octupolar pattern, as opposed to the well-studied quadrupolar out-of-plane field of reconnection. The emergence of the octupolar components was found to be caused by ion currents and is a general feature of X-point collapse. In a comparative study of tearing-mode reconnection, signatures of octupolar components are found only in the out-flow region. It is argued that space-craft observations of magnetic fields at reconnection sites may be used accordingly to identify the type of reconnection [1][2]. Further, initial oscillatory reconnection is observed, prior to reconnection onset, generating electro-magnetic waves at the upper-hybrid frequency, matching solar flare progenitor emission. When applying a guide-field, in both open and closed boundary conditions, thinner dissipation regions are obtained and the onset of reconnection is increasingly delayed. Investigations with open boundary conditions show that, for guide-fields close to the strength of the in-plane field, shear flows emerge, leading to the formation of electron flow vortices and magnetic islands [3]. Asymmetries in the components of the generalised Ohm's law across the dissipation region are observed. Extended in 3D geometry, it is shown that locations of magnetic islands and vortices are not constant along the height of the current-sheet. Vortices formed on opposite sites of the current-sheet travel in opposite directions along it, leading to a criss-cross vortex pattern. Possible instabilities resulting from this specific structure formation are to be investigated [4].[1] J. Graf von der Pahlen and D. Tsiklauri, Phys. Plasmas 21, 060705 (2014), [2] J. Graf von der Pahlen and D. Tsiklauri

  5. Lateral temperature variations at the core-mantle boundary deduced from the magnetic field

    NASA Technical Reports Server (NTRS)

    Bloxham, Jeremy; Jackson, Andrew

    1990-01-01

    Recent studies of the secular variation of the earth's magnetic field over periods of a few centuries have suggested that the pattern of fluid motion near the surface of earth's outer core may be strongly influenced by lateral temperature variations in the lowermost mantle. This paper introduces a self-consistent method for finding the temperature variations near the core surface by assuming that the dynamical balance there is geostrophic and that lateral density variations there are thermal in origin. As expected, the lateral temperature variations are very small. Some agreement is found between this pattern and the pattern of topography of the core-mantle boundary, but this does not conclusively answer to what extent core surface motions are controlled by the mantle, rather than being determined by processes in the core.

  6. Auroral activity associated with Kelvin-Helmholtz instability at the inner edge of the low-latitude boundary layer

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Sandholt, P. E.; Burlaga, L. F.

    1994-01-01

    Auroral activity occurred in the late afternoon sector (approx. 16 MLT) in the northern hemisphere during the passage at Earth of an interplanetary magnetic cloud on January 14, 1988. The auroral activity consisted of a very dynamic display which was preceded and followed by quiet auroral displays. During the quiet displays, discrete rayed arcs aligned along the geomagnetic L shells were observed. In the active stage, rapidly evolving spiral forms centered on magnetic zenith were evident. The activity persisted for many minutes and was characterized by the absence of directed motion. They were strongly suggestive of intense filaments of upward field-aligned currents embedded in the large-scale region 1 current system. Distortions of the flux ropes as they connect from the equatorial magnetosphere to the ionosphere were witnessed. We assess as possible generating mechanisms three nonlocal sources known to be associated with field-aligned currents. Of these, partial compressions of the magnetosphere due to variations of solar wind dynamic pressure seem an unlikely source. The possibility that the auroral forms are due to reconnection is investigated but is excluded because the active aurora were observed on the closed field line region just equatorward of the convection reversal boundary. To support this conclusion further, we apply recent results on the mapping of ionospheric regions to the equatorial plane based on the Tsyganenko 1989 model (Kaufmann et al., 1993). We find that for comparable magnetic activity the aurora map to the equatorial plane at X(sub GSM) = approx. 3 R(sub E) and approx. 2 R(sub E) inward of the magnetopause, that is, the inner edge of the boundary layer close to dusk. Since the auroral forms are manifestly associated with magnetic field shear, a vortical motion at the equatorial end of the flux rope is indicated, making the Kelvin-Helmholtz instability acting at the inner edge of the low-latitude boundary layer the most probable generating

  7. The Solar Wind-Mars Interaction Boundaries in Three Dimensions

    NASA Astrophysics Data System (ADS)

    Gruesbeck, J.; Espley, J. R.; Connerney, J. E. P.; DiBraccio, G. A.; Soobiah, Y. I. J.

    2017-12-01

    The Martian magnetosphere is a product of the interaction of Mars with the interplanetary magnetic field and the supersonic solar wind. A bow shock forms upstream of the planet as the solar wind is diverted around the planet. Closer to the planet another boundary is located that separates the shock-heated solar wind plasma from the planetary plasma in the Martian magnetosphere. The Martian magnetosphere is induced by the pile-up of the interplanetary magnetic field. This induced magnetospheric boundary (IMB) has been referred to by different names, in part due to the observations available at the time. The location of these boundaries have been previously analyzed using data from Phobos 2, Mars Global Surveyor, and Mars Express resulting in models describing their average shapes. Observations of individual transitions demonstrate that it is a boundary with a finite thickness. The MAVEN spacecraft has been in orbit about Mars since November 2014 resulting in many encounters of the spacecraft with the boundaries. Using data from the Particle and Fields Package (PFP), we identify over 1000 bow shock crossings and over 4000 IMB crossings that we use to model the average locations. We model the boundaries as a 3-dimensional surface allowing observations of asymmetry. The average location of the bow shock and IMB lies further from the planet in the southern hemisphere, where stronger crustal fields are present. The MAVEN PFP dataset allows concurrent observations of the magnetic field and plasma environment to investigate the nature of the IMB and the relationship of the boundary to the different plasma signatures. Finally, we model the upstream and downstream encounters of the boundaries separately to produce shell models that quantify the finite thicknesses of the boundaries.

  8. Boundary conditions and formation of pure spin currents in magnetic field

    NASA Astrophysics Data System (ADS)

    Eliashvili, Merab; Tsitsishvili, George

    2017-09-01

    Schrödinger equation for an electron confined to a two-dimensional strip is considered in the presence of homogeneous orthogonal magnetic field. Since the system has edges, the eigenvalue problem is supplied by the boundary conditions (BC) aimed in preventing the leakage of matter away across the edges. In the case of spinless electrons the Dirichlet and Neumann BC are considered. The Dirichlet BC result in the existence of charge carrying edge states. For the Neumann BC each separate edge comprises two counterflow sub-currents which precisely cancel out each other provided the system is populated by electrons up to certain Fermi level. Cancelation of electric current is a good starting point for developing the spin-effects. In this scope we reconsider the problem for a spinning electron with Rashba coupling. The Neumann BC are replaced by Robin BC. Again, the two counterflow electric sub-currents cancel out each other for a separate edge, while the spin current survives thus modeling what is known as pure spin current - spin flow without charge flow.

  9. Transport in a field aligned magnetized plasma/neutral gas boundary: the end of the plasma

    NASA Astrophysics Data System (ADS)

    Cooper, Christopher Michael

    The objective of this dissertation is to characterize the physics of a boundary layer between a magnetized plasma and a neutral gas along the direction of a confining magnetic field. A series of experiments are performed at the Enormous Toroidal Plasma Device (ETPD) at UCLA to study this field aligned Neutral Boundary Layer (NBL) at the end of the plasma. A Lanthanum Hexaboride (LaB6) cathode and semi-transparent anode creates a magnetized, current-free helium plasma which terminates on a neutral helium gas without touching any walls. Probes are inserted into the plasma to measure the basic plasma parameters and study the transport in the NBL. The experiment is performed in the weakly ionized limit where the plasma density (ne) is much less than the neutral density (nn) such that ne/nn < 5%. The NBL is characterized by a field-aligned electric field which begins at the point where the plasma pressure equilibrates with the neutral gas pressure. Beyond the pressure equilibration point the electrons and ions lose their momentum by collisions with the neutral gas and come to rest. An electric field is established self consistently to maintain a current-free termination through equilibration of the different species' stopping rates in the neutral gas. The electric field resembles a collisional quasineutral sheath with a length 10 times the electron-ion collision length, 100 times the neutral collision length, and 10,000 times the Debye length. Collisions with the neutral gas dominate the losses in the system. The measured plasma density loss rates are above the classical cross-field current-free ambipolar rate, but below the anomalous Bohm diffusion rate. The electron temperature is below the ionization threshold of the gas, 2.2 eV in helium. The ions are in thermal equilibrium with the neutral gas. A generalized theory of plasma termination in a Neutral Boundary Layer is applied to this case using a two-fluid, current-free, weakly ionized transport model. The electron

  10. Boundary plasma heat flux width measurements for poloidal magnetic fields above 1 Tesla in the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Brunner, Dan; Labombard, Brian; Kuang, Adam; Terry, Jim; Alcator C-Mod Team

    2017-10-01

    The boundary heat flux width, along with the total power flowing into the boundary, sets the power exhaust challenge for tokamaks. A multi-machine boundary heat flux width database found that the heat flux width in H-modes scaled inversely with poloidal magnetic field (Bp) and was independent of machine size. The maximum Bp in the database was 0.8 T, whereas the ITER 15 MA, Q =10 scenario will be 1.2 T. New measurements of the boundary heat flux width in Alcator C-Mod extend the international database to plasmas with Bp up to 1.3 T. C-Mod was the only experiment able to operate at ITER-level Bp. These new measurements are from over 300 plasma shots in L-, I-, and EDA H-modes spanning essentially the whole operating space in C-Mod. We find that the inverse-Bp dependence of the heat flux width in H-modes continues to ITER-level Bp, further reinforcing the empirical projection of 500 μm heat flux width for ITER. We find 50% scatter around the inverse-Bp scaling and are searching for the `hidden variables' causing this scatter. Supported by USDoE award DE-FC02-99ER54512.

  11. Bulk Single Crystal-Like Structural and Magnetic Characteristics of Epitaxial Spinel Ferrite Thin Films with Elimination of Antiphase Boundaries.

    PubMed

    Singh, Amit V; Khodadadi, Behrouz; Mohammadi, Jamileh Beik; Keshavarz, Sahar; Mewes, Tim; Negi, Devendra Singh; Datta, Ranjan; Galazka, Zbigniew; Uecker, Reinhard; Gupta, Arunava

    2017-08-01

    Spinel ferrite NiFe 2 O 4 thin films have been grown on three isostructural substrates, MgAl 2 O 4 , MgGa 2 O 4 , and CoGa 2 O 4 using pulsed laser deposition. These substrates have lattice mismatches of 3.1%, 0.8%, and 0.2%, respectively, with NiFe 2 O 4 . As expected, the films grown on MgAl 2 O 4 substrate show the presence of the antiphase boundary defects. However, no antiphase boundaries (APBs) are observed for films grown on near-lattice-matched substrates MgGa 2 O 4 and CoGa 2 O 4 . This demonstrates that by using isostructural and lattice-matched substrates, the formation of APBs can be avoided in NiFe 2 O 4 thin films. Consequently, static and dynamic magnetic properties comparable with the bulk can be realized. Initial results indicate similar improvements in film quality and magnetic properties due to the elimination of APBs in other members of the spinel ferrite family, such as Fe 3 O 4 and CoFe 2 O 4 , which have similar crystallographic structure and lattice constants as NiFe 2 O 4 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Magnetopause Boundary Processes Throughout the Solar System

    NASA Astrophysics Data System (ADS)

    Masters, A.

    2014-12-01

    Earth is not the only planet in the Solar System with a natural magnetic shield. Mercury, Jupiter, Saturn, Uranus, and Neptune are similarly protected from the solar wind and cosmic rays. However, like our planet, the magnetic shielding of each of these magnetized planets can break down, driving energy flow through each planetary magnetosphere. Although studies of the magnetopause boundary of Earth's magnetosphere have shed considerable light on the processes that lead to this breakdown, the extent to which we can apply this understanding to the diverse space plasma environments surrounding other planets remains unclear. Here we review what we have learnt so far about the operation of magnetopause boundary processes at all the magnetized planets in the Solar System, and outline some of the relevant outstanding questions. We start by consolidating present understanding of terrestrial magnetopause processes, which is our reference when considering other boundaries. We focus on selected processes (magnetic reconnection, Kelvin-Helmholtz instability), compare how we expect them to operate at each planetary magnetopause, and assess whether or not this is consistent with in situ spacecraft observations. For each planetary magnetosphere we then discuss the nature of the total interaction with the solar wind, and whether this is expected to be dominant over internal drivers of magnetospheric dynamics. A combination of further spacecraft exploration and dedicated numerical modeling is required in order to address the many outstanding questions concerning this topic. Progress in this direction would have broad implications for other space plasma systems, in our solar system and beyond.

  13. Extension of the SIESTA MHD equilibrium code to free-plasma-boundary problems

    DOE PAGES

    Peraza-Rodriguez, Hugo; Reynolds-Barredo, J. M.; Sanchez, Raul; ...

    2017-08-28

    Here, SIESTA is a recently developed MHD equilibrium code designed to perform fast and accurate calculations of ideal MHD equilibria for three-dimensional magnetic configurations. Since SIESTA does not assume closed magnetic surfaces, the solution can exhibit magnetic islands and stochastic regions. In its original implementation SIESTA addressed only fixed-boundary problems. That is, the shape of the plasma edge, assumed to be a magnetic surface, was kept fixed as the solution iteratively converges to equilibrium. This condition somewhat restricts the possible applications of SIESTA. In this paper we discuss an extension that will enable SIESTA to address free-plasma-boundary problems, opening upmore » the possibility of investigating problems in which the plasma boundary is perturbed either externally or internally. As an illustration, SIESTA is applied to a configuration of the W7-X stellarator.« less

  14. Extension of the SIESTA MHD equilibrium code to free-plasma-boundary problems

    SciTech Connect

    Peraza-Rodriguez, Hugo; Reynolds-Barredo, J. M.; Sanchez, Raul

    Here, SIESTA is a recently developed MHD equilibrium code designed to perform fast and accurate calculations of ideal MHD equilibria for three-dimensional magnetic configurations. Since SIESTA does not assume closed magnetic surfaces, the solution can exhibit magnetic islands and stochastic regions. In its original implementation SIESTA addressed only fixed-boundary problems. That is, the shape of the plasma edge, assumed to be a magnetic surface, was kept fixed as the solution iteratively converges to equilibrium. This condition somewhat restricts the possible applications of SIESTA. In this paper we discuss an extension that will enable SIESTA to address free-plasma-boundary problems, opening upmore » the possibility of investigating problems in which the plasma boundary is perturbed either externally or internally. As an illustration, SIESTA is applied to a configuration of the W7-X stellarator.« less

  15. Magnetism of a relaxed single atom vacancy in graphene

    NASA Astrophysics Data System (ADS)

    Wu, Yunyi; Hu, Yonghong; Xue, Li; Sun, Tieyu; Wang, Yu

    2018-04-01

    It has been suggested in literature that defects in graphene (e.g. absorbed atoms and vacancies) may induce magnetizations due to unpaired electrons. The nature of magnetism, i.e. ferromagnetic or anti-ferromagnetic, is dependent on a number of structural factors including locations of magnetic moments and lattice symmetry. In the present work we investigated the influence of a relaxed single atom vacancy in garphnene on magnetization which were obtained under different pinning boundary conditions, aiming to achieve a better understanding of the magnetic behaviors of graphene. Through first principles calculations, we found that major spin polarizations occur on atoms that deviate slightly from their original lattice positions, and pinning boundaries could also affect the relaxed positions of atoms and determine which atom(s) would become the main source(s) of total spin polarizations and magnetic moments. When the pinning boundary condition is free, a special non-magnetic and semi-conductive structure may be obtained, suggesting that magnetization should more readily occur under pinning boundary conditions.

  16. Effects of reconstructed magnetic field from sparse noisy boundary measurements on localization of active neural source.

    PubMed

    Shen, Hui-min; Lee, Kok-Meng; Hu, Liang; Foong, Shaohui; Fu, Xin

    2016-01-01

    Localization of active neural source (ANS) from measurements on head surface is vital in magnetoencephalography. As neuron-generated magnetic fields are extremely weak, significant uncertainties caused by stochastic measurement interference complicate its localization. This paper presents a novel computational method based on reconstructed magnetic field from sparse noisy measurements for enhanced ANS localization by suppressing effects of unrelated noise. In this approach, the magnetic flux density (MFD) in the nearby current-free space outside the head is reconstructed from measurements through formulating the infinite series solution of the Laplace's equation, where boundary condition (BC) integrals over the entire measurements provide "smooth" reconstructed MFD with the decrease in unrelated noise. Using a gradient-based method, reconstructed MFDs with good fidelity are selected for enhanced ANS localization. The reconstruction model, spatial interpolation of BC, parametric equivalent current dipole-based inverse estimation algorithm using reconstruction, and gradient-based selection are detailed and validated. The influences of various source depths and measurement signal-to-noise ratio levels on the estimated ANS location are analyzed numerically and compared with a traditional method (where measurements are directly used), and it was demonstrated that gradient-selected high-fidelity reconstructed data can effectively improve the accuracy of ANS localization.

  17. Proterozoic crustal boundary in the southern part of the Illinois Basin

    USGS Publications Warehouse

    Heigold, P.C.; Kolata, Dennis R.

    1993-01-01

    Recently acquired COCORP and proprietary seismic reflection data in the southern part of the Illinois Basin, combined with other geological and geophysical data, indicate that a WNW-trending Proterozoic terrane boundary (40 km wide) lies within basement. The boundary is characterized by the termination of subhorizontal Proterozoic reflectors and associated diffraction patterns along a line coinciding with the major magnetic lineament in this region (South Central Magnetic Lineament). North of the boundary, where reflectors thought to represent a sequence of layered Proterozoic rocks in the upper crust are widespread and as much as 11 km thick, total magnetic intensity values are relatively high, suggesting layers of rock with high magnetic susceptibility. To the south, the Proterozoic rocks are acoustically transparent on seismic reflection sections and total magnetic intensity values are relatively low. Moreover, relatively high Bouguer gravity anomaly values to the south may be caused by a dense, altered, lower crustal layer similar to that interpreted from deep seismic refraction studies to underlie the northern Mississippi Embayment. The boundary lies along the projected trend of the northern margin of the Early Proterozoic Central Plains orogen and we suggest that it marks the convergent margin of this orogen. Reactivation of the boundary and the associated zone of weakness during late Paleozoic times apparently resulted in structural deformation in the southern part of the Illinois Basin, including movement along the Cottage Grove Fault System and Ste. Genevieve Fault Zone and igneous activity at Hicks Dome. In addition to the role played by this crustal boundary in the evolution of the Illinois Basin, its location between the Wabash Valley Seismic Zone to the northeast and the New Madrid Seismic Zone to the southwest may be a significant factor in present-day seismicity. ?? 1993.

  18. Small Magnetic Sensors for Space Applications

    PubMed Central

    Díaz-Michelena, Marina

    2009-01-01

    Small magnetic sensors are widely used integrated in vehicles, mobile phones, medical devices, etc for navigation, speed, position and angular sensing. These magnetic sensors are potential candidates for space sector applications in which mass, volume and power savings are important issues. This work covers the magnetic technologies available in the marketplace and the steps towards their implementation in space applications, the actual trend of miniaturization the front-end technologies, and the convergence of the mature and miniaturized magnetic sensor to the space sector through the small satellite concept. PMID:22574012

  19. Commercial-scale recycling of NdFeB-type magnets with grain boundary modification yields products with 'designer properties' that exceed those of starting materials.

    PubMed

    Zakotnik, M; Tudor, C O

    2015-10-01

    NdFeB-type magnets dominate the market for high performance magnetic materials, yet production of 'virgin' magnets via mining is environmentally, financially and energetically costly. Hence, interest is growing in 'magnet to magnet' recycling schemes that offer the potential for cheaper, more environmentally-friendly solutions to the world's growing appetite for rare-earth based magnetic materials. Unfortunately, previously described recycling processes only partially capitalise on this potential, because the methods described to date are limited to 'laboratory scale' or operate only under ideal conditions and result in products that fail to recapture the coercivity of the starting, scrap materials. Herein, we report a commercial scale process (120 kg batches) that completely recovers the properties of the starting scrap magnets. Indeed, 'grain boundary modification', via careful addition of a proprietary mix of blended elements, produces magnets with 'designer properties' that can exceed those of the starting materials and can be closely tailored to meet a wide variety of end-user applications, including high-coercivity (>2000 kA/m), sintered magnets suitable for motor applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. On the role of the grain size in the magnetic behavior of sintered permanent magnets

    NASA Astrophysics Data System (ADS)

    Efthimiadis, K. G.; Ntallis, N.

    2018-02-01

    In this work the finite elements method is used to simulate, by micromagnetic modeling, the magnetic behavior of sintered anisotropic magnets. Hysteresis loops were simulated for different grain sizes in an oriented multigrain sample. By keeping out other parameters that contribute to the magnetic microstructure, such as the sample size, the grain morphology and the grain boundaries mismatch, it has been found that the grain size affects the magnetic properties only if the grains are exchange-decoupled. In this case, as the grain size decreases, a decrease in the nucleation field of a reverse magnetic domain is observed and an increase in the coercive field due to the pinning of the magnetic domain walls at the grain boundaries.

  1. Cross-sector Service Provision in Health and Social Care: An Umbrella Review.

    PubMed

    Winters, Shannon; Magalhaes, Lilian; Anne Kinsella, Elizabeth; Kothari, Anita

    2016-04-08

    Meeting the complex health needs of people often requires interaction among numerous different sectors. No one service can adequately respond to the diverse care needs of consumers. Providers working more effectively together is frequently touted as the solution. Cross-sector service provision is defined as independent, yet interconnected sectors working together to better meet the needs of consumers and improve the quality and effectiveness of service provision. Cross-sector service provision is expected, yet much remains unknown about how it is conceptualised or its impact on health status. This umbrella review aims to clarify the critical attributes that shape cross-sector service provision by presenting the current state of the literature and building on the findings of the 2004 review by Sloper. Literature related to cross-sector service provision is immense, which poses a challenge for decision makers wishing to make evidence-informed decisions. An umbrella review was conducted to articulate the overall state of cross-sector service provision literature and examine the evidence to allow for the discovery of consistencies and discrepancies across the published knowledge base. Sixteen reviews met the inclusion criteria. Seven themes emerged: Focusing on the consumer, developing a shared vision of care, leadership involvement, service provision across the boundaries, adequately resourcing the arrangement, developing novel arrangements or aligning with existing relationships, and strengthening connections between sectors. Future research from a cross-organisational, rather than individual provider, perspective is needed to better understand what shapes cross-sector service provision at the boundaries. Findings aligned closely with the work done by Sloper and raise red flags related to reinventing what is already known. Future researchers should look to explore novel areas rather than looking into areas that have been explored at length. Evaluations of out

  2. Is There a Magnet-School Effect? A Multisite Study of MSAP-Funded Magnet Schools

    ERIC Educational Resources Information Center

    Wang, Jia; Schweig, Jonathan D.; Herman, Joan L.

    2017-01-01

    Magnet schools are one of the largest sectors of choice schools in the United States. In this study, we explored the heterogeneity in magnet-school effects on student achievement by examining 24 magnet schools, funded under the Magnet Schools Assistance Program (MSAP), in 5 school districts across 4 states. The magnet effects were synthesized…

  3. Solving free-plasma-boundary problems with the SIESTA MHD code

    NASA Astrophysics Data System (ADS)

    Sanchez, R.; Peraza-Rodriguez, H.; Reynolds-Barredo, J. M.; Tribaldos, V.; Geiger, J.; Hirshman, S. P.; Cianciosa, M.

    2017-10-01

    SIESTA is a recently developed MHD equilibrium code designed to perform fast and accurate calculations of ideal MHD equilibria for 3D magnetic configurations. It is an iterative code that uses the solution obtained by the VMEC code to provide a background coordinate system and an initial guess of the solution. The final solution that SIESTA finds can exhibit magnetic islands and stochastic regions. In its original implementation, SIESTA addressed only fixed-boundary problems. This fixed boundary condition somewhat restricts its possible applications. In this contribution we describe a recent extension of SIESTA that enables it to address free-plasma-boundary situations, opening up the possibility of investigating problems with SIESTA in which the plasma boundary is perturbed either externally or internally. As an illustration, the extended version of SIESTA is applied to a configuration of the W7-X stellarator.

  4. Petrological, Magnetic and Geochemical Characterization of Cretaceous-Paleogene Boundary El Mimbral and La Lajilla Sections, Northeastern Mexico

    NASA Astrophysics Data System (ADS)

    Ortega Nieto, A.; Fucugauchi, J. U.; Perez-Cruz, L. L.

    2009-12-01

    We present initial results of a petrological, magnetic and geochemical study of El Mimbral and La Lajilla sections that span the Cretaceous-Paleogene (K-Pg) boundary. K-Pg sections in northeastern Mexico have been intensively studied in past years, mainly because of their relationship to the Chicxulub crater in the Yucatan platform and for investigating the nature, origin, stratigraphic relations and age of the impact ejecta deposits. The K-Pg boundary is preserved in between hemipelagic marls and limestones of the Mendez (Maastrichtian) and Velasco (Paleocene) formations. The two sections are situated about 1000 km away from Chicxulub and K-Pg deposits are part of the proximal ejecta and the complex channelized siliciclastic units. We had separated the siliciclastic units into two parts, with a basal coarse poorly graded spherulitic bed some 0.2 to 1 m thick and a second part with several sandstone siltstone beds that have been grouped in various ways in previous studies. In the field, samples were collected across stratigraphic profiles for rock magnetic, petrological and geochemical analyses. Using field observations and analytical data, detailed columns for the two localities are prepared. Rock magnetic measurements include susceptibility, remanent and isothermal magnetization and remanent coercivity. Magnetic hysteresis loops and IRM and back-field demagnetization were measured for samples of spherulitic bed. X-ray fluorescence analyses on whole rock were complemented with previous data obtained for the Mimbral section by atomic absorption spectrometry and inductively coupled plasma mass spectrometry (including platinum group elements). Further detailed analysis concentrated in the ejecta material. The spherulitic bed is characterized by Fe-Mg rich chlorite and Si-Al-K rich glass spherules and carbonate accretionary lapilli spherules. The silicic component spherules are altered to calcite or chlorite-smectite, with some retaining glass cores. Spherules have

  5. On the upstream boundary of electron foreshocks in the solar wind

    NASA Technical Reports Server (NTRS)

    Zimbardo, G.; Veltri, P.

    1995-01-01

    The upstream boundary of electron foreshocks is defined as the path of the fastest electrons reflected by collisionless shocks and moving along the magnetic field in the solar wind. Considerable levels of magnetic fluctuations are found in these regions of the solar wind, and their effect is to create both a broadening and a fine structure of the electron foreshock boundary. The magnetic structure is studied by means of a 3-D numerical simulation of a turbulent magnetic field. Enhanced, anomalous diffusion is found, (Delta x(exp 2)) varies as s(sup alpha), where alpha is greater than 1 for typical values of the parameters (here, Delta x(exp 2) is the mean square width of the tangent magnetic surface and s is the field line length). This corresponds to a Levy flight regime for the magnetic field line random walk, and allows very efficient electron propagation perpendicular to the magnetic field. Implications on the observations of planetary foreshocks and of the termination shock foreshock are considered.

  6. Analysis of Aircraft Clusters to Measure Sector-Independent Airspace Congestion

    NASA Technical Reports Server (NTRS)

    Bilimoria, Karl D.; Lee, Hilda Q.

    2005-01-01

    boundaries. Figure 1 , reproduced from Ref. 1, depicts an example traffic situation. When the situation is analyzed by sector boundaries (left side of figure), a Dynamic Density metric would identify excessive congestion in the central sector. When the same traffic situation is analyzed independent of sector boundaries (right side of figure), a Gaggle Density metric would identify congestion in two dynamically defined areas covering portions of several sectors. The first step towards measuring airspace-independent congestion is to identify aircraft clusters, i.e., groups of closely spaced aircraft. The objective of this work is to develop techniques to detect and classify clusters of aircraft.

  7. Commissioning the cryogenic system of the first LHC sector

    SciTech Connect

    Millet, F.; Claudet, S.; Ferlin, G.

    2007-12-01

    The LHC machine, composed of eight sectors with superconducting magnets and accelerating cavities, requires a complex cryogenic system providing high cooling capacities (18 kW equivalent at 4.5 K and 2.4 W at 1.8 K per sector produced in large cold boxes and distributed via 3.3-km cryogenic transfer lines). After individual reception tests of the cryogenic subsystems (cryogen storages, refrigerators, cryogenic transfer lines and distribution boxes) performed since 2000, the commissioning of the cryogenic system of the first LHC sector has been under way since November 2006. After a brief introduction to the LHC cryogenic system and its specificities, the commissioningmore » is reported detailing the preparation phase (pressure and leak tests, circuit conditioning and flushing), the cool-down sequences including the handling of cryogenic fluids, the magnet powering phase and finally the warm-up. Preliminary conclusions on the commissioning of the first LHC sector will be drawn with the review of the critical points already solved or still pending. The last part of the paper reports on the first operational experience of the LHC cryogenic system in the perspective of the commissioning of the remaining LHC sectors and the beam injection test.« less

  8. Emission of magnetosound from MHD-unstable shear flow boundaries

    NASA Astrophysics Data System (ADS)

    Turkakin, H.; Rankin, R.; Mann, I. R.

    2016-09-01

    The emission of propagating MHD waves from the boundaries of flow channels that are unstable to the Kelvin-Helmholtz Instability (KHI) in magnetized plasma is investigated. The KHI and MHD wave emission are found to be two competing processes. It is shown that the fastest growing modes of the KHI surface waves do not coincide with efficient wave energy transport away from a velocity shear boundary. MHD wave emission is found to be inefficient when growth rates of KHI surface waves are maximum, which corresponds to the situation where the ambient magnetic field is perpendicular to the flow channel velocity vector. The efficiency of wave emission increases with increasing magnetic field tension, which in Earth's magnetosphere likely dominates along the nightside magnetopause tailward of the terminator, and within earthward Bursty Bulk Flows (BBFs) in the inner plasma sheet. MHD wave emission may also dominate in Supra-Arcade Downflows (SADs) in the solar corona. Our results suggest that efficient emission of propagating MHD waves along BBF and SAD boundaries can potentially explain observations of deceleration and stopping of BBFs and SADs.

  9. Dynamo Tests for Stratification Below the Core-Mantle Boundary

    NASA Astrophysics Data System (ADS)

    Olson, P.; Landeau, M.

    2017-12-01

    Evidence from seismology, mineral physics, and core dynamics points to a layer with an overall stable stratification in the Earth's outer core, possibly thermal in origin, extending below the core-mantle boundary (CMB) for several hundred kilometers. In contrast, energetic deep mantle convection with elevated heat flux implies locally unstable thermal stratification below the CMB in places, consistent with interpretations of non-dipole geomagnetic field behavior that favor upwelling flows below the CMB. Here, we model the structure of convection and magnetic fields in the core using numerical dynamos with laterally heterogeneous boundary heat flux in order to rationalize this conflicting evidence. Strongly heterogeneous boundary heat flux generates localized convection beneath the CMB that coexists with an overall stable stratification there. Partially stratified dynamos have distinctive time average magnetic field structures. Without stratification or with stratification confined to a thin layer, the octupole component is small and the CMB magnetic field structure includes polar intensity minima. With more extensive stratification, the octupole component is large and the magnetic field structure includes intense patches or high intensity lobes in the polar regions. Comparisons with the time-averaged geomagnetic field are generally favorable for partial stratification in a thin layer but unfavorable for stratification in a thick layer beneath the CMB.

  10. Health sector reform and public sector health worker motivation: a conceptual framework.

    PubMed

    Franco, Lynne Miller; Bennett, Sara; Kanfer, Ruth

    2002-04-01

    Motivation in the work context can be defined as an individual's degree of willingness to exert and maintain an effort towards organizational goals. Health sector performance is critically dependent on worker motivation, with service quality, efficiency, and equity, all directly mediated by workers' willingness to apply themselves to their tasks. Resource availability and worker competence are essential but not sufficient to ensure desired worker performance. While financial incentives may be important determinants of worker motivation, they alone cannot and have not resolved all worker motivation problems. Worker motivation is a complex process and crosses many disciplinary boundaries, including economics, psychology, organizational development, human resource management, and sociology. This paper discusses the many layers of influences upon health worker motivation: the internal individual-level determinants, determinants that operate at organizational (work context) level, and determinants stemming from interactions with the broader societal culture. Worker motivation will be affected by health sector reforms which potentially affect organizational culture, reporting structures, human resource management, channels of accountability, types of interactions with clients and communities, etc. The conceptual model described in this paper clarifies ways in which worker motivation is influenced and how health sector reform can positively affect worker motivation. Among others, health sector policy makers can better facilitate goal congruence (between workers and the organizations they work for) and improved worker motivation by considering the following in their design and implementation of health sector reforms: addressing multiple channels for worker motivation, recognizing the importance of communication and leadership for reforms, identifying organizational and cultural values that might facilitate or impede implementation of reforms, and understanding that reforms

  11. 33 CFR 3.65-10 - Sector Seattle: Puget Sound Marine Inspection Zone and Captain of the Port Zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Sector Seattle: Puget Sound...: Puget Sound Marine Inspection Zone and Captain of the Port Zone. Sector Seattle's office is located in Seattle, WA. The boundaries of Sector Seattle's Puget Sound Marine Inspection and Captain of the Port...

  12. Instantons in Script N = 2 magnetized D-brane worlds

    NASA Astrophysics Data System (ADS)

    Billò, Marco; Frau, Marialuisa; Pesando, Igor; Di Vecchia, Paolo; Lerda, Alberto; Marotta, Raffaele

    2007-10-01

    In a toroidal orbifold of type IIB string theory we study instanton effects in Script N = 2 super Yang-Mills theories engineered with systems of wrapped magnetized D9 branes and Euclidean D5 branes. We analyze the various open string sectors in this brane system and study the 1-loop amplitudes described by annulus diagrams with mixed boundary conditions, explaining their rôle in the stringy instanton calculus. We show in particular that the non-holomorphic terms in these annulus amplitudes precisely reconstruct the appropriate Kähler metric factors that are needed to write the instanton correlators in terms of purely holomorphic variables. We also explicitly derive the correct holomorphic structure of the instanton induced low energy effective action in the Coulomb branch.

  13. Renewing Occupational Cultures--Bridging Boundaries in Learning Spaces

    ERIC Educational Resources Information Center

    Kalliola, Satu; Nakari, Risto

    2007-01-01

    Professional bureaucracies of the Finnish municipal services are challenged by many modernization pressures manifested currently in the form of New Public Management. Along with efficiency demands the new emphasis is on the provision of client-oriented services by the means of multi-professional teamwork crossing the traditional sector boundaries.…

  14. 33 CFR 3.05-30 - Sector New York Marine Inspection Zone and Captain of the Port Zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Sector New York Marine Inspection... CAPTAIN OF THE PORT ZONES First Coast Guard District § 3.05-30 Sector New York Marine Inspection Zone and Captain of the Port Zone. Sector New York's office is located in New York City, NY. The boundaries of...

  15. Asymmetric Kelvin-Helmholtz Instability at Jupiter's Magnetopause Boundary: Implications for Corotation-Dominated Systems

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Delamere, P. A.; Ma, X.; Burkholder, B.; Wiltberger, M.; Lyon, J. G.; Merkin, V. G.; Sorathia, K. A.

    2018-01-01

    The multifluid Lyon-Fedder-Mobarry (MFLFM) global magnetosphere model is used to study the interactions between solar wind and rapidly rotating, internally driven Jupiter magnetosphere. The MFLFM model is the first global simulation of Jupiter magnetosphere that captures the Kelvin-Helmholtz instability (KHI) in the critically important subsolar region. Observations indicate that Kelvin-Helmholtz vortices are found predominantly in the dusk sector. Our simulations explain that this distribution is driven by the growth of KHI modes in the prenoon and subsolar region (e.g., >10 local time) that are advected by magnetospheric flows to the dusk sector. The period of density fluctuations at the dusk terminator flank (18 magnetic local time, MLT) is roughly 1.4 h compared with 7.2 h at the dawn flank (6 MLT). Although the simulations are only performed using parameters of the Jupiter's magnetosphere, the results may also have implications for solar wind-magnetosphere interactions at other corotation-dominated systems such as Saturn. For instance, the simulated average azimuthal speed of magnetosheath flows exhibit significant dawn-dusk asymmetry, consistent with recent observations at Saturn. The results are particularly relevant for the ongoing Juno mission and the analysis of dawnside magnetopause boundary crossings for other planetary missions.

  16. Photospheric Magnetic Flux Transport - Supergranules Rule

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.; Rightmire-Upton, Lisa

    2012-01-01

    Observations of the transport of magnetic flux in the Sun's photosphere show that active region magnetic flux is carried far from its origin by a combination of flows. These flows have previously been identified and modeled as separate axisymmetric processes: differential rotation, meridional flow, and supergranule diffusion. Experiments with a surface convective flow model reveal that the true nature of this transport is advection by the non-axisymmetric cellular flows themselves - supergranules. Magnetic elements are transported to the boundaries of the cells and then follow the evolving boundaries. The convective flows in supergranules have peak velocities near 500 m/s. These flows completely overpower the superimposed 20 m/s meridional flow and 100 m/s differential rotation. The magnetic elements remain pinned at the supergranule boundaries. Experiments with and without the superimposed axisymmetric photospheric flows show that the axisymmetric transport of magnetic flux is controlled by the advection of the cellular pattern by underlying flows representative of deeper layers. The magnetic elements follow the differential rotation and meridional flow associated with the convection cells themselves -- supergranules rule!

  17. Traveling waves in a magnetized Taylor-Couette flow.

    PubMed

    Liu, Wei; Goodman, Jeremy; Ji, Hantao

    2007-07-01

    We investigate numerically a traveling wave pattern observed in experimental magnetized Taylor-Couette flow at low magnetic Reynolds number. By accurately modeling viscous and magnetic boundaries in all directions, we reproduce the experimentally measured wave patterns and their amplitudes. Contrary to previous claims, the waves are shown to be transiently amplified disturbances launched by viscous boundary layers, rather than globally unstable magnetorotational modes.

  18. A new technique for observationally derived boundary conditions for space weather

    NASA Astrophysics Data System (ADS)

    Pagano, Paolo; Mackay, Duncan Hendry; Yeates, Anthony Robinson

    2018-04-01

    Context. In recent years, space weather research has focused on developing modelling techniques to predict the arrival time and properties of coronal mass ejections (CMEs) at the Earth. The aim of this paper is to propose a new modelling technique suitable for the next generation of Space Weather predictive tools that is both efficient and accurate. The aim of the new approach is to provide interplanetary space weather forecasting models with accurate time dependent boundary conditions of erupting magnetic flux ropes in the upper solar corona. Methods: To produce boundary conditions, we couple two different modelling techniques, MHD simulations and a quasi-static non-potential evolution model. Both are applied on a spatial domain that covers the entire solar surface, although they extend over a different radial distance. The non-potential model uses a time series of observed synoptic magnetograms to drive the non-potential quasi-static evolution of the coronal magnetic field. This allows us to follow the formation and loss of equilibrium of magnetic flux ropes. Following this a MHD simulation captures the dynamic evolution of the erupting flux rope, when it is ejected into interplanetary space. Results.The present paper focuses on the MHD simulations that follow the ejection of magnetic flux ropes to 4 R⊙. We first propose a technique for specifying the pre-eruptive plasma properties in the corona. Next, time dependent MHD simulations describe the ejection of two magnetic flux ropes, that produce time dependent boundary conditions for the magnetic field and plasma at 4 R⊙ that in future may be applied to interplanetary space weather prediction models. Conclusions: In the present paper, we show that the dual use of quasi-static non-potential magnetic field simulations and full time dependent MHD simulations can produce realistic inhomogeneous boundary conditions for space weather forecasting tools. Before a fully operational model can be produced there are a

  19. A new DMSP magnetometer and auroral boundary data set and estimates of field-aligned currents in dynamic auroral boundary coordinates

    NASA Astrophysics Data System (ADS)

    Kilcommons, Liam M.; Redmon, Robert J.; Knipp, Delores J.

    2017-08-01

    We have developed a method for reprocessing the multidecadal, multispacecraft Defense Meteorological Satellite Program Special Sensor Magnetometer (DMSP SSM) data set and have applied it to 15 spacecraft years of data (DMSP Flight 16-18, 2010-2014). This Level-2 data set improves on other available SSM data sets with recalculated spacecraft locations and magnetic perturbations, artifact signal removal, representations of the observations in geomagnetic coordinates, and in situ auroral boundaries. Spacecraft locations have been recalculated using ground-tracking information. Magnetic perturbations (measured field minus modeled main field) are recomputed. The updated locations ensure the appropriate model field is used. We characterize and remove a slow-varying signal in the magnetic field measurements. This signal is a combination of ring current and measurement artifacts. A final artifact remains after processing: step discontinuities in the baseline caused by activation/deactivation of spacecraft electronics. Using coincident data from the DMSP precipitating electrons and ions instrument (SSJ4/5), we detect the in situ auroral boundaries with an improvement to the Redmon et al. (2010) algorithm. We embed the location of the aurora and an accompanying figure of merit in the Level-2 SSM data product. Finally, we demonstrate the potential of this new data set by estimating field-aligned current (FAC) density using the Minimum Variance Analysis technique. The FAC estimates are then expressed in dynamic auroral boundary coordinates using the SSJ-derived boundaries, demonstrating a dawn-dusk asymmetry in average FAC location relative to the equatorward edge of the aurora. The new SSM data set is now available in several public repositories.

  20. Static Magnetic Cloak without a Superconductor

    NASA Astrophysics Data System (ADS)

    Jiang, Wei; Ma, Yungui; He, Sailing

    2018-05-01

    Similar to its electromagnetic counterpart, magnetic cloaking also has very important technological applications. However, the traditional method to build a static magnetic cloak requires the use of superconducting materials as the diamagnetic component, which seriously limits the practical potential because of the cryogenic condition. We show that a diamagnetic active current boundary combined with a high-permeability magnetic inner shell (MIS) can be designed to solve this problem, rendering an ideal magnetic cloaking effect at zero frequency. We first theoretically prove that a current boundary could magnetically behave as a superconductor to external observers. Based on this phenomena, we introduce a high-permeability MIS made of magnetically ultrasoft metallic sheets (permeability μ >103 ) and experimentally prove that the bilayer combination can exactly balance out the disturbance to the external probing field and, meanwhile, have a large invisible inner space. We also show that the active boundary currents can be accordingly configured to overcome the permeability and frequency band limits, leading to a robust cloak over the entire quasistatic frequency region. Our work creates an efficient way to circumvent the traditional limits of metamaterials to build magnetic cloaks for ultralow frequencies. The active-passive hybrid approach could be generally extended to yield other artificial magnetic devices or systems as well.

  1. Finite Beta Boundary Magnetic Fields of NCSX

    NASA Astrophysics Data System (ADS)

    Grossman, A.; Kaiser, T.; Mioduszewski, P.

    2004-11-01

    The magnetic field between the plasma surface and wall of the National Compact Stellarator (NCSX), which uses quasi-symmetry to combine the best features of the tokamak and stellarator in a configuration of low aspect ratio is mapped via field line tracing in a range of finite beta in which part of the rotational transform is generated by the bootstrap current. We adopt the methodology developed for W7-X, in which an equilibrium solution is computed by an inverse equilibrium solver based on an energy minimizing variational moments code, VMEC2000[1], which solves directly for the shape of the flux surfaces given the external coils and their currents as well as a bootstrap current provided by a separate transport calculation. The VMEC solution and the Biot-Savart vacuum fields are coupled to the magnetic field solver for finite-beta equilibrium (MFBE2001)[2] code to determine the magnetic field on a 3D grid over a computational domain. It is found that the edge plasma is more stellarator-like, with a complex 3D structure, and less like the ordered 2D symmetric structure of a tokamak. The field lines make a transition from ergodically covering a surface to ergodically covering a volume, as the distance from the last closed magnetic surface is increased. The results are compared with the PIES[3] calculations. [1] S.P. Hirshman et al. Comput. Phys. Commun. 43 (1986) 143. [2] E. Strumberger, et al. Nucl. Fusion 42 (2002) 827. [3] A.H. Reiman and H.S. Greenside, Comput. Phys. Commun. 43, 157 (1986).

  2. Cross-sector Service Provision in Health and Social Care: An Umbrella Review

    PubMed Central

    Magalhaes, Lilian; Anne Kinsella, Elizabeth; Kothari, Anita

    2016-01-01

    Introduction: Meeting the complex health needs of people often requires interaction among numerous different sectors. No one service can adequately respond to the diverse care needs of consumers. Providers working more effectively together is frequently touted as the solution. Cross-sector service provision is defined as independent, yet interconnected sectors working together to better meet the needs of consumers and improve the quality and effectiveness of service provision. Cross-sector service provision is expected, yet much remains unknown about how it is conceptualised or its impact on health status. This umbrella review aims to clarify the critical attributes that shape cross-sector service provision by presenting the current state of the literature and building on the findings of the 2004 review by Sloper. Methods: Literature related to cross-sector service provision is immense, which poses a challenge for decision makers wishing to make evidence-informed decisions. An umbrella review was conducted to articulate the overall state of cross-sector service provision literature and examine the evidence to allow for the discovery of consistencies and discrepancies across the published knowledge base. Findings: Sixteen reviews met the inclusion criteria. Seven themes emerged: Focusing on the consumer, developing a shared vision of care, leadership involvement, service provision across the boundaries, adequately resourcing the arrangement, developing novel arrangements or aligning with existing relationships, and strengthening connections between sectors. Future research from a cross-organisational, rather than individual provider, perspective is needed to better understand what shapes cross-sector service provision at the boundaries. Conclusion: Findings aligned closely with the work done by Sloper and raise red flags related to reinventing what is already known. Future researchers should look to explore novel areas rather than looking into areas that have been

  3. Ferroelectric translational antiphase boundaries in nonpolar materials

    PubMed Central

    Wei, Xian-Kui; Tagantsev, Alexander K.; Kvasov, Alexander; Roleder, Krystian; Jia, Chun-Lin; Setter, Nava

    2014-01-01

    Ferroelectric materials are heavily used in electro-mechanics and electronics. Inside the ferroelectric, domain walls separate regions in which the spontaneous polarization is differently oriented. Properties of ferroelectric domain walls can differ from those of the domains themselves, leading to new exploitable phenomena. Even more exciting is that a non-ferroelectric material may have domain boundaries that are ferroelectric. Many materials possess translational antiphase boundaries. Such boundaries could be interesting entities to carry information if they were ferroelectric. Here we show first that antiphase boundaries in antiferroelectrics may possess ferroelectricity. We then identify these boundaries in the classical antiferroelectric lead zirconate and evidence their polarity by electron microscopy using negative spherical-aberration imaging technique. Ab initio modelling confirms the polar bi-stable nature of the walls. Ferroelectric antiphase boundaries could make high-density non-volatile memory; in comparison with the magnetic domain wall memory, they do not require current for operation and are an order of magnitude thinner. PMID:24398704

  4. Gravity and magnetic survey of the Oaxaca city region: Cenozoic horst-and-graben structure superimposed on the Oaxaca-Juarez terrane boundary, southern Mexico

    NASA Astrophysics Data System (ADS)

    Campos-Enríquez, J. O.; Belmonte-Jiménez, S. I.; Keppie, J. D.; Ortega-Gutiérrez, F.; Arzate, J. A.; Martínez-Silva, J.; Martínez-Serrano, R. G.

    2010-04-01

    A geophysical survey of the Oaxaca Fault along the north-trending Etla and Zaachila valleys area, southern Mexico, shows a series of NNW-SSE Bouguer and magnetic anomalies with steeper gradients towards the east. The Oaxaca Fault represents Tertiary extensional reactivation of the Juarez shear zone that constitutes the boundary between the Oaxaca and Juárez terranes. Cooperative interpretation of six combined gravity and magnetic NE-SW profiles perpendicular to the valleys indicates the presence of a composite depression comprising three N-S sub-basins: the northern Etla and southern Zaachila sub-basins separated by the Atzompa sub-basin. The Etla sub-basin is bounded by the moderately E-dipping, Etla Fault and the more steeply W-dipping Oaxaca Fault, which together constitute a graben that continues southwards into the Atzompa graben. The deeper Zaachila sub-basin, south of Oaxaca city, is a wide V-shaped graben with a horst in the middle. The new geophysical data suggest that the Oaxaca-Juarez terrane boundary is displaced sinistrally ca. 20 km along the E-W Donají Fault, which defines the northern boundary of the Zaachila sub-basin. On the other hand, the Oaxaca Fault may either continue unbroken southwards along the western margin of the horst in the Zaachila sub-basin or be offset along with the terrane boundary. The sinistral movement may have taken place either during the Late Mesozoic-Early Cenozoic, Laramide Orogeny as a lateral ramp in the thrust plane or under Miocene-Pliocene, NE-SW extension. The former suggests that the Donají Fault is a transcurrent fault, whereas the latter implies that it is a transfer fault. The models imply that originally the suture was continuous south of the Donaji Fault and provide a constraint for the accretion of the Oaxaca and Juarez terranes.

  5. New Crustal Boundary Revealed Beneath the Ross Ice Shelf, Antarctica, through ROSETTA-Ice Integrated Aerogeophysics, Geology, and Ocean Research

    NASA Astrophysics Data System (ADS)

    Tinto, K. J.; Siddoway, C. S.; Bell, R. E.; Lockett, A.; Wilner, J.

    2017-12-01

    Now submerged within marine plateaus and rises bordering Antarctica, Australia and Zealandia, the East Gondwana accretionary margin was a belt of terranes and stitched by magmatic arcs, later stretched into continental ribbons separated by narrow elongate rifts. This crustal architecture is known from marine geophysical exploration and ocean drilling of the mid-latitude coastal plateaus and rises. A concealed sector of the former East Gondwana margin that underlies the Ross Ice Shelf (RIS), Antarctica, is the focus of ROSETTA-ICE, a new airborne data acquisition campaign that explores the crustal makeup, tectonic boundaries and seafloor bathymetry beneath RIS. Gravimeters and a magnetometer are deployed by LC130 aircraft surveying along E-W lines spaced at 10 km, and N-S tie lines at 55 km, connect 1970s points (RIGGS) for controls on ocean depth and gravity. The ROSETTA-ICE survey, 2/3 completed thus far, provides magnetic anomalies, Werner depth-to-basement solutions, a new gravity-based bathymetric model at 20-km resolution, and a new crustal density map tied to the 1970s data. Surprisingly, the data reveal that the major lithospheric boundary separating East and West Antarctica lies 300 km east of the Transantarctic Mountains, beneath the floating RIS. The East and West regions have contrasting geophysical characteristics and bathymetry, with relatively dense lithosphere, low amplitude magnetic anomalies, and deep bathymetry on the East Antarctica side, and high amplitude magnetic anomalies, lower overall density and shallower water depths on the West Antarctic side. The Central High, a basement structure cored at DSDP Site 270 and seismically imaged in the Ross Sea, continues beneath RIS as a faulted but coherent crustal ribbon coincident with the tectonic boundary. The continuity of Gondwana margin crustal architecture discovered beneath the West Antarctic Ice Sheet requires a revision of the existing tectonic framework. The sub-RIS narrow rift basins and

  6. Modeling of non-ideal hard permanent magnets with an affine-linear model, illustrated for a bar and a horseshoe magnet

    NASA Astrophysics Data System (ADS)

    Glane, Sebastian; Reich, Felix A.; Müller, Wolfgang H.

    2017-11-01

    This study is dedicated to continuum-scale material modeling of isotropic permanent magnets. An affine-linear extension to the commonly used ideal hard model for permanent magnets is proposed, motivated, and detailed. In order to demonstrate the differences between these models, bar and horseshoe magnets are considered. The structure of the boundary value problem for the magnetic field and related solution techniques are discussed. For the ideal model, closed-form analytical solutions were obtained for both geometries. Magnetic fields of the boundary value problems for both models and differently shaped magnets were computed numerically by using the boundary element method. The results show that the character of the magnetic field is strongly influenced by the model that is used. Furthermore, it can be observed that the shape of an affine-linear magnet influences the near-field significantly. Qualitative comparisons with experiments suggest that both the ideal and the affine-linear models are relevant in practice, depending on the magnetic material employed. Mathematically speaking, the ideal magnetic model is a special case of the affine-linear one. Therefore, in applications where knowledge of the near-field is important, the affine-linear model can yield more accurate results—depending on the magnetic material.

  7. Electron precipitation in the post midnight sector of the auroral zones. [on the Explorer 40 satellite

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Saflekos, N. A.; Ackerson, K. L.

    1975-01-01

    Comprehensive measurements of the angular distributions and energy spectra of electron intensities with electrostatic analyzer arrays on board the low-altitude satellite Injun 5 are reported. These are for the post-midnight sector of the auroral zones during the high-intensity events accompanying magnetic substorms. Precipitation features on closed terrestrial field lines well equatorward of the trapping boundary for energetic electrons with E greater than 45 keV were examined. No evidences of maxima in the differential energy spectra or of strongly field-aligned currents which are indicative of quasi-static electric fields aligned parallel to the geomagnetic field were found. Precipitation of low-energy electron intensities fluctuated on time scales greater than 2 seconds as viewed at the satellite position. This precipitation was characterized by isotropy for all pitch angles outside the atmospheric backscatter cone.

  8. The Mars Crustal Magnetic Field Control of Plasma Boundary Locations and Atmospheric Loss: MHD Prediction and Comparison with MAVEN

    NASA Technical Reports Server (NTRS)

    Fang, Xiaohua; Ma, Yingjuan; Masunaga, Kei; Dong, Chuanfei; Brain, David; Halekas, Jasper; Lillis, Robert; Jakosky, Bruce M.; Connerney, Jack; Grebowsky, Joseph; hide

    2017-01-01

    We present results from a global Mars time-dependent MHD simulation under constant solar wind and solar radiation impact considering inherent magnetic field variations due to continuous planetary rotation. We calculate the 3-D shapes and locations of the bow shock (BS) and the induced magnetospheric boundary (IMB) and then examine their dynamic changes with time. We develop a physics-based, empirical algorithm to effectively summarize the multidimensional crustal field distribution. It is found that by organizing the model results using this new approach, the Mars crustal field shows a clear, significant influence on both the IMB and the BS. Specifically, quantitative relationships have been established between the field distribution and the mean boundary distances and the cross-section areas in the terminator plane for both of the boundaries. The model-predicted relationships are further verified by the observations from the NASA Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. Our analysis shows that the boundaries are collectively affected by the global crustal field distribution, which, however, cannot be simply parameterized by a local parameter like the widely used subsolar longitude. Our calculations show that the variability of the intrinsic crustal field distribution in Mars-centered Solar Orbital itself may account for approx.60% of the variation in total atmospheric loss, when external drivers are static. It is found that the crustal field has not only a shielding effect for atmospheric loss but also an escape-fostering effect by positively affecting the transterminator ion flow cross-section area.

  9. Manipulation of Schwann cell migration across the astrocyte boundary by polysialyltransferase-loaded superparamagnetic nanoparticles under magnetic field

    PubMed Central

    Xia, Bing; Huang, Liangliang; Zhu, Lei; Liu, Zhongyang; Ma, Teng; Zhu, Shu; Huang, Jinghui; Luo, Zhuojing

    2016-01-01

    Schwann cell (SC) transplantation is an attractive strategy for spinal cord injury (SCI). However, the efficacy of SC transplantation has been limited by the poor migratory ability of SCs in the astrocyte-rich central nervous system (CNS) environment and the inability to intermingle with the host astrocyte. In this study, we first magnetofected SCs by polysialyltransferase-functionalized superparamagnetic iron oxide nanoparticles (PST/SPIONs) to induce overexpression of polysialylation of neural cell adhesion molecule (PSA-NCAM) to enhance SC migration ability, before manipulating the direction of SC migration with the assistance of an applied magnetic field (MF). It was found that magnetofection with PST/SPIONs significantly upregulated the expression of PSA-NCAM in SCs, which significantly enhanced the migration ability of SCs, but without preferential direction in the absence of MF. The number and averaged maximum distance of SCs with PST/SPIONs migrating into the astrocyte domain were significantly enhanced by an applied MF. In a 300 μm row along the astrocyte boundary, the number of SCs with PST/SPIONs migrating into the astrocyte domain under an MF was 2.95 and 6.71 times higher than that in the absence of MF and the intact control SCs, respectively. More interestingly, a confrontation assay demonstrated that SCs with PST/SPIONs were in close contact with astrocytes and no longer formed boundaries in the presence of MF. In conclusion, SCs with PST/SPIONs showed enhanced preferential migration along the axis of a magnetic force, which might be beneficial for the formation of Büngner bands in the CNS. These findings raise the possibilities of enhancing the migration of transplanted SCs in astrocyte-rich CNS regions in a specific direction and creating an SC bridge in the CNS environment to guide regenerated axons to their distal destination in the treatment of SCI. PMID:28003748

  10. Phase retrieval in annulus sector domain by non-iterative methods

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Mao, Heng; Zhao, Da-zun

    2008-03-01

    Phase retrieval could be achieved by solving the intensity transport equation (ITE) under the paraxial approximation. For the case of uniform illumination, Neumann boundary condition is involved and it makes the solving process more complicated. The primary mirror is usually designed segmented in the telescope with large aperture, and the shape of a segmented piece is often like an annulus sector. Accordingly, It is necessary to analyze the phase retrieval in the annulus sector domain. Two non-iterative methods are considered for recovering the phase. The matrix method is based on the decomposition of the solution into a series of orthogonalized polynomials, while the frequency filtering method depends on the inverse computation process of ITE. By the simulation, it is found that both methods can eliminate the effect of Neumann boundary condition, save a lot of computation time and recover the distorted phase well. The wavefront error (WFE) RMS can be less than 0.05 wavelength, even when some noise is added.

  11. Boundary layer polarization and voltage in the 14 MLT region

    NASA Astrophysics Data System (ADS)

    Lundin, R.; Yamauchi, M.; Woch, J.; Marklund, G.

    1995-05-01

    Viking midlatitude observations of ions and electrons in the postnoon auroral region show that field-aligned acceleration of electrons and ions with energies up to a few kiloelectron volts takes place. The characteristics of the upgoing ion beams and the local transverse electric field observed by Viking indicate that parallel ion acceleration is primarily due to a quasi-electrostatic field-aligned acceleration process below Viking altitudes, i.e., below 10,000-13,500 km. A good correlation is found between the maximum upgoing ion beam energy and the depth of the local potential well determined by the Viking electric field experiment within dayside 'ion inverted Vs.' The total transverse potential throughout the entire region near the ion inverted Vs. is generally much higher than the field-aligned potential and may reach well above 10 kV. However, the detailed mapping of the transverse potential out to the boundary layer, a fundamental issue which remains controversial, was not attempted here. An important finding in this study is the strong correlation between the maximum up going ion beam energy of dayside ion inverted Vs and the solar wind velocity. This suggests a direct coupling of the solar wind plasma dynamo/voltage generator to the region of field-aligned particle acceleration. The fact that the center of dayside ion inverted Vs coincide with convection reversals/flow stagnation and upward Birkeland currents on what appears to be closed field lines (Woch et al., 1993), suggests that field-aligned potential structures connect to the inner part of an MHD dyanmo in the low-latitude boundary layer. Thus the Viking observations substantiate the idea of a solar wind induced boundary layer polarization where negatively charged perturbations in the postnoon sector persistently develops along the magnetic field lines, establishing accelerating potential drops along the geomagnetic field lines in the 0.5-10 kV range.

  12. Geophysical constraints for terrane boundaries in southern Mongolia

    NASA Astrophysics Data System (ADS)

    Guy, Alexandra; Schulmann, Karel; Munschy, Marc; Miehe, Jean-Marc; Edel, Jean-Bernard; Lexa, Ondrej; Fairhead, Derek

    2014-05-01

    The Central Asian Orogenic Belt (CAOB) is a typical accretionary orogen divided into numerous lithostratigraphic terranes corresponding to magmatic arcs, back arcs, continental basement blocks, accretionary wedges and metamorphic blocks. These terranes should be in theory characterized by contrasting magnetic and gravity signatures thanks to their different petrophysical properties. To test this hypothesis, the stratigraphically defined terranes in southern Mongolia were compared with potential field data to constrain their boundaries and extent. The existence of terranes in southern Mongolia cannot be attested by the uniform geophysical fabrics due to the lack of systematic correspondence between the high/low amplitude and high/low frequency geophysical domains and major terranes. Processed magnetic and gravity grids show that both gravity and magnetic lineaments are E-W trending in the west and correlate with direction of some geological units. In the east, both magnetic and gravity lineaments are disrupted by NE-SW trending heterogeneities resulting in complete blurring of the geophysical pattern. Correlation of magnetic signal with geological map shows that the magnetic highs coincide with late Carboniferous-early Permian volcanic and plutonic belts. The matched-filtering shows good continuity of signal to the depth located along the boundaries of these high magnetic anomalies which may imply presence of deeply rooted tectono-magmatic zones. The axes of high density bodies in the western and central part of the studied CAOB are characterized by periodic alternations of NW-SE trending high frequency and high amplitude gravity anomalies corresponding to late Permian to Triassic cleavage fronts up to 20 km wide. The matched-filtering analysis shows that the largest deformation zones are deeply rooted down to 20 km depth. Such a gravity signal is explained by the verticalization of high density mantle and lower crustal rocks due to localized vertical shearing

  13. Improved detection limits for electrospray ionization on a magnetic sector mass spectrometer by using an array detector.

    PubMed

    Cody, R B; Tamura, J; Finch, J W; Musselman, B D

    1994-03-01

    Array detection was compared with point detection for solutions of hen egg-white lysozyme, equine myoglobin, and ubiquitin analyzed by electrospray ionization with a magnetic sector mass spectrometer. The detection limits for samples analyzed by using the array detector system were at least 10 times lower than could be achieved by using a point detector on the same mass spectrometer. The minimum detectable quantity of protein corresponded to a signal-to-background ratio of approximately 2∶1 for a 500 amol/μL solution of hen egg-white lysozyme. However, the ultimate practical sample concentrations appeared to be in the 10-100 fmol/μL range for the analysis of dilute solutions of relatively pure proteins or simple mixtures.

  14. Spectral asymptotics of Euclidean quantum gravity with diff-invariant boundary conditions

    NASA Astrophysics Data System (ADS)

    Esposito, Giampiero; Fucci, Guglielmo; Kamenshchik, Alexander Yu; Kirsten, Klaus

    2005-03-01

    A general method is known to exist for studying Abelian and non-Abelian gauge theories, as well as Euclidean quantum gravity, at 1-loop level on manifolds with boundary. In the latter case, boundary conditions on metric perturbations h can be chosen to be completely invariant under infinitesimal diffeomorphisms, to preserve the invariance group of the theory and BRST symmetry. In the de Donder gauge, however, the resulting boundary-value problem for the Laplace-type operator acting on h is known to be self-adjoint but not strongly elliptic. The latter is a technical condition ensuring that a unique smooth solution of the boundary-value problem exists, which implies, in turn, that the global heat-kernel asymptotics yielding 1-loop divergences and 1-loop effective action actually exists. The present paper shows that, on the Euclidean 4-ball, only the scalar part of perturbative modes for quantum gravity is affected by the lack of strong ellipticity. Further evidence for lack of strong ellipticity, from an analytic point of view, is therefore obtained. Interestingly, three sectors of the scalar-perturbation problem remain elliptic, while lack of strong ellipticity is 'confined' to the remaining fourth sector. The integral representation of the resulting ζ-function asymptotics on the Euclidean 4-ball is also obtained; this remains regular at the origin by virtue of a spectral identity here obtained for the first time.

  15. MHD Free Convective Boundary Layer Flow of a Nanofluid past a Flat Vertical Plate with Newtonian Heating Boundary Condition

    PubMed Central

    Uddin, Mohammed J.; Khan, Waqar A.; Ismail, Ahmed I.

    2012-01-01

    Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

  16. Ion-Scale Wave Properties and Enhanced Ion Heating Across the Low-Latitude Boundary Layer During Kelvin-Helmholtz Instability

    NASA Astrophysics Data System (ADS)

    Moore, T. W.; Nykyri, K.; Dimmock, A. P.

    2017-11-01

    In the Earth's magnetosphere, the magnetotail plasma sheet ions are much hotter than in the shocked solar wind. On the dawn sector, the cold-component ions are more abundant and hotter by 30-40% when compared to the dusk sector. Recent statistical studies of the flank magnetopause and magnetosheath have shown that the level of temperature asymmetry of the magnetosheath is unable to account for this, so additional physical mechanisms must be at play, either at the magnetopause or plasma sheet that contributes to this asymmetry. In this study, we perform a statistical analysis on the ion-scale wave properties in the three main plasma regimes common to flank magnetopause boundary crossings when the boundary is unstable to Kelvin-Helmholtz instability (KHI): hot and tenuous magnetospheric, cold and dense magnetosheath, and mixed (Hasegawa et al., 2004). These statistics of ion-scale wave properties are compared to observations of fast magnetosonic wave modes that have recently been linked to Kelvin-Helmholtz (KH) vortex centered ion heating (Moore et al., 2016). The statistical analysis shows that during KH events there is enhanced nonadiabatic heating calculated during ion scale wave intervals when compared to non-KH events. This suggests that during KH events there is more free energy for ion-scale wave generation, which in turn can heat ions more effectively when compared to cases when KH waves are absent. This may contribute to the dawn favored temperature asymmetry of the plasma sheet; recent studies suggest KH waves favor the dawn flank during Parker-Spiral interplanetary magnetic field.

  17. Studying the kinetics of magnetization in high Tc superconductors

    NASA Technical Reports Server (NTRS)

    Turchinskaya, Marina

    1993-01-01

    The first microscopic maps of magnetic induction in YBa2Cu3O(7-x) crystals which directly show the dependence of flux flow on twin density and polytwin block and twin boundary orientation are reported. These maps were obtained by means of a recently-improved magneto-optical imaging technique. Pinning was lowest in untwinned regions and increased with increasing twin density. An isotropy in twin boundary pinning, defined as the ratio of the magnetic induction gradient across twin boundaries to that along twin boundaries, was 10 at 17 K; this ratio increased with increasing temperature. In polycrystals, twin boundaries also had a strongly anisotropic effect on flux flow into a grain from a grain boundary.

  18. Studying the kinetics of magnetization in high Tc superconductors

    NASA Technical Reports Server (NTRS)

    1993-01-01

    We report the first microscopic maps of magnetic induction in YBa2Cu3O(7-x) crystals which directly show the dependence of flux flow on twin density, polytwin block, and twin boundary orientation. These maps were obtained by means of a recently-improved magneto-optical imaging technique. Pinning was lowest in untwinned regions and increasing with increasing twin density. Anisotropy in twin boundary pinning, defined as the ratio of the magnetic induction gradient across twin boundaries to that along twin boundaries, was 10 at 17 K; this ratio increased with increasing temperature. In polycrystals, twin boundaries also had a strongly anisotropic effect on flux flow into a grain from a grain boundary.

  19. The effect of antiphase boundaries on the elastic properties of Ni-Mn-Ga austenite and premartensite

    NASA Astrophysics Data System (ADS)

    Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Drahokoupil, Jan; Kopecký, Vít; Kopeček, Jaromír; Landa, Michal; Heczko, Oleg

    2013-10-01

    The evolution of elastic properties with temperature and magnetic field was studied in two differently heat-treated single crystals of the Ni-Mn-Ga magnetic shape memory alloy using resonant ultrasound spectroscopy. Quenching and slow furnace cooling were used to obtain different densities of antiphase boundaries. We found that the crystals exhibited pronounced differences in the c‧ elastic coefficient and related shear damping in high-temperature ferromagnetic phases (austenite and premartensite). The difference can be ascribed to the formation of fine magnetic domain patterns and pinning of the magnetic domain walls on antiphase boundaries in the material with a high density of antiphase boundaries due to quenching. The fine domain pattern arising from mutual interactions between antiphase boundaries and ferromagnetic domain walls effectively reduces the magnetocrystalline anisotropy and amplifies the contribution of magnetostriction to the elastic response of the material. As a result, the anomalous elastic softening prior to martensite transformation is significantly enhanced in the quenched sample. Thus, for any comparison of experimental data and theoretical calculations the microstructural changes induced by specific heat treatment must be taken into account.

  20. The effect of antiphase boundaries on the elastic properties of Ni-Mn-Ga austenite and premartensite.

    PubMed

    Seiner, Hanuš; Sedlák, Petr; Bodnárová, Lucie; Drahokoupil, Jan; Kopecký, Vít; Kopeček, Jaromír; Landa, Michal; Heczko, Oleg

    2013-10-23

    The evolution of elastic properties with temperature and magnetic field was studied in two differently heat-treated single crystals of the Ni-Mn-Ga magnetic shape memory alloy using resonant ultrasound spectroscopy. Quenching and slow furnace cooling were used to obtain different densities of antiphase boundaries. We found that the crystals exhibited pronounced differences in the c' elastic coefficient and related shear damping in high-temperature ferromagnetic phases (austenite and premartensite). The difference can be ascribed to the formation of fine magnetic domain patterns and pinning of the magnetic domain walls on antiphase boundaries in the material with a high density of antiphase boundaries due to quenching. The fine domain pattern arising from mutual interactions between antiphase boundaries and ferromagnetic domain walls effectively reduces the magnetocrystalline anisotropy and amplifies the contribution of magnetostriction to the elastic response of the material. As a result, the anomalous elastic softening prior to martensite transformation is significantly enhanced in the quenched sample. Thus, for any comparison of experimental data and theoretical calculations the microstructural changes induced by specific heat treatment must be taken into account.

  1. Magnetic Reconnection in the Heliospheric Current Sheet: The Implications of the Different Environments Seen by the VoyagerSpacecraft

    NASA Astrophysics Data System (ADS)

    Swisdak, M. M.; Drake, J. F.; Opher, M.

    2014-12-01

    The magnetic field abutting the heliospheric current sheet (HCS) is primarily in the azimuthal direction, either east-to-west or west-to-east. Mis-alignment of the solar rotational and magnetic axesleads to the characteristic ballerina-skirt shape of the HCS and during the solar cycle there can be large excursions in the sheet's latitudinal extent. Voyager 2's observations of energetic electrondropouts are related to its crossing of this boundary. Magnetic reconnection is also thought to occur as the HCS compresses and narrows between the termination shock and the heliopause. Near theequator the two HCS field alignments are present in roughly equal amounts, while near the edges the distribution can be considerably skewed. This will lead to substantial differences in the environmentsof the two Voyager spacecraft since Voyager 1 is north of the equator, but firmly in the sector region, while Voyager 2 is south of the equator and skirting the edges of the sector region. We presentparticle-in-cell simulations demonstrating the consequences of the reconnection of asymmetric amounts of flux. In particular, we will discuss Voyager 2's remaining time in the heliosphere -- including theimplications for the solar wind velocity, energetic particle transport, and the expected structure of Voyager 2's heliopause crossing -- and compare it with the data collected from Voyager 1.

  2. Magnetic anomalies in the Cosmonauts Sea, off East Antarctica

    NASA Astrophysics Data System (ADS)

    Nogi, Y.; Hanyu, T.; Fujii, M.

    2017-12-01

    Identification of magnetic anomaly lineations and fracture zone trends in the Southern Indian Ocean, are vital to understanding the breakup of Gondwana. However, the magnetic spreading anomalies and fracture zones are not clear in the Southern Indian Ocean. Magnetic anomaly lineations in the Cosmonauts Sea, off East Antarctica, are key to elucidation of separation between Sri Lanka/India and Antarctica. No obvious magnetic anomaly lineations are observed from a Japanese/German aerogeophysical survey in the Cosmonauts Sea, and this area is considered to be created by seafloor spreading during the Cretaceous Normal Superchron. Vector magnetic anomaly measurements have been conducted on board the Icebreaker Shirase mainly to understand the process of Gondwana fragmentation in the Indian Ocean. Magnetic boundary strikes are derived from vector magnetic anomalies obtained in the Cosmonauts Sea. NE-SW trending magnetic boundary strikes are mainly observed along the several NW-SE oriented observation lines with magnetic anomaly amplitudes of about 200 nT. These NE-SW trending magnetic boundary strikes possibly indicate M-series magnetic anomalies that can not be detected from the aerogeophysical survey with nearly N-S observation lines. We will discuss the magnetic spreading anomalies and breakup process between Sri Lanka/India and Antarctica in the Cosmonauts Sea.

  3. Antiphase domains and reverse thermoremanent magnetism in ilmenite-hematite minerals

    USGS Publications Warehouse

    Lawson, C.A.; Nord, G.L.; Dowty, Eric; Hargraves, R.B.

    1981-01-01

    Examination of synthetic ilmenite-hematite samples by transmission electron microscopy has for the first time revealed the presence of well-defined antiphase domains and antiphase domain boundaries in this mineral system. Samples quenched from 1300??C have a high density of domain boundaries, whereas samples quenched from 900??C have a much lower density. Only the high-temperature samples acquire reverse thermoremanent magnetism when cooled in an applied magnetic field. The presence of a high density of domain boundaries seems to be a necessary condition for the acquisition of reverse thermoremanent magnetism.

  4. Changes of the boot-shaped coronal hole boundary during Whole Sun Month near sunspot minimum

    NASA Astrophysics Data System (ADS)

    Zhao, X. P.; Hoeksema, J. T.; Scherrer, P. H.

    1999-05-01

    The August 27, 1996, boot-shaped coronal hole is shown to rotate nearly rigidly at a rate of 13.25°/day, greater than the equatorial rotation rate of bipolar magnetic regions such as active regions and plages. The day-to-day variation of the coronal hole border is determined by comparing the rigid rotation projection of the disk-center hole boundary to coronal hole boundaries observed in successive daily coronal images. To determine the influence of the changing photospheric field on the location of the coronal hole boundary, a better approximation of the instantaneous global magnetic field distribution is developed and used as input to a potential-field source-surface model to compute the foot-point areas of open field lines. Day-to-day variations of the coronal hole boundary may be caused by changes of the magnetic field and plasma properties in the corona, as well as by the changing photospheric field.

  5. THE EFFECT OF RECONNECTION ON THE STRUCTURE OF THE SUN’S OPEN–CLOSED FLUX BOUNDARY

    SciTech Connect

    Pontin, D. I.; Wyper, P. F., E-mail: dpontin@maths.dundee.ac.uk, E-mail: peter.f.wyper@nasa.gov

    2015-05-20

    Global magnetic field extrapolations are now revealing the huge complexity of the Sun's corona, and in particular the structure of the boundary between open and closed magnetic flux. Moreover, recent developments indicate that magnetic reconnection in the corona likely occurs in highly fragmented current layers, and that this typically leads to a dramatic increase in the topological complexity beyond that of the equilibrium field. In this paper we use static models to investigate the consequences of reconnection at the open–closed flux boundary (“interchange reconnection”) in a fragmented current layer. We demonstrate that it leads to efficient mixing of magnetic fluxmore » (and therefore plasma) from open and closed field regions. This corresponds to an increase in the length and complexity of the open–closed boundary. Thus, whenever reconnection occurs at a null point or separator of this open–closed boundary, the associated separatrix arc of the so-called S-web in the high corona becomes not a single line but a band of finite thickness within which the open–closed boundary is highly structured. This has significant implications for the acceleration of the slow solar wind, for which the interaction of open and closed field is thought to be important, and may also explain the coronal origins of certain solar energetic particles. The topological structures examined contain magnetic null points, separatrices and separators, and include a model for a pseudo-streamer. The potential for understanding both the large scale morphology and fine structure observed in flare ribbons associated with coronal nulls is also discussed.« less

  6. REDEFINING THE BOUNDARIES OF INTERPLANETARY CORONAL MASS EJECTIONS FROM OBSERVATIONS AT THE ECLIPTIC PLANE

    SciTech Connect

    Cid, C.; Palacios, J.; Saiz, E.

    2016-09-01

    On 2015 January 6–7, an interplanetary coronal mass ejection (ICME) was observed at L1. This event, which can be associated with a weak and slow coronal mass ejection, allows us to discuss the differences between the boundaries of the magnetic cloud and the compositional boundaries. A fast stream from a solar coronal hole surrounding this ICME offers a unique opportunity to check the boundaries’ process definition and to explain differences between them. Using Wind and ACE data, we perform a complementary analysis involving compositional, magnetic, and kinematic observations providing relevant information regarding the evolution of the ICME as travelling awaymore » from the Sun. We propose erosion, at least at the front boundary of the ICME, as the main reason for the difference between the boundaries, and compositional signatures as the most precise diagnostic tool for the boundaries of ICMEs.« less

  7. Model for temperature-dependent magnetization of nanocrystalline materials

    NASA Astrophysics Data System (ADS)

    Bian, Q.; Niewczas, M.

    2015-01-01

    A magnetization model of nanocrystalline materials incorporating intragrain anisotropies, intergrain interactions, and texture effects has been extended to include the thermal fluctuations. The method relies on the stochastic Landau-Lifshitz-Gilbert theory of magnetization dynamics and permits to study the magnetic properties of nanocrystalline materials at arbitrary temperature below the Currie temperature. The model has been used to determine the intergrain exchange constant and grain boundary anisotropy constant of nanocrystalline Ni at 100 K and 298 K. It is found that the thermal fluctuations suppress the strength of the intergrain exchange coupling and also reduce the grain boundary anisotropy. In comparison with its value at 2 K, the interparticle exchange constant decreases by 16% and 42% and the grain boundary anisotropy constant decreases by 28% and 40% at 100 K and 298 K, respectively. An application of the model to study the grain size-dependent magnetization indicates that when the thermal activation energy is comparable to the free energy of grains, the decrease in the grain size leads to the decrease in the magnetic permeability and saturation magnetization. The mechanism by which the grain size influences the magnetic properties of nc-Ni is discussed.

  8. Enhanced magnetization of the Marlboro Clay as a product of impact-induced soil pyrogenesis at the Paleocene-Eocene boundary

    NASA Astrophysics Data System (ADS)

    Kent, D. V.; Lanci, L.; Wang, H.

    2016-12-01

    The Marlboro Clay, a shallow water shelf deposit on the eastern margin of North America whose base corresponds to the onset of the carbon isotope excursion (CIE) at the Paleocene-Eocene boundary, is characterized by an anomalously high concentration of magnetic nanoparticles of enigmatic origin that give rise to a particularly intense bulk magnetization1-3. Recent rock magnetic results (TFT, high-resolution FORC, etc.) show that the magnetic assemblage is dominated by near-equant single-domain magnetic particles that are isolated and not arranged in chains characteristic of bacterial magnetosomes4. However, the 6 m average thickness of the widespread Marlboro, far in excess of known ejecta layers, makes a proposed origin of the nanoparticles as condensates of an impact plume problematical5. New data from a core at Wilson Lake reveals that the saturation remanence of the Marlboro is not only more intense but also more highly anisotropic compared to the immediately underlying Vincentown Formation, even though high field magnetic susceptibilities are not significantly different between the units. We suggest that the magnetization of the Marlboro originates from pyromagnetic soil enhancement by widespread wildfires on the adjoining drainage area (e.g.,6,7). The soils were soon washed down from the denuded landscape and rapidly deposited as mud-waves across the shelf to become the Marlboro. The pyromagnetic nanoparticles evidently nucleated within altered soil clays whose subsequent compaction on the shelf can account for the observed high magnetic anisotropy. A plausible trigger for the widespread wildfires needed to produce the unusual amount of pyrogenetic material in the Marlboro is a fireball from the impact of a modest-sized object at moderate range8, for example, a 10 km diameter carbon-rich comet coming down something like the distance to Bermuda away. The high concentration of magnetic nanoparticles in the Marlboro may thus be only a very indirect result of an

  9. Boundary States and Broken Bulk Symmetries in WAr Minimal Models

    NASA Astrophysics Data System (ADS)

    Caldeira, Alexandre F.; Wheater, J. F.

    We review the free-field formalism for boundary states. The multi-component free-field formalism is then used to study the boundary states of (p',p) rational conformal field theories having a W symmetry of the type Ar. We show how the classification of primary fields for these models is obtained by demanding modular covariance of cylinder amplitudes and that the resulting modular S matrix satisfies all the necessary conditions. Basis states satisfying the boundary conditions are found in the form of coherent states and as expected we find that W violating states can be found for all these models. We construct consistent physical boundary states for all the rank 2 (p + 1,p) models (of which the already known case of the 3-state Potts model is the simplest example) and find that the W violating sector possesses a direct analogue of the Verlinde formula.

  10. Enhanced magnetization of the Marlboro Clay as a product of soil pyrogenesis at the Paleocene-Eocene boundary?

    NASA Astrophysics Data System (ADS)

    Kent, Dennis V.; Lanci, Luca; Wang, Huapei; Wright, James D.

    2017-09-01

    The kaolinite-rich Marlboro Clay was deposited on the inner shelf in the Salisbury Embayment of the U.S. Atlantic margin at the onset of the carbon isotope excursion marking the 56 Ma Paleocene-Eocene boundary and is characterized by an anomalously high concentration of magnetic nanoparticles of enigmatic origin that give rise to notably intense bulk magnetization. Recent studies point to a magnetic assemblage that is dominated by single-domain magnetite particles that tend to be isolated rather than arranged in chains, the most distinguishing feature of magnetotactic bacteria fossils. On the other hand, it is very unlikely that the nanoparticles can be condensates of an impact plume given the meter-scale thickness of the Marlboro Clay. We obtained new data from a landward proximal site at Wilson Lake on the New Jersey Coastal Plain and find that the abrupt increase in magnetite nanoparticles is virtually coincident stratigraphically with the recently reported impact spherule layer at the base of the Marlboro Clay in the same core. Yet the high field magnetic susceptibility, a measure of total iron concentration, and strontium isotope values on bulk sediment, an indicator of sediment weathering provenance, are not different in the Marlboro Clay from the immediately underlying Vincentown Formation. We suggest that the distinctive magnetic properties of the Marlboro Clay originated from pyromagnetic soil enhancement by widespread wildfires on the adjoining drainage area. The pyrogenetic products were soon washed from the denuded landscape and rapidly deposited as mud-waves across the shelf, becoming the Marlboro Clay. A few percent of incinerated biomass ends up as calcite known as wood ash stone and can inherit its light carbon isotope composition. Disseminated wood ash stone entrained in the Marlboro Clay could contribute to the landward increase in amplitude of the carbon isotope excursion in bulk carbonate data. A plausible trigger for the initial conflagration

  11. Forced three-dimensional magnetic reconnection due to linkage of magnetic flux tubes

    NASA Technical Reports Server (NTRS)

    Otto, A.

    1995-01-01

    During periods of southward interplanetary magnetic field (IMF) orientation the magnetic field geometry at the dayside magnetopause is susceptible to magnetic reconnection. It has been suggested that reconnection may occur in a localized manner at several patches on the magnetopause. A major problem with this picture is the interaction of magnetic flux ropes which are generated by different reconnection processes. An individual flux rope is bent elbowlike where it intersects the magnetopause and the magnetic field changes from magnetospheric to interplanetary magnetic field orientation. Multiple patches of reconnection can lead to the formation of interlinked magnetic flux tubes. Although the corresponding flux is connected to the IMF the northward and southward connected branches are hooked into each other and cannot develop independently. We have studied this problem in the framework of three-dimensional magnetohydrodynamic simulations. The results indicate that a singular current sheet forms at the interface of two interlinked flux tubes if no resistivity is present in the simulation. This current sheet is strongly tilted compared to the original current sheet. In the presence of resistivity the interaction of the two flux tubes forces a fast reconnection process which generates helically twisted closed magnetospheric flux. This linkage induced reconnection generates a boundary layer with layers of open and closed magnetospheric flux and may account for the brightening of auroral arcs poleward of the boundary between open and closed magnetic flux.

  12. Blurring the Boundaries of Public and Private Education in Brazil

    ERIC Educational Resources Information Center

    Akkari, Abdeljalil

    2013-01-01

    A typical analysis of the privatization of education in Latin America focuses on private sector development at the expense of public education. In this paper, I propose a different view that will highlight the blurring of boundaries between public and private education in Brazil. This confusion perpetuates the historical duality of the education…

  13. Plasma-tail activity at the time of the Vega encounters

    NASA Technical Reports Server (NTRS)

    Niedner, Malcolm B., Jr.; Schwingensuch, Konrad

    1986-01-01

    Physical associations are sought between Halley's plasma tail activity seen in ground-based imagery and near-comet, solar wind/IMF measurements obtained by the Vega spacecraft. Disconnection Events (DE's) and the sector boundary/frontside magnetic reconnection model (Niedner and Brandt, 1978) of their origin are discussed. Strong support for the model comes from 2 DE's: a major event whose onset, on March 7 to 8, is strongly correlated with a reversal of the comet's magnetic barrier observed by Vega-1 and Vega-2 and with an IMF sector boundary observed by Vega-1; and a minor event on March 7 which may be associated with the two-polarity (possibly reconnecting) magnetic barrier seen by Vega-1 on March 6, when the solar-wind density was low.

  14. Magnetic signature of the Sicily Channel volcanism

    NASA Astrophysics Data System (ADS)

    Lodolo, E.; Civile, D.; Zanolla, C.; Geletti, R.

    2012-03-01

    Widespread Late Miocene to Quaternary volcanic activity is know to have occurred in the Sicily Channel continuing up to historical time. New magnetic anomaly data acquired in the Pantelleria Graben, one of the three main tectonic depressions forming the WNW-trending Sicily Channel rift system, integrated with available profiles, are used to identify and map volcanic bodies in this sector of the northern African margin. Some of these manifestations, both outcropping at the sea-floor or buried beneath a variable thickness of Plio-Quaternary sedimentary cover, have been imaged by seismic reflection profiles. Three main positive magnetic anomalies have been found: to the S-E of the Pantelleria Island, the largest emerged caldera of the Sicily Channel, along the eastern margin of the Nameless Bank, and at the north-western termination of the Linosa Graben. Only the anomaly located off the south-eastern coast of the Pantelleria Island, associated with a large outcropping body gradually buried beneath a substantially undisturbed Upper Pliocene-Quaternary sediments, aligns with the trend of the tectonic depression. 2-D geophysical models produced along seismic transects perpendicularly crossing the Pantelleria Graben have allowed to derive its deep crustal structure, and detect the presence of buried magmatic bodies which generate the anomalies. Marginal faults seem to have played a major role in focussing magma emplacement in this sector of the Sicily Channel. The other anomalies represent off-axis volcanic episodes and generally do not show evident magmatic manifestations at the sea-floor. These magnetic maxima seem to follow a NNE-SSW-trending belt extending from Linosa Island to the Nameless Bank, where pre-existing crustal anisotropies may have conditioned magma emplacement both at deep and shallow crustal levels. In general, data analysis has shown that there is a structural control on magma emplacement, with the major magmatic features located in specific locations

  15. Origin of reduced magnetization and domain formation in small magnetite nanoparticles

    DOE PAGES

    Nedelkoski, Zlatko; Kepaptsoglou, Demie; Lari, Leonardo; ...

    2017-04-10

    We compare the structural, chemical, and magnetic properties of magnetite nanoparticles. Aberration corrected scanning transmission electron microscopy reveals the prevalence of antiphase boundaries in nanoparticles that have significantly reduced magnetization, relative to the bulk. We show that atomistic magnetic modelling of nanoparticles with and without these defects reveal the origin of the reduced moment. Strong antiferromagnetic interactions across antiphase boundaries support multiple magnetic domains even in particles as small as 12–14 nm.

  16. Cusp/cleft auroral activity in relation to solar wind dynamic pressure, interplanetary magnetic field B(sub z) and B(sub y)

    NASA Technical Reports Server (NTRS)

    Sandholt, P. E.; Farrugia, C. J.; Burlaga, L. F.; Holtet, J. A.; Moen, J.; Lybekk, B.; Jacobsen, B.; Opsvik, D.; Egeland, A.; Lepping, R.

    1994-01-01

    Continuous optical observations of cusp/cleft auroral activities within approximately equal to 09-15 MLT and 70-76 deg magnetic latitude are studied in relation to changes in solar wind dynamic pressure and interplanetary magnetic field (IMF) variability. The observed latitudinal movements of the cusp/cleft aurora in response to IMF B(sub z) changes may be explained as an effect of a variable magnetic field intensity in the outer dayside magnetosphere associated with the changing intensity of region 1 field-aligned currents and associated closure currents. Ground magnetic signatures related to such currents were observed in the present case (January 10, 1993). Strong, isolated enhancements in solar wind dynamic pressure (Delta p/p is greater than or equal to 0.5) gave rise to equatorward shifts of the cusp/cleft aurora, characteristic auroral transients, and distinct ground magnetic signatures of enhanced convection at cleft latitudes. A sequence of auroral events of approximately equal to 5-10 min recurrence time, moving eastward along the poleward boundary of the persistent cusp/cleft aurora in the approximately equal to 10-14 MLT sector, during negative IMF B(sub z) and B(sub y) conditions, were found to be correlated with brief pulses in solar wind dynamic pressure (0.1 is less than Delta p/p is less than 0.5). Simultaneous photometer observations from Ny Alesund, Svalbard, and Danmarkshavn, Greenland, show that the events often appeared on the prenoon side (approximately equal to 10-12 MLT), before moving into the postnoon sector in the case we study here, when IMF B(sub y) is less than 0. In other cases, similar auroral event sequences have been observed to move westward in the prenoon sector, during intervals of positive B(sub y). Thus a strong prenoon/postnoon asymmetry of event occurence and motion pattern related to the IMF B(sub y) polarity is observed. We find that this category of auroral event sequence is stimulated bursts of electron precipitation

  17. Crustal structure of the Churchill-Superior boundary zone between 80 and 98 deg W longitude from Magsat anomaly maps and stacked passes

    NASA Technical Reports Server (NTRS)

    Hall, D. H.; Millar, T. W.; Noble, I. A.

    1985-01-01

    A modeling technique using spherical shell elements and equivalent dipole sources has been applied to Magsat signatures at the Churchill-Superior boundary in Manitoba, Ontario, and Ungava. A large satellite magnetic anomaly (12 nT amplitude) on POGO and Magsat maps near the Churchill-Superior boundary was found to be related to the Richmond Gulf aulacogen. The averaged crustal magnetization in the source region is 5.2 A/m. Stacking of the magnetic traces from Magsat passes reveals a magnetic signature (10 nT amplitude) at the Churchill-Superior boundary in an area studied between 80 deg W and 98 deg W. Modeling suggests a steplike thickening of the crust on the Churchill side of the boundary in a layer with a magnetization of 5 A/m. Signatures on aeromagnetic maps are also found in the source areas for both of these satellite anomalies.

  18. Analytical and numerical analyses for a penny-shaped crack embedded in an infinite transversely isotropic multi-ferroic composite medium: semi-permeable electro-magnetic boundary condition

    NASA Astrophysics Data System (ADS)

    Zheng, R.-F.; Wu, T.-H.; Li, X.-Y.; Chen, W.-Q.

    2018-06-01

    The problem of a penny-shaped crack embedded in an infinite space of transversely isotropic multi-ferroic composite medium is investigated. The crack is assumed to be subjected to uniformly distributed mechanical, electric and magnetic loads applied symmetrically on the upper and lower crack surfaces. The semi-permeable (limited-permeable) electro-magnetic boundary condition is adopted. By virtue of the generalized method of potential theory and the general solutions, the boundary integro-differential equations governing the mode I crack problem, which are of nonlinear nature, are established and solved analytically. Exact and complete coupling magneto-electro-elastic field is obtained in terms of elementary functions. Important parameters in fracture mechanics on the crack plane, e.g., the generalized crack surface displacements, the distributions of generalized stresses at the crack tip, the generalized stress intensity factors and the energy release rate, are explicitly presented. To validate the present solutions, a numerical code by virtue of finite element method is established for 3D crack problems in the framework of magneto-electro-elasticity. To evaluate conveniently the effect of the medium inside the crack, several empirical formulae are developed, based on the numerical results.

  19. A statistical study of ionopause perturbation and associated boundary wave formation at Venus.

    NASA Astrophysics Data System (ADS)

    Chong, G. S.; Pope, S. A.; Walker, S. N.; Zhang, T.; Balikhin, M. A.

    2017-12-01

    In contrast to Earth, Venus does not possess an intrinsic magnetic field. Hence the interaction between solar wind and Venus is significantly different when compared to Earth, even though these two planets were once considered similar. Within the induced magnetosphere and ionosphere of Venus, previous studies have shown the existence of ionospheric boundary waves. These structures may play an important role in the atmospheric evolution of Venus. By using Venus Express data, the crossings of the ionopause boundary are determined based on the observations of photoelectrons during 2011. Pulses of dropouts in the electron energy spectrometer were observed in 92 events, which suggests potential perturbations of the boundary. Minimum variance analysis of the 1Hz magnetic field data for the perturbations is conducted and used to confirm the occurrence of the boundary waves. Statistical analysis shows that they were propagating mainly in the ±VSO-Y direction in the polar north terminator region. The generation mechanisms of boundary waves and their evolution into the potential nonlinear regime are discussed and analysed.

  20. Growth anisotropy effect of bulk high temperature superconductors on the levitation performance in the applied magnetic field

    NASA Astrophysics Data System (ADS)

    Zheng, J.; Liao, X. L.; Jing, H. L.; Deng, Z. G.; Yen, F.; Wang, S. Y.; Wang, J. S.

    2013-10-01

    Growth anisotropies of bulk high temperature superconductors (HTSCs) fabricated by a top-seeded melt texture growth process, that is, different pinning effect in the growth sectors (GSs) and growth sector boundaries (GSBs), possess effect on the macro flux trapping and levitation performance of bulk HTSCs. Previous work (Physics Procedia, 36 (2012) 1043) has found that the bulk HTSC array with aligned GSB pattern (AGSBP) exhibits better capability for levitation and suppression of levitation force decay above a permanent magnet guideway (PMG) compared with misaligned GSB pattern (MGSBP). In this paper, we further examine this growth anisotropy effect on the maglev performance of a double-layer bulk HTSC. In contrast to reported trapped flux cases (Supercond. Sci. Technol. 19 (2006) S466), the two superposed bulk HTSCs with same AGSBP with PMG are found to show better maglev performance. These series of results are helpful and support a new way for the performance optimization of present HTS maglev systems.

  1. Using magnetic charge to understand soft-magnetic materials

    NASA Astrophysics Data System (ADS)

    Arrott, Anthony S.; Templeton, Terry L.

    2018-04-01

    This is an overview of what the Landau-Lifshitz-Gilbert equations are doing in soft-magnetic materials with dimensions large compared to the exchange length. The surface magnetic charges try to cancel applied magnetic fields inside the soft magnetic material. The exchange energy tries to reach a minimum while meeting the boundary conditions set by the magnetic charges by using magnetization patterns that have a curl but no divergence. It can almost do this, but it still pays to add some divergence to further lower the exchange energy. There are then both positively and negatively charged regions in the bulk. The unlike charges attract one another, but do not annihilate because they are paid for by the reduction in exchange energy. The micromagnetics of soft magnetic materials is about how those charges rearrange themselves. The topology of magnetic charge distributions presents challenges for mathematicians. No one guessed that they like to form helical patterns of extended multiples of charge density.

  2. Pulse propagation, dispersion, and energy in magnetic materials.

    PubMed

    Scalora, Michael; D'Aguanno, Giuseppe; Mattiucci, Nadia; Akozbek, Neset; Bloemer, Mark J; Centini, Marco; Sibilia, Concita; Bertolotti, Mario

    2005-12-01

    We discuss pulse propagation effects in generic, electrically and magnetically dispersive media that may display large material discontinuities, such as a surface boundary. Using the known basic constitutive relations between the fields, and an explicit Taylor expansion to describe the dielectric susceptibility and magnetic permeability, we derive expressions for energy density and energy dissipation rates, and equations of motion for the coupled electric and magnetic fields. We then solve the equations of motion in the presence of a single interface, and find that in addition to the now-established negative refraction process an energy exchange occurs between the electric and magnetic fields as the pulse traverses the boundary.

  3. Characterization of the in situ magnetic architecture of oceanic crust (Hess Deep) using near-source vector magnetic data

    NASA Astrophysics Data System (ADS)

    Tominaga, Masako; Tivey, Maurice A.; MacLeod, Christopher J.; Morris, Antony; Lissenberg, C. Johan; Shillington, Donna J.; Ferrini, Vicki

    2016-06-01

    Marine magnetic anomalies are a powerful tool for detecting geomagnetic polarity reversals, lithological boundaries, topographic contrasts, and alteration fronts in the oceanic lithosphere. Our aim here is to detect lithological contacts in fast-spreading lower crust and shallow mantle by characterizing magnetic anomalies and investigating their origins. We conducted a high-resolution, near-bottom, vector magnetic survey of crust exposed in the Hess Deep "tectonic window" using the remotely operated vehicle (ROV) Isis during RRS James Cook cruise JC21 in 2008. Hess Deep is located at the western tip of the propagating rift of the Cocos-Nazca plate boundary near the East Pacific Rise (EPR) (2°15'N, 101°30'W). ROV Isis collected high-resolution bathymetry and near-bottom magnetic data as well as seafloor samples to determine the in situ lithostratigraphy and internal structure of a section of EPR lower crust and mantle exposed on the steep (~20°dipping) south facing slope just north of the Hess Deep nadir. Ten magnetic profiles were collected up the slope using a three-axis fluxgate magnetometer mounted on ROV Isis. We develop and extend the vertical magnetic profile (VMP) approach of Tivey (1996) by incorporating, for the first time, a three-dimensional vector analysis, leading to what we here termed as "vector vertical magnetic profiling" approach. We calculate the source magnetization distribution, the deviation from two dimensionality, and the strike of magnetic boundaries using both the total field Fourier-transform inversion approach and a modified differential vector magnetic analysis. Overall, coherent, long-wavelength total field anomalies are present with a strong magnetization contrast between the upper and lower parts of the slope. The total field anomalies indicate a coherently magnetized source at depth. The upper part of the slope is weakly magnetized and magnetic structure follows the underlying slope morphology, including a "bench" and lobe

  4. Calculation and Analysis of magnetic gradient tensor components of global magnetic models

    NASA Astrophysics Data System (ADS)

    Schiffler, Markus; Queitsch, Matthias; Schneider, Michael; Stolz, Ronny; Krech, Wolfram; Meyer, Hans-Georg; Kukowski, Nina

    2014-05-01

    Magnetic mapping missions like SWARM and its predecessors, e.g. the CHAMP and MAGSAT programs, offer high resolution Earth's magnetic field data. These datasets are usually combined with magnetic observatory and survey data, and subject to harmonic analysis. The derived spherical harmonic coefficients enable magnetic field modelling using a potential series expansion. Recently, new instruments like the JeSSY STAR Full Tensor Magnetic Gradiometry system equipped with very high sensitive sensors can directly measure the magnetic field gradient tensor components. The full understanding of the quality of the measured data requires the extension of magnetic field models to gradient tensor components. In this study, we focus on the extension of the derivation of the magnetic field out of the potential series magnetic field gradient tensor components and apply the new theoretical framework to the International Geomagnetic Reference Field (IGRF) and the High Definition Magnetic Model (HDGM). The gradient tensor component maps for entire Earth's surface produced for the IGRF show low values and smooth variations reflecting the core and mantle contributions whereas those for the HDGM gives a novel tool to unravel crustal structure and deep-situated ore bodies. For example, the Thor Suture and the Sorgenfrei-Thornquist Zone in Europe are delineated by a strong northward gradient. Derived from Eigenvalue decomposition of the magnetic gradient tensor, the scaled magnetic moment, normalized source strength (NSS) and the bearing of the lithospheric sources are presented. The NSS serves as a tool for estimating the lithosphere-asthenosphere boundary as well as the depth of plutons and ore bodies. Furthermore changes in magnetization direction parallel to the mid-ocean ridges can be obtained from the scaled magnetic moment and the normalized source strength discriminates the boundaries between the anomalies of major continental provinces like southern Africa or the Eastern European

  5. Design and Fabrication of a Magnetic System to Investigate Magnetized Dusty Plasmas

    NASA Astrophysics Data System (ADS)

    Bates, Evan M.; Romero-Talamas, Carlos A.

    2013-10-01

    The interest in researching the dynamics and equilibrium of magnetized dusty plasma crystallization has led to the design and fabrication of a novel experimental setup at UMBC. The proposed magnets will be an important subsystem of this setup, and will produce a uniform magnetic field of several tesla for a duration of several seconds. The magnets will be arranged in the Helmholtz configuration and will have a cooling system for temperature compensation of the coils, as well as the ability to adjust the orientation of the magnetic field with respect to gravity. Planned experiments include propagation of magnetized waves in dusty plasma crystals under various boundary conditions.

  6. Magnetically inferred basement structure in central Saudi Arabia

    USGS Publications Warehouse

    Johnson, P.R.; Stewart, I.C.F.

    1995-01-01

    A compilation of magnetic data acquired during the past three decades for a region in central Saudi Arabia where Precambrian basement is partly exposed on the Arabian shield and partly concealed by overlying Phanerozoic strata, shows a central sector of conspicuous N-S-trending anomalies, a heterogeneous western sector of short-wavelength, high-intensity anomalies, and an eastern sector of low- to moderate-intensity broad-wavelength anomalies. Anomalies in the western and central sectors correlate with Neoproterozoic metavolcanic, metasedimentary, and intrusive rocks of the Arabian shield and are interpreted as delineating extensions of shield-type rocks down-dip beneath Phanerozoic cover. These rocks constitute terranes making up part of a Neoproterozoic orogenic belt that underlies Northeast Africa and western Arabia and it is proposed that their magnetically indicated easternmost extent marks the concealed eastern edge of the orogenic belt in central Arabia. The flat magnetic signature of the eastern sector, not entirely accounted for as an effect of deep burial, may reflect the presence of a crustal block different in character to the terranes of the orogenic belt and, speculatively, may outline a continental block that, according to some tectonic models of the region, collided with the Neoproterozoic terranes and thereby caused their deformation and tectonic accretion.

  7. 33 CFR 3.05-15 - Sector Northern New England Marine Inspection Zone and Captain of the Port Zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Captain of the Port Zone start at the boundary of the Massachusetts-New Hampshire coast at latitude 42°52... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Sector Northern New England... INSPECTION ZONES, AND CAPTAIN OF THE PORT ZONES First Coast Guard District § 3.05-15 Sector Northern New...

  8. 33 CFR 3.05-15 - Sector Northern New England Marine Inspection Zone and Captain of the Port Zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Captain of the Port Zone start at the boundary of the Massachusetts-New Hampshire coast at latitude 42°52... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Sector Northern New England... INSPECTION ZONES, AND CAPTAIN OF THE PORT ZONES First Coast Guard District § 3.05-15 Sector Northern New...

  9. 33 CFR 3.05-15 - Sector Northern New England Marine Inspection Zone and Captain of the Port Zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Captain of the Port Zone start at the boundary of the Massachusetts-New Hampshire coast at latitude 42°52... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Sector Northern New England... INSPECTION ZONES, AND CAPTAIN OF THE PORT ZONES First Coast Guard District § 3.05-15 Sector Northern New...

  10. Fine-scale characteristics of interplanetary sector

    NASA Technical Reports Server (NTRS)

    Behannon, K. W.; Neubauer, F. M.; Barnstoff, H.

    1980-01-01

    The structure of the interplanetary sector boundaries observed by Helios 1 within sector transition regions was studied. Such regions consist of intermediate (nonspiral) average field orientations in some cases, as well as a number of large angle directional discontinuities (DD's) on the fine scale (time scales 1 hour). Such DD's are found to be more similar to tangential than rotational discontinuities, to be oriented on average more nearly perpendicular than parallel to the ecliptic plane to be accompanied usually by a large dip ( 80%) in B and, with a most probable thickness of 3 x 10 to the 4th power km, significantly thicker previously studied. It is hypothesized that the observed structures represent multiple traversals of the global heliospheric current sheet due to local fluctuations in the position of the sheet. There is evidence that such fluctuations are sometimes produced by wavelike motions or surface corrugations of scale length 0.05 - 0.1 AU superimposed on the large scale structure.

  11. Low-latitude boundary layer near noon: An open field line model

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.; Schulz, M.; Pridmore-Brown, D. C.; Roeder, J. L.

    1994-01-01

    We propose that many features of the cusp and low-latitude boundary layer (LLBL) observed near noon MLT can be explained by interpreting the LLBL as being on open lines with an inner boundary at the separatrix between open and closed magnetic field lines. This interpretation places the poleward boundary of the LLBL and equatorward boundary of the cusp along the field line that bifurcates at the cusp neutral point. The interpretation accounts for the abrupt boundary of magnetosheath particles at the inner edge of the LLBL, a feature that is inconsistent with LLBL formation by diffusion onto closed field lines, and for the distribution of magnetosheath particles appearing more as one continuous region than as two distinct regions across the noon cusp/LLBL boundary. Furthermore, we can explain the existence of energetic radiation belt electrons and protons with differing pitch angle distributions within the LLBL and their abrupt cutoff at the poleward boundary of the LLBL. By modeling the LLBL and cusp region quantitatively, we can account for a hemispherical difference in the location of the equatorial boundary of the cusp that is observed to be dependent on the dipole tilt angle but not on the interplanetary magnetic field (IMF) x component. We also find important variations and hemispherical differences in that the size of the LLBL that should depend strongly upon the x component of the IMF. This prediction is observationally testable. Finally, we find that when the IMF is strongly northward, the LLBL may include a narrow region adjacent to the magnetopause where field lines are detached (i.e., have both ends connected to the IMF).

  12. Evolution of solar magnetic fields - A new approach to MHD initial-boundary value problems by the method of nearcharacteristics

    NASA Technical Reports Server (NTRS)

    Nakagawa, Y.

    1980-01-01

    A method of analysis for the MHD initial-boundary problem is presented in which the model's formulation is based on the method of nearcharacteristics developed by Werner (1968) and modified by Shin and Kot (1978). With this method, the physical causality relationship can be traced from the perturbation to the response as in the method of characteristics, while achieving the advantage of a considerable reduction in mathematical procedures. The method offers the advantage of examining not only the evolution of nonforce free fields, but also the changes of physical conditions in the atmosphere accompanying the evolution of magnetic fields. The physical validity of the method is demonstrated with examples, and their significance in interpreting observations is discussed.

  13. Open Heisenberg chain under boundary fields: A magnonic logic gate

    NASA Astrophysics Data System (ADS)

    Landi, Gabriel T.; Karevski, Dragi

    2015-05-01

    We study the spin transport in the quantum Heisenberg spin chain subject to boundary magnetic fields and driven out of equilibrium by Lindblad dissipators. An exact solution is given in terms of matrix product states, which allows us to calculate exactly the spin current for any chain size. It is found that the system undergoes a discontinuous spin-valve-like quantum phase transition from ballistic to subdiffusive spin current, depending on the value of the boundary fields. Thus, the chain behaves as an extremely sensitive magnonic logic gate operating with the boundary fields as the base element.

  14. Energy saver A-sector power test results

    SciTech Connect

    Martin, P.; Flora, R.; Tool, G.

    1982-09-15

    The superconducting magnets and associated cryogenic components in A-sector represent the initial phase of installation of the Fermilab superconducting accelerator, designed to accelerate proton beams to energies of 1 TeV. Installation of the magnets, comprising one-eighth of the ring, was completed in December, 1981. Cooldown and power tests took place in the first half of 1982, concurrent with main ring use for 400 GeV high energy physics. The tests described in this paper involved 151 cryogenic components in the tunnel: 94 dipoles, 24 quadrupoles, 25 spool pieces, 3 feed cans, 4 turn-around boxes and 1 bypass. Refrigeration was supplied bymore » three satellite refrigerators, the Central Helium Liquefier, and two compressor buildings. The magnets were powered by a single power supply.« less

  15. Further analyses of laminar flow heat transfer in circular sector ducts

    SciTech Connect

    Lei, Q.M.; Trupp, A.C.

    1989-11-01

    Heat transfer in circular sector ducts is often encountered in multipassage tubes. Certain flow characteristics of circular sector ducts for apex angles up to {pi} have been determined as documented by Shah and London (1978). Recently, Lei and Trupp (1989) have more completely analyzed the flow characteristics of fully developed laminar flow for apex angles up to 2{pi}, including the location of the maximum velocity. Heat transfer results of fully developed laminar flow in circular sector ducts are also available for certain boundary conditions. Trupp and Lau (1984) numerically determined the average Nusselt number (Nu{sub T}) for isothermal walls. Eckertmore » et al. (1958) initially derived an analytical expression for the temperature profile for the case of H1. Sparrow and Haji-angles up to {pi}. However, the above work required numerical integration (or equivalent) to obtain a value for Nu{sub H1}. Regarding the H1{sub ad} boundary condition, Date (1974) numerically obtained a limiting value of Nu{sub H1}{sub ad} for the semicircular duct from the prediction of circular tubes containing a twisted tape (straight and nonconducting tape). Hong and Bergles (1976) also reported an asymptotic value of Nu{sub H1}{sub ad} for the semicircular duct from their entrance region solution. Otherwise it appears that there are no published analytical results of Nu{sub H1}{sub ad} for circular sector ducts. The purpose of this technical note is to communicate these results. In addition, a novel series expression for Nu{sub H1} is presented together with results for apex angles up to 2{pi}.« less

  16. Evolution of magnetic field and atmospheric response. I - Three-dimensional formulation by the method of projected characteristics. II - Formulation of proper boundary equations. [stellar magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Nakagawa, Y.

    1981-01-01

    The method described as the method of nearcharacteristics by Nakagawa (1980) is renamed the method of projected characteristics. Making full use of properties of the projected characteristics, a new and simpler formulation is developed. As a result, the formulation for the examination of the general three-dimensional problems is presented. It is noted that since in practice numerical solutions must be obtained, the final formulation is given in the form of difference equations. The possibility of including effects of viscous and ohmic dissipations in the formulation is considered, and the physical interpretation is discussed. A systematic manner is then presented for deriving physically self-consistent, time-dependent boundary equations for MHD initial boundary problems. It is demonstrated that the full use of the compatibility equations (differential equations relating variations at two spatial locations and times) is required in determining the time-dependent boundary conditions. In order to provide a clear physical picture as an example, the evolution of axisymmetric global magnetic field by photospheric differential rotation is considered.

  17. Structures and transitions in tungsten grain boundaries

    SciTech Connect

    Frolov, T.; Zhu, Q.; Marian, J.

    2017-02-07

    The objective of this study is to develop a computational methodology to predict structure, energies of tungsten grain boundaries as a function of misorientation and inclination. The energies and the mobilities are the necessary input for thermomechanical model of recrystallization of tungsten for magnetic fusion applications being developed by the Marian Group at UCLA.

  18. Magnetization reversal mechanisms in hybrid resin-bonded Nd Fe B magnets

    NASA Astrophysics Data System (ADS)

    Plusa, D.; Dospial, M.; Slusarek, B.; Kotlarczyk, U.

    2006-11-01

    The magnetic properties of isotropic epoxy resin-bonded magnets prepared by mixing a hard magnetic powder made from melt quenched Nd-Fe-Co-B ribbons and a soft magnetic iron powder have been examined. The magnetization reversal processes and the magnetic parameters have been studied by the measurement of the virgin magnetization curves, the major and minor hysteresis loops and sets of recoil curves. From these recoil curves the field dependence of the reversible and irreversible magnetization components during the magnetization and demagnetization processes has been derived. The remanence relationship was used to study the nature of magnetic interaction between the grains. A study of interaction domains was conducted using optical microscopy. Groups of domains, each over several grains, were observed. It was found that the reversal process in the samples investigated involves the rotation of magnetization vectors in the iron powder grains and pinning of domain walls at the MQP-B grain boundaries.

  19. The PhotoElectron Boundary as observed by MAVEN instruments

    NASA Astrophysics Data System (ADS)

    Garnier, P.; Steckiewicz, M.; Mazelle, C. X.; Xu, S.; Mitchell, D. L.; Holmberg, M.; Halekas, J. S.; Andersson, L.; Brain, D.; Connerney, J. E. P.; Espley, J. R.; Lillis, R. J.; Luhmann, J. G.; Savaud, J. A.; Jakosky, B. M.

    2017-12-01

    Photoelectron peaks in the 20-30 eV energy range are commonly observed in planetary atmospheres (Earth, Mars, Titan...), produced by the intense photoionization from solar 30.4 nm photons. At Mars, these photoelectrons result from the ionization of CO2 and O atmospheric neutrals, and are known to escape the planet down its tail, making them tracers for the atmospheric escape (Frahm et al., 2006). Furthermore, their presence or absence allows us to define the so-called PhotoElectron Boundary (PEB), that separates the sunlit photoelectron-dominated ionosphere from the solar wind controlled environment, as initially observed by the Mars Global Surveyor (MGS) MAG/ER instrument (Mitchell et al. (2000, 2001). We provide here a detailed statistical analysis of the location and properties of the PEB based on the Mars Atmosphere and Volatile Evolution (MAVEN) mission electron and magnetic field data. Our dataset includes 1696 dayside PEB crossings obtained from September 2014 until May 2016 (the observations of escaping photoelectrons in the wake being not included). The PEB appears as mostly sensitive to the solar wind dynamic and crustal magnetic fields pressures, for which a quantitative dependance is derived and compared with two other important boundaries : the bow shock and magnetic pileup boundary. The PEB altitude is highly variable, leading to a variable wake cross section for escape (up to +- 50%), which is important for deriving global escape rates from in situ photoelectron escape rates. The PEB is not always sharp, and is, despite a strong variability, characterized on average by : a magnetic field topology typical for the edge of the Magnetic Pile Up Region above it, more field aligned fluxes above than below, and a clear change of the altitude dependence of both electron fluxes and total density (that appears different from the ionopause). The PEB thus appears as a transition region between two plasma and field configurations which is determined by the

  20. Probing storm-time near-Earth magnetotail dynamics using 30 keV proton isotropic boundaries as tracers of precipitating and trapped populations

    NASA Astrophysics Data System (ADS)

    Ganushkina, N. Y.; Dubyagin, S.; Liemohn, M. W.

    2017-12-01

    The isotropic boundaries of the energetic protons, which can be routinely observed by low-altitude satellites, have been used as a tool to probe remotely the nightside magnetic configuration in the near-Earth region. The validity of this method is based on the assumption that the isotropic boundary is formed by the particle scattering on the curved field lines in the magnetotail current sheet. However recent results revealed that the wave-particle interaction process often can be responsible for the isotropic boundary formation especially during active times. Using numerous observations of the 30 keV proton isotropic boundaries and conjugated measurements of the magnetic field in the equatorial magnetosphere we demonstrate that isotropic boundary location can be used as a proxy of the magnetotail stretching even during magnetic storms. The results imply that the scattering on the curved field lines still plays major role as a mechanism of the isotropic boundary formation during storm-time. We found that the wave-particle interaction could lead to isotropic boundary formation in 15% of events. In addition, we discuss the morphology of the storm-time energetic proton precipitations.

  1. Is There a Magnet School Effect? Using Meta-Analysis to Explore Variation in Magnet School Success. CRESST Report 843

    ERIC Educational Resources Information Center

    Wang, Jia; Schweig, Jonathan D.; Herman, Joan L.

    2014-01-01

    Magnet schools are one of the largest sectors of choice schools in the United States. In this study, we explored whether there is heterogeneity in magnet school effects on student achievement by examining the effectiveness of 24 recently funded magnet schools in 5 school districts across 4 states. We used a two-step analysis: First, separate…

  2. High Latitude Energetic Particle Boundaries: The SAMPEX Database

    NASA Astrophysics Data System (ADS)

    Kanekal, S. G.; Baker, D. N.

    2006-11-01

    The size of the polar cap or the open field line region depends, upon the difference in reconnection rates at the dayside between the IMF and the geomagnetic field, and those occurring in the magnetotail. The dayside merging adds flux to the open field region increasing the polar cap size and the magnetic flux in the lobes of the tail, thereby causing energy to be stored in the magnetosphere. Night side reconnection, geomagnetic storms and substorms dissipate this energy removing flux and shrink the polar cap. The dynamics of the polar cap can therefore be useful in the study of the energy dynamics of the magnetosphere. Energetic particles delineate magnetospheric regions, since their motions are governed by the geomagnetic field. Convection and corotation electric fields control the drift of low energy particles whereas magnetic field gradient and curvature are the dominant factors for higher energy (> ~30 keV) particles. High latitude energetic particle boundaries are related to the polar cap and therefore useful in determining the size of the open field line regions We will provide a long database of energetic particle boundaries in the polar regions using instruments aboard SAMPEX, the first of the Small explorer (SMEX) spacecraft. It was launched on July 3, 1992 into a low earth polar orbit. There are four particle detectors, HILT, LICA, PET and MAST on board which point toward the zenith over the poles of the Earth. These detectors measure electrons, protons and ions ranging in energy from tens of keV to a few MeV. This database will comprise the latitudinal (geographic, magnetic and invariant) and longitudinal (geographic and magnetic local time) positions of energetic particle boundaries in the polar regions. The database will cover a time period from launch to about mid 2004. It will therefore cover a significant portion of the solar cycles 22 and 23. Together with interplanetary data obtainable from public databases, such as the NASA OMNI database the

  3. Recent Plasma Observations Related to Magnetic Merging and the Low-Latitude Boundary Layer. Case Study by Polar, March 18, 2006

    NASA Technical Reports Server (NTRS)

    Chandler, M.; Avanov, L.; Craven, P.; Mozer, F.; Moore, T. E.

    2007-01-01

    We have begun an investigation of the nature of the low-latitude boundary layer in the mid-altitude cusp region using data from the Polar spacecraft. Magnetosheath-like plasma is frequently observed deep (in terms of distance from the magnetopause and in invariant latitude) in the magnetosphere. One such case, taken during a long period of northward interplanetary magnetic field (IMP) on March 18, 2006, shows injected magnetosheath ions within the magnetosphere with velocity distributions resulting from two separate merging sites along the same field lines. Cold ionospheric ions were also observed counterstreaming along the field lines, evidence that these field lines were closed. Our results support the idea of double reconnection under northward IMP on the same group of field lines can provide a source for the LLBL. However, the flow direction of the accelerated magnetosheath ions antiparallel to the local magnetic field and given location of the spacecraft suggest that these two injection sites are located northward of the spacecraft position. Observed convection velocities of the magnetic field lines are inconsistent with those expected for double post-cusp reconnection in both hemispheres. These observations favor a scenario in which a group of newly closed field lines was created by a combination of high shear merging at high latitudes in the northern hemisphere and low shear merging at lower latitudes at the dayside magnetopause.

  4. Image Guided Focal Therapy for Magnetic Resonance Imaging Visible Prostate Cancer: Defining a 3-Dimensional Treatment Margin Based on Magnetic Resonance Imaging Histology Co-Registration Analysis.

    PubMed

    Le Nobin, Julien; Rosenkrantz, Andrew B; Villers, Arnauld; Orczyk, Clément; Deng, Fang-Ming; Melamed, Jonathan; Mikheev, Artem; Rusinek, Henry; Taneja, Samir S

    2015-08-01

    We compared prostate tumor boundaries on magnetic resonance imaging and radical prostatectomy histological assessment using detailed software assisted co-registration to define an optimal treatment margin for achieving complete tumor destruction during image guided focal ablation. Included in study were 33 patients who underwent 3 Tesla magnetic resonance imaging before radical prostatectomy. A radiologist traced lesion borders on magnetic resonance imaging and assigned a suspicion score of 2 to 5. Three-dimensional reconstructions were created from high resolution digitalized slides of radical prostatectomy specimens and co-registered to imaging using advanced software. Tumors were compared between histology and imaging by the Hausdorff distance and stratified by the magnetic resonance imaging suspicion score, Gleason score and lesion diameter. Cylindrical volume estimates of treatment effects were used to define the optimal treatment margin. Three-dimensional software based registration with magnetic resonance imaging was done in 46 histologically confirmed cancers. Imaging underestimated tumor size with a maximal discrepancy between imaging and histological boundaries for a given tumor of an average ± SD of 1.99 ± 3.1 mm, representing 18.5% of the diameter on imaging. Boundary underestimation was larger for lesions with an imaging suspicion score 4 or greater (mean 3.49 ± 2.1 mm, p <0.001) and a Gleason score of 7 or greater (mean 2.48 ± 2.8 mm, p = 0.035). A simulated cylindrical treatment volume based on the imaging boundary missed an average 14.8% of tumor volume compared to that based on the histological boundary. A simulated treatment volume based on a 9 mm treatment margin achieved complete histological tumor destruction in 100% of patients. Magnetic resonance imaging underestimates histologically determined tumor boundaries, especially for lesions with a high imaging suspicion score and a high Gleason score. A 9 mm treatment margin around a lesion

  5. Anomalous plasma diffusion and the magnetopause boundary layer

    NASA Technical Reports Server (NTRS)

    Treumann, Rudolf A.; Labelle, James; Haerendel, Gerhard; Pottelette, Raymond

    1992-01-01

    An overview of the current state of anomalous diffusion research at the magnetopause and its role in the formation of the magnetopause boundary layer is presented. Plasma wave measurements in the boundary layer indicate that most of the relevant unstable wave modes contribute negligibly to the diffusion process at the magnetopause under magnetically undisturbed northward IMF conditions. The most promising instability is the lower hybrid drift instability, which may yield diffusion coefficients of the right order if the highest measured wave intensities are assumed. It is concluded that global stationary diffusion due to wave-particle interactions does not take place at the magnetopause. Microscopic wave-particle interaction and anomalous diffusion may contribute to locally break the MD frozen-in conditions and help in transporting large amounts of magnetosheath plasma across the magnetospheric boundary.

  6. Magnetic domain pattern in hierarchically twinned epitaxial Ni-Mn-Ga films.

    PubMed

    Diestel, Anett; Neu, Volker; Backen, Anja; Schultz, Ludwig; Fähler, Sebastian

    2013-07-03

    Magnetic shape memory alloys exhibit a hierarchically twinned microstructure, which has been examined thoroughly in epitaxial Ni-Mn-Ga films. Here we analyze the consequences of this 'twin within twins' microstructure on the magnetic domain pattern. Atomic and magnetic force microscopy are used to probe the correlation between the martensitic microstructure and magnetic domains. We examine the consequences of different twin boundary orientations with respect to the substrate normal as well as variant boundaries between differently aligned twinned laminates. A detailed micromagnetic analysis is given which describes the influence of the finite film thickness on the formation of magnetic band domains in these multiferroic materials.

  7. Electron distributions in the plasma sheet boundary layer - Time-of-flight effects

    NASA Technical Reports Server (NTRS)

    Onsager, T. G.; Thomsen, M. F.; Gosling, J. T.; Bame, S. J.

    1990-01-01

    The electron edge of the plasma sheet boundary layer lies lobeward of the ion edge. Measurements obtained near the electron edge of the boundary layer reveal low-speed cutoffs for earthward and tailward-flowing electrons. These cutoffs progress to lower speeds with deeper penetration into the boundary layer, and are consistently lower for the earthward-directed electrons than for the tailward-direction electrons. The cutoffs and their variation with distance from the edge of the boundary layer can be consistently interpreted in terms of a time-of-flight effect on recently reconnected magnetic field lines. The observed cutoff speeds are used to estimate the downtail location of the reconnection site.

  8. Ergonomics and design in the Brazilian agricultural sector: a proposal to build matrix of contradictions.

    PubMed

    Tosetto, Thaís; Camarotto, João Alberto

    2012-01-01

    The paper presents a correlation between the parameters of classical TRIZ and variables of analysis of the EWA to construct a matrix of contradictions in ergonomics, with the objective of assisting the designing processes in the Brazilian agricultural sector. Given the representativeness of the sector in the economy, the boundary conditions in which the activities are developed and their impact on the health of workers, this proposal should contribute to the development of adaptable solutions and the promotion of Decent Work.

  9. Specific feature of magnetooptical images of stray fields of magnets of various geometrical shapes

    NASA Astrophysics Data System (ADS)

    Ivanov, V. E.; Koveshnikov, A. V.; Andreev, S. V.

    2017-08-01

    Specific features of magnetooptical images (MOIs) of stray fields near the faces of prismatic hard magnetic elements have been studied. Attention has primarily been focused on MOIs of fields near faces oriented perpendicular to the magnetic moment of hard magnetic elements. With regard to the polar sensitivity, MOIs have practically uniform brightness and geometrically they coincide with the figures of the bases of the elements. With regard to longitudinal sensitivity, MOIs consist of several sectors, the number of which is determined by the number of angles of the image. Each angle is divided by the bisectrix into two sectors of different brightnesses; therefore, the MOI of a triangular magnet consists of three sectors. A rectangle consists of four sectors separated by the bisectrices of the interior angles. In all types of figures, these lines converge at the center of the figure and form a singular point of the source or sink type.

  10. Hidden magnetism and quantum criticality in the heavy fermion superconductor CeRhIn5.

    PubMed

    Park, Tuson; Ronning, F; Yuan, H Q; Salamon, M B; Movshovich, R; Sarrao, J L; Thompson, J D

    2006-03-02

    With only a few exceptions that are well understood, conventional superconductivity does not coexist with long-range magnetic order (for example, ref. 1). Unconventional superconductivity, on the other hand, develops near a phase boundary separating magnetically ordered and magnetically disordered phases. A maximum in the superconducting transition temperature T(c) develops where this boundary extrapolates to zero Kelvin, suggesting that fluctuations associated with this magnetic quantum-critical point are essential for unconventional superconductivity. Invariably, though, unconventional superconductivity masks the magnetic phase boundary when T < T(c), preventing proof of a magnetic quantum-critical point. Here we report specific-heat measurements of the pressure-tuned unconventional superconductor CeRhIn5 in which we find a line of quantum-phase transitions induced inside the superconducting state by an applied magnetic field. This quantum-critical line separates a phase of coexisting antiferromagnetism and superconductivity from a purely unconventional superconducting phase, and terminates at a quantum tetracritical point where the magnetic field completely suppresses superconductivity. The T --> 0 K magnetic field-pressure phase diagram of CeRhIn5 is well described with a theoretical model developed to explain field-induced magnetism in the high-T(c) copper oxides, but in which a clear delineation of quantum-phase boundaries has not been possible. These experiments establish a common relationship among hidden magnetism, quantum criticality and unconventional superconductivity in copper oxides and heavy-electron systems such as CeRhIn5.

  11. Dispersive O+ conics observed in the plasma-sheet boundary layer with CRRES/LOMICS during a magnetic storm

    NASA Astrophysics Data System (ADS)

    Wüest, M.; Young, D. T.; Thomsen, M. F.; Barraclough, B. L.; Singer, H. J.; Anderson, R. R.

    1996-06-01

    We present initial results from the Low-energy magnetospheric ion composition sensor (LOMICS) on the Combined release and radiation effects satellite (CRRES) together with electron, magnetic field, and electric field wave data. LOMICS measures all important magnetospheric ion species (H+, He++, He+, O++, O+) simultaneously in the energy range 60 eV to 45 keV, as well as their pitch-angle distributions, within the time resolution afforded by the spacecraft spin period of 30 s. During the geomagnetic storm of 9 July 1991, over a period of 42 min (0734 UT to 0816 UT) the LOMICS ion mass spectrometer observed an apparent O+ conic flowing away from the southern hemisphere with a bulk velocity that decreased exponentially with time from 300 km/s to 50 km/s, while its temperature also decreased exponentially from 700 to 5 eV. At the onset of the O+ conic, intense low-frequency electromagnetic wave activity and strong pitch-angle scattering were also observed. At the time of the observations the CRRES spacecraft was inbound at Lapprox7.5 near dusk, magnetic local time (MLT), and at a magnetic latitude of -23°. Our analysis using several CRRES instruments suggests that the spacecraft was skimming along the plasma sheet boundary layer (PSBL) when the upward-flowing ion conic arrived. The conic appears to have evolved in time, both slowing and cooling, due to wave-particle interactions. We are unable to conclude whether the conic was causally associated with spatial structures of the PSBL or the central plasma sheet. Acknowledgements. This study is supported in part by the Ministry of Education, Science, Sports, and Culture in Japan, under a Grant-in-Aid for Scientific Research (Category B). Topical Editor D. Alcaydé thanks M. Lockwood and N. J. Fox for their help in evaluating this paper.->

  12. Numerical magnetohydrodynamic simulations of expanding flux ropes: Influence of boundary driving

    SciTech Connect

    Tacke, Thomas; Dreher, Jürgen; Sydora, Richard D.

    2013-07-15

    The expansion dynamics of a magnetized, current-carrying plasma arch is studied by means of time-dependent ideal MHD simulations. Initial conditions model the setup used in recent laboratory experiments that in turn simulate coronal loops [J. Tenfelde et al., Phys. Plasmas 19, 072513 (2012); E. V. Stenson and P. M. Bellan, Plasma Phys. Controlled Fusion 54, 124017 (2012)]. Boundary conditions of the electric field at the “lower” boundary, intersected by the arch, are chosen such that poloidal magnetic flux is injected into the domain, either localized at the arch footpoints themselves or halfway between them. These conditions are motivated by themore » tangential electric field expected to exist in the laboratory experiments due to the external circuit that drives the plasma current. The boundary driving is found to systematically enhance the expansion velocity of the plasma arch. While perturbations at the arch footpoints also deform its legs and create characteristic elongated segments, a perturbation between the footpoints tends to push the entire structure upwards, retaining an ellipsoidal shape.« less

  13. A compilation of unsteady turbulent boundary-layer experimental data

    NASA Technical Reports Server (NTRS)

    Carr, L. W.

    1981-01-01

    An extensive literature search was conducted and those experiments related to unsteady boundary layer behavior were cataloged. In addition, an international survey of industrial, university, and governmental research laboratories was made in which new and ongoing experimental programs associated with unsteady turbulent boundary layer research were identified. Pertinent references were reviewed and classified based on the technical emphasis of the various experiments. Experiments that include instantaneous or ensemble averaged profiles of boundary layer variables are stressed. The experimental apparatus and flow conditions are described and summaries of acquired data and significant conclusions are summarized. Measurements obtained from the experiments which exist in digital form were stored on magnetic tape. Instructions are given for accessing these data sets for further analysis.

  14. The Quasi-monochromatic ULF Wave Boundary in the Venusian Foreshock: Venus Express Observations

    NASA Astrophysics Data System (ADS)

    Shan, Lican; Mazelle, Christian; Meziane, Karim; Romanelli, Norberto; Ge, Yasong S.; Du, Aimin; Lu, Quanming; Zhang, Tielong

    2018-01-01

    The location of ultralow-frequency (ULF) quasi-monochromatic wave onset upstream of Venus bow shock is explored using Venus Express magnetic field data. We report the existence of a spatial foreshock boundary behind which ULF waves are present. We have found that the ULF wave boundary at Venus is sensitive to the interplanetary magnetic field (IMF) direction like the terrestrial one and appears well defined for a cone angle larger than 30°. In the Venusian foreshock, the inclination angle of the wave boundary with respect to the Sun-Venus direction increases with the IMF cone angle. We also found that for the IMF nominal direction (θBX = 36°) at Venus' orbit, the value of this inclination angle is 70°. Moreover, we have found that the inferred velocity of an ion traveling along the ULF boundary is in a qualitative agreement with a quasi-adiabatic reflection of a portion of the solar wind at the bow shock. For an IMF nominal direction at Venus, the inferred bulk speed of ions traveling along this boundary is 1.07 VSW, sufficiently enough to overcome the solar wind convection. This strongly suggests that the backstreaming ions upstream of the Venusian bow shock provide the main energy source for the ULF waves.

  15. Magnetic microspherules associated with the K/T and upper Eocene extinction events

    NASA Technical Reports Server (NTRS)

    Cisowski, Stanley M.

    1988-01-01

    Magnetic microspherules were identified in over 20 K/T boundary sites, and in numerous Deep Sea Drilling Project (DSDP) cores from the Caribbean and Pacific, synchronous with the extinction of several radiolarian species near the end of the Eocene. The K/T magnetic spherules are of particular interest as carriers of Ir and other siderophiles generally found in abundance in K/T boundary clay. Furthermore the textures and unusual chemistry of their component magnetic phases indicate an origin at high temperature, possibly related to (an) unusual event(s) marking the end of the Cretaceous and Eocene periods. Their origin, along with the non-magnetic (sanidine) spheules, is generally ascribed directly to megaimpact events hypothesized to have periodically disrupted life on Earth. A survey of microspherical forms associated with known meteorite and impact derived materials reveals fundamental differences from the extinction related spherules. Low temperature magnetic experiments on the K/T and Upper Eocene spheroids indicate that, unlike tektites, extremely small superparamagnetic carriers are not present in abundance. The extensive subaerial exposure of Cretaceous combustible black shale during sea level regression in the latest Cretaceous represents a potential source for the magnetic spheroids found in certain K/T boundary clays. The recent discovery of high Ir abundances distributed above and below the K/T boundary within shallow water sediments in Israel, which also contain the most extensive known zones of combustion metamorphism, the so called Mottled Zone, adds a further dramatic footnote to the proposed association between the magnetic spheroids and combustion of organic shales. Interestingly, the Mottled Zone also contains the rare mineral magnesioferrite, which was identified both within the K/T magnetic spheroids and as discrete crystals in boundary clay from marine and continental sites.

  16. Formation of the wave compressional boundary in the earth's foreshock

    NASA Technical Reports Server (NTRS)

    Skadron, George; Holdaway, Robert D.; Lee, Martin A.

    1988-01-01

    Using an evolutionary model and allowing for nonuniform proton injection and wave growth rates, the compressional wave boundaries corresponding to IMF inclinations to the solar wind of theta(BV) equal to 45 and 25 deg were located. The compressional boundaries deduced from this model were found to support the results of Greenstadt and Baum (1986) who have concluded that the observed compressional boundaries are incompatible with wave growth at a fixed growth rate, due to the interaction of a uniform beam with the solar wind. The results indicate, however, that the compressional boundaries are quite compatible with nonuniform beams and growth rates which result from the coupled evolution of the energetic protons and the waves with which they interact. It was found that, in the solar wind frame, the dominant wave-particle interaction in the outer foreshock is the damping of inward propagating (toward the shock) left-polarized waves, producing a magnetically quiet region immediately downstream of the foreshock boundary.

  17. Symmetries and Boundary Conditions with a Twist

    NASA Astrophysics Data System (ADS)

    Zawadzki, Krissia; D'Amico, Irene; Oliveira, Luiz N.

    2017-10-01

    Interest in finite-size systems has risen in the last decades, due to the focus on nanotechnological applications and because they are convenient for numerical treatment that can subsequently be extrapolated to infinite lattices. Independently of the envisioned application, special attention must be given to boundary condition, which may or may not preserve the symmetry of the infinite lattice. Here, we present a detailed study of the compatibility between boundary conditions and conservation laws. The conflict between open boundary conditions and momentum conservation is well understood, but we examine other symmetries, as well: we discuss gauge invariance, inversion, spin, and particle-hole symmetry and their compatibility with open, periodic, and twisted boundary conditions. In the interest of clarity, we develop the reasoning in the framework of the one-dimensional half-filled Hubbard model, whose Hamiltonian displays a variety of symmetries. Our discussion includes analytical and numerical results. Our analytical survey shows that, as a rule, boundary conditions break one or more symmetries of the infinite-lattice Hamiltonian. The exception is twisted boundary condition with the special torsion Θ = πL/2, where L is the lattice size. Our numerical results for the ground-state energy at half-filling and the energy gap for L = 2-7 show how the breaking of symmetry affects the convergence to the L → ∞ limit. We compare the computed energies and gaps with the exact results for the infinite lattice drawn from the Bethe-Ansatz solution. The deviations are boundary-condition dependent. The special torsion yields more rapid convergence than open or periodic boundary conditions. For sizes as small as L = 7, the numerical results for twisted condition are very close to the L → ∞ limit. We also discuss the ground-state electronic density and magnetization at half filling under the three boundary conditions.

  18. Thickness dependence of the levitation performance of double-layer high-temperature superconductor bulks above a magnetic rail

    NASA Astrophysics Data System (ADS)

    Sun, R. X.; Zheng, J.; Liao, X. L.; Che, T.; Gou, Y. F.; He, D. B.; Deng, Z. G.

    2014-10-01

    A double-layer high-temperature superconductor (HTSC) arrangement was proposed and proved to be able to bring improvements to both levitation force and guidance force compared with present single-layer HTSC arrangement. To fully exploit the applied magnetic field by a magnetic rail, the thickness dependence of a double-layer HTSC arrangement on the levitation performance was further investigated in the paper. In this study, the lower-layer bulk was polished step by step to different thicknesses, and the upper-layer bulk with constant thickness was directly superimposed on the lower-layer one. The levitation force and the force relaxation of the double-layer HTSC arrangement were measured above a Halbach magnetic rail. Experimental result shows that a bigger levitation force and a less levitation force decay could be achieved by optimizing the thickness of the lower-layer bulk HTSC. This thickness optimization method could be applied together with former reported double-layer HTSC arrangement method with aligned growth sector boundaries pattern. This series of study on the optimized combination method do bring a significant improvement on the levitation performance of present HTS maglev systems.

  19. Fragmentation of a Filamentary Cloud Permeated by a Perpendicular Magnetic Field

    SciTech Connect

    Hanawa, Tomoyuki; Kudoh, Takahiro; Tomisaka, Kohji

    We examine the linear stability of an isothermal filamentary cloud permeated by a perpendicular magnetic field. Our model cloud is assumed to be supported by gas pressure against self-gravity in the unperturbed state. For simplicity, the density distribution is assumed to be symmetric around the axis. Also for simplicity, the initial magnetic field is assumed to be uniform, and turbulence is not taken into account. The perturbation equation is formulated to be an eigenvalue problem. The growth rate is obtained as a function of the wavenumber for fragmentation along the axis and the magnetic field strength. The growth rate dependsmore » critically on the outer boundary. If the displacement vanishes in regions very far from the cloud axis (fixed boundary), cloud fragmentation is suppressed by a moderate magnetic field, which means the plasma beta is below 1.67 on the cloud axis. If the displacement is constant along the magnetic field in regions very far from the cloud, the cloud is unstable even when the magnetic field is infinitely strong. The cloud is deformed by circulation in the plane perpendicular to the magnetic field. The unstable mode is not likely to induce dynamical collapse, since it is excited even when the whole cloud is magnetically subcritical. For both boundary conditions, the magnetic field increases the wavelength of the most unstable mode. We find that the magnetic force suppresses compression perpendicular to the magnetic field especially in regions of low density.« less

  20. Ferromagnetic behaviour of ZnO: the role of grain boundaries

    PubMed Central

    Protasova, Svetlana G; Mazilkin, Andrei A; Goering, Eberhard; Schütz, Gisela; Straumal, Petr B; Baretzky, Brigitte

    2016-01-01

    The possibility to attain ferromagnetic properties in transparent semiconductor oxides such as ZnO is very promising for future spintronic applications. We demonstrate in this review that ferromagnetism is not an intrinsic property of the ZnO crystalline lattice but is that of ZnO/ZnO grain boundaries. If a ZnO polycrystal contains enough grain boundaries, it can transform into the ferromagnetic state even without doping with “magnetic atoms” such as Mn, Co, Fe or Ni. However, such doping facilitates the appearance of ferromagnetism in ZnO. It increases the saturation magnetisation and decreases the critical amount of grain boundaries needed for FM. A drastic increase of the total solubility of dopants in ZnO with decreasing grain size has been also observed. It is explained by the multilayer grain boundary segregation. PMID:28144542

  1. Toroidal current asymmetry and boundary conditions in disruptions

    NASA Astrophysics Data System (ADS)

    Strauss, Henry

    2014-10-01

    It was discovered on JET that disruptions were accompanied by toroidal asymmetry of the plasma current. The toroidal current asymmetry ΔIϕ is proportional to the vertical current moment ΔMIZ , with positive sign for an upward vertical displacement event (VDE) and negative sign for a downward VDE. It was claimed that this could only be explained by Hiro current. It is shown that instead it is essentially a kinematic effect produced by the VDE displacement of a 3D magnetic perturbation. This is verified by M3D simulations. The simulation results do not require penetration of plasma into the boundary, as in the Hiro current model. It is shown that the normal velocity perpendicular to the magnetic field vanishes at the wall, in the small Larmor radius limit of electromagnetic sheath boundary conditions. Plasma is absorbed into the wall only via the parallel velocity, which is small, penetrates only an infinitesimal distance into the wall, and does not affect forces exerted by the plasma on the wall. Supported by USDOE and ITER.

  2. Source-sector contributions to European ozone and fine PM in 2010 using AQMEII modeling data

    NASA Astrophysics Data System (ADS)

    Karamchandani, Prakash; Long, Yoann; Pirovano, Guido; Balzarini, Alessandra; Yarwood, Greg

    2017-05-01

    Source apportionment modeling provides valuable information on the contributions of different source sectors and/or source regions to ozone (O3) or fine particulate matter (PM2.5) concentrations. This information can be useful in designing air quality management strategies and in understanding the potential benefits of reducing emissions from a particular source category. The Comprehensive Air quality Model with Extensions (CAMx) offers unique source attribution tools, called the Ozone and Particulate Source Apportionment Technology (OSAT/PSAT), which track source contributions. We present results from a CAMx source attribution modeling study for a summer month and a winter month using a recently evaluated European CAMx modeling database developed for Phase 3 of the Air Quality Model Evaluation International Initiative (AQMEII). The contributions of several source sectors (including model boundary conditions of chemical species representing transport of emissions from outside the modeling domain as well as initial conditions of these species) to O3 or PM2.5 concentrations in Europe were calculated using OSAT and PSAT, respectively. A 1-week spin-up period was used to reduce the influence of initial conditions. Evaluation focused on 16 major cities and on identifying source sectors that contributed above 5 %. Boundary conditions have a large impact on summer and winter ozone in Europe and on summer PM2.5, but they are only a minor contributor to winter PM2.5. Biogenic emissions are important for summer ozone and PM2.5. The important anthropogenic sectors for summer ozone are transportation (both on-road and non-road), energy production and conversion, and industry. In two of the 16 cities, solvent and product also contributed above 5 % to summertime ozone. For summertime PM2.5, the important anthropogenic source sectors are energy, transportation, industry, and agriculture. Residential wood combustion is an important anthropogenic sector in winter for PM2.5 over

  3. E and F region study of the evening sector auroral oval - A Chatanika/Dynamics Explorer 2/NOAA 6 comparison

    NASA Technical Reports Server (NTRS)

    Senior, C.; Sharber, J. R.; Winningham, J. D.; De La Beaujardiere, O.; Heelis, R. A.; Evans, D. S.; Sugiura, M.; Hoegy, W. R.

    1987-01-01

    Simultaneous data from the Chatanika radar and the DE 2 and NOAA 6 satellites are used to study the typical behavior of the winter evening-sector auroral plasma during moderate and steady magnetic activity. The equatorward edge of the auroral E layer, of the region 2 field-aligned currents, and of the region of intense convection are colocated. The auroral E layer extends several degrees south of the equatorward edge of the keV electron precipitation from the CPS. Although the main trough and ionization channel are embedded in a region of intense electric field where the plasma flows sunward at high speed, the flux tubes associated with these two features have different time histories. The midlatitude trough is located south of the region of electron precipitation, above a proton aurora. The ionization channel marks the poleward edge of the main trough and is colocated with the equatorward boundary of the electron precipitation from the central plasma sheet.

  4. Initializing a Mesoscale Boundary-Layer Model with Radiosonde Observations

    NASA Astrophysics Data System (ADS)

    Berri, Guillermo J.; Bertossa, Germán

    2018-01-01

    A mesoscale boundary-layer model is used to simulate low-level regional wind fields over the La Plata River of South America, a region characterized by a strong daily cycle of land-river surface-temperature contrast and low-level circulations of sea-land breeze type. The initial and boundary conditions are defined from a limited number of local observations and the upper boundary condition is taken from the only radiosonde observations available in the region. The study considers 14 different upper boundary conditions defined from the radiosonde data at standard levels, significant levels, level of the inversion base and interpolated levels at fixed heights, all of them within the first 1500 m. The period of analysis is 1994-2008 during which eight daily observations from 13 weather stations of the region are used to validate the 24-h surface-wind forecast. The model errors are defined as the root-mean-square of relative error in wind-direction frequency distribution and mean wind speed per wind sector. Wind-direction errors are greater than wind-speed errors and show significant dispersion among the different upper boundary conditions, not present in wind speed, revealing a sensitivity to the initialization method. The wind-direction errors show a well-defined daily cycle, not evident in wind speed, with the minimum at noon and the maximum at dusk, but no systematic deterioration with time. The errors grow with the height of the upper boundary condition level, in particular wind direction, and double the errors obtained when the upper boundary condition is defined from the lower levels. The conclusion is that defining the model upper boundary condition from radiosonde data closer to the ground minimizes the low-level wind-field errors throughout the region.

  5. 3D modeling of the total electric field induced by transcranial magnetic stimulation using the boundary element method

    NASA Astrophysics Data System (ADS)

    Salinas, F. S.; Lancaster, J. L.; Fox, P. T.

    2009-06-01

    Transcranial magnetic stimulation (TMS) delivers highly localized brain stimulations via non-invasive externally applied magnetic fields. This non-invasive, painless technique provides researchers and clinicians with a unique tool capable of stimulating both the central and peripheral nervous systems. However, a complete analysis of the macroscopic electric fields produced by TMS has not yet been performed. In this paper, we addressed the importance of the secondary E-field created by surface charge accumulation during TMS using the boundary element method (BEM). 3D models were developed using simple head geometries in order to test the model and compare it with measured values. The effects of tissue geometry, size and conductivity were also investigated. Finally, a realistically shaped head model was used to assess the effect of multiple surfaces on the total E-field. Secondary E-fields have the greatest impact at areas in close proximity to each tissue layer. Throughout the head, the secondary E-field magnitudes typically range from 20% to 35% of the primary E-field's magnitude. The direction of the secondary E-field was generally in opposition to the primary E-field; however, for some locations, this was not the case (i.e. going from high to low conductivity tissues). These findings show that realistically shaped head geometries are important for accurate modeling of the total E-field.

  6. Fullerenes and interplanetary dust at the Permian-Triassic boundary.

    PubMed

    Poreda, Robert J; Becker, Luann

    2003-01-01

    We recently presented new evidence that an impact occurred approximately 250 million years ago at the Permian-Triassic boundary (PTB), triggering the most severe mass extinction in the history of life on Earth. We used a new extraterrestrial tracer, fullerene, a third carbon carrier of noble gases besides diamond and graphite. By exploiting the unique properties of this molecule to trap noble gases inside of its caged structure (helium, neon, argon), the origin of the fullerenes can be determined. Here, we present new evidence for fullerenes with extraterrestrial noble gases in the PTB at Graphite Peak, Antarctica, similar to PTB fullerenes from Meishan, China and Sasayama, Japan. In addition, we isolated a (3)He-rich magnetic carrier phase in three fractions from the Graphite Peak section. The noble gases in this magnetic fraction were similar to zero-age deep-sea interplanetary dust particles (IDPs) and some magnetic grains isolated from the Cretaceous-Tertiary boundary. The helium and neon isotopic compositions for both the bulk Graphite Peak sediments and an isolated magnetic fraction from the bulk material are consistent with solar-type gases measured in zero-age deep-sea sediments and point to a common source, namely, the flux of IDPs to the Earth's surface. In this instance, the IDP noble gas signature for the bulk sediment can be uniquely decoupled from fullerene, demonstrating that two separate tracers are present (direct flux of IDPs for (3)He vs. giant impact for fullerene).

  7. Study of the Cooldown and Warmup for the Eight Sectors of the Large Hadron Collider

    NASA Astrophysics Data System (ADS)

    Liu, L.; Riddone, G.; Tavian, L.

    2004-06-01

    The LHC cryogenic system is based on a five-point feed scheme with eight refrigerators serving the eight sectors of the LHC machine. The paper presents the simplified flow scheme of the eight sectors and the mathematical methods including the program flowchart and the boundary conditions to simulate the cooldown and warmup of these sectors. The methods take into account the effect of the pressure drop across the valves as well as the pressure evolution in the different headers of the cryogenic distribution line. The simulated pressure and temperature profiles of headers of the LHC sector during the cooldown and warmup are given and the temperature evolutions of entire processes of cooldown and warmup are presented. As a conclusion, the functions of the input temperature for the normal and fast cooldown and warmup, the cooldown and warmup time of each sector and the distributions of mass flow rates in each sector are summarized. The results indicate that it is possible to cool down any of the LHC sector within 12.7 days in normal operation and 6.8 days in case of fast operation.

  8. Formation of the Dayside Magnetopause and Its Boundary Layers Under the Radial IMF

    NASA Astrophysics Data System (ADS)

    Pi, Gilbert; Němeček, Zdeněk.; Å afránková, Jana; Grygorov, Kostiantyn; Shue, Jih-Hong

    2018-05-01

    The global structure of magnetopause boundary layers under the radial interplanetary magnetic field (IMF) conditions is studied by a comparison of experimental and simulation results. In magnetohydrodynamic simulations, the hemispherical asymmetry of the reconnection locations was found. The draped field adjacent to the magnetopause points northward in the Northern Hemisphere, but it is oriented southward in the Southern Hemisphere at the beginning of the simulation for negative IMF Bx. The magnetopause region affected by the positive IMF Bz component enlarges over time, and the density profile exhibit a north-south asymmetry near the magnetopause. The experimental part of the study uses the Time History of Events and Macroscale Interactions during Substorm data. We analyze profiles of the plasma parameters and magnetic field as well as the ion pitch-angle distributions. The nonsimultaneous appearance of parallel and antiparallel aligned flows suggests two spatially separated sources of these flows. We have identified (1) the inner part of the low-latitude boundary layer (LLBL) on closed magnetic field lines; (2) the outer LLBL on open field lines; (3) the inner part of the magnetosheath boundary layer (MSBL) formed by dayside reconnection in the Southern Hemisphere; and (4) the outer MSBL resulting from lobe reconnection in the Northern Hemisphere.

  9. Magnetic thin-film split-domain current sensor-recorder

    DOEpatents

    Hsieh, Edmund J.

    1979-01-01

    A sensor-recorder for recording a representation of the direction and peak amplitude of a transient current. A magnetic thin film is coated on a glass substrate under the influence of a magnetic field so that the finished film is magnetically uniaxial and anisotropic. The film is split into two oppositely magnetized contiguous domains with a central boundary by subjecting adjacent portions of the film simultaneously to magnetic fields that are opposed 180.degree.. With the split-domain sensor-recorder placed with the film plane and domain boundary either perpendicular or parallel to the expected conductive path of a transient current, the occurrence of the transient causes switching of a portion of one domain to the direction of the other domain. The amount of the switched domain portion is indicative of the amplitude of the peak current of the transient, while the particular domain that is switched is indicative of the direction of the current. The resulting domain patterns may be read with a passive magnetic tape viewer.

  10. Magnetic flux transport of decaying active regions and enhanced magnetic network. [of solar supergranulation

    NASA Technical Reports Server (NTRS)

    Wang, Haimin; Zirin, Harold; Ai, Guoxiang

    1991-01-01

    Several series of coordinated observations on decaying active regions and enhanced magnetic network regions on the sun were carried out jointly at Big Bear Solar Observatory and at the Huairou Solar Observing Station of the Bejing Astronomical Observatory in China. The magnetic field evolution in several regions was followed closely for three to seven days. The magnetic flux transport from the remnants of decayed active regions was studied, along with the evolution and lifetime of the magnetic network which defines the boundaries of supergranules. The magnetic flux transport in an enhanced network region was studied in detail and found to be negative. Also briefly described are some properties of moving magnetic features around a sunspot. Results of all of the above studies are presented.

  11. Role of Transtension in Rifting at the Pacific-North America Plate Boundary

    NASA Astrophysics Data System (ADS)

    Stock, J. M.

    2011-12-01

    Transtensional plate motion can be accommodated either in a localized zone of transtensional rifting or over a broader region. Broader zones of deformation can be classified either as diffuse deformation or strain partitioning (one or more major strike-slip shear zones geographically offset from a region of a extensional faulting). The Pacific-North America plate boundary in southwestern North America was transtensional during much of its history and has exhibited the full range of these behaviors at different spatial scales and in different locations, as recorded by fault motions and paleomagnetic rotations. Here we focus on the northern Gulf of California part of the plate boundary (Upper and Lower Delfin basin segments), which has been in a zone of transtensional Pacific-North America plate boundary motion ever since the middle Miocene demise of adjacent Farallon-derived microplates. Prior to the middle Miocene, during the time of microplate activity, this sector of North America experienced basin-and-range normal faults (core complexes) in Sonora. However there is no evidence of continued extensional faulting nor of a Gulf-related topographic depression until after ca 12 Ma when a major ignimbrite (Tuff of San Felipe/ Ignimbrite of Hermosillo) was deposited across the entire region of the future Gulf of California rift in this sector. After 12 Ma, faults disrupted this marker bed in eastern Baja California and western Sonora, and some major NNW-striking right-lateral faults are inferred to have developed near the Sonoran coast causing offset of some of the volcanic facies. However, there are major tectonic rotations of the volcanic rocks in NE Baja California between 12 and 6 Ma, suggesting that the plate boundary motion was still occurring over a broad region. By contrast, after about 6 Ma, diminished rotations in latest Miocene and Pliocene volcanic rocks, as well as fault slip histories, show that plate boundary deformation became localized to a narrower

  12. Plasma Boundary Collisionless Absorption Effects in the Loading of RF Conductors,

    DTIC Science & Technology

    1979-10-01

    a quasi-thermodynamic equilibrium between the charged particles and the applied RF potential. It is clear that the effect of external magnetic fields...AO-AOBI 115 CALIFORNIA UNIV LOS ANBELES PLASMA PHYSICS BROUP F/6O 20/9 PLASMA BOUNDARY COLLISIONLESS ABSORPTION EFFECTS IN THE LbADINGS-E*IC(U) OCT...79 B J MORALES N00OOIATB-C-0NA NLASIED PPB-435 NL mii-hiiiii PLASMA BOUNDARY COLLISIONLESS ABSORPTION EFFECTS IN THE LOADING OF ONDUCTOR) (𔃻.J. Oral

  13. Kinetics of Magnetoelastic Twin-Boundary Motion in Ferromagnetic Shape-Memory Alloys

    NASA Astrophysics Data System (ADS)

    Pramanick, A.; Wang, X.-L.; Stoica, A. D.; Yu, C.; Ren, Y.; Tang, S.; Gai, Z.

    2014-05-01

    We report the kinetics of twin-boundary motion in the ferromagnetic shape-memory alloy of Ni-Mn-Ga as measured by in situ high energy synchrotron diffraction. The temporal evolution of twin reorientation during the application of a magnetic field is described by thermally activated creep motion of twin boundaries over a distribution of energy barriers. The dynamical creep exponent μ was found to be ˜0.5, suggesting that the distribution of energy barriers is a result of short-range disorders.

  14. Evidence for preferential flux flow at the grain boundaries of superconducting RF-quality niobium

    SciTech Connect

    Sung, Z. -H.; Lee, P. J.; Gurevich, A.

    Here, the question of whether grain boundaries (GBs) in niobium can be responsible for lowered operating field (B RF) or quality factor (Q 0) in superconducting radio-frequency (SRF) cavities is still controversial. Here, we show by direct DC transport across planar grain boundaries isolated from a slice of very large-grain SRF-quality Nb that vortices can preferentially flow along the grain boundary when the external magnetic field lies in the GB plane. However, increasing the misalignment between the GB plane and the external magnetic field vector markedly reduces preferential flux flow along GB. Importantly, we find that preferential GB flux flowmore » is more prominent for a buffered chemical polished than for an electropolished bi-crystal. The voltage-current characteristics of GBs are similar to those seen in low angle grain boundaries of high temperature superconductors where there is clear evidence of suppression of the superconducting order parameter at the GB. While local weakening of superconductivity at GBs in cuprates and pnictides is intrinsic, deterioration of current transparency of GBs in Nb appears to be extrinsic, since the polishing method clearly affect the local GB degradation. The dependence of preferential GB flux flow on important cavity preparation and experimental variables, particularly, the final chemical treatment and the angle between the magnetic field and the GB plane, suggests two more reasons why real cavity performance can be so variable.« less

  15. Evidence for preferential flux flow at the grain boundaries of superconducting RF-quality niobium

    DOE PAGES

    Sung, Z. -H.; Lee, P. J.; Gurevich, A.; ...

    2018-02-19

    Here, the question of whether grain boundaries (GBs) in niobium can be responsible for lowered operating field (B RF) or quality factor (Q 0) in superconducting radio-frequency (SRF) cavities is still controversial. Here, we show by direct DC transport across planar grain boundaries isolated from a slice of very large-grain SRF-quality Nb that vortices can preferentially flow along the grain boundary when the external magnetic field lies in the GB plane. However, increasing the misalignment between the GB plane and the external magnetic field vector markedly reduces preferential flux flow along GB. Importantly, we find that preferential GB flux flowmore » is more prominent for a buffered chemical polished than for an electropolished bi-crystal. The voltage-current characteristics of GBs are similar to those seen in low angle grain boundaries of high temperature superconductors where there is clear evidence of suppression of the superconducting order parameter at the GB. While local weakening of superconductivity at GBs in cuprates and pnictides is intrinsic, deterioration of current transparency of GBs in Nb appears to be extrinsic, since the polishing method clearly affect the local GB degradation. The dependence of preferential GB flux flow on important cavity preparation and experimental variables, particularly, the final chemical treatment and the angle between the magnetic field and the GB plane, suggests two more reasons why real cavity performance can be so variable.« less

  16. Boundary streaming with Navier boundary condition.

    PubMed

    Xie, Jin-Han; Vanneste, Jacques

    2014-06-01

    In microfluidic applications involving high-frequency acoustic waves over a solid boundary, the Stokes boundary-layer thickness δ is so small that some non-negligible slip may occur at the fluid-solid interface. This paper assesses the impact of this slip by revisiting the classical problem of steady acoustic streaming over a flat boundary, replacing the no-slip boundary condition with the Navier condition u|_{y=0}=L_{s}∂_{y}u|_{y=0}, where u is the velocity tangent to the boundary y=0, and the parameter L_{s} is the slip length. A general expression is obtained for the streaming velocity across the boundary layer as a function of the dimensionless parameter L_{s}/δ. The limit outside the boundary layer provides an effective slip velocity satisfied by the interior mean flow. Particularizing to traveling and standing waves shows that the boundary slip respectively increases and decreases the streaming velocity.

  17. The memory of the accreting plate boundary and the continuity of fracture zones

    USGS Publications Warehouse

    Schouten, Hans; Klitgord, Kim D.

    1982-01-01

    A detailed aeromagnetic anomaly map of the Mesozoic seafloor-spreading lineations southwest of Bermuda reveals the dominant magnetic grain of the oceanic crust and the character of the accreting boundary at the time of crustal formation. The magnetic anomaly pattern is that of a series of elongate lobes perpendicular to the fracture zone (flowline) trends. The linear sets of magnetic anomaly peaks and troughs have narrow regions of reduced amplitude anomalies associated with the fracture zones. During the period of Mesozoic geomagnetic polarity reversals (when 1200 km of central North Atlantic seafloor formed), the Atlantic accreting boundary consisted of stationary, elongate, spreading center cells that maintained their independence even though sometimes only minor spatial offsets existed between cells. Normal oceanic crustal structure was formed in the spreading center cells, but structural anomalies and discontinuities characteristic of fracture zones were formed at their boundaries, which parallel flowlines of Mesozoic relative plate motion in the central North Atlantic. We suggest that the memory for a stationary pattern of independent spreading center cells resides in the young brittle lithosphere at the accreting boundary where the lithosphere is weakest; here, each spreading center cell independently goes through its cylce of stress buildup, stress release, and crustal accretion, after which its memory is refreshed. The temporal offset between the peaks of the accretionary activity that takes place within each cell may provide the mechanism for maintaining the independence of adjacent spreading center cells through times when no spatial offset between the cells exists.

  18. Integrated geophysical characterisation of Sunyani municipal solid waste disposal site using magnetic gradiometry, magnetic susceptibility survey and electrical resistivity tomography

    NASA Astrophysics Data System (ADS)

    Appiah, Isaac; Wemegah, David Dotse; Asare, Van-Dycke Sarpong; Danuor, Sylvester K.; Forson, Eric Dominic

    2018-06-01

    Non-invasive geophysical investigation using magnetic gradiometry, magnetic susceptibility survey and electrical resistivity tomography (ERT) was carried out on the Sunyani Municipal Assembly (SMA) solid waste disposal (SWD) site. The study was aimed at delineating the physical boundaries and the area extent of the waste deposit, mapping the distribution of the waste at the site, detecting and delineating zones of leachate contamination and its preferential migration pathways beneath the waste deposit and its surroundings. The results of both magnetic susceptibility and gradiometric methods displayed in anomaly maps clearly delineated the physical boundaries of the waste deposit with an approximate area extent of 82,650 m2 that are characterised by high magnetic susceptibilities between 426 × 10-5 SI and 9890 × 10-5 SI. They also revealed high magnetic anomalies erratically distributed within the waste deposit attributable to its heterogeneous and uncontrolled nature. The high magnetic anomalies outside the designated waste boundaries were also attributed to indiscriminate deposition of the waste. Similarly, the ERT sections delineated and characterised zones of leachate contamination beneath the waste body and its close surroundings as well as pathways for leachate migration with low resistivity signatures up to 43.9 Ωm. In spite of the successes reported herein using the ERT, this research also revealed that the ERT is less effective in estimating the thickness of the waste deposit in unlined SWD sites due to leachate infiltration into the ground beneath it that masks the resistivities of the top level ground and makes it indistinguishable from the waste body.

  19. Charting the Interstellar Magnetic Field causing the Interstellar Boundary Explorer (IBEX) Ribbon of Energetic Neutral Atoms

    NASA Astrophysics Data System (ADS)

    Frisch, P. C.; Berdyugin, A.; Piirola, V.; Magalhaes, A. M.; Seriacopi, D. B.; Wiktorowicz, S. J.; Andersson, B.-G.; Funsten, H. O.; McComas, D. J.; Schwadron, N. A.; Slavin, J. D.; Hanson, A. J.; Fu, C.-W.

    2015-12-01

    The interstellar magnetic field (ISMF) near the heliosphere is a fundamental component of the solar galactic environment that can only be studied using polarized starlight. The results of an ongoing survey of the linear polarizations of local stars are analyzed with the goal of linking the ISMF that shapes the heliosphere to the nearby field in interstellar space. We present new results on the direction of the magnetic field within 40 pc obtained from analyzing polarization data using a merit function that determines the field direction that provides the best fit to the polarization data. Multiple magnetic components are identified, including a dominant interstellar field, {B}{POL}, that is aligned with the direction ℓ, b = 36.°2, 49.°0 (±16.°0). Stars tracing {B}{POL} have the same mean distance as stars that do not trace {B}{POL}, but show weaker average polarizations consistent with a smaller column density of polarizing material. {B}{POL} is aligned with the ISMF traced by the IBEX Ribbon to within {7.6}-7.6+14.9 degrees. The variations in the polarization position angle directions derived from the data that best match {B}{POL} indicate a low level of magnetic turbulence, ˜9° ± 1°. The direction of {B}{POL} is obtained after excluding polarization data tracing a separate magnetic structure that appears to be associated with interstellar dust deflected around the heliosphere. The velocities of local interstellar clouds relative to the Local Standard of Rest (LSR) increase with the angles between the LSR velocities and {B}{POL}, indicating that the kinematics of local interstellar material is ordered by the ISMF. The Loop I superbubble that extends close to the Sun contains dust that reddens starlight and whose distance is determined by the color excess E(B - V) of starlight. Polarizations caused by grains aligned with respect to {B}{POL} are consistent with the location of the Sun in the rim of the Loop I superbubble. An angle of {76

  20. Lorentz violation in the gravity sector: The t puzzle

    NASA Astrophysics Data System (ADS)

    Bonder, Yuri

    2015-06-01

    Lorentz violation is a candidate quantum-gravity signal, and the Standard-Model Extension (SME) is a widely used parametrization of such a violation. In the gravitational SME sector, there is an elusive coefficient for which no effects have been found. This is known as the t puzzle and, to date, it has no compelling explanation. This paper analyzes whether there is a fundamental explanation for the t puzzle. To tackle this question, several approaches are followed. Mainly, redefinitions of the dynamical fields are studied, showing that other SME coefficients can be moved to nongravitational sectors. It is also found that the gravity SME sector can be consistently treated à la Palatini, and that, in the presence of spacetime boundaries, it is possible to correct its action to get the desired equations of motion. Moreover, through a reformulation as a Lanczos-type tensor, some problematic features of the t term, which should arise at the phenomenological level, are revealed. The most important conclusion of the paper is that there is no evidence of a fundamental explanation for the t puzzle, suggesting that it may be linked to the approximations taken at the phenomenological level.

  1. An improved determination of the lithium depletion boundary age of Blanco 1 and a first look on the effects of magnetic activity

    SciTech Connect

    Juarez, Aaron J.; Stassun, Keivan G.; Cargile, Phillip A.

    2014-11-10

    The lithium depletion boundary (LDB) is a robust method for accurately determining the ages of young clusters, but most pre-main-sequence models used to derive LDB ages do not include the effects of magnetic activity on stellar properties. In light of this, we present results from our spectroscopic study of the very-low-mass members of the southern open cluster Blanco 1 using the Gemini-North Telescope, program IDs: GN-2009B-Q-53 and GN-2010B-Q-96. We obtained Gemini Multi-Object Spectrograph spectra at intermediate resolution for cluster candidate members with I ≈ 13-20 mag. From our sample of 43 spectra, we find 14 probable cluster members by consideringmore » proximity to the cluster sequence in an I/I – K {sub s} color-magnitude diagram, agreement with the cluster's systemic radial velocity, and magnetic activity as a youth indicator. We systematically analyze the Hα and Li features and update the LDB age of Blanco 1 to be 126{sub −14}{sup +13} Myr. Our new LDB age for Blanco 1 shows remarkable coevality with the benchmark Pleiades open cluster. Using available empirical activity corrections, we investigate the effects of magnetic activity on the LDB age of Blanco 1. Accounting for activity, we infer a corrected LDB age of 114{sub −10}{sup +9} Myr. This work demonstrates the importance of accounting for magnetic activity on LDB inferred stellar ages, suggesting the need to reinvestigate previous LDB age determinations.« less

  2. The western submerged sector of the Ischia volcanic island (Tyrrhenian Sea, Italy): new insights into its volcano-tectonic evolution

    NASA Astrophysics Data System (ADS)

    Passaro, Salvatore; de Alteriis, Giovanni; Milano, Girolamo; Fedi, Maurizio; Florio, Giovanni

    2010-05-01

    The Island of Ischia is a volcanic complex located in the northern boundary of the Gulf of Naples (south-eastern Tyrrhenian Sea, Italy). The island represents only the 30% of a larger, E-W trending, volcanic ridge and likely controlled by a regional tectonic lineament. Despite the many geo-volcanological and geophysical investigations conducted on the island since long time, still little is the knowledge of its offshore. Several marine surveys have been carried out over the past 10 years from IAMC - CNR research institute (Naples, Italy) mostly in the frame of INGV and GNV projects, funded by Italy Civil Protection Department. Such surveys have largely improved the knowledge of the entire volcanic complex. Multibeam bathymetry surveys has revealed several, previously unexpected, morphological and morphostructural features. Moreover some structural patterns and volcano alignments offshore show similarities with those occurring at a regional scale in the Campania region and, locally, between the island of Procida and Phlegrean Fields. Here we report the joint interpretation of geophysical data focused on the western underwater sector of the island. Interpretation was chiefly based on processing/inversion of magnetic data in turn constrained by bathymetry and seismic reflection profiles. Magnetic data, acquired by the IAMC during two different cruises in 2000 and 2002 onboard of the Urania R/V oceanographic vessel, put in evidence that the western seafloor of Ischia is characterized by the presence of a strong residual magnetic anomaly field of complex behaviour, somewhere correlated to local bathymetry. These two last methods allowed to define and distinguish between undersea and subsurface magnetic (i.e. magmatic) basement. Interpretation was also constrained by seismological data.

  3. Transition from the Unipolar Region to the Sector Zone: Voyager 2, 2013 and 2014

    NASA Astrophysics Data System (ADS)

    Burlaga, L. F.; Ness, N. F.; Richardson, J. D.

    2017-05-01

    We discuss magnetic field and plasma observations of the heliosheath made by Voyager 2 (V2) during 2013 and 2014 near solar maximum. A transition from a unipolar region to a sector zone was observed in the azimuthal angle λ between ˜2012.45 and 2013.82. The distribution of λ was strongly singly peaked at 270^\\circ in the unipolar region and double peaked in the sector zone. The δ-distribution was strongly peaked in the unipolar region and very broad in the sector zone. The distribution of daily averages of the magnetic field strength B was Gaussian in the unipolar region and lognormal in the sector zone. The correlation function of B was exponential with an e-folding time of ˜5 days in both regions. The distribution of hourly increments of B was a Tsallis distribution with nonextensivity parameter q = 1.7 ± 0.04 in the unipolar region and q = 1.44 ± 0.12 in the sector zone. The CR-B relationship qualitatively describes the 2013 observations, but not the 2014 observations. A 40 km s-1 increase in the bulk speed associated with an increase in B near 2013.5 might have been produced by the merging of streams. A “D sheet” (a broad depression in B containing a current sheet moved past V2 from days 320 to 345, 2013. The R- and N-components of the plasma velocity changed across the current sheet.

  4. Large-Scale Dynamics of the Magnetospheric Boundary: Comparisons between Global MHD Simulation Results and ISTP Observations

    NASA Technical Reports Server (NTRS)

    Berchem, J.; Raeder, J.; Ashour-Abdalla, M.; Frank, L. A.; Paterson, W. R.; Ackerson, K. L.; Kokubun, S.; Yamamoto, T.; Lepping, R. P.

    1998-01-01

    Understanding the large-scale dynamics of the magnetospheric boundary is an important step towards achieving the ISTP mission's broad objective of assessing the global transport of plasma and energy through the geospace environment. Our approach is based on three-dimensional global magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere- ionosphere system, and consists of using interplanetary magnetic field (IMF) and plasma parameters measured by solar wind monitors upstream of the bow shock as input to the simulations for predicting the large-scale dynamics of the magnetospheric boundary. The validity of these predictions is tested by comparing local data streams with time series measured by downstream spacecraft crossing the magnetospheric boundary. In this paper, we review results from several case studies which confirm that our MHD model reproduces very well the large-scale motion of the magnetospheric boundary. The first case illustrates the complexity of the magnetic field topology that can occur at the dayside magnetospheric boundary for periods of northward IMF with strong Bx and By components. The second comparison reviewed combines dynamic and topological aspects in an investigation of the evolution of the distant tail at 200 R(sub E) from the Earth.

  5. Magnetic charge distribution and stray field landscape of asymmetric néel walls in a magnetically patterned exchange bias layer system

    NASA Astrophysics Data System (ADS)

    Zingsem, Norbert; Ahrend, Florian; Vock, Silvia; Gottlob, Daniel; Krug, Ingo; Doganay, Hatice; Holzinger, Dennis; Neu, Volker; Ehresmann, Arno

    2017-12-01

    The 3D stray field landscape above an exchange bias layer system with engineered domain walls has been fully characterized by quantitative magnetic force microscopy (qMFM) measurements. This method is based on a complete quantification of the MFM tip’s imaging properties and the subtraction of its contribution from the measured MFM data by deconvolution in Fourier space. The magnetically patterned Ir17Mn83/Co70Fe30-exchange-bias-multilayers have been designed to contain asymmetric head-to-head (hh)/tail-to-tail (tt) Néel walls between domains of different magnetic anisotropies for potential use in guided particle transport. In the current application, qMFM reveals the effective magnetic charge profile on the surface of the sample—with high spatial resolution and in an absolute quantitative manner. These data enable to calculate the magnetostatic potential and the full stray field landscape above the sample surface. It has been successfully tested against: (i) micromagnetic simulations of the magnetization structure of a comparable exchange-bias layer system, (ii) measurements of the magnetization profile across the domain boundary with x-ray photoemission electron microscopy, and (iii) direct stray field measurements obtained by scanning Hall probe microscopy at elevated scan heights. This approach results in a quantitative determination of the stray field landscape at close distances to the sample surface, which will be of importance for remote magnetic particle transport applications in lab-on-a-chip devices. Furthermore, the highly resolving and quantitative MFM approach reveals details of the domain transition across the artificially structured phase boundary, which have to be attributed to a continuous change in the materials parameters across this boundary, rather than an abrupt one.

  6. Turbulent Helicity in the Atmospheric Boundary Layer

    NASA Astrophysics Data System (ADS)

    Chkhetiani, Otto G.; Kurgansky, Michael V.; Vazaeva, Natalia V.

    2018-05-01

    We consider the assumption postulated by Deusebio and Lindborg (J Fluid Mech 755:654-671, 2014) that the helicity injected into the Ekman boundary layer undergoes a cascade, with preservation of its sign (right- or alternatively left-handedness), which is a signature of the system rotation, from large to small scales, down to the Kolmogorov microscale of turbulence. At the same time, recent direct field measurements of turbulent helicity in the steppe region of southern Russia near Tsimlyansk Reservoir show the opposite sign of helicity from that expected. A possible explanation for this phenomenon may be the joint action of different scales of atmospheric flows within the boundary layer, including the sea-breeze circulation over the test site. In this regard, we consider a superposition of the classic Ekman spiral solution and Prandtl's jet-like slope-wind profile to describe the planetary boundary-layer wind structure. The latter solution mimics a hydrostatic shallow breeze circulation over a non-uniformly heated surface. A 180°-wide sector on the hodograph plane exists, within which the relative orientation of the Ekman and Prandtl velocity profiles favours the left rotation with height of the resulting wind velocity vector in the lowermost part of the boundary layer. This explains the negative (left-handed) helicity cascade toward small-scale turbulent motions, which agrees with the direct field measurements of turbulent helicity in Tsimlyansk. A simple turbulent relaxation model is proposed that explains the measured positive values of the relatively minor contribution to turbulent helicity from the vertical components of velocity and vorticity.

  7. Three dimensional boundary displacement due to stable ideal kink modes excited by external n = 2 magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Willensdorfer, M.; Strumberger, E.; Suttrop, W.; Dunne, M.; Fischer, R.; Birkenmeier, G.; Brida, D.; Cavedon, M.; Denk, S. S.; Igochine, V.; Giannone, L.; Kirk, A.; Kirschner, J.; Medvedeva, A.; Odstrčil, T.; Ryan, D. A.; The ASDEX Upgrade Team; The EUROfusion MST1 Team

    2017-11-01

    In low-collisionality (ν\\star) scenarios exhibiting mitigation of edge localized mode (ELMs), stable ideal kink modes at the edge are excited by externally applied magnetic perturbation (MP)-fields. In ASDEX Upgrade these modes can cause three-dimensional (3D) boundary displacements up to the centimeter range. These displacements have been measured using toroidally localized high resolution diagnostics and rigidly rotating n=2 MP-fields with various applied poloidal mode spectra. These measurements are compared to non-linear 3D ideal magnetohydrodynamics (MHD) equilibria calculated by VMEC. Comprehensive comparisons have been conducted, which consider for instance plasma movements due to the position control system, attenuation due to internal conductors and changes in the edge pressure profiles. VMEC accurately reproduces the amplitude of the displacement and its dependencies on the applied poloidal mode spectra. Quantitative agreement is found around the low field side (LFS) midplane. The response at the plasma top is qualitatively compared. The measured and predicted displacements at the plasma top maximize when the applied spectra is optimized for ELM-mitigation. The predictions from the vacuum modeling generally fails to describe the displacement at the LFS midplane as well as at the plasma top. When the applied mode spectra is set to maximize the displacement, VMEC and the measurements clearly surpass the predictions from the vacuum modeling by a factor of four. Minor disagreements between VMEC and the measurements are discussed. This study underlines the importance of the stable ideal kink modes at the edge for the 3D boundary displacement in scenarios relevant for ELM-mitigation.

  8. Multi-region relaxed magnetohydrodynamics in plasmas with slowly changing boundaries -- Resonant response of a plasma slab

    DOE PAGES

    Dewar, R. L.; Hudson, S. R.; Bhattacharjee, A.; ...

    2017-04-03

    The adiabatic limit of a recently proposed dynamical extension of Taylor relaxation, multi-region relaxed magnetohydrodynamics (MRxMHD), is summarized, with special attention to the appropriate definition of a relative magnetic helicity. The formalism is illustrated using a simple two-region, sheared-magnetic-field model similar to the Hahm-Kulsrud-Taylor (HKT) rippled-boundary slab model. In MRxMHD, a linear Grad-Shafranov equation applies, even at finite ripple amplitude. The adiabatic switching on of boundary ripple excites a shielding current sheet opposing reconnection at a resonant surface. The perturbed magnetic field as a function of ripple amplitude is calculated by invoking the conservation of magnetic helicity in the twomore » regions separated by the current sheet. Here, at low ripple amplitude, "half islands" appear on each side of the current sheet, locking the rotational transform at the resonant value. Beyond a critical amplitude, these islands disappear and the rotational transform develops a discontinuity across the current sheet. Published by AIP Publishing.« less

  9. Multi-region relaxed magnetohydrodynamics in plasmas with slowly changing boundaries -- Resonant response of a plasma slab

    SciTech Connect

    Dewar, R. L.; Hudson, S. R.; Bhattacharjee, A.

    The adiabatic limit of a recently proposed dynamical extension of Taylor relaxation, multi-region relaxed magnetohydrodynamics (MRxMHD), is summarized, with special attention to the appropriate definition of a relative magnetic helicity. The formalism is illustrated using a simple two-region, sheared-magnetic-field model similar to the Hahm-Kulsrud-Taylor (HKT) rippled-boundary slab model. In MRxMHD, a linear Grad-Shafranov equation applies, even at finite ripple amplitude. The adiabatic switching on of boundary ripple excites a shielding current sheet opposing reconnection at a resonant surface. The perturbed magnetic field as a function of ripple amplitude is calculated by invoking the conservation of magnetic helicity in the twomore » regions separated by the current sheet. Here, at low ripple amplitude, "half islands" appear on each side of the current sheet, locking the rotational transform at the resonant value. Beyond a critical amplitude, these islands disappear and the rotational transform develops a discontinuity across the current sheet. Published by AIP Publishing.« less

  10. Paleomagnetic and AMS studies of the El Castillo ignimbrite, central-east Mexico: Source and rock magnetic nature

    NASA Astrophysics Data System (ADS)

    Alva-Valdivia, L. M.; Agarwal, A.; Caballero-Miranda, C.; García-Amador, B. I.; Morales-Barrera, W.; Rodríguez-Elizarraráz, S.; Rodríguez-Trejo, A.

    2017-04-01

    Lithological, petromagnetic, paleomagnetic and magnetic fabric studies are employed to determine the flow direction and the location of the source of the, 2.44 to 2.21 Ma, El Castillo ignimbrite in the central-east Mexico. Based on the increasing matrix to pumice ratio and decreasing pumice size, the ignimbrite field is divided into the northwestern, central and south-southeastern sectors. Lithological comparisons among the three sectors reveal that the ignimbrite had flowed from NW to SE, and the source is in the NW part of the study area. Thermomagnetic results concur with the increasing matrix proportions from the proximal to the distal sector. The coercivity and magnetization ratios of the hysteresis parameters are lower in the SE sector than in the NW and central sectors. The dominant flow direction inferred through magnetic fabrics, at most sites, is NW to SE, which coincides with the direction inferred from lithological comparisons. However, at some sites magnetic fabrics demonstrate flow towards ENE or other various directions. The paleomagnetic analysis and field observations reveal that these anomalous directions are a consequence of anticlockwise block rotation and tilting due to normal and lateral faulting in the region.

  11. Constructing Integrable Full-pressure Full-current Free-boundary Stellarator Magnetohydrodynamic Equilibria

    NASA Astrophysics Data System (ADS)

    Hudson, S. R.; Monticello, D. A.; Reiman, A. H.; Strickler, D. J.; Hirshman, S. P.

    2003-06-01

    For the (non-axisymmetric) stellarator class of plasma confinement devices to be feasible candidates for fusion power stations it is essential that, to a good approximation, the magnetic field lines lie on nested flux surfaces; however, the inherent lack of a continuous symmetry implies that magnetic islands are guaranteed to exist. Magnetic islands break the smooth topology of nested flux surfaces and chaotic field lines result when magnetic islands overlap. An analogous case occurs with 11/2-dimension Hamiltonian systems where resonant perturbations cause singularities in the transformation to action-angle coordinates and destroy integrability. The suppression of magnetic islands is a critical issue for stellarator design, particularly for small aspect ratio devices. Techniques for `healing' vacuum fields and fixed-boundary plasma equilibria have been developed, but what is ultimately required is a procedure for designing stellarators such that the self-consistent plasma equilibrium currents and the coil currents combine to produce an integrable magnetic field, and such a procedure is presented here for the first time. Magnetic islands in free-boundary full-pressure full-current stellarator magnetohydrodynamic equilibria are suppressed using a procedure based on the Princeton Iterative Equilibrium Solver [A.H.Reiman & H.S.Greenside, Comp. Phys. Comm., 43:157, 1986.] which iterates the equilibrium equations to obtain the plasma equilibrium. At each iteration, changes to a Fourier representation of the coil geometry are made to cancel resonant fields produced by the plasma. As the iterations continue, the coil geometry and the plasma simultaneously converge to an equilibrium in which the island content is negligible. The method is applied to a candidate plasma and coil design for the National Compact Stellarator eXperiment [G.H.Neilson et.al., Phys. Plas., 7:1911, 2000.].

  12. Boundary displacement measurements using multi-energy soft x-rays

    SciTech Connect

    Tritz, K., E-mail: ktritz@pppl.gov; Stutman, D.; Diallo, A.

    The Multi-Energy Soft X-ray (ME-SXR) system on NSTX provides radial profiles of soft X-ray emission, measured through a set of filters with varying thickness, which have been used to reconstruct the electron temperature on fast time scales (∼10 kHz). In addition to this functionality, here we show that the ME-SXR system can be used to measure the boundary displacement of the NSTX plasma with a few mm spatial resolution during magnetohydrodyamic (MHD) activity. Boundary displacement measurements can serve to inform theoretical predictions of neoclassical toroidal viscosity, and will be used to investigate other edge phenomena on NSTX-U. For example, boundary measurementsmore » using filtered SXR measurements can provide information on pedestal steepness and dynamic evolution leading up to and during edge localized modes (ELMs). Future applications include an assessment of a simplified, filtered SXR edge detection system as well as its suitability for real-time non-magnetic boundary feedback for ELMs, MHD, and equilibrium position control.« less

  13. Surface-structure-controlled sectoral zoning of the rare earth elements in fluorite from Long Lake, New York, and Bingham, New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Bosze, Stephanie; Rakovan, John

    2002-03-01

    The concentration and distribution of rare earth elements (REE) in sectorally zoned fluorite crystals from Long Lake, New York, and the Hansonburg Mining District, Bingham, New Mexico, have been studied using cathodoluminescence and synchrotron X-ray fluorescence microanalysis (SXRFMA). In cubo-octahedral samples from Long Lake, New York, Ce, Nd, Gd, Dy, Ho, Er, and Tm are preferentially partitioned into the |111| sector relative to the |100| sector. Partition coefficients (K d = concentration in |111| sector/concentration in |100| sector) range between 3.5 for Ce, to 1.4 for Tm, with a general decrease in K d as elements deviated from the ionic radius of Ca 2+, for which REE substitute in fluorite. Diffusion of the REE has occurred, as evidenced by gradual changes in composition over distances of 0.2 to 0.3 mm at sector boundaries. In Bingham samples, three different partition coefficients were determined for Dy: K d|100|/|111| = 2.83, K d |100|/|110| = 1.77, and K d |110|/|111| = 1.60. These are mean K d values for a 95% confidence interval. In another sample from the same deposit, Dy, Er, and Gd were found to be preferentially incorporated into the |100| sector relative to the |210| sector with average K d |100|/|210| of 3.1, 2.4, and 2.9, respectively. In a third sample, Nd was found to be preferentially incorporated into the |110| sector relative to the |321| sector with an average K d |110|/|321| value of 2.3. Compositional heterogeneities in a given sector (concentric zoning) have been resolved using SXRFMA but are significantly less than the concentration difference across sector boundaries. Often fluorite exists in a wide variety of morphologies, as is the case in the Hansonburg Mining District of Bingham. We suggest caution when using the REE as petrogenetic indicators because fluorite trace element chemistry can vary greatly among crystals within a deposit depending on the internal morphology of a particular crystal.

  14. Magnetic Helicity and Planetary Dynamos

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    2012-01-01

    A model planetary dynamo based on the Boussinesq approximation along with homogeneous boundary conditions is considered. A statistical theory describing a large-scale MHD dynamo is found, in which magnetic helicity is the critical parameter

  15. A global MHD simulation study of the vortices at the magnetosphere boundary under the southward IMF condition

    NASA Astrophysics Data System (ADS)

    Park, K.; Ogino, T.; Lee, D.; Walker, R. J.; Kim, K.

    2013-12-01

    One of the significant problems in magnetospheric physics concerns the nature and properties of the processes which occur at the magnetopause boundary; in particular how energy, momentum, and plasma the magnetosphere receives from the solar wind. Basic processes are magnetic reconnection [Dungey, 1961] and viscouslike interaction, such as Kelvin-Helmholtz instability [Dungey 1955, Miura, 1984] and pressure-pulse driven [Sibeck et al. 1989]. In generally, magnetic reconnection occurs efficiently when the IMF is southward and the rate is largest where the magnetosheath magnetic field is antiparallel to the geomagnetic field. [Sonnerup, 1974; Crooker, 1979; Luhmann et al., 1984; Park et al., 2006, 2009]. The Kelvin-Helmholtz instability is driven by the velocity shear at the boundary, which occur frequently when the IMF is northward. Also variation of the magnetic field and the plasma properties is reported to be quasi-periodic with 2-3min [Otto and Fairfield, 2000] and period of vortex train with 3 to 4 minutes by global MHD simulation [Ogino, 2011]. The pressure-pulse is driven by the solar wind. And the observations of the magnetospheric magnetic field response show quasi-periodic with a period of 8 minutes [Sibeck et al., 1989; Kivelson and Chen, 1995]. There have been few studies of the vortices in the magnetospheric boundary under southward IMF condition. However it is not easy to find the generation mechanism and characteristic for vortices in complicated 3-dimensional space. Thus we have performed global MHD simulation for the steady solar wind and southward IMF conditions. From the simulation results, we find that the vortex occurs at R= 11.7Re (IMF Bz = -2 nT) and R= 10.2Re (IMF Bz = -10 nT) in the dayside magnetopause boundary. Also the vortex rotates counterclockwise in duskside magnetopause (clockwise in dawnside) and propagates tailward. Across the vortex, magnetic field and plasma properties clearly show quasi-periodic fluctuations with a period of 8

  16. Influence of annealing temperature on the Dy diffusion process in NdFeB magnets

    NASA Astrophysics Data System (ADS)

    Hu, Sheng-qing; Peng, Kun; Chen, Hong

    2017-03-01

    Sintered NdFeB magnets were coated with a layer of Dy metal using electron beam evaporation method and then annealed at various temperatures to investigate the temperature dependence of Dy diffusion process in NdFeB magnets. A Dy-rich phase was observed along the grain boundaries after the grain boundary diffusion process, the diffusion coefficients of various temperatures were obtained, the diffusion coefficients of Dy along the grain boundaries at 800 °C and 900 °C were determined to be 9.8×10-8 cm2 s-1 and 2.4×10-7 cm2 s-1, respectively. The diffusion length depended on the annealing temperature and the maximum diffusion length of approximately 1.8 mm and 3.0 mm can be obtained after annealing at 800 °C and 900 °C for 8 h. Higher diffusion temperature results in the diffusion not only along the grain boundaries but also into grains and then decrease in magnetic properties. The optimum annealing conditions can be determined as 900 °C for 8 h. The coercivity was improved from 1040 kA/m to 1450 kA/m and its magnetization has no significant reduction after the grain boundary diffusion process at the optimum annealing conditions.

  17. An MHD simulation model of time-dependent global solar corona with temporally varying solar-surface magnetic field maps

    NASA Astrophysics Data System (ADS)

    Hayashi, K.

    2013-11-01

    We present a model of a time-dependent three-dimensional magnetohydrodynamics simulation of the sub-Alfvenic solar corona and super-Alfvenic solar wind with temporally varying solar-surface boundary magnetic field data. To (i) accommodate observational data with a somewhat arbitrarily evolving solar photospheric magnetic field as the boundary value and (ii) keep the divergence-free condition, we developed a boundary model, here named Confined Differential Potential Field model, that calculates the horizontal components of the magnetic field, from changes in the vertical component, as a potential field confined in a thin shell. The projected normal characteristic method robustly simulates the solar corona and solar wind, in response to the temporal variation of the boundary Br. We conduct test MHD simulations for two periods, from Carrington Rotation number 2009 to 2010 and from Carrington Rotation 2074 to 2075 at solar maximum and minimum of Cycle 23, respectively. We obtained several coronal features that a fixed boundary condition cannot yield, such as twisted magnetic field lines at the lower corona and the transition from an open-field coronal hole to a closed-field streamer. We also obtained slight improvements of the interplanetary magnetic field, including the latitudinal component, at Earth.

  18. Onset of oscillatory Rayleigh-Bénard magnetoconvection with rigid horizontal boundaries

    NASA Astrophysics Data System (ADS)

    Mondal, Hiya; Das, Alaka; Kumar, Krishna

    2018-01-01

    We present the results of linear stability analysis of oscillatory Rayleigh-Bénard magnetoconvection with rigid and thermally conducting boundaries. We have investigated two types of horizontal surfaces: (i) electrically conducting and (ii) boundaries which do not allow any outward current normal to the surface (magnetic vacuum conditions). For the case of electrically conducting boundaries, the critical Rayleigh number R ao(Q ,P r ,P m ) , the critical wave number ko(Q ,P r ,P m ) , and the frequency at the instability onset ω(Q ,P r ,P m ) increase as the Chandrasekhar number Q is raised for fixed non-zero values of thermal Prandtl Pr and magnetic Prandtl number Pm. For small values of Pr, the frequency of oscillation ω at the primary instability shows a rapid increase with Pm for very small values of Pm followed by a decrease at relatively larger values of Pm. In the limit of P r →0 , Rao and ko are found to be independent of Q. However, the frequency ω increases with Q, but decreases with Pm in this limit. The oscillatory instability is possible at the onset of magnetoconvection if and only if Chandrasekhar's criterion is valid (i.e., Pm > Pr) and Q is raised above a critical value Qc(P r ,P m ) such that the product P m *Qc≈91 for large Pm. For the stellar interior of an astrophysical body ( P m ≈10-4 and P r ≈10-8 ), the value of this product P m *Qc≈230 . The boundary conditions for magnetic vacuum change the critical values of Rayleigh number, wave number, and frequency of oscillation at the onset. The oscillatory magnetoconvection occurs in this case, if Q >Qc , where P m *Qc≈42 for large Pm. For steller interior, this value is approximately 64. A low-dimensional model is also constructed to study various patterns near the onset of oscillatory convection for rigid, thermally and electrically conducting boundaries. The model shows standing and drifting fluid patterns in addition to flow reversal close to the onset of magnetoconvection.

  19. The Ionospheric Impact of an ICME-Driven Sheath Region Over Indian and American Sectors in the Absence of a Typical Geomagnetic Storm

    NASA Astrophysics Data System (ADS)

    Rout, Diptiranjan; Chakrabarty, D.; Sarkhel, S.; Sekar, R.; Fejer, B. G.; Reeves, G. D.; Kulkarni, Atul S.; Aponte, Nestor; Sulzer, Mike; Mathews, John D.; Kerr, Robert B.; Noto, John

    2018-05-01

    On 13 April 2013, the ACE spacecraft detected arrival of an interplanetary shock at 2250 UT, which is followed by the passage of the sheath region of an interplanetary coronal mass ejection (ICME) for a prolonged (18-hr) period. The polarity of interplanetary magnetic field Bz was northward inside the magnetic cloud region of the ICME. The ring current (SYM-H) index did not go below -7 nT during this event suggesting the absence of a typical geomagnetic storm. The responses of the global ionospheric electric field associated with the passage of the ICME sheath region have been investigated using incoherent scatter radar measurements of Jicamarca and Arecibo (postmidnight sector) along with the variations of equatorial electrojet strength over India (day sector). It is found that westward and eastward prompt penetration (PP) electric fields affected ionosphere over Jicamarca/Arecibo and Indian sectors, respectively, during 0545-0800 UT. The polarities of the PP electric field perturbations over the day/night sectors are consistent with model predictions. In fact, DP2-type electric field perturbations with ˜40-min periodicity are found to affect the ionosphere over both the sectors for about 2.25 hr during the passage of the ICME sheath region. This result shows that SYM-H index may not capture the full geoeffectivenss of the ICME sheath-driven storms and suggests that the PP electric field perturbations should be evaluated for geoeffectiveness of ICME when the polarity of interplanetary magnetic field Bz is northward inside the magnetic cloud region of the ICME.

  20. Mariner 10 magnetic field observations of the Venus wake

    NASA Technical Reports Server (NTRS)

    Lepping, R. P.; Behannon, K. W.

    1977-01-01

    Magnetic field measurements made over a 21-hour interval during the Mariner 10 encounter with Venus were used to study the down-stream region of the solar wind-Venus interaction over a distance of approximately 100 R sub v. For most of the day before closest approach the spacecraft was located in a sheath-like region which was apparently bounded by planetary bow shock on the outer side and either a planetary wake boundary or transient boundary-like feature on the inner side. The spacecraft made multiple encounters with the wake-like boundary during the 21-hour interval with an increasing frequency as it approached the planet. Each pass into the wake boundary from the sheath region was consistently characterized by a slight decrease in magnetic field magnitude, a marked increase in the frequency and amplitude of field fluctuations, and a systematic clockwise rotation of the field direction when viewed from above the plane of the planet orbit.

  1. Correlation of Magnetic Fields with Solar Wind Plasma Parameters at 1AU

    NASA Astrophysics Data System (ADS)

    Shen, F.

    2017-12-01

    The physical parameters of the solar wind observed in-situ near 1AU have been studied for several decades, and relationships between them, such as the positive correlation between the solar wind plasma temperature T and velocity V, and the negative correlation between density N and velocity V, are well known. However, the magnetic field intensity does not appear to be well correlated with any individual plasma parameter. In this paper, we discuss previously under-reported correlations between B and the combined plasma parameters √NV2 as well as between B and √NT. These two correlations are strong during the periods of corotating interaction regions and high speed streams, moderate during intervals of slow solar wind, and rather poor during the passage of interplanetary coronal mass ejections. The results indicate that the magnetic pressure in the solar wind is well correlated both with the plasma dynamic pressure and the thermal pressure. Then, we employ a 3D MHD model to simulate the formation of the relationships between the magnetic strength B and √NV2 as well as √NT observed at 1AU. The inner boundary condition is derived by empirical models, with the magnetic field and density are optional. Five kinds of boundary conditions at the inner boundary of heliosphere are tested. In the cases that the magnetic field is related to speed at the inner boundary, the correlation coefficients between B and √NV2 as well as between B and √NT are even higher than that in the observational results. At 1AU the simulated radial magnetic field shows little latitude dependence, which matches the observation of Ulysses. Most of the modeled characters in these cases are closer to observation than others. This inner boundary condition may more accurately characterize Sun's magnetic influence on the heliosphere. The new input may be able to improve the simulation of CME propagation in the inner heliosphere and the space weather forecasting.

  2. Subsidence of Ionospheric Flows Triggered by Magnetotail Magnetic Reconnection During Transpolar Arc Brightening

    NASA Astrophysics Data System (ADS)

    Nowada, Motoharu; Fear, Robert C.; Grocott, Adrian; Shi, Quan-Qi; Yang, Jun; Zong, Qiu-Gang; Wei, Yong; Fu, Sui-Yan; Pu, Zu-Yin; Mailyan, Bagrat; Zhang, Hui

    2018-05-01

    A transpolar arc (TPA), which extended from postmidnight to prenoon, was seen on 16 September 2001 in the Northern Hemisphere under northward interplanetary magnetic field (IMF)-Bz and weakly dawnward IMF-By conditions. Super Dual Auroral Radar Network detected significant westward plasma flows just equatorward of the poleward edge of the midnight sector auroral oval. These plasma flows were confined to closed field lines and are identified as the ionospheric plasma flow signature of tail reconnection during IMF northward nonsubstorm intervals (TRINNIs). These TRINNI flows persisted for 53 min from prior to the TPA appearance to the cessation of TPA growth. They are usually observed before (and during) intervals when TPAs are present, but in this case, subsided after the TPA was completely connected to the dayside. Additional slower flows across the open/closed polar cap boundary were seen at the TPA onset time in the same magnetic local time sector as the nightside end of the TPA. These ionospheric flows suggest that magnetotail reconnection significantly contributed to the TPA formation, as proposed by Milan et al., https://doi.org/10.1029/2004JA010835). We propose a possible scenario for an absence of the TRINNI flows during the TPA brightening by considering the relation between the extent of the magnetotail reconnection line mapped onto nightside auroral oval and the TPA width; TRINNI flows would subside when the extent of X-line is comparable to the TPA width. Therefore, our results suggest that the fate (absence or presence) of TRINNI flows on closed field lines during the TPA formation would be closely related with magnetotail reconnection extent.

  3. Study of the magnetic interaction in nanocrystalline Pr-Fe-Co-Nb-B permanent magnets

    NASA Astrophysics Data System (ADS)

    Dospial, M.; Plusa, D.; Ślusarek, B.

    2012-03-01

    The magnetic properties of an isotropic, epoxy resin bonded magnets made from Pr-Fe-Co-Nb-B powder were investigated. The magnetization reversal process and magnetic parameters were examined by measurements of the initial magnetization curve, major and minor hysteresis loops and sets of recoil curves. From the initial magnetization curve and the field dependencies of the reversible and irreversible magnetization components derived from the recoil loops it was found that the magnetization reversal process is the combination of the nucleation of reversed domains and pinning of domain walls at the grain boundaries and the reversible rotation of magnetization vector in single domain grains. The interactions between grains were studied by means of δM plots. The nonlinear behavior of δM curve approve that the short range intergrain exchange coupling interactions are dominant in a field up to the sample coercivity. The interaction domains and fine magnetic structure were revealed as the evidence of exchange coupling between soft α-Fe and hard magnetic Nd2Fe14B grains.

  4. Magnetic subdomains of the High Arctic Magnetic High - Speculations and implications for understanding of the High Arctic Large Igneous Province and related tectonics.

    NASA Astrophysics Data System (ADS)

    Saltus, R. W.; Oakey, G. N.

    2015-12-01

    The crustal magnetic anomaly pattern for the high Arctic is dominated by a 1.3 x 106 km2 roughly oval domain of magnetic high, the High Arctic Magnetic High (HAMH) that includes numerous linear and curvi-linear shorter wavelength magnetic highs and lows with no single overall trend. Previous workers (including us) have associated this magnetic domain with the intrusive and extrusive mafic rocks of the High Arctic Large Igneous Province (HALIP). The HAMH shows the HALIP to be roughly the same size as other more well-known LIPs such as the Deccan Traps. The broad crustal magnetic character of LIPs is similar (and distinctive from non-LIP regions) worldwide. We identify 5 general subdomains and further distinguish 2 or 3 sections within each subdomain. We examine matched filter magnetic anomaly depth slices and the bathymetric and gravimetric expression of each sub-domain. Subdomains I and II associated respectively with the Mendeleev and Alpha Ridges have the deepest crustal roots. Subdomain III spans most of the central HAMH between I and II and has a distinctly less magnetic core. Subdomain IV on the Canadian margin side appears transitional to the relatively non-magnetic deep Canada Basin. Subdomain V is a zone of parallel magnetic highs at 90 degrees to the trend of the adjacent Lomonosov Ridge. Subdomains I and II may represent the deep cores of two smaller mantle plume heads that contributed to the overall HALIP. The presence of two plumes might serve to explain the two separate clusters of age dates (80 - 90 Ma and 120 - 130 Ma) found on igneous rocks surrounding and dredged from the HALIP region, and two stratigraphic sequence boundaries and extinction events associated with those time ranges. The boundaries between the magnetic subdomains might coincide with tectonic zones related to the post-LIP complex tectonic history of the Amerasian basin. A linear, through-going boundary that bisects the HAMH and runs perpendicular to the trend of the Lomonosov ridge

  5. The growth of the tearing mode - Boundary and scaling effects

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.; Van Hoven, G.

    1983-01-01

    A numerical model of resistive magnetic tearing is developed in order to verify and relate the results of the principal approximations used in analytic analyses and to investigate the solutions and their growth-rate scalings over a large range of primary parameters which include parametric values applicable to the solar atmosphere. The computations cover the linear behavior for a variety of boundary conditions, emphasizing effects which differentiate magnetic tearing in astrophysical situations from that in laboratory devices. Eigenfunction profiles for long and short wavelengths are computed and the applicability of the 'constant psi' approximation is investigated. The growth rate is computed for values of the magnetic Reynolds number up to a trillion and of the dimensionless wavelength parameter down to 0.001. The analysis predicts significant effects due to differing values of the magnetic Reynolds number.

  6. Reconnection Scaling Experiment (RSX): Magnetic Reconnection in Linear Geometry

    NASA Astrophysics Data System (ADS)

    Intrator, T.; Sovinec, C.; Begay, D.; Wurden, G.; Furno, I.; Werley, C.; Fisher, M.; Vermare, L.; Fienup, W.

    2001-10-01

    The linear Reconnection Scaling Experiment (RSX) at LANL is a qualitatively different way of creating MHD relevant plasmas to look at the physics of magnetic reconnection. We show here an overview of the experiment and initial electrostatic and magnetic probe data. Plasma creation using plasma guns is independent of equilibrium or force balance, so we can scale many relevant parameters. As the magnetic reconnection region between two parallel current channels sweeps down a long plasma column we can generate 3D movies of magnetic reconnection from many repetitive shots. If two current channels were to move because of kink instabilities instead of mutual J x B forces and reconnection effects, each shot would less reproducible. Our data show the kink stability boundary for a single current channel. We compare this with MHD 2 fluid NIMROD simulations of the single current channel kink stability boundary for a variety of experimental conditions.

  7. Fabrication and Test of an Optical Magnetic Mirror

    NASA Technical Reports Server (NTRS)

    Hagopian, John G.; Roman, Patrick A.; Shiri, Shahram; Wollack, Edward J.; Roy, Madhumita

    2011-01-01

    Traditional mirrors at optical wavelengths use thin metalized or dielectric layers of uniform thickness to approximate a perfect electric field boundary condition. The electron gas in such a mirror configuration oscillates in response to the incident photons and subsequently re-emits fields where the propagation and electric field vectors have been inverted and the phase of the incident magnetic field is preserved. We proposed fabrication of sub-wavelength-scale conductive structures that could be used to interact with light at a nano-scale and enable synthesis of the desired perfect magnetic-field boundary condition. In a magnetic mirror, the interaction of light with the nanowires, dielectric layer and ground plate, inverts the magnetic field vector resulting in a zero degree phase shift upon reflection. Geometries such as split ring resonators and sinusoidal conductive strips were shown to demonstrate magnetic mirror behavior in the microwave and then in the visible. Work to design, fabricate and test a magnetic mirror began in 2007 at the NASA Goddard Space Flight Center (GSFC) under an Internal Research and Development (IRAD) award Our initial nanowire geometry was sinusoidal but orthogonally asymmetric in spatial frequency, which allowed clear indications of its behavior by polarization. We report on the fabrication steps and testing of magnetic mirrors using a phase shifting interferometer and the first far-field imaging of an optical magnetic mirror.

  8. The Impact of Geometrical Constraints on Collisionless Magnetic Reconnection

    NASA Technical Reports Server (NTRS)

    Hesse, Michael; Aunai, Nico; Kuznetsova, Masha; Frolov, Rebekah; Black, Carrrie

    2012-01-01

    One of the most often cited features associated with collisionless magnetic reconnection is a Hall-type magnetic field, which leads, in antiparallel geometries, to a quadrupolar magnetic field signature. The combination of this out of plane magnetic field with the reconnection in-plane magnetic field leads to angling of magnetic flux tubes out of the plane defined by the incoming magnetic flux. Because it is propagated by Whistler waves, the quadrupolar field can extend over large distances in relatively short amounts of time - in fact, it will extend to the boundary of any modeling domain. In reality, however, the surrounding plasma and magnetic field geometry, defined, for example, by the overall solar wind flow, will in practice limit the extend over which a flux tube can be angled out of the main plain. This poses the question to what extent geometric constraints limit or control the reconnection process and this is the question investigated in this presentation. The investigation will involve a comparison of calculations, where open boundary conditions are set up to mimic either free or constrained geometries. We will compare momentum transport, the geometry of the reconnection regions, and the acceleration if ions and electrons to provide the current sheet in the outflow jet.

  9. Effect of grain-boundary flux pinning in MgB 2 with columnar structure

    NASA Astrophysics Data System (ADS)

    Kim, D. H.; Hwang, T. J.; Cha, Y. J.; Seong, W. K.; Kang, W. N.

    2009-10-01

    We studied the flux pinning properties by grain boundaries in MgB 2 films prepared by using a hybrid physical chemical vapor deposition method on the c-axis oriented sapphire substrates. All the films we report here had the columnar grains with the growth direction perpendicular to the substrates and the grain sizes in the range of a few hundred nanometers. At very low magnetic fields, no discernable grain-boundary (GB) pinning effect was observed in all measuring temperatures, but above those fields, the effect of GB flux pinning was observed as enhanced critical current densities ( Jcs) and reduced resistances when an external magnetic field ( B) was aligned parallel to the c-axis. We interpret the B dependence of Jc in the terms of flux line lattice shear inside the columnar grains activated by dislocations of Frank-Read source while the flux lines pinned by GB act as anchors for dislocations. Magnetic field dependence of flux pinning force density for B parallel to the c-axis was reasonably explained by the above model.

  10. Magnetic properties of the surface layer and its magnetic interaction with the interior of Nd-Fe-B sintered magnets

    NASA Astrophysics Data System (ADS)

    Kobayashi, Kurima; Nakamura, Michi-hide; Urushibata, Kimiko

    2015-05-01

    The magnetization and demagnetization mechanisms in the mechanically polished surface layers (SL) of the c-plane and a-b plane of Nd-Fe-B sintered magnets were investigated. The magnetic interaction between the SL and the interior of the magnet was clarified by using vibrating sample magnetometer measurements of a whole sample and magneto-force microscopy observations of the domain structure of the SL layer. The polishing eliminated the Nd-rich grain boundary phases, which was only about 2 nm thick, from the SL crystal grains in the sintered magnets. The a-b plane polishing caused the independent magnetic reversal of the a-b plane SL, which was about 5.5 μm thick, as in the platy samples. The coercivities (μ0Hc) of the SL were less than 0.3 T. In contrast, the c-plane polishing did not produce independent magnetic reversal of the SL, although the coercivity of bulk samples was clearly decreased by the formation of the c-plane SL. The grains in the SL should form clusters that alter the demagnetizing factors, depending on the shape of cluster as a magnetic unit. The magnetic interaction among the SL crystal grains is expected to play an important role in the coercivity mechanism of Nd-Fe-B sintered magnets.

  11. A high magnetic Reynolds number dynamo

    NASA Technical Reports Server (NTRS)

    Perkins, F. W.; Zweibel, E. G.

    1987-01-01

    A boundary-layer solution to a high magnetic Reynolds number R periodic dynamo model shows that: (1) flux expulsion forces the magnetic field into flux sheets; (2) the principal contribution to the alpha effect arises from regions of flow stagnation along a flux sheet; and (3) the alpha effect scales as R exp-1/2. Arguments for these effects persisting in turbulent dynamos are given.

  12. Evidence of impurity and boundary effects on magnetic monopole dynamics in spin ice

    NASA Astrophysics Data System (ADS)

    Revell, H. M.; Yaraskavitch, L. R.; Mason, J. D.; Ross, K. A.; Noad, H. M. L.; Dabkowska, H. A.; Gaulin, B. D.; Henelius, P.; Kycia, J. B.

    2013-01-01

    Electrical resistance is a crucial and well-understood property of systems ranging from computer microchips to nerve impulse propagation in the human body. Here we study the motion of magnetic charges in spin ice and find that extra spins inserted in Dy2Ti2O7 trap magnetic monopole excitations and provide the first example of how defects in a spin-ice material obstruct the flow of monopoles--a magnetic version of residual resistance. We measure the time-dependent magnetic relaxation in Dy2Ti2O7 and show that it decays with a stretched exponential followed by a very slow long-time tail. In a Monte Carlo simulation governed by Metropolis dynamics we show that surface effects and a very low level of stuffed spins (0.30%)--magnetic Dy ions substituted for non-magnetic Ti ions--cause these signatures in the relaxation. In addition, we find evidence that the rapidly diverging experimental timescale is due to a temperature-dependent attempt rate proportional to the monopole density.

  13. T-duality simplifies bulk-boundary correspondence: the noncommutative case

    NASA Astrophysics Data System (ADS)

    Hannabuss, Keith C.; Mathai, Varghese; Thiang, Guo Chuan

    2018-05-01

    We state and prove a general result establishing that T-duality, or the Connes-Thom isomorphism, simplifies the bulk-boundary correspondence, given by a boundary map in K-theory, in the sense of converting it to a simple geometric restriction map. This settles in the affirmative several earlier conjectures of the authors and provides a clear geometric picture of the correspondence. In particular, our result holds in arbitrary spatial dimension, in both the real and complex cases, and also in the presence of disorder, magnetic fields, and H-flux. These special cases are relevant both to string theory and to the study of the quantum Hall effect and topological insulators with defects in condensed matter physics.

  14. Macroscopic theory of dark sector

    NASA Astrophysics Data System (ADS)

    Meierovich, Boris

    A simple Lagrangian with squared covariant divergence of a vector field as a kinetic term turned out an adequate tool for macroscopic description of the dark sector. The zero-mass field acts as the dark energy. Its energy-momentum tensor is a simple additive to the cosmological constant [1]. Space-like and time-like massive vector fields describe two different forms of dark matter. The space-like massive vector field is attractive. It is responsible for the observed plateau in galaxy rotation curves [2]. The time-like massive field displays repulsive elasticity. In balance with dark energy and ordinary matter it provides a four parametric diversity of regular solutions of the Einstein equations describing different possible cosmological and oscillating non-singular scenarios of evolution of the universe [3]. In particular, the singular big bang turns into a regular inflation-like transition from contraction to expansion with the accelerate expansion at late times. The fine-tuned Friedman-Robertson-Walker singular solution corresponds to the particular limiting case at the boundary of existence of regular oscillating solutions in the absence of vector fields. The simplicity of the general covariant expression for the energy-momentum tensor allows to analyse the main properties of the dark sector analytically and avoid unnecessary model assumptions. It opens a possibility to trace how the additional attraction of the space-like dark matter, dominating in the galaxy scale, transforms into the elastic repulsion of the time-like dark matter, dominating in the scale of the Universe. 1. B. E. Meierovich. "Vector fields in multidimensional cosmology". Phys. Rev. D 84, 064037 (2011). 2. B. E. Meierovich. "Galaxy rotation curves driven by massive vector fields: Key to the theory of the dark sector". Phys. Rev. D 87, 103510, (2013). 3. B. E. Meierovich. "Towards the theory of the evolution of the Universe". Phys. Rev. D 85, 123544 (2012).

  15. Magnetic Binary Silicide Nanostructures.

    PubMed

    Goldfarb, Ilan; Cesura, Federico; Dascalu, Matan

    2018-05-02

    In spite of numerous advantageous properties of silicides, magnetic properties are not among them. Here, the magnetic properties of epitaxial binary silicide nanostructures are discussed. The vast majority of binary transition-metal silicides lack ferromagnetic order in their bulk-size crystals. Silicides based on rare-earth metals are usually weak ferromagnets or antiferromagnets, yet both groups tend to exhibit increased magnetic ordering in low-dimensional nanostructures, in particular at low temperatures. The origin of this surprising phenomenon lies in undercoordinated atoms at the nanostructure extremities, such as 2D (surfaces/interfaces), 1D (edges), and 0D (corners) boundaries. Uncompensated superspins of edge atoms increase the nanostructure magnetic shape anisotropy to the extent where it prevails over its magnetocrystalline counterpart, thus providing a plausible route toward the design of a magnetic response from nanostructure arrays in Si-based devices, such as bit-patterned magnetic recording media and spin injectors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Subauroral polarization stream on the outer boundary of the ring current during an energetic ion injection event

    NASA Astrophysics Data System (ADS)

    Yuan, Zhigang; Qiao, Zheng; Li, Haimeng; Huang, Shiyong; Wang, Dedong; Yu, Xiongdong; Yu, Tao

    2017-04-01

    Subauroral polarization stream (SAPS) electric field can play an important role in the coupling between the inner magnetosphere and ionosphere; however, the production mechanism of SAPS has not been yet solved. During an energetic ion injection event on 26 March 2004, at latitudes lower than the equatorward boundaries of precipitating plasma sheet electrons and ions, the Defense Meteorological Satellite Program (DMSP) F13 satellite simultaneously observed a strong SAPS with the peak velocity of 1294 m/s and downward flowing field-aligned currents (FACs). Conjugate observations of DMSP F13 and NOAA 15 satellites have shown that FACs flowing into the ionosphere just lie in the outer boundary of the ring current (RC). The downward flowing FACs were observed in a region of positive latitudinal gradients of the ion energy density, implying that the downward flowing FACs are more likely linked to the azimuthal gradient than the radial gradient of the RC ion pressure. Our result demonstrates that RC ion pressure gradients on the outer boundary of the RC in the evening sector during energetic ion injection events can lead to downward flowing FACs so as to cause strong SAPS in condition of low ionospheric conductivities.Plain Language SummaryThis paper provides a good case that the SAPS and FAC occurred in the outer <span class="hlt">boundary</span> of the ring current during an energetic ion injection event. Our result demonstrates that RC ion pressure gradients on the outer <span class="hlt">boundary</span> of the RC in the evening <span class="hlt">sector</span> during energetic ion injection events can lead to downward flowing FACs so as to cause strong SAPS in condition of low ionospheric conductivities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018SuScT..31d5001S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018SuScT..31d5001S"><span>Evidence for preferential flux flow at the grain <span class="hlt">boundaries</span> of superconducting RF-quality niobium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sung, Z.-H.; Lee, P. J.; Gurevich, A.; Larbalestier, D. C.</p> <p>2018-04-01</p> <p>The question of whether grain <span class="hlt">boundaries</span> (GBs) in niobium can be responsible for lowered operating field (B RF) or quality factor (Q 0) in superconducting radio frequency (SRF) cavities is still controversial. Here, we show by direct DC transport across planar GBs isolated from a slice of very large-grain SRF-quality Nb that vortices can preferentially flow along the grain <span class="hlt">boundary</span> when the external <span class="hlt">magnetic</span> field lies in the GB plane. However, increasing the misalignment between the GB plane and the external <span class="hlt">magnetic</span> field vector markedly reduces preferential flux flow along the GB. Importantly, we find that preferential GB flux flow is more prominent for a buffered chemical polished than for an electropolished bi-crystal. The voltage-current characteristics of GBs are similar to those seen in low angle grain <span class="hlt">boundaries</span> of high temperature superconductors where there is clear evidence of suppression of the superconducting order parameter at the GB. While local weakening of superconductivity at GBs in cuprates and pnictides is intrinsic, deterioration of current transparency of GBs in Nb appears to be extrinsic, since the polishing method clearly affect the local GB degradation. The dependence of preferential GB flux flow on important cavity preparation and experimental variables, particularly the final chemical treatment and the angle between the <span class="hlt">magnetic</span> field and the GB plane, suggests two more reasons why real cavity performance can be so variable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4810604Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4810604Y"><span>A New Method for Coronal <span class="hlt">Magnetic</span> Field Reconstruction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yi, Sibaek; Choe, Gwang-Son; Cho, Kyung-Suk; Kim, Kap-Sung</p> <p>2017-08-01</p> <p>A precise way of coronal <span class="hlt">magnetic</span> field reconstruction (extrapolation) is an indispensable tool for understanding of various solar activities. A variety of reconstruction codes have been developed so far and are available to researchers nowadays, but they more or less bear this and that shortcoming. In this paper, a new efficient method for coronal <span class="hlt">magnetic</span> field reconstruction is presented. The method imposes only the normal components of <span class="hlt">magnetic</span> field and current density at the bottom <span class="hlt">boundary</span> to avoid the overspecification of the reconstruction problem, and employs vector potentials to guarantee the divergence-freeness. In our method, the normal component of current density is imposed, not by adjusting the tangential components of A, but by adjusting its normal component. This allows us to avoid a possible numerical instability that on and off arises in codes using A. In real reconstruction problems, the information for the lateral and top <span class="hlt">boundaries</span> is absent. The arbitrariness of the <span class="hlt">boundary</span> conditions imposed there as well as various preprocessing brings about the diversity of resulting solutions. We impose the source surface condition at the top <span class="hlt">boundary</span> to accommodate flux imbalance, which always shows up in magnetograms. To enhance the convergence rate, we equip our code with a gradient-method type accelerator. Our code is tested on two analytical force-free solutions. When the solution is given only at the bottom <span class="hlt">boundary</span>, our result surpasses competitors in most figures of merits devised by Schrijver et al. (2006). We have also applied our code to a real active region NOAA 11974, in which two M-class flares and a halo CME took place. The EUV observation shows a sudden appearance of an erupting loop before the first flare. Our numerical solutions show that two entwining flux tubes exist before the flare and their shackling is released after the CME with one of them opened up. We suggest that the erupting loop is created by <span class="hlt">magnetic</span> reconnection between</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19749769','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19749769"><span>Giant <span class="hlt">magnetic</span>-field-induced strains in polycrystalline Ni-Mn-Ga foams.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chmielus, M; Zhang, X X; Witherspoon, C; Dunand, D C; Müllner, P</p> <p>2009-11-01</p> <p>The <span class="hlt">magnetic</span> shape-memory alloy Ni-Mn-Ga shows, in monocrystalline form, a reversible <span class="hlt">magnetic</span>-field-induced strain (MFIS) up to 10%. This strain, which is produced by twin <span class="hlt">boundaries</span> moving solely by internal stresses generated by <span class="hlt">magnetic</span> anisotropy energy, can be used in actuators, sensors and energy-harvesting devices. Compared with monocrystalline Ni-Mn-Ga, fine-grained Ni-Mn-Ga is much easier to process but shows near-zero MFIS because twin <span class="hlt">boundary</span> motion is inhibited by constraints imposed by grain <span class="hlt">boundaries</span>. Recently, we showed that partial removal of these constraints, by introducing pores with sizes similar to grains, resulted in MFIS values of 0.12% in polycrystalline Ni-Mn-Ga foams, close to those of the best commercial magnetostrictive materials. Here, we demonstrate that introducing pores smaller than the grain size further reduces constraints and markedly increases MFIS to 2.0-8.7%. These strains, which remain stable over >200,000 cycles, are much larger than those of any polycrystalline, active material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAP...118x4104F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAP...118x4104F"><span>The effects of <span class="hlt">magnetic</span> and mechanical microstructures on the twinning stress in Ni-Mn-Ga</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Faran, Eilon; Benichou, Itamar; Givli, Sefi; Shilo, Doron</p> <p>2015-12-01</p> <p>The ferromagnetic 10M Ni-Mn-Ga alloy exhibits complex <span class="hlt">magnetic</span> and mechanical microstructures, which are expected to form barriers for motion of macro twin <span class="hlt">boundaries</span>. Here, the contributions of both microstructures to the magnitude of the twinning stress property are investigated experimentally. A series of uniaxial loading-unloading curves are taken under different orientation angles of a constant <span class="hlt">magnetic</span> field. The different 180 ° <span class="hlt">magnetic</span> domains microstructures that are formed across the twin <span class="hlt">boundary</span> in each case are visualised using a magneto optical film. Analysis of the different loading curves and the corresponding <span class="hlt">magnetic</span> microstructures show that the latter does not contribute to the barriers for twin <span class="hlt">boundary</span> motion. In accordance, the internal resisting stress for twin <span class="hlt">boundary</span> motion under any <span class="hlt">magnetic</span> field can be taken as the twinning stress measured in the absence of an external field. In addition, a statistical analysis of the fine features in the loading profiles reveals that the barrier for twinning is associated with a μ m sized characteristic length scale. This length scale corresponds to the typical thickness of micro-twinning laminates that constitute a mechanical microstructure. These findings indicate that the magnitude of the twinning stress in 10M Ni-Mn-Ga is determined by the characteristic fine twinned mechanical microstructure of this alloy.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6612886','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/biblio/6612886"><span>Thermomagnetic burn control for <span class="hlt">magnetic</span> fusion reactor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Rawls, J.M.; Peuron, A.U.</p> <p>1980-07-01</p> <p>Apparatus is provided for controlling the plasma energy production rate of a <span class="hlt">magnetic</span>-confinement fusion reactor, by controlling the <span class="hlt">magnetic</span> field ripple. The apparatus includes a group of shield <span class="hlt">sectors</span> formed of ferromagnetic material which has a temperature-dependent saturation <span class="hlt">magnetization</span>, with each shield lying between the plasma and a toroidal field coil. A mechanism for controlling the temperature of the <span class="hlt">magnetic</span> shields, as by controlling the flow of cooling water therethrough, thereby controls the saturation <span class="hlt">magnetization</span> of the shields and therefore the amount of ripple in the <span class="hlt">magnetic</span> field that confines the plasma, to thereby control the amount of heat loss from the plasma. This heat loss in turn determines the plasma state and thus the rate of energy production.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T43D2706T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T43D2706T"><span><span class="hlt">Magnetic</span> mapping of (carbonated) oceanic crust-mantle <span class="hlt">boundary</span>: New insights from Linnajavri, northern Norway</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tominaga, M.; Beinlich, A.; Tivey, M.; Andrade Lima, E.; Weiss, B. P.</p> <p>2012-12-01</p> <p>The contribution of lower oceanic crust and upper mantle to marine <span class="hlt">magnetic</span> anomalies has long been recognized, but the detailed <span class="hlt">magnetic</span> character of this non-volcanic source layer remains to be fully defined. Here, we report preliminary results of a <span class="hlt">magnetic</span> survey and source characterization of a "carbonated" oceanic Moho (petrological "Mohorovicic discontinuity") sequence observed at the Linnajavri Serpentinite Complex (LSC), northern Norway. The LSC is located at 67° 36'N and 16° 24'E within the upper Allochthon of the Norwegian Caledonides and represents a dismembered ophiolite. Particularly in the southern ("Ridoalggicohkka") area of the LSC, gabbro, serpentinite and its talc-carbonate (soapstone) and quartz-carbonate (listvenite) altered equivalents are extraordinarily well-exposed [1]. An intact oceanic Moho is exposed here, despite its complex tectonic setting. The small degree of arctic rock weathering (≤ 2 mm weathering surface) allowed for detailed regional-scale surface <span class="hlt">magnetic</span> mapping across alteration fronts (serpentinite-soapstone; soapstone-listvenite) and lithological contacts (soapstone-gabbro). <span class="hlt">Magnetic</span> mapping was conducted using a handheld 3-axis magnetometer, surface-towed resistivity meter and Teka surface <span class="hlt">magnetic</span> susceptometer with sample spacing of 1 m. Geophysical field mapping was combined with petrological observations and scanning SQUID microscopy (SM) mapping conducted on thin sections from rock samples that were drilled along the survey lines. Regional scale <span class="hlt">magnetic</span> mapping indicates that the total <span class="hlt">magnetic</span> field across both the "carbonated" Moho and the soapstone-serpentinite interfaces show higher frequency changes in their <span class="hlt">magnetic</span> anomaly character and amplitudes than the surface-towed resistivity data. SQUID microscopy mapping of both natural remanence <span class="hlt">magnetization</span> (NRM) and anhysteretic remanence <span class="hlt">magnetization</span> (ARM) on gabbro, serpentinite, soapstone, and listvenite samples, with a sensor-sample separation of ˜190 </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.3829N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.3829N"><span>Remote Sensing of the Reconnection Electric Field From In Situ Multipoint Observations of the Separatrix <span class="hlt">Boundary</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, T. K. M.; Nakamura, R.; Varsani, A.; Genestreti, K. J.; Baumjohann, W.; Liu, Y.-H.</p> <p>2018-05-01</p> <p>A remote sensing technique to infer the local reconnection electric field based on in situ multipoint spacecraft observation at the reconnection separatrix is proposed. In this technique, the increment of the reconnected <span class="hlt">magnetic</span> flux is estimated by integrating the in-plane <span class="hlt">magnetic</span> field during the sequential observation of the separatrix <span class="hlt">boundary</span> by multipoint measurements. We tested this technique by applying it to virtual observations in a two-dimensional fully kinetic particle-in-cell simulation of <span class="hlt">magnetic</span> reconnection without a guide field and confirmed that the estimated reconnection electric field indeed agrees well with the exact value computed at the X-line. We then applied this technique to an event observed by the Magnetospheric Multiscale mission when crossing an energetic plasma sheet <span class="hlt">boundary</span> layer during an intense substorm. The estimated reconnection electric field for this event is nearly 1 order of magnitude higher than a typical value of magnetotail reconnection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850016251&hterms=Knott&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3DKnott%252C%2BC','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850016251&hterms=Knott&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAuthor-Name%26N%3D0%26No%3D30%26Ntt%3DKnott%252C%2BC"><span>Electric fields in the plasma sheet and plasma sheet <span class="hlt">boundary</span> layer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pedersen, A.; Cattell, C. A.; Faelthammar, C. G.; Knott, K.; Lindqvist, P. A.; Manka, R. H.; Mozer, F. S.</p> <p>1984-01-01</p> <p>Data from the spherical double probe electric-field experiment on ISEE-1 were used to study plasmasheet/lobe <span class="hlt">boundary</span> crossings during substorms, identified by plasma measurements and by using the electric field probes as a reference for measurements of the spacecraft potential. There are strong electric fields, with a dominant dawn-to-dusk component, throughout the <span class="hlt">boundary</span> layer outside the plasmasheet for contracting and expanding motions of the plasmasheet and for different <span class="hlt">magnetic</span> field directions. Characteristic amplitudes and durations are 5 to 10 mV/m and 5 to 15 min. The corresponding E x B vectors are always towards the plasmasheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1349900-micromagnetic-simulations-periodic-boundary-conditions-hard-soft-nanocomposites','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1349900-micromagnetic-simulations-periodic-boundary-conditions-hard-soft-nanocomposites"><span>Micromagnetic simulations with periodic <span class="hlt">boundary</span> conditions: Hard-soft nanocomposites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wysocki, Aleksander L.; Antropov, Vladimir P.</p> <p>2016-12-01</p> <p>Here, we developed a micromagnetic method for modeling <span class="hlt">magnetic</span> systems with periodic <span class="hlt">boundary</span> conditions along an arbitrary number of dimensions. The main feature is an adaptation of the Ewald summation technique for evaluation of long-range dipolar interactions. The method was applied to investigate the hysteresis process in hard-soft <span class="hlt">magnetic</span> nanocomposites with various geometries. The dependence of the results on different micromagnetic parameters was studied. We found that for layered structures with an out-of-plane hard phase easy axis the hysteretic properties are very sensitive to the strength of the interlayer exchange coupling, as long as the spontaneous <span class="hlt">magnetization</span> for the hardmore » phase is significantly smaller than for the soft phase. The origin of this behavior was discussed. Additionally, we investigated the soft phase size optimizing the energy product of hard-soft nanocomposites.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880001386','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880001386"><span>Vortex/<span class="hlt">boundary</span>-layer interactions: Data report, volume 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cutler, A. D.; Bradshaw, P.</p> <p>1987-01-01</p> <p>This report summarizes the work done under NASA Grant NAGw-581, Vortex/<span class="hlt">Boundary</span> Layer Interactions. The experimental methods are discussed in detail and numerical results are presented, but are not fully interpreted. This report should be useful to anyone who wishes to make further use of the data (available on floppy disc or <span class="hlt">magnetic</span> tape) for the development of turbulence models or the validation of predictive methods. Journal papers are in course of preparation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990018405','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990018405"><span>Convection of Plasmaspheric Plasma into the Outer Magnetosphere and <span class="hlt">Boundary</span> Layer Region: Initial Results</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ober, Daniel M.; Horwitz, J. L.</p> <p>1998-01-01</p> <p>We present initial results on the modeling of the circulation of plasmaspheric-origin plasma into the outer magnetosphere and low-latitude <span class="hlt">boundary</span> layer (LLBL), using a dynamic global core plasma model (DGCPM). The DGCPM includes the influences of spatially and temporally varying convection and refilling processes to calculate the equatorial core plasma density distribution throughout the magnetosphere. We have developed an initial description of the electric and <span class="hlt">magnetic</span> field structures in the outer magnetosphere region. The purpose of this paper is to examine both the losses of plasmaspheric-origin plasma into the magnetopause <span class="hlt">boundary</span> layer and the convection of this plasma that remains trapped on closed <span class="hlt">magnetic</span> field lines. For the LLBL electric and <span class="hlt">magnetic</span> structures we have adopted here, the plasmaspheric plasma reaching the outer magnetosphere is diverted anti-sunward primarily along the dusk flank. These plasmas reach X= -15 R(sub E) in the LLBL approximately 3.2 hours after the initial enhancement of convection and continues to populate the LLBL for 12 hours as the convection electric field diminishes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017TMP...193.1811E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TMP...193.1811E"><span>The critical <span class="hlt">boundary</span> RSOS M(3,5) model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>El Deeb, O.</p> <p>2017-12-01</p> <p>We consider the critical nonunitary minimal model M(3, 5) with integrable <span class="hlt">boundaries</span> and analyze the patterns of zeros of the eigenvalues of the transfer matrix and then determine the spectrum of the critical theory using the thermodynamic Bethe ansatz ( TBA) equations. Solving the TBA functional equation satisfied by the transfer matrices of the associated A 4 restricted solid-on-solid Forrester-Baxter lattice model in regime III in the continuum scaling limit, we derive the integral TBA equations for all excitations in the ( r, s) = (1, 1) <span class="hlt">sector</span> and then determine their corresponding energies. We classify the excitations in terms of ( m, n) systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12424516','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12424516"><span>Public and private <span class="hlt">sector</span> contributions to the discovery and development of "impact" drugs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Reichert, Janice M; Milne, Christopher-Paul</p> <p>2002-01-01</p> <p>Recently, well-publicized reports by Public Citizen and the Joint Economic Committee (JEC) of the US Congress questioned the role of the drug industry in the discovery and development of therapeutically important drugs. To gain a better understanding of the relative roles of the public and private <span class="hlt">sectors</span> in pharmaceutic innovation, the Tufts Center for the Study of Drug Development evaluated the underlying National Institutes of Health (NIH) and academic research cited in the Public Citizen and JEC reports and performed its own assessment of the relationship between the private and public <span class="hlt">sectors</span> in drug discovery and development of 21 "impact" drugs. We found that, ultimately, any attempt to measure the relative contribution of the public and private <span class="hlt">sectors</span> to the research and development (R&D) of therapeutically important drugs by output alone, such as counting publications or even product approvals, is flawed. Several key factors (eg, degree of uncertainty, expected market value, potential social benefit) affect investment decisions and determine whether public or private <span class="hlt">sector</span> funds, or both, are most appropriate. Because of the competitiveness and complexity of today's R&D environment, both <span class="hlt">sectors</span> are increasingly challenged to show returns on their investment and the traditional <span class="hlt">boundaries</span> separating the roles of the private and public research spheres have become increasingly blurred. What remains clear, however, is that the process still starts with good science and ends with good medicine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21306239','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21306239"><span>The role of public-<span class="hlt">sector</span> research in the discovery of drugs and vaccines.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stevens, Ashley J; Jensen, Jonathan J; Wyller, Katrine; Kilgore, Patrick C; Chatterjee, Sabarni; Rohrbaugh, Mark L</p> <p>2011-02-10</p> <p>Historically, public-<span class="hlt">sector</span> researchers have performed the upstream, basic research that elucidated the underlying mechanisms of disease and identified promising points of intervention, whereas corporate researchers have performed the downstream, applied research resulting in the discovery of drugs for the treatment of diseases and have carried out development activities to bring them to market. However, the <span class="hlt">boundaries</span> between the roles of the public and private <span class="hlt">sectors</span> have shifted substantially since the dawn of the biotechnology era, and the public <span class="hlt">sector</span> now has a much more direct role in the applied-research phase of drug discovery. We identified new drugs and vaccines approved by the Food and Drug Administration (FDA) that were discovered by public-<span class="hlt">sector</span> research institutions (PSRIs) and classified them according to their therapeutic category and potential therapeutic effect. We found that during the past 40 years, 153 new FDA-approved drugs, vaccines, or new indications for existing drugs were discovered through research carried out in PSRIs. These drugs included 93 small-molecule drugs, 36 biologic agents, 15 vaccines, 8 in vivo diagnostic materials, and 1 over-the-counter drug. More than half of these drugs have been used in the treatment or prevention of cancer or infectious diseases. PSRI-discovered drugs are expected to have a disproportionately large therapeutic effect. Public-<span class="hlt">sector</span> research has had a more immediate effect on improving public health than was previously realized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5379487','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5379487"><span>Atomic structure and electronic properties of MgO grain <span class="hlt">boundaries</span> in tunnelling magnetoresistive devices</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bean, Jonathan J.; Saito, Mitsuhiro; Fukami, Shunsuke; Sato, Hideo; Ikeda, Shoji; Ohno, Hideo; Ikuhara, Yuichi; McKenna, Keith P.</p> <p>2017-01-01</p> <p>Polycrystalline metal oxides find diverse applications in areas such as nanoelectronics, photovoltaics and catalysis. Although grain <span class="hlt">boundary</span> defects are ubiquitous their structure and electronic properties are very poorly understood since it is extremely challenging to probe the structure of buried interfaces directly. In this paper we combine novel plan-view high-resolution transmission electron microscopy and first principles calculations to provide atomic level understanding of the structure and properties of grain <span class="hlt">boundaries</span> in the barrier layer of a <span class="hlt">magnetic</span> tunnel junction. We show that the highly [001] textured MgO films contain numerous tilt grain <span class="hlt">boundaries</span>. First principles calculations reveal how these grain <span class="hlt">boundaries</span> are associated with locally reduced band gaps (by up to 3 eV). Using a simple model we show how shunting a proportion of the tunnelling current through grain <span class="hlt">boundaries</span> imposes limits on the maximum magnetoresistance that can be achieved in devices. PMID:28374755</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1174551','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1174551"><span>Method and system for controlling start of a permanent <span class="hlt">magnet</span> machine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Walters, James E.; Krefta, Ronald John</p> <p>2003-10-28</p> <p>Method and system for controlling a permanent <span class="hlt">magnet</span> machine are provided. The method provides a sensor assembly for sensing rotor <span class="hlt">sector</span> position relative to a plurality of angular <span class="hlt">sectors</span>. The method further provides a sensor for sensing angular increments in rotor position. The method allows starting the machine in a brushless direct current mode of operation using a calculated initial rotor position based on an initial angular <span class="hlt">sector</span> position information from the sensor assembly. Upon determining a transition from the initial angular <span class="hlt">sector</span> to the next angular <span class="hlt">sector</span>, the method allows switching to a sinusoidal mode of operation using rotor position based on rotor position information from the incremental sensor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3878613','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3878613"><span>Magnetoacoustic Tomography with <span class="hlt">Magnetic</span> Induction: A Rigorous Theory</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ma, Qingyu; He, Bin</p> <p>2013-01-01</p> <p>We have proposed a new theory on mechanism of the magnetoacoustic signal generation with <span class="hlt">magnetic</span> induction for an object with an arbitrary shape. An object under a static <span class="hlt">magnetic</span> field emits acoustic signals when excited by a time-varying <span class="hlt">magnetic</span> field, and that the acoustic waveform is mainly generated at the conductivity <span class="hlt">boundaries</span> within the object. The proposed theory on the magnetoacoustic tomography with <span class="hlt">magnetic</span> induction produced highly consistent results among computational and experimental paradigms in a two-layer sample phantom and suggests the potential applications for bioimpedance imaging. PMID:18270025</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760007457','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760007457"><span>Apparent relationship between solar <span class="hlt">sector</span> <span class="hlt">boundaries</span> and 300-millibar vorticity: Possible explanation in terms of upward propagation of planetary-scale waves</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Deland, R. J.</p> <p>1975-01-01</p> <p>The correlations between the solar <span class="hlt">sectors</span> and large-scale atmospheric vorticity in the lower atmosphere reported earlier are of interest since the solar-<span class="hlt">sector</span> data appear to be independent of any terrestrial influences. It is shown that even these solar data may be affected by geomagnetic properties; a method for removing such influences is suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22497263','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22497263"><span>A novel technique for tailoring frontal osteoplastic flaps using the ENT <span class="hlt">magnetic</span> navigation system.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Volpi, Luca; Pistochini, Andrea; Bignami, Maurizio; Meloni, Francesco; Turri Zanoni, Mario; Castelnuovo, Paolo</p> <p>2012-06-01</p> <p>The ENT <span class="hlt">magnetic</span> navigation system is potentially useful and offers the most accurate technique for harvesting frontal osteoplastic flaps. It represents a valid tool in the wide range of instruments available to rhinologists. Precise delineation of the <span class="hlt">boundaries</span> of the frontal sinus is a crucial step when harvesting a frontal osteoplastic flap. We present a novel technique using the ENT <span class="hlt">magnetic</span> navigation system. Nineteen patients affected by different pathologies involving the frontal sinus underwent an osteoplastic flap procedure using the ENT <span class="hlt">magnetic</span> navigation system between January 2009 and April 2011. The ENT <span class="hlt">magnetic</span> navigation system was found to be a safe and accurate tool for delineating the frontal sinus <span class="hlt">boundaries</span>. No intraoperative complications occurred during the osteoplastic procedures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005GSASp.384..191S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005GSASp.384..191S"><span>Chicxulub ejecta at the Cretaceous-Paleogene (K-P) <span class="hlt">boundary</span> in Northeastern Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schulte, Peter; Kontny, Agnes</p> <p>2005-04-01</p> <p>The combined petrological and rock <span class="hlt">magnetic</span> study of the Cretaceous-Paleogene (K-P) <span class="hlt">boundary</span> in northeastern Mexico revealed compositionally and texturally complex Chicxulub ejecta deposits. The predominant silicic ejecta components are Fe-Mg-rich chlorite and Si-Al-K-rich glass spherules with carbonate inclusions and schlieren. Besides these silica phases, the most prominent ejecta component is carbonate. Carbonate occurs as lithic clasts, accretionary lapilli, melt globules (often with quench textures), and as microspar. The composition of the spherules provides evidence for a range of target rocks of mafic to intermediate composition, presumably situated in the northwestern <span class="hlt">sector</span> of the Chicxulub impact structure. The abundance of carbonate ejecta suggests that this area received ejecta mainly from shallow, carbonate-rich lithologies. Rare µm-sized metallic and sulfidic Ni-Co-rich inclusions in the spherules indicate a possible contamination by meteoritic material. This complex composition underlines the similarities of ejecta in NE Mexico to Chicxulub ejecta from K-P sections worldwide. Although the ejecta display a great variability, the <span class="hlt">magnetic</span> susceptibility, remanence, and hysteresis properties of the ejecta deposits are fairly homogeneous, with dominantly paramagnetic susceptibilities and a weak ferromagnetic contribution from hematite and goethite. The absence of spinels and the ubiquitous presence of hematite and goethite points to high oxygen fugacity during the impact process. The microfacies and internal texture of the ejecta deposits show welding and fusing of components, as well as evidence for liquid immiscibility between silicic and carbonate melts. No evidence for binary mixing of ejecta phases was found. Therefore, Chicxulub ejecta in NE Mexico probably derived from less energetic parts of the ejecta curtain. However, welding features of ejecta particles and enclosed marl clasts and/or benthic foraminifera from a siliciclastic environment</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GeoJI.196.1375R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GeoJI.196.1375R"><span>Chemical and <span class="hlt">magnetic</span> properties of rapidly cooled metastable ferri-ilmenite solid solutions - IV: the fine structure of self-reversed thermoremanent <span class="hlt">magnetization</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robinson, Peter; McEnroe, S. A.; Fabian, K.; Harrison, R. J.; Thomas, C. I.; Mukai, H.</p> <p>2014-03-01</p> <p><span class="hlt">Magnetic</span> experiments, a Monte Carlo simulation and transmission electron microscopy observations combine to confirm variable chemical phase separation during quench and annealing of metastable ferri-ilmenite compositions, caused by inhomogeneous Fe-Ti ordering and anti-ordering. Separation begins near interfaces between growing ordered and anti-ordered domains, the latter becoming progressively enriched in ilmenite component, moving the Ti-impoverished hematite component into Fe-enriched diffusion waves near the interfaces. Even when disordered regions are eliminated, Fe-enriched waves persist and enlarge on anti-phase <span class="hlt">boundaries</span> between growing and shrinking ordered and anti-ordered domains. <span class="hlt">Magnetic</span> results and conceptual models show that <span class="hlt">magnetic</span> ordering with falling T initiates in the Fe-enriched wave crests. Although representing only a tiny fraction of material, identified at highest Ts on a field-cooling curve, they control the `pre-destiny' of progressive <span class="hlt">magnetization</span> at lower T. They can provide a positive <span class="hlt">magnetic</span> moment in a minority of ordered ferrimagnetic material, which, by exchange coupling, then creates a self-reversed negative moment in the remaining majority. Four Ts or T ranges are recognized on typical field-cooling curves: TPD is the T range of `pre-destination'; TC is the predominant Curie T where major positive <span class="hlt">magnetization</span> increases sharply; TMAX is where <span class="hlt">magnetization</span> reaches a positive maximum, beyond which it is outweighed by self-reversed <span class="hlt">magnetization</span> and TZM is the T where total <span class="hlt">magnetization</span> passes zero. Disposition of these Ts on cooling curves indicate the fine structure of self-reversed thermoremanent <span class="hlt">magnetization</span>. These results confirm much earlier suspicions that the `x-phase' responsible for self-reversed <span class="hlt">magnetization</span> resides in Fe-enriched phase <span class="hlt">boundaries</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29032622','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29032622"><span>Harnessing private <span class="hlt">sector</span> expertise to improve complementary feeding within a regulatory framework: Where is the evidence?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>van Liere, Marti J; Tarlton, Dessie; Menon, Ravi; Yellamanda, M; Reerink, Ietje</p> <p>2017-10-01</p> <p>Global recognition that the complex and multicausal problems of malnutrition require all players to collaborate and to invest towards the same objective has led to increased private <span class="hlt">sector</span> engagement as exemplified through the Scaling Up Nutrition Business Network and mechanisms for blended financing and matched funding, such as the Global Nutrition for Growth Compact. The careful steps made over the past 5 to 10 years have however not taken away or reduced the hesitation and scepticism of the public <span class="hlt">sector</span> actors towards commercial or even social businesses. Evidence of impact or even a positive contribution of a private <span class="hlt">sector</span> approach to intermediate nutrition outcomes is still lacking. This commentary aims to discuss the multiple ways in which private <span class="hlt">sector</span> can leverage its expertise to improve nutrition in general, and complementary feeding in particular. It draws on specific lessons learned in Bangladesh, Côte d'Ivoire, India, Indonesia, and Madagascar on how private <span class="hlt">sector</span> expertise has contributed, within the <span class="hlt">boundaries</span> of a regulatory framework, to improve availability, accessibility, affordability, and adequate use of nutritious foods. It concludes that a solid evidence base regarding the contribution of private <span class="hlt">sector</span> to complementary feeding is still lacking and that the development of a systematic learning agenda is essential to make progress in the area of private <span class="hlt">sector</span> engagement in nutrition. © 2017 John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22130800-kelvin-helmholtz-instability-coronal-mass-ejection-boundaries-solar-corona-observations-mhd-simulations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22130800-kelvin-helmholtz-instability-coronal-mass-ejection-boundaries-solar-corona-observations-mhd-simulations"><span>THE KELVIN-HELMHOLTZ INSTABILITY AT CORONAL MASS EJECTION <span class="hlt">BOUNDARIES</span> IN THE SOLAR CORONA: OBSERVATIONS AND 2.5D MHD SIMULATIONS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moestl, U. V.; Temmer, M.; Veronig, A. M., E-mail: ute.moestl@uni-graz.at</p> <p>2013-03-20</p> <p>The Atmospheric Imaging Assembly on board the Solar Dynamics Observatory observed a coronal mass ejection with an embedded filament on 2011 February 24, revealing quasi-periodic vortex-like structures at the northern side of the filament <span class="hlt">boundary</span> with a wavelength of approximately 14.4 Mm and a propagation speed of about 310 {+-} 20 km s{sup -1}. These structures could result from the Kelvin-Helmholtz instability occurring on the <span class="hlt">boundary</span>. We perform 2.5D numerical simulations of the Kelvin-Helmholtz instability and compare the simulated characteristic properties of the instability with the observations, where we obtain qualitative as well as quantitative accordance. We study the absencemore » of Kelvin-Helmholtz vortex-like structures on the southern side of the filament <span class="hlt">boundary</span> and find that a <span class="hlt">magnetic</span> field component parallel to the <span class="hlt">boundary</span> with a strength of about 20% of the total <span class="hlt">magnetic</span> field has stabilizing effects resulting in an asymmetric development of the instability.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/864338','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/864338"><span>Thermomagnetic burn control for <span class="hlt">magnetic</span> fusion reactor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Rawls, John M.; Peuron, Unto A.</p> <p>1982-01-01</p> <p>Apparatus is provided for controlling the plasma energy production rate of a <span class="hlt">magnetic</span>-confinement fusion reactor, by controlling the <span class="hlt">magnetic</span> field ripple. The apparatus includes a group of shield <span class="hlt">sectors</span> (30a, 30b, etc.) formed of ferromagnetic material which has a temperature-dependent saturation <span class="hlt">magnetization</span>, with each shield lying between the plasma (12) and a toroidal field coil (18). A mechanism (60) for controlling the temperature of the <span class="hlt">magnetic</span> shields, as by controlling the flow of cooling water therethrough, thereby controls the saturation <span class="hlt">magnetization</span> of the shields and therefore the amount of ripple in the <span class="hlt">magnetic</span> field that confines the plasma, to thereby control the amount of heat loss from the plasma. This heat loss in turn determines the plasma state and thus the rate of energy production.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22113314-unique-topological-characterization-braided-magnetic-fields','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22113314-unique-topological-characterization-braided-magnetic-fields"><span>Unique topological characterization of braided <span class="hlt">magnetic</span> fields</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yeates, A. R.; Hornig, G.</p> <p></p> <p>We introduce a topological flux function to quantify the topology of <span class="hlt">magnetic</span> braids: non-zero, line-tied <span class="hlt">magnetic</span> fields whose field lines all connect between two <span class="hlt">boundaries</span>. This scalar function is an ideal invariant defined on a cross-section of the <span class="hlt">magnetic</span> field, and measures the average poloidal <span class="hlt">magnetic</span> flux around any given field line, or the average pairwise crossing number between a given field line and all others. Moreover, its integral over the cross-section yields the relative <span class="hlt">magnetic</span> helicity. Using the fact that the flux function is also an action in the Hamiltonian formulation of the field line equations, we prove thatmore » it uniquely characterizes the field line mapping and hence the <span class="hlt">magnetic</span> topology.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22130430-observation-low-magnetic-field-density-peaks-helicon-plasma','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22130430-observation-low-magnetic-field-density-peaks-helicon-plasma"><span>Observation of low <span class="hlt">magnetic</span> field density peaks in helicon plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.</p> <p>2013-04-15</p> <p>Single density peak has been commonly observed in low <span class="hlt">magnetic</span> field (<100 G) helicon discharges. In this paper, we report the observations of multiple density peaks in low <span class="hlt">magnetic</span> field (<100 G) helicon discharges produced in the linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. Experiments are carried out using argon gas with m = +1 right helical antenna operating at 13.56 MHz by varying the <span class="hlt">magnetic</span> field from 0 G to 100 G. The plasma density varies with varying the <span class="hlt">magnetic</span> field at constant input power and gas pressure and reaches to its peakmore » value at a <span class="hlt">magnetic</span> field value of {approx}25 G. Another peak of smaller magnitude in density has been observed near 50 G. Measurement of amplitude and phase of the axial component of the wave using <span class="hlt">magnetic</span> probes for two <span class="hlt">magnetic</span> field values corresponding to the observed density peaks indicated the existence of radial modes. Measured parallel wave number together with the estimated perpendicular wave number suggests oblique mode propagation of helicon waves along the resonance cone <span class="hlt">boundary</span> for these <span class="hlt">magnetic</span> field values. Further, the observations of larger floating potential fluctuations measured with Langmuir probes at those <span class="hlt">magnetic</span> field values indicate that near resonance cone <span class="hlt">boundary</span>; these electrostatic fluctuations take energy from helicon wave and dump power to the plasma causing density peaks.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22273910-characterization-grain-boundary-conductivity-spin-sprayed-ferrites-using-scanning-microwave-microscope','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22273910-characterization-grain-boundary-conductivity-spin-sprayed-ferrites-using-scanning-microwave-microscope"><span>Characterization of grain <span class="hlt">boundary</span> conductivity of spin-sprayed ferrites using scanning microwave microscope</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Myers, J.; Nicodemus, T.; Zhuang, Y., E-mail: yan.zhuang@wright.edu</p> <p>2014-05-07</p> <p>Grain <span class="hlt">boundary</span> electrical conductivity of ferrite materials has been characterized using scanning microwave microscope. Structural, electrical, and <span class="hlt">magnetic</span> properties of Fe{sub 3}O{sub 4} spin-sprayed thin films onto glass substrates for different length of growth times were investigated using a scanning microwave microscope, an atomic force microscope, a four-point probe measurement, and a made in house transmission line based <span class="hlt">magnetic</span> permeameter. The real part of the <span class="hlt">magnetic</span> permeability shows almost constant between 10 and 300 MHz. As the Fe{sub 3}O{sub 4} film thickness increases, the grain size becomes larger, leading to a higher DC conductivity. However, the loss in the Fe{sub 3}O{submore » 4} films at high frequency does not increase correspondingly. By measuring the reflection coefficient s{sub 11} from the scanning microwave microscope, it turns out that the grain <span class="hlt">boundaries</span> of the Fe{sub 3}O{sub 4} films exhibit higher electric conductivity than the grains, which contributes loss at radio frequencies. This result will provide guidance for further improvement of low loss ferrite materials for high frequency applications.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED398434.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED398434.pdf"><span>Short Summary European Reports on Retail <span class="hlt">Sector</span>, Motor Vehicle Repair and Sales <span class="hlt">Sector</span>, Food and Beverages <span class="hlt">Sector</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>European Centre for the Development of Vocational Training, Berlin (Germany).</p> <p></p> <p>This document is composed of European synthesis reports on retail trade, the agro-food <span class="hlt">sector</span>, and the motor vehicle sales and repair <span class="hlt">sector</span>. They are based on the most important findings of the European report and the 12 national reports for each <span class="hlt">sector</span>. Section 1, "Retail <span class="hlt">Sector</span>," deals in part 1 with the structure of retailing in the…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SuScT..29b4003O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SuScT..29b4003O"><span><span class="hlt">Magnetization</span> behavior of RE123 bulk <span class="hlt">magnets</span> bearing twin seed-crystals in pulsed field <span class="hlt">magnetization</span> processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oka, T.; Miyazaki, T.; Ogawa, J.; Fukui, S.; Sato, T.; Yokoyama, K.; Langer, M.</p> <p>2016-02-01</p> <p>Melt-textured Y-Ba-Cu-O high temperature superconducting bulk <span class="hlt">magnets</span> were fabricated by the cold seeding method with using single or twin-seed crystals composed of Nd-Ba-Cu-O thin films on MgO substrates. The behavior of the <span class="hlt">magnetic</span> flux penetration into anisotropic-grown bulk <span class="hlt">magnets</span> thus fabricated was precisely evaluated during and after the pulsed field <span class="hlt">magnetization</span> operated at 35 K. These seed crystals were put on the top surfaces of the precursors to grow large grains during the melt-processes. Although we know the <span class="hlt">magnetic</span> flux motion is restricted by the enhanced pinning effect in temperature ranges lower than 77 K, we observed that flux invasion occurred at applied fields of 3.3 T when the twin seeds were used. This is definitely lower than those of 3.7 T when the single-seeds were employed. This means that the <span class="hlt">magnetic</span> fluxes are capable of invading into twin-seeded bulk <span class="hlt">magnets</span> more easily than single-seeded ones. The twin seeds form the different grain growth regions, the narrow-GSR (growth <span class="hlt">sector</span> region) and wide-GSR, according to the different grain growth directions which are parallel and normal to the rows of seed crystals, respectively. The invading flux measurements revealed that the <span class="hlt">magnetic</span> flux invades the sample from the wide-GSR prior to the narrow-GSR. It suggests that such anisotropic grain growth leads to different distributions of pinning centers, variations of J c values, and the formation of preferential paths for the invading <span class="hlt">magnetic</span> fluxes. Using lower applied fields definitely contributed to lowering the heat generation during the PFM process, which, in turn, led to enhanced trapped <span class="hlt">magnetic</span> fluxes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JPhD...51s3002F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JPhD...51s3002F"><span>Micromagnetics of rare-earth efficient permanent <span class="hlt">magnets</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischbacher, Johann; Kovacs, Alexander; Gusenbauer, Markus; Oezelt, Harald; Exl, Lukas; Bance, Simon; Schrefl, Thomas</p> <p>2018-05-01</p> <p>The development of permanent <span class="hlt">magnets</span> containing less or no rare-earth elements is linked to profound knowledge of the coercivity mechanism. Prerequisites for a promising permanent <span class="hlt">magnet</span> material are a high spontaneous <span class="hlt">magnetization</span> and a sufficiently high <span class="hlt">magnetic</span> anisotropy. In addition to the intrinsic <span class="hlt">magnetic</span> properties the microstructure of the <span class="hlt">magnet</span> plays a significant role in establishing coercivity. The influence of the microstructure on coercivity, remanence, and energy density product can be understood by using micromagnetic simulations. With advances in computer hardware and numerical methods, hysteresis curves of <span class="hlt">magnets</span> can be computed quickly so that the simulations can readily provide guidance for the development of permanent <span class="hlt">magnets</span>. The potential of rare-earth reduced and rare-earth free permanent <span class="hlt">magnets</span> is investigated using micromagnetic simulations. The results show excellent hard <span class="hlt">magnetic</span> properties can be achieved in grain <span class="hlt">boundary</span> engineered NdFeB, rare-earth <span class="hlt">magnets</span> with a ThMn12 structure, Co-based nano-wires, and L10-FeNi provided that the magnet’s microstructure is optimized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840064432&hterms=force+origins&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dforce%2Borigins','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840064432&hterms=force+origins&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dforce%2Borigins"><span>On some properties of force-free <span class="hlt">magnetic</span> fields in infinite regions of space</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Aly, J. J.</p> <p>1984-01-01</p> <p>Techniques for solving <span class="hlt">boundary</span> value problems (BVP) for a force free <span class="hlt">magnetic</span> field (FFF) in infinite space are presented. A priori inequalities are defined which must be satisfied by the force-free equations. It is shown that upper bounds may be calculated for the <span class="hlt">magnetic</span> energy of the region provided the value of the <span class="hlt">magnetic</span> normal component at the <span class="hlt">boundary</span> of the region can be shown to decay sufficiently fast at infinity. The results are employed to prove a nonexistence theorem for the BVP for the FFF in the spatial region. The implications of the theory for modeling the origins of solar flares are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1208..593V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1208..593V"><span>Permanent <span class="hlt">Magnet</span> Spiral Motor for <span class="hlt">Magnetic</span> Gradient Energy Utilization: Axial <span class="hlt">Magnetic</span> Field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Valone, Thomas F.</p> <p>2010-01-01</p> <p> power for <span class="hlt">magnetic</span> field switching device can be achieved in order to deflect the rotor <span class="hlt">magnet</span> in transit. The Wiegand effect itself (bistable FeCoV wire called "Vicalloy") invented by John Wiegand (Switchable <span class="hlt">Magnetic</span> Device, US Patent ♯4,247,601), utilizing Barkhausen jumps of <span class="hlt">magnetic</span> domains, is also applied for a similar achievement (Dilatush, 1977). Conventional approaches for spiral <span class="hlt">magnetic</span> gradient force production have not been adequate for magnetostatic motors to perform useful work. It is proposed that integrating a <span class="hlt">magnetic</span> force control device with a spiral stator inhomogeneous axial <span class="hlt">magnetic</span> field motor is a viable approach to add a sufficient nonlinear <span class="hlt">boundary</span> shift to apply the angular momentum and potential energy gained in 315 degrees of the motor cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JHEP...12..041R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JHEP...12..041R"><span>Holographic vortices in the presence of dark matter <span class="hlt">sector</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rogatko, Marek; Wysokinski, Karol I.</p> <p>2015-12-01</p> <p>The dark matter seem to be an inevitable ingredient of the total matter configuration in the Universe and the knowledge how the dark matter affects the properties of superconductors is of vital importance for the experiments aimed at its direct detection. The homogeneous <span class="hlt">magnetic</span> field acting perpendicularly to the surface of (2+1) dimensional s-wave holographic superconductor in the theory with dark matter <span class="hlt">sector</span> has been modeled by the additional U(1)-gauge field representing dark matter and coupled to the Maxwell one. As expected the free energy for the vortex configuration turns out to be negative. Importantly its value is lower in the presence of dark matter <span class="hlt">sector</span>. This feature can explain why in the Early Universe first the web of dark matter appeared and next on these gratings the ordinary matter forming cluster of galaxies has formed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Natur.548..561N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Natur.548..561N"><span><span class="hlt">Magnetic</span> antiskyrmions above room temperature in tetragonal Heusler materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nayak, Ajaya K.; Kumar, Vivek; Ma, Tianping; Werner, Peter; Pippel, Eckhard; Sahoo, Roshnee; Damay, Franoise; Rößler, Ulrich K.; Felser, Claudia; Parkin, Stuart S. P.</p> <p>2017-08-01</p> <p><span class="hlt">Magnetic</span> skyrmions are topologically stable, vortex-like objects surrounded by chiral <span class="hlt">boundaries</span> that separate a region of reversed <span class="hlt">magnetization</span> from the surrounding <span class="hlt">magnetized</span> material. They are closely related to nanoscopic chiral <span class="hlt">magnetic</span> domain walls, which could be used as memory and logic elements for conventional and neuromorphic computing applications that go beyond Moore’s law. Of particular interest is ‘racetrack memory’, which is composed of vertical <span class="hlt">magnetic</span> nanowires, each accommodating of the order of 100 domain walls, and that shows promise as a solid state, non-volatile memory with exceptional capacity and performance. Its performance is derived from the very high speeds (up to one kilometre per second) at which chiral domain walls can be moved with nanosecond current pulses in synthetic antiferromagnet racetracks. Because skyrmions are essentially composed of a pair of chiral domain walls closed in on themselves, but are, in principle, more stable to perturbations than the component domain walls themselves, they are attractive for use in spintronic applications, notably racetrack memory. Stabilization of skyrmions has generally been achieved in systems with broken inversion symmetry, in which the asymmetric Dzyaloshinskii-Moriya interaction modifies the uniform <span class="hlt">magnetic</span> state to a swirling state. Depending on the crystal symmetry, two distinct types of skyrmions have been observed experimentally, namely, Bloch and Néel skyrmions. Here we present the experimental manifestation of another type of skyrmion—the <span class="hlt">magnetic</span> antiskyrmion—in acentric tetragonal Heusler compounds with D2d crystal symmetry. Antiskyrmions are characterized by <span class="hlt">boundary</span> walls that have alternating Bloch and Néel type as one traces around the <span class="hlt">boundary</span>. A spiral <span class="hlt">magnetic</span> ground-state, which propagates in the tetragonal basal plane, is transformed into an antiskyrmion lattice state under <span class="hlt">magnetic</span> fields applied along the tetragonal axis over a wide range of temperatures</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhFl...29i2006R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhFl...29i2006R"><span>Computer simulations of equilibrium <span class="hlt">magnetization</span> and microstructure in <span class="hlt">magnetic</span> fluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rosa, A. P.; Abade, G. C.; Cunha, F. R.</p> <p>2017-09-01</p> <p>In this work, Monte Carlo and Brownian Dynamics simulations are developed to compute the equilibrium <span class="hlt">magnetization</span> of a <span class="hlt">magnetic</span> fluid under action of a homogeneous applied <span class="hlt">magnetic</span> field. The particles are free of inertia and modeled as hard spheres with the same diameters. Two different periodic <span class="hlt">boundary</span> conditions are implemented: the minimum image method and Ewald summation technique by replicating a finite number of particles throughout the suspension volume. A comparison of the equilibrium <span class="hlt">magnetization</span> resulting from the minimum image approach and Ewald sums is performed by using Monte Carlo simulations. The Monte Carlo simulations with minimum image and lattice sums are used to investigate suspension microstructure by computing the important radial pair-distribution function go(r), which measures the probability density of finding a second particle at a distance r from a reference particle. This function provides relevant information on structure formation and its anisotropy through the suspension. The numerical results of go(r) are compared with theoretical predictions based on quite a different approach in the absence of the field and dipole-dipole interactions. A very good quantitative agreement is found for a particle volume fraction of 0.15, providing a validation of the present simulations. In general, the investigated suspensions are dominated by structures like dimmer and trimmer chains with trimmers having probability to form an order of magnitude lower than dimmers. Using Monte Carlo with lattice sums, the density distribution function g2(r) is also examined. Whenever this function is different from zero, it indicates structure-anisotropy in the suspension. The dependence of the equilibrium <span class="hlt">magnetization</span> on the applied field, the <span class="hlt">magnetic</span> particle volume fraction, and the magnitude of the dipole-dipole <span class="hlt">magnetic</span> interactions for both <span class="hlt">boundary</span> conditions are explored in this work. Results show that at dilute regimes and with moderate dipole</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820006119','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820006119"><span>Observational data needs for plasma phenomena</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Niedner, M. B., Jr.</p> <p>1981-01-01</p> <p>Bright comets display a rich variety of interesting plasma phenomena which occur over an enormous range of spatial scales, and which require different observational techniques to be studied effectively. Wide-angle photography of high time resolution is probably the best method of studying the phenomenon of largest known scale: the plasma tail disconnection event (DE), which has been attributed to <span class="hlt">magnetic</span> reconnection at interplanetary <span class="hlt">sector</span> <span class="hlt">boundary</span> crossings. These structures usually accelerate as they recede from the head region and observed velocities are typically in the range 50 V km/s. They are often visible for several days following the time of disconnection, and are sometimes seen out past 0.2 AU from the cometary head. The following areas pertaining to plasma phenomena in the ionoshere are addressed: the existence, size, and heliocentric distance variations of the contact surface, and the observational signatures of <span class="hlt">magnetic</span> reconnection at <span class="hlt">sector</span> <span class="hlt">boundary</span> crossings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24779990','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24779990"><span>Improving the physical health of people with severe mental illness: <span class="hlt">boundaries</span> of care provision.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ehrlich, Carolyn; Kendall, Elizabeth; Frey, Nicolette; Kisely, Steve; Crowe, Elizabeth; Crompton, David</p> <p>2014-06-01</p> <p>There is compelling evidence that the physical health of people with severe mental illness is poor. Health-promotion guidelines have been recommended as a mechanism for improving the physical health of this population. However, there are significant barriers to the adoption of evidence-based guidelines in practice. The purpose of this research was to apply existing implementation theories to examine the capability of the health system to integrate physical health promotion into mental health service delivery. Data were collected within a regional city in Queensland, Australia. Fifty participants were interviewed. The core theme that emerged from the data was that of 'care <span class="hlt">boundaries</span>' that influenced the likelihood of guidelines being implemented. <span class="hlt">Boundaries</span> existed around the illness, care provision processes, <span class="hlt">sectors</span>, the health-care system, and society. These multilevel <span class="hlt">boundaries</span>, combined with participants' ways of responding to them, impacted on capability (i.e. the ability to integrate physical health promotion into existing practices). Participants who were able to identify strategies to mediate these <span class="hlt">boundaries</span> were better positioned to engage with physical health-promotion practice. Thus, the implementation of evidence-based guidelines depended heavily on the capability of the workforce to develop and adopt <span class="hlt">boundary</span>-mediating strategies. © 2013 Australian College of Mental Health Nurses Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhRvA..81a0102H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhRvA..81a0102H"><span>Entanglement and area law with a fractal <span class="hlt">boundary</span> in a topologically ordered phase</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hamma, Alioscia; Lidar, Daniel A.; Severini, Simone</p> <p>2010-01-01</p> <p>Quantum systems with short-range interactions are known to respect an area law for the entanglement entropy: The von Neumann entropy S associated to a bipartition scales with the <span class="hlt">boundary</span> p between the two parts. Here we study the case in which the <span class="hlt">boundary</span> is a fractal. We consider the topologically ordered phase of the toric code with a <span class="hlt">magnetic</span> field. When the field vanishes it is possible to analytically compute the entanglement entropy for both regular and fractal bipartitions (A,B) of the system and this yields an upper bound for the entire topological phase. When the A-B <span class="hlt">boundary</span> is regular we have S/p=1 for large p. When the <span class="hlt">boundary</span> is a fractal of the Hausdorff dimension D, we show that the entanglement between the two parts scales as S/p=γ⩽1/D, and γ depends on the fractal considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720055073&hterms=time+zone&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtime%2Bzone','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720055073&hterms=time+zone&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtime%2Bzone"><span>Local-time survey of plasma at low altitudes over the auroral zones.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Frank, L. A.; Ackerson, K. L.</p> <p>1972-01-01</p> <p>Local-time survey of the low-energy proton and electron intensities precipitated into the earth's atmosphere over the auroral zones during periods of <span class="hlt">magnetic</span> quiescence. This survey was constructed by selecting a typical individual satellite crossing of this region in each of eight local-time <span class="hlt">sectors</span> from a large library of similar observations with the polar-orbiting satellite Injun 5. The trapping <span class="hlt">boundary</span> for more-energetic electron intensities, E greater than 45 keV, was found to be a 'natural coordinate' for delineating the <span class="hlt">boundary</span> between the two major types of lower-energy, 50 less than or equal to E less than or equal to 15,000 eV, electron precipitation commonly observed over the auroral zones at low altitudes. Poleward of this trapping <span class="hlt">boundary</span> inverted 'V' electron precipitation bands are observed in all local-time <span class="hlt">sectors</span>. These inverted 'V' electron bands in the evening and midnight <span class="hlt">sectors</span> are typically more energetic and have greater latitudinal widths than their counterparts in the noon and morning <span class="hlt">sectors</span>. In general, the main contributors to the electron energy influx into the earth's atmosphere over the auroral zones are the electron inverted 'V' precipitation poleward of the trapping <span class="hlt">boundary</span> in late evening, the plasma-sheet electron intensities equatorward of this <span class="hlt">boundary</span> in early morning, and both of these precipitation events near local midnight.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AnPhy.372..482M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AnPhy.372..482M"><span>Classical impurities and <span class="hlt">boundary</span> Majorana zero modes in quantum chains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Müller, Markus; Nersesyan, Alexander A.</p> <p>2016-09-01</p> <p>We study the response of classical impurities in quantum Ising chains. The Z2 degeneracy they entail renders the existence of two decoupled Majorana modes at zero energy, an exact property of a finite system at arbitrary values of its bulk parameters. We trace the evolution of these modes across the transition from the disordered phase to the ordered one and analyze the concomitant qualitative changes of local <span class="hlt">magnetic</span> properties of an isolated impurity. In the disordered phase, the two ground states differ only close to the impurity, and they are related by the action of an explicitly constructed quasi-local operator. In this phase the local transverse spin susceptibility follows a Curie law. The critical response of a <span class="hlt">boundary</span> impurity is logarithmically divergent and maps to the two-channel Kondo problem, while it saturates for critical bulk impurities, as well as in the ordered phase. The results for the Ising chain translate to the related problem of a resonant level coupled to a 1d p-wave superconductor or a Peierls chain, whereby the <span class="hlt">magnetic</span> order is mapped to topological order. We find that the topological phase always exhibits a continuous impurity response to local fields as a result of the level repulsion of local levels from the <span class="hlt">boundary</span> Majorana zero mode. In contrast, the disordered phase generically features a discontinuous <span class="hlt">magnetization</span> or charging response. This difference constitutes a general thermodynamic fingerprint of topological order in phases with a bulk gap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT........32J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT........32J"><span>Spin-dependent heat transport and thermal <span class="hlt">boundary</span> resistance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeong, Taehee</p> <p></p> <p>In this thesis, thermal conductivity change depending on the <span class="hlt">magnetic</span> configurations has been studied. In order to make different <span class="hlt">magnetic</span> configurations, we developed a spin valve structure, which has high MR ratio and low saturation field. The high MR ratio was achieved using Co/Cu multilayer and 21A or 34A thick Cu layer. The low saturation field was obtained by implementing different coercivities of the successive ferromagnetic layers. For this purpose, Co/Cu/Cu tri-layered structure was used with the thicknesses of the Co layers; 15 A and 30 A. For the thermal conductivity measurement, a three-omega method was employed with a thermally isolated microscale rod. We fabricated the microscale rod using optical lithography and MEMS process. Then the rod was wire-bonded to a chip-carver for further electrical measurement. For the thermal conductivity measurement, we built the three-omega measurement system using two lock-in amplifiers and two differential amplifiers. A custom-made electromagnet was added to the system to investigate the impact of <span class="hlt">magnetic</span> field. We observed titanic thermal conductivity change depending on the <span class="hlt">magnetic</span> configurations of the Co/Cu/Co multilayer. The thermal conductivity change was closely correlated with that of the electric conductivity in terms of the spin orientation, but the thermal conductivity was much more sensitive than that of the electric conductivity. The relative thermal conductivity change was 50% meanwhile that of electric resistivity change was 8.0%. The difference between the two ratios suggests that the scattering mechanism for charge and heat transport in the Co/Cu/Co multilayer is different. The Lorentz number in Weidemann-Franz law is also spin-dependent. Thermal <span class="hlt">boundary</span> resistance between metal and dielectrics was also studied in this thesis. The thermal <span class="hlt">boundary</span> resistance becomes critical for heat transport in a nanoscale because the thermal <span class="hlt">boundary</span> resistance can potentially determine overall heat transport</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA.....7938L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA.....7938L"><span>Evidence for Weak Crustal <span class="hlt">Magnetic</span> Fields over the Hellas, Chryse, and Acidalia Planitiae</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, C. O.; Mitchell, D. L.; Lillis, R.; Lin, R. P.; Reme, H.; Cloutier, P. A.; Acuna, M. H.</p> <p>2003-04-01</p> <p>The Electron Reflectometer (ER) onboard Mars Global Surveyor (MGS) detected a plasma <span class="hlt">boundary</span> between the ionosphere and the solar wind as the latter is diverted around and past the planet [Mitchell et al., GRL, 27, 1871, 2000; Mitchell et al., JGR, 106, 23419, 2001]. Above this <span class="hlt">boundary</span> the 10-1000 eV electron population is dominated by solar wind electrons, while below the <span class="hlt">boundary</span> it is dominated by ionospheric photoelectrons. This "photoelectron <span class="hlt">boundary</span>", or PEB, is sensitive to pressure variations and moves vertically in response to changes in the ionospheric pressure from below and the solar wind pressure from above. The PEB is also sensitive to crustal <span class="hlt">magnetic</span> fields, which locally increase the total ionospheric pressure and positively bias the PEB altitude. We have empirically modeled and removed systematic variations in the PEB altitude associated with the solar wind interaction, thus isolating perturbations caused by crustal <span class="hlt">magnetic</span> fields. A map of the PEB altitude perturbations closely resembles maps of the horizontal component of the crustal <span class="hlt">magnetic</span> field measured at 400 km by the MGS Magnetometer (MAG). We find a PEB altitude bias over the Hellas basin that is consistent with a horizontal <span class="hlt">magnetic</span> field with an intensity of several nanotesla at 400 km altitude. This is compatible with upper limits to the horizontal crustal field strength set by MGS MAG measurements. Since there is no evidence for significant crustal <span class="hlt">magnetic</span> sources within the basin from MAG data obtained during aerobraking [Acuna et al. Science, 284, 790, 1999] or from electron reflection data obtained in the mapping orbit [Lillis et al., this conference], the most likely explanation is that the observed horizontal field originates from sources around the Hellas perimeter. No detectable PEB or <span class="hlt">magnetic</span> signature is observed over the younger Argyre and Isidis Basins. There is also evidence for a significant enhancement (several nanoteslas) in the crustal field strength over Chryse</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28159009','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28159009"><span>Pathways for best practice diffusion: the structure of informal relationships in Canada's long-term care <span class="hlt">sector</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dearing, James W; Beacom, Amanda M; Chamberlain, Stephanie A; Meng, Jingbo; Berta, Whitney B; Keefe, Janice M; Squires, Janet E; Doupe, Malcolm B; Taylor, Deanne; Reid, Robert Colin; Cook, Heather; Cummings, Greta G; Baumbusch, Jennifer L; Knopp-Sihota, Jennifer; Norton, Peter G; Estabrooks, Carole A</p> <p>2017-02-03</p> <p>Initiatives to accelerate the adoption and implementation of evidence-based practices benefit from an association with influential individuals and organizations. When opinion leaders advocate or adopt a best practice, others adopt too, resulting in diffusion. We sought to identify existing influence throughout Canada's long-term care <span class="hlt">sector</span> and the extent to which informal advice-seeking relationships tie the <span class="hlt">sector</span> together as a network. We conducted a sociometric survey of senior leaders in 958 long-term care facilities operating in 11 of Canada's 13 provinces and territories. We used an integrated knowledge translation approach to involve knowledge users in planning and administering the survey and in analyzing and interpreting the results. Responses from 482 senior leaders generated the names of 794 individuals and 587 organizations as sources of advice for improving resident care in long-term care facilities. A single advice-seeking network appears to span the nation. Proximity exhibits a strong effect on network structure, with provincial inter-organizational networks having more connections and thus a denser structure than interpersonal networks. We found credible individuals and organizations within groups (opinion leaders and opinion-leading organizations) and individuals and organizations that function as weak ties across groups (<span class="hlt">boundary</span> spanners and bridges) for all studied provinces and territories. A good deal of influence in the Canadian long-term care <span class="hlt">sector</span> rests with professionals such as provincial health administrators not employed in long-term care facilities. The Canadian long-term care <span class="hlt">sector</span> is tied together through informal advice-seeking relationships that have given rise to an emergent network structure. Knowledge of this structure and engagement with its opinion leaders and <span class="hlt">boundary</span> spanners may provide a route for stimulating the adoption and effective implementation of best practices, improving resident care and strengthening the long</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCo...712772F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCo...712772F"><span>A novel perovskite oxide chemically designed to show multiferroic phase <span class="hlt">boundary</span> with room-temperature magnetoelectricity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernández-Posada, Carmen M.; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey</p> <p>2016-09-01</p> <p>There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a <span class="hlt">magnetic</span> field or <span class="hlt">magnetism</span> with an electric one (for example, voltage-tunable spintronic devices, uncooled <span class="hlt">magnetic</span> sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO3-BiCoO3 solid solution, specifically at its morphotropic phase <span class="hlt">boundary</span> between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO3-BiMnO3-PbTiO3 ternary system, chemically designed to present such multiferroic phase <span class="hlt">boundary</span> with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27677353','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27677353"><span>A novel perovskite oxide chemically designed to show multiferroic phase <span class="hlt">boundary</span> with room-temperature magnetoelectricity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fernández-Posada, Carmen M; Castro, Alicia; Kiat, Jean-Michel; Porcher, Florence; Peña, Octavio; Algueró, Miguel; Amorín, Harvey</p> <p>2016-09-28</p> <p>There is a growing activity in the search of novel single-phase multiferroics that could finally provide distinctive magnetoelectric responses at room temperature, for they would enable a range of potentially disruptive technologies, making use of the ability of controlling polarization with a <span class="hlt">magnetic</span> field or <span class="hlt">magnetism</span> with an electric one (for example, voltage-tunable spintronic devices, uncooled <span class="hlt">magnetic</span> sensors and the long-searched magnetoelectric memory). A very promising novel material concept could be to make use of phase-change phenomena at structural instabilities of a multiferroic state. Indeed, large phase-change magnetoelectric response has been anticipated by a first-principles investigation of the perovskite BiFeO 3 -BiCoO 3 solid solution, specifically at its morphotropic phase <span class="hlt">boundary</span> between multiferroic polymorphs of rhombohedral and tetragonal symmetries. Here, we report a novel perovskite oxide that belongs to the BiFeO 3 -BiMnO 3 -PbTiO 3 ternary system, chemically designed to present such multiferroic phase <span class="hlt">boundary</span> with enhanced ferroelectricity and canted ferromagnetism, which shows distinctive room-temperature magnetoelectric responses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018EL....12145001W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018EL....12145001W"><span>Effects of resonant <span class="hlt">magnetic</span> perturbation on the triggering and the evolution of double-tearing mode</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, L.; Lin, W. B.; Wang, X. Q.</p> <p>2018-02-01</p> <p>The effects of resonant <span class="hlt">magnetic</span> perturbation on the triggering and the evolution of the double-tearing mode are investigated by using nonlinear magnetohydrodynamics simulations in a slab geometry. It is found that the double-tearing mode can be destabilized by <span class="hlt">boundary</span> <span class="hlt">magnetic</span> perturbation. Moreover, the mode has three typical development stages before it reaches saturation: the linear stable stage, the linear-growth stage, and the exponential-growth stage. The onset and growth of the double-tearing mode significantly depend on the <span class="hlt">boundary</span> <span class="hlt">magnetic</span> perturbations, particularly in the early development stage of the mode. The influences of the <span class="hlt">magnetic</span> perturbation amplitude on the mode for different separations of the two rational surfaces are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JNuM..241..946R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JNuM..241..946R"><span><span class="hlt">Boundary</span> modelling of the stellarator Wendelstein 7-X</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Renner, H.; Strumberger, E.; Kisslinger, J.; Nührenberg, J.; Wobig, H.</p> <p>1997-02-01</p> <p>To justify the design of the divertor plates in W7-X the <span class="hlt">magnetic</span> fields of finite-β HELIAS equilibria for the so-called high-mirror case have been computed for various average β-values up to < β > = 0.04 with the NEMEC free-<span class="hlt">boundary</span> equilibrium code [S.P. Hirshman, W.I. van Rij and W.I. Merkel, Comput. Phys. Commun. 43 (1986) 143] in combination with the newly developed MFBE (<span class="hlt">magnetic</span> field solver for finite-beta equilibria) code. In a second study the unloading of the target plates by radiation was investigated. The B2 code [B.J. Braams, Ph.D. Thesis, Rijksuniversiteit Utrecht (1986)] was applied for the first time to stellarators to provide of a self-consistent modelling of the SOL including effects of neutrals and impurities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhRvL.120c1101A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhRvL.120c1101A"><span>Evaluation of the Interplanetary <span class="hlt">Magnetic</span> Field Strength Using the Cosmic-Ray Shadow of the Sun</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amenomori, M.; Bi, X. J.; Chen, D.; Chen, T. L.; Chen, W. Y.; Cui, S. W.; Danzengluobu, Ding, L. K.; Feng, C. F.; Feng, Zhaoyang; Feng, Z. Y.; Gou, Q. B.; Guo, Y. Q.; He, H. H.; He, Z. T.; Hibino, K.; Hotta, N.; Hu, Haibing; Hu, H. B.; Huang, J.; Jia, H. Y.; Jiang, L.; Kajino, F.; Kasahara, K.; Katayose, Y.; Kato, C.; Kawata, K.; Kozai, M.; Labaciren, Le, G. M.; Li, A. F.; Li, H. J.; Li, W. J.; Liu, C.; Liu, J. S.; Liu, M. Y.; Lu, H.; Meng, X. R.; Miyazaki, T.; Mizutani, K.; Munakata, K.; Nakajima, T.; Nakamura, Y.; Nanjo, H.; Nishizawa, M.; Niwa, T.; Ohnishi, M.; Ohta, I.; Ozawa, S.; Qian, X. L.; Qu, X. B.; Saito, T.; Saito, T. Y.; Sakata, M.; Sako, T. K.; Shao, J.; Shibata, M.; Shiomi, A.; Shirai, T.; Sugimoto, H.; Takita, M.; Tan, Y. H.; Tateyama, N.; Torii, S.; Tsuchiya, H.; Udo, S.; Wang, H.; Wu, H. R.; Xue, L.; Yamamoto, Y.; Yamauchi, K.; Yang, Z.; Yuan, A. F.; Yuda, T.; Zhai, L. M.; Zhang, H. M.; Zhang, J. L.; Zhang, X. Y.; Zhang, Y.; Zhang, Yi; Zhang, Ying; Zhaxisangzhu, Zhou, X. X.; Tibet AS γ Collaboration</p> <p>2018-01-01</p> <p>We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disk center in the "away" ("toward") interplanetary <span class="hlt">magnetic</span> field (IMF) <span class="hlt">sector</span>. By comparing with numerical simulations based on the solar <span class="hlt">magnetic</span> field model, we find that the average IMF strength in the away (toward) <span class="hlt">sector</span> is 1.54 ±0.21stat±0.20syst (1.62 ±0.15stat±0.22syst ) times larger than the model prediction. These demonstrate that the observed Sun's shadow is a useful tool for the quantitative evaluation of the average solar <span class="hlt">magnetic</span> field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29400499','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29400499"><span>Evaluation of the Interplanetary <span class="hlt">Magnetic</span> Field Strength Using the Cosmic-Ray Shadow of the Sun.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Amenomori, M; Bi, X J; Chen, D; Chen, T L; Chen, W Y; Cui, S W; Danzengluobu; Ding, L K; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gou, Q B; Guo, Y Q; He, H H; He, Z T; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Jia, H Y; Jiang, L; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Kozai, M; Labaciren; Le, G M; Li, A F; Li, H J; Li, W J; Liu, C; Liu, J S; Liu, M Y; Lu, H; Meng, X R; Miyazaki, T; Mizutani, K; Munakata, K; Nakajima, T; Nakamura, Y; Nanjo, H; Nishizawa, M; Niwa, T; Ohnishi, M; Ohta, I; Ozawa, S; Qian, X L; Qu, X B; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Shao, J; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, H; Wu, H R; Xue, L; Yamamoto, Y; Yamauchi, K; Yang, Z; Yuan, A F; Yuda, T; Zhai, L M; Zhang, H M; Zhang, J L; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhang, Ying; Zhaxisangzhu; Zhou, X X</p> <p>2018-01-19</p> <p>We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disk center in the "away" ("toward") interplanetary <span class="hlt">magnetic</span> field (IMF) <span class="hlt">sector</span>. By comparing with numerical simulations based on the solar <span class="hlt">magnetic</span> field model, we find that the average IMF strength in the away (toward) <span class="hlt">sector</span> is 1.54±0.21_{stat}±0.20_{syst} (1.62±0.15_{stat}±0.22_{syst}) times larger than the model prediction. These demonstrate that the observed Sun's shadow is a useful tool for the quantitative evaluation of the average solar <span class="hlt">magnetic</span> field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPA....7e6221L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPA....7e6221L"><span><span class="hlt">Magnetization</span> reversal process in (Sm, Dy, Gd) (Co, Fe, Cu, Zr)z <span class="hlt">magnets</span> with different cellular structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Lei; Liu, Zhuang; Zhang, Xin; Feng, Yanping; Wang, Chunxiao; Sun, Yingli; Lee, Don; Yan, Aru; Wu, Qiong</p> <p>2017-05-01</p> <p><span class="hlt">Magnetization</span> reversal mechanism is found to vary with cellular structures by a comparative study of the <span class="hlt">magnetization</span> processes of three (Sm, Dy, Gd) (Co, Fe, Cu, Zr)z <span class="hlt">magnets</span> with different cellular structures. Analysis of domain walls, initial <span class="hlt">magnetization</span> curves and recoil loops indicates that the morphology of cellular structure has a significant effect on the <span class="hlt">magnetization</span> process, besides the obvious connection to the difference of domain energy density between cell <span class="hlt">boundary</span> phase (CBP) and main phase. The <span class="hlt">magnetization</span> of Sample 2 (with a moderate cell size and uniformly continuous CBPs) behaves as a strong coherence domain-wall pinning effect to the domain wall and lead to a highest coercivity in the <span class="hlt">magnet</span>. The <span class="hlt">magnetization</span> of Sample 1 (with thin and discontinuous CBPs) shows an inconsistent pinning effect to the domain wall while that of Sample 3 (with thick and aggregate CBPs) exhibits a two-phase separation <span class="hlt">magnetization</span>. Both the two cases lead to lower coercivities. A simplified model is given as well to describe the relationships among cellular structure and <span class="hlt">magnetization</span> behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986JMMM...54..557H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986JMMM...54..557H"><span>The microstructure and <span class="hlt">magnetic</span> properties of melt-spun Fe 76Nd 16B 8 <span class="hlt">magnetic</span> materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hadjipanayis, G. C.; Dickenson, R. C.; Lawless, K. R.</p> <p>1986-02-01</p> <p>The origin of <span class="hlt">magnetic</span> hardening has been examined in melt-spun Fe 76Nd 16B 8 samples heat-treated at around 700°C. Microstructure studies show the same phases as in sintered <span class="hlt">magnets</span> consisting of Fe 14Nd 2B, Fe 4NdB 4 and two high-Nd content phases. These phases exist in both equiaxed and faceted crystallites of submicron size. Lorentz microscopy shows domain walls which end at grain <span class="hlt">boundaries</span> indicating that they are pinned there.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017BrJPh..47..640Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017BrJPh..47..640Z"><span>Effect of Longitudinal <span class="hlt">Magnetic</span> Field on Vibration Characteristics of Single-Walled Carbon Nanotubes in a Viscoelastic Medium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, D. P.; Lei, Y.; Shen, Z. B.</p> <p>2017-12-01</p> <p>The effect of longitudinal <span class="hlt">magnetic</span> field on vibration response of a sing-walled carbon nanotube (SWCNT) embedded in viscoelastic medium is investigated. Based on nonlocal Euler-Bernoulli beam theory, Maxwell's relations, and Kelvin viscoelastic foundation model, the governing equations of motion for vibration analysis are established. The complex natural frequencies and corresponding mode shapes in closed form for the embedded SWCNT with arbitrary <span class="hlt">boundary</span> conditions are obtained using transfer function method (TFM). The new analytical expressions for the complex natural frequencies are also derived for certain typical <span class="hlt">boundary</span> conditions and Kelvin-Voigt model. Numerical results from the model are presented to show the effects of nonlocal parameter, viscoelastic parameter, <span class="hlt">boundary</span> conditions, aspect ratio, and strength of the <span class="hlt">magnetic</span> field on vibration characteristics for the embedded SWCNT in longitudinal <span class="hlt">magnetic</span> field. The results demonstrate the efficiency of the proposed methods for vibration analysis of embedded SWCNTs under <span class="hlt">magnetic</span> field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhRvB..97n4424S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhRvB..97n4424S"><span><span class="hlt">Magnetic</span> phase diagram of a frustrated spin ladder</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sugimoto, Takanori; Mori, Michiyasu; Tohyama, Takami; Maekawa, Sadamichi</p> <p>2018-04-01</p> <p>Frustrated spin ladders show <span class="hlt">magnetization</span> plateaux depending on the rung-exchange interaction and frustration defined by the ratio of first and second neighbor exchange interactions in each chain. This paper reports on its <span class="hlt">magnetic</span> phase diagram. Using the variational matrix-product state method, we accurately determine phase <span class="hlt">boundaries</span>. Several kinds of <span class="hlt">magnetization</span> plateaux are induced by the frustration and the strong correlation among quasiparticles on a lattice. The appropriate description of quasiparticles and their relevant interactions are changed by a <span class="hlt">magnetic</span> field. We find that the frustration differentiates the triplet quasiparticle from the singlet one in kinetic energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JMP....56g1705V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JMP....56g1705V"><span><span class="hlt">Boundary</span> transfer matrices and <span class="hlt">boundary</span> quantum KZ equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vlaar, Bart</p> <p>2015-07-01</p> <p>A simple relation between inhomogeneous transfer matrices and <span class="hlt">boundary</span> quantum Knizhnik-Zamolodchikov (KZ) equations is exhibited for quantum integrable systems with reflecting <span class="hlt">boundary</span> conditions, analogous to an observation by Gaudin for periodic systems. Thus, the <span class="hlt">boundary</span> quantum KZ equations receive a new motivation. We also derive the commutativity of Sklyanin's <span class="hlt">boundary</span> transfer matrices by merely imposing appropriate reflection equations, in particular without using the conditions of crossing symmetry and unitarity of the R-matrix.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912050R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912050R"><span>Dry intrusions: Lagrangian climatology and impact on the <span class="hlt">boundary</span> layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raveh-Rubin, Shira; Wernli, Heini</p> <p>2017-04-01</p> <p>Dry air intrusions (DIs) are large-scale descending airstreams. A DI is typically referred to as a coherent airstream in the cold <span class="hlt">sector</span> of an extratropical cyclone. Emerging evidence suggests that DIs are linked to severe surface wind gusts. However, there is yet no strict Lagrangian definition of DIs, and so their climatological frequency, dynamical characteristics as well as their seasonal and spatial distributions are unknown. Furthermore, the dynamical interaction between DIs and the planetary <span class="hlt">boundary</span> layer is not fully understood. Here, we suggest a Lagrangian definition for DI air parcels, namely a minimum pressure increase along a trajectory of 400 hPa in 48 hours. Based on this criterion, the open questions are addressed by: (i) a novel global Lagrangian climatology for the ECMWF ERA-Interim reanalysis dataset for the years 1979-2014; (ii) a case study illustrating the interaction between DIs and the <span class="hlt">boundary</span> layer. We find that DIs occur predominantly in winter. DIs coherently descend from the upper troposphere (their stratospheric origin is small), to the mid- and low levels, where they mix with their environment and diverge. Different physical characteristics typify DIs in the different regions and seasons. Finally, we demonstrate the different mechanisms by which DIs can destabilize the <span class="hlt">boundary</span> layer and facilitate the formation of strong surface winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PhyE...97..250A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PhyE...97..250A"><span>Atomistic modelling of <span class="hlt">magnetic</span> nano-granular thin films</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Agudelo-Giraldo, J. D.; Arbeláez-Echeverry, O. D.; Restrepo-Parra, E.</p> <p>2018-03-01</p> <p>In this work, a complete model for studying the <span class="hlt">magnetic</span> behaviour of polycrystalline thin films at nanoscale was processed. This model includes terms as exchange interaction, dipolar interaction and various types of anisotropies. For the first term, exchange interaction dependence of the distance n was used with purpose of quantify the interaction, mainly in grain <span class="hlt">boundaries</span>. The third term includes crystalline, surface and <span class="hlt">boundary</span> anisotropies. Special attention was paid to the disorder vector that determines the loss of cubic symmetry in the crystalline structure. For the case of the dipolar interaction, a similar implementation of the fast multiple method (FMM) was performed. Using these tools, modelling and simulations were developed varying the number of grains, and the results obtained presented a great dependence of the <span class="hlt">magnetic</span> properties on this parameter. Comparisons between critical temperature and <span class="hlt">magnetization</span> of saturation depending on the number of grains were performed for samples with and without factors as the surface and <span class="hlt">boundary</span> anisotropies, and the dipolar interaction. It was observed that the inclusion of these parameters produced a decrease in the critical temperature and the <span class="hlt">magnetization</span> of saturation; furthermore, in both cases, including and not including the disorder parameters, not only the critical temperature, but also the <span class="hlt">magnetization</span> of saturation exhibited a range of values that also depend on the number of grains. This presence of a critical interval is due to each grain can transit toward the ferromagnetic state at different values of critical temperature. The processes of Zero field cooling (ZFC), Field cooling (FCC) and field cooling in warming mode (FCW) were necessary for understanding the mono-domain regime around of transition temperature, due to the high probabilities of a Super-paramagnetic (SPM) state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JGR...10124373K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JGR...10124373K"><span>The topology of intrasector reversals of the interplanetary <span class="hlt">magnetic</span> field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kahler, S. W.; Crooker, N. U.; Gosling, J. T.</p> <p>1996-11-01</p> <p>A technique has been developed recently to determine the polarities of interplanetary <span class="hlt">magnetic</span> fields relative to their origins at the Sun by comparing energetic electron flow directions with local <span class="hlt">magnetic</span> field directions. Here we use heat flux electrons from the Los Alamos National Laboratory (LANL) plasma detector on the ISEE 3 spacecraft to determine the field polarities. We examine periods within well-defined <span class="hlt">magnetic</span> <span class="hlt">sectors</span> when the field directions appear to be reversed from the normal spiral direction of the <span class="hlt">sector</span>. About half of these intrasector field reversals (IFRs) are cases in which the polarities match those of the surrounding <span class="hlt">sectors</span>, indicating that those fields have been folded back toward the Sun. The more interesting cases are those with polarity reversals. We find no clear cases of isolated reverse polarity fields, which suggests that islands of reverse polarity in the solar source dipole field probably do not exist. The IFRs with polarity reversals are strongly associated with periods of bidirectional electron flows, suggesting that those fields occur only in conjunction with closed fields. We propose that both those IFRs and the bidirectional flows are signatures of coronal mass ejections (CMEs). In that case, many interplanetary CMEs are larger and more complex than previously thought, consisting of both open and closed field components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ISPAn.II5..329W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ISPAn.II5..329W"><span><span class="hlt">Boundaries</span> and <span class="hlt">Boundary</span> Marks - Substantive Cultural Heritage of Extensive Importance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waldhaeusl, P.; Koenig, H.; Mansberger, R.</p> <p>2015-08-01</p> <p>The Austrian Society for surveying and Geoinformation (ASG) has proposed to submit "<span class="hlt">Boundaries</span> and <span class="hlt">Boundary</span> Marks" for the UNESCO World Heritage title. It was time that <span class="hlt">boundaries</span>, borders and limits of all types as well as ownership rights would find the proper attention in the global public. Landmarks symbolize the real property and the associated rights and obligations, in a figurative sense, the property generally and all legal limits. A democratic state of law is impossible at today's population density without a functioning land administration system with surveying and jurisdiction. As monumental World Heritage representatives of the geodetic artwork "<span class="hlt">Boundaries</span> and <span class="hlt">Boundary</span> Marks" are specifically proposed: remaining monuments of the original cadastral geodetic network, the first pan-Austrian surveying headquarters in Vienna, and a specific selection of outstanding <span class="hlt">boundary</span> monuments. Landmarks are monuments to the <span class="hlt">boundaries</span> which separate rights and obligations, but also connect the neighbors peacefully after written agreement. "And cursed be he who does not respect the <span class="hlt">boundaries</span>" you wrote already 3000 years ago. <span class="hlt">Boundaries</span> and <span class="hlt">Boundary</span> Marks are a real thing; they all belong to the tangible or material heritage of human history. In this context also the intangible heritage is discussed. This refers to oral tradition and expressions, performing arts; social practices, rituals and festive events; as well as to knowledge and practices handling nature and the universe. "<span class="hlt">Boundaries</span> and <span class="hlt">Boundary</span> Marks" do not belong to it, but clearly to the material cultural world heritage. "<span class="hlt">Boundary</span> and <span class="hlt">Boundary</span> Marks" is proposed to be listed according to the criteria (ii),(iv),(vi).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AnGeo..29....1P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AnGeo..29....1P"><span>Sq field characteristics at Phu Thuy, Vietnam, during solar cycle 23: comparisons with Sq field in other longitude <span class="hlt">sectors</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pham Thi Thu, H.; Amory-Mazaudier, C.; Le Huy, M.</p> <p>2011-01-01</p> <p>Quiet days variations in the Earth's <span class="hlt">magnetic</span> field (the Sq current system) are compared and contrasted for the Asian, African and American <span class="hlt">sectors</span> using a new dataset from Vietnam. This is the first presentation of the variation of the Earth's <span class="hlt">magnetic</span> field (Sq), during the solar cycle 23, at Phu Thuy, Vietnam (geographic latitudes 21.03° N and longitude: 105.95° E). Phu Thuy observatory is located below the crest of the equatorial fountain in the Asian longitude <span class="hlt">sector</span> of the Northern Hemisphere. The morphology of the Sq daily variation is presented as a function of solar cycle and seasons. The diurnal variation of Phu Thuy is compared to those obtained in different <span class="hlt">magnetic</span> observatories over the world to highlight the characteristics of the Phu Thuy observations. In other longitude <span class="hlt">sectors</span> we find different patterns. At Phu Thuy the solar cycle variation of the amplitude of the daily variation of the X component is correlated to the F.10.7 cm solar radiation (~0.74). This correlation factor is greater than the correlation factor obtained in two observatories located at the same <span class="hlt">magnetic</span> latitudes in other longitude <span class="hlt">sectors</span>: at Tamanrasset in the African <span class="hlt">sector</span> (~0.42, geographic latitude ~22.79) and San Juan in the American <span class="hlt">sector</span> (~0.03, geographic latitude ~18.38). At Phu Thuy, the Sq field exhibits an equinoctial and a diurnal asymmetry: - The seasonal variation of the monthly mean of X component exhibits the well known semiannual pattern with 2 equinox maxima, but the X component is larger in spring than in autumn. Depending of the phase of the sunspot cycle, the maximum amplitude of the X component varies in spring from 30 nT to 75 nT and in autumn from 20 nT to 60 nT. The maximum amplitude of the X component exhibits roughly the same variation in both solstices, varying from about ~20 nT to 50 nT, depending on the position into the solar cycle. - In all seasons, the mean equinoctial diurnal Y component has a morning maximum Larger than the afternoon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760046362&hterms=planetary+boundaries&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dplanetary%2Bboundaries','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760046362&hterms=planetary+boundaries&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dplanetary%2Bboundaries"><span>Depletion of solar wind plasma near a planetary <span class="hlt">boundary</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zwan, B. J.; Wolf, R. A.</p> <p>1976-01-01</p> <p>A mathematical model is presented that describes the squeezing of solar wind plasma out along interplanetary <span class="hlt">magnetic</span> field lines in the region between the bow shock and the effective planetary <span class="hlt">boundary</span> (in the case of the earth, the magnetopause). In the absence of local <span class="hlt">magnetic</span> merging the squeezing process should create a 'depletion layer', a region of very low plasma density just outside the magnetopause. Numerical solutions are obtained for the dimensionless magnetohydrodynamic equations describing this depletion process for the case where the solar wind <span class="hlt">magnetic</span> field is perpendicular to the solar wind flow direction. For the case of the earth, the theory predicts that the density should be reduced by a factor exceeding 2 in a layer about 700-1300 km thick if the Alfven Mach number in the solar wind, is equal to 8. Scaling of the model calculations to Venus and Mars suggests layer thicknesses about 1/10 and 1/15 those of the earth, respectively, neglecting diffusion and ionospheric effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..DPPNP8026C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..DPPNP8026C"><span>Transport in a field-aligned <span class="hlt">magnetized</span> plasma and neutral gas <span class="hlt">boundary</span>: the end of the plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cooper, Christopher; Gekelman, Walter</p> <p>2012-10-01</p> <p>A series of experiments at the Enormous Toroidal Plasma Device (ETPD) at UCLA study the Neutral <span class="hlt">Boundary</span> Layer (NBL) between a <span class="hlt">magnetized</span> plasma and a neutral gas in the direction of the confining field. A lanthanum hexaboride (LaB6) cathode and semi-transparent anode create a current-free, weakly ionized (ne/nn<5%), helium plasma (B˜250 G, Rplasma=10cm, ne<10^12cm^3, Te<3eV, and Ti˜Tn) that terminates on helium gas without touching any walls. Probes inserted into the plasma measure the basic plasma parameters in the NBL. The NBL begins where the plasma and neutral gas pressures equilibrate and the electrons and ions come to rest through collisions with the neutral gas. A field-aligned electric field (δφ/kTe˜1) is established self-consistently to maintain a current-free termination and dominates transport in the NBL, similar to a sheath but with a length L˜10λei˜10^2λen˜10^5λD. A two-fluid weakly-ionized transport model describes the system. A generalized Ohm's Law correctly predicts the electric field observed. The pressure balance criteria and magnitude of the termination electric field are confirmed over a scaling of parameters. The model can also be used to describe the atmospheric termination of aurora or fully detached gaseous divertors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1307437-direct-measurement-proximity-induced-magnetism-interface-between-topological-insulator-ferromagnet','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1307437-direct-measurement-proximity-induced-magnetism-interface-between-topological-insulator-ferromagnet"><span>Direct measurement of proximity-induced <span class="hlt">magnetism</span> at the interface between a topological insulator and a ferromagnet</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Lee, Changmin; Katmis, Ferhat; Jarillo-Herrero, Pablo; ...</p> <p>2016-06-27</p> <p>When a topological insulator (TI) is in contact with a ferromagnet, both time-reversal and inversion symmetries are broken at the interface. An energy gap is formed at the TI surface, and its electrons gain a net <span class="hlt">magnetic</span> moment through short-range exchange interactions. <span class="hlt">Magnetic</span> TIs can host various exotic quantum phenomena, such as massive Dirac fermions, Majorana fermions, the quantum anomalous Hall effect and chiral edge currents along the domain <span class="hlt">boundaries</span>. However, selective measurement of induced <span class="hlt">magnetism</span> at the buried interface has remained a challenge. Using <span class="hlt">magnetic</span> second-harmonic generation, we directly probe both the in-plane and out-of-plane <span class="hlt">magnetizations</span> induced at themore » interface between the ferromagnetic insulator (FMI) EuS and the three-dimensional TI Bi 2Se 3. Furthermore, our findings not only allow characterizing <span class="hlt">magnetism</span> at the TI–FMI interface but also lay the groundwork for imaging <span class="hlt">magnetic</span> domains and domain <span class="hlt">boundaries</span> at the <span class="hlt">magnetic</span> TI surfaces.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780060945&hterms=magnetic+vector+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmagnetic%2Bvector%2Bpotential','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780060945&hterms=magnetic+vector+potential&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmagnetic%2Bvector%2Bpotential"><span>Comparisons of measured and calculated potential <span class="hlt">magnetic</span> fields. [in solar corona</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hagyard, M. J.; Teuber, D.</p> <p>1978-01-01</p> <p>Photospheric line-of-sight and transverse-<span class="hlt">magnetic</span>-field data obtained, with a vector magnetograph system for an isolated sunspot are described. A study of the linear polarization patterns and of the calculated transverse field lines indicates that the <span class="hlt">magnetic</span> field of the region is very nearly potential. The H-alpha fibril structures of this region as seen in high-resolution photographs corroborate this conclusion. Consequently, a potential-field calculation is described using the measured line-of-sight fields together with assumed Neumann <span class="hlt">boundary</span> conditions; both are necessary and sufficient for a unique solution. The computed transverse fields are then compared with the measured transverse fields to verify the potential-field model and assumed <span class="hlt">boundary</span> values. The implications of these comparisons for the validity of <span class="hlt">magnetic</span>-field extrapolations using potential theory are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002560&hterms=electrons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Delectrons','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002560&hterms=electrons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Delectrons"><span>Electron-Scale Measurements of <span class="hlt">Magnetic</span> Reconnection in Space</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Burch, J. L.; Torbert, R. B.; Phan, T. D.; Chen, L.-J.; Moore, T. E.; Ergun, R. E.; Eastwood, J. P.; Gershman, D. J.; Cassak, P. A.; Argall, M. R.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20170002560'); toggleEditAbsImage('author_20170002560_show'); toggleEditAbsImage('author_20170002560_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20170002560_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20170002560_hide"></p> <p>2016-01-01</p> <p><span class="hlt">Magnetic</span> reconnection is a fundamental physical process in plasmas whereby stored <span class="hlt">magnetic</span> energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward <span class="hlt">boundary</span> of Earth's magnetosphere where the interplanetary <span class="hlt">magnetic</span> field reconnects with the terrestrial <span class="hlt">magnetic</span> field. We have (i) observed the conversion of <span class="hlt">magnetic</span> energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of <span class="hlt">magnetic</span> energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=earths+AND+outer+AND+core&id=EJ407671','ERIC'); return false;" href="https://eric.ed.gov/?q=earths+AND+outer+AND+core&id=EJ407671"><span>The Evolution of the Earth's <span class="hlt">Magnetic</span> Field.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Bloxham, Jeremy; Gubbins, David</p> <p>1989-01-01</p> <p>Describes the change of earth's <span class="hlt">magnetic</span> field at the <span class="hlt">boundary</span> between the outer core and the mantle. Measurement techniques used during the last 300 years are considered. Discusses the theories and research for explaining the field change. (YP)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH13A2029B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH13A2029B"><span>Kinetic Approaches to Shear-Driven <span class="hlt">Magnetic</span> Reconnection for Multi-Scale Modeling of CME Initiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Black, C.; Antiochos, S. K.; DeVore, C.; Germaschewski, K.; Karpen, J. T.</p> <p>2013-12-01</p> <p>In the standard model for coronal mass ejections (CME) and/or solar flares, the free energy for the event resides in the strongly sheared <span class="hlt">magnetic</span> field of a filament channel. The pre-eruption force balance, consisting of an upward force due to the <span class="hlt">magnetic</span> pressure of the sheared field balanced by a downward tension due to overlying un-sheared field, is widely believed to be disrupted by <span class="hlt">magnetic</span> reconnection. Therefore, understanding initiation of solar explosive phenomena requires a true multi-scale model of reconnection onset driven by the buildup of <span class="hlt">magnetic</span> shear. While the application of <span class="hlt">magnetic</span>-field shear is a trivial matter in MHD simulations, it is a significant challenge in a PIC code. The driver must be implemented in a self-consistent manner and with <span class="hlt">boundary</span> conditions that avoid the generation of waves that destroy the applied shear. In this work, we describe drivers for 2.5D, aperiodic, PIC systems and discuss the implementation of driver-consistent <span class="hlt">boundary</span> conditions that allow a net electric current to flow through the walls. Preliminary tests of these <span class="hlt">boundaries</span> with a MHD equilibrium are shown. This work was supported, in part, by the NASA Living With a Star TR&T Program.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSH41E..04T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSH41E..04T"><span>Embedding Circular Force-Free Flux Ropes in Potential <span class="hlt">Magnetic</span> Fields</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Titov, V. S.; Torok, T.; Mikic, Z.; Linker, J.</p> <p>2013-12-01</p> <p>We propose a method for constructing approximate force-free equilibria in active regions that locally have a potential bipolar-type <span class="hlt">magnetic</span> field with a thin force-free flux rope embedded inside it. The flux rope has a circular-arc axis and circular cross-section in which the interior <span class="hlt">magnetic</span> field is predominantly toroidal (axial). Its <span class="hlt">magnetic</span> pressure is balanced outside by that of the poloidal (azimuthal) field created at the <span class="hlt">boundary</span> by the electric current sheathing the flux rope. To facilitate the implementation of the method in our numerical magnetohydrodynamic (MHD) code, the entire solution is described in terms of the vector potential of the <span class="hlt">magnetic</span> field. The parameters of the flux rope can be chosen so that a subsequent MHD relaxation of the constructed configuration under line-tied conditions at the <span class="hlt">boundary</span> provides a numerically exact equilibrium. Such equilibria are an approximation for the <span class="hlt">magnetic</span> configuration preceding solar eruptions, which can be triggered in our model by imposing suitable photospheric flows beneath the flux rope. The proposed method is a useful tool for constructing pre-eruption <span class="hlt">magnetic</span> fields in data-driven simulations of solar active events. Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70036217','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70036217"><span>Chapter 4: Regional <span class="hlt">magnetic</span> domains of the Circum-Arctic: A framework for geodynamic interpretation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Saltus, R.W.; Miller, E.L.; Gaina, C.; Brown, P.J.</p> <p>2011-01-01</p> <p>We identify and discuss 57 <span class="hlt">magnetic</span> anomaly pattern domains spanning the Circum-Arctic. The domains are based on analysis of a new Circum-Arctic data compilation. The <span class="hlt">magnetic</span> anomaly patterns can be broadly related to general geodynamic classification of the crust into stable, deformed (<span class="hlt">magnetic</span> and nonmagnetic), deep <span class="hlt">magnetic</span> high, oceanic and large igneous province domains. We compare the <span class="hlt">magnetic</span> domains with topography/bathymetry, regional geology, regional free air gravity anomalies and estimates of the relative <span class="hlt">magnetic</span> 'thickness' of the crust. Most of the domains and their geodynamic classification assignments are consistent with their topographic/bathymetric and geological expression. A few of the domains are potentially controversial. For example, the extent of the Iceland Faroe large igneous province as identified by <span class="hlt">magnetic</span> anomalies may disagree with other definitions for this feature. Also the lack of definitive <span class="hlt">magnetic</span> expression of oceanic crust in Baffin Bay, the Norwegian-Greenland Sea and the Amerasian Basin is at odds with some previous interpretations. The <span class="hlt">magnetic</span> domains and their <span class="hlt">boundaries</span> provide clues for tectonic models and <span class="hlt">boundaries</span> within this poorly understood portion of the globe. ?? 2011 The Geological Society of London.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhLA..381.3909Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhLA..381.3909Z"><span>Effect of <span class="hlt">boundary</span> conditions on magnetocapacitance effect in a ring-type magnetoelectric structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Juanjuan</p> <p>2017-12-01</p> <p>By considering the nonlinear magneto-elastic coupling relationships of magnetostrictive materials, an analytical model is proposed. The resonance frequencies can be accurately predicted by this theoretical model, and they are in good agreement with experimental data. Subsequently, the magnetocapacitance effect in a ring-type magnetoelectric (ME) structure with different <span class="hlt">boundary</span> conditions is investigated, and it is found that various mechanical <span class="hlt">boundaries</span>, the frequency, the <span class="hlt">magnetic</span> field, the geometric size, and the interface bonding significantly affect the capacitance of the ME structure. Further, additional resonance frequencies can be predicted by considering appropriate imperfect interface bonding. Finally, the influence of an external force on the capacitance is studied. The result shows that an external force on the <span class="hlt">boundary</span> changes the capacitance, but has only a weak influence on the resonance frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999PhDT........56O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999PhDT........56O"><span>The relationship between structure and <span class="hlt">magnetic</span> properties in ultra-fine grained/nanostructured FePd alloys</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okumura, Hideyuki</p> <p></p> <p>In this study, the <span class="hlt">magnetic</span> behavior including coercivity and the <span class="hlt">magnetic</span> phase transition (ferromagnetic ↔ paramagnetic) and related phenomena were qualitatively and quantitatively investigated in ultra-fine grained/nanostructured FePd permanent <span class="hlt">magnet</span> alloys, in relation to the microstructure and defect structure, and the results were compared with bulk FePd. Most of the alloy specimens investigated were in the form of epoxybonded <span class="hlt">magnets</span> or isostatically-pressed pellets, formed from powders which were produced with high energy ball milling. Some results of thin films and ribbons produced with sputtering and melt-spinning, respectively, are also included in this thesis. Characterization of the materials was performed by using X-ray diffraction techniques with texture measurement, transmission electron microscopy with Lorentz microscopy, scanning electron microscopy with EDS analysis, optical microscopy and vibrating sample magnetometry. X-ray line broadening analysis was utilized for the quantitative characterization of the nanoscale microstructure, and it was found that the Cauchy-Gaussian profile assumption best describes the broadening data. Enhanced coercivities ˜10 times those of the bulk FePd obtained using conventional heat treatments were explained as the result of statistical (stochastic) unpinning of interaction domain walls out of the potential well at the grain <span class="hlt">boundary</span>, and there is also an additional effect ascribed to an increase of the magnetocrystalline anisotropy, which is mainly due to the metastable c/a ratio of the nanostructured ordered phase and possibly to stress anisotropy. At the same time, there is also a decrease of the coercivity for smaller grain sizes because of the "<span class="hlt">magnetically</span> soft" grain <span class="hlt">boundary</span> phase. A semi-quantitative theoretical model is proposed, which includes the effect of exchange coupling between the ordered grains. The so-called Kronmuller analysis based on the wall pinning model was self-consistent, supporting</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9160F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9160F"><span>Deciphering the <span class="hlt">magnetic</span> and mineralogical record of the Deccan Traps at the Cretaceous-Paleogene <span class="hlt">boundary</span> of the Zumaia section, Basque-Cantabric basin (Spain)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Font, Eric; Adatte, Thierry; Andrade, Mariana; Keller, Gerta; Mbabi Bitchong, André; Carvallo, Claire; Ferreira, Joana; Diogo, Zenaida; Mirão, José</p> <p>2017-04-01</p> <p>The Deccan Traps Magmatic Province coincides with the Cretaceous-Paleogene (KPg) <span class="hlt">boundary</span> and probably contributed to the associated mass extinctions by inducing rapid and abrupt climate changes, including continental and superficial seawater acidification. However, how such environmental acidification is expressed in the marine sedimentary record is still poorly constrained. Recent environmental <span class="hlt">magnetic</span> studies of the Bidart (France) and Gubbio (Italy) sections proposed new benchmarks to identify the Deccan Traps fingerprint in the marine sedimentary record, namely anomalous concentration in mercury, presence of akagenéite (a Cl-rich oxy-hydroxide forming in hyper-chlorinated and acid conditions) and the loss of detrital and biogenic magnetite by acid reductive dissolution. Here we test this scenario on the Zumaia section, Spain, a reference KPg section cropping out in the Basque-Cantabric basin. Our results confirm the presence of an iron-depleted interval located just below the KPg <span class="hlt">boundary</span>, similarly to Bidart and Gubbio, and which contains significant amounts of akaganéite grains as well as high content in mercury. These results consolidate the use of the previously cited benchmarks to identify environmental and climate changes induced by the Deccan volcanism. It also suggests that the main eruptive Deccan phase began just before the KPg extinction, reinforcing its contribution in the KPg mass extinction. Publication supported by FCT- project UID/GEO/50019/2013 - Instituto Dom Luiz</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850046161&hterms=rio+grande+sul&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drio%2Bgrande%2Bsul','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850046161&hterms=rio+grande+sul&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Drio%2Bgrande%2Bsul"><span>Relationships of a growing <span class="hlt">magnetic</span> flux region to flares</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Martin, S. F.; Bentley, R. D.; Schadee, A.; Antalova, A.; Kucera, A.; Dezso, L.; Gesztelyi, L.; Harvey, K. L.; Jones, H.; Livi, S. H. B.</p> <p>1984-01-01</p> <p>The evolution of flare sites at the <span class="hlt">boundaries</span> of major new and growing <span class="hlt">magnetic</span> flux regions within complexes of active regions has been analyzed using H-alpha images. A spectrum of possible relationships of growing flux regions to flares is described. An 'intimate' interaction between old and new flux and flare sites occurs at the <span class="hlt">boundaries</span> of their regions. Forced or 'intimidated' interaction involves new flux pushing older, lower flux density fields toward a neighboring old polarity inversion line, followed by the occurrence of a flare. In 'influential' interaction, <span class="hlt">magnetic</span> lines of force over an old polarity inversion line reconnect to new emerging flux, and a flare occurs when the <span class="hlt">magnetic</span> field overlying the filament becomes too weak to prevent its eruption. 'Inconsequential' interaction occurs when a new flux region is too small or has the wrong orientation for creating flare conditions. 'Incidental' interaction involves a flare occurring without any significant relationship to new flux regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JCoPh.231.4160A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JCoPh.231.4160A"><span><span class="hlt">Boundary</span> states at reflective moving <span class="hlt">boundaries</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Acosta Minoli, Cesar A.; Kopriva, David A.</p> <p>2012-06-01</p> <p>We derive and evaluate <span class="hlt">boundary</span> states for Maxwell's equations, the linear, and the nonlinear Euler gas-dynamics equations to compute wave reflection from moving <span class="hlt">boundaries</span>. In this study we use a Discontinuous Galerkin Spectral Element method (DGSEM) with Arbitrary Lagrangian-Eulerian (ALE) mapping for the spatial approximation, but the <span class="hlt">boundary</span> states can be used with other methods, like finite volume schemes. We present four studies using Maxwell's equations, one for the linear Euler equations, and one more for the nonlinear Euler equations. These are: reflection of light from a plane mirror moving at constant velocity, reflection of light from a moving cylinder, reflection of light from a vibrating mirror, reflection of sound from a plane wall and dipole sound generation by an oscillating cylinder in an inviscid flow. The studies show that the <span class="hlt">boundary</span> states preserve spectral convergence in the solution and in derived quantities like divergence and vorticity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1987JGR....9213472T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1987JGR....9213472T"><span>An eastward propagating compressional Pc 5 wave observed by AMPTE/CCE in the postmidnight <span class="hlt">sector</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takahashi, K.; Lopez, R. E.; McEntire, R. W.; Zanetti, L. J.; Kistler, L. M.; Ipavich, F. M.</p> <p>1987-12-01</p> <p>This paper presents a detailed analysis of a compressional Pc 5 wave observed in the postmidnight <span class="hlt">sector</span> on July 21, 1986, using data from the magnetometer, the charge-energy-mass spectrometer, and the medium-energy particle analyzer aboard the AMPTE/Charge Composition Explorer (CCE) spacecraft. The Pc 5 wave exhibited harmonically related transverse and compressional <span class="hlt">magnetic</span> oscillations, modulation of the flux of medium energy protons, and a large azimuthal wave number, i.e., properties that are similar to those of compressional Pc5 waves observed previously at geostationary orbit. The unique observations recorded by the AMPTE/CCE included the occurrence of the wave in the postmidnight <span class="hlt">sector</span>, its sunward propagation with respect to the spacecraft, and the left-handed polarization of the perturbed <span class="hlt">magnetic</span> field. In spite of the morphological uniqueness observed, the excitation of the July 21 event is considered to be due to the same type of instability as operates at geostationary orbit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPA....7e6656S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPA....7e6656S"><span><span class="hlt">Magnet</span> pole shape design for reduction of thrust ripple of slotless permanent <span class="hlt">magnet</span> linear synchronous motor with arc-shaped <span class="hlt">magnets</span> considering end-effect based on analytical method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shin, Kyung-Hun; Park, Hyung-Il; Kim, Kwan-Ho; Jang, Seok-Myeong; Choi, Jang-Young</p> <p>2017-05-01</p> <p>The shape of the <span class="hlt">magnet</span> is essential to the performance of a slotless permanent <span class="hlt">magnet</span> linear synchronous machine (PMLSM) because it is directly related to desirable machine performance. This paper presents a reduction in the thrust ripple of a PMLSM through the use of arc-shaped <span class="hlt">magnets</span> based on electromagnetic field theory. The <span class="hlt">magnetic</span> field solutions were obtained by considering end effect using a <span class="hlt">magnetic</span> vector potential and two-dimensional Cartesian coordinate system. The analytical solution of each subdomain (PM, air-gap, coil, and end region) is derived, and the field solution is obtained by applying the <span class="hlt">boundary</span> and interface conditions between the subdomains. In particular, an analytical method was derived for the instantaneous thrust and thrust ripple reduction of a PMLSM with arc-shaped <span class="hlt">magnets</span>. In order to demonstrate the validity of the analytical results, the back electromotive force results of a finite element analysis and experiment on the manufactured prototype model were compared. The optimal point for thrust ripple minimization is suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663424-magnetic-helicities-dynamo-action-magneto-rotational-turbulence','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663424-magnetic-helicities-dynamo-action-magneto-rotational-turbulence"><span><span class="hlt">Magnetic</span> Helicities and Dynamo Action in Magneto-rotational Turbulence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bodo, G.; Rossi, P.; Cattaneo, F.</p> <p></p> <p>We examine the relationship between <span class="hlt">magnetic</span> flux generation, taken as an indicator of large-scale dynamo action, and <span class="hlt">magnetic</span> helicity, computed as an integral over the dynamo volume, in a simple dynamo. We consider dynamo action driven by magneto-rotational turbulence (MRT) within the shearing-box approximation. We consider <span class="hlt">magnetically</span> open <span class="hlt">boundary</span> conditions that allow a flux of helicity in or out of the computational domain. We circumvent the problem of the lack of gauge invariance in open domains by choosing a particular gauge—the winding gauge—that provides a natural interpretation in terms of the average winding number of pairwise field lines. We usemore » this gauge precisely to define and measure the helicity and the helicity flux for several realizations of dynamo action. We find in these cases that the system as a whole does not break reflectional symmetry and that the total helicity remains small even in cases when substantial <span class="hlt">magnetic</span> flux is generated. We find no particular connection between the generation of <span class="hlt">magnetic</span> flux and the helicity or the helicity flux through the <span class="hlt">boundaries</span>. We suggest that this result may be due to the essentially nonlinear nature of the dynamo processes in MRT.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810012108','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810012108"><span>Evidence for <span class="hlt">magnetic</span> field reconnection at the Earth's magnetopause</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sonnerup, B. U. O.; Paschmann, G.; Papamastorakis, I.; Sckopke, N.; Haerendel, G.; Bame, S. J.; Asbridge, J. R.; Gosling, J. T.; Russell, C. T.</p> <p>1981-01-01</p> <p>Eleven passes of the ISEE satellites through the frontside terrestrial magnetopause were identified, where the plasma velocity in the magnetopause and <span class="hlt">boundary</span> layer was substantially larger than in the magnetosheath. The nature of the plasma flow, <span class="hlt">magnetic</span> field, and energetic particle fluxes in these regions were examined, with a view to determining whether the velocity enhancements can be explained by <span class="hlt">magnetic</span> field reconnection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PlPhR..38..439M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PlPhR..38..439M"><span>Medium-β free-<span class="hlt">boundary</span> equilibria of a quasi-isodynamic stellarator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mikhailov, M. I.; Drevlak, M.; Nührenberg, J.; Shafranov, V. D.</p> <p>2012-06-01</p> <p>Free-<span class="hlt">boundary</span> MHD equilibria with <span class="hlt">magnetic</span> surfaces in the vacuum region surrounding the plasma [E. Strumberger, Nucl. Fusion 37, 19 (1997); M. Drevlak, D. Monticello, and A. Reiman, Nucl. Fusion 45, 731 (2005)] are obtained for a quasi-isodynamic stellarator [A. A. Subbotin, M. I. Mikhailov, V. D. Shafranov et al., Nucl. Fusion 46, 921 (2006); M. I. Mikhailov, J. Nuhrenberg, and V. D. Shafranov, Plasma Phys. Rep. 35, 529 (2009)].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22047398-medium-beta-free-boundary-equilibria-quasi-isodynamic-stellarator','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22047398-medium-beta-free-boundary-equilibria-quasi-isodynamic-stellarator"><span>Medium-{beta} free-<span class="hlt">boundary</span> equilibria of a quasi-isodynamic stellarator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mikhailov, M. I.; Drevlak, M.; Nuehrenberg, J.</p> <p></p> <p>Free-<span class="hlt">boundary</span> MHD equilibria with <span class="hlt">magnetic</span> surfaces in the vacuum region surrounding the plasma [E. Strumberger, Nucl. Fusion 37, 19 (1997); M. Drevlak, D. Monticello, and A. Reiman, Nucl. Fusion 45, 731 (2005)] are obtained for a quasi-isodynamic stellarator [A. A. Subbotin, M. I. Mikhailov, V. D. Shafranov et al., Nucl. Fusion 46, 921 (2006); M. I. Mikhailov, J. Nuhrenberg, and V. D. Shafranov, Plasma Phys. Rep. 35, 529 (2009)].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14651916','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14651916"><span>Destabilizing effect of time-dependent oblique <span class="hlt">magnetic</span> field on <span class="hlt">magnetic</span> fluids streaming in porous media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>El-Dib, Yusry O; Ghaly, Ahmed Y</p> <p>2004-01-01</p> <p>The present work studies Kelvin-Helmholtz waves propagating between two <span class="hlt">magnetic</span> fluids. The system is composed of two semi-infinite <span class="hlt">magnetic</span> fluids streaming throughout porous media. The system is influenced by an oblique <span class="hlt">magnetic</span> field. The solution of the linearized equations of motion under the <span class="hlt">boundary</span> conditions leads to deriving the Mathieu equation governing the interfacial displacement and having complex coefficients. The stability criteria are discussed theoretically and numerically, from which stability diagrams are obtained. Regions of stability and instability are identified for the <span class="hlt">magnetic</span> fields versus the wavenumber. It is found that the increase of the fluid density ratio, the fluid velocity ratio, the upper viscosity, and the lower porous permeability play a stabilizing role in the stability behavior in the presence of an oscillating vertical <span class="hlt">magnetic</span> field or in the presence of an oscillating tangential <span class="hlt">magnetic</span> field. The increase of the fluid viscosity plays a stabilizing role and can be used to retard the destabilizing influence for the vertical <span class="hlt">magnetic</span> field. Dual roles are observed for the fluid velocity in the stability criteria. It is found that the field frequency plays against the constant part for the <span class="hlt">magnetic</span> field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29239355','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29239355"><span><span class="hlt">Magnetically</span> gated accretion in an accreting 'non-<span class="hlt">magnetic</span>' white dwarf.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Scaringi, S; Maccarone, T J; D'Angelo, C; Knigge, C; Groot, P J</p> <p>2017-12-13</p> <p>White dwarfs are often found in binary systems with orbital periods ranging from tens of minutes to hours in which they can accrete gas from their companion stars. In about 15 per cent of these binaries, the <span class="hlt">magnetic</span> field of the white dwarf is strong enough (at 10 6 gauss or more) to channel the accreted matter along field lines onto the <span class="hlt">magnetic</span> poles. The remaining systems are referred to as 'non-<span class="hlt">magnetic</span>', because until now there has been no evidence that they have a <span class="hlt">magnetic</span> field that is strong enough to affect the accretion dynamics. Here we report an analysis of archival optical observations of the 'non-<span class="hlt">magnetic</span>' accreting white dwarf in the binary system MV Lyrae, whose light curve displays quasi-periodic bursts of about 30 minutes duration roughly every 2 hours. The timescale and amplitude of these bursts indicate the presence of an unstable, <span class="hlt">magnetically</span> regulated accretion mode, which in turn implies the existence of <span class="hlt">magnetically</span> gated accretion, in which disk material builds up around the magnetospheric <span class="hlt">boundary</span> (at the co-rotation radius) and then accretes onto the white dwarf, producing bursts powered by the release of gravitational potential energy. We infer a surface <span class="hlt">magnetic</span> field strength for the white dwarf in MV Lyrae of between 2 × 10 4 gauss and 1 × 10 5 gauss, too low to be detectable by other current methods. Our discovery provides a new way of studying the strength and evolution of <span class="hlt">magnetic</span> fields in accreting white dwarfs and extends the connections between accretion onto white dwarfs, young stellar objects and neutron stars, for which similar <span class="hlt">magnetically</span> gated accretion cycles have been identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2813637','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2813637"><span><span class="hlt">Boundaries</span> of dreams, <span class="hlt">boundaries</span> of dreamers: thin and thick <span class="hlt">boundaries</span> as a new personality measure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hartmann, E</p> <p>1989-11-01</p> <p>Previous work by the author and his collaborators on frequent nightmare sufferers demonstrated that these people had striking personality characteristics which could be called "thin <span class="hlt">boundaries</span>" in a number of different senses. In order to measure thin and thick <span class="hlt">boundaries</span>, a 145-item questionnaire, the <span class="hlt">Boundary</span> Questionnaire, has been developed which has now been taken by over 1,000 persons. Preliminary results are presented indicating that, as predicted a priori, several new groups of nightmare sufferers and groups of art students scored usually "thin," whereas a group of naval officers had usually "thick" <span class="hlt">boundaries</span>. Overall, thinness on the <span class="hlt">Boundary</span> Questionnaire correlated highly positively (r = .40) with frequency of dream recall and also significantly (r = .16) with length of sleep.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3026013','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3026013"><span>Three-dimensional multiexcitation magnetoacoustic tomography with <span class="hlt">magnetic</span> induction</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Xu; Mariappan, Leo; He, Bin</p> <p>2010-01-01</p> <p>Magnetoacoustic tomography with <span class="hlt">magnetic</span> induction (MAT-MI) is a hybrid imaging modality proposed to image electrical conductivity contrast of biological tissue with high spatial resolution. This modality combines <span class="hlt">magnetic</span> excitations with ultrasound detection through the Lorentz force based coupling mechanism. However, previous studies have shown that MAT-MI method with single type of <span class="hlt">magnetic</span> excitation can only reconstruct the conductivity <span class="hlt">boundaries</span> of a sample. In order to achieve more complete conductivity contrast reconstruction, we proposed a multiexcitation MAT-MI approach. In this approach, multiple <span class="hlt">magnetic</span> excitations using different coil configurations are applied to the object sequentially and ultrasonic signals corresponding to each excitation are collected for conductivity image reconstruction. In this study, we validate the new multiexcitation MAT-MI method for three-dimensional (3D) conductivity imaging through both computer simulations and phantom experiments. 3D volume data are obtained by utilizing acoustic focusing and cylindrical scanning under each <span class="hlt">magnetic</span> excitation. It is shown in our simulation and experiment results that with a common ultrasound probe that has limited bandwidth we are able to correctly reconstruct the 3D relative conductivity contrast of the imaging object. As compared to those conductivity <span class="hlt">boundary</span> images generated by previous single-excitation MAT-MI, the new multiexcitation MAT-MI method provides more complete conductivity contrast reconstruction, and therefore, more valuable information in possible clinical and research applications. PMID:21267084</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110007826','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110007826"><span>The Origins of <span class="hlt">Magnetic</span> Structure in the Corona and Wind</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Antiochos, Spiro K.</p> <p>2010-01-01</p> <p>One of the most important and most puzzling features of the coronal <span class="hlt">magnetic</span> field is that it appears to have smooth <span class="hlt">magnetic</span> structure with little evidence for non-potentiality except at two special locations: photospheric polarity inversions lines. (non-potentiality observed as a filament channel) and coronal hole <span class="hlt">boundaries</span>, (observed as the slow solar wind). This characteristic feature of the closed-field corona is highly unexpected given that its <span class="hlt">magnetic</span> field is continuously tangled by photospheric motions. Although reconnection can eliminate some of the injected structure, it cannot destroy the helicity, which should build up to produce observable complexity. I propose that an inverse cascade process transports the injected helicity from the interior of closed flux regions to their <span class="hlt">boundaries</span> inversion lines and coronal holes, creating both filament channels and the slow wind. We describe how the helicity is injected and transported and calculate the relevant rates. I argue that one process, helicity transport, can explain both the observed lack and presence of structure in the coronal <span class="hlt">magnetic</span> field. This work has been supported by the NASA HTP, SR&T, and LWS programs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770060049&hterms=method+magnetic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmethod%2Bmagnetic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770060049&hterms=method+magnetic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmethod%2Bmagnetic"><span>The mean <span class="hlt">magnetic</span> field of the sun - Method of observation and relation to the interplanetary <span class="hlt">magnetic</span> field</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scherrer, P. H.; Wilcox, J. M.; Kotov, V.; Severnyi, A. B.; Howard, R.</p> <p>1977-01-01</p> <p>The mean solar <span class="hlt">magnetic</span> field as measured in integrated light has been observed since 1968. Since 1970 it has been observed both at Hale Observatories and at the Crimean Astrophysical Observatory. The observing procedures at both observatories and their implications for mean field measurements are discussed. A comparison of the two sets of daily observations shows that similar results are obtained at both observatories. A comparison of the mean field with the interplanetary <span class="hlt">magnetic</span> polarity shows that the IMF <span class="hlt">sector</span> structure has the same pattern as the mean field polarity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005JMMM..289..415K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005JMMM..289..415K"><span>The DC dielectric breakdown strength of <span class="hlt">magnetic</span> fluids based on transformer oil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kopčanský, Peter; Tomčo, Ladislav; Marton, Karol; Koneracká, Martina; Timko, Milan; Potočová, Ivana</p> <p>2005-03-01</p> <p>The DC dielectric breakdown strength of <span class="hlt">magnetic</span> fluids based on transformer oil TECHNOL US 4000, with different saturation <span class="hlt">magnetizations</span>, was investigated in various orientations of external <span class="hlt">magnetic</span> field. It was shown that the dielectric breakdown strength in H∣∣ E is strongly influenced by the aggregation effects. As a <span class="hlt">boundary</span> volume concentration of <span class="hlt">magnetic</span> particles, below which the <span class="hlt">magnetic</span> fluids have better dielectric properties than pure transformer oil, the volume concentration Φ=0.01 was found. Thus <span class="hlt">magnetic</span> fluids with Φ<0.01 are suitable for the use as a high-voltage insulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1364417-enhanced-conductivity-orthorhombicrhombohedral-phase-boundaries-bifeo3-thin-films','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1364417-enhanced-conductivity-orthorhombicrhombohedral-phase-boundaries-bifeo3-thin-films"><span>Enhanced conductivity at orthorhombic–rhombohedral phase <span class="hlt">boundaries</span> in BiFeO 3 thin films</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Heo, Yooun; Lee, Jin Hong; Xie, Lin; ...</p> <p>2016-08-26</p> <p>Enhanced properties in modern functional materials can often be found at structural transition regions, such as morphotropic phase <span class="hlt">boundaries</span> (MPB), owing to the coexistence of multiple phases with nearly equivalent energies. Strain-engineered MPBs have emerged in epitaxially grown BiFeO 3 (BFO) thin films by precisely tailoring a compressive misfit strain, leading to numerous intriguing phenomena, such as a massive piezoelectric response, magnetoelectric coupling, interfacial <span class="hlt">magnetism</span> and electronic conduction. Recently, an orthorhombic–rhombohedral (O–R) phase <span class="hlt">boundary</span> has also been found in tensile-strained BFO. In this study, we characterise the crystal structure and electronic properties of the two competing O and R phasesmore » using X-ray diffraction, scanning probe microscope and scanning transmission electron microscopy (STEM). We observe the temperature evolution of R and O domains and find that the domain <span class="hlt">boundaries</span> are highly conductive. Temperature-dependent measurements reveal that the conductivity is thermally activated for R–O <span class="hlt">boundaries</span>. STEM observations point to structurally wide <span class="hlt">boundaries</span>, significantly wider than in other systems. Furthermore, we reveal a strong correlation between the highly conductive domain <span class="hlt">boundaries</span> and structural material properties. These findings provide a pathway to use phase <span class="hlt">boundaries</span> in this system for novel nanoelectronic applications.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JMMM..437...62T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JMMM..437...62T"><span>Nanocomposite Nd-Y-Fe-B-Mo bulk <span class="hlt">magnets</span> prepared by injection casting technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tao, Shan; Ahmad, Zubair; Zhang, Pengyue; Yan, Mi; Zheng, Xiaomei</p> <p>2017-09-01</p> <p>The phase composition, <span class="hlt">magnetic</span> and microstructural properties of Nd2Fe14B/(α-Fe, Fe3B) nanocomposite <span class="hlt">magnets</span> produced by injection casting technique have been studied. <span class="hlt">Magnetic</span> hysteresis loop of the Nd7Y6Fe61B22Mo4 permanent <span class="hlt">magnet</span> demonstrates the coercivity as high as 1289 kA/m. Electron microscopy elucidates a microstructure composed of <span class="hlt">magnetically</span> soft α-Fe, Fe3B and hard Nd2Fe14B/Y2Fe14B nanograins (20-50 nm) separated by ultra-thin grain <span class="hlt">boundary</span> layer. The Henkel plot curve of the Nd7Y6Fe61B22Mo4 <span class="hlt">magnet</span> yields the existence of exchange coupling interactions between soft and hard phases. Macroscopically large size sheet <span class="hlt">magnet</span> is obtained due to high glass forming ability of the Nd7Y6Fe61B22Mo4 alloy derived from large atomic radius mismatch and negative enthalpy of alloy constituent elements. The high coercivity of the <span class="hlt">magnet</span> is attributed to the <span class="hlt">magnetically</span> hard phase increment, nucleation of reverse domains and the presence of thin grain <span class="hlt">boundary</span> phase. Good <span class="hlt">magnetic</span> properties such as remanence of 0.51 T, coercivity of 1289 kA/m and maximum energy product of 46.2 kJ/m3 are obtained in directly casted Nd7Y6Fe61B22Mo4 sheet <span class="hlt">magnets</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22454443-sakiadis-flow-maxwell-fluid-considering-magnetic-field-convective-boundary-conditions','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22454443-sakiadis-flow-maxwell-fluid-considering-magnetic-field-convective-boundary-conditions"><span>Sakiadis flow of Maxwell fluid considering <span class="hlt">magnetic</span> field and convective <span class="hlt">boundary</span> conditions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mustafa, M., E-mail: meraj-mm@hotmail.com; Khan, Junaid Ahmad; Hayat, T.</p> <p>2015-02-15</p> <p>In this paper we address the flow of Maxwell fluid due to constantly moving flat radiative surface with convective condition. The flow is under the influence of non-uniform transverse <span class="hlt">magnetic</span> field. The velocity and temperature distributions have been evaluated numerically by shooting approach. The solution depends on various interesting parameters including local Deborah number De, <span class="hlt">magnetic</span> field parameter M, Prandtl number Pr and Biot number Bi. We found that variation in velocity with an increase in local Deborah number De is non-monotonic. However temperature is a decreasing function of local Deborah number De.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1113158V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1113158V"><span>Comparing the solar <span class="hlt">magnetic</span> field in the corona and in the inner heliosphere during solar cycles 21-23</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Virtanen, I. I.; Mursula, K.</p> <p>2009-04-01</p> <p>We compare the open solar <span class="hlt">magnetic</span> field estimated by the PFSS model based on the WSO photospheric field observations, with the inner heliospheric <span class="hlt">magnetic</span> field. We trace the observed radial HMF into the coronal PFSS <span class="hlt">boundary</span> at 2.5 solar radii using the observed solar wind velocity, and determine the PFSS model field at the line-of-sight footpoint. Comparing the two field values, we calculate the power n of the apparent decrease of the radial field. According to expectations based on Maxwell's equations, also reproduced by Parker's HMF model, the radial HMF field should decrease with n=2. However, comparison gives considerably lower values of n, indicating the effect of HCS in the PFSS model and the possible superexpansion. The n values vary with solar cycle, being roughly 1.3-1.4 at minima and about 1.7 at maxima. Interestingly, the n values for the two HMF <span class="hlt">sectors</span> show systematic differences in the late declining to minimum phase, with smaller n values for the HMF <span class="hlt">sector</span> dominant in the northern hemisphere. This is in agreement with the smaller field value in the northern hemisphere and the southward shifted HCS, summarized by the concept of the bashful ballerina. We also find that the values of n during the recent years, in the late declining phase of solar cycle 23, are significantly larger than during the same phase of the previous cycles. This agrees with the exceptionally large tilt of the solar dipole at the end of cycle 23. We also find that the bashful ballerina appears even during SC 23 but the related hemispheric differences are smaller than during the previous cycles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940007747&hterms=geomagnetic+reversal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeomagnetic%2Breversal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940007747&hterms=geomagnetic+reversal&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgeomagnetic%2Breversal"><span>Polarity reversals and tilt of the Earth's <span class="hlt">magnetic</span> dipole</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dolginov, A. Z.</p> <p>1993-01-01</p> <p>There is evidence that the terrestrial <span class="hlt">magnetic</span> field is connected with the Earth's mantle: (1) there are <span class="hlt">magnetic</span> anomalies that do not take part in the westward drift of the main field, but are fixed with respect to the mantle; (2) the geomagnetic pole position flips in a particular way by preferred meridional paths during a reversal; and (3) <span class="hlt">magnetic</span> polarity reversals are correlated with the activations of geological processes. These facts may be explained if we take into account that a significant horizontal temperature gradient can exist in the top levels of the liquid core because of the different thermoconductivity of the different areas of the core-mantle <span class="hlt">boundary</span>. These temperature inhomogeneities can penetrate the core because fluxes along the core <span class="hlt">boundary</span> (the thermal wind) can be strongly suppressed by a small redistribution of the chemical composition in the top of the core. The nonparallel gradients of the temperature, density, and composition on the top of the core create a curled electric field that produces a current and a <span class="hlt">magnetic</span> field. This seed-field can be amplified by motions in the core. The resulting field does not forget the seed-field distribution and in this way the field on the Earth surface (that can be created only in regions with high conductivity, i.e. in the core) is connected with the core-mantle <span class="hlt">boundary</span>. Contrary to the usual approach to the dynamo problem, we will take into account that the seed field of thermoelectric origin is acting not only at some initial moment of time but permanently.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JNR....20..130S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JNR....20..130S"><span>Application of biomolecular recognition via <span class="hlt">magnetic</span> nanoparticle in nanobiotechnology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Wei-Zheng; Cetinel, Sibel; Montemagno, Carlo</p> <p>2018-05-01</p> <p>The marriage of biomolecular recognition and <span class="hlt">magnetic</span> nanoparticle creates tremendous opportunities in the development of advanced technology both in academic research and in industrial <span class="hlt">sectors</span>. In this paper, we review current progress on the <span class="hlt">magnetic</span> nanoparticle-biomolecule hybrid systems, particularly employing the recognition pairs of DNA-DNA, DNA-protein, protein-protein, and protein-inorganics in several nanobiotechnology application areas, including molecular biology, diagnostics, medical treatment, industrial biocatalysts, and environmental separations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AIPC..911..400K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AIPC..911..400K"><span>Fast Conformal Thermal Ablation in the Prostate with Transurethral Multi-<span class="hlt">Sectored</span> Ultrasound Devices and MR Guidance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kinsey, Adam M.; Diederich, Chris J.; Nau, William H.; Ross, Anthony B.; Pauly, Kim Butts; Rieke, Viola; Sommer, Graham</p> <p>2007-05-01</p> <p>Transurethral ultrasound applicators incorporating an array of multisectored tubular transducers were evaluated in theoretical simulations and in vivo canine prostates under MR guidance as a method for fast, conformal thermal therapy of the prostate. Comprehensive simulations with a biothermal model investigated the effect on lesion creation of <span class="hlt">sector</span> size, perfusion, treatment time, rectal cooling, prostate target dimensions, and feedback controller parameters (maximum temperature, pilot points at <span class="hlt">boundary</span>, update times). In vivo canine prostates (n = 4) were treated with trisectored ultrasound transducers (3 mm OD) under MR temperature monitoring to contour the ablation zone (>52 C for 1-2 min) to the <span class="hlt">boundary</span> of the prostate. Contiguous thermal lesions extended 2 cm in radius from the urethra in less than 15 min and independent <span class="hlt">sector</span> control simultaneously allowed for conformal treatment in the angular dimension. Experiments investigated sequential translation of the transducer assembly within the catheter for tailoring heat treatments to different partitions in the prostate (base, apex) without changing the initial setup. This treatment method offered greater lesion shape control in three dimensions and slightly lengthened the overall treatment time. The MR temperature images correlated with post-treatment histology and accurately controlled the heating to the target <span class="hlt">boundary</span>. MR-based control of transurethral ultrasound devices appeared more practical with multisectored transducers compared to rotating curvilinear and planar applicators due to less stringent requirements on spatial and temporal MR parameters. This study demonstrated the applicability of these devices in the prostate for anterior-lateral BPH treatment, and whole gland or quadrant target volumes for cancer treatment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.T13C2215C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.T13C2215C"><span>Continuation, south of Oaxaca City (southern Mexico) of the Oaxaca-Juarez terrane <span class="hlt">boundary</span> and of the Oaxaca Fault. Based in MT, gravity and <span class="hlt">magnetic</span> studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Campos-Enriquez, J. O.; Corbo, F.; Arzate-Flores, J.; Belmonte-Jimenez, S.; Arango-Galván, C.</p> <p>2010-12-01</p> <p>The Oaxaca Fault represents Tertiary extensional reactivation of the Juarez shear zone constituting the <span class="hlt">boundary</span>-suture between the Oaxaca and Juarez terranes (southern Mexico). South of Oaxaca City, the fault trace disappears and there are not clear evidences for its southward continuation at depth. The crust in southern México has been studied through seismic refraction, and seismological and magnetotelluric (MT) studies. The refraction studies did not image the Oaxaca Fault. However, previous regional MT studies suggest that the Oaxaca-Juarez terrane <span class="hlt">boundary</span> lies to the east of the Zaachila and Mitla sub-basins, which implies sinistral displacement along the Donaji Fault. Campos-Enriquez et al. (2009) established the shallow structure of the Oaxaca-Juarez terrane <span class="hlt">boundary</span> based in detailed gravity and <span class="hlt">magnetic</span> studies. This study enabled: 1) to establish the shallow structure of the composite depression comprising three N-S sub-basins: the northern Etla and southern Zaachila sub-basins separated by the Atzompa sub-basin. According to the Oaxaca-Juarez terrane <span class="hlt">boundary</span> is displaced sinistrally ca. 20 km along the E-W Donají Fault, which defines the northern <span class="hlt">boundary</span> of the Zaachila sub-basin. At the same time,, the Oaxaca Fault may either continue unbroken southwards along the western margin of a horst in the Zaachila sub-basin or be offset along with the terrane <span class="hlt">boundary</span>. This model implies that originally the suture was continuous south of the Donaji Fault. A constraint for the accreation of the Oaxaca and Juarez terranes. Thirty MT soundings were done in the area of the Central Valleys, Oaxaca City (southern Mexico). In particular we wanted to image the possible southward continuation of the Oaxaca Fault. 22 Mt sounding are located along two NE-SW profiles to the northern and to the south of the City of Oaxaca. To the north of Oaxaca City, the electrical resistivity distribution obtained show a clear discontinuity across the superficial trace of the Oaxaca</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750004795','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750004795"><span>On the use of Godhavn H-component as an indicator of the interplanetary <span class="hlt">sector</span> polarity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Svalgaard, L.</p> <p>1974-01-01</p> <p>An objective method of inferring the polarity of the interplanetary <span class="hlt">magnetic</span> field using the H-component at Godhavn is presented. The objectively inferred polarities are compared with a subjective index inferred earlier. It is concluded that no significant difference exists between the two methods. The inferred polarities derived from Godhavn H is biased by the (slp) sub q signature in the sense that during summer prolonged intervals of geomagnetic calm will result in inferred Away polarity regardless of the actual <span class="hlt">sector</span> polarity. This bias does not significantly alter the large scale structure of the inferred <span class="hlt">sector</span> structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930037356&hterms=earths+outer+core&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dearths%2Bouter%2Bcore','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930037356&hterms=earths+outer+core&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dearths%2Bouter%2Bcore"><span>The steady part of the secular variation of the Earth's <span class="hlt">magnetic</span> field</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bloxham, Jeremy</p> <p>1992-01-01</p> <p>The secular variation of the Earth's <span class="hlt">magnetic</span> field results from the effects of <span class="hlt">magnetic</span> induction in the fluid outer core and from the effects of <span class="hlt">magnetic</span> diffusion in the core and the mantle. Adequate observations to map the <span class="hlt">magnetic</span> field at the core-mantle <span class="hlt">boundary</span> extend back over three centuries, providing a model of the secular variation at the core-mantle <span class="hlt">boundary</span>. Here we consider how best to analyze this time-dependent part of the field. To calculate steady core flow over long time periods, we introduce an adaptation of our earlier method of calculating the flow in order to achieve greater numerical stability. We perform this procedure for the periods 1840-1990 and 1690-1840 and find that well over 90 percent of the variance of the time-dependent field can be explained by simple steady core flow. The core flows obtained for the two intervals are broadly similar to each other and to flows determined over much shorter recent intervals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPJWC..6405008B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPJWC..6405008B"><span><span class="hlt">Boundary</span> Between Stable and Unstable Regimes of Accretion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blinova, A. A.; Lovelace, R. V. E.; Romanova, M. M.</p> <p>2014-01-01</p> <p>We investigated the <span class="hlt">boundary</span> between stable and unstable regimes of accretion and its dependence on different parameters. Simulations were performed using a "cubed sphere" code with high grid resolution (244 grid points in the azimuthal direction), which is twice as high as that used in our earlier studies. We chose a very low viscosity value, with alpha-parameter α=0.02. We observed from the simulations that the <span class="hlt">boundary</span> strongly depends on the ratio between magnetospheric radius rm (where the <span class="hlt">magnetic</span> stress in the magnetosphere matches the matter stress in the disk) and corotation radius rcor (where the Keplerian velocity in the disk is equal to the angular velocity of the star). For a small misalignment angle of the dipole field, Θ = 5°, accretion is unstable if rcor/rm> 1.35, and is stable otherwise. In cases of a larger misalignment angle of the dipole, Θ = 20°, instability occurs at slightly larger values, rcor/rm> 1.41</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940016316&hterms=Steiner&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSteiner','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940016316&hterms=Steiner&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DSteiner"><span>Two-polarity <span class="hlt">magnetization</span> in the Manson impact breccia</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Steiner, M. B.; Shoemaker, E. M.</p> <p>1993-01-01</p> <p>A preliminary paleomagnetic study of the impact breccia matrix and clasts has produced surprising results--nearly antipodal normal and reversed polarity <span class="hlt">magnetic</span> vectors are observed in different portions of the core. Near-antipodal <span class="hlt">magnetizations</span> within a segment of matrix and within individual samples rule out core inversion as the explanation of the dual polarity. In both the dense and the sandy matrix breccias, the <span class="hlt">magnetizations</span> of clasts and matrix within the same core segment are identical; this negative 'conglomerate test' indicates that <span class="hlt">magnetization</span> originated after impact. Paleomagnetic study of the Manson Impact Structure is an attempt to refine the Ar-40/Ar-39 age (65.7 +/- 1 m.y.) that suggests Manson to be a Cretaceous-Tertiary <span class="hlt">boundary</span> impact. Refinement is possible because the <span class="hlt">boundary</span> occurs within a reversed polarity interval (29R) of only 0.5 m.y. duration. The two breccia types in the Manson structure were both examined: one of a very dense matrix and apparently partially melted, and the breccia stratigraphically below it of granular or 'sandy' chloritic matrix. Samples were taken from the matrixes and a wide variety of clast compositions, including granite, diabase, gneiss, amphibolite, and melted granite. Currently, measurements have been made on 22 samples, using 30-35 steps of either alternating field (AF) or thermal demagnetization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1187967-radio-frequency-sheaths-oblique-magnetic-field','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1187967-radio-frequency-sheaths-oblique-magnetic-field"><span>Radio frequency sheaths in an oblique <span class="hlt">magnetic</span> field</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Myra, James R.; D'Ippolito, Daniel A.</p> <p>2015-06-01</p> <p>The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a <span class="hlt">magnetic</span> field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent <span class="hlt">magnetic</span> presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the <span class="hlt">magnetization</span> and mobility of the ions is determined by the <span class="hlt">magnetic</span> field strength, and wave frequency, respectively. The angle, θ assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numericallymore » to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath <span class="hlt">boundary</span> condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath <span class="hlt">boundary</span> condition models. The resistive part contributes to parasitic power dissipation at the wall.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018RSPTA.37670301C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018RSPTA.37670301C"><span>Transmission of climate risks across <span class="hlt">sectors</span> and borders</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Challinor, Andy J.; Adger, W. Neil; Benton, Tim G.; Conway, Declan; Joshi, Manoj; Frame, Dave</p> <p>2018-06-01</p> <p>Systemic climate risks, which result from the potential for cascading impacts through inter-related systems, pose particular challenges to risk assessment, especially when risks are transmitted across <span class="hlt">sectors</span> and international <span class="hlt">boundaries</span>. Most impacts of climate variability and change affect regions and jurisdictions in complex ways, and techniques for assessing this transmission of risk are still somewhat limited. Here, we begin to define new approaches to risk assessment that can account for transboundary and trans-<span class="hlt">sector</span> risk transmission, by presenting: (i) a typology of risk transmission that distinguishes clearly the role of climate versus the role of the social and economic systems that distribute resources; (ii) a review of existing modelling, qualitative and systems-based methods of assessing risk and risk transmission; and (iii) case studies that examine risk transmission in human displacement, food, water and energy security. The case studies show that policies and institutions can attenuate risks significantly through cooperation that can be mutually beneficial to all parties. We conclude with some suggestions for assessment of complex risk transmission mechanisms: use of expert judgement; interactive scenario building; global systems science and big data; innovative use of climate and integrated assessment models; and methods to understand societal responses to climate risk. These approaches aim to inform both research and national-level risk assessment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890012020','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890012020"><span>Impact and extinction signatures in complete Cretaceous-Tertiary (K-T) <span class="hlt">boundary</span> sections</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smit, J.; Groot, H.; Dejonge, R.; Smit, P.</p> <p>1988-01-01</p> <p>The Zumaya, Caravaca and Agost sections in Spain, the El Kef section in Tunisia and the Negev (Nahal Avdat) sections in Israel are among the most continuous, expanded and complete K-T <span class="hlt">boundary</span> sections. The distribution patterns of the planktic faunas were quantitatively analyzed in closely spaced samples across the K-T <span class="hlt">boundary</span> in these sections, in conjuction with the geochemistry, stable isotopes, mineralogy and magnetostratigraphy. Three hundred foraminiferal specimens were randomly selected and determined. Reliable estimates for the foraminiferal productivity changes across the K-T <span class="hlt">boundary</span> and for the 1 to 2 Ma interval preceding the K-T <span class="hlt">boundary</span> were made from the numbers of individuals/gram of sediment corrected for the sedimentation rates (calculated from <span class="hlt">magnetic</span> reversals and lithology). No gradual or stepwise extinction is seen below the K-T <span class="hlt">boundary</span> nor any productivity decrease. Stable isotope analyses show a warming just after deposition of the ejecta layer, not cooling as predicted by nuclear winter scenarios, although the duration of such cooling may be too short to be observed even in these complete sections. Low REE values and cpx spherules with quench textures idential to quench-textures in diagenetically altered spherules, strongly indicate an oceanic site of (one of) the impactor(s).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663504-tev-cosmic-ray-anisotropy-from-magnetic-field-heliospheric-boundary','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663504-tev-cosmic-ray-anisotropy-from-magnetic-field-heliospheric-boundary"><span>TeV Cosmic-Ray Anisotropy from the <span class="hlt">Magnetic</span> Field at the Heliospheric <span class="hlt">Boundary</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>López-Barquero, V.; Xu, S.; Desiati, P.</p> <p></p> <p>We performed numerical calculations to test the suggestion by Desiati and Lazarian that the anisotropies of TeV cosmic rays may arise from their interactions with the heliosphere. For this purpose, we used a <span class="hlt">magnetic</span> field model of the heliosphere and performed direct numerical calculations of particle trajectories. Unlike earlier papers testing the idea, we did not employ time-reversible techniques that are based on Liouville’s theorem. We showed numerically that for scattering by the heliosphere, the conditions of Liouville’s theorem are not satisfied, and the adiabatic approximation and time-reversibility of the particle trajectories are not valid. Our results indicate sensitivity tomore » the <span class="hlt">magnetic</span> structure of the heliospheric <span class="hlt">magnetic</span> field, and we expect that this will be useful for probing this structure in future research.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ApJ...853...35T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ApJ...853...35T"><span>Effect of <span class="hlt">Magnetic</span> Twist on Nonlinear Transverse Kink Oscillations of Line-tied <span class="hlt">Magnetic</span> Flux Tubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Terradas, J.; Magyar, N.; Van Doorsselaere, T.</p> <p>2018-01-01</p> <p><span class="hlt">Magnetic</span> twist is thought to play an important role in many structures of the solar atmosphere. One of the effects of twist is to modify the properties of the eigenmodes of <span class="hlt">magnetic</span> tubes. In the linear regime standing kink solutions are characterized by a change in polarization of the transverse displacement along the twisted tube. In the nonlinear regime, <span class="hlt">magnetic</span> twist affects the development of shear instabilities that appear at the tube <span class="hlt">boundary</span> when it is oscillating laterally. These Kelvin–Helmholtz instabilities (KHI) are produced either by the jump in the azimuthal component of the velocity at the edge of the sharp <span class="hlt">boundary</span> between the internal and external part of the tube or by the continuous small length scales produced by phase mixing when there is a smooth inhomogeneous layer. In this work the effect of twist is consistently investigated by solving the time-dependent problem including the process of energy transfer to the inhomogeneous layer. It is found that twist always delays the appearance of the shear instability, but for tubes with thin inhomogeneous layers the effect is relatively small for moderate values of twist. On the contrary, for tubes with thick layers, the effect of twist is much stronger. This can have some important implications regarding observations of transverse kink modes and the KHI itself.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70012680','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70012680"><span>The complex variable <span class="hlt">boundary</span> element method: Applications in determining approximative <span class="hlt">boundaries</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hromadka, T.V.</p> <p>1984-01-01</p> <p>The complex variable <span class="hlt">boundary</span> element method (CVBEM) is used to determine approximation functions for <span class="hlt">boundary</span> value problems of the Laplace equation such as occurs in potential theory. By determining an approximative <span class="hlt">boundary</span> upon which the CVBEM approximator matches the desired constant (level curves) <span class="hlt">boundary</span> conditions, the CVBEM is found to provide the exact solution throughout the interior of the transformed problem domain. Thus, the acceptability of the CVBEM approximation is determined by the closeness-of-fit of the approximative <span class="hlt">boundary</span> to the study problem <span class="hlt">boundary</span>. ?? 1984.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1254743-study-energy-conversion-partitioning-magnetic-reconnection-layer-laboratory-plasma','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1254743-study-energy-conversion-partitioning-magnetic-reconnection-layer-laboratory-plasma"><span>Study of energy conversion and partitioning in the <span class="hlt">magnetic</span> reconnection layer of a laboratory plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Yamada, Masaaki; Yoo, Jongsoo; Jara-Almonte, Jonathan; ...</p> <p>2015-05-15</p> <p>The most important feature of <span class="hlt">magnetic</span> reconnection is that it energizes plasma particles by converting <span class="hlt">magnetic</span> energy to particle energy, the exact mechanisms by which this happens are yet to be determined despite a long history of reconnection research. Recently, we have reported our results on the energy conversion and partitioning in a laboratory reconnection layer in a short communication [Yamada et al., Nat. Commun. 5, 4474 (2014)]. The present paper is a detailed elaboration of this report together with an additional dataset with different <span class="hlt">boundary</span> sizes. Our experimental study of the reconnection layer is carried out in the two-fluidmore » physics regime where ions and electrons move quite differently. We have observed that the conversion of <span class="hlt">magnetic</span> energy occurs across a region significantly larger than the narrow electron diffusion region. A saddle shaped electrostatic potential profile exists in the reconnection plane, and ions are accelerated by the resulting electric field at the separatrices. These accelerated ions are then thermalized by re-<span class="hlt">magnetization</span> in the downstream region. A quantitative inventory of the converted energy is presented in a reconnection layer with a well-defined, variable <span class="hlt">boundary</span>. We also carried out a systematic study of the effects of <span class="hlt">boundary</span> conditions on the energy inventory. This study concludes that about 50% of the inflowing <span class="hlt">magnetic</span> energy is converted to particle energy, 2/3 of which is ultimately transferred to ions and 1/3 to electrons. When assisted by another set of <span class="hlt">magnetic</span> reconnection experiment data and numerical simulations with different sizes of monitoring box, it is also observed that the observed features of energy conversion and partitioning do not depend on the size of monitoring <span class="hlt">boundary</span> across the range of sizes tested from 1.5 to 4 ion skin depths.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22181528','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22181528"><span>Model of driven and decaying <span class="hlt">magnetic</span> turbulence in a cylinder.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kemel, Koen; Brandenburg, Axel; Ji, Hantao</p> <p>2011-11-01</p> <p>Using mean-field theory, we compute the evolution of the <span class="hlt">magnetic</span> field in a cylinder with outer perfectly conducting <span class="hlt">boundaries</span> and imposed axial <span class="hlt">magnetic</span> and electric fields. The thus injected <span class="hlt">magnetic</span> helicity in the system can be redistributed by <span class="hlt">magnetic</span> helicity fluxes down the gradient of the local current helicity of the small-scale <span class="hlt">magnetic</span> field. A weak reversal of the axial <span class="hlt">magnetic</span> field is found to be a consequence of the <span class="hlt">magnetic</span> helicity flux in the system. Such fluxes are known to alleviate so-called catastrophic quenching of the α effect in astrophysical applications. A stronger field reversal can be obtained if there is also a significant kinetic α effect. Application to the reversed field pinch in plasma confinement devices is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22383260','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22383260"><span>Cyclical absenteeism among private <span class="hlt">sector</span>, public <span class="hlt">sector</span> and self-employed workers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pfeifer, Christian</p> <p>2013-03-01</p> <p>This research note analyzes differences in the number of absent working days and doctor visits and in their cyclicality between private <span class="hlt">sector</span>, public <span class="hlt">sector</span> and self-employed workers. For this purpose, I used large-scale German survey data for the years 1995 to 2007 to estimate random effects negative binomial (count data) models. The main findings are as follows. (i) Public <span class="hlt">sector</span> workers have on average more absent working days than private <span class="hlt">sector</span> and self-employed workers. Self-employed workers have fewer absent working days and doctor visits than dependent employed workers. (ii) The regional unemployment rate is on average negatively correlated with the number of absent working days among private and public <span class="hlt">sector</span> workers as well as among self-employed men. The correlations between regional unemployment rate and doctor visits are only significantly negative among private <span class="hlt">sector</span> workers. Copyright © 2012 John Wiley & Sons, Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.epa.gov/regulatory-information-sector/agriculture-sectors','PESTICIDES'); return false;" href="https://www.epa.gov/regulatory-information-sector/agriculture-sectors"><span>Agriculture <span class="hlt">Sectors</span></span></a></p> <p><a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a></p> <p></p> <p></p> <p>The Agriculture <span class="hlt">sectors</span> comprise establishments primarily engaged in growing crops, raising animals, and harvesting fish and other animals. Find information on compliance, enforcement and guidance on EPA laws and regulations on the NAICS 111 & 112 <span class="hlt">sectors</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050028442','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050028442"><span><span class="hlt">Boundary</span> Layer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Loitsianskii. L. G.</p> <p>1956-01-01</p> <p>The fundamental, practically the most important branch of the modern mechanics of a viscous fluid or a gas, is that branch which concerns itself with the study of the <span class="hlt">boundary</span> layer. The presence of a <span class="hlt">boundary</span> layer accounts for the origin of the resistance and lift force, the breakdown of the smooth flow about bodies, and other phenomena that are associated with the motion of a body in a real fluid. The concept of <span class="hlt">boundary</span> layer was clearly formulated by the founder of aerodynamics, N. E. Joukowsky, in his well-known work "On the Form of Ships" published as early as 1890. In his book "Theoretical Foundations of Air Navigation," Joukowsky gave an account of the most important properties of the <span class="hlt">boundary</span> layer and pointed out the part played by it in the production of the resistance of bodies to motion. The fundamental differential equations of the motion of a fluid in a laminar <span class="hlt">boundary</span> layer were given by Prandtl in 1904; the first solutions of these equations date from 1907 to 1910. As regards the turbulent <span class="hlt">boundary</span> layer, there does not exist even to this day any rigorous formulation of this problem because there is no closed system of equations for the turbulent motion of a fluid. Soviet scientists have done much toward developing a general theory of the <span class="hlt">boundary</span> layer, and in that branch of the theory which is of greatest practical importance at the present time, namely the study of the <span class="hlt">boundary</span> layer at large velocities of the body in a compressed gas, the efforts of the scientists of our country have borne fruit in the creation of a new theory which leaves far behind all that has been done previously in this direction. We shall herein enumerate the most important results by Soviet scientists in the development of the theory of the <span class="hlt">boundary</span> layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JNuM..266..485D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JNuM..266..485D"><span>The diagnosed mobile limiters of the TJ-II stellarator for plasma <span class="hlt">boundary</span> studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de la Cal, E.; Tabarés, F. L.; Tafalla, D.; Cortés, I. García.; Hidalgo, C.; López-Fraguas, A.</p> <p></p> <p>TJ-II is a medium size (major radius R=1.5 m, average plasma radius a <0.25 m, on axis <span class="hlt">magnetic</span> field B=1 T) helical axis stellarator. The main characteristic is its <span class="hlt">magnetic</span> configuration flexibility, due to the separate control of the different <span class="hlt">magnetic</span> field coils. The two diagnosed mobile limiters are installed to reduce thermal loads on the thin protection plates of the contacting plasma-chamber regions and to study the plasma edge. First diagnostics are a set of thermocouples, Langmuir probes, H α-detectors and a CCD video camera with different filters (atomic lines of HeI, H α and near IR) looking at the limiter. A method of passive spectroscopy is proposed to map the electron temperature and density over the whole limiter surface by analysing the emission of helium recycling neutrals. It is expected from previous results of other stellarators, that the <span class="hlt">boundary</span> <span class="hlt">magnetic</span> topology will have a strong influence on the plasma-wall interaction. The mobile limiters can control the last closed <span class="hlt">magnetic</span> surface and diagnose the plasma <span class="hlt">boundary</span>. A qualitative different plasma edge scenario is foreseen between the limiter and the natural island divertor configuration (rational rotational transform inside the limiter radius). Plasma-wall interaction in TJ-II shows very specific features and the optimisation of the plasma edge topology can influence strongly the core plasma parameters. In particular, impurity screening will be a challenge due to the large power density which will be available in future (up to 2 MW NBI for 0.5 s). A safe operation for future high β-plasmas is also required and the mobile limiters should help to remove a fraction of the conductive/convective power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015CMaPh.339.1101N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015CMaPh.339.1101N"><span>On the Aharonov-Bohm Operators with Varying Poles: The <span class="hlt">Boundary</span> Behavior of Eigenvalues</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Noris, Benedetta; Nys, Manon; Terracini, Susanna</p> <p>2015-11-01</p> <p>We consider a <span class="hlt">magnetic</span> Schrödinger operator with <span class="hlt">magnetic</span> field concentrated at one point (the pole) of a domain and half integer circulation, and we focus on the behavior of Dirichlet eigenvalues as functions of the pole. Although the <span class="hlt">magnetic</span> field vanishes almost everywhere, it is well known that it affects the operator at the spectral level (the Aharonov-Bohm effect, Phys Rev (2) 115:485-491, 1959). Moreover, the numerical computations performed in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010) show a rather complex behavior of the eigenvalues as the pole varies in a planar domain. In this paper, in continuation of the analysis started in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010), we analyze the relation between the variation of the eigenvalue and the nodal structure of the associated eigenfunctions. We deal with planar domains with Dirichlet <span class="hlt">boundary</span> conditions and we focus on the case when the singular pole approaches the <span class="hlt">boundary</span> of the domain: then, the operator loses its singular character and the k-th <span class="hlt">magnetic</span> eigenvalue converges to that of the standard Laplacian. We can predict both the rate of convergence and whether the convergence happens from above or from below, in relation with the number of nodal lines of the k-th eigenfunction of the Laplacian. The proof relies on the variational characterization of eigenvalues, together with a detailed asymptotic analysis of the eigenfunctions, based on an Almgren-type frequency formula for <span class="hlt">magnetic</span> eigenfunctions and on the blow-up technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730002039','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730002039"><span>Large-scale properties of the interplanetary <span class="hlt">magnetic</span> field</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schatten, K. H.</p> <p>1972-01-01</p> <p>Early theoretical work of Parker is presented along with the observational evidence supporting his Archimedes spiral model. Variations present in the interplanetary <span class="hlt">magnetic</span> field from the spiral angle are related to structures in the solar wind. The causes of these structures are found to be either nonuniform radial solar wind flow or the time evolution of the photospheric field. Coronal <span class="hlt">magnetic</span> models are related to the connection between the solar <span class="hlt">magnetic</span> field and the interplanetary <span class="hlt">magnetic</span> field. Direct extension of the solar field-<span class="hlt">magnetic</span> nozzle controversy is discussed along with the coronal <span class="hlt">magnetic</span> models. Effects of active regions on the interplanetary <span class="hlt">magnetic</span> field is discussed with particular reference to the evolution of interplanetary <span class="hlt">sectors</span>. Interplanetary <span class="hlt">magnetic</span> field magnitude variations are shown throughout the solar cycle. The percentage of time the field magnitude is greater than 10 gamma is shown to closely parallel sunspot number. The sun's polar field influence on the interplanetary field and alternative views of the <span class="hlt">magnetic</span> field structure out of the ecliptic plane are presented. In addition, a variety of significantly different interplanetary field structures are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890056881&hterms=earth+magnetic+field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dearth%2Bmagnetic%2Bfield','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890056881&hterms=earth+magnetic+field&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dearth%2Bmagnetic%2Bfield"><span>Satellite measurements of the earth's crustal <span class="hlt">magnetic</span> field</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schnetzler, C. C.</p> <p>1989-01-01</p> <p>The literature associated with the Magsat mission has evaluated the capabilities and limitations of satellite measurements of the earth's crustal <span class="hlt">magnetic</span> field, and demonstrated that there exists a 300-3000 km <span class="hlt">magnetic</span> field, related to major features in the earth's crust, which is primarily caused by induction. Due to its scale and sensitivity, satellite data have been useful in the development of models for such large crustal features as subduction zones, submarine platforms, continental accretion <span class="hlt">boundaries</span>, and rifts. Attention is presently given to the lack of agreement between laboratory and satellite estimates of lower crustal <span class="hlt">magnetization</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JGRA..10912213S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JGRA..10912213S"><span>Two types of energy-dispersed ion structures at the plasma sheet <span class="hlt">boundary</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sauvaud, J.-A.; Kovrazhkin, R. A.</p> <p>2004-12-01</p> <p>We study two main types of ion energy dispersions observed in the energy range ˜1 to 14 keV on board the Interball-Auroral (IA) satellite at altitudes 2-3 RE at the poleward <span class="hlt">boundary</span> of the plasma sheet. The first type of structure is named velocity dispersed ion structures (VDIS). It is known that VDIS represent a global proton structure with a latitudinal width of ˜0.7-2.5°, where the ion overall energy increases with latitude. IA data allow to show that VDIS are made of substructures lasting for ˜1-3 min. Inside each substructure, high-energy protons arrive first, regardless of the direction of the plasma sheet <span class="hlt">boundary</span> crossing. A near-continuous rise of the maximal and minimal energies of consecutive substructures with invariant latitude characterizes VDIS. The second type of dispersed structure is named time-of-flight dispersed ion structures (TDIS). TDIS are recurrent sporadic structures in H+ (and also O+) with a quasi-period of ˜3 min and a duration of ˜1-3 min. The maximal energy of TDIS is rather constant and reaches ≥14 keV. During both poleward and equatorward crossings of the plasma sheet <span class="hlt">boundary</span>, inside each TDIS, high-energy ions arrive first. These structures are accompanied by large fluxes of upflowing H+ and O+ ions with maximal energies up to 5-10 keV. In association with TDIS, bouncing H+ clusters are observed in quasi-dipolar <span class="hlt">magnetic</span> field tubes, i.e., equatorward from TDIS. The electron populations generally have different properties during observations of VDIS and TDIS. The electron flux accompanying VDIS first increases smoothly and then decreases after Interball-Auroral has passed through the proton structure. The average electron energy in the range ˜0.5-2 keV is typical for electrons from the plasma sheet <span class="hlt">boundary</span> layer (PSBL). The electron fluxes associated with TDIS increases suddenly at the polar <span class="hlt">boundary</span> of the auroral zone. Their average energy, reaching ˜5-8 keV, is typical for CPS. A statistical analysis shows that</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001MNRAS.328.1161M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001MNRAS.328.1161M"><span>Torsional oscillations of <span class="hlt">magnetized</span> relativistic stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Messios, Neophytos; Papadopoulos, Demetrios B.; Stergioulas, Nikolaos</p> <p>2001-12-01</p> <p>Strong <span class="hlt">magnetic</span> fields in relativistic stars can be a cause of crust fracturing, resulting in the excitation of global torsional oscillations. Such oscillations could become observable in gravitational waves or in high-energy radiation, thus becoming a tool for probing the equation of state of relativistic stars. As the eigenfrequency of torsional oscillation modes is affected by the presence of a strong <span class="hlt">magnetic</span> field, we study torsional modes in <span class="hlt">magnetized</span> relativistic stars. We derive the linearized perturbation equations that govern torsional oscillations coupled to the oscillations of a <span class="hlt">magnetic</span> field, when variations in the metric are neglected (Cowling approximation). The oscillations are described by a single two-dimensional wave equation, which can be solved as a <span class="hlt">boundary</span>-value problem to obtain eigenfrequencies. We find that, in the non-<span class="hlt">magnetized</span> case, typical oscillation periods of the fundamental l=2 torsional modes can be nearly a factor of 2 larger for relativistic stars than previously computed in the Newtonian limit. For <span class="hlt">magnetized</span> stars, we show that the influence of the <span class="hlt">magnetic</span> field is highly dependent on the assumed <span class="hlt">magnetic</span> field configuration, and simple estimates obtained previously in the literature cannot be used for identifying normal modes observationally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990009051','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990009051"><span><span class="hlt">Magnetic</span> Fluid Friction and Wear Behavior</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Keith, Theo G., Jr.</p> <p>1998-01-01</p> <p>The friction and wear properties of two groups of <span class="hlt">magnetic</span> fluids, one developed at NASA Lewis Research Center and a commercial fluid, were evaluated for <span class="hlt">boundary</span> lubrication. Friction and wear measurements were made using a pin-on-disk apparatus. Three different ball materials were evaluated, (1) 440C, (2) Al2O3, and (3) Si3N4 against 440C disks. The first class of <span class="hlt">magnetic</span> fluids have a low vapor pressure hydrocarbon base oil and are suitable for space application. Four variations of this fluid were evaluated: (1) the base oil, (2) base oil with anti-wear additives, (3) a 100 Gauss strength <span class="hlt">magnetic</span> fluid, and (4) a 400 gauss <span class="hlt">magnetic</span> fluid. The commercial fluid base oil and four different <span class="hlt">magnetic</span> particle concentration levels have been evaluated. A space qualified fluorinated lubricant was tested for base line comparison. Hardness, optical microscopy, surface profilometry, and surface analysis were used to characterize the test specimens. Friction was unaffected by the concentration of <span class="hlt">magnetic</span> particles. Wear rates for <span class="hlt">magnetic</span> fluids were slightly higher than the base oil. The low vapor pressure <span class="hlt">magnetic</span> fluid has better wear characteristics than the space qualified fluorinated lubricant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DPPN12032G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DPPN12032G"><span>Teaching an Old Dog an Old Trick: FREE-FIX and Free-<span class="hlt">Boundary</span> Axisymmetric MHD Equilibrium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guazzotto, Luca</p> <p>2015-11-01</p> <p>A common task in plasma physics research is the calculation of an axisymmetric equilibrium for tokamak modeling. The main unknown of the problem is the <span class="hlt">magnetic</span> poloidal flux ψ. The easiest approach is to assign the shape of the plasma and only solve the equilibrium problem in the plasma / closed-field-lines region (the ``fixed-<span class="hlt">boundary</span> approach''). Often, one may also need the vacuum fields, i.e. the equilibrium in the open-field-lines region, requiring either coil currents or ψ on some closed curve outside the plasma to be assigned (the ``free-<span class="hlt">boundary</span> approach''). Going from one approach to the other is a textbook problem, involving the calculation of Green's functions and surface integrals in the plasma. However, no tools are readily available to perform this task. Here we present a code (FREE-FIX) to compute a <span class="hlt">boundary</span> condition for a free-<span class="hlt">boundary</span> equilibrium given only the corresponding fixed-<span class="hlt">boundary</span> equilibrium. An improvement to the standard solution method, allowing for much faster calculations, is presented. Applications are discussed. PPPL fund 245139 and DOE grant G00009102.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005MolPh.103.2969F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005MolPh.103.2969F"><span><span class="hlt">Boundary</span> conditions, dimensionality, topology and size dependence of the superconducting transition temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fink, Herman J.; Haley, Stephen B.; Giuraniuc, Claudiu V.; Kozhevnikov, Vladimir F.; Indekeu, Joseph O.</p> <p>2005-11-01</p> <p>For various sample geometries (slabs, cylinders, spheres, hypercubes), de Gennes' <span class="hlt">boundary</span> condition parameter b is used to study its effect upon the transition temperature Tc of a superconductor. For b > 0 the order parameter at the surface is decreased, and as a consequence Tc is reduced, while for b < 0 the order parameter at the surface is increased, thereby enhancing Tc of a specimen in zero <span class="hlt">magnetic</span> field. Exact solutions, derived by Fink and Haley (Int. J. mod. Phys. B, 17, 2171 (2003)), of the order parameter of a slab of finite thickness as a function of temperature are presented, both for reduced and enhanced transition (nucleation) temperatures. At the nucleation temperature the order parameter approaches zero. This concise review closes with a link established between de Gennes' microscopic <span class="hlt">boundary</span> condition and the Ginzburg-Landau phenomenological approach, and a discussion of some relevant experiments. For example, applying the <span class="hlt">boundary</span> condition with b < 0 to tin whiskers elucidates the increase of Tc with strain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22661156-casting-coronal-magnetic-field-reconstruction-tools-using-mhd-bifrost-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22661156-casting-coronal-magnetic-field-reconstruction-tools-using-mhd-bifrost-model"><span>Casting the Coronal <span class="hlt">Magnetic</span> Field Reconstruction Tools in 3D Using the MHD Bifrost Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fleishman, Gregory D.; Loukitcheva, Maria; Anfinogentov, Sergey</p> <p></p> <p>Quantifying the coronal <span class="hlt">magnetic</span> field remains a central problem in solar physics. Nowadays, the coronal <span class="hlt">magnetic</span> field is often modeled using nonlinear force-free field (NLFFF) reconstructions, whose accuracy has not yet been comprehensively assessed. Here we perform a detailed casting of the NLFFF reconstruction tools, such as π -disambiguation, photospheric field preprocessing, and volume reconstruction methods, using a 3D snapshot of the publicly available full-fledged radiative MHD model. Specifically, from the MHD model, we know the <span class="hlt">magnetic</span> field vector in the entire 3D domain, which enables us to perform a “voxel-by-voxel” comparison of the restored and the true <span class="hlt">magnetic</span> fieldsmore » in the 3D model volume. Our tests show that the available π -disambiguation methods often fail in the quiet-Sun areas dominated by small-scale <span class="hlt">magnetic</span> elements, while they work well in the active region (AR) photosphere and (even better) chromosphere. The preprocessing of the photospheric <span class="hlt">magnetic</span> field, although it does produce a more force-free <span class="hlt">boundary</span> condition, also results in some effective “elevation” of the <span class="hlt">magnetic</span> field components. This “elevation” height is different for the longitudinal and transverse components, which results in a systematic error in absolute heights in the reconstructed <span class="hlt">magnetic</span> data cube. The extrapolations performed starting from the actual AR photospheric magnetogram are free from this systematic error, while other metrics are comparable with those for extrapolations from the preprocessed magnetograms. This finding favors the use of extrapolations from the original photospheric magnetogram without preprocessing. Our tests further suggest that extrapolations from a force-free chromospheric <span class="hlt">boundary</span> produce measurably better results than those from a photospheric <span class="hlt">boundary</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008544','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008544"><span><span class="hlt">Magnetic</span> Topology of Coronal Hole Linkages</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Titov, V. S.; Mikic, Z.; Linker, J. A.; Lionello, R.; Antiochos, S. K.</p> <p>2010-01-01</p> <p>In recent work, Antiochos and coworkers argued that the <span class="hlt">boundary</span> between the open and closed field regions on the Sun can be extremely complex with narrow corridors of open ux connecting seemingly disconnected coronal holes from the main polar holes, and that these corridors may be the sources of the slow solar wind. We examine, in detail, the topology of such <span class="hlt">magnetic</span> configurations using an analytical source surface model that allows for analysis of the eld with arbitrary resolution. Our analysis reveals three important new results: First, a coronal hole <span class="hlt">boundary</span> can join stably to the separatrix <span class="hlt">boundary</span> of a parasitic polarity region. Second, a single parasitic polarity region can produce multiple null points in the corona and, more important, separator lines connecting these points. Such topologies are extremely favorable for <span class="hlt">magnetic</span> reconnection, because it can now occur over the entire length of the separators rather than being con ned to a small region around the nulls. Finally, the coronal holes are not connected by an open- eld corridor of finite width, but instead are linked by a singular line that coincides with the separatrix footprint of the parasitic polarity. We investigate how the topological features described above evolve in response to motion of the parasitic polarity region. The implications of our results for the sources of the slow solar wind and for coronal and heliospheric observations are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22663650-magnetic-helicity-estimations-models-observations-solar-magnetic-field-iii-twist-number-method','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22663650-magnetic-helicity-estimations-models-observations-solar-magnetic-field-iii-twist-number-method"><span><span class="hlt">Magnetic</span> Helicity Estimations in Models and Observations of the Solar <span class="hlt">Magnetic</span> Field. III. Twist Number Method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Guo, Y.; Pariat, E.; Moraitis, K.</p> <p></p> <p>We study the writhe, twist, and <span class="hlt">magnetic</span> helicity of different <span class="hlt">magnetic</span> flux ropes, based on models of the solar coronal <span class="hlt">magnetic</span> field structure. These include an analytical force-free Titov–Démoulin equilibrium solution, non-force-free magnetohydrodynamic simulations, and nonlinear force-free <span class="hlt">magnetic</span> field models. The geometrical <span class="hlt">boundary</span> of the <span class="hlt">magnetic</span> flux rope is determined by the quasi-separatrix layer and the bottom surface, and the axis curve of the flux rope is determined by its overall orientation. The twist is computed by the Berger–Prior formula, which is suitable for arbitrary geometry and both force-free and non-force-free models. The <span class="hlt">magnetic</span> helicity is estimated by the twistmore » multiplied by the square of the axial <span class="hlt">magnetic</span> flux. We compare the obtained values with those derived by a finite volume helicity estimation method. We find that the <span class="hlt">magnetic</span> helicity obtained with the twist method agrees with the helicity carried by the purely current-carrying part of the field within uncertainties for most test cases. It is also found that the current-carrying part of the model field is relatively significant at the very location of the <span class="hlt">magnetic</span> flux rope. This qualitatively explains the agreement between the <span class="hlt">magnetic</span> helicity computed by the twist method and the helicity contributed purely by the current-carrying <span class="hlt">magnetic</span> field.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150022458','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150022458"><span>Determination Gradients of the Earth's <span class="hlt">Magnetic</span> Field from the Measurements of the Satellites and Inversion of the Kursk <span class="hlt">Magnetic</span> Anomaly</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Karoly, Kis; Taylor, Patrick T.; Geza, Wittmann</p> <p>2014-01-01</p> <p>We computed <span class="hlt">magnetic</span> field gradients at satellite altitude, over Europe with emphasis on the Kursk <span class="hlt">Magnetic</span> Anomaly (KMA). They were calculated using the CHAMP satellite total <span class="hlt">magnetic</span> anomalies. Our computations were done to determine how the <span class="hlt">magnetic</span> anomaly data from the new ESA/Swarm satellites could be utilized to determine the structure of the <span class="hlt">magnetization</span> of the Earths crust, especially in the region of the KMA. Since the ten years of 2 CHAMP data could be used to simulate the Swarm data. An initial East <span class="hlt">magnetic</span> anomaly gradient map of Europe was computed and subsequently the North, East and Vertical <span class="hlt">magnetic</span> gradients for the KMA region were calculated. The vertical gradient of the KMA was determined using Hilbert transforms. Inversion of the total KMA was derived using Simplex and Simulated Annealing algorithms. Our resulting inversion depth model is a horizontal quadrangle with upper 300-329 km and lower 331-339 km <span class="hlt">boundaries</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1250..496T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1250..496T"><span><span class="hlt">Magnetic</span> Force Microscopy Investigation of <span class="hlt">Magnetic</span> Domains in Nd2Fe14B</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Talari, Mahesh Kumar; Markandeyulu, G.; Rao, K. Prasad</p> <p>2010-07-01</p> <p>Remenance and coercivity in Nd2Fe14B materials are strongly dependent on the microstructural aspects like phases morphology and grain size. The coercivity (Hc) of a <span class="hlt">magnetic</span> material varies inversely with the grain size (D) and there is a critical size below which Hc∝D6. Domain wall pinning by grain <span class="hlt">boundaries</span> and foreign phases is the important mechanism in explaining the improvement in coercivity and remenance. Nd2Fe14B intermetallic compound with stochiometric composition was prepared from pure elements (Nd -99.5%, Fe—99.95%, B -99.99%) by arc melting in argon atmosphere. <span class="hlt">Magnetic</span> Force Microscope (MFM) gives high-resolution <span class="hlt">magnetic</span> domain structural information of ferromagnetic samples. DI-3100 Scanning Probe Microscope with MESP probes was used For MFM characterization of the samples. <span class="hlt">Magnetic</span> domains observed in cast ingots were very long (up to 40 μm were observed) and approximately 1-5 μm wide due to high anisotropy of the compounds. <span class="hlt">Magnetic</span> domains have displayed different image contrast and morphologies at different locations of the samples. The domain morphologies and image contrast obtained in this analysis were explained in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JGR...10527531F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JGR...10527531F"><span>Pulsating midmorning auroral arcs, filamentation of a mixing region in a flank <span class="hlt">boundary</span> layer, and ULF waves observed during a Polar-Svalbard conjunction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Farrugia, C. J.; Sandholt, P. E.; Maynard, N. C.; Burke, W. J.; Scudder, J. D.; Ober, D. M.; Moen, J.; Russell, C. T.</p> <p>2000-12-01</p> <p><span class="hlt">Magnetically</span> conjugate observations by the HYDRA and the <span class="hlt">Magnetic</span> Field Experiment instruments on Polar, meridian-scanning photometers and all-sky imagers at Ny-Ålesund, and International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometers on November 30, 1997, illustrate aspects of magnetosphere-ionosphere coupling at 0900-1000 <span class="hlt">magnetic</span> local times (MLT) and 70°-80° <span class="hlt">magnetic</span> latitudes and their dependence on interplanetary parameters. Initially, Polar crossed a <span class="hlt">boundary</span> layer on closed field lines where magnetospheric and magnetosheath plasmas are mixed. This region contains filaments where magnetospheric electron and ion fluxes are enhanced. These filaments are associated with field-aligned current structures embedded within the large-scale region 1 (R1) current. Ground auroral imagery document the presence at this time of discrete, east-west aligned arcs, which are in one-to-one correspondence with the filaments. Temporal variations present in these auroral arcs correlate with Pc 5 pulsations and are probably related to modulations in the interplanetary electric field. The auroral observations indicate that the filamented mixing region persisted for many tens of minutes, suggesting a spatial structuring. The data suggest further that the filamented, mixing region is an important source of the R1 current and the associated midmorning arcs. When the interplanetary <span class="hlt">magnetic</span> field (IMF) turned strongly north, Polar had entered the dayside extension of the central plasma sheet/region 2 current system where it and the underlying ground magnetometers recorded a clear field line resonance of frequency ~2.4 mHz (Pc 5 range). The source of these oscillations is most likely the Kelvin-Helmholtz instability. Subsequent to the IMF northward turning, the multiple arcs were replaced by a single auroral form to the north of Ny-Ålesund (at 1000 MLT) in the vicinity of the westward edge of the cusp. ULF pulsation activity changed to the Pc 3-4 range in the regime of</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28974671','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28974671"><span>Neutrophil-inspired propulsion in a combined acoustic and <span class="hlt">magnetic</span> field.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ahmed, Daniel; Baasch, Thierry; Blondel, Nicolas; Läubli, Nino; Dual, Jürg; Nelson, Bradley J</p> <p>2017-10-03</p> <p>Systems capable of precise motion in the vasculature can offer exciting possibilities for applications in targeted therapeutics and non-invasive surgery. So far, the majority of the work analysed propulsion in a two-dimensional setting with limited controllability near <span class="hlt">boundaries</span>. Here we show bio-inspired rolling motion by introducing superparamagnetic particles in <span class="hlt">magnetic</span> and acoustic fields, inspired by a neutrophil rolling on a wall. The particles self-assemble due to dipole-dipole interaction in the presence of a rotating <span class="hlt">magnetic</span> field. The aggregate migrates towards the wall of the channel due to the radiation force of an acoustic field. By combining both fields, we achieved a rolling-type motion along the <span class="hlt">boundaries</span>. The use of both acoustic and <span class="hlt">magnetic</span> fields has matured in clinical settings. The combination of both fields is capable of overcoming the limitations encountered by single actuation techniques. We believe our method will have far-reaching implications in targeted therapeutics.Devising effective swimming and propulsion strategies in microenvironments is attractive for drug delivery applications. Here Ahmed et al. demonstrate a micropropulsion strategy in which a combination of <span class="hlt">magnetic</span> and acoustic fields is used to assemble and propel colloidal particles along channel walls.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017CoGG...47..261S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017CoGG...47..261S"><span><span class="hlt">Magnetic</span> and velocity fields in a dynamo operating at extremely small Ekman and <span class="hlt">magnetic</span> Prandtl numbers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Šimkanin, Ján; Kyselica, Juraj</p> <p>2017-12-01</p> <p>Numerical simulations of the geodynamo are becoming more realistic because of advances in computer technology. Here, the geodynamo model is investigated numerically at the extremely low Ekman and <span class="hlt">magnetic</span> Prandtl numbers using the PARODY dynamo code. These parameters are more realistic than those used in previous numerical studies of the geodynamo. Our model is based on the Boussinesq approximation and the temperature gradient between upper and lower <span class="hlt">boundaries</span> is a source of convection. This study attempts to answer the question how realistic the geodynamo models are. Numerical results show that our dynamo belongs to the strong-field dynamos. The generated <span class="hlt">magnetic</span> field is dipolar and large-scale while convection is small-scale and sheet-like flows (plumes) are preferred to a columnar convection. Scales of <span class="hlt">magnetic</span> and velocity fields are separated, which enables hydromagnetic dynamos to maintain the <span class="hlt">magnetic</span> field at the low <span class="hlt">magnetic</span> Prandtl numbers. The inner core rotation rate is lower than that in previous geodynamo models. On the other hand, dimensional magnitudes of velocity and <span class="hlt">magnetic</span> fields and those of the <span class="hlt">magnetic</span> and viscous dissipation are larger than those expected in the Earth's core due to our parameter range chosen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSH33B2472M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSH33B2472M"><span>Random Interchange of <span class="hlt">Magnetic</span> Connectivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matthaeus, W. H.; Ruffolo, D. J.; Servidio, S.; Wan, M.; Rappazzo, A. F.</p> <p>2015-12-01</p> <p><span class="hlt">Magnetic</span> connectivity, the connection between two points along a <span class="hlt">magnetic</span> field line, has a stochastic character associated with field lines random walking in space due to <span class="hlt">magnetic</span> fluctuations, but connectivity can also change in time due to dynamical activity [1]. For fluctuations transverse to a strong mean field, this connectivity change be caused by stochastic interchange due to component reconnection. The process may be understood approximately by formulating a diffusion-like Fokker-Planck coefficient [2] that is asymptotically related to standard field line random walk. Quantitative estimates are provided, for transverse <span class="hlt">magnetic</span> field models and anisotropic models such as reduced magnetohydrodynamics. In heliospheric applications, these estimates may be useful for understanding mixing between open and close field line regions near coronal hole <span class="hlt">boundaries</span>, and large latitude excursions of connectivity associated with turbulence. [1] A. F. Rappazzo, W. H. Matthaeus, D. Ruffolo, S. Servidio & M. Velli, ApJL, 758, L14 (2012) [2] D. Ruffolo & W. Matthaeus, ApJ, 806, 233 (2015)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910036461&hterms=Net+Neutrality&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DNet%2BNeutrality','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910036461&hterms=Net+Neutrality&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DNet%2BNeutrality"><span>Equilibrium structure of the plasma sheet <span class="hlt">boundary</span> layer-lobe interface</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Romero, H.; Ganguli, G.; Palmadesso, P.; Dusenbery, P. B.</p> <p>1990-01-01</p> <p>Observations are presented which show that plasma parameters vary on a scale length smaller than the ion gyroradius at the interface between the plasma sheet <span class="hlt">boundary</span> layer and the lobe. The Vlasov equation is used to investigate the properties of such a <span class="hlt">boundary</span> layer. The existence, at the interface, of a density gradient whose scale length is smaller than the ion gyroradius implies that an electrostatic potential is established in order to maintain quasi-neutrality. Strongly sheared (scale lengths smaller than the ion gyroradius) perpendicular and parallel (to the ambient <span class="hlt">magnetic</span> field) electron flows develop whose peak velocities are on the order of the electron thermal speed and which carry a net current. The free energy of the sheared flows can give rise to a broadband spectrum of electrostatic instabilities starting near the electron plasma frequency and extending below the lower hybrid frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21889279','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21889279"><span>Reversing the polarity of a cochlear implant <span class="hlt">magnet</span> after <span class="hlt">magnetic</span> resonance imaging.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jeon, Ju Hyun; Bae, Mi Ran; Chang, Jae Won; Choi, Jae Young</p> <p>2012-08-01</p> <p>The number of patients with cochlear implant (CI) has been rapidly increasing in recent years, and these patients show a growing need of examination by <span class="hlt">magnetic</span> resonance imaging (MRI). However, the use of MRI on patients with CI is restricted by the internal <span class="hlt">magnet</span> of the CI. Many studies have investigated the safety of performing 1.5T MRI on patients with CI, which is now being practiced in a clinical setting. We experienced a case in which the polarity of the cochlear implant <span class="hlt">magnet</span> was reversed after the patient was examined using 1.5T MRI. The external device was attached to the internal device oppositely. We could not find displacement of the internal device, <span class="hlt">magnet</span>, or electrode upon radiological evaluation. We came up with two possible mechanisms by which the polarity of the <span class="hlt">magnet</span> reversed. The first possibility was that the <span class="hlt">magnetic</span> field of MRI reversed the polarity of the <span class="hlt">magnet</span>. The second was that the internal <span class="hlt">magnet</span> was physically realigned while interacting with the MRI. We believe the second hypothesis to be more reliable. A removable <span class="hlt">magnet</span> and a loose <span class="hlt">magnet</span> <span class="hlt">boundary</span> of a CI device may have allowed for physical reorientation of the internal <span class="hlt">magnet</span>. Therefore, in order to avoid these complications, first, the internal <span class="hlt">magnet</span> must not be aligned anti-parallel with the <span class="hlt">magnetic</span> polarity of MRI. In the Siemens MRI, the vector of the <span class="hlt">magnetic</span> field is downward, so implant site should be placed in facing upwards to minimize demagnetization. In the GE Medical Systems MRI, the vector of the <span class="hlt">magnetic</span> field is upward, so the implant site should be placed facing downwards. Second, wearing of a commercial mold which is fixed to the internal device before performing MRI can be helpful. In addition, any removable internal <span class="hlt">magnets</span> in a CI device should be removed before MRI, especially in the trunk. However, to ultimately solve this problem, the pocket of the internal <span class="hlt">magnet</span> should be redesigned for safety. Copyright © 2011. Published by Elsevier Ireland Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DPPJ10014S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DPPJ10014S"><span>Measurement of argon neutral velocity distribution functions near an absorbing <span class="hlt">boundary</span> in a plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Short, Zachary; Thompson, Derek; Good, Timothy; Scime, Earl</p> <p>2016-10-01</p> <p>Neutral particle distributions are critical to the study of plasma <span class="hlt">boundary</span> interactions, where ion-neutral collisions, e.g. via charge exchange, may modify energetic particle populations impacting the <span class="hlt">boundary</span> surface. Neutral particle behavior at absorbing <span class="hlt">boundaries</span> thus underlies a number of important plasma physics issues, such as wall loading in fusion devices and anomalous erosion in Hall thruster channels. Neutral velocity distribution functions (NVDFs) are measured using laser-induced fluorescence (LIF). Our LIF scheme excites the 1s4 non-metastable state of neutral argon with 667.913 nm photons. The subsequent decay emission at 750.590 nm is recorded synchronously with injection laser frequency. Measurements are performed near a grounded <span class="hlt">boundary</span> immersed in a cylindrical helicon plasma, with the <span class="hlt">boundary</span> plate oriented at an oblique angle to the <span class="hlt">magnetic</span> field. NVDFs are recorded in multiple velocity dimensions and in a three-dimensional volume, enabling point-to-point comparisons with NVDF predictions from particle-in-cell models as well as comparisons with ion velocity distribution function measurements obtained in the same regions through Ar-II LIF. This work is supported by US National Science Foundation Grant Number PHYS-1360278.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080004508','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080004508"><span>Low loss pole configuration for multi-pole homopolar <span class="hlt">magnetic</span> bearings</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blumenstock, Kenneth A. (Inventor); Hakun, Claef F. (Inventor)</p> <p>2001-01-01</p> <p>A new pole configuration for multi-pole homopolar bearings proposed in this invention reduces rotational losses caused by eddy-currents generated when non-uniform flux distributions exist along the rotor surfaces. The new homopolar <span class="hlt">magnetic</span> bearing includes a stator with reduced pole-to-pole and exhibits a much more uniform rotor flux than with large pole-to-pole gaps. A pole feature called a pole-link is incorporated into the low-loss poles to provide a uniform pole-to-pole gap and a controlled path for pole-to-pole flux. In order to implement the low-loss pole configuration of <span class="hlt">magnetic</span> bearings with small pole-to-pole gaps, a new stator configuration was developed to facilitate installation of coil windings. The stator was divided into <span class="hlt">sector</span> shaped pieces, as many pieces as there are poles. Each <span class="hlt">sector</span>-shaped pole-piece can be wound on a standard coil winding machine, and it is practical to wind precision layer wound coils. To achieve maximum actuation efficiency, it is desirable to use all the available space for the coil formed by the natural geometric configuration. Then, the coils can be wound in a tapered shape. After winding, the <span class="hlt">sectored</span>-pole-pieces are installed into and fastened by bonding or other means, to a ring of material which encloses the <span class="hlt">sectored</span>-pole-pieces, forming a complete stator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24766617','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24766617"><span>Shifting contours of <span class="hlt">boundaries</span>: an exploration of inter-agency integration between hospital and community interprofessional diabetes programs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wong, Rene; Breiner, Petra; Mylopoulos, Maria</p> <p>2014-09-01</p> <p>This article reports on research into the relationships that emerged between hospital-based and community-based interprofessional diabetes programs involved in inter-agency care. Using constructivist grounded theory methodology we interviewed a purposive theoretical sample of 21 clinicians and administrators from both types of programs. Emergent themes were identified through a process of constant comparative analysis. Initial <span class="hlt">boundaries</span> were constructed based on contrasts in beliefs, practices and expertise. In response to bureaucratic and social pressures, <span class="hlt">boundaries</span> were redefined in a way that created role uncertainty and disempowered community programs, ultimately preventing collaboration. We illustrate the dynamic and multi-dimensional nature of social and symbolic <span class="hlt">boundaries</span> in inter-agency diabetes care and the tacit ways in which hospitals can maintain a power position at the expense of other actors in the field. As efforts continue in Canada and elsewhere to move knowledge and resources into community <span class="hlt">sectors</span>, we highlight the importance of hospitals seeing beyond their own interests and adopting more altruistic models of inter-agency integration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ZaMP...69...32P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ZaMP...69...32P"><span>A free <span class="hlt">boundary</span> approach to the Rosensweig instability of ferrofluids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parini, Enea; Stylianou, Athanasios</p> <p>2018-04-01</p> <p>We establish the existence of saddle points for a free <span class="hlt">boundary</span> problem describing the two-dimensional free surface of a ferrofluid undergoing normal field instability. The starting point is the ferrohydrostatic equations for the <span class="hlt">magnetic</span> potentials in the ferrofluid and air, and the function describing their interface. These constitute the strong form for the Euler-Lagrange equations of a convex-concave functional, which we extend to include interfaces that are not necessarily graphs of functions. Saddle points are then found by iterating the direct method of the calculus of variations and applying classical results of convex analysis. For the existence part, we assume a general nonlinear <span class="hlt">magnetization</span> law; for a linear law, we also show, via convex duality, that the saddle point is a constrained minimizer of the relevant energy functional.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21561198','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21561198"><span>Exact time-dependent nonlinear dispersive wave solutions in compressible <span class="hlt">magnetized</span> plasmas exhibiting collapse.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chakrabarti, Nikhil; Maity, Chandan; Schamel, Hans</p> <p>2011-04-08</p> <p>Compressional waves in a <span class="hlt">magnetized</span> plasma of arbitrary resistivity are treated with the lagrangian fluid approach. An exact nonlinear solution with a nontrivial space and time dependence is obtained with <span class="hlt">boundary</span> conditions as in Harris' current sheet. The solution shows competition among hydrodynamic convection, <span class="hlt">magnetic</span> field diffusion, and dispersion. This results in a collapse of density and the <span class="hlt">magnetic</span> field in the absence of dispersion. The dispersion effects arrest the collapse of density but not of the <span class="hlt">magnetic</span> field. A possible application is in the early stage of <span class="hlt">magnetic</span> star formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/7254841','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/7254841"><span><span class="hlt">Magnetic</span> fields for transporting charged beams</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Parzen, G.</p> <p>1976-01-01</p> <p>The transport of charged particle beams requires <span class="hlt">magnetic</span> fields that must be shaped correctly and very accurately. During the last 20 years or so, many studies have been made, both analytically and through the use of computer programs, of various <span class="hlt">magnetic</span> shapes that have proved to be useful. Many of the results for <span class="hlt">magnetic</span> field shapes can be applied equally well to electric field shapes. A report is given which gathers together the results that have more general significance and would be useful in designing a configuration to produce a desired <span class="hlt">magnetic</span> field shape. The field shapes studied include themore » fields in dipoles, quadrupoles, sextupoles, octupoles, septum <span class="hlt">magnets</span>, combined-function <span class="hlt">magnets</span>, and electrostatic septums. Where possible, empirical formulas are proposed, based on computer and analytical studies and on <span class="hlt">magnetic</span> field measurements. These empirical formulas are often easier to use than analytical formulas and often include effects that are difficult to compute analytically. In addition, results given in the form of tables and graphs serve as illustrative examples. The field shapes studied include uniform fields produced by window-frame <span class="hlt">magnets</span>, C-<span class="hlt">magnets</span>, H-<span class="hlt">magnets</span>, and cosine <span class="hlt">magnets</span>; linear fields produced by various types of quadrupoles; quadratic and cubic fields produced by sextupoles and octupoles; combinations of uniform and linear fields; and septum fields with sharp <span class="hlt">boundaries</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JAP....80.4548G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JAP....80.4548G"><span>High-frequency, transient <span class="hlt">magnetic</span> susceptibility of ferroelectrics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grimes, Craig A.</p> <p>1996-10-01</p> <p>A significant high-frequency <span class="hlt">magnetic</span> susceptibility was measured both in weakly polarized and nonpolarized samples of barium titanate, lead zirconate titanate, and carnauba wax. <span class="hlt">Magnetic</span> susceptibility measurements were made from 10 to 500 MHz using a thin film permeameter at room temperature; initial susceptibilities ranged from 0.1 to 2.5. These values are larger than expected for paramagnets and smaller than expected for ferromagnets. It was found that the <span class="hlt">magnetic</span> susceptibility decreases rapidly with exposure to the exciting field. The origin of the <span class="hlt">magnetic</span> susceptibility is thought to originate with the applied time varying electric field associated with the susceptibility measurements. An electric field acts to rotate an electric dipole, creating a <span class="hlt">magnetic</span> quadrupole if the two moments are balanced, and a net <span class="hlt">magnetic</span> dipole moment if imbalanced. It is thought that local electrostatic fields created at ferroelectric domain discontinuities associated with grain <span class="hlt">boundaries</span> create an imbalance in the anion rotation that results in a net, measurable, <span class="hlt">magnetic</span> moment. The origin of the <span class="hlt">magnetic</span> aftereffect may be due to the local heating of the material through the moving charges associated with the <span class="hlt">magnetic</span> moment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.5877B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.5877B"><span>Local time asymmetry of Saturn's magnetosheath flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burkholder, B.; Delamere, P. A.; Ma, X.; Thomsen, M. F.; Wilson, R. J.; Bagenal, F.</p> <p>2017-06-01</p> <p>Using gross averages of the azimuthal component of flow in Saturn's magnetosheath, we find that flows in the prenoon <span class="hlt">sector</span> reach a maximum value of roughly half that of the postnoon side. Corotational magnetodisc plasma creates a much larger flow shear with solar wind plasma prenoon than postnoon. Maxwell stress tensor analysis shows that momentum can be transferred out of the magnetosphere along tangential field lines if a normal component to the <span class="hlt">boundary</span> is present, i.e., field lines which pierce the magnetopause. A Kelvin-Helmholtz unstable flow gives rise to precisely this situation, as intermittent reconnection allows the <span class="hlt">magnetic</span> field to thread the <span class="hlt">boundary</span>. We interpret the Kelvin-Helmholtz instability acting along the magnetopause as a tangetial drag, facilitating two-way transport of momentum through the <span class="hlt">boundary</span>. We use reduced magnetosheath flows in the dawn <span class="hlt">sector</span> as evidence of the importance of this interaction in Saturn's magnetosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JMMM..314...30B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JMMM..314...30B"><span>Effect of grain <span class="hlt">boundary</span> layer strain on the <span class="hlt">magnetic</span> and transport properties of (100- x) La 0.7Ca 0.3MnO 3/( x) BaTiO 3 composites showing enhanced magnetoresistance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bose, Esa; Taran, S.; Karmakar, S.; Chaudhuri, B. K.; Pal, S.; Sun, C. P.; Yang, H. D.</p> <p>2007-07-01</p> <p>A ferromagnetic/ferroelectric composite system, viz. (100- x)La 0.7Ca 0.3 MnO 3 [LCMO]/( x) BaTiO 3 [BTO] (with x=0.0%, 1.0%, 5.0%, 7.5%, 10.0% and 15.0%, in wt%) has been synthesized and the temperature-dependent DC <span class="hlt">magnetization</span> M( T), resistivity ρ( T), magnetoresistance (MR), and thermoelectric power S( T) have been studied. Both metal-insulator transition temperature ( TMI) and the corresponding Curie temperature ( TC) decrease whereas peak resistivity at TMI increases as x is enhanced from 0.0% to 10.0%. For x>10.0%, this trend of variation is reversed. A maximum three-fold increase of magnetoresistance (MR) is observed (for sample with x=10.0%) due to the addition of ferroelectric (non-<span class="hlt">magnetic</span>) perovskite BTO (compared to the mother compound LCMO). Interestingly, thermoelectric power S( T) shows a pronounced depression (dip) near the <span class="hlt">magnetic</span> transition region for the composite samples. The above results have been analyzed considering strain induced by the LCMO/BTO grain <span class="hlt">boundary</span> layer (BL).</p