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Sample records for magnetospheric substorms occurring

  1. Magnetospheric substorms

    NASA Astrophysics Data System (ADS)

    Lopez, Ramon E.

    1990-12-01

    The earth's magnetic tail acts as a reservoir for the energy that is extracted by the interaction between the solar wind and the earth's magnetosphere. Occasionally, a portion of that energy is released through a violent process known as a magnetospheric substorm. The substorm is one of the most important magnetospheric phenomena, and it is the subject of extensive research. Recent work utilizing data collected by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer satellite, built at APL, has contributed markedly to the understanding of substorms.

  2. Observations of magnetospheric substorms occurring with no apparent solar wind/IMF trigger

    SciTech Connect

    Henderson, M.G.; Reeves, G.D.; Belian, R.D.; Murphree, J.S.

    1996-03-01

    An outstanding topic in magnetospheric physics is whether substorms are always externally triggered by disturbances in either the interplanetary magnetic field or solar wind, or whether they can also occur solely as the result of an internal magnetospheric instability. Over the past decade, arguments have been made on both sides of this issue. Horwitz and McPherron have shown examples of substorm onsets which they claimed were not externally triggered. However, as pointed out by Lyons, there are several problems associated with these studies that make their results somewhat inconclusive. In particular, in the McPherron et al. study, fluctuations in the B{sub y} component were not considered as possible triggers. Furthermore, Lyons suggests that the sharp decreases in the AL index during intervals of steady IMF/solar wind, are not substorms at all but rather that they are just enhancements of the convection driven DP2 current system that are often observed to occur during steady magnetospheric convection events. In the present study, we utilize a much more comprehensive dataset (consisting of particle data from the Los Alamos energetic particle detectors at geosynchronous orbit, IMP 8 magnetometer and plasma data, Viking UV auroral imager data, mid-latitude Pi2 pulsation data, ground magnetometer data and ISEE1 magnetic field and energetic particle data) to show as unambiguously as possible that typical substorms can indeed occur in the absence of an identifiable trigger in the solar wind/IMF.

  3. Onset of magnetospheric substorms.

    NASA Technical Reports Server (NTRS)

    Tsurutani, B.; Bogott, F.

    1972-01-01

    An examination of the onset of magnetospheric substorms is made by using ATS 5 energetic particles, conjugate balloon X rays and electric fields, all-sky camera photographs, and auroral-zone magnetograms. It is shown that plasma injection to ATS distances, conjugate 1- to 10-keV auroral particle precipitation, energetic electron precipitation, and enhancements of westward magnetospheric electric-field component all occur with the star of slowly developing negative magnetic bays. No trapped or precipitating energetic-particle features are seen at ATS 5 when later sharp negative magnetic-bay onsets occur at Churchill or Great Whale River.

  4. Magnetospheric Substorm Electrodynamics

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1998-01-01

    It was proposed that the expansion phase of substorms results from a reduction in the large-scale electric field imparted to the magnetosphere from the solar wind, following a greater than or equal to 30 min growth phase due to an enhancement in this electric field. The reduction in the electric field is assumed to propagate anti-sunward within the magnetosphere. Triggering by a reduction in the electric field is suggested by the observation that substorms are often triggered by northward turning of the interplanetary magnetic field (IMF). However, under the theory presented here, substorms may be triggered by anything that causes an electric field reduction such as a reduction in the magnitude of the y-component of the IMF. A reduction in the large-scale electric field disrupts both the inward motion and energization of plasma sheet particles that occurs during the growth phase. It is suggested here that this can lead to formation of the expansion-phase current wedge and active aurora. The current wedge results from the magnetic drift of ions, which has a speed proportional to particle energy, and a large azimuthal gradient in mean particle energy that is expected to develop in the vicinity of magnetic midnight during the growth phase. Current wedge formation will most likely be initiated near the radial distance (approx. 6- 10 R(sub E)) of the peak in the growth-phase plasma pressure distribution, and then propagate tailward from that region. Order-of-magnitude calculations show that the above proposal can account for the rapid development of the expansion phase relative to the growth phase, the magnitude of the reduction in the cross-tail current within the current wedge, the speeds of tailward and westward expansion of the current reduction region, the speeds of poleward and westward motion of active aurora in the ionosphere, and the magnitude of wedge field-aligned currents that connect the ionospheric region of active auroral to the divergent cross

  5. A mechanism for magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Erickson, G. M.; Heinemann, M.

    1994-01-01

    Energy-principle analysis performed on two-dimensional, self-consistent solutions for magnetospheric convection indicates that the magnetosphere is unstable to isobaric (yet still frozen-in) fluctuations of plasma-sheet flux tubes. Normally, pdV work associated with compression maintains stability of the inward/outward oscillating normal mode. However, if Earth's ionosphere can provide sufficient mass flux, isobaric expansion of flux tubes can occur. The growth of a field-aligned potential drop in the near-Earth, midnight portion of the plasma sheet, associated with upward field-aligned currents responsible for the Harang discontinuity, redistributes plasma along field lines in a manner that destabilizes the normal mode. The growth of this unstable mode results in an out-of-equilibrium situation near the inner edge. When this occurs over a downtail extent comparable to the half-thickness of the plasma sheet, collapse ensues and forces thinning of the plasma sheet whereby conditions favorable to reconnection occur. This scenario for substorm onset is consistent with observed upward fluxes of ions, parallel potential drops, and observations of substorm onset. These observations include near Earth onset, pseudobreakups, the substorm current wedge, and local variations of plasma-sheet thickness.

  6. Convection and Substorms - Paradigms of Magnetospheric Phenomenology

    NASA Astrophysics Data System (ADS)

    Kennel, Charles F.

    The magnetosphere is the region where cosmic rays and the solar wind interact with the Earth's magnetic field, creating such phenomena as the northern lights and other aurorae. The configuration and dynamics of the magnetosphere are of interest to planetary physicists, geophysicists, plasma astrophysicists, and to scientists planning space missions. The circulation of solar wind plasma in the magnetosphere and substorms have long been used as the principle paradigms for studying this vital region. Charles F. Kennel, a leading scientist in the field, here presents a synthesis of the convection and substorm literatures, and an analysis of convection and substorm interactions; he also suggests that the currently accepted steady reconnection model may be advantageously replaced by a model of multiple tail reconnection events, in which many mutually interdependent reconnections occur. Written in an accessible, non-mathematical style, this book introduces the reader to the exciting discoveries in this fast-growing field.

  7. Magnetospheric Substorms and Tail Dynamics

    NASA Technical Reports Server (NTRS)

    Hughes, W. Jeffrey

    1998-01-01

    This grant funded several studies of magnetospheric substorms and their effect on the dynamics of the earth's geomagnetic tail. We completed an extensive study of plasmoids, plasma/magnetic field structures that travel rapidly down the tail, using data from the ISEE 3 and IMP 8 spacecraft. This study formed the PhD thesis of Mark Moldwin. We found that magnetically plasmoids are better described as flux-ropes (twisted magnetic flux tubes) rather than plasma bubbles, as had been generally regarded up to that point (Moldwin and Hughes, 1990; 1991). We published several examples of plasmoids observed first in the near tail by IMP 8 and later in the distant tail by ISEE 3, confirming their velocities down tail. We showed how the passage of plasmoids distorts the plasma sheet. We completed the first extensive statistical survey of plasmoids that showed how plasmoids evolve as they move down tail from their formation around 30 RE to ISEE 3 apogee at 240 RE. We established a one-to-one correspondence between the observation of plasmoids in the distant tail and substorm onsets at earth or in the near tail. And we showed that there is a class of plasmoid-like structures that move slowly earthward, especially following weak substorms during northward IMF. Collectively this work constituted the most extensive study of plasmoids prior to the work that has now been done with the GEOTAIL spacecraft. Following our work on plasmoids, we turned our attention to signatures of substorm onset observed in the inner magnetosphere near geosynchronous orbit, especially signatures observed by the CRRES satellite. Using data from the magnetometer, electric field probe, plasma wave instrument, and low energy plasma instrument on CRRES we were able to better document substorm onsets in the inner magnetosphere than had been possible previously. Detailed calculation of the Poynting flux showed energy exchange between the magnetosphere and ionosphere, and a short burst of tailward convective

  8. Communications Magnetospheric Substorms.

    DTIC Science & Technology

    1983-01-17

    increases with either an increase in solar wind velocity or a decrease in the angle of the interplanetary magnetic field with respect to the earth- sun ...symmetry produced by changes in the j orientation of the dipole with respect to the earth- sun line. Paper (46) showed very clearly that the synchronous field...57 (12), 993, 1976. - 36 - 34. Barfield, J.N. and R.1L. Mc:l’herron, MuItiple-synchrolous satellite observations of substorm-associ’ated field- aliged

  9. Substorms - Future of magnetospheric substorm-storm research

    SciTech Connect

    Akasofu, S.I. )

    1989-04-01

    Seven approaches and/or areas of magnetospheric substorm and storm science which should be emphasized in future research are briefly discussed. They are: the combining of groups of researchers who study magnetic storms and substorms in terms of magnetic reconnection with those that do not, the possible use of a magnetosphere-ionosphere coupling model to merge the groups, the development of improved input-output relationships, the complementing of satellite and ground-based observations, the need for global imaging of the magnetosphere, the complementing of observations with computer simulations, and the need to study the causes of changes in the north-south component of the IMF. 36 refs.

  10. Evidence for particle acceleration during magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Lopez, Ramon E.; Baker, Daniel N.

    1994-01-01

    Magnetospheric substorms represent the episodic dissipation of energy stored in the geomagnetic tail that was previously extracted from the solar wind. This energy release produces activity throughout the entire magnetosphere-ionosphere system, and it results in a wide variety of phenomena such as auroral intensifications and the generation of new current systems. All of these phenomena involve the acceleration of particles, sometimes up to several MeV. We present a brief overview of substorm phenomenology. We then review some of the evidence for particle acceleration in Earth's magnetosphere during substorms. Such in-situ observations in this most accessible of all cosmic plasma domains may hold important clues to understanding acceleration processes in more distant astrophysical systems.

  11. Evidence for particle acceleration during magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Lopez, Ramon E.; Baker, Daniel N.

    1994-01-01

    Magnetospheric substorms represent the episodic dissipation of energy stored in the geomagnetic tail that was previously extracted from the solar wind. This energy release produces activity throughout the entire magnetosphere-ionosphere system, and it results in a wide variety of phenomena such as auroral intensifications and the generation of new current systems. All of these phenomena involve the acceleration of particles, sometimes up to several MeV. We present a brief overview of substorm phenomenology. We then review some of the evidence for particle acceleration in Earth's magnetosphere during substorms. Such in-situ observations in this most accessible of all cosmic plasma domains may hold important clues to understanding acceleration processes in more distant astrophysical systems.

  12. Extremely Intense Magnetospheric Substorms : External Triggering? Preconditioning?

    NASA Astrophysics Data System (ADS)

    Tsurutani, Bruce; Echer, Ezequiel; Hajra, Rajkumar

    2016-07-01

    We study particularly intense substorms using a variety of near-Earth spacecraft data and ground observations. We will relate the solar cycle dependences of events, determine whether the supersubstorms are externally or internally triggered, and their relationship to other factors such as magnetospheric preconditioning. If time permits, we will explore the details of the events and whether they are similar to regular (Akasofu, 1964) substorms or not. These intense substorms are an important feature of space weather since they may be responsible for power outages.

  13. Midday auroras and magnetospheric substorms.

    NASA Technical Reports Server (NTRS)

    Akasofu, S. I.

    1972-01-01

    Auroral activity in the midday sector is examined in some detail on the basis of all-sky photographs taken from Pyramida, Spitzbergen. The equatorward motion of the midday auroras observed during substorms and the subsequent poleward shift during the recovery phase are discussed.

  14. The relationship between the magnetosphere and magnetospheric/auroral substorms

    NASA Astrophysics Data System (ADS)

    Akasofu, S.-I.

    2013-03-01

    On the basis of auroral and polar magnetic substorm studies, the relationship between the solar wind-magnetosphere dynamo (the DD dynamo) current and the substorm dynamo (the UL dynamo) current is studied. The characteristics of both the DD and UL currents reveal why auroral substorms consist of the three distinct phases after the input power ɛ is increased above 1018 erg s-1. (a) The growth phase; the magnetosphere can accumulate magnetic energy for auroral substorms, when the ionosphere cannot dissipate the power before the expansion phase. (b) The expansion phase; the magnetosphere releases the accumulated magnetic energy during the growth phase in a pulse-like manner in a few hours, because it tries to stabilize itself when the accumulated energy reaches to about 1023 erg s-1. (c) The recovery phase; the magnetosphere becomes an ordinary dissipative system after the expansion phase, because the ionosphere becomes capable of dissipating the power with the rate of 1018 ~ 1019 erg s-1. On the basis of the above conclusion, it is suggested that the magnetosphere accomplishes the pulse-like release process (resulting in spectacular auroral activities) by producing plasma instabilities in the current sheet, thus reducing the current. The resulting contraction of the magnetic field lines (expending the accumulated magnetic energy), together with break down of the "frozen-in" field condition at distances of less than 10 RE, establishes the substorm dynamo that generates an earthward electric field (Lui and Kamide, 2003; Akasofu, 2011). It is this electric field which manifests as the expansion phase. A recent satellite observation at a distance of as close as 8.1 RE by Lui (2011) seems to support strongly the occurrence of the chain of processes suggested in the above. It is hoped that although the concept presented here is very crude, it will serve in providing one way of studying the three phases of auroral substorms. In turn, a better understanding of auroral

  15. A boundary layer model for magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Rostoker, Gordon; Eastman, Tim

    1987-01-01

    An alternative framework for understanding magnetospheric substorm activity is presented. It is argued that observations of magnetic field and plasma flow variations in the magnetotail can be explained in terms of the passage of the plasma sheet boundary layer over the satellite detecting the tail signatures. It is shown that field-aligned currents and particle acceleration processes on magnetic field lines threading the ionospheric Harang discontinuity lead to the distinctive particle and field signatures observed in the magnetotail during substorms. It is demonstrated that edge effects of field-aligned currents associated with the westward traveling surge can lead to the negative B(z) perturbations observed in the tail that are presently attributed to observations made on the anti-earthward side of a near-earth neutral line. Finally, it is shown that the model can provide a physical explanation of both the driven system and the loading-unloading system whose combined effects provide the observed substorm perturbation pattern in the magnetosphere and ionosphere.

  16. The earth's magnetosphere under continued forcing - Substorm activity during the passage of an interplanetary magnetic cloud

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Freeman, M. P.; Burlaga, L. F.; Lepping, R. P.; Takahashi, K.

    1993-01-01

    Magnetic field and energetic particle observations from six spacecraft in the near-earth magnetotail are described and combined with ground magnetograms to document for the first time the magnetospheric substorm activity during a 30-hour long transit of an interplanetary cloud at 1 AU. During an earlier 11-hr interval when B(z) was continuously positive, the magnetosphere was quiescent, while in a later 18-hr interval when B(z) was uninterruptedly negative a large magnetic storm was set off. In the latter interval the substorm onsets recurred on average every 50 min. Their average recurrence frequency remained relatively undiminished even when the magnetic cloud B(z) and other measures of the interplanetary energy input decreased considerably. These results concur with current models of magnetospheric substorms based on deterministic nonlinear dynamics. The substorm onset occurred when the cloud's magnetic field had a persistent northward component but was predominantly westward pointing.

  17. Study of a small magnetospheric substorm

    NASA Technical Reports Server (NTRS)

    Johnstone, A. D.; Boyd, J. S.; Davis, T. N.

    1974-01-01

    Data from a rocket launched into the expansion phase of an auroral substorm have been compared with data from numerous ground stations and several space vehicles. It is shown that this magnetic and auroral substorm has most of the features of larger substorms; thus it is implied that the same plasma processes are involved in all substorms. Some evidence is presented to link the auroral breakup with the field lines conjugate to the inner edge of the plasma sheet. The implications of these two results for substorm morphology and the triggering mechanism of the substorm instability are discussed. It is concluded that spatial gradients in plasma temperature are a likely cause.

  18. Origins and Transport of Ions during Magnetospheric Substorms

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, Maha; El-Alaoui, Mostafa; Peroomian, Vahe; Raeder, Joachim; Walker, Ray J.; Frank, L. A.; Paterson, W. R.

    1999-01-01

    We investigate the origins and the transport of ions observed in the near-Earth plasma sheet during the growth and expansion phases of a magnetospheric substorm that occurred on November 24, 1996. Ions observed at Geotail were traced backward in time in time-dependent magnetic and electric fields to determine their origins and the acceleration mechanisms responsible for their energization. Results from this investigation indicate that, during the growth phase of the substorm, most of the ions reaching Geotail had origins in the low latitude boundary layer (LLBL) and had alread@, entered the magnetosphere when the growth phase began. Late in the growth phase and in the expansion phase a higher proportion of the ions reaching Geotail had their origin in the plasma mantle. Indeed, during the expansion phase more than 90% of the ions seen by Geotail were from the mantle. The ions were accelerated enroute to the spacecraft; however, most of the ions' energy gain was achieved by non-adiabatic acceleration while crossing the equatorial current sheet just prior to their detection by Geotail. In general, the plasma mantle from both southern and northern hemispheres supplied non-adiabatic ions to Geotail, whereas the LLBL supplied mostly adiabatic ions to the distributions measured by the spacecraft.

  19. Equatorward shift of the cleft during magnetospheric substorms as observed by Isis 1

    NASA Technical Reports Server (NTRS)

    Yasuhara, F.; Akasofu, S.-I.; Winningham, J. D.; Heikkila , W. J.

    1973-01-01

    Isis 1 satellite observations of the cleft position during magnetospheric substorms show that the cleft shifts equatorward as the interplanetary B sub z component turns southward and substorm activity increases and that it shifts back toward higher latitudes as substorm activity subsides and B sub z returns northward. Also, unusually low latitudes for the cleft (less than 70 deg invariant latitude) were found during geomagnetic storms with significant Dst values and large negative B sub z values. Significant shifts occur in the cleft location with no accompanying effect seen in the AE index; however, B sub z is observed to be southward during these periods.

  20. Equatorward shift of the cleft during magnetospheric substorms as observed by Isis 1

    NASA Technical Reports Server (NTRS)

    Yasuhara, F.; Akasofu, S.-I.; Winningham, J. D.; Heikkila , W. J.

    1973-01-01

    Isis 1 satellite observations of the cleft position during magnetospheric substorms show that the cleft shifts equatorward as the interplanetary B sub z component turns southward and substorm activity increases and that it shifts back toward higher latitudes as substorm activity subsides and B sub z returns northward. Also, unusually low latitudes for the cleft (less than 70 deg invariant latitude) were found during geomagnetic storms with significant Dst values and large negative B sub z values. Significant shifts occur in the cleft location with no accompanying effect seen in the AE index; however, B sub z is observed to be southward during these periods.

  1. Boundary layer dynamics in the description of magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Eastman, T. E.; Rostoker, G.; Frank, L. A.; Huang, C. Y.; Mitchell, D. G.

    1988-01-01

    This paper presents an analysis of eleven magnetospheric substorm events for which good-quality ground-based magnetometer data and ISEE satellite data were both available. It is shown that the magnetotail particle and field observations associated with a substorm expansive phase can be explained through the spatial movement of the boundary layers and central plasma sheet in the magnetotail. The sweeping of these regions past the satellite, even in the absence of temporal variations within the various regions, can lead to a set of plasma flow observations typical of what is observed in the magnetotail during substorm activity.

  2. Quantitative Simulation of a Magnetospheric Substorm. 2. Comparison with Observations,

    DTIC Science & Technology

    1980-01-23

    we overestimated the polar-boundary potential drop; consequently the p) asma -sheet ions were injected deeper into the magnetosphere than was the case...Magnetospheric Substorms and Related Plasma Processes, Los Alamos, New Mexico , October 1978 and to be published in Astrophysics and Space Science Library...and Related Plasma Processes, Los Alamos, New Mexico , October 1978, published in Astrophysics and Space Science Library Series,p.14 3, Yasuhara, F., and

  3. Advances in magnetospheric storm and substorm research - 1989-1991

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1992-01-01

    Recent advances in magnetospheric storm and substorm research is reviewed, with emphasis on how the large southward fields and high velocities produced in the solar wind influence the magnetosphere and cause the enhanced transfer of energy, momentum, and mass to the magnetosphere. Overwhelming evidence indicates that the southward interplanetary magnetic field is the primary controlling factor in the generation of substorms. The immediate cause of the expansion phase onset is controversial, but the suddenness of the onset is suggestive of an instability that disrupts the cross-tail currents. Measurements increasingly suggest the region of 7-10 R sub E near midnight as the likely point of origin, but it is not clear that the long-popular tearing mode can go unstable this close to the earth, where it may be stabilized by a small northward field component.

  4. Magnetic field signatures of substorms on high latitudes field lines in the nighttime magnetosphere

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1972-01-01

    Two types of magnetic field changes are repeatedly observed in the high latitude nightside magnetosphere in association with magnetic substorms. One type is characterized by sudden decrease in the field strength, accompanied by an abrupt perturbation in the field declination angle. These changes are attributed to field aligned-sheet currents flowing on the high latitude boundary of an expanding plasma sheet following substorms. Single sheets of field-aligned currents on this boundary tend to flow toward the earth in the morning quadrant and away in the evening. Multiple sheets of current may also occur, with the direction of the high latitude sheet generally being the same as for a single sheet. A second type of field change is a decrease in field inclination during substorms. This is regarded as a manifestation of the changing field configuration during substorms and can be described in terms of azimuthal currents.

  5. Magnetospheric substorms in the distant magnetotail observed by Imp 3.

    NASA Technical Reports Server (NTRS)

    Meng, C. I.; Akasofu, S.; Kawasaki, K.; Hones, E. W., Jr.

    1971-01-01

    Study of variations of the magnetic field and plasma sheet in the distant magnetotail (20 to 40 earth radii) during magnetospheric substorms on the basis of the Imp 3 magnetic-field and particle data. Depending on the locations of the satellite with respect to the boundary of the plasma sheet, the variations differ greatly. However, the present results and the results of other workers give a clear indication of an increase of the magnitude of the field outside the plasma sheet and of the simultaneous ?thinning' of the plasma sheet during an early phase of substorms. At about the maximum epoch or during the recovery phase of substorms, the plasma sheet expands and appears to be inflated to at least the presubstorm level. Furthermore, a large excessive flux of the magnetic (approximately equal to Z component) field, as compared with the flux of the original dipole field, appears across the neutral sheet.

  6. Magnetospheric substorms in the distant magnetotail observed by Imp 3.

    NASA Technical Reports Server (NTRS)

    Meng, C. I.; Akasofu, S.; Kawasaki, K.; Hones, E. W., Jr.

    1971-01-01

    Study of variations of the magnetic field and plasma sheet in the distant magnetotail (20 to 40 earth radii) during magnetospheric substorms on the basis of the Imp 3 magnetic-field and particle data. Depending on the locations of the satellite with respect to the boundary of the plasma sheet, the variations differ greatly. However, the present results and the results of other workers give a clear indication of an increase of the magnitude of the field outside the plasma sheet and of the simultaneous ?thinning' of the plasma sheet during an early phase of substorms. At about the maximum epoch or during the recovery phase of substorms, the plasma sheet expands and appears to be inflated to at least the presubstorm level. Furthermore, a large excessive flux of the magnetic (approximately equal to Z component) field, as compared with the flux of the original dipole field, appears across the neutral sheet.

  7. Energy Coupling Between the Ionosphere and Inner Magnetosphere Related to Substorm Onset

    NASA Technical Reports Server (NTRS)

    Maynard, Nelson C.

    1999-01-01

    The investigation of substorm effects in the inner magnetosphere with CRRES data looked in detail at over 50 substorms relative to signatures of onset and early expansion phases. The accomplishments of the project are: Determined perpendicular Poynting flux at CRRES in the inner magnetosphere at substorm onset, including primary direction is azimuthal, not radial, indicating a local source, no obvious signal from the magnetotail to trigger onset, strongly supports substorm onset location near the inner edge of the plasma sheet and process is local and a strong function of Magnetosphere-ionosphere (MI) coupling. We also developed near geosynchronous onset (NGO) model for substorm onset and expansion.

  8. Association of Energetic Neutral Atom Bursts and Magnetospheric Substorms

    NASA Technical Reports Server (NTRS)

    Jorgensen, A. M.; Kepko, L.; Henderson, M. G.; Spence, H. E.; Reeves, G. D.; Sigwarth, J. B.; Frank, L. A.

    2000-01-01

    In this paper we present evidence that short-lived bursts of energetic neutral atoms (ENAs) observed with the Comprehensive Energetic Particle and Pitch Angle Distribution/Imaging Proton Spectrometer (CEPPAD/IPS) instrument on the Polar spacecraft are signatures of substorms. The IPS was designed primarily to measure ions in situ, with energies between 17.5 and 1500 keV. However, it has also proven to be a very capable ENA imager in the range 17.5 keV to a couple hundred keV. It was expected that some ENA signatures of the storm time ring current would be observed. Interestingly, IPS also routinely measures weaker, shorter-lived, and more spatially confined bursts of ENAs with duration from a few tens of minutes to a few hours and appearing once or twice a day. One of these bursts was quickly associated with magnetospheric and auroral substorm activity and has been reported in the literature [Henderson et al., 19971. In this paper we characterize ENA bursts observed from Polar and establish statistically their association with classic substorm signatures (global auroral onsets, electron and ion injections, AL drops, and Pi2 onsets). We conclude that -90% of the observed ENA bursts are associated with classic substorms and thus represent a new type of substorm signature.

  9. Association of Energetic Neutral Atom Bursts and Magnetospheric Substorms

    NASA Technical Reports Server (NTRS)

    Jorgensen, A. M.; Kepko, L.; Henderson, M. G.; Spence, H. E.; Reeves, G. D.; Sigwarth, J. B.; Frank, L. A.

    2000-01-01

    In this paper we present evidence that short-lived bursts of energetic neutral atoms (ENAs) observed with the Comprehensive Energetic Particle and Pitch Angle Distribution/Imaging Proton Spectrometer (CEPPAD/IPS) instrument on the Polar spacecraft are signatures of substorms. The IPS was designed primarily to measure ions in situ, with energies between 17.5 and 1500 keV. However, it has also proven to be a very capable ENA imager in the range 17.5 keV to a couple hundred keV. It was expected that some ENA signatures of the storm time ring current would be observed. Interestingly, IPS also routinely measures weaker, shorter-lived, and more spatially confined bursts of ENAs with duration from a few tens of minutes to a few hours and appearing once or twice a day. One of these bursts was quickly associated with magnetospheric and auroral substorm activity and has been reported in the literature [Henderson et al., 19971. In this paper we characterize ENA bursts observed from Polar and establish statistically their association with classic substorm signatures (global auroral onsets, electron and ion injections, AL drops, and Pi2 onsets). We conclude that -90% of the observed ENA bursts are associated with classic substorms and thus represent a new type of substorm signature.

  10. Substorm Injected Energetic Electrons and Ions Deeply into the Inner Magnetosphere Observed by BD-IES and Van Allan Probes

    NASA Astrophysics Data System (ADS)

    Zong, Qiugang

    2017-04-01

    When substorm injections are observed simultaneously with multiple spacecraft, they help elucidate potential mechanisms for particle transport and energization, a topic of great importance for understanding and modeling the magnetosphere. In the present paper, by using the data return from the BeiDa- IES (BD-IES) instrument onboard an inclined (55◦) geosynchronous orbit (IGSO) satellite together with geo-transfer orbit (GTO) Van Allen Probe A&B satellite, we analysis a substorm injection event occurred on Oct 16, 2015. During the substorm injection, the IES onboard IGSO is outbound while both Van Allen Probe A&B satellites are inbound. This configuration of multiple satellite trajectories provides a unique opportunity to investigate the inward and outward radial propagation of the substorm injection simultaneously. This substorm as indicated by AE/AL indices is closely related an IMF/solar wind discontinuity with a sharp change in the IMF Bz direction (northward turning). The innermost signature of this substorm injection has been detected by the Van Allen Probes A & B at L 3.7. The outermost signature, observed by the BD-IES, is found to be at L 10. This indicated that this substorm have a rather global effect rather than just a local effect. Further, we suggest that the electric fields carried by fast-mode compressional waves around the substorm injection are the most likely mechanism candidate for the injection signatures of electrons observed in the innermost and outermost inner magnetosphere.

  11. Substorms

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    2015-01-01

    This chapter deals with the essence of the magnetospheric substorm, the return of magnetic flux into the magnetosphere after disconnection from the solar wind magnetic field. There are three fundamental transport processes involved: (1) thinning of the tail plasma sheet and accompanying recession of the outer boundary of the dipolar magnetosphere during the growth phase, (2) flux transport along the tail toward that boundary after onset of tail reconnection, and (3) penetration of plasma and magnetic flux into the dipolar magnetosphere. The chapter then looks at corresponding processes in the Jupiter and Saturn magnetospheres and tails, which are strongly dominated by the fast planetary rotations. It elucidates some key aspects of the entry problem, albeit from a personal vantage point, and addresses the still open questions. Finally, the chapter addresses the correlation between solar wind ram pressure and auroral activity and brightness on Jupiter and Saturn.

  12. Vertical motions of the midlatitude F2 layer during magnetospheric substorms.

    NASA Technical Reports Server (NTRS)

    Park, C. G.; Meng, C.

    1971-01-01

    Use of ground-based ionosonde records from midlatitude stations during winter nights to study vertical motions of the F2 layer associated with magnetospheric substorms. The results show that during substorms the F2 layer is lifted upward in the premidnight sector and pushed downward in the postmidnight sector. These motions are interpreted in terms of E x B drifts, the electric field being eastward on the eveningside and westward on the morningside. The results emphasize the importance of substorm effects on the midlatitude F region and the potential of ground-based hf sounding techniques in studying magnetospheric substorms.

  13. Magnetospheric Multiscale (MMS) and Van Allen Probes Study of Substorm Injections

    NASA Astrophysics Data System (ADS)

    Baker, D. N.; Jaynes, A. N.; Leonard, T. W.; Cohen, I.; Mauk, B.; Fennell, J. F.

    2016-12-01

    We study episodes of significantly southward interplanetary magnetic field (IMF) that occurred with periods of high solar wind speed (Vsw500 km/s). We focus on events during the orbital phases with MMS spacecraft apogees in the Earth's local midnight region. Key events during MMS magnetotail passages in 2015 and 2016 show that the magnetosphere progresses through a clear sequence of energy-loading and stress-developing states until the entire system suddenly reconfigures. Energetic electrons, plasma, and magnetic fields measured by the four MMS spacecraft reveal sharp dipolarization front characteristics. It is seen that magnetospheric substorm activity provides a "seed" electron population as observed by MMS particle sensors. Isolated particle injections at higher altitudes are closely related to enhancements in electron flux deeper within the inner magnetosphere. Particle injection events observed by the four MMS spacecraft subsequently feed the enhancement of the outer radiation belt observed by Van Allen Probes mission sensors.

  14. The Earth's magnetosphere under continued forcing: Substorm activity during the passage of an interplanetary magnetic cloud

    SciTech Connect

    Farrugia, C.J.; Burlaga, L.F.; Lepping, R.P. ); Freeman, M.P. ); Takahashi, K. )

    1993-05-01

    This is the third of three papers dealing with the interaction of an interplanetary magnetic field with the earth's magnetosphere in Jan 1988. Here the authors report on substorm observations made during this time period. They sampled information from six spacecraft and a larger number of ground based systems to serve as signals for the initiation of substorm behavior. They relate the interplanetary magnetic field and plasma conditions to the time of observation of substorm initiation. Current models tie substorm occurrence to magnetic reconnection in the magnetosphere. The IMF B[sub y] and B[sub z] components varied slowly over a range of 20 nT on both sides of zero during this observation period. During the period of northward IMF the magnetosphere was quiescent, but during the period of southward IMF a large magnetic storm was initiated. During this interval substorms were observed roughly every 50 minutes.

  15. Linking Space-Borne and Ground-Based Observations Observed Around Substorm Onset to Magnetospheric Processes

    NASA Technical Reports Server (NTRS)

    Kepko, Larry; Spanswick, Emma; Angelopoulos, Vassilis; Donovan, Eric

    2011-01-01

    The combined THEMIS five spacecraft in-situ and ground magnetic and camera arrays have advanced considerably our understanding of the causal relationship between midtail plasma flows, transient ionospheric features, and ground magnetic signatures. In particular, recent work has shown a connection between equatorward moving visible ionospheric transients and substorm onset, in both 6300 nm and white-light emissions. Although both observations detail pre-onset auroral features the interpretations differ substantially. We first provide a brief summary of these observations, highlighting in particular areas where the two observations differ, and suggest reasons for the differences. We then detail how these observations relate to dynamical magnetospheric processes, and show how they constrain models of transient convection. Next, we pull together observations and models of Pi2 generation, substorm current wedge (SCW) initiation and dipolarization to present a self-consistent description of the dynamical processes and communicative pathways that occur just prior to and during substorm expansion onset. Finally, we present a summary of open questions and suggest a roadmap for future work.

  16. New perspectives on substorm injections

    SciTech Connect

    Reeves, G.D.

    1998-12-01

    There has been significant progress in understanding substorm injections since the Third International Conference on Substorms in 1996. Progress has come from a combination of new theories, quantitative modeling, and observations--particularly multi-satellite observations. There is now mounting evidence that fast convective flows are the mechanism that directly couples substorm processes in the mid tail, where reconnection occurs, with substorm processes the inner magnetosphere where Pi2 pulsations, auroral breakups, and substorm injections occur. This paper presents evidence that those flows combined with an earthward-propagating compressional wave are responsible for substorm injections and discusses how that model can account for various substorm injection signatures.

  17. Energetic Electron Transport in the Inner Magnetosphere During Geomagnetic Storms and Substorms

    NASA Technical Reports Server (NTRS)

    McKenzie, D. L.; Anderson, P. C.

    2005-01-01

    We propose to examine the relationship of geomagnetic storms and substorms and the transport of energetic particles in the inner magnetosphere using measurements of the auroral X-ray emissions by PIXIE. PIXIE provides a global view of the auroral oval for the extended periods of time required to study stormtime phenomena. Its unique energy response and global view allow separation of stormtime particle transport driven by strong magnetospheric electric fields from substorm particle transport driven by magnetic-field dipolarization and subsequent particle injection. The relative importance of substorms in releasing stored magnetospheric energy during storms and injecting particles into the inner magnetosphere and the ring current is currently hotly debated. The distribution of particles in the inner magnetosphere is often inferred from measurements of the precipitating auroral particles. Thus, the global distributions of the characteristics of energetic precipitating particles during storms and substorms are extremely important inputs to any description or model of the geospace environment and the Sun-Earth connection. We propose to use PIXIE observations and modeling of the transport of energetic electrons to examine the relationship between storms and substorms.

  18. A comparison of substorms occurring during magnetic storms with those occurring during quiet times

    NASA Astrophysics Data System (ADS)

    McPherron, R. L.; Hsu, T.-S.

    2002-09-01

    It has been suggested that there may be a fundamental difference between substorms that occur during magnetic storms and those that occur at other times. [1996] presented evidence that there is no obvious change in lobe field in "quiet time" substorms but that "storm time" substorms exhibit the classic pattern of storage and release of lobe field energy. This result led them to speculate that the former are caused by current sheet disruption, while the latter are caused by reconnection of lobe flux. In this paper we examine their hypothesis with a much larger data set using definitions of the two types of substorms similar to theirs, as well as additional more restrictive definitions of these classes of events. Our results show that the only differences between the various classes are the absolute value of the lobe field and the size of the changes. When the data are normalized to unit field amplitude, we find that the percent change during storm time and non-storm time substorms is nearly the same. The above conclusions are demonstrated with superposed epoch analysis of lobe field (Bt and Bz) for four classes of substorms: active times (Dst < -50 nT, mostly recovery phase), main phase substorms, non-storm times (Dst > -25 nT), and quiet time substorms (no evidence of storm in Dst). Epoch zero for the analysis was taken as the main substorm onset (Pi2 onset closest to sharp break in AL index). Our results suggest that there is no qualitative distinction between the various classes of substorms, and so they are all likely to be caused by the same mechanism.

  19. Energy supply processes for magnetospheric substorms and solar flares - Tippy bucket model or pitcher model?

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1985-01-01

    In the past, both magnetospheric substorms and solar flares have almost exclusively been discussed in terms of explosive magnetic reconnection. Such a model may conceptually be illustrated by the so-called 'tippy-bucket model', which causes sudden unloading processes, namely a sudden (catastrophic, stochastic, and unpredictable) conversion of stored magnetic energy. However, recent observations indicate that magnetospheric substorms can be understood as a result of a directly driven process which can conceptually be illustrated by the 'pitcher model' in which the output rate varies in harmony with the input rate. It is also possible that solar flare phenomena are directly driven by a photospheric dynamo. Thus, explosive magnetic reconnection may simply be an unworkable hypothesis and may not be a puzzle to be solved as the primary energy supply process for magnetospheric substorms and solar flares.

  20. Magnetospheric substorms are strongly modulated by interplanetary high-speed streams

    NASA Astrophysics Data System (ADS)

    Tanskanen, E. I.; Slavin, J. A.; Tanskanen, A. J.; Viljanen, A.; Pulkkinen, T. I.; Koskinen, H. E. J.; Pulkkinen, A.; Eastwood, J.

    2005-08-01

    The occurrence of substorms was examined over a complete 11-year solar cycle, identifying over 5000 substorms. It was found that high-speed streams strongly modulate the substorm occurrence rate, peak amplitude and ionospheric dissipation in the form of Joule heating and auroral electron precipitation. Substorms occurring during the years of frequent interplanetary high-speed streams (1994 and 2003) are 32% more intense, on average, and transfer twice as much magnetic energy to the auroral ionosphere as the substorms occurring during the years of few or no high-speed streams (1993, 1995-2002). To characterize and to predict the substorm activity we form a new measure, the substorm activity parameter Rsu, which we expect to become a powerful tool in analyzing the near-Earth space climate.

  1. Common solar wind drivers behind magnetic storm - magnetospheric substorm dependency

    NASA Astrophysics Data System (ADS)

    Balasis, Georgios; Runge, Jakob; Daglis, Ioannis A.; Papadimitriou, Constantinos; Donner, Reik E.

    2017-04-01

    The storm-substorm relationship is one of the most controversial aspects of geospace magnetic storm dynamics and one of the unresolved topics of solar-terrestrial coupling. Here we investigate the statistical dependencies between storm and substorm indices in conjunction with multiple relevant solar wind variables with an information-theoretic causal inference approach. We find that the vertical component of the interplanetary magnetic field is the strongest driver of both storms and substorms. Importantly, this common driver explains the transfer entropy between substorms and storms found by a previous bivariate analysis. These results hold during both a year close to solar maximum (2001) and minimum (2008) and suggest that, at least based on the analyzed indices, there is no statistical evidence of a direct or indirect information transfer and, therefore, likely no physical mechanism by which substorms drive storms or vice versa.

  2. Changes in Magnetosphere-Ionosphere Coupling and FACs Associated with Substorm Onset (Invited)

    NASA Astrophysics Data System (ADS)

    Murphy, K. R.; Mann, I. R.; Rae, I. J.; Waters, C. L.; Anderson, B. J.; Korth, H.; Milling, D. K.; Singer, H. J.; Frey, H. U.

    2013-12-01

    Field aligned currents (FACs) are crucial for the communication of information between the ionosphere and magnetosphere. Utilising in-situ observations from the Iridium constellation and Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) we provide detailed observations of the FAC topology through the substorm growth and expansion phases. In particular, for an isolated substorm on 16 February 2010 we demonstrate a clear and localized reduction in the FACs at least 6 minutes prior to auroral onset. A new auroral arc forms in the region of reduced FAC on closed field lines and initially expands azimuthally in wave like fashion. This newly formed arc continues to brighten and expands poleward signifying the start of the substorm expansion phase. We argue that the change in FACs observed prior to onset is the result of a change in the magnetosphere-ionosphere (M-I) coupling in a region local to the subsequent auroral onset. Such a change implies an important role for M-I coupling in destabilising the near-Earth tail during magnetospheric substorms and perhaps more importantly in selecting the location in the ionosphere where auroral onset begins. Further, we provide, a comprehensive in-situ two-dimensional view of the FAC topology associated with the substorm current wedge and westward traveling surge during the substorm expansion phase. We demonstrate that these current structures, when integrated with latitude to produce a net FAC as a function of MLT, have the same structure as the equivalent line current system comprising the SCW. Moreover, regions of upward FAC are associated with discrete auroral forms during the substorm expansion phase.

  3. The Physical Elements of Onset of the Magnetospheric Substorm

    NASA Technical Reports Server (NTRS)

    Erickson, Gary M.

    1997-01-01

    During this reporting period effort continued in the areas: (1) understanding the mechanisms responsible for substorm onset, and (2) application of a fundamental description of field-aligned currents and parallel electric fields to the plasma-sheet boundary layer.

  4. Quasi-static evolution of the magnetosphere: The substorm growth phase

    NASA Astrophysics Data System (ADS)

    Kropotkin, A. P.; Lui, A. T. Y.

    1995-09-01

    The growth phase of a substorm is marked by ``energy loading'' in the magnetosphere prior to energy dissipation in the substorm expansion phase. This loading takes place primarily in the geomagnetic tail and is identified by the growth of total magnetic flux in the tail lobes, the increase of magnetic field intensity in the near-Earth portion of the tail, and the field line stretching leading to thinning of the plasma sheet in that region where a ``neck'' is thus formed. The last two processes are shown here to be natural consequences of the magnetic flux accumulation by considering theoretically a quasi-static evolution of tail equilibrium. One of the model inferences in the growth phase is a strong diminishment of the dimension of the transition region in the nightside where field lines change from dipolar to tail-like. This accounts for the growth phase development often seen in the near-synchronous region. This study also reveals a qualitative difference between the growth phase and the ``quiet'' condition or the ``ground state:'' the tail lobe flux should exceed a certain threshold for the neck formation to occur and the size of the transition region to diminish.

  5. What Might We Learn About Magnetospheric Substorms at the Earth from the MESSENGER Measurements at Mercury?

    NASA Technical Reports Server (NTRS)

    Slavin, James A.

    2008-01-01

    Satellite observations at the Earth, supported by theory and modeling, have established a close connection between the episodes of intense magnetospheric convection termed substorms and the occurrence of magnetic reconnection. Magnetic reconnection at the dayside magnetopause results in strong energy input to the magnetosphere. This energy can either be stored or used immediately to power the magnetospheric convection that produces the phenomena that collectively define the 'substorm.' However, many aspects of magnetic reconnection and the dynamic response of the coupled solar wind - magnetosphere - ionosphere system at the Earth during substorms remain poorly understood. For example, the rate of magnetic reconnection is thought to be proportional to the local Alfven speed, but the limited range of changes in this solar wind parameter at 1 AU have made it difficult to detect its influence over energy input to the Earth's magnetosphere. In addition, the electrical conductance of the ionosphere and how it changes in response to auroral charged particle precipitation are hypothesized to play a critical role in the development of substorms, but the nature of this electrodynamic interaction remain difficult to deduce from Earth observations alone. The amount of energy the terrestrial magnetosphere can store in its tail, the duration of the storage, and the trigger(s) for its dissipation are all thought to be determined by not only the microphysics of the cross-tail current layer, but also the properties of the coupled magnetosphere - ionosphere system. Again, the separation of microphysics effects from system response has proved very difficult using measurements taken only at the Earth. If MESSENGER'S charged particle and magnetic field measurements confirm the occurrence of terrestrial-style substorms in Mercury's miniature magnetosphere, then it may be possible to determine how magnetospheric convection, field-aligned currents, charged particle acceleration

  6. Event study combining magnetospheric and ionospheric perspectives of the substorm current wedge modeling

    NASA Astrophysics Data System (ADS)

    Sergeev, V. A.; Nikolaev, A. V.; Kubyshkina, M. V.; Tsyganenko, N. A.; Singer, H. J.; Rodriguez, J. V.; Angelopoulos, V.; Nakamura, R.; Milan, S. E.; Coxon, J. C.; Anderson, B. J.; Korth, H.

    2014-12-01

    Unprecedented spacecraft and instrumental coverage and the isolated nature and distinct step-like development of a substorm on 17 March 2010 has allowed validation of the two-loop substorm current wedge model (SCW2L). We find a close spatiotemporal relationship of the SCW with many other essential signatures of substorm activity in the magnetotail and demonstrate its azimuthally localized structure and stepwise expansion in the magnetotail. We confirm that ground SCW diagnostics makes it possible to reconstruct and organize the azimuthal spatiotemporal substorm development pattern with accuracy better than 1 h magnetic local time (MLT) in the case of medium-scale substorm. The Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE)-based study of global field-aligned current distribution indicates that (a) the SCW-related field-aligned current system consists of simultaneously activated R1- and R2-type currents, (b) their net currents have a R1-sense, and (c) locations of net current peaks are consistent with the SCW edge locations inferred from midlatitude variations. Thanks to good azimuthal coverage of four GOES and three Time History of Events and Macroscale Interactions during Substorms spacecraft, we evaluated the intensities of the SCW R1- and R2-like current loops (using the SCW2L model) obtained from combined magnetospheric and ground midlatitude magnetic observations and found the net currents consistent (within a factor of 2) with the AMPERE-based estimate. We also ran an adaptive magnetospheric model and show that SCW2L model outperforms it in predicting the magnetic configuration changes during substorm dipolarizations.

  7. Dynamics of the AMPERE Region 1 Birkeland current oval during storms, substorms and steady magnetospheric convection

    NASA Astrophysics Data System (ADS)

    Baker, J. B.; Clausen, L.; Ruohoniemi, J. M.; Milan, S. E.; Kissinger, J.; Anderson, B. J.; Wing, S.

    2012-12-01

    Using radial current densities provided by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) we employ a fitting scheme to identify the location of the maximum Region 1 field-aligned (Birkeland) current at all magnetic local times. We call this parameter the "R1 oval" and we investigate its behavior during various modes of magnetospheric activity such as storms, substorms and steady magnetospheric convection (SMCs). Results show the following: (1) during substorms the radius of the R1 oval undergoes a cyclic inflation and contraction which matches the standard paradigm for substorm growth (loading) and expansion (unloading); (2) during SMCs the R1 oval is relatively steady consistent with balanced dayside and nightside reconnection during these events; and (3) during magnetic storms the size of the R1 oval is strongly correlated with the strength of the ring current specified by the Sym-H index. We also examine the behavior of the R1 oval in the northern and southern hemispheres simultaneously as a function of season in an effort to understand the role that internal magnetosphere-ionosphere coupling influences may play in modulating the response of the magnetosphere during these various types of events.

  8. Distinct Magnetospheric Responses to Southward IMF in Two Substorms

    NASA Technical Reports Server (NTRS)

    El-Alaoui, Mostafa; Ashour-Abdalla, M.; Richard, R. L.; Frank, L. A.; Paterson, W. R.; Sigwarth, J. B.

    2003-01-01

    Solar wind plasma parameters and the Interplanetary Magnetic Field (IMF) observed by the WIND spacecraft upstream of the bow shock were used as input to magnetohydrodynamic (MHD) simulations of two substorm events. The power deposited into the ionosphere due to electron precipitation was calculated both from VIS observations and from the simulations.

  9. Effect of magnetospheric substorms on asymptotic directions of arrival of cosmic ray relativistic protons

    NASA Astrophysics Data System (ADS)

    Pchelkin, V. V.

    2010-06-01

    The effect of magnetospheric storm on the propagation of relativistic protons has been analyzed. The method of trajectory calculations has been used to estimate changes in the reception cones for 21 stations, caused by the storm of July 19-20, 2000, accompanied by considerable saw-tooth substorm disturbances. It has been indicated that the degree of the substorm effect on the propagation of cosmic ray (CR) relativistic protons, registered with ground detectors, differs for different stations and depends on a distance of the particle trajectory from the localization of a substorm disturbance. The maximal effect for the considered substorm was found at Inuvik and McMurdo stations. Changes in the reception cone, caused by the substorm at these stations, were comparable or even larger than changes caused by the storm. Based on the calculations, the conclusion has been drawn that a disturbance (substorm) localized in space results in the appearance of relatively local zones on the Earth’s surface where characteristics of the asymptotic arrival of relativistic particles are changed.

  10. Theoretical magnetograms based on quantitative simulation of a magnetospheric substorm

    NASA Technical Reports Server (NTRS)

    Chen, C.-K.; Wolf, R. A.; Karty, J. L.; Harel, M.

    1982-01-01

    Substorm currents derived from the Rice University computer simulation of the September 19, 1976 substorm event are used to compute theoretical magnetograms as a function of universal time for various stations, integrating the Biot-Savart law over a maze of about 2700 wires and bands that carry the ring, Birkeland and horizontal ionospheric currents. A comparison of theoretical results with corresponding observations leads to a claim of general agreement, especially for stations at high and middle magnetic latitudes. Model results suggest that the ground magnetic field perturbations arise from complicated combinations of different kinds of currents, and that magnetic field disturbances due to different but related currents cancel each other out despite the inapplicability of Fukushima's (1973) theorem. It is also found that the dawn-dusk asymmetry in the horizontal magnetic field disturbance component at low latitudes is due to a net downward Birkeland current at noon, a net upward current at midnight, and, generally, antisunward-flowing electrojets.

  11. Theoretical magnetograms based on quantitative simulation of a magnetospheric substorm

    NASA Technical Reports Server (NTRS)

    Chen, C.-K.; Wolf, R. A.; Karty, J. L.; Harel, M.

    1982-01-01

    Substorm currents derived from the Rice University computer simulation of the September 19, 1976 substorm event are used to compute theoretical magnetograms as a function of universal time for various stations, integrating the Biot-Savart law over a maze of about 2700 wires and bands that carry the ring, Birkeland and horizontal ionospheric currents. A comparison of theoretical results with corresponding observations leads to a claim of general agreement, especially for stations at high and middle magnetic latitudes. Model results suggest that the ground magnetic field perturbations arise from complicated combinations of different kinds of currents, and that magnetic field disturbances due to different but related currents cancel each other out despite the inapplicability of Fukushima's (1973) theorem. It is also found that the dawn-dusk asymmetry in the horizontal magnetic field disturbance component at low latitudes is due to a net downward Birkeland current at noon, a net upward current at midnight, and, generally, antisunward-flowing electrojets.

  12. Dynamic substorm injections - Similar magnetospheric phenomena at earth and Mercury

    NASA Technical Reports Server (NTRS)

    Christon, S. P.; Feynman, J.; Slavin, J. A.

    1987-01-01

    Correlations between energetic electrons, plasma electrons, and magnetic fields during the Mercury 1 energetic particle events are examined and comparisons are made with several well-documented substorm injections at the earth. The data reveal that the B and B-prime events possess the same characteristics as single-point observations of terrestrial dynamic injections. Several recently discovered correlations between the energetic electrons, plasma electrons, and magnetic fields at Mercury are discussed.

  13. Magnetotail changes in relation to the solar wind magnetic field and magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Aubry, M. P.; Mcpherron, R. L.

    1970-01-01

    An attempt is made to understand some of the magnetotail dynamics by using simultaneous observations from several satellites: Explorers 33 and 35 in the solar wind, IMP 4 in the near magnetotail (30 RE), ATS 1, and OGO 5 in the magnetosphere. It was observed that in the main lobes of the tail the magnetic field increases slowly when the interplanetary magnetic field turns southward, and can decrease slowly after a substorm. The plasma sheet changes indicate a thinning when the interplanetary magnetic field turns southward and an expansion when it turns northward. When combined with the plasma sheet expansion, which has been observed to follow a substorm, these results allow a schematic view of the relations between the changes in the orientation of the solar wind magnetic field, the substorms, and the changes in the tail parameters to be developed.

  14. Magnetosphere-Ionosphere Coupling Processes in the Ionospheric Trough Region During Substorms

    NASA Astrophysics Data System (ADS)

    Zou, S.; Moldwin, M.; Nicolls, M. J.; Ridley, A. J.; Coster, A. J.; Yizengaw, E.; Lyons, L. R.; Donovan, E.

    2013-12-01

    The ionospheric troughs are regions of remarkable electron density depression at the subauroral and auroral latitudes, and are categorized into the mid-latitude trough or high-latitude trough, depending on their relative location to the auroral oval. Substorms are one fundamental element of geomagnetic activity, during which structured field-aligned currents (FACs) and convection flows develop in the subauroral and auroral ionosphere. The auroral/trough region is expected to experience severe electron density variations during substorms. Accurate specification of the trough dynamics during substorms and understanding its relationship with the structured FACs and convection flows are of important practical purpose, including providing observational foundations for assessing the attendant impact on navigation and communication. In addition, troughs are important since they map to magnetospheric boundaries allowing the remote sensing of magnetosphere-ionosphere coupling processes. In this talk, we discuss the dynamics of the mid-latitude and high-latitude troughs during substorms based on multi-instrument observations. Using GPS total electron content (TEC) data, we characterize the location and width of the mid-latitude trough through the substorm lifecycle and compare them with existing trough empirical models. Using a combination of incoherent scattering radar (ISR), GPS TEC, auroral imager and a data assimilative model, we investigate the relationship between the high-latitude trough and FACs as well as convection flows. The high-latitude trough is found to be collocated with a counter-clockwise convection flow vortex east of the Harang reversal region, and downward FACs as part of the substorm current system are suggested to be responsible for the high-latitude trough formation. In addition, complex ionospheric electron temperature within the high-latitude trough is found, i.e., increase in the E region while decrease in the F region. We discuss possible

  15. Micro- and meso-scale simulations of magnetospheric processes related to the aurora and substorm morphology

    NASA Technical Reports Server (NTRS)

    Swift, Daniel W.

    1991-01-01

    The primary methodology during the grant period has been the use of micro or meso-scale simulations to address specific questions concerning magnetospheric processes related to the aurora and substorm morphology. This approach, while useful in providing some answers, has its limitations. Many of the problems relating to the magnetosphere are inherently global and kinetic. Effort during the last year of the grant period has increasingly focused on development of a global-scale hybrid code to model the entire, coupled magnetosheath - magnetosphere - ionosphere system. In particular, numerical procedures for curvilinear coordinate generation and exactly conservative differencing schemes for hybrid codes in curvilinear coordinates have been developed. The new computer algorithms and the massively parallel computer architectures now make this global code a feasible proposition. Support provided by this project has played an important role in laying the groundwork for the eventual development or a global-scale code to model and forecast magnetospheric weather.

  16. The concept of Magnetically Driven Magnetosphere: storm/substorm dynamics and organization of the magnetotail

    NASA Astrophysics Data System (ADS)

    Pavlov, Nikolai

    A set of novel ideas and approaches have been found in the long-lasting attempts to better understand how the magnetosphere operates. It is proposed a certain vision of the substorm/storm scenario, of the tail structure with moderate magnetic By-component, and with intrinsic turbulence. Particle acceleration and the place of the tail's current sheet(s) in the proposed vision are discussed as well. For the reasoning of the proposal, several key ideas on the purely magnetospheric topics are included in the presentation.

  17. Spatial structure and temporal evolution of energetic particle injections in the inner magnetosphere during the 14 July 2013 substorm event

    SciTech Connect

    Gkioulidou, Matina; Ohtani, S.; Mitchell, D. G.; Ukhorskiy, A. Y.; Reeves, G. D.; Turner, D. L.; Gjerloev, J. W.; Nosé, M.; Koga, K.; Rodriguez, J. V.; Lanzerotti, L. J.

    2015-03-20

    Recent results by the Van Allen Probes mission showed that the occurrence of energetic ion injections inside geosynchronous orbit could be very frequent throughout the main phase of a geomagnetic storm. Understanding, therefore, the formation and evolution of energetic particle injections is critical in order to quantify their effect in the inner magnetosphere. We present a case study of a substorm event that occurred during a weak storm (Dst ~ –40 nT) on 14 July 2013. Van Allen Probe B, inside geosynchronous orbit, observed two energetic proton injections within 10 min, with different dipolarization signatures and duration. The first one is a dispersionless, short-timescale injection pulse accompanied by a sharp dipolarization signature, while the second one is a dispersed, longer-timescale injection pulse accompanied by a gradual dipolarization signature. We combined ground magnetometer data from various stations and in situ particle and magnetic field data from multiple satellites in the inner magnetosphere and near-Earth plasma sheet to determine the spatial extent of these injections, their temporal evolution, and their effects in the inner magnetosphere. Our results indicate that there are different spatial and temporal scales at which injections can occur in the inner magnetosphere and depict the necessity of multipoint observations of both particle and magnetic field data in order to determine these scales.

  18. Spatial structure and temporal evolution of energetic particle injections in the inner magnetosphere during the 14 July 2013 substorm event

    DOE PAGES

    Gkioulidou, Matina; Ohtani, S.; Mitchell, D. G.; ...

    2015-03-20

    Recent results by the Van Allen Probes mission showed that the occurrence of energetic ion injections inside geosynchronous orbit could be very frequent throughout the main phase of a geomagnetic storm. Understanding, therefore, the formation and evolution of energetic particle injections is critical in order to quantify their effect in the inner magnetosphere. We present a case study of a substorm event that occurred during a weak storm (Dst ~ –40 nT) on 14 July 2013. Van Allen Probe B, inside geosynchronous orbit, observed two energetic proton injections within 10 min, with different dipolarization signatures and duration. The first onemore » is a dispersionless, short-timescale injection pulse accompanied by a sharp dipolarization signature, while the second one is a dispersed, longer-timescale injection pulse accompanied by a gradual dipolarization signature. We combined ground magnetometer data from various stations and in situ particle and magnetic field data from multiple satellites in the inner magnetosphere and near-Earth plasma sheet to determine the spatial extent of these injections, their temporal evolution, and their effects in the inner magnetosphere. Our results indicate that there are different spatial and temporal scales at which injections can occur in the inner magnetosphere and depict the necessity of multipoint observations of both particle and magnetic field data in order to determine these scales.« less

  19. Computer simulation of a geomagnetic substorm

    NASA Technical Reports Server (NTRS)

    Lyon, J. G.; Brecht, S. H.; Huba, J. D.; Fedder, J. A.; Palmadesso, P. J.

    1981-01-01

    A global two-dimensional simulation of a substormlike process occurring in earth's magnetosphere is presented. The results are consistent with an empirical substorm model - the neutral-line model. Specifically, the introduction of a southward interplanetary magnetic field forms an open magnetosphere. Subsequently, a substorm neutral line forms at about 15 earth radii or closer in the magnetotail, and plasma sheet thinning and plasma acceleration occur. Eventually the substorm neutral line moves tailward toward its presubstorm position.

  20. Computer simulation of a geomagnetic substorm

    NASA Technical Reports Server (NTRS)

    Lyon, J. G.; Brecht, S. H.; Huba, J. D.; Fedder, J. A.; Palmadesso, P. J.

    1981-01-01

    A global two-dimensional simulation of a substormlike process occurring in earth's magnetosphere is presented. The results are consistent with an empirical substorm model - the neutral-line model. Specifically, the introduction of a southward interplanetary magnetic field forms an open magnetosphere. Subsequently, a substorm neutral line forms at about 15 earth radii or closer in the magnetotail, and plasma sheet thinning and plasma acceleration occur. Eventually the substorm neutral line moves tailward toward its presubstorm position.

  1. Electromagnetic and electrostatic emissions at the cusp-magnetosphere interface during substorms

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Fairfield, D. H.; Wu, C. S.

    1979-01-01

    Strongly peaked electrostatic emissions near 10.0 kHz and electromagnetic emissions near 0.56 kHz have been observed by the VLF wave detector on board Imp 6 on crossings from the earth's magnetosphere into the polar cusp during the occurrence of large magnetospheric substorms. The electrostatic emissions were observed to be closely confined to the cusp-magnetosphere interface. The electromagnetic emissions were of somewhat broader spatial extent and were seen on higher-latitude field lines within the cusp. Using these plasma wave observations and additional information provided by plasma, magnetometer and particle measurements made simultaneously on Imp 6, theories are constructed to explain each of the two classes of emission. The electromagnetic waves are modeled as whistlers, and the electrostatic waves as electron-cyclotron harmonics. The resulting growth rates predict power spectra similar to those observed for both emission classes. The electrostatic waves may play a significant role via enhanced diffusion in the relaxation of the sharp substorm time cusp-magnetosphere boundary to a more diffuse quiet time boundary.

  2. Electromagnetic and electrostatic emissions at the cusp-magnetosphere interface during substorms

    NASA Technical Reports Server (NTRS)

    Curtis, S. A.; Fairfield, D. H.; Wu, C. S.

    1979-01-01

    Strongly peaked electrostatic emissions near 10.0 kHz and electromagnetic emissions near 0.56 kHz have been observed by the VLF wave detector on board Imp 6 on crossings from the earth's magnetosphere into the polar cusp during the occurrence of large magnetospheric substorms. The electrostatic emissions were observed to be closely confined to the cusp-magnetosphere interface. The electromagnetic emissions were of somewhat broader spatial extent and were seen on higher-latitude field lines within the cusp. Using these plasma wave observations and additional information provided by plasma, magnetometer and particle measurements made simultaneously on Imp 6, theories are constructed to explain each of the two classes of emission. The electromagnetic waves are modeled as whistlers, and the electrostatic waves as electron-cyclotron harmonics. The resulting growth rates predict power spectra similar to those observed for both emission classes. The electrostatic waves may play a significant role via enhanced diffusion in the relaxation of the sharp substorm time cusp-magnetosphere boundary to a more diffuse quiet time boundary.

  3. Modeling substorm dynamics of the magnetosphere: from self-organization and self-organized criticality to nonequilibrium phase transitions.

    PubMed

    Sitnov, M I; Sharma, A S; Papadopoulos, K; Vassiliadis, D

    2002-01-01

    Earth's magnetosphere during substorms exhibits a number of characteristic features such as the signatures of low effective dimension, hysteresis, and power-law spectra of fluctuations on different scales. The largest substorm phenomena are in reasonable agreement with low-dimensional magnetospheric models and in particular those of inverse bifurcation. However, deviations from the low-dimensional picture are also quite considerable, making the nonequilibrium phase transition more appropriate as a dynamical analog of the substorm activity. On the other hand, the multiscale magnetospheric dynamics cannot be limited to the features of self-organized criticality (SOC), which is based on a class of mathematical analogs of sandpiles. Like real sandpiles, during substorms the magnetosphere demonstrates features, that are distinct from SOC and are closer to those of conventional phase transitions. While the multiscale substorm activity resembles second-order phase transitions, the largest substorm avalanches are shown to reveal the features of first-order nonequilibrium transitions including hysteresis phenomena and a global structure of the type of a temperature-pressure-density diagram. Moreover, this diagram allows one to find a critical exponent, that reflects the multiscale aspect of the substorm activity, different from the power-law frequency and scale spectra of autonomous systems, although quite consistent with second-order phase transitions. In contrast to SOC exponents, this exponent relates input and output parameters of the magnetosphere. Using an analogy to the dynamical Ising model in the mean-field approximation, we show the connection between the data-derived exponent of nonequilibrium transitions in the magnetosphere and the standard critical exponent beta of equilibrium second-order phase transitions.

  4. Energetic Electron Populations in the Magnetosphere During Geomagnetic Storms and Substorms

    NASA Technical Reports Server (NTRS)

    McKenzie, David L.; Anderson, Phillip C.

    2002-01-01

    This report summarizes the scientific work performed by the Aerospace Corporation under NASA Grant NAG5-10278, 'Energetic Electron Populations in the Magnetosphere during Geomagnetic Storms and Subsisting.' The period of performance for the Grant was March 1, 2001 to February 28, 2002. The following is a summary of the Statement of Work for this Grant. Use data from the PIXIE instrument on the Polar spacecraft from September 1998 onward to derive the statistical relationship between particle precipitation patterns and various geomagnetic activity indices. We are particularly interested in the occurrence of substorms during storm main phase and the efficacy of storms and substorms in injecting ring-current particles. We will compare stormtime simulations of the diffuse aurora using the models of Chen and Schulz with stormtime PIXIE measurements.

  5. On the relative importance of magnetospheric and ionospheric processes during substorm onset and expansion: A case study

    NASA Technical Reports Server (NTRS)

    Lopez, Ramon E.

    1992-01-01

    The question of whether substorm onset is triggered in the magnetotail or the ionosphere is presented. The possible influence of the ionosphere in the subsequent development of a substorm is discussed. Theoretical considerations involved are reviewed and a case study to address this question is examined. The evidence indicates that magnetotail processes initiate the sequence of events called a substorm, while the ionosphere appears to play a critical role in the subsequent evolution of the substorm expansion phase. However, the necessary observations, in particular high time resolution coordinated observations in the ionosphere and magnetotail are relatively rare. Continued examination of existing ground and space based data sets, in particular underutilized observations such as the Scatha data, may provide a more solid foundation for clarifying this issue and determining the relative importance of magnetospheric and ionospheric processes during substorms.

  6. On the relative importance of magnetospheric and ionospheric processes during substorm onset and expansion: A case study

    NASA Technical Reports Server (NTRS)

    Lopez, Ramon E.

    1992-01-01

    The question of whether substorm onset is triggered in the magnetotail or the ionosphere is presented. The possible influence of the ionosphere in the subsequent development of a substorm is discussed. Theoretical considerations involved are reviewed and a case study to address this question is examined. The evidence indicates that magnetotail processes initiate the sequence of events called a substorm, while the ionosphere appears to play a critical role in the subsequent evolution of the substorm expansion phase. However, the necessary observations, in particular high time resolution coordinated observations in the ionosphere and magnetotail are relatively rare. Continued examination of existing ground and space based data sets, in particular underutilized observations such as the Scatha data, may provide a more solid foundation for clarifying this issue and determining the relative importance of magnetospheric and ionospheric processes during substorms.

  7. A Telescopic and Microscopic Examination of Acceleration in the June 2015 Geomagnetic Storm: Magnetospheric Multiscale and Van Allen Probes Study of Substorm Particle Injection

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Jaynes, A. N.; Turner, D. L.; Nakamura, R.; Schmid, D.; Mauk, B. H.; Cohen, I. J.; Fennell, J. F.; Blake, J. B.; Strangeway, R. J.; hide

    2016-01-01

    An active storm period in June 2015 showed that particle injection events seen sequentially by the four (MagnetosphericMultiscale) MMS spacecraft subsequently fed the enhancement of the outer radiation belt observed by Van Allen Probes mission sensors. Several episodes of significant southward interplanetary magnetic field along with a period of high solar wind speed (Vsw 500kms) on 22 June occurred following strong interplanetary shock wave impacts on the magnetosphere. Key events on 22 June 2015 show that the magnetosphere progressed through a sequence of energy-loading and stress-developing states until the entire system suddenly reconfigured at 19:32 UT. Energetic electrons, plasma, and magnetic fields measured by the four MMS spacecraft revealed clear dipolarization front characteristics. It was seen that magnetospheric substorm activity provided a seed electron population as observed by MMS particle sensors as multiple injections and related enhancements in electron flux.

  8. A telescopic and microscopic examination of acceleration in the June 2015 geomagnetic storm: Magnetospheric Multiscale and Van Allen Probes study of substorm particle injection

    NASA Astrophysics Data System (ADS)

    Baker, D. N.; Jaynes, A. N.; Turner, D. L.; Nakamura, R.; Schmid, D.; Mauk, B. H.; Cohen, I. J.; Fennell, J. F.; Blake, J. B.; Strangeway, R. J.; Russell, C. T.; Torbert, R. B.; Dorelli, J. C.; Gershman, D. J.; Giles, B. L.; Burch, J. L.

    2016-06-01

    An active storm period in June 2015 showed that particle injection events seen sequentially by the four (Magnetospheric Multiscale) MMS spacecraft subsequently fed the enhancement of the outer radiation belt observed by Van Allen Probes mission sensors. Several episodes of significant southward interplanetary magnetic field along with a period of high solar wind speed (Vsw ≳ 500 km/s) on 22 June occurred following strong interplanetary shock wave impacts on the magnetosphere. Key events on 22 June 2015 show that the magnetosphere progressed through a sequence of energy-loading and stress-developing states until the entire system suddenly reconfigured at 19:32 UT. Energetic electrons, plasma, and magnetic fields measured by the four MMS spacecraft revealed clear dipolarization front characteristics. It was seen that magnetospheric substorm activity provided a "seed" electron population as observed by MMS particle sensors as multiple injections and related enhancements in electron flux.

  9. Rapid enhancement of energetic oxygen ions in the inner magnetosphere during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.

    2014-12-01

    Satellite observations show that energetic (>100 keV) O+ ions are rapidly increased in the inner magnetosphere during substorms. The ultimate source of O+ ions is the Earth's ionosphere, so that O+ ions must be accelerated from ~eV to 100s keV somewhere in the magnetosphere. A fundamental question still arise regarding why O+ ions are accelerated and transported to the inner magnetosphere. We simulated substorms under two different solar wind conditions by using the global MHD simulation developed by Tanaka et al. (2010, JGR). The solar wind speed is set to be 372 km/s for Case I, and 500 km/s for Case II. In both cases, the MHD simulation result shows that the dawn to dusk electric field is enhanced in the night side tail region at >7 Re just after the substorm onset. In particular, the electric field in the inner region (~7 Re) is highly enhanced by the tension force because of relatively strong magnetic field together with curved field lines. The strongest electric field takes place near the region where the plasma pressure is high. We performed test particle simulation under the electric and magnetic fields for Cases I and II. O+ ions are released from two planes located at ±2 Re in the Z direction in the tail region. O+ ions released at the two planes represent outflowing stream of O+ ions escaping from the Earth. The distribution function at the planes is assumed to be drifting Kappa distribution with temperature of 10 eV, the density of 105 m-3, and the parallel velocity given by the MHD simulation. In total, around a billion of particles are traced. Each test particle carries the real number of particles in accordance with the Liouville theorem. After tracing particles, we reconstructed 6-dimensional phase space density of O+ ions. We obtained the following results. (1) Just after substorm onset, the differential flux of O+ ions is almost simultaneously enhanced in the region where the electric field is strong. (2) The kinetic energy increases rapidly to

  10. Plasma Entry from Tail into the Dipolar Magnetosphere During Substorms

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    Plasma entering the dipolar magnetosphere from the tail has to overcome the obstacle presented by the conductivity enhancements caused by the poleward arc(s). While the arcs move poleward, the plasma proceeds equatorward as testified by the existence of a westward electric field. The arcs break into smaller-scale structures and loops with a tendency of eastward growth and expansion, although the basic driving force is directed earthward/equatorward. The likely reason is that the arc-related conductivity enhancements act as flow barriers and convert normal into shear stresses. The energy derived from the release of the shear stresses and dissipated in the arcs lowers the entropy content of the flux tubes and enables their earthward progression. In addition, poleward jumps of the breakup arcs are quite common. They result from refreshments of the generator plasma by the sequential arrival of flow bursts from the near-Earth neutral line. Once inside the oval, the plasma continues to move equatorward as manifested through north-south aligned auroral forms. Owing to the existence of an inner border of the oval, marked by the Region 2 currents, all flows are eventually diverted sunward.

  11. Substorms on Mercury?

    NASA Technical Reports Server (NTRS)

    Siscoe, G. L.; Ness, N. F.; Yeates, C. M.

    1974-01-01

    Qualitative similarities between some of the variations in the Mercury encounter data and variations in the corresponding regions of the earth's magnetosphere during substorms are pointed out. The Mariner 10 data on Mercury show a strong interaction between the solar wind and the plant similar to a scaled down version of that for the earth's magnetosphere. Some of the features observed in the night side Mercury magnetosphere suggest time dependent processes occurring there.

  12. The substorm loading-unloading cycle as reproduced by community-available global MHD magnetospheric models

    NASA Astrophysics Data System (ADS)

    Gordeev, Evgeny; Sergeev, Victor; Tsyganenko, Nikolay; Kuznetsova, Maria; Rastaetter, Lutz; Raeder, Joachim; Toth, Gabor; Lyon, John; Merkin, Vyacheslav; Wiltberger, Michael

    2017-04-01

    In this study we investigate how well the three community-available global MHD models, supported by the Community Coordinated Modeling Center (CCMC NASA), reproduce the global magnetospheric dynamics, including the loading-unloading substorm cycle. We found that in terms of global magnetic flux transport CCMC models display systematically different response to idealized 2-hour north then 2-hour south IMF Bz variation. The LFM model shows a depressed return convection in the tail plasma sheet and high rate of magnetic flux loading into the lobes during the growth phase, as well as enhanced return convection and high unloading rate during the expansion phase, with the amount of loaded/unloaded magnetotail flux and the growth phase duration being the closest to their observed empirical values during isolated substorms. BATSRUS and Open GGCM models exhibit drastically different behavior. In the BATS-R-US model the plasma sheet convection shows a smooth transition to the steady convection regime after the IMF southward turning. In the Open GGCM a weak plasma sheet convection has comparable intensities during both the growth phase and the following slow unloading phase. Our study shows that different CCMC models under the same solar wind conditions (north to south IMF variation) produce essentially different solutions in terms of global magnetospheric convection.

  13. Combining magnetospheric and ionospheric perspectives on the substorm current wedge modeling and dynamics.

    NASA Astrophysics Data System (ADS)

    Sergeev, Viktor

    Unprecedent spacecraft and instrumental coverage, isolated nature and distinct step-like development of the studied event on March 17, 2010 allowed us to investigate and demonstrate close spatio-temportal relationship of the substorm current wedge development with many other essential signatures of substorm activity in the magnetotail, including tailward flux transport in the more distant tail, flow bursts and disruptions of the thin current sheet in the near tail, and the dipolarizations and particle injections at geosynchronous orbit. This case study provides a clear illustration of sectorial organization of the activity in the magnetotail, with activity being confined to azimuthally localized sectors and expanding in step-like way to the new sectors of the magnetotail, presumably reflecting the step-like cross-tail evolution of the reconnection process. We confirm that ground SCW diagnostics allows to reconstruct the azimuthal spatio-temporal substorm development pattern with accuracy better than 1h MLT. Thanks to good azimuthal coverage of four GOES and three THEMIS spacecraft we evaluated the intensities of total SCW R1- and R2-like current loops (using SCW2L model) from combined magetospheric and ground midlatitude magnetic observations and compare it to the field-aligned current estimates provided by AMPERE project. As one more test of SCW2L model we predicted the amplitude of the poleward shift of the ionospheric footpoints due to addition of so-obtained SCW2L currents and found a reasonable agreement with observed poleward expansion of polar auroras and westward electrojet. Finally we run the adapted magnetospheric model and show that previous versions ofadaptive models can not substitite SCW2L to correctly predict the magnetic configuration changes during substorms, which require future efforts.

  14. Electric fields, electron precipitation, and VLF radiation during a simultaneous magnetospheric substorm and atmospheric thunderstorm

    SciTech Connect

    Bering, E.A.; Rosenberg, T.J.; Benbrook, J.R.; Detrick, D.; Matthews, D.L.; Rycroft, M.J.; Saunders, M.A.; Sheldon, W.R.

    1980-01-01

    A balloon payload instrumented with a double-probe electric field detector and an X ray scintillation counter was launched from Roberval, Quebec, Canada (L=4.1) at 0828 UT (0328 LT) on July 9, 1975. A magnetospheric substorm was observed locally between 0815 and 1100 UT, which produced a maximum ..delta..B of approx.500 nT at approx.0930 UT. A single-cell atmospheric thunderstorm developed northeast of Roberval beginning around 0925 UT which was most intense from approx.1000 to 1035 UT. Detailed study of the electrical properties of the thunderstorm, the X ray precipitation data, and VLF spheric data leads to three conclusions. First, the electrical coupling from the thunderstorm to the magnetosphere increases with frequency from dc to the VLF; for the observed storm the amplitude at the ionosphere of thunderstorm produced electric fields was not significant at frequencies below 0.1 Hz. Second, the atmospheric conductivity above the thunderstorm was observed to be about one-half the fair weather value prior to 1000 UT; decreased to about one-quarter the fair weather value at about 1000 UT; and remained depressed after the end of the thunderstorm. This result was contrary to that expected on the basis of previous work and is one which merits considerably more investigation. Third, the data show a high probability that half-hop whistlers initiated by sferics from the thunderstorm triggered energetic electron precipitation from the magnetosphere.

  15. Space Borne and Ground-Based Observations of Transient Processes Occurring Around Substorm Onset

    NASA Technical Reports Server (NTRS)

    Kepko, L.; Spanswick, E.; Angelopoulos, V.; Donovan, E.

    2010-01-01

    The combined THEMIS five spacecraft in-situ and ground magnetic and visible camera arrays have advanced considerably our understanding of the causal relationship between midtail plasma flows, transient ionospheric features, and ground magnetic signatures. In particular recent work has shown a connection between equatorward moving visible ionospheric transients and substorm onset, in both white-light and 6300 nm emissions. These observations, together with THEMIS in-situ measurements of bulk flows, provides strict constraints on the sequence of events leading to substorm auroral onset.We first provide a brief summary of these observations, highlighting in particular areas where the two observations differ, and suggest reasons for the differences. Next, by combining the observed correlation of flow and Pi2 waveform with a unified model of global Pi2 generation and substorm current wedge initiation we present a self-consistent description of the dynamical processes and communicative pathways that occur just prior to and during substorm expansion onset.

  16. Temporal and Spatial Evolution of Energetic Ion Injections in the Inner Magnetosphere: Multi-Point Observations of a Substorm Event.

    NASA Astrophysics Data System (ADS)

    Gkioulidou, M.; Ohtani, S.; Mitchell, D. G.; Reeves, G. D.; Ukhorskiy, A. Y.; Turner, D. L.; Gjerloev, J. W.; Nose, M.; Koga, K.; Rodriguez, J. V.; Lanzerotti, L. J.

    2014-12-01

    Plasma transport and energization of ions in the magnetotail has been shown to largely occur in the form of injections of hot plasma, localized in MLT, associated with bursty bulk flows and sharp dipolarizations of the magnetic field. However, the relationship of these transient tail phenomena to energetic particle injections into the inner magnetosphere is not well understood. Recent results by the RBSPICE instrument of the Van Allen Probes mission showed that the occurrence of energetic ion injections inside geosynchronous orbit can be very frequent throughout the main phase of a geomagnetic storm, and indicated that the contribution of such injections to the ring current buildup could be substantial. Understanding the formation and evolution of energetic ion injections in the inner magnetosphere and their relationship to transient phenomena in the tail is, therefore, of great importance. In order to differentiate between temporal and spatial variations, it is essential to investigate injections via multi-point observations. We study a substorm event that occurred during a small storm (Dst ~-40 nT), where two injections of energetic ions (50 - 300 keV), 10 minutes apart, were observed by RBSPICE instrument inside geosynchronous orbit, and six LANL and two GOES spacecraft at geosynchronous orbit. Geosynchronous spacecraft ETS-8, at a similar MLT with Van Allen Probe B, also observed the dipolarization signatures associated with these two injections. At the same time, two THEMIS spacecraft were monitoring the night-side magnetosphere at ~ 10 RE. Using ground-based magnetometer data, we are able to identify the eastward and westward edges of the current wedge associated with each one of these injections. The two injections, as observed in the inner magnetosphere, exhibit distinct differences in their dipolarization signatures as well as their duration. With all the above data at hand, we investigate the inward propagation of the injections into the inner

  17. A Mechanism for the Loading-Unloading Substorm Cycle Missing in MHD Global Magnetospheric Simulation Models

    NASA Technical Reports Server (NTRS)

    Klimas, A. J.; Uritsky, V.; Vassiliadis, D.; Baker, D. N.

    2005-01-01

    Loading and consequent unloading of magnetic flux is an essential element of the substorm cycle in Earth's magnetotail. We are unaware of an available global MHD magnetospheric simulation model that includes a loading- unloading cycle in its behavior. Given the central role that MHD models presently play in the development of our understanding of magnetospheric dynamics, and given the present plans for the central role that these models will play in ongoing space weather prediction programs, it is clear that this failure must be corrected. A 2-dimensional numerical driven current-sheet model has been developed that incorporates an idealized current- driven instability with a resistive MHD system. Under steady loading, the model exhibits a global loading- unloading cycle. The specific mechanism for producing the loading-unloading cycle will be discussed. It will be shown that scale-free avalanching of electromagnetic energy through the model, from loading to unloading, is carried by repetitive bursts of localized reconnection. Each burst leads, somewhat later, to a field configuration that is capable of exciting a reconnection burst again. This process repeats itself in an intermittent manner while the total field energy in the system falls. At the end of an unloading interval, the total field energy is reduced to well below that necessary to initiate the next unloading event and, thus, a loading-unloading cycle results. It will be shown that, in this model, it is the topology of bursty localized reconnection that is responsible for the appearance of the loading-unloading cycle.

  18. Substorm occurrence rates, substorm recurrence times, and solar wind structure

    NASA Astrophysics Data System (ADS)

    Borovsky, Joseph E.; Yakymenko, Kateryna

    2017-03-01

    Two collections of substorms are created: 28,464 substorms identified with jumps in the SuperMAG AL index in the years 1979-2015 and 16,025 substorms identified with electron injections into geosynchronous orbit in the years 1989-2007. Substorm occurrence rates and substorm recurrence-time distributions are examined as functions of the phase of the solar cycle, the season of the year, the Russell-McPherron favorability, the type of solar wind plasma at Earth, the geomagnetic-activity level, and as functions of various solar and solar wind properties. Three populations of substorm occurrences are seen: (1) quasiperiodically occurring substorms with recurrence times (waiting times) of 2-4 h, (2) randomly occurring substorms with recurrence times of about 6-15 h, and (3) long intervals wherein no substorms occur. A working model is suggested wherein (1) the period of periodic substorms is set by the magnetosphere with variations in the actual recurrence times caused by the need for a solar wind driving interval to occur, (2) the mesoscale structure of the solar wind magnetic field triggers the occurrence of the random substorms, and (3) the large-scale structure of the solar wind plasma is responsible for the long intervals wherein no substorms occur. Statistically, the recurrence period of periodically occurring substorms is slightly shorter when the ram pressure of the solar wind is high, when the magnetic field strength of the solar wind is strong, when the Mach number of the solar wind is low, and when the polar-cap potential saturation parameter is high.

  19. On the cause of thin current sheets in the near-Earth magnetotail and their possible significance for magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Schindler, K.; Birn, J.

    1993-01-01

    The formation of thin current sheets in the near-Earth magnetotail during substorm growth phases is addressed in terms of a simple model. An appropriate part of the unperturbed magnetotail is represented by a plane sheet model. Perturbations are applied to the upper and to the left boundaries, representing the magnetopause and the near-Earth tail boundary, where the perturbation at the latter models the interaction between the tail and the inner magnetosphere. Treating the perturbation as ideal (dissipation-free), we found that singular current sheets develop in the midplane of the tail. The analytical results are explored numerically. Using realistic dimensions of the domain considered, the influence of the earthward boundary on current sheet formation dominates. It is argued that current sheet formation of this type plays an important role in the processes associated with the onset of magnetospheric substorms.

  20. Magnetospheric substorm: Loss of the magnetoplasma equilibrium as a nonlinear dynamical bifurcation

    NASA Astrophysics Data System (ADS)

    Kropotkin, A. P.

    2012-04-01

    The fast onset of a substorm—a substorm "explosion"—is usually associated with the moment of stability loss of the magnetoplasma equilibrium in the geomagnetic tail. The origination of such a process either from the near-Earth part of the plasma sheet or from its remote part, which is highly stretched into the tail, is now being studied theoretically and verified experimentally (at the present time, in the THEMIS project). In the first case, the resulting disturbance must have the form of a ballooning mode; in the second case, of tearing perturbation. However, in both cases, this stability loss, i.e., a quick breakdown in the balance, replacing the slow quasi-static evolution of configuration, can only occur as a nonlinear process. Taking into account the specific properties of the configuration and possible disturbances in it, we indicate why such a process cannot be the previously proposed "substorm detonation." It is shown that a suitable mathematical model is a nonlinear dynamical bifurcation occurring on a small time scale, with a delay relative to the moment of passing the marginally stable state.

  1. Near-earth substorm onset: A coordinated study

    SciTech Connect

    Persson, M.A.L.; Opgenoorth, H.J.; Eriksson, A.I.; Dovner, P.O.; Pulkkinen, T.I.; Reeves, G.D.; Belian, R.D.; Andre, M.; Blomberg, L.G.; Erlandson, R.E.

    1994-08-15

    The authors present simultaneous satellite and ground-based measurements of a substorm. Throughout the initial substorm expansion, southward drifting arcs are observed poleward of the expanding substorm aurora, indicating two independent systems of particle precipitation. Freja passes the brightening onset arc in the topside ionosphere near the moment of the substorm onset, observing an Alfven wave, field aligned current and oxygen ion outflow. The substorm onset occurs at low magnetospheric L-shells, near the poleward edge of the region of trapped particles. The location and time for the substorm injection are confirmed by geostationary spacecraft together with magnetometers, all-sky cameras and radar on the ground. The authors believe that the substorm onset may be triggered by modification of the oxygen content of the inner magnetosphere during the growth-phase caused by ionospheric ion outflow. 15 refs., 7 figs.

  2. The problem of the acceleration of electrons of the outer radiation belt and magnetospheric substorms

    NASA Astrophysics Data System (ADS)

    Antonova, E. E.; Stepanova, M. V.

    2015-09-01

    Predicting of the location of the maximum in high-energy electron fluxes filling a new radiation belt is an endeavor being carried out by physicists studying the magnetosphere. We analyzed the data from the Defense Meteorological Satellite Program (DMSP) satellites and ground-based magnetometers obtained during geomagnetic storm on 8-9 October 2012. The minimum value of the disturbance storm time (Dst) was -111 nT, and the maximum in high-energy electron fluxes that appeared during the recovery phase was observed at L = 4 Re. At the same time, we analyzed the motion of the auroral oval toward lower latitudes and related substorm activity using the data of the low-orbiting DMSP satellites and the IMAGE magnetic meridian network. It was found from the DMSP satellites' measurements that the maximum of the energy density of precipitating ions, the maximum of the plasma pressure, and the most equatorial part of the westward auroral electrojet are all located at the 60° geomagnetic latitude. This value corresponds to L = 4 Re, i.e., it coincides with the location of the maximum in high-energy electron fluxes. This L-value also agrees with the predictions of the Tverskaya relation between the minimum in Dst variation and the location of the maximum of the energetic electron fluxes, filling a new radiation belt. The obtained results show that the location of this maximum could be predicted solely from the data of the auroral particle precipitations and/or ground-based magnetic observations.

  3. Multiple-satellite studies of magnetospheric substorms: Plasma sheet recovery and the poleward leap of auroral-zone activity

    NASA Technical Reports Server (NTRS)

    Pytte, T.; Mcpherron, R. L.; Kivelson, M. G.; West, H. I., Jr.; Hones, E. W., Jr.

    1977-01-01

    Particle observations from pairs of satellites (Ogo 5, Vela 4A and 5B, Imp 3) during the recovery of plasma sheet thickness late in substorms were examined. Six of the nine events occurred within about 5 min in locations near the estimated position of the neutral sheet, but over wide ranges of east-west and radial separations. The time of occurrence and spatial extent of the recovery were related to the onset (defined by ground Pi 2 pulsations) and approximate location (estimated from ground mid-latitude magnetic signatures) of substorm expansions. It was found that the plasma sheet recovery occurred 10 - 30 min after the last in a series of Pi bursts, which were interpreted to indicate that the recovery was not due directly to a late, high latitude substorm expansion. The recovery was also observed to occur after the substorm current wedge had moved into the evening sector and to extend far to the east of the center of the last preceding substorm expansion.

  4. Dynamics of Thin Current Sheets and Their Disruption by Ballooning Instabilities: a Mechanism for Magnetospheric Substorms

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, A.

    1997-11-01

    During the growth phase, the magnetotail is prepared for the violent relaxation dynamics that occurs at substorm onset. Multi-satellite observations indicate the development of a thin current sheet and a rapid intensification of the cross-tail current density at near-Earth distances during a short interval (< 1 min) just before onset, after a period of sluggish growth ( ~ 0.5-1.5 hr). These observational features have been accounted for recently by analysis as well as high-resolution MHD simulation of the magnetotail, including the Earth's dipole field. In the slow growth and impulsive pre-onset phase, it is shown that a thin current sheet develops spanning Y-points that stretch from the mid-tail region ( ~ 30 R_E) to the near-Earth region ( ~ 10 R_E). The current sheet dynamics exhibits an impulsive enhancement in amplitude and the flows are dominantly earthward, consistent with observations. When the current sheet becomes sufficiently thin, finite ion-Larmor-radius terms such as electron pressure gradients and Hall currents must be included in the theory and are shown to have a striking effect on the dynamics in the impulsive growth phase. It is shown that the thin current sheet is unstable to ideal ballooning instabilities with rapid spatial variation in the dawn-dusk direction. Ionospheric boundary conditions can have a strong influence on the linear properties of the ballooning instability, especially at near-Earth distances. Once the linear mode is triggered, nonlinear studies indicate a tendency for near-explosive growth of the instability, suggesting its possible role as a mechanism for substorm onset.

  5. Solar and Interplanetary Causes of Extremely Intense Substorms During Superstorms

    NASA Astrophysics Data System (ADS)

    Tsurutani, Bruce; Hajra, Rajkumar; Echer, Ezequiel; Gjerloev, Jesper

    2016-04-01

    We have begun a study of particularly intense substorms that occur during superstorms. We will relate the solar cycle dependences of events, whether they are externally or internally triggered, and their relationship to other factors such as magnetospheric preconditioning. If time permits, we will explore the details of the events and whether they are similar to regular (Akasofu, 1964) substorms or not. These intense substorms are an important feature of space weather since they may be responsible for power outages.

  6. Modeling particle injections during magnetospheric substorm by a propagating earthward electromagnetic pulse.

    NASA Astrophysics Data System (ADS)

    Kalugin, G. A.; Kabin, K.; Donovan, E.; Spanswick, E.

    2016-12-01

    During substorm expansion phase the electrons and ions with energies of up to 100 keV appear in the near-Earth magnetotail. Often, this increase occurs simultaneously for a broad range of particle energies; such events are called dispersionless injections (DIs). Explanations of DIs usually relay on some form of an earthward propagating electromagnetic pulse, which is capable of effectively energizing an initial distribution of electrons and ions. Most of the previous models of such pulses were developed for the equatorial plane only. We propose a new model of an electromagnetic pulse which is two-dimensional in the meridional plane. Electric and magnetic fields in the pulse are calculated self-consistently and satisfy Maxwell's equations. We use realistic time-independent stretched magnetic field as the background. Our model has several adjustable parameters, such as the speed of the pulse propagation, its amplitude and spatial extent, which makes it versatile enough to investigate effects of the pulse characteristics on the particle energization. We present and discuss several examples of particle energization in our model and find that in some cases the energies of the seed electrons can increase by a factor of 10 or more. Two-dimensional nature of our model allows us to visualize the motion of the field lines in the meridional plane associated with the travelling electromagnetic pulse and to calculate the ionospheric footprints of the particle dynamics in the equatorial plane.

  7. A multi-instrumental case study of the substorm event occurring 2002-09-08

    NASA Astrophysics Data System (ADS)

    Palin, Laurianne; Ågren, Karin; zivkovic, Tatjana; Opgenoorth, Hermann; Fasckó, Gabor; Sergeev, Victor; Kubyshkina, Marina; Nikolaev, Alexander; Milan, Steve; Imber, Suzanne; Kauristie, Kirsti; Palmroth, Minna; van de Kamp, Max; Nakamura, Rumi; Boakes, Peter

    2014-05-01

    Multi-instrumental data mining and interpretation can be tricky. In this context, the ECLAT (European Cluster Assimilation Technology) project was created to « provide a novel and unique data base and tools for space scientists, by providing an upgrade of the European Space Agency's Cluster Active Archive (CAA). » How can this new tool help the space plasma physics community? Here we demonstrate the power of coordinated global and meso-scale ground-based data to put satellite data into the proper context. We re-analyse a well-isolated substorm with a strong growth phase, which starts right overhead the Scandinavian network of instruments. This event was previously studied in detail by Sergeev et al (2005), based on a THEMIS-like configuration near-midnight using a unique radial constellation of LANL (~6.6Re), Geotail and Polar (~9Re), and Cluster (~16Re). In this new study we add detailed IMAGE spacecraft and ground-based network data. Several magnetospheric models are specially adapted using solar wind conditions and in-situ observations. Simulation results are compared to the in-situ observations and discussed.

  8. Comment on "Tail reconnection triggering substorm onset".

    PubMed

    Lui, A T Y

    2009-06-12

    Angelopoulos et al. (Research Articles, 15 August 2008, p. 931) reported that magnetic reconnection in Earth's magnetotail triggered the onset of a magnetospheric substorm. We provide evidence that (i) near-Earth current disruption, occurring before the conventional tail reconnection signatures, triggered the onset; (ii) the observed auroral intensification and tail reconnection are not causally linked; and (iii) the onset they identified is a continuation of earlier substorm activities.

  9. PC index as a proxy of the solar wind energy that entered into the magnetosphere: 2. Relation to the interplanetary electric field E KL before substorm onset

    NASA Astrophysics Data System (ADS)

    Troshichev, OA; Sormakov, DA

    2015-10-01

    This paper (the second of a series) presents the results of statistical investigation of relationship between the interplanetary electric field E KL and the Polar Cap (PC) index in case of magnetic substorms (1998-2001), which have been analyzed in Troshichev et al. (J. Geophys. Res. Space Physics, 119, 2014). The PC index is directly related to the E KL field variations on interval preceding the substorm sudden onset (SO): correlation R > 0.5 is typical of more than 90 % of isolated substorms, 80 % of expanded substorms, and 99 % of events with coordinated E KL and PC jumps. The low or negative correlation observing in ~10 % of examined substorms suggests that the solar wind flow measured by the Advanced Composition Explorer (ACE) spacecraft in the Lagrange point L1 did not encounter the magnetosphere in these cases. Examination of the delay times Δ T in the response of PC index to E KL variations provides the following results: (1) delay times do not depend on separate solar wind parameters, such as solar wind speed V X and interplanetary magnetic field (IMF) B Z component, contrary to general conviction, (2) the Δ T value is best controlled by the E KL field growth rate (d E KL/dt), (3) the lower Δ T limit (5-7 min is attained under conditions of the higher E KL growth rate, and (4) the PC index provides the possibility to verify the solar wind flow transportation time from ACE position (where the solar wind speed is estimated) to magnetosphere. These results, in combination with data testifying that the substorm onsets are related to the PC precursors, demonstrate that the PC index is an adequate ground-based indicator of the solar wind energy incoming into the magnetosphere.

  10. Generation of large-amplitude electric field and subsequent enhancement of O+ ion flux in the inner magnetosphere during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.

    2015-06-01

    Energetic O+ ions are rapidly enhanced in the inner magnetosphere because of abrupt intensification of the dawn-to-dusk electric field and significantly contribute to the ring current during substorms. Here we examine the generation mechanism of the dawn-to-dusk electric field that accelerates the O+ ions and the spatial and temporal evolution of the differential flux of the O+ ions by using a test particle simulation in the electric and magnetic fields that are provided by a global magnetohydrodynamics (MHD) simulation. In the MHD simulation, strong dawn-to-dusk electric field appears in the near-Earth tail region by a joint action of the earthward tension force and pileup of magnetic flux near an onset of substorm expansion. The peak of the electric field is ~9-13 mV/m and is located ~1-2 RE earthward of the peak of the plasma bulk speed because of the pileup. O+ ions coming from the lobe are accelerated from ~eV to >100 keV in ~10 min. The reconstructed flux of the O+ ions shows that at ~7 RE near midnight, the flux has a peak near a few tens of keV and the flux below ~10 keV is small. This structure, called a "void" structure, is consistent with the Polar observation and can be regarded as a manifestation of the acceleration of unmagnetized ions perpendicular to the magnetic field. In the inner magnetosphere (at 6.0 RE), reconstructed energy-time spectrograms show the nose dispersion structure that is also consistent with satellite observations.

  11. Substorm aurorae and their connection to the inner magnetosphere. Technical report

    SciTech Connect

    Lopez, R.E.; Meng, C.I.; Spence, H.E.

    1994-04-15

    In this report the authors present evidence from the low-altitude DMSP F7 satellite that the poleward edge of auroral luminosity in the nightside auroral zone does not necessarily correspond to the boundary between plasma-filled flux tubes and flux tubes devoid of plasma. Assuming that the low-altitude boundary corresponds to the boundary between the lobe and the plasma sheet, this implies that the boundary between open and closed field lines may lie poleward of the most poleward auroral luminosity. Thus the assumption that the poleward boundary of auroral luminosity is a good indicator of the open-closed boundary may not always be correct. Furthermore, they show clear evidence that an auroral surge may also be located equatorward of the open-closed boundary. Therefore, tailward of the region of the plasma sheet to which the surge is connected there may exist undisturbed plasma sheet that has not yet been disconnected from the ionosphere. This means that substorm-associated reconnection does not necessarily begin to reconnect lobe field lines at the onset of a substorm. Moreover, available evidence strongly suggests that the arc that brightens at the onset of a substorm and that develops into a surge maps to the inner magnetotail, to that region at the inner edge of the plasma sheet where the magnetic field changes from a dipolar to a tail-like configuration. This would be consistent with recent studies that connect auroral breakup to the near-Earth (

  12. Crossover behavior of multiscale fluctuations in Big Data: Langevin model and substorm time-scales in Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Sharma, A. S.; Setty, V. A.

    2015-12-01

    Multiscale fluctuations in large and complex data are usually characterized by a power law with a scaling exponent but many systems require more than one exponent and thus exhibit crossover behavior. The scaling exponents, such as Hurst exponents, represent the nature of correlation in the system and the crossover shows the presence of more than one type of correlation. An accurate characterization of the crossover behavior is thus needed for a better understanding of the inherent correlations in the system, and is an important method of Big Data analysis. A multi-step process is developed for accurate computation of the crossover behavior. First the detrended fluctuation analysis is used to remove the trends in the data and the scaling exponents are computed. The crossover point is then computed by a Hyperbolic regression technique, with no prior assumptions. The time series data of the magnetic field variations during substorms in the Earth's magnetosphere is analyzed with these techniques and yields a crossover behavior with a time scale of ~4 hrs. A Langevin model derived from the data provides an excellent fit to the crossover in the scaling exponents and a good model of magnetospheric dynamics. The combination of fluctuation analysis and mathematical modeling thus yields a comprehensive approach in the analysis of Big Data.

  13. Relationship between the growth of the ring current and the interplanetary quantity. [solar wind energy-magnetospheric coupling parameter correlation with substorm AE index

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1979-01-01

    Akasofu (1979) has reported that the interplanetary parameter epsilon correlates reasonably well with the magnetospheric substorm index AE; in the first approximation, epsilon represents the solar wind coupled to the magnetosphere. The correlation between the interplanetary parameter, the auroral electrojet index and the ring current index is examined for three magnetic storms. It is shown that when the interplanetary parameter exceeds the amount that can be dissipated by the ionosphere in terms of the Joule heat production, the excess energy is absorbed by the ring current belt, producing an abnormal growth of the ring current index.

  14. Solar Wind-Magnetosphere Coupling During an Isolated Substorm Event: A Multispacecraft ISTP Study

    NASA Technical Reports Server (NTRS)

    Pulkkinen, T. I.; Baker, D. N.; Turner, N. E.; Singer, H. J.; Frank, L. A.; Sigwarth, J. B.; Scudder, J.; Anderson, R.; Kokubun, S.; Mukai, T.; Nakamura, R.; Blake, J. B.; Russell, C. T.; Kawano, H.; Mozer, F.; Slavin, J. A.

    1997-01-01

    Multispacecraft data from the upstream solar wind, polar cusp, and inner magnetotail are used to show that the polar ionosphere responds within a few minutes to a southward IMF turning, whereas the inner tail signatures are visible within ten min from the southward turning. Comparison of two subsequent substorm onsets, one during southward and the other during northward IMF, demonstrates the dependence of the expansion phase characteristics on the external driving conditions. Both onsets are shown to have initiated in the midtail, with signatures in the inner tail and auroral oval following a few minutes later.

  15. Hemispheric Asymmetries in Substorm Recovery Time Scales

    NASA Technical Reports Server (NTRS)

    Fillingim, M. O.; Chua, D H.; Germany, G. A.; Spann, James F.

    2009-01-01

    Previous statistical observations have shown that the recovery time scales of substorms occurring in the winter and near equinox (when the nighttime auroral zone was in darkness) are roughly twice as long as the recovery time scales for substorms occurring in the summer (when the nighttime auroral region was sunlit). This suggests that auroral substorms in the northern and southern hemispheres develop asymmetrically during solstice conditions with substorms lasting longer in the winter (dark) hemisphere than in the summer (sunlit) hemisphere. Additionally, this implies that more energy is deposited by electron precipitation in the winter hemisphere than in the summer one during substorms. This result, coupled with previous observations that have shown that auroral activity is more common when the ionosphere is in darkness and is suppressed when the ionosphere is in daylight, strongly suggests that the ionospheric conductivity plays an important role governing how magnetospheric energy is transferred to the ionosphere during substorms. Therefore, the ionosphere itself may dictate how much energy it will accept from the magnetosphere during substorms rather than this being an externally imposed quantity. Here, we extend our earlier work by statistically analyzing the recovery time scales for a large number of substorms observed in the conjugate hemispheres simultaneously by two orbiting global auroral imagers: Polar UVI and IMAGE FUV. Our current results are consistent with previous observations. The recovery time scales are observed to be longer in the winter (dark) hemisphere while the auroral activity has a shorter duration in the summer (sunlit) hemisphere. This leads to an asymmetric energy input from the magnetosphere to the ionosphere with more energy being deposited in the winter hemisphere than in the summer hemisphere.

  16. Hemispheric Asymmetries in Substorm Recovery Time Scales

    NASA Technical Reports Server (NTRS)

    Fillingim, M. O.; Chua, D H.; Germany, G. A.; Spann, James F.

    2009-01-01

    Previous statistical observations have shown that the recovery time scales of substorms occurring in the winter and near equinox (when the nighttime auroral zone was in darkness) are roughly twice as long as the recovery time scales for substorms occurring in the summer (when the nighttime auroral region was sunlit). This suggests that auroral substorms in the northern and southern hemispheres develop asymmetrically during solstice conditions with substorms lasting longer in the winter (dark) hemisphere than in the summer (sunlit) hemisphere. Additionally, this implies that more energy is deposited by electron precipitation in the winter hemisphere than in the summer one during substorms. This result, coupled with previous observations that have shown that auroral activity is more common when the ionosphere is in darkness and is suppressed when the ionosphere is in daylight, strongly suggests that the ionospheric conductivity plays an important role governing how magnetospheric energy is transferred to the ionosphere during substorms. Therefore, the ionosphere itself may dictate how much energy it will accept from the magnetosphere during substorms rather than this being an externally imposed quantity. Here, we extend our earlier work by statistically analyzing the recovery time scales for a large number of substorms observed in the conjugate hemispheres simultaneously by two orbiting global auroral imagers: Polar UVI and IMAGE FUV. Our current results are consistent with previous observations. The recovery time scales are observed to be longer in the winter (dark) hemisphere while the auroral activity has a shorter duration in the summer (sunlit) hemisphere. This leads to an asymmetric energy input from the magnetosphere to the ionosphere with more energy being deposited in the winter hemisphere than in the summer hemisphere.

  17. Energy limits of electron acceleration in the plasma sheet during substorms: A case study with the Magnetospheric Multiscale (MMS) mission

    DOE PAGES

    Turner, Drew Lawson; Fennell, J. F.; Blake, J. B.; ...

    2016-08-01

    Here, we present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASA's Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at ~7–9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially due to precipitation by strong parallel electrostatic wavefields or initial sources in the lobes. Electrons at energies higher than the thresholdmore » are accelerated cumulatively by a series of impulsive magnetic dipolarization events. This case demonstrates how the upper energy cutoff increases, in this case from ~130 keV to >500 keV, with each dipolarization/injection during sustained activity. We also present a simple model accounting for these energy limits that reveals that electron energization is dominated by betatron acceleration.« less

  18. Energy limits of electron acceleration in the plasma sheet during substorms: A case study with the Magnetospheric Multiscale (MMS) mission

    SciTech Connect

    Turner, Drew Lawson; Fennell, J. F.; Blake, J. B.; Clemmons, J. H.; Mauk, B. H.; Cohen, I. J.; Jaynes, A. N.; Craft, J. V.; Wilder, F. D.; Baker, D. N.; Reeves, Geoffrey D.; Gershman, D. J.; Avanov, L. A.; Dorelli, J. C.; Giles, B. L.; Pollock, C. J.; Schmid, D.; Nakamura, R.; Strangeway, R. J.; Russell, C. T.; Artemyev, A. V.; Runov, A.; Angelopoulos, V.; Spence, H. E.; Torbert, R. B.; Burch, J. L.

    2016-08-01

    Here, we present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASA's Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at ~7–9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially due to precipitation by strong parallel electrostatic wavefields or initial sources in the lobes. Electrons at energies higher than the threshold are accelerated cumulatively by a series of impulsive magnetic dipolarization events. This case demonstrates how the upper energy cutoff increases, in this case from ~130 keV to >500 keV, with each dipolarization/injection during sustained activity. We also present a simple model accounting for these energy limits that reveals that electron energization is dominated by betatron acceleration.

  19. Energy limits of electron acceleration in the plasma sheet during substorms: A case study with the Magnetospheric Multiscale (MMS) mission

    NASA Astrophysics Data System (ADS)

    Turner, D. L.; Fennell, J. F.; Blake, J. B.; Clemmons, J. H.; Mauk, B. H.; Cohen, I. J.; Jaynes, A. N.; Craft, J. V.; Wilder, F. D.; Baker, D. N.; Reeves, G. D.; Gershman, D. J.; Avanov, L. A.; Dorelli, J. C.; Giles, B. L.; Pollock, C. J.; Schmid, D.; Nakamura, R.; Strangeway, R. J.; Russell, C. T.; Artemyev, A. V.; Runov, A.; Angelopoulos, V.; Spence, H. E.; Torbert, R. B.; Burch, J. L.

    2016-08-01

    We present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASA's Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at 7-9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially due to precipitation by strong parallel electrostatic wavefields or initial sources in the lobes. Electrons at energies higher than the threshold are accelerated cumulatively by a series of impulsive magnetic dipolarization events. This case demonstrates how the upper energy cutoff increases, in this case from 130 keV to >500 keV, with each dipolarization/injection during sustained activity. We also present a simple model accounting for these energy limits that reveals that electron energization is dominated by betatron acceleration.

  20. Energy Limits of Electron Acceleration in the Plasma Sheet During Substorms: A Case Study with the Magnetospheric Multiscale (MMS) Mission

    NASA Technical Reports Server (NTRS)

    Turner, D. L.; Fennell, J. F.; Blake, J. B.; Clemmons, J. H.; Mauk, B. H.; Cohen, I. J.; Jaynes, A. N.; Craft, J. V.; Wilder, F. D.; Baker, D. N.; hide

    2016-01-01

    We present multipoint observations of earthward moving dipolarization fronts and energetic particle injections from NASAs Magnetospheric Multiscale mission with a focus on electron acceleration. From a case study during a substorm on 02 August 2015, we find that electrons are only accelerated over a finite energy range, from a lower energy threshold at approx. 7-9 keV up to an upper energy cutoff in the hundreds of keV range. At energies lower than the threshold energy, electron fluxes decrease, potentially due to precipitation by strong parallel electrostatic wavefields or initial sources in the lobes. Electrons at energies higher than the threshold are accelerated cumulatively by a series of impulsive magnetic dipolarization events. This case demonstrates how the upper energy cutoff increases, in this case from approx. 130 keV to >500 keV, with each depolarization/injection during sustained activity. We also present a simple model accounting for these energy limits that reveals that electron energization is dominated by betatron acceleration.

  1. Dynamics of thin current sheets and their disruption by ballooning instabilities: A mechanism for magnetospheric substorms

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, A.; Ma, Z. W.; Wang, Xiaogang

    1998-05-01

    Multipoint satellite observations indicate the development of thin current sheets and an impulsive intensification of the cross-tail current density in the growth phase at near-earth distances during a short interval (<1 min) just before onset, after a period of sluggish growth (˜0.5-1.5 h). These multiple time scales are accounted for by analysis and two-dimensional magnetohydrodynamic simulation of the magnetotail in the high-Lundquist number regime, including the earth's dipole field. In the slow growth phase, a thin current sheet develops spanning Y points that stretch from the midtail region (˜30RE) to the near-earth region (˜10RE). This is followed by an impulsive enhancement in the current sheet amplitude due to flux pileup, consistent with observations. The stretched magnetotail with an embedded thin current sheet is found to be unstable to an ideal compressible ballooning instability with rapid spatial variation in the dawn-dusk direction. The linear instability is demonstrated by numerical solutions of the ideal ballooning eigenmode equation for a sequence of two-dimensional magnetotail configurations containing a thin current sheet, realized during the impulsive growth phase. Line-tied boundary conditions are imposed at the ionosphere, and shown to have a strong influence on the linear stability of ballooning modes at near-earth distances. It is suggested that the ideal ballooning instability provides a possible mechanism for disrupting the cross-tail current at substorm onset.

  2. The solar wind and magnetospheric dynamics

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1974-01-01

    The dynamic processes involved in the interaction between the solar wind and the earth's magnetosphere are reviewed. The evolution of models of the magnetosphere is first surveyed. The existence of the auroral substorm and the cyclical polar magnetic substorm is evidence that the magnetosphere is a dynamic system. The dynamic changes occurring in the magnetosphere, including erosion of the magnetopause, changes in the size of the polar cap, variations in the flaring angle of the tail, neutral point formation, plasma sheet motions, and the inward collapse of the midnight magnetosphere, are discussed. The cyclical variations of geomagnetic activity are explained in terms of the control of the solar wind-magnetosphere interaction by the north-south component of the interplanetary magnetic field. Present phenomenological models allow prediction of geomagnetic activity from interplanetary measurements, but modeling of detailed magnetospheric processes is still in its infancy.

  3. Storm-Substorm Relations Workshop

    NASA Astrophysics Data System (ADS)

    Kan, Joe

    2006-06-01

    Magnetic storms in the magnetosphere can cause damage to communication satellites and large-scale power outages. The concept that a magnetic storm is a compilation of a series of substorms was proposed by Akasofu [1968]. However, Kamide [1992] showed that substorms are not a necessary condition for the occurrence of a magnetic storm. This controversy initiated a new era of research on the storm-substorm relation, which was the subject of a recent workshop in Banff, Alberta, Canada. The main topics discussed during the meeting included a brief overview of what a substorm is, how quasiperiodic substorm events and steady magnetospheric convection (SMC) events without substorms contribute to storms, and how plasma flows enhanced by magnetic reconnection in the plasma sheet contribute to substorms and storms.

  4. PC index and magnetic substorms

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Janzhura, Alexander; Sormakov, Dmitry; Podorozhkina, Nataly

    PC index is regarded as a proxy of the solar wind energy that entered into the magnetosphere as distinct from the AL and Dst indices, which are regarded as characteristics of the energy that realize in the magnetosphere in form of substorm and magnetic storms. This conclusion is based on results of analysis of relationships between the polar cap magnetic activity (PC-index) and parameters of the solar wind, on the one hand, relationships between changes of PC and development of magnetospheric substorms (AL-index) and magnetic storms (Dst-index), on the other hand. This paper describes in detail the following main results which demonstrate a strong connection between the behavior of PC and development of magnetic disturbances in the auroral zone: (1) magnetic substorms are preceded by the РС index growth (isolated and extended substorms) or long period of stationary PC (postponed substorms), (2) the substorm sudden onsets are definitely related to such PC signatures as leap and reverse, which are indicative of sharp increase of the PC growth rate, (3) substorms generally start to develop when the PC index exceeds the threshold level ~ 1.5±0.5 mV/m, irrespective of the substorm growth phase duration and type of substorm, (4) linear dependency of AL values on PC is typical of all substorm events irrespective of type and intensity of substorm.

  5. 27 August 2001 substorm: Preonset phenomena, two main onsets, field-aligned current systems, and plasma flow channels in the ionosphere and in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Mishin, V. M.; Mishin, V. V.; Lunyushkin, S. B.; Wang, J. Y.; Moiseev, A. V.

    2017-05-01

    We supplement the results of the 27 August 2001 substorm studied earlier in the series of papers. Described is the plasma flow in the nightside ionosphere from the near-polar region from the polar cap to the auroral oval during the substorm preonset phase and two expansion onsets, EO1 and EO2, produced by reconnection in the closed tail (magnetic reconnection (MR1) and in the open tail lobes (MR2), respectively. We discuss the location of the MR2 region (is it near, middle, and/or distant tail?) and the EO2 trigger mechanism. The upward substorm current wedge field-aligned current (FAC) and the downward FAC in the polar cap dusk sector that were both produced by different types of magnetosphere-ionosphere feedback instability are found to provide the main contribution to the system of FACs during EO1 and EO2. Also, we obtain the estimates for the EO1 and EO2 power and energy. Addressed are the variations in the tail lobe magnetic flux and their (variations) association with EO2. In addition, we describe a 3-D system of mesoscale cells, each of which involves a plasma vortex and a local FAC maximum. The cells of this system in the inner magnetosphere and in the tail lobes intensify one after other within 2 min interval. At last, we substantiate the assumption that the fast plasma flow recorded by the Cluster satellites 7 min prior to EO1 was a bursty bulk flow from the most distant tail.

  6. The Substorm Cycle at Mercury

    NASA Astrophysics Data System (ADS)

    Imber, S. M.; Slavin, J. A.

    2015-12-01

    The large-scale dynamic behavior of Mercury's highly compressed magnetosphere is primarily powered by magnetic reconnection between the solar wind and the planetary magnetic field. Reconnection transfers energy and momentum from the solar wind to the magnetosphere and drives the large-scale circulation of magnetic flux through the system, predominantly via the substorm cycle. We will present a statistical analysis of the average substorm amplitude, duration and frequency using magnetic field data acquired in orbit about Mercury by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. We will also present an example of steady magnetospheric convection in Mercury's magnetosphere, during which reconnection is ongoing both at the dayside magnetopause and in the magnetotail, but large-scale magnetic energy storage and release is not observed. We aim to ascertain the combination of internal magnetospheric and external solar wind parameters that lead to a substorm, or a period of steady magnetospheric convection in Mercury's magnetosphere.

  7. Substorm and High Speed Stream Observations During Solar Cyles 22 and 23

    NASA Astrophysics Data System (ADS)

    Tanskanen, E. I.; Slavin, J. A.; Tanskanen, A. J.; Viljanen, A.; Pulkkinen, T. I.; Koskinen, H. E.; Huttunen, K. E.

    2005-05-01

    Magnetic measurements from the MIRACLE network are used to identify substorms during solar cycles 22 and 23, from 1993 to 2004. For the first time substorm activity is examined over a complete solar cycle. In this study more than 5000 substorms are identified and their interplanetary drivers are examined. A new parameter called substorm number Rsu is formed based on (monthly) averages of substorm peak amplitudes. The substorm number measures magnetic activity of the Earth's magnetosphere in a way analogous to how sunspot number Rz estimates the level of Sun's magnetic activity. Analysis of WIND, ACE and SOHO interplanetary measurements indicate that high speed streams (HSS, with Sun-to-Earth velocities over 700 km/s) are the main drivers of the terrestrial substorms. The substorm number peaked in 1994-1995 and in 2003-2004 (at 3-4 years after the sunspot maximum), which is when the high speed streams occurred repeatedly every 27 days. During the years of repeated HSSs, substorms occurred more frequently, were more intense, and carried more magnetic energy to the auroral ionosphere, compared to the substorms existing during non-HSS intervals.

  8. Investigation of the Triggering Mechanism of Magnetospheric Substorm via 2-1/2 D Full-Particle Simulation

    NASA Astrophysics Data System (ADS)

    Uchino, H.; Machida, S.

    2012-12-01

    A physical process of the substorm triggering in the Earth's Magnetotail is thought to be closely related to the magnetic reconnection and the tearing instability. Recently we proposed a new scheme of the substorm onset called "Catapult Current Sheet Relaxation (CCSR) Model " to physically understand the results from GEOTAIL and THEMIS data. The CCSR Model has characters that are the decrease of the total pressure and thinning of the current sheet at the distance about -12Re in the magnetotail a few minutes before the substorm onset, and the simultaneous occurrence of the dipolarization at X~-10Re and the magnetic reconnection at X~-20Re at the time of the onset. In this study, we investigate a stability of the current sheet and the particle acceleration via particle simulation in order to assess the validity of the CCSR model and to clarify the mechanism of substorm onset. We give an initial magnetic field structure which is akin to the Earth's dipole magnetic field together with a stretched magnetic field by thin current sheet, and further add a weak northward magnetic field at the place where Near-Earth Neutral Line is expected to be formed. The results of simulation contain similar features that characterize the CCSR Model. A physically interpretation of the simulation result with the linear instability theory as well as comparison with observations will be given.

  9. On the influence of open magnetic flux on substorm intensity: Ground- and space-based observations

    NASA Astrophysics Data System (ADS)

    Clausen, L. B. N.; Milan, S. E.; Baker, J. B. H.; Ruohoniemi, J. M.; Glassmeier, K.-H.; Coxon, J. C.; Anderson, B. J.

    2013-06-01

    Using the location of maximum region 1 current determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment as a proxy for the open/closed field line boundary, we monitor the evolution of the amount of open magnetic flux inside the magnetosphere during 772 substorms. We then divide all substorms into three classes, depending on the amount of open flux at expansion phase onset. Studying the temporal variations during the substorms of each class for a number of related geophysical parameters, we find that substorms occurring while the amount of open flux is large are generally more intense. By intense we mean that the auroral electrojet, region 1 current, auroral brightness, tail dipolarization and flow speed, ground magnetic signatures, Pi2 wave power, as well as the intensity and extent of the substorm current wedge (SCW) are all larger than during substorms that occur on a contracted polar cap. The SCW manifests itself as an intensification of the nightside R1 and R2 current system after onset. Our analysis shows that to dispose of large amounts of accumulated open magnetic flux, large substorms are triggered in the terrestrial magnetosphere.

  10. Electrodynamics of solar wind-magnetosphere-ionosphere interactions

    NASA Technical Reports Server (NTRS)

    Kan, Joseph R.; Akasofu, Syun-Ichi

    1989-01-01

    The paper presents a coherent picture of fundamental physical processes in three basic elements of the solar-wind/magnetosphere/ionosphere coupling system: (1) the field-aligned potential structure which leads to the formation of auroral arcs, (2) the magnetosphere-ionosphere coupling which leads to the onset of magnetospheric substorms, and (3) the solar-wind/magnetosphere dynamo which supplies the power driving various magnetospheric processes. Process (1) is forced into existence by the loss-cone constriction effect when the upward field-aligned current density exceeds the loss-cone thermal flux limit. Substorm onset occurs when the ionosphere responds fully to the enhanced magnetospheric convection driven by the solar wind. Energy is transferred from the solar wind to the magnetosphere by a dynamo process, primarily on open field lines.

  11. Is energy storage and release part of the substorm process?

    NASA Technical Reports Server (NTRS)

    Clauer, C. R.

    1981-01-01

    Models for magnetospheric substorms were considered. A modified model which includes the growth phase, a time interval prior to the onset of the expansion phase, during which energy was transferred from a solar wind to the magnetosphere and stored for subsequent release, is discussed. Evidence for energy storage in the tail prior to substorm expansion for both isolated and moderate substorm activity is reviewed.

  12. Space weather and the safety of ground infrastructures. Numerical simulation and prediction of electromagnetic effects induced by real magnetospheric substorms in the Earth's models with real three-dimensional distribution of electrical conductivity

    NASA Astrophysics Data System (ADS)

    Kuvshinov, Alexey; Filippov, Sergey; Kalegaev, Vladimir; Sidorova, Larisa; Mukhametdinova, Ludmila; Pankratov, Oleg; Alexeev, Dmitry

    Strong eruptions at Sun’s surface produce large release of matter (plasma), which, with a speed of 800-1000 km/s (the solar wind), flows into interplanetary space. If the Earth appears to be on the way of the solar wind the interaction of the wind with the Earth's magnetosphere and the ionosphere leads to abnormal disturbance of fluctuating geomagnetic field. In the middle latitudes, the disturbances (geomagnetic storms) last a few days and have amplitudes up to 400 nT. At high latitudes, these perturbations (magnetospheric substorms) last a few hours and have amplitudes up to 3000 nT. According to Faraday’s law of induction, the fluctuating magnetic field in turn generates a electric field. The electric field for intense substorms can reach hundreds of volts/km in the polar region and generate very high, the so-called geomagnetic induced currents in the ground-based systems, such as power grids and pipelines. These currents are one of the most dangerous factors affecting the operation of the above systems. Thus extremely topical task in the field of "space weather" is the quantification and prediction of spatio-temporal distribution of the electric field during substorm activity. Despite the abundance of works carried out in this direction, the problem is still far from a satisfactory solution. In the field of modeling, researchers are still working with highly simplified models of both the source and the conducting Earth. As for prediction the situation is even worse. In this presentation we discuss a general formalism which allows for simulating the electric fields induced by real magnetospheric substorms in the spherical model of the Earth with real three-dimensional distribution of conductivity. We show the first results of such simulations. We also discuss a concept to predict substorm spatio-temporal pattern of the electric field.

  13. Substorm Current Wedge Revisited

    NASA Astrophysics Data System (ADS)

    Kepko, L.; McPherron, R. L.; Amm, O.; Apatenkov, S.; Baumjohann, W.; Birn, J.; Lester, M.; Nakamura, R.; Pulkkinen, T. I.; Sergeev, V.

    2015-07-01

    Almost 40 years ago the concept of the substorm current wedge was developed to explain the magnetic signatures observed on the ground and in geosynchronous orbit during substorm expansion. In the ensuing decades new observations, including radar and low-altitude spacecraft, MHD simulations, and theoretical considerations have tremendously advanced our understanding of this system. The AMPTE/IRM, THEMIS and Cluster missions have added considerable observational knowledge, especially on the important role of fast flows in producing the stresses that generate the substorm current wedge. Recent detailed, multi-spacecraft, multi-instrument observations both in the magnetosphere and in the ionosphere have brought a wealth of new information about the details of the temporal evolution and structure of the current system. While the large-scale picture remains valid, the new details call for revision and an update of the original view. In this paper we briefly review the historical development of the substorm current wedge, review recent in situ and ground-based observations and theoretical work, and discuss the current active research areas. We conclude with a revised, time-dependent picture of the substorm current wedge that follows its evolution from the initial substorm flows through substorm expansion and recovery.

  14. Magnetosphere of Earth: Geomagnetic Tail

    NASA Astrophysics Data System (ADS)

    Pulkkinen, T.; Murdin, P.

    2000-11-01

    The geomagnetic tail is an elongated region of the MAGNETOSPHERE OF EARTH extending from the near-Earth space in the antisunward direction. It acts as a giant energy reservoir for the magnetosphere and is therefore an important participant in dynamic processes such as GEOMAGNETIC STORMS and substorms (see MAGNETOSPHERE OF EARTH: SUBSTORMS)....

  15. Space climate implications from substorm frequency

    NASA Astrophysics Data System (ADS)

    Newell, P. T.; Gjerloev, J. W.; Mitchell, E. J.

    2013-10-01

    solar wind impacting the Earth varies over a wide range of time scales, driving a corresponding range of geomagnetic activity. Past work has strongly indicated that the rate of merging on the frontside magnetosphere is the most important predictor for magnetospheric activity, especially over a few hours. However, the magnetosphere exhibits variations on other time scales, including UT, seasonal, and solar cycle variations. Much of this geomagnetic variation cannot be reasonably attributed to changes in the solar wind driving—that is, it is not created by the original Russell-McPherron effect or any generalization thereof. In this paper we examine the solar cycle, seasonal, and diurnal effects based upon the frequency of substorm onsets, using a data set of 53,000 substorm onsets. These were identified through the SuperMAG collaboration and span three decades with continuous coverage. Solar cycle variations include a profound minimum in 2009 (448 substorms) and peak in 2003 (3727). The magnitude of this variation (a factor of 8.3) is not explained through variations in estimators of the frontside merging rate (such as dΦMP/dt), even when the more detailed probability distribution functions are examined. Instead, v, or better, n1/2v2 seems to be implicated in the dramatic difference between active and quiet years, even beyond the role of velocity in modulating merging. Moreover, we find that although most substorms are preceded by flux loading (78.5% are above the mean and 83.8% above median solar wind driving), a high solar wind v is almost as important (68.3% above mean, 74.8% above median). This and other evidence suggest that either v or n1/2v2 (but probably not p) plays a strong secondary role in substorm onset. As for the seasonal and diurnal effects, the elliptical nature of the Earth's orbit, which is closest to the Sun in January, leads to a larger solar wind driving (measured by Bs, vBs, or dΦMP/dt) in November, as is confirmed by 22 years of solar wind

  16. Some features of the Pi2 bursts during triggered and nontriggered substorms

    NASA Astrophysics Data System (ADS)

    Klain, B. I.; Kurazhkovskaya, N. A.

    2009-04-01

    The character of amplitudes and duration distributions of the Pi2 bursts observed in nighttime was investigated during development magnetospheric substorms. The analog recordings of the middle latitude Borok observatory (corrected geomagnetic latitude and longitude: 53.6; 114.4) for 1994-1995 were used in the investigation. We separate the Pi2 bursts into two classes: 1) Pi2 observed during substorms which were triggered by the external factors and 2) Pi2 observed during substorms which were occurred spontaneously. Both northward and southward turnings IMF Bz were considered as the possible triggers of the magnetospheric substorms. It was found that the distributions of Pi2 bursts amplitudes of both classes are submitted to the power law. The Pi2 bursts observed during triggered substorms are the power-low index of the amplitudes distribution equal 2.64. To the power dependence with an index 2.50 are submitted Pi2 bursts observed during nontriggered substorms. The results obtained make it possible to assume that the sequences of wave packets of Pi2 pulsations are intermittent process. The analysis of distributions of the Pi2 bursts duration two classes was shown that it are approximated by exponential functions with different indices. If the expansion phase of substorms is connected with IMF orientation change the index of approximated function made 0.43. In case of nontriggered substorms the index of approximated function equal 0.36. It is supposed that on the basis of the obtained indices it is possible on a qualitative level to estimate a turbulence degree of plasma on the night side magnetosphere during development of substorm activity. The work was supported by the Program of Basic Researches of Presidium of Russian Academy of Science "Change of a surroundings and climate: Extreme Natural Phenomena and Catastrophes"

  17. Identification of critical substorm-expansion-phase phenomena: Problems addressable with GEM observations

    SciTech Connect

    Lyons, L.R.

    1994-09-01

    Understanding the physics of the substorm process is currently a crucial topic in magnetospheric physics. Fundamental to this understanding is the determination of what phenomena occur in the magnetosphere during the expansion phase, where these phenomena occur, and how they propagate during the expansion phase. Satellite observations have given researchers important point measurements of what happens; however there is potential for enhancing the use of ground-based observations to study the substorm phenomena. Such enhanced use of ground-based measurements is already taking place as part of the GEM (Geospace Environment Modeling) boundary-layer campaign and is planned to continue throughout the tail/substorm campaign. This report identifies expansion-phase phenomena observed locally within the nightside magnetosphere and from the ground, believed to be of fundamental importance for understanding large-scale substorm processes. The phenomena observed in situ are related to the phenomena observed from the ground. The primary goal is to identify outstanding questions that could be addressed during the GEM tail/substorm campaign using ground-based data from GEM observing periods in coordination with available satellite observations.

  18. Substorms: The Attempt at Magnetospheric Dynamic Equilibrium between Magnetically-Driven Frontside Reconnection and Particle-Driven Reconnection in a Multiple-Current-Sheet Magnetotail

    NASA Astrophysics Data System (ADS)

    Sofko, G. J.; Hussey, G. C.; McWilliams, K. A.; Reimer, A. S.

    2016-12-01

    We propose a multi-current-sheet model for magnetic substorms. Those storms are normally driven by frontside magnetically-driven reconnection (MDRx), in which the diffusion zone current JD and the electric field E have a "load" relationship JD*E >0, indicating transfer if magnetic energy to the particles in the "reconnection jets". As a result of lobe field line transport over the north and south poles, polar cap particles are subject to parallel energization as they flow upward out of the ionosphere. These particles convectively drift toward the equator and subsequently mirror near the Neutral Sheet (NSh) region, forming an extended westward NSh current sheet which is unstable and "tears up" into multiple current sheets. Each current sheet has very different behaviour at its ends: (a) strong magnetic pressure and weak particle pressure at its tailward end; (b) strong particle pressure and weak magnetic field at its earthward end. Therefore, in each Separation Zone (SZ) between current sheets, a strong eastward magnetic curl develops. The associated eastward SZ current, caused by diamagnetic electron drift, is squeezed by the repulsion of the westward currents tailward and earthward. That current becomes intense enough to act as a diffusion zone for "generator-type" or Particle-driven reconnection (PDRx) for which JD*E<0, indicating that the particles return energy to the magnetic field. The PDRx produces a Dipolarization Front (DF) on the earthward side of the SZ and a Plasmoid (PMD) on the tailward side. Such DF-PMD pairs form successively in time and radial downtail SZ distance. In this way, the magnetosphere attempts to achieve a dynamic equilibrium between magnetic and particle energy.

  19. The Role of Self-Organized Criticality in the Substorm Phenomenon and its Relation to Localized Reconnection in the Magnetospheric Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Klimas, Alex J.; Valdivia, J. A.; Vassiliadis, D.; Baker, D. N.; Hesse, M.; Takalo, J.

    1999-01-01

    Evidence is presented that suggests there is a significant self-organized criticality (SOC) component in the dynamics of substorms in the magnetosphere. Observations of BBFs, fast flows, localized dipolarizations, plasma turbulence, etc. are taken to show that multiple localized reconnection sites provide the basic avalanche phenomenon in the establishment of SOC in the plasma sheet. First results are presented from a continuing plasma physical study of this avalanche process. A one-dimensional resistive MHD model of a magnetic field reversal is discussed. Resistivity, in this model, is self-consistently generated in response to the excitation of an idealized current-driven instability. When forced by convection of magnetic flux into the field reversal region, the model yields rapid magnetic field annihilation through a dynamic behavior that is shown to exhibit many of the characteristics of SOC. Over a large range of forcing strengths, the annihilation rate is shown to self-adjust to balance the rate at which flux is convected into the reversal region. Several analogies to magnetotail dynamics are discussed: (1) It is shown that the presence of a localized criticality in the model produces a remarkable stability in the global configuration of the field reversal while simultaneously exciting extraordinarily dynamic internal evolution. (2) Under steady forcing, it is shown that a loading-unloading cycle may arise that, as a consequence of the global stability, is quasi-periodic and, therefore, predictable despite the presence of internal turbulence in the field distribution. Indeed, it is shown that the global loading-unloading cycle is a consequence of the internal turbulence. (3) It is shown that, under steady, strong forcing the loading-unloading cycle vanishes. Instead, a recovery from a single unloading persists indefinitely. The field reversal is globally very steady while internally it is very dynamic as field annihilation goes on at the rate necessary to

  20. Substorm Current Wedge at Earth and Mercury

    NASA Astrophysics Data System (ADS)

    Kepko, L.; Glassmeier, K.-H.; Slavin, J. A.; Sundberg, T.

    2015-01-01

    This chapter reviews magnetospheric substorms and dipolarizations observed at both Earth and Mercury. It briefly discusses new insights into the physics of the substorm current wedge (SCW) that have been revealed the past few years. The formation and evolution of the SCW are closely tied to the braking of flows convecting flux away from the reconnection site and the resultant near-planet flux pileup that creates the dipolarization. At Earth, the SCW plays a critical role in substorms, coupling magnetospheric to ionospheric motions, deflecting incoming plasma flows, and regulating the dissipation of pressure built up in the near-Earth magnetosphere during dipolarization. The lack of a conducting boundary at Mercury provides a natural experiment to examine the role of an ionosphere on regulating magnetospheric convection. Energetic particles may play a much greater role within substorms at Mercury than at Earth, providing another opportunity for comparative studies.

  1. Comparative study on dynamics associated with terrestrial and Jovian substorms

    NASA Astrophysics Data System (ADS)

    Ge, Yasong

    Terrestrial substorms have been studied for over four decades and our understanding about this phenomenon has improved through those studies. However, many issues regarding substorms are still controversial, especially the initiation mechanism of substorm onset. To understand the initiation mechanism, we have to first answer some important questions. What is the substorm expansion onset? What is the physics behind its phenomenological definition? Where does the initiation start? What is the relation of tail reconnection with near-Earth onsets? Where does tail reconnection occur? While one way to understand better the physics of substorms is to increase the number of spacecraft and the resolution of ground observations, another way is to compare substorm phenomena between different planets. In this study, we investigate the different phases of substorms both on the Earth and Jupiter. For Jovian dynamic event, we need to know if they are substorms? How are they driven? How can we better understand terrestrial substorms through studying Jovian substorms? We used Polar, GOES, Cluster and ground-station observations to study terrestrial substorms and used the Galileo observations to study Jovian dynamic events. A 3-day growth phase of Jovian substorm is discovered, which is also found driven by the internal processes including mass-loading at Io instead of the solar wind. This discovery establishes the substorm nature of those dynamics events which have counterparts of key elements of terrestrial substorms, including the connection of those events with the Jupiter's polar auroral activity. Near-planet dipolarization caused by the mid-tail reconnection is also investigated. In the near-Earth tail region, dipolarizations appear to be associated with mid-tail reconnections, near-tail flow braking and formation of substorm current wedge. In both magnetospheres, major onsets of substorms are found to be due to the major tail reconnection which can globally release the loaded

  2. Relation of the auroral substorm to the substorm current wedge

    NASA Astrophysics Data System (ADS)

    McPherron, Robert L.; Chu, Xiangning

    2016-12-01

    The auroral substorm is an organized sequence of events seen in the aurora near midnight. It is a manifestation of the magnetospheric substorm which is a disturbance of the magnetosphere brought about by the solar wind transfer of magnetic flux from the dayside to the tail lobes and its return through the plasma sheet to the dayside. The most dramatic feature of the auroral substorm is the sudden brightening and poleward expansion of the aurora. Intimately associated with this expansion is a westward electrical current flowing across the bulge of expanding aurora. This current is fed by a downward field-aligned current (FAC) at its eastern edge and an upward current at its western edge. This current system is called the substorm current wedge (SCW). The SCW forms within a minute of auroral expansion. FAC are created by pressure gradients and field line bending from shears in plasma flow. Both of these are the result of pileup and diversion of plasma flows in the near-earth plasma sheet. The origins of these flows are reconnection sites further back in the tail. The auroral expansion can be explained by a combination of a change in field line mapping caused by the substorm current wedge and a tailward growth of the outer edge of the pileup region. We illustrate this scenario with a complex substorm and discuss some of the problems associated with this interpretation.

  3. Occurrence frequencies of IMF triggered and nontriggered substorms

    NASA Technical Reports Server (NTRS)

    Hsu, Tung-Shin; McPherron, Robert L.

    2003-01-01

    The occurrence of triggered and nontriggered substorm are examined in light of current interest in such issues as substorm identification, IMF By variations, and potentially undetected small-scale solar wind perturbation. Global substorms are identified using a sudden, persistent decrease in the AL index. The onset of this global expansion is taken to be the time of the Pi 2 burst nearest in time to the beginning of the AL, decrease. IMF triggers were identified both subjectively through visual scanning of the data and automatically with a computer algorithm. Both northward turnings of the IMF Bz and decreases in the amplitude of the By component were considered as possible triggers. Two different solar wind monitors were used in the investigation: IMP-8 in a circular orbit with a distance 12 to approx.35 Re to the Earth-Sun line and ISEE-2 in an elliptical orbit with a distance only 5 to approx.10 Re to the Earth-Sun line. The IMP-8 results show that the triggering probability does not depend on the distance of the monitor from the Earth-Sun line in the range 12-35 Re. The ISEE dataset shows that closer than 12 Re the triggering probability is the same as it is in the IMP-8 data set. Thus there appears to be no dependence of triggering on the location of the monitor provided it is within 35 Re of the Earth. We also demonstrate that including the By component does not significantly increase the probability of substorm triggering. Approximately 60% of all substorms appear to be triggered. Of the 40% for which we could not identify a trigger, 10% occurred while the IMF was northward. The data suggest that substorm onset is a consequence of an internal magnetospheric instability that is highly sensitive to changes in magnetospheric convection induced by a sudden change in the IMF, but that these changes are not always necessary.

  4. Substorm statistics: Occurrences and amplitudes

    SciTech Connect

    Borovsky, J.E.; Nemzek, R.J.

    1994-05-01

    The occurrences and amplitudes of substorms are statistically investigated with the use of three data sets: the AL index, the Los Alamos 3-satellite geosynchronous energetic-electron measurements, and the GOES-5 and -6 geosynchronous magnetic-field measurements. The investigation utilizes {approximately} 13,800 substorms in AL, {approximately} 1400 substorms in the energetic-electron flux, and {approximately} 100 substorms in the magnetic field. The rate of occurrence of substorms is determined as a function of the time of day, the time of year, the amount of magnetotail bending, the orientation of the geomagnetic dipole, the toward/away configuration of the IMF, and the parameters of the solar wind. The relative roles of dayside reconnection and viscous coupling in the production of substorms are assessed. Three amplitudes are defined for a substorms: the jump in the AL index, the peak of the >30-keV integral electron flux at geosynchronous orbit near midnight, and the angle of rotation of the geosynchronous magnetic field near midnight. The substorm amplitudes are statistically analyzed, the amplitude measurements are cross correlated with each other, and the substorm amplitudes are determined as functions of the solar-wind parameters. Periodically occurring and randomly occurring substorms are analyzed separately. The energetic-particle-flux amplitudes are consistent with unloading and the AL amplitudes are consistent with direct driving plus unloading.

  5. Predictions of Substorms and Intensifications Following Northward Turnings of the IMF

    NASA Technical Reports Server (NTRS)

    Blanchard, G. T.; Lyons, L. R.; Spann, J.

    1999-01-01

    Substorms are often observed to occur at the end of intervals of Southward interplanetary magnetic field (IMF), i.e. following the northward turning. Despite the significant correlation between northward turning and substorms, no direct causal relationship between northward turnings and substorms has been demonstrated. Assuming such a causal relationship, we predict that substorms will occur within a particular interval following the observation of a northward turning in the IMF. We observe 16 northward turnings following steady, southward IMF in data taken by the WIND spacecraft magnetic field instrument (MFI). To ensure that the northward turning was observed at the magnetosphere, we require that the northward turning also be observed by instruments on either one of Geotail or IMP-8 while the separation of the second spacecraft from WIND was more that 10 R(sub E). These two-spacecraft observations also allow us to predict more accurately the arrival time of the northward turning at the Earth. Of the predictions substorms, 10 predictions were clearly successful to within +/- 12 min. Five predictions failed, but the failures reveal clear shortcomings in the criteria for a northward turning that we correct. The failures were caused by an increase in the absolute value of B(sub YGSM) simultaneous with the northward turning in 3 cases, and a weak southward IMF preceding the northward turning in 2 cases. The final northward turning arrived in the recovery phase of an ongoing substorm, and resulted in unusual auroral activity. The implication of the predictability of substorms following sharp northward turnings is that the postulated causal relationship between northward turnings and substorm onset exists. The effect of increases in the absolute value of B(sub YGSM) to negate the triggering ability of northward turnings suggests that the triggering mechanism involves sharp reductions in the magnetospheric convection electric field.

  6. Predictions of Substorms and Intensifications Following Northward Turnings of the IMF

    NASA Technical Reports Server (NTRS)

    Blanchard, G. T.; Lyons, L. R.; Spann, J.

    1999-01-01

    Substorms are often observed to occur at the end of intervals of Southward interplanetary magnetic field (IMF), i.e. following the northward turning. Despite the significant correlation between northward turning and substorms, no direct causal relationship between northward turnings and substorms has been demonstrated. Assuming such a causal relationship, we predict that substorms will occur within a particular interval following the observation of a northward turning in the IMF. We observe 16 northward turnings following steady, southward IMF in data taken by the WIND spacecraft magnetic field instrument (MFI). To ensure that the northward turning was observed at the magnetosphere, we require that the northward turning also be observed by instruments on either one of Geotail or IMP-8 while the separation of the second spacecraft from WIND was more that 10 R(sub E). These two-spacecraft observations also allow us to predict more accurately the arrival time of the northward turning at the Earth. Of the predictions substorms, 10 predictions were clearly successful to within +/- 12 min. Five predictions failed, but the failures reveal clear shortcomings in the criteria for a northward turning that we correct. The failures were caused by an increase in the absolute value of B(sub YGSM) simultaneous with the northward turning in 3 cases, and a weak southward IMF preceding the northward turning in 2 cases. The final northward turning arrived in the recovery phase of an ongoing substorm, and resulted in unusual auroral activity. The implication of the predictability of substorms following sharp northward turnings is that the postulated causal relationship between northward turnings and substorm onset exists. The effect of increases in the absolute value of B(sub YGSM) to negate the triggering ability of northward turnings suggests that the triggering mechanism involves sharp reductions in the magnetospheric convection electric field.

  7. Substorms At Jupiter: Galileo Observations of Transient Reconnection in The Near Tail

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Khurana, K. K.; Kivelson, M. G.; Huddleston, D. E.

    2000-01-01

    The magnetic flux content of the Jovian magnetosphere is set by the internal dynamo, but those magnetic field lines are constantly being loaded by heavy ions at the orbit of lo and dragged inexorably outward by the centrifugal force. Vasyliunas has proposed a steady state reconnecting magnetospheric model that sheds plasma islands of zero net magnetic flux and returns nearly empty flux tubes to the inner magnetosphere. The Galileo observations indicate that beyond 40 Rj the current sheet begins to tear and beyond 50 Rj on the nightside explosively reconnects as the tearing site reaches the low density lobe region above and below the current sheet. Small events occur irregularly but on average about every 4 hours and large events about once a day. The magnetic flux reconnected in such events amounts up to about 70,000 Webers/sec and is sufficient to return the outwardly convected magnetic flux to the inner magnetosphere. Since this process releases plasmoids into the jovian tail, as do terrestrial substorms; since this process involves explosive reconnection across the current sheet on the nightside of the planet, as do terrestrial substorms; and since the process is a key in closing the circulation pattern of the magnetic and plasma flux, as it is in terrestrial substorms; we refer to these events as jovian substorms.

  8. What is the Relationship between the Solar Wind and Storms/Substorms?

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Burlaga, L. F.

    1999-01-01

    The interplanetary magnetic field (IMF) carried past the Earth by the solar wind has long been known to be the principal quantity that controls geomagnetic storms and substorms. Intervals of strong southward IMF with durations of at least a significant fraction of a day produce storms, while more typical, shorter intervals of less-intense southward fields produce substorms. The strong, long-duration southward fields are generally associated with coronal mass ejections and magnetic clouds or else they are produced by interplanetary dynamics initiated by fast solar wind flows that compress preexisting southward fields. Smaller, short-duration southward fields that occur on most days are related to long period waves, turbulence, or random variations in the IMF. Southward IMF enhances dayside reconnection between the IMF and the Earth's dipole with the reconnected field lines supplementing open field lines of the geomagnetic tail and producing an expanded polar cap and increased tail energy. Although the frequent storage of solar wind energy and its release during substorms is the most common mode of solar wind/magnetosphere interaction, under certain circumstances, steady southward IMF seems to produce intervals of relatively steady magnetosphere convection without substorms. During these latter times, the inner magnetosphere remains in a stressed tail-like state while the more distant magnetotail has larger northward field and more dipolar-like field lines. Recent evidence suggests that enhanced magnetosphere particle densities associated with enhanced solar wind densities allow more particles to be accelerated for the ring current, thus creating larger storms.

  9. Planetary magnetospheres

    NASA Technical Reports Server (NTRS)

    Stern, D. P.; Ness, N. F.

    1981-01-01

    A concise overview is presented of our understanding of planetary magnetospheres (and in particular, of that of the Earth), as of the end of 1981. Emphasis is placed on processes of astrophysical interest, e.g., on particle acceleration, collision-free shocks, particle motion, parallel electric fields, magnetic merging, substorms, and large scale plasma flows. The general morphology and topology of the Earth's magnetosphere are discussed, and important results are given about the magnetospheres of Jupiter, Saturn and Mercury, including those derived from the Voyager 1 and 2 missions and those related to Jupiter's satellite Io. About 160 references are cited, including many reviews from which additional details can be obtained.

  10. Substorm Events from Observations of Energetic Particle Injections at Geosynchronous Orbit

    NASA Astrophysics Data System (ADS)

    Yakymenko, K.; Borovsky, J.

    2016-12-01

    We present a new algorithm for identification of substorm events based on observation that the specific entropy S = T/n^{2/3} of energetic electron population at geosynchronous orbit decreases significantly when a fresh injection of electrons occurs. The time of injection events is refined by exploring the energy dispersion in the injected cluster of particles. More than 35 years of observations from CPA and SOPA instruments on board of the LANL geosynchronous satellites are analyzed and list of substorm events is created. The list is compared with various substorm onset lists identified from three other sets of data: SuperMAG index, Midlatitude Positive Bay index, and global auroral images. It is established that different data sets and algorithms yield different sets of events. We show that majority of events identified from ground-based magnetometer data by various known from the literature algorithms are intensifications of an ongoing substorm event rather then true substorm onsets. Difficulties and pitfalls in identification of substorm events from different data sets are discussed. A comprehensive statistical study of the occurrence rate and recurrence time of magnetospheric substorms versus parameters of solar-wind plasma passing the Earth,versus the level of geomagnetic activity, and time through three solar cycles was performed. Substorm occurrence rates were studied in 70 high-speed-stream-driven storms: the rate is anomalously low in the calms before the storms, the rate increases rapidly at storm onset, and the rate is sustained at high levels for days through the high speed streams and into the trailing edges. Substorm occurrence rates were studied in 47 CME-sheath-driven storms wherein the rate jumps up as the interplanetary shock passes the Earth and is sustained into the sheath. The passage of an interplanetary shock does not itself produce a substorm.

  11. Substorm electrodynamics

    NASA Technical Reports Server (NTRS)

    Stern, David P.

    1990-01-01

    The present one-dimensional model analysis of substorm electrodynamics proceeds from the standard scenario in which the plasma sheet collapses into a neutral sheet, and magnetic merging occurs between the two tail lobes; plasma flows into the neutral sheet from the lobes and the sides, undergoing acceleration in the dawn-dusk direction. The process is modified by the tendency of the accelerated plasma to unbalance charge neutrality, leading to an exchange of electrons with the ionosphere in order to maintain neutrality. The cross-tail current is weakened by the diversion: this reduces the adjacent lobe-field intensity, but without notable effects apart from a slight expansion of the tail boundary.

  12. A Bright Future for Substorms

    NASA Astrophysics Data System (ADS)

    Kissinger, J.; McPherron, R. L.

    2010-09-01

    Tenth International Conference on Substorms; San Luis Obispo, California, 22-26 March 2010; Intense auroral displays are caused by substorms, events in the Earth's magnetosphere consisting of an abundance of plasma physics processes. More than 120 scientists gathered to discuss the latest findings on this phenomenon at a conference organized by Vassilis Angelopoulos, Larry R. Lyons, and Robert L. McPherron of the University of California, Los Angeles. Just as a thunderstorm cannot be properly analyzed with a single weather station, substorms cannot be properly studied with a single satellite in the vastness of space. Recent satellite missions now provide several simultaneous observations of key processes. Extensive networks of ionospheric radars, magnetometers, and all-sky imagers extend around the world. This has resulted in unprecedented coverage and conjunctions, brightening scientists' understanding of substorms.

  13. Correlative comparison of geomagnetic storms and auroral substorms using geomagnetic indeces. Master's thesis

    SciTech Connect

    Cade, W.B.

    1993-06-01

    Partial contents include the following: (1) Geomagnetic storm and substorm processes; (2) Magnetospheric structure; (3) Substorm processes; (4) Data description; (5) Geomagnetic indices; and (6) Data period and data sets.

  14. The roles of direct input of energy from the solar wind and unloading of stored magnetotail energy in driving magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Rostoker, G.; Akasofu, S. I.; Baumjohann, W.; Kamide, Y.; Mcpherron, R. L.

    1987-01-01

    The contributions to the substorm expansive phase of direct energy input from the solar wind and from energy stored in the magnetotail which is released in an unpredictable manner are considered. Two physical processes for the dispensation of the energy input from the solar wind are identified: (1) a driven process in which energy supplied from the solar wind is directly dissipated in the ionosphere; and (2) a loading-unloading process in which energy from the solar wind is first stored in the magnetotail and then is suddenly released to be deposited in the ionosphere. The pattern of substorm development in response to changes in the interplanetary medium has been elucidated for a canonical isolated substorm.

  15. The roles of direct input of energy from the solar wind and unloading of stored magnetotail energy in driving magnetospheric substorms

    NASA Technical Reports Server (NTRS)

    Rostoker, G.; Akasofu, S. I.; Baumjohann, W.; Kamide, Y.; Mcpherron, R. L.

    1987-01-01

    The contributions to the substorm expansive phase of direct energy input from the solar wind and from energy stored in the magnetotail which is released in an unpredictable manner are considered. Two physical processes for the dispensation of the energy input from the solar wind are identified: (1) a driven process in which energy supplied from the solar wind is directly dissipated in the ionosphere; and (2) a loading-unloading process in which energy from the solar wind is first stored in the magnetotail and then is suddenly released to be deposited in the ionosphere. The pattern of substorm development in response to changes in the interplanetary medium has been elucidated for a canonical isolated substorm.

  16. Proton aurora and substorm intensifications

    NASA Technical Reports Server (NTRS)

    Samson, J. C.; Xu, B.; Lyons, L. R.; Newell, P. T.; Creutzberg, F.

    1993-01-01

    Ground based measurements from the CANOPUS array of meridian scanning photometers and precipitating ion and electron data from the DMSP F9 satellite show that the electron arc which brightens to initiate substorm intensifications is formed within a region of intense proton precipitation that is well equatorward (approximately four to six degrees) of the nightside open-closed field line boundary. The precipitating protons are from a population that is energized via earthward convection from the magnetotail into the dipolar region of the magnetosphere and may play an important role in the formation of the electron arcs leading to substorm intensifications on dipole-like field lines.

  17. The Substorm Current Wedge Revisited

    NASA Astrophysics Data System (ADS)

    Kepko, Larry; McPherron, Robert; Apatenkov, Sergey; Baumjohann, Wolfgang; Birn, Joachim; Lester, Mark; Nakamura, Rumi; Pulkkinen, Tuija; Sergeev, Victor

    2015-04-01

    Almost 40 years ago the concept of the substorm current wedge was developed to explain the magnetic signatures observed on the ground and in geosynchronous orbit during substorm expansion. In the ensuing decades new observations, including radar and low-altitude spacecraft, MHD simulations, and theoretical considerations have tremendously advanced our understanding of this system. The AMPTE/IRM, THEMIS and Cluster missions have added considerable observational knowledge, especially on the important role of fast flows in producing the stresses that generate the substorm current wedge. Recent detailed, multi-spacecraft, multi-instrument observations both in the magnetosphere and in the ionosphere have brought a wealth of new information about the details of the temporal evolution and structure of the current system. In this paper, we briefly review recent in situ and ground-based observations and theoretical work that have demonstrated a need for an update of the original picture. We present a revised, time-dependent picture of the substorm current wedge that follows its evolution from the initial substorm flows through substorm expansion and recovery, and conclude by identifying open questions.

  18. Substorm theories: United they stand, divided they fall

    NASA Technical Reports Server (NTRS)

    Erickson, Gary M.

    1995-01-01

    Consensus on the timing and mapping of substorm features has permitted a synthesis of substorm models. Within the synthesis model the mechanism for onset of substorm expansion is still unknown. Possible mechanisms are: growth of an ion tearing mode, current disruption by a cross-field current instability, and magnetosphere-ionosphere coupling. While the synthesis model is consistent with overall substorm morphology, including near-Earth onset, none of the onset theories, taken individually, appear to account for substorm expansion onset. A grand synthesis with unification of the underlying onset theories appears necessary.

  19. Comparative study of a substorm event by satellite observation and model simulation

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Ma, ShuYing; Ridley, A. J.

    2010-03-01

    A substorm event has been simulated for the first time by using SWMF (Space Weather Modeling Framework) developed by the University of Michigan. The model results have been validated using Geotail and Cluster satellite observations. The substorm onset occurs at 22:08 UT on September 28 2004, as identified from FUV WIC observations on the NASA IMAGE spacecraft. SWMF can couple effectively the magnetosphere, inner magnetosphere and ionosphere processes and is driven by the solar wind and IMF (Interplanetary Magnetic Field) parameters, which are measured by ACE satellite and time delayed to the upstream boundary of the model. It shows that (1) SWMF can predict well the large-scale variations of the magnetospheric magnetic field and ionospheric currents during the substorm event; and (2) the accuracy of the time delay of the solar wind from ACE to the outer boundary of the model has great effects on the model results. Finally, the substorm trigger mechanism has been discussed and the way of improvement of the model has been pointed out.

  20. Energetics of the magnetosphere

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1980-01-01

    The approximate magnitudes of several power inputs and energies associated with the Earth's magnetosphere will be derived. They include: Solar wind power impinging on the dayside magnetopause approximately 1.4 10 to the 13th power watt; power input to cross tail current approximately 3 10 to the 11th power watt; energy of moderate magnetic storm approximately 2 10 to the 15th power joule; power related to the flow of j approximately 1 to 3 10 to the 11th power watt; average power deposited by the aurora approximately 2 10 to the 10th power watt. Stored magnetic energy: released in a substorm approximately 1.5 10 to the 14th power joule. Compared to the above, the rate at which energy is released locally in magnetospheric regions where magnetic merging occurs is probably small. Merging is essential, however, for the existence of open field lines, which provide the most likely explanation for some major energy inputs listed here. Merging is also required if part of the open flux of the tail lobes is converted into closed flux, as seems to happen during substorms. Again, most of the energy release becomes evident only beyond the merging region, though some particles may gain appreciable energy in that region itself, if the plasma sheet is completely squeezed out and the high latitude lobes interact directly.

  1. Current understanding of magnetic storms: Storm-substorm relationships

    SciTech Connect

    Kamide, Y.; Gonzalez, W.D.; Baumjohann, W.; Daglis, I.A.; Grande, M.; Joselyn, J.A.; Singer, H.J.; McPherron, R.L.; Phillips, J.L.; Reeves, E.G.; Rostoker, G.; Sharma, A.S.; Tsurutani, B.T.

    1998-08-01

    the storm-time ring current. An apparently new controversy regarding the relative importance of the two processes is thus created. It is important to identify the role of substorm occurrence in the large-scale enhancement of magnetospheric convection driven by solar wind electric fields. (3) Numerical schemes for predicting geomagnetic activity indices on the basis of solar/solar wind/interplanetary magnetic field parameters continue to be upgraded, ensuring reliable techniques for forecasting magnetic storms under real-time conditions. There is a need to evaluate the prediction capability of geomagnetic indices on the basis of physical processes that occur during storm time substorms. (4) It is crucial to differentiate between storms and nonstorm time substorms in terms of energy transfer/conversion processes, i.e., mechanical energy from the solar wind, electromagnetic energy in the magnetotail, and again, mechanical energy of particles in the plasma sheet, ring current, and aurora. To help answer the question of the role of substorms in energizing ring current particles, it is crucial to find efficient magnetospheric processes that heat ions up to some minimal energies so that they can have an effect on the strength of the storm time ring current. (5) The question of whether the {ital Dst} index is an accurate and effective measure of the storm time ring-current is also controversial. In particular, it is demonstrated that the dipolarization effect associated with substorm expansion acts to reduce the {ital Dst} magnitude, even though the ring current may still be growing. {copyright} 1998 American Geophysical Union

  2. Spatially Resolved Substorm Dynamical Model with Internal and External Substorm Triggers

    NASA Astrophysics Data System (ADS)

    Horton, W.; Crabtree, C.; Weigel, R. S.; Vassiliadis, D.; Doxas, I.

    2002-12-01

    A spatially-resolved nonlinear dynamics model of the coupled solar wind driven magnetosphere-ionosphere system is developed for the purpose of determining the electrical power flow from the solar wind through the nightside magnetosphere into the ionosphere. The model is derived from Maxwell equations and nonlinear plasma dynamics and focuses on the key conservation laws of mass, charge and energy in the power transfer elements in this complex dynamical system. The models has numerous feedback and feedforward loops for six forms of the distributed energy storage in the M-I system. In contrast to neural networks, the model delineates physically realizable time ordered sequence of energetic events in substorm dynamics. Three types of energy releases are observed in the substorm data and studied with the model. Type I events occur for solar wind conditions that lead to the creation of a near Earth neutral line (NENL) in the geomagnetic tail. Other solar wind conditions lead dominantly to the onset of convection in flux tubes with foot points in the auroral region that produced enhanced field aligned currents (FACs) closing in the ionosphere. These are the type II and type III events. In type II events a sudden northward turning of the IMF produces a transient mis-alignment of the pressure gradient with the gradient of the flux volumes as in the Lyons model. Large transient substorm current wedge and auroral region 1 sense currents are driven by the steep near-Earth pressure gradient in these events type II events. In type III events the slower evolving IMF field directly drives the nightside M-I system. This is the directly driven auroral substorm. We use physics-based filters to classify events in historical databases, and we use the 2-1/2D transport model to simulate the events for model solar wind inputs. The results of the research stress the need for more accurate determinations of the day-side magnetopause arrival times of structures in the solar wind required

  3. Using MMS measurements to validate models of reconnection-driven magnetotail reconfiguration and particle acceleration during substorms

    NASA Astrophysics Data System (ADS)

    Baker, Daniel N.

    2016-04-01

    New data from the Magnetospheric Multiscale (MMS) mission confirms and greatly extends the view that substorms are a configurational instability driven by magnetic reconnection. We have studied in detail a powerful storm period in June 2015 which shows that substorm events seen sequentially by the four MMS spacecraft subsequently feed the powerful enhancement of the radiation belts observed by the Van Allen Probes mission. Several sequences of significant southward IMF along with a period of high (VSW≥500 km/s) solar wind speed occurred following a strong interplanetary shock wave impact on the magnetosphere. We see that substorms provide a "seed" population, while high-speed solar wind drives the acceleration to relativistic energies in this two-step geomagnetic activity scenario. Thus, MMS data help validate models that invoke reconnection as a fundamental driver of magnetospheric particle acceleration. The data for several separate events on 22 June 2015 show that the magnetosphere progresses through a specific, well-observed sequence of energy-loading and stress-developing states until the entire system suddenly reconfigures. Energetic electron fluxes measured by the several MMS spacecraft reveal the clear temporal occurrence characteristics and the obvious relationships to concurrently measured solar wind drivers. This shows that enhancements in substorms are a key first step in the acceleration of radiation belt electrons to high energies as observed subsequently by the Van Allen Probes instrumentation. Thus, this high-resolution observational evidence along with the accompanying modeling has demonstrated that magnetospheric substorms are an important acceleration component within the coupled near-Earth system.

  4. The earth's magnetosphere. [as astrophysical plasma laboratory

    NASA Technical Reports Server (NTRS)

    Roederer, J. G.

    1974-01-01

    A qualitative description of the general magnetospheric configuration is given, with emphasis on some of the physical processes governing the magnetosphere that are the main targets of current research. The magnetosphere behaves like a huge 'bag' of plasma and radiation that swells and contracts under the influence of the solar wind. The electric field, the magnetospheric plasma, the magnetospheric substorm, and the radiation belt and wave particle interactions are discussed. During the past 15 years, the study of the earth's magnetosphere man's immediate plasma and radiation environment - has undergone a successful stage of discovery and exploration. Investigators have obtained a morphological description of the magnetospheric field, the particle population embedded in it, and its interface with the solar wind, and have identified and are beginning to understand many of the physical processes involved. Quite generally, the magnetosphere reveals itself as a region where it is possible to observe some of the fundamental plasma processes at work that are known to occur elsewhere in the universe.

  5. Continuous Lobe Reconnection in the Mid-Tail: Observational Signatures and Relation to Substorm onset

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Pu, Z.; Cao, X.; Xiao, C.; Fu, S.

    2004-12-01

    Magnetospheric substorms represent a global interaction between the solar wind, the magnetosphere, and the ionosphere. Energy extracted from the solar wind is mainly stored in the form of excess magnetic flux in the magnetotail lobes. There is little doubt that reconnection occurs in the magnetotail at some point during substorms. However, whether or not explosive release of this energy is required to cause the substorm and whether reconnection precedes or succeeds expansion onset are still subjects of big debate and controversy. In past three years (2001-2003) Cluster constellation passed through the plasma sheet more than one hundred times. Base on survey of the three yearAƒÆ'A+â_TAƒâ_sA,AøAƒÆ'A,AøAƒAøAøâ_sA¬A.A¡Aƒâ_sA,A¬AƒÆ'A,AøAƒAøAøâ_sA¬A.A_Aƒâ_sA,Aøs four spacecraft data, we have selected 39 continues lobe reconnection (CLR) events. A careful study of these events indicates that the CLR and plasma sheet closed field line reconnection manifest quite differently. The CLR occurs when the IMF is persistently southward (say, for more than a few tens of minutes) and maintains for more than about 20 minutes. It creates a low-density and low-temperature structure with high-speed plasma flows near the central plasma sheet. Quite often the CLRs appear quasi-periodically and in association with the presence of a magnetic storm. Comprehensive investigations have been made in this paper on the relationship between the occurrence of CLRs in the mid-tail and the substorm onsets in the near-Earth region. The 39 CLRs are all found to be corresponding to the appearance of intense substorms. In 37 events the CLRs precede substorms expansion onsets, while other two are opposite. These suggest that tail lobe unloading via CLR is a critical issue for the expansion onset of substorms occurring in persistently southward IMF periods. Nevertheless, this study does not exclude that substorms of other types may have different causes and that dynamical

  6. Dynamics of the outer radiation belts in relation to polar substorms and hot plasma injections at geostationary altitude

    NASA Technical Reports Server (NTRS)

    Sauvaud, J. A.; Winckler, J. R.

    1981-01-01

    Geostationary satellite and ground measurements of dynamic variations of the outer radiation belts and their relations with the development of auroral structures during magnetospheric substorms are analyzed. A comparison of measurements of the H or X geomagnetic field components made by seven auroral stations with ATS-6 low-energy and high-energy particle measurements during the multiple-onset substorm of Aug. 16, 1974 is presented which demonstrates that while the decrease in energetic particle fluxed ends only at the time of a strong substorm onset, rapid motions of the outer radiation belts may occur during the flux decrease. All-sky photographs of auroral phenomena taken at Fort Yukon and College, Alaska are then compared with ATS-1 energetic particle flux measurements in order to demonstrate the relation between flux decreases and increases and distinct substorm phases. Results support the hypothesis of a magnetospheric substorm precursor which appears to be an instability growing at the inner boundary of the plasma layer and approaching the earth, and underline the importance of current and magnetic field variations in charged particle dynamics.

  7. Can X-ray bursts be caused by substorms at a neutron star

    NASA Technical Reports Server (NTRS)

    Neugebauer, M.; Tsurutani, B. T.

    1978-01-01

    A model for X-ray bursts from accreting neutron stars is developed by analogy with geomagnetic substorms. The essential steps in the substorm process are the nearly steady merging or reconnection of the magnetic field in the magnetosphere with the field in the stellar wind, the transport of some of the merged plasma into a magnetically controlled tail, and the explosive release of plasma from the tail into the magnetosphere. The strength of the magnetic field in the stellar wind required to drive a substorm is approximately 0.1 gauss. If the stellar wind is organized into large-scale magnetic sectors, as is the solar wind, topological dissipation will not occur, and the large-scale field will be available for merging at the magnetopause. Once the material is in the tail, the time scales for the Kruskal-Schwarzschild instability and the unidentified instability which drives terrestrial substorms may be comparable. Alternating periods of burst activity and quiescence could be caused by passage from one sector to another with opposite polarity, or be seasonal variations.

  8. The three dimensional current system during substorms

    NASA Astrophysics Data System (ADS)

    Gjerloev, Jesper; Hoffman, Robert

    2013-04-01

    We present results from a comprehensive statistical study of the ionospheric current system and it's coupling to the magnetosphere during classical bulge type substorms. We identified 116 substorms and determined the global ionospheric current system before and during the substorm using the SuperMAG initiative and global auroral images obtained by the Polar VIS Earth camera. The westward electrojet (WEJ) is centered around 65 / 72 deg magnetic latitude post-midnight / pre-midnight. Thus, we find a distinct latitudinal shift between the locations of the westward electrojet at these local times. The spatiotemporal behavior of the WEJ differs at these two local times. Attempting to explain this significant finding we propose two possible simple current systems. 1) The classical substorm current wedge, which is a single 3D current system. The distinct poleward kink and the different spatiotemporal behavior, however, present considerable complications for this solution. 2) A new 3D current system that consists of 2 wedge type systems: the classical substorm current wedge in the pre-midnight region and another current wedge in the post-midnight region. The latter maps to the inner magnetosphere. To support the empirical modeling we performed Biot and Savart integrations to simulate the ground perturbations. We present results of the statistical study, show typical events, results from the simulations, and discuss the implications for our understanding of the 3D current system associated with substorms.

  9. Auroral substorms

    NASA Astrophysics Data System (ADS)

    Heikkila, Walter J.

    Many models of the substorm process assume a uniform current sheet before the auroral breakup and the onset of the expansion phase; in fact, a lower energy state for the cross-tail current is a set of filamentary currents. We hypothesize that such filaments are connected to auroral arcs during the growth phase. We must have an arc for it to break up, an essential part of the substorm. This means that we should look at instabilities of current filaments in the magnetotail. We have proposed that the appropriate instability is a simple meander of the current filament in the equatorial plane. An outward meander will be caused by the current carriers, undergoing curvature drift, becoming demagnetized. We take the inductive electric field as EIND = -∂A/∂t, using the Coulomb or transverse gauge. This inductive electric field will in general have a component parallel to the magnetic field. We take the response of the plasma to be reflected in a scalar potential, EES = - ∇ φ that response must be such as to diminish the actual (or net) E∥ Part of the response is the formation of field-aligned currents producing the well-known substorm current diversion. At the same time the plasma will enhance the transverse component of the induction electric field. Other work has indicated that a substorm reconnection X-line will form. The enhanced induction electric field near the emerging X-line will cause a discharge, again to decrease E∥ After subsequent betatron acceleration even zero energy particles can be energized to MeV energies in a matter of seconds in a two-step process. A plasmoid will be created which will move in the direction of least magnetic pressure, namely tailward.

  10. An Analysis of Conjugate Ground-based and Space-based Measurements of Energetic Electrons during Substorms

    NASA Astrophysics Data System (ADS)

    Sivadas, N.; Semeter, J. L.

    2015-12-01

    Substorms within the Earth's magnetosphere release energy in the form of energetic charged particles and several kinds of waves within the plasma. Depending on their strength, satellite-based navigation and communication systems are adversely affected by the energetic charged particles. Like many other natural phenomena, substorms can have a severe economic impact on a technology-driven society such as ours. Though energization of charged particles is known to occur in the magnetosphere during substorms, the source of this population and its relation to traditional acceleration region dynamics, are not completely understood. Combining measurements of energetic charged particles within the plasmasheet and that of charged particles precipitated in to the ionosphere will provide a better understanding of the role of processes that accelerate these charged particles. In the current work, we present energetic electron flux measured indirectly using data from ground-based Incoherent Scatter Radar and that measured directly at the plasmasheet by the THEMIS spacecraft. Instances of low-altitude-precipitation observed from ground suggest electrons of energy greater than 300 keV, possibly arising from particle injection events during substorms at the magnetically conjugate locations in the plasmasheet. The differences and similarities in the measurements at the plasmasheet and the ionosphere indicate the role different processes play in influencing the journey of these energetic particles form the magnetosphere to the ionosphere. Our observations suggest that there is a lot more to be understood of the link between magnetotail dynamics and energetic electron precipitation during substorms. Understanding this may open up novel and potentially invaluable ways of diagnosing the magnetosphere from the ground.

  11. Observations in the vicinity of substorm onset: Implications for the substrom process

    NASA Technical Reports Server (NTRS)

    Elphinstone, R. D.; Hearn, D. J.; Cogger, L. L.; Murphree, J. S.; Singer, H.; Sergeev, V.; Mursula, K.; Klumpar, D. M.; Reeves, G. D.; Johnson, M.

    1995-01-01

    Multi-instrument data sets from the ground and satellites at both low and high altitude have provided new results concerning substorm onset and its source region in the magnetosphere. Twenty-six out of 37 substorm onset events showed evidence of azimuthally spaced auroral forms (AAFs) prior to the explosive poleward motion associated with optical substorm onset. AAFs can span 8 hours of local time prior to onset and generally propagate eastward in the morning sector. Onset itself is, however, more localized spanning only about 1 hour local time. AAF onset occur during time periods when the solar wind pressure is relatively high. AAFs brighten in conjunction with substorm onset leading to the conclusion that they are a growth phase activity casually related to substorm onset. Precursor activity associated with these AAFs is also seen near geosynchronous orbit altitude and examples show the relationship between the various instrumental definitions of substorm onset. The implied mode number (30 to 135) derived from this work is inconsistent with cavity mode resonances but is consistent with a modified flute/ballooning instability which requires azimuthal pressure gradients. The extended source region and the distance to the open-closed field line region constrain reconnection theory and local mechanisms for substorm onset. It is demonstrated that multiple onset substorms can exist for which localized dipolarizations and the Pi 2 occur simultaneously with tail stretching existing elsewhere. These pseudobreakups can be initiated by auroral streamers which originate at the most poleward set of arc systems and drift to the more equatorward main UV oval. Observations are presented of these AAFs in conjunction with low- and high-altitutde particle and magnetic field data. These place the activations at the interface between dipolar and taillike field lines probably near the peak in the cross-tail current. These onsets are put in the context of a new scenario for substorm

  12. Saw-tooth substorms: Inconsistency of repetitive bay-like magnetic disturbances with behavior of aurora

    NASA Astrophysics Data System (ADS)

    Troshichev, O.; Stauning, P.; Liou, K.; Reeves, G.

    2011-02-01

    The relationships between the magnetic disturbance onsets, aurora dynamics and particles injections at the geostationary orbit have been analyzed in detail for 25 sawtooth substorms. It is shown that inconsistency between the above signatures of the substorms onset is typical of the powerful sawtooth substorms, unlike the isolated (“classical”) magnetospheric substorms. The distinguishing feature of the aurora in case of saw-tooth substorms is permanently high level of auroral activity irrespective of the magnetic disturbance onsets and the double oval structure of the aurora display. The close relationship between the aurora behavior and the particle injections at geostationary orbit is also broken. The conclusion is made, that the classical concept of the substorm development, put forward by Akasofu (1964) for isolated substorms, is not workable in cases of the sawtooth disturbances, when the powerful solar wind energy pumping into the magnetosphere provides a permanent powerful aurora particle precipitation into the auroral zone.

  13. Response of the Earth's Magnetosphere to Changes in the Solar Wind

    NASA Technical Reports Server (NTRS)

    McPherron, Robert L.; Weygand, James M.; Hsu, Tung-Shin

    2007-01-01

    The solar wind couples to the magnetosphere via dynamic pressure and electric field. Pressure establishes the size and shape of the system, while the electric field transfers energy, mass, and momentum to the magnetosphere. When the interplanetary magnetic field (IMF) is antiparallel to the dayside magnetic field, magnetic reconnection connects the IMF to the dipole field. Solar wind transport of the newly opened field lines to the nightside creates an internal convection system. These open field lines must ultimately be closed by reconnection on the nightside. For many decades, it was thought that a magnetospheric substorm was the process for accomplishing this and that all magnetic activity was a consequence of substorms. It is now recognized that there are a variety of modes of response of the magnetosphere to the solar wind. In this paper, we briefly describe these modes and the conditions under which they occur. They include substorms, pseudo-breakups, poleward boundary intensifications (PBI), steady magnetospheric convection (SMC), sawtooth injection events, magnetic storms, high-intensity long-duration continuous AE activities (HILDCAAs), and storm-time activations. There are numerous explanations for these different phenomena, some of which do not involve magnetic reconnection. However, we speculate that it is possible to interpret each mode in terms of differences in the way magnetic reconnection occurs on the nightside.

  14. Response of the Earth's Magnetosphere to Changes in the Solar Wind

    NASA Technical Reports Server (NTRS)

    McPherron, Robert L.; Weygand, James M.; Hsu, Tung-Shin

    2007-01-01

    The solar wind couples to the magnetosphere via dynamic pressure and electric field. Pressure establishes the size and shape of the system, while the electric field transfers energy, mass, and momentum to the magnetosphere. When the interplanetary magnetic field (IMF) is antiparallel to the dayside magnetic field, magnetic reconnection connects the IMF to the dipole field. Solar wind transport of the newly opened field lines to the nightside creates an internal convection system. These open field lines must ultimately be closed by reconnection on the nightside. For many decades, it was thought that a magnetospheric substorm was the process for accomplishing this and that all magnetic activity was a consequence of substorms. It is now recognized that there are a variety of modes of response of the magnetosphere to the solar wind. In this paper, we briefly describe these modes and the conditions under which they occur. They include substorms, pseudo-breakups, poleward boundary intensifications (PBI), steady magnetospheric convection (SMC), sawtooth injection events, magnetic storms, high-intensity long-duration continuous AE activities (HILDCAAs), and storm-time activations. There are numerous explanations for these different phenomena, some of which do not involve magnetic reconnection. However, we speculate that it is possible to interpret each mode in terms of differences in the way magnetic reconnection occurs on the nightside.

  15. Energetic particles of the outer regions of planetary magnetospheres

    NASA Technical Reports Server (NTRS)

    Tsurutani, B. T.; Goldstein, B. E.; Bratenahl, A.

    1976-01-01

    High energy particles, with energies above those attainable by adiabatic or steady-state electric field acceleration, have been observed in and around the outer regions of planetary magnetospheres. Acceleration by large amplitude sporadic cross-tail electric fields over an order of magnitude greater than steady-state convection fields is proposed as a source of these particles. It is suggested that such explosive electric fields will occur intermittently in the vicinity of the tail neutral line in the expansive phase of substorms. Laboratory and satellite evidence are used to estimate this electric potential for substorms at earth; values of 500 kilovolts to 2 megavolts are calculated, in agreement with particle observations. It is further suggested that these particles, which have been accelerated in the night side magnetosphere, drift to the dayside on closed field lines, and under certain interplanetary conditions can escape to regions upstream of the bow shock.

  16. Interaction of Substorm Injections with the Subauroral Geospace

    NASA Astrophysics Data System (ADS)

    Mishin, E. V.

    2013-12-01

    The subauroral geospace includes the ring current (RC), innermost part of the outer radiation belt, and plasmasphere adjacent to the electron plasma sheet boundary and conjugate ionosphere. The purpose of this paper is to extend understanding of the active subauroral geospace by exploring subauroral events in the near-equatorial magnetosphere and conjugate ionosphere soon after the onsets of individual substorms. Their fast appearance is consistent with the propagation of substorm injections. The documented features in the premidnight sector are described in terms of the effect of a short circuit of substorm-injected plasma jets over the plasmapause. The short-circuiting occurs when the cold plasma density exceeds a critical value of 5-10 c.c. As the polarization field at the front of the hot plasma jet is shorten out, the hot electrons are arrested, while the hot ions yet move inward. This provides a natural explanation of the long-known dispersionless auroral electron precipitation boundary and the SAID location just interior to the plasmapause. Enhanced plasma turbulence provides anomalous circuit resistivity and magnetic diffusion leading to a turbulent boundary layer adjacent to the plasmapause. The hot ions' inward motion stops when their pressure gradient is balanced by the polarization electric field. Then, the ions experiencing gradient-curvature drift move westward and their interaction with the plasmasphere creates strong wave structures on the duskside.

  17. 3D PIC Simulation of the Magnetosphere during IMF Rotation from North to South: Signatures of Substorm Triggering in the Magnetotail

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi; Cao. D/ S/; Lembege, B.

    2008-01-01

    Three dimensional PIC simulations are performed in order to analyse the dynamics of the magnetotail as the interplanetary magnetic field (IMF) rotates from northward to southward direction. This dynamics reveals to be quite different within meridian/equatorial planes over two successive phases of this rotation. First, as IMF rotates from North to Dawn-Dusk direction, the X-Point (magnetic reconnection) evidenced in the magnetotail (meridian plane) is moving earthward (from x=-35 Re to x=-17.5 ) distance at which it stabilizes. This motion is coupled with the formation of "Crosstail-S" patterns (within the plane perpendicular to the Sun-Earth mine) through the neutral sheet in the nearby magnetotail. Second, as IMF rotates from dawn-dusk to South, the minimum B field region is expanding within the equatorial plane and forms a ring. This two-steps dynamics is analyzed in strong association with the cross field magnetotail current Jy, in order to recover the signatures of substorms triggering.

  18. 3D PIC Simulation of the Magnetosphere during IMF Rotation from North to South: Signatures of Substorm Triggering in the Magnetotail

    NASA Technical Reports Server (NTRS)

    Nishikawa, Ken-Ichi; Cao. D/ S/; Lembege, B.

    2008-01-01

    Three dimensional PIC simulations are performed in order to analyse the dynamics of the magnetotail as the interplanetary magnetic field (IMF) rotates from northward to southward direction. This dynamics reveals to be quite different within meridian/equatorial planes over two successive phases of this rotation. First, as IMF rotates from North to Dawn-Dusk direction, the X-Point (magnetic reconnection) evidenced in the magnetotail (meridian plane) is moving earthward (from x=-35 Re to x=-17.5 ) distance at which it stabilizes. This motion is coupled with the formation of "Crosstail-S" patterns (within the plane perpendicular to the Sun-Earth mine) through the neutral sheet in the nearby magnetotail. Second, as IMF rotates from dawn-dusk to South, the minimum B field region is expanding within the equatorial plane and forms a ring. This two-steps dynamics is analyzed in strong association with the cross field magnetotail current Jy, in order to recover the signatures of substorms triggering.

  19. Substorm evolution of auroral structures

    NASA Astrophysics Data System (ADS)

    Partamies, N.; Juusola, L.; Whiter, D.; Kauristie, K.

    2015-07-01

    Auroral arcs are often associated with magnetically quiet time and substorm growth phases. We have studied the evolution of auroral structures during global and local magnetic activity to investigate the occurrence rate of auroral arcs during different levels of magnetic activity. The ground-magnetic and auroral conditions are described by the magnetometer and auroral camera data from five Magnetometers — Ionospheric radars — All-sky cameras Large Experiment stations in Finnish and Swedish Lapland. We identified substorm growth, expansion, and recovery phases from the local electrojet index (IL) in 1996-2007 and analyzed the auroral structures during the different phases. Auroral structures were also analyzed during different global magnetic activity levels, as described by the planetary Kp index. The distribution of auroral structures for all substorm phases and Kp levels is of similar shape. About one third of all detected structures are auroral arcs. This suggests that auroral arcs occur in all conditions as the main element of the aurora. The most arc-dominated substorm phases occur in the premidnight sector, while the least arc-dominated substorm phases take place in the dawn sector. Arc event lifetimes and expectation times calculated for different substorm phases show that the longest arc-dominated periods are found during growth phases, while the longest arc waiting times occur during expansion phases. Most of the arc events end when arcs evolve to more complex structures. This is true for all substorm phases. Based on the number of images of auroral arcs and the durations of substorm phases, we conclude that a randomly selected auroral arc most likely belongs to a substorm expansion phase. A small time delay, of the order of a minute, is observed between the magnetic signature of the substorm onset (i.e., the beginning of the negative bay) and the auroral breakup (i.e., the growth phase arc changing into a dynamic display). The magnetic onset was

  20. Strong induction effects during the substorm on 27 August 2001

    NASA Astrophysics Data System (ADS)

    Mishin, V. V.; Mishin, V. M.; Lunyushkin, S. B.; Pu, Z.; Wang, C.

    2015-10-01

    We report on strong induction effects notably contributing to the cross polar cap potential drop and the energy balance during the growth and active phases of the substorm on 27 August 2001. The inductance of the magnetosphere is found to be crucial for the energy balance and electrical features of the magnetosphere in the course of the substorm. The inductive response to the switching on and off of the solar wind-magnetosphere generator exceeds the effect of the interplanetary magnetic field (IMF) variation. The induction effects are most apparent during the substorm expansion onset when the rapid growth of the ionospheric conductivity is accompanied by the fast release of the magnetic energy stored in the magnetotail during the growth phase. Using the magnetogram inversion technique, we estimated the magnetospheric inductance and effective ionospheric conductivity during the loading and unloading phases.

  1. Substorm probabilities are best predicted from solar wind speed

    NASA Astrophysics Data System (ADS)

    Newell, P. T.; Liou, K.; Gjerloev, J. W.; Sotirelis, T.; Wing, S.; Mitchell, E. J.

    2016-08-01

    Most measures of magnetospheric activity - including auroral power (AP), magnetotail stretching, and ring current intensity - are best predicted by solar wind-magnetosphere coupling functions which approximate the frontside magnetopause merging rate. However radiation belt fluxes are best predicted by a simpler function, namely the solar wind speed, v. Since most theories of how these high energy electrons arise are associated with repeated rapid dipolarizations such as associated with substorms, this apparent discrepancy could be reconciled under the hypothesis that the frequency of substorms tracks v rather than the merging rate - despite the necessity of magnetotail flux loading prior to substorms. Here we investigate this conjecture about v and substorm probability. Specifically, a continuous list of substorm onsets compiled from SuperMAG covering January 1, 1997 through December 31, 2007 are studied. The continuity of SuperMAG data and near continuity of solar wind measurements minimize selection bias. In fact v is a much better predictor of onset probability than is the overall merging rate, with substorm odds rising sharply with v. Some loading by merging is necessary, and frontside merging does increase substorm probability, but nearly as strongly as does v taken alone. Likewise, the effects of dynamic pressure, p, are smaller than simply v taken by itself. Changes in the solar wind matter, albeit modestly. For a given level of v (or Bz), a change in v (or Bz) will increase the odds of a substorm for at least 2 h following the change. A decrease in driving elevates substorm probabilities to a greater extent than does an increase, partially supporting external triggering. Yet current v is the best single predictor of subsequently observing a substorm. These results explain why geomagnetically quiet years and active years are better characterized by low or high v (respectively) than by the distribution of merging estimators. It appears that the flow of energy

  2. Magnetosphere-Regolith/Exosphere Coupling: Differences and Similarities to the Earth Magnetosphere-Ionosphere Coupling

    NASA Technical Reports Server (NTRS)

    Gjerleov, J. W.; Slavin, J. A.

    2001-01-01

    Of the three Mercury passes made by Mariner 10, the first and third went through the Mercury magnetosphere. The third encounter which occurred during northward IMF (interplanetary magnetic field) showed quiet time magnetic fields. In contrast the third encounter observed clear substorm signatures including dipolarization, field-aligned currents (FACs) and injection of energetic electrons at geosynchronous orbit. However, the determined cross-tail potential drop and the assumed height integrated conductance indicate that the FAC should be 2-50 times weaker than observed. We address this inconsistency and the fundamental problem of FAC closure whether this takes place in the regolith or in the exosphere. The current state of knowledge of the magnetosphere-exosphere/regolith coupling is addressed and similarities and differences to the Earth magnetosphere-ionosphere coupling are discussed.

  3. Tests of Substorm Models' Predictions Using ISTP Observations

    NASA Technical Reports Server (NTRS)

    Sanchez, Ennio R.

    1998-01-01

    This report provides progress to test the predictions of substorm models using ISTP observations. During the first year, two investigations were initiated in collaboration with a number of ISTP researchers. Both investigations use a combination of simultaneous measurements from high-, low-, and ground-altitude instruments to: (1) explore the role of MHD resonances in the onset and evolution of substorms, and (2) establish the timing of events in the magnetosphere and ionosphere during the substorm evolution beginning with the growth phase and ending with the recovery phase.

  4. Magnetic substorms and northward IMF turning

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Podorozhkina, Nataly

    To determine the relation of the northward IMF turnings to substorm sudden onsets, we separated all events with sharp northward IMF turnings observed in years of solar maximum (1999-2002) and solar minimum (2007-2008). The events (N=261) have been classified in 5 groups in accordance with average magnetic activity in auroral zone (low, moderate or high levels of AL index) at unchanged or slightly changed PC index and with dynamics of PC (steady distinct growth or distinct decline) at arbitrary values of AL index. Statistical analysis of relationships between the IMF turning and changes of PC and AL indices has been fulfilled separately for each of 5 classes. Results of the analysis showed that, irrespective of geophysical conditions and solar activity epoch, the magnetic activity in the polar caps and in the auroral zone demonstrate no response to the sudden northward IMF turning, if the moment of northward turning is taken as a key date. Sharp increases of magnetic disturbance in the auroral zone are observed only under conditions of the growing PC index and statistically they are related to moment of the PC index exceeding the threshold level (~1.5 mV/m), not to northward turnings timed, as a rule, after the moment of sudden onset. Magnetic disturbances observed in these cases in the auroral zone (magnetic substorms) are guided by behavior of the PC index, like to ordinary magnetic substorms or substorms developed under conditions of the prolonged northward IMF impact on the magnetosphere. The evident inconsistency between the sharp IMF changes measured outside of the magnetosphere and behavior of the ground-based PC index, the latter determining the substorm development, provides an additional argument in favor of the PC index as a ground-based proxy of the solar wind energy that entered into magnetosphere.

  5. Special Issue the 12th International Conference on Substorms

    NASA Technical Reports Server (NTRS)

    Shiokawa, Kazuo; Fok, Mei-Ching; Fujimoto, Masaki

    2016-01-01

    The 12th International Conference on Substorms (ICS-12) was held at the Ise-Shima Royal Hotel in Shima, Japan, on November 10-14, 2014. There were 125 attendees including 68 from foreign countries. The ICS has been held every 2 years since 1992 to discuss substorms, which are fundamental global-scale disturbances in the Earth's magnetosphere. The year 2014 marked the 50th anniversary of the first publication about substorms (Akasofu 1964). The conference included three tutorial lecturers (Profs. S.-I. Akasofu, V. Angelopoulous, and D. Baker), as well as many international scientists, to discuss substorm processes in the tail, their Interactions with the inner magnetosphere and the ionosphere, substorm currents and their dynamics and energetics, the role of MagnetoHydroDynamics (MHD) and kinetic instabilities, storm-substorm relationships, ULFELFVLF waves, and non-Earth substorm-like features. Prof. Akasofu also gave an evening talk about the history of auroral research since the nineteenth century with photographs that inspired and intrigued the young scientists and students in attendance.

  6. Extremely intense (SML ≤-2500 nT) substorms: isolated events that are externally triggered?

    NASA Astrophysics Data System (ADS)

    Tsurutani, B. T.; Hajra, R.; Echer, E.; Gjerloev, J. W.

    2015-05-01

    We examine particularly intense substorms (SML ≤-2500 nT), hereafter called "supersubstorms" or SSS events, to identify their nature and their magnetic storm dependences. It is found that these intense substorms are typically isolated events and are only loosely related to magnetic storms. SSS events can occur during super (Dst ≤-250 nT) and intense (-100 nT ≥ Dst >-250) magnetic storms. SSS events can also occur during nonstorm (Dst ≥-50 nT) intervals. SSSs are important because the strongest ionospheric currents will flow during these events, potentially causing power outages on Earth. Several SSS examples are shown. SSS events appear to be externally triggered by small regions of very high density (~30 to 50 cm-3) solar wind plasma parcels (PPs) impinging upon the magnetosphere. Precursor southward interplanetary magnetic fields are detected prior to the PPs hitting the magnetosphere. Our hypothesis is that these southward fields input energy into the magnetosphere/magnetotail and the PPs trigger the release of the stored energy.

  7. Dynamics of the 1054 UT March 22, 1979, substorm event - CDAW 6. [Coordinated Data Analysis Workshop

    NASA Technical Reports Server (NTRS)

    Mcpherron, R. L.; Manka, R. H.

    1985-01-01

    The Coordinated Data Analysis Workshop (CDAW 6) has the primary objective to trace the flow of energy from the solar wind through the magnetosphere to its ultimate dissipation in the ionosphere. An essential role in this energy transfer is played by magnetospheric substorms, however, details are not yet completely understood. The International Magnetospheric Study (IMS) has provided an ideal data base for the study conducted by CDAW 6. The present investigation is concerned with the 1054 UT March 22, 1979, substorm event, which had been selected for detailed examination in connection with the studies performed by the CDAW 6. The observations of this substorm are discussed, taking into account solar wind conditions, ground magnetic activity on March 22, 1979, observations at synchronous orbit, observations in the near geomagnetic tail, and the onset of the 1054 UT expansion phase. Substorm development and magnetospheric dynamics are discussed on the basis of a synthesis of the observations.

  8. The Cross-field Current Instability for Substorm Expansion Onset

    SciTech Connect

    Lui, A. T. Y.

    2011-01-04

    A challenging problem in the topic of the nonlinear dynamics of the magnetosphere is the physical process responsible for the onset of magnetospheric substorms. The early collaboration with Dr. K. Papadopoulos has led to the proposal of a kinetic plasma instability, called the cross-field current instability, as the onset process. This has developed into a full-blown research effort, supplementing the initial theoretical analysis with in-depth data analysis and particle simulations. Several theoretical predictions based on this instability are successfully verified in observations. Data from the present NASA THEMIS mission provide some evidence for its validity. Further investigations for this substorm onset process are also discussed.

  9. Solar cycle dependence of substorm occurrence and duration: Implications for onset

    NASA Astrophysics Data System (ADS)

    Chu, Xiangning; McPherron, Robert L.; Hsu, Tung-Shin; Angelopoulos, Vassilis

    2015-04-01

    Magnetospheric substorms represent a major energy release process in Earth's magnetosphere. Their duration and intensity are coupled to solar wind input, but the precise way the solar wind energy is stored and then released is a matter of considerable debate. Part of the observational difficulty has been the gaps in the auroral electrojet index traditionally used to study substorm properties. In this study, we created a midlatitude positive bay (MPB) index to measure the strength of the substorm current wedge. Because this index is based on midlatitude magnetometer data that are available continuously over several decades, we can assemble a database of substorm onsets lasting 31 years (1982-2012). We confirmed that the MPB onsets have a good agreement (±2 min) with auroral onsets as determined by optical means on board the IMAGE mission and that the MPB signature of substorms is robust and independent of the stations' position relative to ionospheric currents. Using the MPB onset, expansion, and recovery as a proxy of the respective substorm quantities, we found that the solar cycle variation of substorm occurrence depends on solar wind conditions and has a most probable value of 80 min. In contrast, the durations of substorm expansion and recovery phases do not change with the solar cycle. This suggests that the frequency of energy unloading in the magnetosphere is controlled by solar wind conditions through dayside reconnection, but the unloading process related to flux pileup in the near-Earth region is controlled by the magnetosphere and independent of external driving.

  10. Theory of substorm onset and dipolarization

    NASA Astrophysics Data System (ADS)

    Cheng, C. Z.; Zaharia, S.

    2003-04-01

    We present a theory of substorm onset and dipolarization. At the end of the substorm growth phase, the plasma pressure profile steepens and a thin current sheet is formed in the near-Earth plasma sheet around the local midnight with a finite radial and azimuthal domain. In the current sheet the plasma beta becomes about 50 or larger and magnetic field curvature is enhanced, and the kinetic ballooning instability (KBI) is excited with amplitude localized at the maximum plasma beta region. The KBI explains the low frequency (about 1 min period) instability observed by AMPTE/CCE with period on the order of 1 min is observed about 2-3 minutes before the substorm onset [Cheng and Lui, GRL, 1998]. The KBI is responsible for substorm onset because as it grows to a large amplitude with Δ B/B > 01, it causes an enhanced westward ion drift during the explosive growth phase that lasts about 30 sec. The KBI then excites higher frequency instabilities, and the plasma and magnetic field become strongly turbulent. The plasma transport in both radial and azimuthal direction caused by the turbulence relaxes the steep plasma pressure profile during the expansion phase. As the plasma pressure profile relaxes, the magnetic field configuration dipolarizes and returns to the pre-substorm more dipole-like geometry. Theories of current sheet formation, KBI mechanism and dipolarization will be presented along with numerical solutions of 3D magnetospheric structure.

  11. A case study of lightning, whistlers, and associated ionospheric effects during a substorm particle injection event

    NASA Technical Reports Server (NTRS)

    Rodriguez, J. V.; Inan, U. S.; Li, Y. Q.; Holzworth, R. H.; Smith, A. J.; Orville, R. E.; Rosenberg, T. J.

    1992-01-01

    The relationships among cloud-to-ground (CG) lightning, sferics, whistlers, VLF amplitude perturbations, and other ionospheric phenomena occurring during substorm events were investigated using data from simultaneous ground-based observations of narrow-band and broad-band VLF radio waves and of CG lightning made during the 1987 Wave-Induced Particle Precipitation campaign conducted from Wallops Island (Virginia). Results suggest that the data collected on ionospheric phenomena during this event may represent new evidence of direct coupling of lightning energy to the lower ionosphere, either in conjunction with or in the absence of gyroresonant interactions between whistler mode waves and electrons in the magnetosphere.

  12. Comparing and contrasting dispersionless injections at geosynchronous orbit during a substorm event

    NASA Astrophysics Data System (ADS)

    Kronberg, E. A.; Grigorenko, E. E.; Turner, D. L.; Daly, P. W.; Khotyaintsev, Y.; Kozak, L.

    2017-03-01

    Particle injections in the magnetosphere transport electrons and ions from the magnetotail to the radiation belts. Here we consider generation mechanisms of "dispersionless" injections, namely, those with simultaneous increase of the particle flux over a wide energy range. In this study we take advantage of multisatellite observations which simultaneously monitor Earth's magnetospheric dynamics from the tail toward the radiation belts during a substorm event. Dispersionless injections are associated with instabilities in the plasma sheet during the growth phase of the substorm, with a dipolarization front at the onset and with magnetic flux pileup during the expansion phase. They show different spatial spread and propagation characteristics. Injection associated with the dipolarization front is the most penetrating. At geosynchronous orbit (6.6 RE), the electron distributions do not have a classic power law fit but instead a bump on tail centered on ˜120 keV during dispersionless electron injections. However, electron distributions of injections associated with magnetic flux pileup in the magnetotail (13 RE) do not show such a signature. We surmise that an additional resonant acceleration occurs in between these locations. We relate the acceleration mechanism to the electron drift resonance with ultralow frequency waves localized in the inner magnetosphere.

  13. Comparing and contrasting dispersionless injections at geosynchronous orbit during a substorm event

    NASA Astrophysics Data System (ADS)

    Kronberg, Elena; Grigorenko, Elena; Turner, Drew; Daly, Patrick; Khotyaintsev, Yuri; Kozak, Liudmyla

    2017-04-01

    Particle injections in the magnetosphere transport electrons and ions from the magnetotail to the radiation belts. We consider generation mechanisms of ``dispersionless'' injections, namely those with simultaneous increase of the particle flux over a wide energy range. We take advantage of multi-satellite observations which simultaneously monitor Earth's magnetospheric dynamics from the tail towards the radiation belts during a substorm event. Dispersionless injections are associated with instabilities in the plasma sheet during the growth phase of the substorm, with a dipolarization front at the onset and with magnetic flux pileup during the expansion phase. They show different spatial spread and propagation characteristics. At geosynchronous orbit (6.6 RE), the electron distributions do not have a classic power law fit but instead a bump-on-tail centered on 120 keV during dispersionless electron injections. However, electron distributions of injections associated with magnetic flux pileup in the magnetotail (13 RE) do not show such a signature. We surmise that an additional resonant acceleration occurs in-between these locations. We relate the acceleration mechanism to the electron drift resonance with ultralow frequency (ULF) waves localized in the inner magnetosphere. This study is supported by the Volkswagen Foundation.

  14. Pressure changes in the plasma sheet during substorm injections

    NASA Technical Reports Server (NTRS)

    Kistler, L. M.; Moebius, E.; Baumjohann, W.; Paschmann, G.; Hamilton, D. C.

    1992-01-01

    Data from the CHEM instrument on AMPTE CCE, data from the 3D plasma instrument and the SULEICA instrument on AMPTE IRM, and magnetometer data from both spacecraft are used to determine the particle pressure and total pressure as a function of radial distance in the plasma sheet for periods before and after the onset of substorm-associated ion enhancements over the range 7-19 RE. Events were chosen that occurred during times of increasing magnetospheric activity, as determined by an increasing AE index, in which a sudden increase, or 'injection', of energetic particle flux is observed. It is shown that the simultaneous appearance of energetic particles and changes in the magnetic field results naturally from pressure balance and does not necessarily indicate that the local changing field is accelerating the particles.

  15. Temporal and spatial dynamics of the regions 1 and 2 Birkeland currents during substorms

    NASA Astrophysics Data System (ADS)

    Clausen, L. B. N.; Baker, J. B. H.; Ruohoniemi, J. M.; Milan, S. E.; Coxon, J. C.; Wing, S.; Ohtani, S.; Anderson, B. J.

    2013-06-01

    We use current density data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) to identify the location of maximum region 1 current at all magnetic local times (MLTs). We term this location the R1 oval. Comparing the R1 oval location with particle precipitation boundaries identified in DMSP data, we find that the R1 oval is located on average within 1° of particle signatures associated with the open/closed field line boundary (OCB) across dayside and nightside MLTs. We hence conclude that the R1 oval can be used as a proxy for the location of the OCB. Studying the amount of magnetic flux enclosed by the R1 oval during the substorm cycle, we find that the R1 oval flux is well organized by it: during the growth phase the R1 oval location moves equatorward as the amount of magnetic flux increases whereas after substorm expansion phase onset significant flux closure occurs as the R1 current location retreats to higher latitudes. For about 15 min after expansion phase onset, the amount of open magnetic flux continues to increase indicating that dayside reconnection dominates over nightside reconnection. In the current density data, we find evidence of the substorm current wedge and also show that the dayside R1 currents are stronger than their nightside counterpart during the substorm growth phase, whereas after expansion phase onset, the nightside R1 currents dominate. Our observations of the current distribution and OCB movement during the substorm cycle are in excellent agreement with the expanding/contracting polar cap paradigm.

  16. AMPERE observations of the Birkeland currents associated with substorms and comparison with simple electrodynamic modelling

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Coxon, J. C.; Clausen, L. B. N.; Korth, H.; Anderson, B. J.

    2014-04-01

    We present observations of the global terrestrial Birkeland field-aligned current (FAC) pattern observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during a sequence of substorms. The observations show that the region 1 and 2 current systems move to lower latitudes during the substorm growth phase and retreat to higher latitudes following substorm expansion phase onset. We interpret these observations within the framework of the expanding/contracting polar cap paradigm. This links expansion of the polar cap and equatorward motion of the auroras and FAC systems to the action of magnetopause reconnection increasing the open magnetic flux content of the magnetosphere.

  17. The Origin of the Near-Earth Plasma Population During a Substorm on November 24, 1996

    NASA Technical Reports Server (NTRS)

    Ashour-Abdalla, M.; El-Alaoui, M.; Peroomian, V.; Walker, R. J.; Raeder, J.; Frank, L. A.; Paterson, W. R.

    1999-01-01

    We investigate the origins and the transport of ions observed in the near-Earth plasma sheet during the growth and expansion phases of a magnetospheric substorm that occurred on November 24, 1996. Ions observed at Geotail were traced backward in time in time-dependent magnetic and electric fields to determine their origins and the acceleration mechanisms responsible for their energization. Results from this investigation indicate that, during the growth phase of the substorm, most of the ions reaching Geotail had origins in the low latitude boundary layer (LLBL) and had already entered the magnetosphere when the growth phase began. Late in the growth phase and in the expansion phase a higher proportion of the ions reaching Geotail had their origin in the plasma mantle. Indeed, during the expansion phase more than 90% of the ions seen by Geotail were from the mantle. The ions were accelerated enroute to the spacecraft; however, most of the ions' energy gain was achieved by non-adiabatic acceleration while crossing the equatorial current sheet just prior to their detection by Geotail. In general, the plasma mantle from both southern and northern hemispheres supplied non-adiabatic ions to Geotail, whereas the LLBL supplied mostly adiabatic ions to the distributions measured by the spacecraft. Distribution functions computed at the ion sources indicate that ionospheric ions reaching Geotail during the expansion phase were significantly heated. Plasma mantle source distributions indicated the presence of a high-latitude reconnection region that allowed ion entry into the magnetosphere when the IMF was northward. These ions reached Geotail during the expansion phase. Ions from the traditional plasma mantle had access to the spacecraft throughout the substorm.

  18. Periodic substorm activity in the geomagnetic tail

    NASA Technical Reports Server (NTRS)

    Huang, C. Y.; Eastman, T. E.; Frank, L. A.; Williams, D. J.

    1983-01-01

    On 19 May 1978 an anusual series of events is observed with the Quadrispherical LEPEDEA on board the ISEE-1 satellite in the Earth's geomagnetic tail. For 13 hours periodic bursts of both ions and electrons are seen in all the particle detectors on the spacecraft. On this day periodic activity is also seen on the ground, where multiple intensifications of the electrojets are observed. At the same time the latitudinal component of the interplanetary magnetic field shows a number of strong southward deflections. It is concluded that an extended period of substorm activity is occurring, which causes repeated thinnings and recoveries of the plasma sheet. These are detected by ISEE, which is situated in the plasma sheet boundary layer, as periodic dropouts and reappearances of the plasma. Comparisons of the observations at ISEE with those at IMP-8, which for a time is engulfed by the plasma sheet, indicate that the activity is relatively localized in spatial extent. For this series of events it is clear that a global approach to magnetospheric dynamics, e.g., reconnection, is inappropriate.

  19. On the dynamical development of the downward field-aligned current in the substorm current wedge

    SciTech Connect

    Pellinen, R.J.; Pulkkinen, T.I.; Huuskonen, A.

    1995-08-01

    We report observations of a substorm event on March 4, 1979, onset at 2236 UT, which confirm the participation of the upward accelerated ionospheric electrons in the substorm current wedge current during the first few minutes after the substorm onset. The slow ions do not contribute much to the downward current immediately after the substorm onset, whereas the precipitating magnetospheric electrons quickly set up the upward current. A scanning photometer was centrally placed at the center of the downward current during the event. The observations suggest that the current was mainly caused by cold ionospheric electrons. 27 refs., 8 figs.

  20. MESSENGER Observations of Substorm Activity at Mercury

    NASA Astrophysics Data System (ADS)

    Sun, W. J.; Slavin, J. A.; Fu, S.; Raines, J. M.; Zong, Q. G.; Poh, G.; Jia, X.; Sundberg, T.; Gershman, D. J.; Pu, Z.; Zurbuchen, T.; Shi, Q.

    2015-12-01

    MErcury Surface, Space ENviroment, GEochemistry, and Ranging (MESSENGER) magnetic field and plasma measurements taken during crossings of Mercury's magnetotail from 2011 to 2014 have been investigated for substorms. A number of events with clear Earth-like growth phase and expansion phase signatures were found. The thinning of the plasma sheet and the increase of magnetic field intensity in the lobe were observed during the growth phase and plasma sheet was observed to thicken during the expansion phase, which are similar to the observations at Earth. But the time scale of Mercury's substorm is only several minutes comparing with the several hours at Earth [Sun et al., 2015a]. Detailed analysis of magnetic field fluctuations during the substorm expansion phase have revealed low frequency plasma waves, e.g. Pi2-like pulsations. The By fluctuations accompanying substorm dipolarizations are consistent with pulses of field-aligned currents near the high latitude edge of the plasma sheet. Further study shows that they are near-circularly polarized electromagnetic waves, most likely Alfvén waves. Soon afterwards the plasma sheet thickened and MESSENGER detected a series of compressional waves. We have also discussed their possible sources [Sun et al., 2015b]. Sun, W.-J., J. A. Slavin, S. Y. Fu, et al. (2015a), MESSENGER observations of magnetospheric substorm activity in Mercury's near magnetotail. Geophys. Res. Lett., 42, 3692-3699. doi: 10.1002/2015GL064052.Sun, W.-J., J. A. Slavin, S. Y. Fu, et al. (2015b), MESSENGER observations of Alfvénic and compressional waves during Mercury's substorms. Geophys. Res. Lett., 42, in press. doi: 10.1002/ 2015GL065452.

  1. Inertial magnetic field reconnection and magnetospheric substorms.

    NASA Technical Reports Server (NTRS)

    Van Hoven, G.; Cross, M. A.

    1973-01-01

    We describe and calculate the growth rate of a magnetohydrodynamic neutral-sheet instability due to electron-inertia terms in the infinite-conductivity Ohm's law. The results are compared with an approximate Vlasov-equation calculation, and are shown to be particularly germane to the geomagnetic-tail instability.

  2. Magnetic reconnection during steady magnetospheric convection and other magnetospheric modes

    NASA Astrophysics Data System (ADS)

    Hubert, Benoit; Gérard, Jean-Claude; Milan, Steve E.; Cowley, Stanley W. H.

    2017-03-01

    We use remote sensing of the proton aurora with the IMAGE-FUV SI12 (Imager for Magnetopause to Aurora Global Exploration-Far Ultraviolet-Spectrographic Imaging at 121.8 nm) instrument and radar measurements of the ionospheric convection from the SuperDARN (Super Dual Aurora Radar Network) facility to estimate the open magnetic flux in the Earth's magnetosphere and the reconnection rates at the dayside magnetopause and in the magnetotail during intervals of steady magnetospheric convection (SMC). We find that SMC intervals occur with relatively high open magnetic flux (average ˜ 0.745 GWb, standard deviation ˜ 0.16 GWb), which is often found to be nearly steady, when the magnetic flux opening and closure rates approximately balance around 55 kV on average, with a standard deviation of 21 kV. We find that the residence timescale of open magnetic flux, defined as the ratio between the open magnetospheric flux and the flux closure rate, is roughly 4 h during SMCs. Interestingly, this number is approximately what can be deduced from the discussion of the length of the tail published by Dungey (1965), assuming a solar wind speed of ˜ 450 km s-1. We also infer an enhanced convection velocity in the tail, driving open magnetic flux to the nightside reconnection site. We compare our results with previously published studies in order to identify different magnetospheric modes. These are ordered by increasing open magnetic flux and reconnection rate as quiet conditions, SMCs, substorms (with an important overlap between these last two) and sawtooth intervals.

  3. SAPS onset timing during substorms and the westward traveling surge

    NASA Astrophysics Data System (ADS)

    Mishin, Evgeny, V.

    2016-07-01

    We present multispacecraft observations in the magnetosphere and conjugate ionosphere of the onset time of subauroral polarization streams (SAPS) and tens of keV ring current injections on the duskside in three individual substorms. This is probably the first unequivocal determination of the substorm SAPS onset timing. The time lag between the SAPS and substorm onsets is much shorter than the gradient-curvature drift time of ˜10 keV ions in the plasmasphere. It seemingly depends on the propagation time of substorm-injected plasma from the dipolarization onset region to the plasmasphere, as well as on the SAPS position. These observations suggest that fast onset SAPS and ring current injections are causally related to the two-loop system of the westward traveling surge.

  4. Evolution of magnetic configurations in the plasma sheet during a substorm on March 19, 1978

    SciTech Connect

    Sun, W.; Kan, J.R.; Akasofu, S.I. )

    1991-09-01

    Evolution of the magnetic field configuration in the plasma sheet is modeled for an intense substorm event on March 19, 1978. The model is based on the idea that the substorm enhanced field-aligned currents are initiated in the ionosphere in response to an enhanced magnetospheric convection. The field-aligned currents in the model are determined from the ground-based magnetometer data with a time resolution of 5 min. The substorm field-aligned currents are assumed to close in the plasma sheet to complete the substorm current circuit. It is shown that the magnetic field produced by the substorm current system in the model can reproduce several important substorm signatures observed in the plasma sheet. These signatures include the taillike reconfiguration in the plasma sheet during the growth phase, the dipolarization of the plasma sheet associated with the substorm expansion onset, and the formation of a new X line. A shortcoming of the model is that the plasma dynamics in the plasma sheet have been ignored. In spite of this shortcoming, however, the model demonstrates that the ionosphere, in response to an enhanced magnetospheric convection, can cause the plasma sheet to change its magnetic configuration to result in the substorm signatures observed in the plasma sheet. The present study shows that it is possible for the ionosphere to play an active role in causing the observed reconfigurations of the plasma sheet during substorms.

  5. Evolution of asymmetrically displaced footpoints during substorms

    NASA Astrophysics Data System (ADS)

    Ohma, Anders; Østgaard, Nikolai; Reistad, Jone Peter; Tenfjord, Paul; Laundal, Karl M.; Snekvik, Kristian

    2017-04-01

    It is well established that a transverse (y) component in the interplanetary magnetic field (IMF) induces a By component in the closed magnetosphere through asymmetric loading and/or redistribution of magnetic flux. Simultaneous images of the aurora in the two hemispheres have revealed that conjugate auroral features are displaced longitudinally during such conditions, indicating that the field-lines are displaced from their symmetric configuration. Although the direction and magnitude of this displacement show correlations with IMF clock angle and dipole tilt, events show large temporal and spatial variability of this displacement. For instance, it is not clear how substorms affect the displacement. In a previous case study, it has been demonstrated that displaced auroral forms, associated with the present IMF orientation, returned to a more symmetric configuration during the expansion phase of two substorms. Using IMAGE and Polar, we have identified several events where conjugate images during substorm are available. We identify asymmetric auroral features during these events and investigate their time development during the substorm phases.

  6. Fast ionospheric feedback instability and substorm onset

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Grieger, John; Song, Yan

    1992-01-01

    A study suggesting that the Alfven resonator can play an important role in modifying the ionosphere on the time and space scales required to play a significant role in substorm formation is presented. Although the effect of magnetosphere-ionosphere coupling on the onset of substorms has been studied, the effects due to gradients of the Alfven speed along auroral field line were neglected. The large increase of the Alfven speed with altitude above the ionosphere creates an effective resonant cavity, which can lead to fluctuations in the electric and magnetic fields as well as in particle fluxes in the range 0.1 to 1 Hz. Such fluctuations can be observed from the ground as PiB pulsations associated with substorm onset. These fluctuations can be excited by a fast feedback instability, which can grow on time scales much less than the Alfven travel time between the ionosphere and the plasma sheet. The instability enhances the value of both the Pedersen and Hall conductivity, and may play a role in preparing the ionosphere for substorm onset.

  7. Fast ionospheric feedback instability and substorm onset

    NASA Technical Reports Server (NTRS)

    Lysak, Robert L.; Grieger, John; Song, Yan

    1992-01-01

    A study suggesting that the Alfven resonator can play an important role in modifying the ionosphere on the time and space scales required to play a significant role in substorm formation is presented. Although the effect of magnetosphere-ionosphere coupling on the onset of substorms has been studied, the effects due to gradients of the Alfven speed along auroral field line were neglected. The large increase of the Alfven speed with altitude above the ionosphere creates an effective resonant cavity, which can lead to fluctuations in the electric and magnetic fields as well as in particle fluxes in the range 0.1 to 1 Hz. Such fluctuations can be observed from the ground as PiB pulsations associated with substorm onset. These fluctuations can be excited by a fast feedback instability, which can grow on time scales much less than the Alfven travel time between the ionosphere and the plasma sheet. The instability enhances the value of both the Pedersen and Hall conductivity, and may play a role in preparing the ionosphere for substorm onset.

  8. Solar Wind-Magnetosphere Coupling Influences on Pseudo-Breakup Activity

    NASA Technical Reports Server (NTRS)

    Fillingim, M. O.; Brittnacher, M.; Parks, G. K.; Germany, G. A.; Spann, J. F.

    1998-01-01

    Pseudo-breakups are brief, localized aurora[ arc brightening, which do not lead to a global expansion, are historically observed during the growth phase of substorms. Previous studies have demonstrated that phenomenologically there is very little difference between substorm onsets and pseudo-breakups except for the degree of localization and the absence of a global expansion phase. A key open question is what physical mechanism prevents a pseudo-breakup form expanding globally. Using Polar Ultraviolet Imager (UVI) images, we identify periods of pseudo-breakup activity. Foe the data analyzed we find that most pseudo-breakups occur near local midnight, between magnetic local times of 21 and 03, at magnetic latitudes near 70 degrees, through this value may change by several degrees. While often discussed in the context of substorm growth phase events, pseudo-breakups are also shown to occur during prolonged relatively inactive periods. These quiet time pseudo-breakups can occur over a period of several hours without the development of a significant substorm for at least an hour after pseudo-breakup activity stops. In an attempt to understand the cause of quiet time pseudo-breakups, we compute the epsilon parameter as a measure of the efficiency of solar wind-magnetosphere coupling. It is noted that quiet time pseudo-breakups occur typically when epsilon is low; less than about 50 GW. We suggest that quiet time pseudo-breakups are driven by relatively small amounts of energy transferred to the magnetosphere by the solar wind insufficient to initiate a substorm expansion onset.

  9. Auroral Substorm Time Scales: Seasonal and IMF Variations

    NASA Technical Reports Server (NTRS)

    Chua, D.; Parks, G. K.; Brittnacher, M.; Germany, G. A.; Spann, J. F.; Six, N. Frank (Technical Monitor)

    2002-01-01

    The time scales and phases of auroral substorm, activity are quantied in this study using the hemispheric power computed from Polar Ultraviolet Imager (UVI) images. We have applied this technique to several hundred substorm events and we are able to quantify how the characterist act, of substorms vary with season and IMF Bz orientation. We show that substorm time scales vary more strongly with season than with IMF Bz orientation. The recovery time for substorm. activity is well ordered by whether or not the nightside oral zone is sunlit. The recovery time scales for substorms occurring in the winter and equinox periods are similar and are both roughly a factor of two longer than in summer when the auroral oval is sunlit. Our results support the hypothesis that the ionosphere plays an active role in governing the dynamics of the aurora.

  10. Auroral Substorm Time Scales: Seasonal and IMF Variations

    NASA Technical Reports Server (NTRS)

    Chua, D.; Parks, G. K.; Brittnacher, M.; Germany, G. A.; Spann, J. F.; Six, N. Frank (Technical Monitor)

    2002-01-01

    The time scales and phases of auroral substorm, activity are quantied in this study using the hemispheric power computed from Polar Ultraviolet Imager (UVI) images. We have applied this technique to several hundred substorm events and we are able to quantify how the characterist act, of substorms vary with season and IMF Bz orientation. We show that substorm time scales vary more strongly with season than with IMF Bz orientation. The recovery time for substorm. activity is well ordered by whether or not the nightside oral zone is sunlit. The recovery time scales for substorms occurring in the winter and equinox periods are similar and are both roughly a factor of two longer than in summer when the auroral oval is sunlit. Our results support the hypothesis that the ionosphere plays an active role in governing the dynamics of the aurora.

  11. Magnetospheric Sawtooth Oscillations Induced by Ionospheric Outflow

    NASA Astrophysics Data System (ADS)

    Brambles, O. J.; Lotko, W.; Zhang, B.; Lyon, J.; Wiltberger, M. J.

    2010-12-01

    This paper aims to address why sawtooth oscillations occur and what factors affect their periodicity. We use a multifluid version of the LFM global simulation model, driven by a steady solar wind to examine the effects of ion outflow on convection in the magnetosphere. In the simulation model, the properties of cusp and auroral region O+ outflow are causally regulated by electron precipitation and electromagnetic power flowing into the ionosphere. It is found that when ion outflow is included in the simulation, the solar wind-magnetosphere-ionosphere interaction can generate periodic substorms which appear as sawtooth-like oscillations in the geostationary magnetic field. The ion outflow enhances plasma pressure in the inner magnetosphere and the associated diamagnetic ring current stretches the field lines throughout the nightside, essentially from dawn to dusk. If the field lines are sufficiently stretched they reconnect and dipolarize, ejecting a plasmoid downtail. This cycle repeats forming multiple sawtooth oscillations. The periodicity of the sawtooth oscillation depends largely upon the strength of the outflow. The strength of outflow is varied in the simulation by changing both the driving conditions (which affects the power flowing into the ionosphere) and through direct modification of the constants in the empirical relationships. Higher outflow fluences produce oscillations with shorter periods. The period of the oscillation is found to vary in the simulations from approximately 2 hours to 6 hours depending upon the strength of the outflow. For a smaller solar wind electric field the outflow fluence is not large enough to stretch the nightside field lines enough for sawtooth oscillations to form and the magnetosphere goes into a steady magnetosphere convection (SMC) mode. As the solar wind electric field increases the outflow fluence becomes sufficiently large to affect the convection in the magnetosphere and generate sawtooth oscillations. The strength

  12. MESSENGER: Exploring Mercury's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Slavin, James A.

    2008-01-01

    The MESSENGER mission to Mercury offers our first opportunity to explore this planet's miniature magnetosphere since Mariner 10's brief fly-bys in 1974-5. Mercury's magnetosphere is unique in many respects. The magnetosphere of Mercury is the smallest in the solar system with its magnetic field typically standing off the solar wind only - 1000 to 2000 km above the surface. For this reason there are no closed dri-fi paths for energetic particles and, hence, no radiation belts; the characteristic time scales for wave propagation and convective transport are short possibly coupling kinetic and fluid modes; magnetic reconnection at the dayside magnetopause may erode the subsolar magnetosphere allowing solar wind ions to directly impact the dayside regolith; inductive currents in Mercury's interior should act to modify the solar In addition, Mercury's magnetosphere is the only one with its defining magnetic flux tubes rooted in a planetary regolith as opposed to an atmosphere with a conductive ionosphere. This lack of an ionosphere is thought to be the underlying reason for the brevity of the very intense, but short lived, approx. 1-2 min, substorm-like energetic particle events observed by Mariner 10 in Mercury's magnetic tail. In this seminar, we review what we think we know about Mercury's magnetosphere and describe the MESSENGER science team's strategy for obtaining answers to the outstanding science questions surrounding the interaction of the solar wind with Mercury and its small, but dynamic magnetosphere.

  13. Storm-Time Substorms and Sawtooth Events: Test for Substorm Models

    NASA Astrophysics Data System (ADS)

    Pulkkinen, T. I.; Tanskanen, E. I.; Reeves, G. D.; Donovan, E.; Singer, H. J.; Slavin, J. A.

    2005-12-01

    A substorm search engine is used to identify substorm onsets that occur during magnetic storms in the period 2001-2004. Each substorm is analyzed in detail using several parameters to classify the events. Peak amplitude of the substorm is defined from the AL-index. Existence and type of energetic particle injections are determined from the LANL energetic ion and electron data. Tail magnetic field measurements (GOES, Cluster, Geotail) are used to infer whether a thin current sheet was formed prior to the substorm onset. Latitudinal magnetometer chains (CANOPUS, IMAGE) are used to determine whether the main expansion direction was poleward or equatorward. Possible triggers for the onset and intensity of the driving electric field are identified from the solar wind and interplanetary magnetic field measurements (ACE, WIND). The goal of the study is to statistically examine to what extent the stormtime substorms show signatures typically associated classical non-storm substorms and to what extent the activity is characteristic only of storm periods. Furthermore, the goal is to identify the "sawtooth events" from the data set, and examine whether the activation characteristics differ from the other stormtime activations.

  14. THEMIS and Substorm Timing

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.

    2010-01-01

    The THEMIS mission represents the culmination of many years of planning directed towards understanding the processes that drive and trigger geomagnetic substorms. Following Akasofu's discovery of the substorm cycle, it became increasingly clear that timing questions provide the key to discriminating between proposed 'inside-out' and 'outside-in' models for substorms, triggered respectively by current disruption and magnetic reconnection. THEMIS observations provide a wealth of information that is currently being investigated to resolve this question. While observations in the magnetotail generally point towards reconnection. those on the ground point towards current disruption. This talk reviews the relevant observations and recent efforts at reconciliation.

  15. Empirical evidence for two nightside current wedges during substorms

    NASA Astrophysics Data System (ADS)

    Hoffman, R. A.; Gjerloev, J. W.

    2013-12-01

    We present results from a comprehensive statistical study of the ionospheric current system and its coupling to the magnetosphere during classical bulge type substorms. We identified 116 substorms and determined the global ionospheric current system before and during the substorm using the SuperMAG initiative and global auroral images obtained by the Polar VIS Earth camera. The westward electrojet (WEJ) display a distinct latitudinal shift between the pre- and post-midnight region and we find evidence that the two WEJ regions are disconnected. This, and other observational facts, led us to propose a new 3D current system configuration that consists of 2 wedge type systems: a current wedge in the pre-midnight region (substorm current wedge), and another current wedge system in the post-midnight region (oval current wedge). There is some local time overlap between the two systems. The former maps to the region inside the near Earth neutral line and is associated with structured BPS type electron precipitation. The latter maps to the inner magnetosphere and is associated with diffuse electron precipitation. We present results of the statistical study, show typical events, results from Biot-Savart simulations, and discuss the implications for our understanding of the 3D current system associated with substorms.

  16. Small substorms: Solar wind input and magnetotail dynamics

    NASA Astrophysics Data System (ADS)

    Petrukovich, A. A.; Baumjohann, W.; Nakamura, R.; Mukai, T.; Troshichev, O. A.

    We investigated properties of 43 small magnetospheric substorms. Their general signatures were found to be consistent with the so-called contracted oval or northern Bz substorms. Small but clear pressure changes in the tail corresponding to growth and expansion phases detected in about a half of cases testify that these substorms follow the same loading-unloading scheme as the larger ones. However, rate of the solar wind energy accumulation in the magnetosphere was low due to azimuthal IMF orientation with dominating IMFBy and small fluctuating IMFBz. Plasma sheet signatures could be very strong and likely were localized in their cross-tail size. Negative bays in auroral X magnetograms were of order of 100-300 nT, with maxima at Bear Island station (71° geomagnetic latitude) and in few cases were delayed after magnetotail onsets by tens of minutes. Small substorms probably differ from their larger counterparts in a way that coherency of the magnetotail reconfiguration in the inner and middle-tail regions and across the tail is lost in smaller substorms.

  17. Statistical properties of substorm auroral onset beads/rays

    NASA Astrophysics Data System (ADS)

    Nishimura, Y.; Yang, J.; Pritchett, P. L.; Coroniti, F. V.; Donovan, E. F.; Lyons, L. R.; Wolf, R. A.; Angelopoulos, V.; Mende, S. B.

    2016-09-01

    Auroral substorms are often associated with optical ray or bead structures during initial brightening (substorm auroral onset waves). Occurrence probabilities and properties of substorm onset waves have been characterized using 112 substorm events identified in Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imager data and compared to Rice Convection Model-Equilibrium (RCM-E) and kinetic instability properties. All substorm onsets were found to be associated with optical waves, and thus, optical waves are a common feature of substorm onset. Eastward propagating wave events are more frequent than westward propagating wave events and tend to occur during lower-latitude substorms (stronger solar wind driving). The wave propagation directions are organized by orientation of initial brightening arcs. We also identified notable differences in wave propagation speed, wavelength (wave number), period, and duration between westward and eastward propagating waves. In contrast, the wave growth rate does not depend on the propagation direction or substorm strength but is inversely proportional to the wave duration. This suggests that the waves evolve to poleward expansion at a certain intensity threshold and that the wave properties do not directly relate to substorm strengths. However, waves are still important for mediating the transition between the substorm growth phase and poleward expansion. The relation to arc orientation can be explained by magnetotail structures in the RCM-E, indicating that substorm onset location relative to the pressure peak determines the wave propagation direction. The measured wave properties agree well with kinetic ballooning interchange instability, while cross-field current instability and electromagnetic ion cyclotron instability give much larger propagation speed and smaller wave period.

  18. Global magnetospheric dynamics - Reporter reviews and global magnetospheric dynamics; 1989 IAGA Division III, Symposia Papers

    NASA Astrophysics Data System (ADS)

    Siscoe, George L.

    1990-12-01

    Topics presented include 1987-1989 magnetosheath, magnetopause and low latitude boundary layer research; the morphology of magnetic merging at the magnetopause; the global dynamics of the magnetosphere for northward IMF conditions; and some recent advances in magnetospheric substorm research. Consideration is also given to the energetic particles in the environment of the earth's magnetosphere, ULF waves on the ground and in space, the magnetic field of the magnetospheric ring current and its dynamics during magnetic storms, and a review of extraterrestrial magnetosphere research during 1987-1989.

  19. What effect do substorms have on the content of the radiation belts?

    PubMed Central

    Rae, I. J.; Murphy, K. R.; Freeman, M. P.; Huang, C.‐L.; Spence, H. E.; Boyd, A. J.; Coxon, J. C.; Jackman, C. M.; Kalmoni, N. M. E.; Watt, C. E. J.

    2016-01-01

    Abstract Substorms are fundamental and dynamic processes in the magnetosphere, converting captured solar wind magnetic energy into plasma energy. These substorms have been suggested to be a key driver of energetic electron enhancements in the outer radiation belts. Substorms inject a keV “seed” population into the inner magnetosphere which is subsequently energized through wave‐particle interactions up to relativistic energies; however, the extent to which substorms enhance the radiation belts, either directly or indirectly, has never before been quantified. In this study, we examine increases and decreases in the total radiation belt electron content (TRBEC) following substorms and geomagnetically quiet intervals. Our results show that the radiation belts are inherently lossy, shown by a negative median change in TRBEC at all intervals following substorms and quiet intervals. However, there are up to 3 times as many increases in TRBEC following substorm intervals. There is a lag of 1–3 days between the substorm or quiet intervals and their greatest effect on radiation belt content, shown in the difference between the occurrence of increases and losses in TRBEC following substorms and quiet intervals, the mean change in TRBEC following substorms or quiet intervals, and the cross correlation between SuperMAG AL (SML) and TRBEC. However, there is a statistically significant effect on the occurrence of increases and decreases in TRBEC up to a lag of 6 days. Increases in radiation belt content show a significant correlation with SML and SYM‐H, but decreases in the radiation belt show no apparent link with magnetospheric activity levels. PMID:27656336

  20. What effect do substorms have on the content of the radiation belts?

    PubMed

    Forsyth, C; Rae, I J; Murphy, K R; Freeman, M P; Huang, C-L; Spence, H E; Boyd, A J; Coxon, J C; Jackman, C M; Kalmoni, N M E; Watt, C E J

    2016-07-01

    Substorms are fundamental and dynamic processes in the magnetosphere, converting captured solar wind magnetic energy into plasma energy. These substorms have been suggested to be a key driver of energetic electron enhancements in the outer radiation belts. Substorms inject a keV "seed" population into the inner magnetosphere which is subsequently energized through wave-particle interactions up to relativistic energies; however, the extent to which substorms enhance the radiation belts, either directly or indirectly, has never before been quantified. In this study, we examine increases and decreases in the total radiation belt electron content (TRBEC) following substorms and geomagnetically quiet intervals. Our results show that the radiation belts are inherently lossy, shown by a negative median change in TRBEC at all intervals following substorms and quiet intervals. However, there are up to 3 times as many increases in TRBEC following substorm intervals. There is a lag of 1-3 days between the substorm or quiet intervals and their greatest effect on radiation belt content, shown in the difference between the occurrence of increases and losses in TRBEC following substorms and quiet intervals, the mean change in TRBEC following substorms or quiet intervals, and the cross correlation between SuperMAG AL (SML) and TRBEC. However, there is a statistically significant effect on the occurrence of increases and decreases in TRBEC up to a lag of 6 days. Increases in radiation belt content show a significant correlation with SML and SYM-H, but decreases in the radiation belt show no apparent link with magnetospheric activity levels.

  1. From space weather toward space climate time scales: Substorm analysis from 1993 to 2008

    NASA Astrophysics Data System (ADS)

    Tanskanen, E. I.; Pulkkinen, T. I.; Viljanen, A.; Mursula, K.; Partamies, N.; Slavin, J. A.

    2011-05-01

    Magnetic activity in the Northern Hemisphere auroral region was examined during solar cycles 22 and 23 (1993-2008). Substorms were identified from ground-based magnetic field measurements by an automated search engine. On average, 550 substorms were observed per year, which gives in total about 9000 substorms. The interannual, seasonal and solar cycle-to-cycle variations of the substorm number (Rss), substorm duration (Tss), and peak amplitude (Ass) were examined. The declining phases of both solar cycles 22 and 23 were more active than the other solar cycle phases due to the enhanced solar wind speed. The spring substorms during the declining solar cycle phase (∣Ass,decl∣ = 500 nT) were 25% larger than the spring substorms during the ascending solar cycle years (∣Ass,acs∣ = 400 nT). The following seasonal variation was found: the most intense substorms occurred during spring and fall, the largest substorm frequency in the Northern Hemisphere winter, and the longest-duration substorms in summer. Furthermore, we found a winter-summer asymmetry in the substorm number and duration, which is speculated to be due to the variations in the ionospheric conductivity. The solar cycle-to-cycle variation was found in the yearly substorm number and peak amplitude. The decline from the peak substorm activity in 1994 and 2003 to the following minima took 3 years during solar cycle 22, while it took 6 years during solar cycle 23.

  2. Auroral Substorms: Paradigm Shifts in Research

    NASA Astrophysics Data System (ADS)

    Akasofu, Syun-Ichi

    2010-08-01

    The study of scientific advancement is the study of evolving thought. Disciplines progress as old prevailing theoretical ideas are toppled by new ones, one after another. Provided that new ideas can be independently verified, scientists at any level can greatly contribute to their field. Though space weather is a young field, it has been riddled with such paradigm shifts. As a scientist who has worked on auroral and magnetospheric substorm research during several of these moments, I have witnessed firsthand how diligence, patience, and creativity combine to advance science.

  3. Interball substorm observations: Christmas for space scientists

    NASA Technical Reports Server (NTRS)

    Sandahl, Ingrid; Pulkkinen, Tuija; Budnik, Elena Yu.; Dubinin, Edouard M.; Eklund, Ulrik; Hughes, Terence J.; Kokubun, Susumu; Koskinen, Hannu; Kudela, Karel; Lepping, Ronald P.; Lin, Robert P.; Lui, Anthony T. Y.; Lutsenko, Volt; Mostroem, Arne; Nozdrachev, Michail; Pissarenko, Novomir, F.; Prokhorenko, Victoria; Sauvaud, Jean-Andre; Yermolaev, Yuri I.; Zakharov, Alexander V.

    1996-01-01

    Observational results from the Interball Tail Probe spacecraft are presented. One of the main objectives of the Interball project is to study the dynamic processes in the magnetosphere. Three events observed by the spacecraft's instruments are investigated: a pseudobreakup during which earthward streaming ions were observed in the vicinity of a thin current sheet; a substorm in which the magnetic signatures in the lobe and on the ground were preceeded by northward re-orientation of the interplanetary magnetic field Bz component; and a magnetic storm at the beginning of which extreme deformation of the magnetotail was observed.

  4. Interball substorm observations: Christmas for space scientists

    NASA Technical Reports Server (NTRS)

    Sandahl, Ingrid; Pulkkinen, Tuija; Budnik, Elena Yu.; Dubinin, Edouard M.; Eklund, Ulrik; Hughes, Terence J.; Kokubun, Susumu; Koskinen, Hannu; Kudela, Karel; Lepping, Ronald P.; hide

    1996-01-01

    Observational results from the Interball Tail Probe spacecraft are presented. One of the main objectives of the Interball project is to study the dynamic processes in the magnetosphere. Three events observed by the spacecraft's instruments are investigated: a pseudobreakup during which earthward streaming ions were observed in the vicinity of a thin current sheet; a substorm in which the magnetic signatures in the lobe and on the ground were preceeded by northward re-orientation of the interplanetary magnetic field Bz component; and a magnetic storm at the beginning of which extreme deformation of the magnetotail was observed.

  5. The Role of Substorms in Radiation Belt Particle Enhancements

    NASA Astrophysics Data System (ADS)

    Baker, D. N.

    2014-12-01

    Observational and numerical modeling evidence demonstrates that magnetospheric substorms are a coherent set of processes within the coupled near-Earth system. This supports the view that substorms are a global configurational instability. The magnetosphere progresses through a specific sequence of energy-loading and stress-developing states until the entire system suddenly reconfigures. Related long-term studies of relativistic electron fluxes in the Earth's magnetosphere have revealed many of their temporal occurrence characteristics and their relationships to solar wind drivers. Early work showed the obvious and powerful role played by solar wind speed in producing subsequent high-energy electron enhancements. More recent work has also pointed out the key role that the north-south component of the IMF plays: In order to observe major relativistic electron enhancements, there must typically be a significant interval of southward IMF along with a period of high (VSW≥500 km/s) solar wind speed. This has led to the view that enhancements in geomagnetic activity (i.e., magnetospheric substorms) are normally a key first step in the acceleration of radiation belt electrons to high energies. A second step is suggested to be a period of powerful low-frequency waves that is closely related to high values of VSW or higher frequency ("chorus") waves that rapidly heat and accelerate electrons. Hence, substorms provide a "seed" population, while high-speed solar wind drives the acceleration to relativistic energies in this two-step geomagnetic activity scenario. This picture seems to apply to most storms examined whether associated with high-speed streams or with CME-related events. In this talk, we address the substorm relationships as they pertain to high-energy electron acceleration and transport. We also discuss various models of electron energization that have recently been advanced. We present remarkable new results from the Van Allen Probes (Radiation Belt Storm

  6. Drift-shell splitting of energetic ions injected at pseudo-substorm onsets

    SciTech Connect

    Takahashi, K. |; Anderson, B.J.; Ohtani, S.; Reeves, G.D.; Takahashi, S.; Sarris, T.E. |; Mursula, K.

    1997-10-01

    One feature of a magnetospheric substorm is the injection of energetic particles into closed drift orbits. Injections are routinely observed by geosynchronous satellites and have been used to identify the occurrence of substorms and the local time of particle energization. In this study we examine pitch angle distributions of ion injections in the 50-to 300-keV energy range observed by the Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE/CCE) satellite, hereinafter CCE. In a dipole field, all pitch angles follow the same drift shell, but the day{endash}night asymmetry of the magnetospheric magnetic field introduces a pitch angle dependence in particle drift orbits, so that particles with different pitch angles disperse radially as they drift. The effect is known as drift-shell splitting. For satellite observations near noon at a fixed geocentric distance, the guiding center orbits of ions detected at small pitch angles intersect the midnight meridian at larger geocentric distances than do ions with near-90{degree} pitch angles. The ion pitch angle distributions detected on the dayside therefore provide information about the radial distance of the nightside acceleration region. We apply this principle to study ion injection events observed on September 17{endash}18, 1984, in association with pseudo-substorm onsets. CCE was at 13 hours local time near its apogee (8.8R{sub E}) and observed a series of ion flux enhancements. Energy dispersion of the timing of the flux increases assures that they are due to injections on the nightside. The flux increases were observed only at pitch angles from 0{degree} to 60{degree}. We calculate drift orbits of protons using the Tsyganenko 89c magnetic field model and find that the drift orbits for 60{degree} pitch angle protons observed at the satellite pass through midnight at 9R{sub E}, well outside of geostationary orbit, indicating that the ion injections occurred tailward of 9R{sub E}. Energetic

  7. Energy coupling between the solar wind and the magnetosphere

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1981-01-01

    A description is given of the path leading to the first approximation expression for the solar wind-magnetosphere energy coupling function (epsilon), which correlates well with the total energy consumption rate (U sub T) of the magnetosphere. It is shown that epsilon is the primary factor controlling the time development of magnetospheric substorms and storms. The finding of this particular expression epsilon indicates how the solar wind couples its energy to the magnetosphere; the solar wind and the magnetosphere make up a dynamo. In fact, the power generated by the dynamo can be identified as epsilon through the use of a dimensional analysis. In addition, the finding of epsilon suggests that the magnetosphere is closer to a directly driven system than to an unloading system which stores the generated energy before converting it to substorm and storm energies. The finding of epsilon and its implications is considered to have significantly advanced and improved the understanding of magnetospheric processes.

  8. Decay of the Dst field of geomagnetic disturbance after substorm onset and its implication to storm-substorm relation

    NASA Astrophysics Data System (ADS)

    Iyemori, T.; Rao, D. R. K.

    1996-06-01

    In order to investigate the causal relationship between magnetic storms and substorms, variations of the mid-latitude geomagnetic indices, ASY (asymmetric part) and SYM (symmetric part), at substorm onsets are examined. Substorm onsets are defined by three different phenomena; (1) a rapid increase in the mid-latitude asymmetric-disturbance indices, ASY-D and ASY-H, with a shape of so-called `mid-latitude positive bay\\'; (2) a sharp decrease in the AL index; (3) an onset of Pi2 geomagnetic pulsation. The positive bays are selected using eye inspection and a pattern-matching technique. The 1-min-resolution SYM-H index, which is essentially the same as the hourly Dst index except in terms of the time resolution, does not show any statistically significant development after the onset of substorms; it tends to decay after the onset rather than to develop. It is suggested by a simple model calculation that the decay of the magnetospheric tail current after substorm onset is responsible for the decay of the Dst field. The relation between the IMF southward turning and the development of the Dst field is re-examined. The results support the idea that the geomagnetic storms and substorms are independent processes; that is, the ring-current development is not the result of the frequent occurrence of substorms, but that of enhanced convection caused by the large southward IMF. A substorm is the process of energy dissipation in the magnetosphere, and its contribution to the storm-time ring-current formation seems to be negligible. The decay of the Dst field after a substorm onset is explained by a magnetospheric energy theorem. 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.-> Correspondence to: Y. Kamide->

  9. The February 24, 2010 substorm: a refined view involving a pseudobreakup/expansive phase/poleward boundary intensification sequence

    NASA Astrophysics Data System (ADS)

    Connors, Martin; Russell, Christopher T.; Chu, Xiangning; McPherron, Robert L.

    2015-12-01

    A substorm on February 24, 2010 was chosen for study by Connors et al. (Geophys. Res. Lett. 41:4449-4455, 2014) due to simple symmetric subauroral magnetic perturbations observed in North America. It was shown that a substorm current wedge (SCW) three-dimensional current model could represent these perturbations well, gave a reasonable representation of auroral zone perturbations, and matched field-aligned currents determined in space from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) project. The conclusion was that substorm onset was at approximately 4:30 UT and that the substorm current wedge (SCW) formed in the region 1 (more poleward) current system.

  10. The aurora and the magnetosphere - The Chapman Memorial Lecture. [dynamo theory development, 1600-present

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1974-01-01

    Review of recent progress in magnetospheric physics, in particular, in understanding the magnetospheric substorm. It is shown that a number of magnetospheric phenomena can now be understood by viewing the solar wind-magnetosphere interaction as an MHD dynamo; auroral phenomena are powered by the dynamo. Also, magnetospheric responses to variations of the north-south and east-west components of the interplanetary magnetic field have been identified. The magnetospheric substorm is entirely different from the responses of the magnetosphere to the southward component of the interplanetary magnetic field. It may be associated with the formation of a neutral line within the plasma sheet and with an enhanced reconnection along the line. A number of substorm-associated phenomena can be understood by noting that the new neutral line formation is caused by a short-circuiting of a part of the magnetotail current.

  11. The aurora and the magnetosphere - The Chapman Memorial Lecture. [dynamo theory development, 1600-present

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1974-01-01

    Review of recent progress in magnetospheric physics, in particular, in understanding the magnetospheric substorm. It is shown that a number of magnetospheric phenomena can now be understood by viewing the solar wind-magnetosphere interaction as an MHD dynamo; auroral phenomena are powered by the dynamo. Also, magnetospheric responses to variations of the north-south and east-west components of the interplanetary magnetic field have been identified. The magnetospheric substorm is entirely different from the responses of the magnetosphere to the southward component of the interplanetary magnetic field. It may be associated with the formation of a neutral line within the plasma sheet and with an enhanced reconnection along the line. A number of substorm-associated phenomena can be understood by noting that the new neutral line formation is caused by a short-circuiting of a part of the magnetotail current.

  12. A relation of the values of the longitudinal drift of substorm current systems with solar wind parameters

    NASA Astrophysics Data System (ADS)

    Litinskii, V. M.

    A relationship between the drift of substorm current systems and magnetospheric convection can be demonstrated by determining the interval of longitudes in which the center of the mid-latitude current vortex shifts during the course of the substorm. Drift values were obtained from 1963-1974 by calculating the difference between angles of inclination of the disturbance vector at the beginning and at the end of the substorm. This difference in angles was then used with a formula of spherical trigonometry to determine the longitude of the center of the current vortex at the beginning and end of the substorm. The longitudinal drift of substorm current systems is shown to resemble the drift of elevated ionization regions in the auroral zone and the auroral arcs, and is due to magnetospheric convection. The relationship between the values of longitudinal drift and solar wind parameters supports this observation.

  13. Magnetotail energy dissipation during an auroral substorm

    PubMed Central

    Panov, E.V.; Baumjohann, W.; Wolf, R.A.; Nakamura, R.; Angelopoulos, V.; Weygand, J. M.; Kubyshkina, M.V.

    2016-01-01

    Violent releases of space plasma energy from the Earth’s magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1km/s. This observed auroral activity appears sufficient to dissipate the released energy. PMID:27917231

  14. Magnetotail energy dissipation during an auroral substorm

    NASA Astrophysics Data System (ADS)

    Panov, Evgeny V.; Baumjohann, Wolfgang; Wolf, Richard A.; Nakamura, Rumi; Angelopoulos, Vassilis; Weygand, James M.; Kubyshkina, Marina V.

    2017-04-01

    Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1 km s-1. This observed auroral activity appears sufficient to dissipate the released energy.

  15. Magnetotail energy dissipation during an auroral substorm.

    PubMed

    Panov, E V; Baumjohann, W; Wolf, R A; Nakamura, R; Angelopoulos, V; Weygand, J M; Kubyshkina, M V

    2016-12-01

    Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1km/s. This observed auroral activity appears sufficient to dissipate the released energy.

  16. Magnetotail energy dissipation during an auroral substorm

    NASA Astrophysics Data System (ADS)

    Panov, E. V.; Baumjohann, W.; Wolf, R. A.; Nakamura, R.; Angelopoulos, V.; Weygand, J. M.; Kubyshkina, M. V.

    2016-12-01

    Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1 km s-1. This observed auroral activity appears sufficient to dissipate the released energy.

  17. Auroral Acceleration, Solar Wind Driving, and Substorm Triggering (Invited)

    NASA Astrophysics Data System (ADS)

    Newell, P. T.; Liou, K.

    2010-12-01

    We use a data base of 4861 substorms identified by global UV images to investigate the substorm cycle dependence of various types of aurora, and to obtain new results on substorm triggering by external driving. Although all types of aurora increase at substorm onset, broadband (Alfvénic) aurora shows a particular association with substorms, and, especially, substorm onset. While diffuse electron and monoenergetic auroral precipitating power rises by 79% and 90% respectively following an onset, broadband aurora rises by 182%. In the first 10-15 minutes following onset, the power associated with Alfvénic acceleration is comparable to monoenergetic acceleration (also called “inverted-V” events). In general, this is not the case prior to onset, or indeed, during recovery. The rise time of the electron diffuse aurora following onset is much slower, about 50 minutes, and thus presumably extends into recovery. We also re-investigate the issue of solar wind triggering of substorms by considering not just changes in the solar wind prior to onset, but how the pattern of changes differs from random and comparable epochs. We verify that a preonset reduction of solar wind driving (“northward turning” in the simplest case of IMF Bz) holds for the superposed epoch mean of the ensemble. Moreover, this reduction is not the result of a small number of substorms with large changes. The reduction starts about 20 min prior to substorm onset, which, although a longer delay than previously suggested, is appropriate given the various propagation time delays involved. Next, we compare the IMF to random solar wind conditions. Not surprisingly, solar wind driving prior to onset averages somewhat higher than random. Although about a quarter of substorms occur for steady northward IMF conditions, more general coupling functions such as the Kan-Lee electric field, the Borovosky function, or our dΦMP/dt, show very few substorms occur following weak dayside merging. We assembled a data

  18. Investigation of isolated substorms: Generation conditions and characteristics of different phases

    NASA Astrophysics Data System (ADS)

    Vorobjev, V. G.; Yagodkina, O. I.; Zverev, V. L.

    2016-11-01

    Characteristics of isolated substorms selected by variations in the 1-min values of the AL index are analyzed. The substorms were divided into several types with respect to the behavior of the Bz component of the interplanetary magnetic field (IMF) during the expansion phase. The probability of observations of substorms associated with the northward turn of the Bz component of IMF was 19%, while the substorms taking place at Bz < 0 were observed in 53% of cases. A substantial number of events in which no substorm magnetic activity was observed in the auroral zone after a long (>30 min) period of the southward IMF and a following sharp turn of the Bz component of IMF before the north was detected. The data suggest that a northward IMF turn is neither a necessary nor sufficient condition for generating substorms. It has been shown for substorms of the both types that the average duration of the southward IMF to moment T 0 and the average intensity of the magnetic perturbation in the maximum are approximately the same and amount to 80 min and-650 nT, respectively. However, for substorms at Bz < 0, their mean duration, including the expansive and recovery phases, is on average 30 min longer than that at a northward turn of IMF. Correlations between the loading-unloading processes in the magnetosphere in the periods of magnetospheric substorms were investigated with different functions that determine the efficiency of the energy transfer from the solar wind to the magnetosphere. It has been shown that the highest correlation coefficient ( r = 0.84) is observed when the function suggested by Newell et al. (2007) is used. It has been detected that a simple function VB S yields a high correlation coefficient ( r = 0.75).

  19. Relationship between auroral substorms and the occurrence of terrestrial kilometric radiation

    NASA Technical Reports Server (NTRS)

    Kaiser, M. L.; Alexander, J. K.

    1977-01-01

    The correlation between magnetospheric substorms as inferred from the AE(11) index and the occurrence of terrestrial kilometric radiation (TKR) is examined. It is found that AE and TKR are well correlated when observations are made from above the 15-03 hr local time zone and are rather poorly correlated over the 03-15 hr zone. High-resolution dynamic spectra obtained during periods of isolated substorms indicate that low-intensity, high-frequency TKR commences at about the same time as the substorm phase. The substorm expansion phase corresponds to a rapid intensification and bandwidth increase of TKR. When combined with previous results, these new observations imply that many TKR events begin at low altitudes and high frequencies (about 400-500 kHz) and spread to higher altitudes and lower frequencies as the substorm expands.

  20. Configuration and Generation of Substorm Current Wedge

    NASA Astrophysics Data System (ADS)

    Chu, Xiangning

    The substorm current wedge (SCW), a core element of substorm dynamics coupling the magnetotail to the ionosphere, is crucial in understanding substorms. It has been suggested that the field-aligned currents (FACs) in the SCW are caused by either pressure gradients or flow vortices, or both. Our understanding of FAC generations is based predominately on numerical simulations, because it has not been possible to organize spacecraft observations in a coordinate system determined by the SCW. This dissertation develops an empirical inversion model of the current wedge and inverts midlatitude magnetometer data to obtain the parameters of the current wedge for three solar cycles. This database enables statistical data analysis of spacecraft plasma and magnetic field observations relative to the SCW coordinate. In chapter 2, a new midlatitude positive bay (MPB) index is developed and calculated for three solar cycles of data. The MPB index is processed to determine the substorm onset time, which is shown to correspond to the auroral breakup onset with at most 1-2 minutes difference. Substorm occurrence rate is found to depend on solar wind speed while substorm duration is rather constant, suggesting that substorm process has an intrinsic pattern independent of external driving. In chapter 3, an SCW inversion technique is developed to determine the strength and locations of the FACs in an SCW. The inversion parameters for FAC strength and location, and ring current strength are validated by comparison with other measurements. In chapter 4, the connection between earthward flows and auroral poleward expansion is examined using improved mapping, obtained from a newly-developed dynamic magnetospheric model by superimposing a standard magnetospheric field model with substorm current wedge obtained from the inversion technique. It is shown that the ionospheric projection of flows observed at a fixed point in the equatorial plane map to the bright aurora as it expands poleward

  1. Magnetotail energy storage and release during the CDAW 6 substorm analysis intervals

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Fritz, T. A.; Mcpherron, R. L.; Fairfield, D. H.; Kamide, Y.; Baumjohann, W.

    1985-01-01

    The concept of the Coordinated Data Analysis Workshop (CDAW) grew out of the International Magnetospheric Study (IMS) program. According to this concept, data are to be pooled from a wide variety of spacecraft and ground-based sources for limited time intervals. These data are to provide the basis for the performance of very detailed correlative analyses, usually with fairly limited physical problems in mind. However, in the case of the CDAW 6 truly global goals are involved. The primary goal is to trace the flow of energy from the solar wind through the magnetosphere to its ultimate dissipation by substorm processes. The present investigation has the specific goal to examine the evidence for the storage of solar wind energy in the magnetotail prior to substorm expansion phase onsets. Of particular interest is the determination, in individual substorm cases, of the time delays between the loading of energy into the magnetospheric system and the subsequent unloading of this energy.

  2. The magnetosphere of Neptune - Hot plasmas and energetic particles

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.; Keath, E. P.; Kane, M.; Krimigis, M.; Cheng, A. F.; Acuna, M. H.; Armstrong, T. P.; Ness, N. F.

    1991-01-01

    An overview is presented of the hot plasmas and energetic (not less than 20 keV) particles observed in the vicinity of Neptune by the Low Energy Charged Particle (LECP) experiment aboard the Voyager 2 spacecraft. The LECP findings are presented on the shock, the magnetosheath, the magnetopause, and the cusp of the Neptune's magnetosphere; the middle magnetosphere; the inner magnetosphere and material interactions; the magnetotail and the substorms; and the characteristics of Triton's plasma. It is shown that, in sharp contrast to the Uranian magnetotail, the Neptunian magnetotail shows no evidence of substorm processes.

  3. Statistical comparison of inter-substorm timings in global magnetohydrodynamics (MHD) and observations

    NASA Astrophysics Data System (ADS)

    Haiducek, J. D.; Welling, D. T.; Morley, S.; Ozturk, D. S.

    2015-12-01

    Magnetospheric substorms are events in which energy stored in the magnetotail is released into the auroral zone and into the downstream solar wind. Because of the complex, nonlinear, and possibly chaotic nature of the substorm energy release mechanism, it may be extremely difficult to forecast individual substorms in the near term. However, the inter-substorm timing (the amount of time elapsed between substorms) can be reproduced in a statistical sense, as was demonstrated by Freeman and Morley (2004) using their Minimal Substorm Model (MSM), a simple solar-wind driven model with the only free parameter being a recurrence time. The goal of the present work is to reproduce the observed distribution of inter-substorm timings with a global MHD model. The period of 1-31 January 2005 was simulated using the Space Weather Modeling Framework (SWMF), driven by solar wind observations. Substorms were identified in the model output by synthesizing surface magnetometer data and by looking for tailward-moving plasmoids. Substorms identified in the MHD model are then compared with observational data from the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, Los Alamos National Laboratory (LANL) geostationary satellite energetic particle data, and surface magnetometer data. For each dataset (MHD model and observations), we calculate the substorm occurrence rate, and for the MHD model we additionally calculate the timing error of the substorm onsets relative to the observed substorms. Finally, we calculate distribution functions for the inter-substorm timings in both the observations and the model. The results of this analysis will guide improvements to the MHD-based substorm model, including the use of Hall MHD and embedded particle in cell (EPIC), leading to a better reproduction of the observed inter-substorm timings and an improved understanding of the underlying physical processes. ReferencesM. P. Freeman and S. K. Morley. A minimal substorm model that

  4. A case study of the response of the magnetosphere to changes in the interplanetary medium

    NASA Technical Reports Server (NTRS)

    Rostoker, G.; Baumjohann, W.; Russell, C. T.

    1983-01-01

    A detailed analysis of world-wide ground based magnetometer data is presented, together with information on the plasma and magnetic field properties of the interplanetary medium and magnetosheath obtained from the ISEE 1 and 2 and IMP 8 spacecraft. The event concerned exhibited an interval of relatively stable southward IMF followed by a sharp northward turning. It is pointed out that during the interval of southward IMF there were occasional transient northward turnings with significant substorm expansive phase activity appearing to be triggered by these transient northward turnings. The final northward turning of the IMF was linked with an episode of strong magnetospheric substorm expansive phase activity after which the level of high latitude magnetic activity declined to a low level. Evidence is presented indicating that the driven system auroral electrojets begin to decay at the time of the northward turning of the IMF, even as the substorm expansive phase activity is initiated in the midnight sector. The collapse of the substorm current wedge during the final decay of high latitude activity is described in some detail, and it is shown that this collapse occurs progressively from east to west in a series of impulsive episodes.

  5. Phenomenological and Theoretical Studies on Magnetic Indicators of Substorm Activity.

    DTIC Science & Technology

    1980-03-21

    docummeni-we report results of studies made on substorm de- tection, behavior, and irelationship to magnetospheric processes . A scheme is developed whereby...regard. Field aligned currents drive ionospheric current systems on a global scale. A model is developed to describe this process for quiet and disturbed...currents and ionospheric closure currents., This process is discussed and estimates are developed for the relative ’c6ntributions of Pederson and

  6. Dynamics of Mars' magnetosphere

    SciTech Connect

    Kennel, C.F.; Coroniti, F.V. ); Zelenyi, L.M. ); Moses, S.L.

    1989-08-01

    If Mars has a small intrinsic magnetic moment, Mars' magnetosphere could vary on time scales of a few minutes due to reconnection with the solar wind magnetic field. The day-side magnetopause will be one or two reflected-ion Larmor radii from the bow shock. Substorms will have scale-times of about six minutes. Mars' high ionospheric conductance will virtually stop polar cap convection, and create a magnetic topological crisis unless convecting magnetic flux finds a dissipative way to return to the day-side. The strong magnetic hear induced by magnetospheric convection above the ionosphere could be tearing unstable. The magnetic field might diffusively percolate through the tearing layer. This shearing also draws field aligned currents from the ionosphere which could inject few KeV heavy ionospheric ions into the magnetotail.

  7. Two substorm studies of relations between westward electric fields in the outer plasmasphere, auroral activity, and geomagnetic perturbations

    NASA Technical Reports Server (NTRS)

    Carpenter, D. L.; Akasofu, S.

    1972-01-01

    Temporal variations of the westward component of the magnetospheric convection electric field in the outer plasmasphere were compared to auroral activity near L = 7, and to variations in the geomagnetic field at middle and high latitudes. The substorms occurred on July 29, 1965 near 0530 UT and on August 20, 1965 near 0730 UT. The results on westward electric field E(w) were obtained by the whistler method using data from Eights, Antarctica (L is approximately 4). All sky camera records were obtained from Byrd, Antarctica, (L is approximately 7), located within about 1 hour of Eights in magnetic local time. It was found that E(w) within the outer plasmasphere increased rapidly to substorm levels about the time of auroral expansion at nearby longitudes. This behavior is shown to differ from results on E(w) from balloons, which show E(w) reaching enhanced levels prior to the expansion. A close temporal relation was found between the rapid, substorm associated increases in E(w) and a well known type of nightside geomagnetic perturbation. Particularly well defined was the correlation of E(w) rise and a large deviation of the D component at middle latitudes.

  8. A statistical relationship between the geosynchronous magnetic field and substorm electrojet magnitude

    NASA Technical Reports Server (NTRS)

    Lopez, Ramon E.; Von Rosenvinge, Tycho

    1993-01-01

    The relationship between the geosynchronous magnetic field variations during substorms measured by GOES 5 and the auroral electroject as measured by AE and Poste de la Baleine is examined. It is found that the more taillike the field prior to the local onset, the greater the dipolarization of the field during the substorm. The greater the deviation of the field from a dipolar configuration, the larger the change in AE during the event. It is inferred that stronger cross-tail currents prior to the substorm are associated with larger substorm-associated westward electrojets and thus more intense substorms. Since the westward electroject is the ionospheric leg of the substorm current wedge, it is inferred that the substorm-associated westward electrojet is drawn from the near-earth region. Most of the current diversion is found to occur in the near-earth magnetotail.

  9. A statistical relationship between the geosynchronous magnetic field and substorm electrojet magnitude

    NASA Technical Reports Server (NTRS)

    Lopez, Ramon E.; Von Rosenvinge, Tycho

    1993-01-01

    The relationship between the geosynchronous magnetic field variations during substorms measured by GOES 5 and the auroral electroject as measured by AE and Poste de la Baleine is examined. It is found that the more taillike the field prior to the local onset, the greater the dipolarization of the field during the substorm. The greater the deviation of the field from a dipolar configuration, the larger the change in AE during the event. It is inferred that stronger cross-tail currents prior to the substorm are associated with larger substorm-associated westward electrojets and thus more intense substorms. Since the westward electroject is the ionospheric leg of the substorm current wedge, it is inferred that the substorm-associated westward electrojet is drawn from the near-earth region. Most of the current diversion is found to occur in the near-earth magnetotail.

  10. Large-scale current systems and ground magnetic disturbance during deep substorm injections

    NASA Astrophysics Data System (ADS)

    Yang, J.; Toffoletto, F. R.; Wolf, R. A.; Sazykin, S.; Ontiveros, P. A.; Weygand, J. M.

    2012-04-01

    also estimate the horizontal and vertical currents using magnetograms at tens of ground stations for a deep injection substorm event occurred on April 9, 2008, resulting in a picture that is qualitatively consistent with the simulation. Based on the simulations and the observations, an overall picture of the ionospheric dynamics and its magnetospheric drivers during deep bubble injections is obtained.

  11. Growth-phase thinning of the near-Earth current sheet during the CDAW 6 substorm

    NASA Technical Reports Server (NTRS)

    Sanny, Jeff; Mcpherron, R. L.; Russell, C. T.; Baker, D. N.; Pulkkinen, T. I.; Nishida, A.

    1994-01-01

    The thinning of the near-Earth current sheet during the growth phase of the Coordinated Data Analysis Workshop (CDAW) 6 magnetospheric substorm is studied. The expansion onset of the substorm occurred at 1054 UT, March 22, 1979. During the growth phase, two spacecraft, International Sun Earth Explorer (ISEE) 1 and ISEE 2, were within the current sheet approximately 13 R(sub E) from the Earth and obtained simultaneous high-resolution magnetic data at two points in the current sheet. Plasma data were also provided by the ISEE spacecraft and solar wind data by IMP 8. To facilitate the analysis, the GSM magnetic field data are transformed to a 'neutral sheet coordinate system' in which the new x axis is parallel to the average magnetic field above and below the neutral sheet and the new y axis lies in the GSM equatorial plane. A model based on the assumption that the current sheet is a time-invariant structure fails to predict neutral sheet crossing times. Consequently, the Harris sheet model, which allows one to remove the restriction of time invariancy, is used instead. It is found that during the growth phase, a model parameter corresponding to the thickness of the current sheet decreased exponentially from about 5 R(sub E) to 1 R(sub E) with a time constant of about 14 min. In addition, the ISEE 1 and ISEE 2 neutral sheet crossings after expansion onset indicate that the neutral sheet was moving upward at 7 km/s relative to the spacecraft. Since both crossings occurred in approximately 80 s, the current sheet thickness is estimated to be about 500 km. These results demonstrate that the near-Earth current sheet undergoes dramatic thinning during the substorm growth phase and expansion onset.

  12. Magnetospheric particle injection and the upstream ion event of September 5, 1984

    NASA Technical Reports Server (NTRS)

    Krimigis, S. M.; Sibeck, D. G.; Mcentire, R. W.

    1986-01-01

    Energetic particle data from the AMPTE Charge Composition Explorer (CCE) spacecraft in the outer dayside magnetosphere are examined during the period of an upstream ion event observed by the AMPTE Ion Release Module (IRM) spacecraft on September 5, 1984. The CCE data reveal the following: (1) an ion enhancement was observed at about 0040 UT in near coincidence with a substorm onset at about 0035 UT, approximately 15 minutes prior to the onset of the event upstream of the shock; (b) ions of both solar-wind - H(2+) Fe-group - and ionospheric O(+) - origin over a broad energy range (about 20 keV to greater than 1350 keV) were injected at substorm onset; (3) the time evolution of the H(+), He(2+), and O(+) pitch angle distributions markedly differed, with O(+) exhibiting mostly enhancements at off-90-deg angles for the first hour after injection; (4) an enhancement in the Fe-group ions inside the magnetosphere at L = about 6.4 occurred simultaneously with the appearance of an O(+) burst upstream of the shock. The CCE observations, taken together with the simultaneously observed IRM ion event, suggest that a plausible explanation for the appearance of upstream ions is leakage from the magnetosphere into the upstream region, rather than the alternative explanation which requires in situ acceleration of solar wind ions via the Fermi Mechanims.

  13. Global Remote Sensing of Precipitating Electron Energies: A Comparison of Substorms and Pressure Pulse Related Intensifications

    NASA Technical Reports Server (NTRS)

    Chua, D.; Parks, G. K.; Brittnacher, M. J.; Germany, G. A.; Spann, J. F.

    2000-01-01

    The Polar Ultraviolet Imager (UVI) observes aurora responses to incident solar wind pressure pulses and interplanetary shocks such its those associated with coronal mass ejections. Previous observations have demonstrated that the arrival of it pressure pulse at the front of the magnetosphere results in highly disturbed geomagnetic conditions and a substantial increase in both dayside and nightside aurora precipitations. Our observations show it simultaneous brightening over bread areas of the dayside and nightside auroral in response to a pressure pulse, indicating that more magnetospheric regions participate as sources for auroral precipitation than during isolate substorm. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated event to those during isolated substorms. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated events to those during isolated auroral substorms. Electron precipitation during substorms has characteristic energies greater than 10 KeV and is structured both in local time and in magnetic latitude. For auroral intensifications following the arrival of'a pressure pulse or interplanetary shock. Electron precipitation is less spatially structured and has greater flux of lower characteristic energy electrons (Echar less than 7 KeV) than during isolated substorm onsets. These observations quantify the differences between global and local auroral precipitation processes and will provide a valuable experimental check for models of sudden storm commencements and magnetospheric response to perturbations in the solar wind.

  14. Global Remote Sensing of Precipitating Electron Energies: A Comparison of Substorms and Pressure Pulse Related Intensifications

    NASA Technical Reports Server (NTRS)

    Chua, D.; Parks, G. K.; Brittnacher, M. J.; Germany, G. A.; Spann, J. F.

    2000-01-01

    The Polar Ultraviolet Imager (UVI) observes aurora responses to incident solar wind pressure pulses and interplanetary shocks such its those associated with coronal mass ejections. Previous observations have demonstrated that the arrival of it pressure pulse at the front of the magnetosphere results in highly disturbed geomagnetic conditions and a substantial increase in both dayside and nightside aurora precipitations. Our observations show it simultaneous brightening over bread areas of the dayside and nightside auroral in response to a pressure pulse, indicating that more magnetospheric regions participate as sources for auroral precipitation than during isolate substorm. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated event to those during isolated substorms. We estimate the characteristic energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated events to those during isolated auroral substorms. Electron precipitation during substorms has characteristic energies greater than 10 KeV and is structured both in local time and in magnetic latitude. For auroral intensifications following the arrival of'a pressure pulse or interplanetary shock. Electron precipitation is less spatially structured and has greater flux of lower characteristic energy electrons (Echar less than 7 KeV) than during isolated substorm onsets. These observations quantify the differences between global and local auroral precipitation processes and will provide a valuable experimental check for models of sudden storm commencements and magnetospheric response to perturbations in the solar wind.

  15. Reconnection in substorms and solar flares: analogies and differences

    SciTech Connect

    Birn, Joachim

    2008-01-01

    Magnetic reconnection is the crucial process in the release of magnetic energy associated with magnetospheric substorms and with solar flares. On the basis of three-dimensional resistive MHD simulations we investigate similarities and differences between the two scenarios. We address in particular mechanisms that lead to the onset of reconnection and on energy release, transport, and conversion mechanisms. Analogous processes might exist in the motion of field line footpoints on the sun and in magnetic flux addition to the magnetotail. In both cases such processes might lead to a loss of neighboring equilibrium, characterized by the formation of very thin embedded current sheet, which acts as trigger for reconnection. We find that Joule (or ohmic) dissipation plays only a minor role in the overall energy transfer associated with reconnection. The dominant transfer of released magnetic energy occurs to electromagnetic energy (Poynting) flux and to thermal energy transport as enthalpy flux. The former dominates in low-beta, specifically initially force-free current sheets expected for the solar corona, while the latter dominates in high-beta current sheets, such as the magnetotail. In both cases the outflow from the reconnection site becomes bursty, i.e. spatially and temporally localized, yet carrying most of the outflow energy. Hence an analogy might exist between bursty bulk flows (BBFs) in the magnetotail and pulses of Poynting flux in solar flares.

  16. Diurnal double maxima patterns in the F region ionosphere: Substorm-related aspects

    SciTech Connect

    Pi, X.; Mendillo, M.; Fox, M.W.; Anderson, D.N.

    1993-08-01

    Daytime double maxima (twin peaks or bite-outs) in the ionospheric total electron content (TEC) at middle and lower latitudes are found to be related to substorm signatures shown in both auroral electrojet and ring current variations. Case studies reveal that during substorm onset and recovery phases, the penetration of magnetospheric convection electric fields and their subsequent {open_quotes}overshielding{close_quotes} effects may be the major dynamical sources of these events. A theoretical low-latitude ionospheric model is used to simulate the dynamical effects of electric field disturbances on F region electron density and TEC. It is demonstrated that the diurnal double maxima in TEC can be created by a combined effect of E x B drift and altitude-dependent F region chemical loss. The required zonal electric fields are found to have greater penetration efficiency in the early evening sector and their latitudinal requirements appear to change with local time. The time scales for the modeled penetration and overshielding effects are 2-3 hours. Modeling results also show that considerable structuring in the local time variation of the ionospheric {open_quotes}equatorial anomaly{close_quotes} can occur due to the interplay of convection electric field penetration and overshielding effects. The possible cause of the midday bite-out ionospheric disturbances by the meridional winds associated with traveling atmospheric disturbances (TADs) is also addressed in modeling studies, but the specialized nature of the required TADs makes this a less well understood substorm-related mechanism. 64 refs., 14 figs., 3 tabs.

  17. Solar Wind Drivers for Steady Magnetospheric Convection

    NASA Technical Reports Server (NTRS)

    McPherron, Robert L.; O'Brien, T. Paul; Thompson, Scott; Lui, A. T. Y. (Editor)

    2005-01-01

    Steady magnetospheric convection (SMC) also known as convection bays, is a particular mode of response of the magnetosphere to solar wind coupling. It is characterized by convection lasting for times longer than a typical substorm recovery during which no substorms expansions can be identified. It is generally believed that the solar wind must be unusually steady for the magnetosphere to enter this state. However, most previous studies have assumed this is true and have used such conditions to identify events. In a preliminary investigation using only the AE and AL indices to select events we have shown that these expectations are generally correct. SMC events seem to be associated with slow speed solar wind and moderate, stable IMF Bz. In this report we extend our previous study including additional parameters and the time variations in various statistical quantities. For the intervals identified as SMCs we perform a detailed statistical analysis of the properties of different solar wind variables. We compare these statistics to those determined from all data, and from intervals in which substorms but not SMCs are present. We also consider the question of whether substorms are required to initiate and terminate an SMC. We conclude that the intervals we have identified as SMC are likely to be examples of the original Dungey concept of balanced reconnection at a pair of x-lines on the day and night side of the Earth.

  18. Solar Wind Drivers for Steady Magnetospheric Convection

    NASA Technical Reports Server (NTRS)

    McPherron, Robert L.; O'Brien, T. Paul; Thompson, Scott; Lui, A. T. Y. (Editor)

    2005-01-01

    Steady magnetospheric convection (SMC) also known as convection bays, is a particular mode of response of the magnetosphere to solar wind coupling. It is characterized by convection lasting for times longer than a typical substorm recovery during which no substorms expansions can be identified. It is generally believed that the solar wind must be unusually steady for the magnetosphere to enter this state. However, most previous studies have assumed this is true and have used such conditions to identify events. In a preliminary investigation using only the AE and AL indices to select events we have shown that these expectations are generally correct. SMC events seem to be associated with slow speed solar wind and moderate, stable IMF Bz. In this report we extend our previous study including additional parameters and the time variations in various statistical quantities. For the intervals identified as SMCs we perform a detailed statistical analysis of the properties of different solar wind variables. We compare these statistics to those determined from all data, and from intervals in which substorms but not SMCs are present. We also consider the question of whether substorms are required to initiate and terminate an SMC. We conclude that the intervals we have identified as SMC are likely to be examples of the original Dungey concept of balanced reconnection at a pair of x-lines on the day and night side of the Earth.

  19. Substorm occurrence during quiet solar wind driving

    NASA Astrophysics Data System (ADS)

    Pulkkinen, T. I.; Partamies, N.; Kilpua, E. K. J.

    2014-04-01

    We examine the OMNI database and International Monitor for Auroral Geomagnetic Effects (IMAGE) magnetometer chain records to study the substorm occurrence and characteristics during quiet solar driving periods, especially during the solar minimum period in 2009. We define substorm-like activations as periods where the hourly average AL is below -200 nT. Using the OMNI data set, we demonstrate that there are limiting solar wind speed, interplanetary magnetic field magnitude, and driving electric field values below which substorm-like activations (AL < 200 nT, intensification and decay of the electrojet) do not occur. These minimum parameter values are V < 266 km/s, B < 1.4 nT, and E < 0.025 mV/m such low values are observed less than 1% of the time. We also show that for the same level of driving solar wind electric field, the electrojet intensity is smaller (by few tens of nT), and the electrojet resides farther poleward (by over 1°) during extended quiet solar driving in 2009 than during average solar activity conditions. During the solar minimum period in 2009, we demonstrate that substorm-like activations can be identified from the IMAGE magnetometer chain observations during periods when the hourly average IL index is below -100 nT. When the hourly IL activity is smaller than that, which covers 87% of the nighttime observations, the electrojet does not show coherent behavior. We thus conclude that substorm recurrence time during very quiet solar wind driving conditions is about 5-8 h, which is almost double that of the average solar activity conditions.

  20. Observing the magnetosphere through auroral imaging.

    NASA Astrophysics Data System (ADS)

    Mende, S. B.

    2015-12-01

    Although the terrestrial aurora is often regarded as 2 dimensional projection of the 3 dimensional magnetosphere there are fundamental limitations in observing magnetospheric processes through their auroral footprints. It has been shown that most electron auroras are produced in the auroral acceleration region at lower altitudes (<2Re) in the last steps of processing the auroral particles. From FAST, IMAGE , Cluster and THEMIS data we can distinguish between four fundamentally different types of auroral acceleration regions. A primary task is to distinguish (1) the upward current, (2) downward current, (3) diffuse aurora and (4) Alfven wave accelerated types of auroral acceleration regions. Type (1) contains the "inverted V" type electron precipitation distinguishable by several keV mono-energetic electron spectra, and low number flux consistent with the source population in the plasma sheet. Our understanding of how these auroras relate to magnetospheric processes is still vague, probably associated with convection sheer. Alfven wave electron auroras (4) are of low average energy (<2 keV) high electron flux consistent with ionospheric electron source predominantly occurring during substorms, and they are generated by wave energy carried from the magnetosphere into the ionosphere, where it is converted into electron energy. These are most promising candidates for observing the footprints of source regions associated with reconnection sites or magnetospheric dB/dt events. Optical measuring techniques of electron energy use the atmosphere as a spectrometer, obtaining the penetration altitude as a proxy for energy, that can be obtained from atmospheric composition, quenching lifetime of the emitters, UV absorption pass-length of O2 to the source or the local atmospheric temperature. Precipitating protons are usually an order of magnitude more energetic and less affected by fields in the low altitude auroral acceleration region. Energetic proton precipitation is a more

  1. Magnetospheric electric fields and currents

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.; Zanetti, L. J.

    1987-01-01

    The progress made in the years 1983-1986 in understanding the character and operation of magnetospheric electric fields and electric currents is discussed, with emphasis placed on the connection with the interior regions. Special attention is given to determinations of global electric-field configurations, measurements of the response of magnetospheric particle populations to the electric-field configurations, and observations of the magnetospheric currents at high altitude and during northward IMF. Global simulations of current distributions are discussed, and the sources of global electric fields and currents are examined. The topics discussed in the area of impulsive and small-scale phenomena include substorm current systems, impulsive electric fields and associated currents, and field-aligned electrodynamics. A key finding of these studies is that the electric fields and currents are interrelated and cannot be viewed as separate entities.

  2. Electric currents of a substorm current wedge on 24 February 2010

    NASA Astrophysics Data System (ADS)

    Connors, Martin; McPherron, Robert L.; Anderson, Brian J.; Korth, Haje; Russell, Christopher T.; Chu, Xiangning

    2014-07-01

    The three-dimensional "substorm current wedge" (SCW) was postulated by McPherron et al. (1973) to explain substorm magnetic perturbations. The origin and coherence as a physical system of this important paradigm of modern space physics remained unclear, however, with progress hindered by gross undersampling, and uniqueness problems in data inversion. Complementing AMPERE (Active Magnetosphere and Planetary Electrodynamics Response Experiment) space-derived radial electric currents with ground magnetic data allowing us to determine currents from the ionosphere up, we overcome problems of uniqueness identified by Fukushima (1969, 1994). For a substorm on 24 February 2010, we quantify SCW development consistently from ground and space data. Its westward electrojet carries 0.5 MA in the more poleward part of the auroral oval, in Region 1 (R1) sense spanning midnight. The evening sector electrojet also feeds into its upward current. We thus validate the SCW concept and obtain parameters needed for quantitative study of substorms.

  3. A nonlinear dynamic analogue model of substorms

    NASA Astrophysics Data System (ADS)

    Klimas, A. J.; Baker, D. N.; Roberts, D. A.; Fairfield, D. H.; Büchner, J.

    Linear prediction filter studies have shown that the magnetospheric response to energy transfer from the solar wind contains both directly driven and unloading components. These studies have also shown that the magnetospheric response is significantly nonlinear and, thus, the linear prediction filtering technique and other correlative techniques which assume a linear magnetospheric response cannot give a complete deacription of that response. Here, the solar wind-magnetosphere interaction is discussed within the framework of deterministic nonlinear dynamics. An earlier dripping faucet mechanical analogue to the magnetosphere is first reviewed and then the plasma physical counterpart to the mechanical model is constructed. A Faraday loop in the magnetotail is considered and the relationship of electric potentials on the loop to changes in the magnetic flux threading the loop is developed. This approach leads to a model of geomagnetic activity which is similar to the earlier mechanical model but described in terms of the geometry and plasma contents of the magnetotail. This Faraday loop response model contains analogues to both the directly driven and the storage-release magnetospheric responses and it includes, in a fundamental way, the inherent nonlinearity of the solar wind-magnetosphere system. It can be chancterized as a nonlinear, damped harmonic oscillator that is driven by the loading-unloading substorm cycle. The model is able to explain many of the features of the linear prediction filter results. In particular, at low geomagnetic activity levels the model exbibits the "regular dripping" response which provides an explanation for the unloading component at 1 hour lag in the linear prediction filters. Further, the model suggests that the disappearance of the unloading component in the linear prediction filters at high geomagnetic activity levels is due to a chaotic transition beyond which the loading-unloading mechanism becomes aperiodic. The model predicts

  4. Studies of Westward Electrojets and Field-Aligned Currents in the Magnetotail during Substorms: Implications for Magnetic Field Models

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Our studies elucidated the relationship between the auroral arcs and magnetotail phenomena. One paper examined particle energization in the source region of the field-aligned currents that intensify at substorm onset when the arc brightens to form the westward electrojet. A second paper examined the relationship between the precipitating particles in the arcs, the location of the westward electrojet, and magnetospheric source regions. Two earlier papers also investigated the roles that field aligned currents and particle acceleration have during substorms.

  5. Electrodynamics of convection in the inner magnetosphere

    NASA Technical Reports Server (NTRS)

    Spiro, R. W.; Wolf, R. A.

    1984-01-01

    During the past ten years, substantial progress has been made in the development of quantitative models of convection in the magnetosphere and of the electrodynamic processes that couple that magnetosphere and ionosphere. Using a computational scheme first proposed by Vasyliunas, the convection models under consideration separate the three-dimensional problem of convection in the inner magnetosphere/ionosphere into a pair of two-dimensional problems coupled by Birkeland currents flowing between the two regions. The logic, development, and major results of the inner magnetosphere convection model are reviewed with emphasis on ionospheric and magnetospheric currents. A major theoretical result of the models has been the clarification of the relationship between the region 1/region 2 picture of field-aligned currents and the older partial ring current/tail current interruption picture of substorm dynamics.

  6. CDAW 7 revisited - Further evidence for the creation of a near-earth substorm neutral line. [Coordinated Data Analysis Workshop

    NASA Technical Reports Server (NTRS)

    Kettmann, G.; Fritz, T. A.; Hones, E. W., Jr.

    1990-01-01

    Eastman et al. (1988) have interpreted the CDAW 7 substorm of April 24, 1979, previously taken as unambiguously supporting the near-earth neutral line model of magnetospheric substorms, in terms of spatial movements of a preexisting plasma-sheet boundary layer (PSBL) and its associated current sheets across the observing ISEE 1 and 2 spacercraft. It is presently noted that, by contrast, a reinvestigation of ISEE 1 and 2 energetic particle measurements around substorm onset on short time-scales shows the observed flux pattern to require the formation of a particle source eastward of the ISEE spacecraft, well within the plasma sheet, associated with the substorm onset. Strong flows were absent prior to substorm onset, indicating the temporal nature of the event, as opposed to an encounter with a preexisting PSBL containing large flows.

  7. Energetic electron precipitation and auroral morphology at the substorm recovery phase

    NASA Astrophysics Data System (ADS)

    Oyama, S.; Kero, A.; Rodger, C. J.; Clilverd, M. A.; Miyoshi, Y.; Partamies, N.; Turunen, E.; Raita, T.; Verronen, P. T.; Saito, S.

    2017-06-01

    It is well known that auroral patterns at the substorm recovery phase are characterized by diffuse or patch structures with intensity pulsation. According to satellite measurements and simulation studies, the precipitating electrons associated with these aurorae can reach or exceed energies of a few hundreds of keV through resonant wave-particle interactions in the magnetosphere. However, because of difficulty of simultaneous measurements, the dependency of energetic electron precipitation (EEP) on auroral morphological changes in the mesoscale has not been investigated to date. In order to study this dependency, we have analyzed data from the European Incoherent Scatter (EISCAT) radar, the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) riometer, collocated cameras, ground-based magnetometers, the Van Allen Probe satellites, Polar Operational Environmental Satellites (POES), and the Antarctic-Arctic Radiation-belt (Dynamic) Deposition-VLF Atmospheric Research Konsortium (AARDDVARK). Here we undertake a detailed examination of two case studies. The selected two events suggest that the highest energy of EEP on those days occurred with auroral patch formation from postmidnight to dawn, coinciding with the substorm onset at local midnight. Measurements of the EISCAT radar showed ionization as low as 65 km altitude, corresponding to EEP with energies of about 500 keV.Plain Language SummaryAurora is emission of the atmospheric particles excited by electrons coming from the <span class="hlt">magnetosphere</span>. The electrons have energies of 1-10 keV or higher. In particular, it is known that the energy can increase more than 100 keV in association with the pulsating aurora and that morphology of the pulsating aurora changes with time. However, relationships between the energy increase and the morphological change have not been studied well. This study analyzed the ionospheric density and auroral images and found that significant increases</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120012572&hterms=time+space&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dtime%2Bspace','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120012572&hterms=time+space&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dtime%2Bspace"><span>From Space Weather Toward Space Climate Time Scales: <span class="hlt">Substorm</span> Analysis from 1993 to 2008</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tanskanen, E. I.; Pulkkinen, T. I.; Viljanen, A.; Partamies, N.; Slavin, J. A.</p> <p>2011-01-01</p> <p>Magnetic activity in the Northern Hemisphere auroral region was examined during solar cycles 22 and 23 (1993- 2008). <span class="hlt">Substorms</span> were identified from ground-based magnetic field measurements by an automated search engine. On average, 550 <span class="hlt">substorms</span> were observed per year, which gives in total about 9000 <span class="hlt">substorms</span>. The interannual, seasonal and solar cycle-to-cycle variations of the <span class="hlt">substorm</span> number (R(sub ss)), <span class="hlt">substorm</span> duration (T(sub ss)), and peak amplitude (A(sub ss)) were examined. The declining phases of both solar cycles 22 and 23 were more active than the other solar cycle phases due to the enhanced solar wind speed. The spring <span class="hlt">substorms</span> during the declining solar cycle phase (absolute value of A(sub ss,decl)) - 500 nT) were 25% larger than the spring <span class="hlt">substorms</span> during the ascending solar cycle years ((absolute value of A(sub ss,asc) = 400 nT). The following seasonal variation was found: the most intense <span class="hlt">substorms</span> <span class="hlt">occurred</span> during spring and fall, the largest <span class="hlt">substorm</span> frequency in the Northern Hemisphere winter, and the longest-duration <span class="hlt">substorms</span> in summer. Furthermore, we found a winter-summer asymmetry in the <span class="hlt">substorm</span> number and duration. which is speculated to be due to the variations in the ionospheric conductivity. The solar cycle-Io-cycle variation was found in the yearly <span class="hlt">substorm</span> number and peak amplitude. The decline from the peak <span class="hlt">substorm</span> activity in 1994 and 2003 to the following minima took 3 years during solar cycle 22, while it took 6 years during solar cycle 23.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM44A..09M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM44A..09M"><span>In-situ measurement of the <span class="hlt">substorm</span> onset instability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murphy, K. R.; Rae, J.; Watt, C.; Forsyth, C.; Mann, I. R.; Yao, Z.; Kalmoni, N.</p> <p>2015-12-01</p> <p>The <span class="hlt">substorm</span> is arguably the major mode of variability in near-Earth Space which unpredictably dissipates a considerable and variable amount of energy into the near-Earth <span class="hlt">magnetosphere</span> and ionosphere. What process or processes determine when this energy is released is uncertain, although it is evident that both near-Earth plasma instability and magnetotail reconnection play a role in this energy release. Much emphasis has recently been placed on the role of magnetic reconnection in <span class="hlt">substorms</span>, we focus here on observations of the unmistakeable signs of a plasma instability acting at <span class="hlt">substorm</span> onset. Using data from the THEMIS spacecraft, we show that electromagnetic waves grow in the magnetotail at the expense of the local electron and ion thermal energy. The wave growth in space is the direct counterpart to the wave growth seen at the <span class="hlt">substorm</span> onset location at the ionosphere, as measured by the CARISMA and THEMIS magnetometers and THEMIS all-sky-imagers. We present evidence that the free energy source for the instability is associated with the electron and ion thermal energy, and not the local electron or ion flow energy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.9834C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.9834C"><span>A superposed epoch analysis of the regions 1 and 2 Birkeland currents observed by AMPERE during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Coxon, J. C.; Milan, S. E.; Clausen, L. B. N.; Anderson, B. J.; Korth, H.</p> <p>2014-12-01</p> <p>We perform a superposed epoch analysis of the evolution of the Birkeland currents (field-aligned currents) observed by the Active <span class="hlt">Magnetosphere</span> and Planetary Electrodynamics Response Experiment (AMPERE) during <span class="hlt">substorms</span>. The study is composed of 2900 <span class="hlt">substorms</span> provided by the SuperMAG experiment. We find that the current ovals expand and contract over the course of a <span class="hlt">substorm</span> cycle and that currents increase in magnitude approaching <span class="hlt">substorm</span> onset and are further enhanced in the expansion phase. Subsequently, we categorize the <span class="hlt">substorms</span> by their onset latitude, a proxy for the amount of open magnetic flux in the <span class="hlt">magnetosphere</span>, and find that Birkeland currents are significantly higher throughout the epoch for low-latitude <span class="hlt">substorms</span>. Our results agree with previous studies which indicate that <span class="hlt">substorms</span> are more intense and close more open magnetic flux when the amount of open flux is larger at onset. We place these findings in the context of previous work linking dayside and nightside reconnection rate to Birkeland current strengths and locations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780002197','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780002197"><span>Nuclear burst plasma injection into the <span class="hlt">magnetosphere</span> and resulting spacecraft charging</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pavel, A. L.; Cipolla, J. A.; Silevitch, M. B.; Golden, K. I.</p> <p>1977-01-01</p> <p>The passage of debris from a high altitude ( 400 km) nuclear burst over the ionospheric plasma is found to be capable of exciting large amplitude whistler waves which can act to structure a collisionless shock. This instability will <span class="hlt">occur</span> in the loss cone exits of the nuclear debris bubble, and the accelerated ambient ions will freestream along the magnetic field lines into the <span class="hlt">magnetosphere</span>. Using Starfish-like parameters and accounting for plasma diffusion and thermalization of the propagating plasma mass, it is found that synchronous orbit plasma fluxes of high temperature electrons (near 10 keV) will be significantly greater than those encountered during <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>. These fluxes will last for sufficiently long periods of time so as to charge immersed bodies to high potentials and arc discharges to take place.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007SSRv..131..133S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007SSRv..131..133S"><span>MESSENGER: Exploring Mercury's <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slavin, James A.; Krimigis, Stamatios M.; Acuña, Mario H.; Anderson, Brian J.; Baker, Daniel N.; Koehn, Patrick L.; Korth, Haje; Livi, Stefano; Mauk, Barry H.; Solomon, Sean C.; Zurbuchen, Thomas H.</p> <p>2007-08-01</p> <p>The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury offers our first opportunity to explore this planet’s miniature <span class="hlt">magnetosphere</span> since the brief flybys of Mariner 10. Mercury’s <span class="hlt">magnetosphere</span> is unique in many respects. The <span class="hlt">magnetosphere</span> of Mercury is among the smallest in the solar system; its magnetic field typically stands off the solar wind only ˜1000 to 2000 km above the surface. For this reason there are no closed drift paths for energetic particles and, hence, no radiation belts. Magnetic reconnection at the dayside magnetopause may erode the subsolar <span class="hlt">magnetosphere</span>, allowing solar wind ions to impact directly the regolith. Inductive currents in Mercury’s interior may act to modify the solar wind interaction by resisting changes due to solar wind pressure variations. Indeed, observations of these induction effects may be an important source of information on the state of Mercury’s interior. In addition, Mercury’s <span class="hlt">magnetosphere</span> is the only one with its defining magnetic flux tubes rooted beneath the solid surface as opposed to an atmosphere with a conductive ionospheric layer. This lack of an ionosphere is probably the underlying reason for the brevity of the very intense, but short-lived, ˜1-2 min, <span class="hlt">substorm</span>-like energetic particle events observed by Mariner 10 during its first traversal of Mercury’s magnetic tail. Because of Mercury’s proximity to the sun, 0.3-0.5 AU, this <span class="hlt">magnetosphere</span> experiences the most extreme driving forces in the solar system. All of these factors are expected to produce complicated interactions involving the exchange and recycling of neutrals and ions among the solar wind, <span class="hlt">magnetosphere</span>, and regolith. The electrodynamics of Mercury’s <span class="hlt">magnetosphere</span> are expected to be equally complex, with strong forcing by the solar wind, magnetic reconnection, and pick-up of planetary ions all playing roles in the generation of field-aligned electric currents. However, these field</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060013125','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060013125"><span>MESSENGER: Exploring Mercury's <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slavin, James A.; Krimigis, Stamatios M.; Acuna, Mario H.; Anderson, Brian J.; Baker, Daniel N.; Koehn, Patrick L.; Korth, Haje; Levi, Stefano; Mauk, Barry H.; Solomon, Sean C.; Zurbuchen, Thomas H.</p> <p>2005-01-01</p> <p>The MESSENGER mission to Mercury offers our first opportunity to explore this planet s miniature <span class="hlt">magnetosphere</span> since the brief flybys of Mariner 10. Mercury s <span class="hlt">magnetosphere</span> is unique in many respects. The <span class="hlt">magnetosphere</span> of Mercury is among the smallest in the solar system; its magnetic field typically stands off the solar wind only - 1000 to 2000 km above the surface. For this reason there are no closed drift paths for energetic particles and, hence, no radiation belts. The characteristic time scales for wave propagation and convective transport are short and kinetic and fluid modes may be coupled. Magnetic reconnection at the dayside magnetopause may erode the subsolar <span class="hlt">magnetosphere</span> allowing solar wind ions to impact directly the regolith. Inductive currents in Mercury s interior may act to modify the solar wind interaction by resisting changes due to solar wind pressure variations. Indeed, observations of these induction effects may be an important source of information on the state of Mercury s interior. In addition, Mercury s <span class="hlt">magnetosphere</span> is the only one with its defining magnetic flux tubes rooted in a planetary regolith as opposed to an atmosphere with a conductive ionospheric layer. This lack of an ionosphere is probably the underlying reason for the brevity of the very intense, but short-lived, - 1-2 min, <span class="hlt">substorm</span>-like energetic particle events observed by Mariner 10 during its first traversal of Mercury s magnetic tail. Because of Mercury s proximity to the sun, 0.3 - 0.5 AU, this <span class="hlt">magnetosphere</span> experiences the most extreme driving forces in the solar system. All of these factors are expected to produce complicated interactions involving the exchange and re-cycling of neutrals and ions between the solar wind, <span class="hlt">magnetosphere</span>, and regolith. The electrodynamics of Mercury s <span class="hlt">magnetosphere</span> are expected to be equally complex, with strong forcing by the solar wind, magnetic reconnection at the magnetopause and in the tail, and the pick-up of planetary ions all</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910030166&hterms=IRM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DIRM','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910030166&hterms=IRM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DIRM"><span>Multipoint observations of a small <span class="hlt">substorm</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lopez, R. E.; Anderson, B. J.; Newell, P. T.; Mcentire, R. W.; Luehr, H.</p> <p>1990-01-01</p> <p>Results are presented of multipoint observations of a small <span class="hlt">substorm</span> which <span class="hlt">occurred</span> at about 0110 UT on April 25, 1985, carried out by AMPTE CCE, AMPTE IRM, DMSP F6, and DMSP F7, as well as by ground auroral stations and midlatitude stations. These data yield information on the latitudinal extent of the polar cap and provide visual identification of <span class="hlt">substorm</span> aurorae, magnetic perturbations produced directly beneath aurorae, and the situ magnetic field. In addition, they provide magnetic-particle observations of the disruption of the cross-tail current sheet and observations concerning the spatial expansion of the current disruption region. Evidence is presented that the current sheet disruption observed by CCE in the neutral sheet was located on field lines which mapped to the westward traveling surge observed directly overhead of the ground station at Syowa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910030166&hterms=observation+identification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dobservation%2Bidentification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910030166&hterms=observation+identification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dobservation%2Bidentification"><span>Multipoint observations of a small <span class="hlt">substorm</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lopez, R. E.; Anderson, B. J.; Newell, P. T.; Mcentire, R. W.; Luehr, H.</p> <p>1990-01-01</p> <p>Results are presented of multipoint observations of a small <span class="hlt">substorm</span> which <span class="hlt">occurred</span> at about 0110 UT on April 25, 1985, carried out by AMPTE CCE, AMPTE IRM, DMSP F6, and DMSP F7, as well as by ground auroral stations and midlatitude stations. These data yield information on the latitudinal extent of the polar cap and provide visual identification of <span class="hlt">substorm</span> aurorae, magnetic perturbations produced directly beneath aurorae, and the situ magnetic field. In addition, they provide magnetic-particle observations of the disruption of the cross-tail current sheet and observations concerning the spatial expansion of the current disruption region. Evidence is presented that the current sheet disruption observed by CCE in the neutral sheet was located on field lines which mapped to the westward traveling surge observed directly overhead of the ground station at Syowa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JGRA..115.7205S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JGRA..115.7205S"><span>Ionospheric feedback instability and <span class="hlt">substorm</span> development</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Streltsov, A. V.; Pedersen, T. R.; Mishin, E. V.; Snyder, A. L.</p> <p>2010-07-01</p> <p>We report on ground magnetic and optical observations performed during an ionospheric heating experiment at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska on 29 October 2008. The experiment was aimed at generation of large-amplitude ULF electromagnetic waves by triggering and facilitating development of the ionospheric feedback instability (IFI) in the region adjacent to a bright auroral arc. In this region the downward/return magnetic field-aligned current decreases plasma density and enhances the electric field in the ionosphere. A combination of these two effects creates favorable conditions for the instability. The experiment <span class="hlt">occurred</span> during a period of <span class="hlt">substorm</span> activity, but effects from the HAARP transmitter were not sufficiently intense to be detected against the background of strong natural oscillations <span class="hlt">occurring</span> farther north from the HAARP site. Thus the experiment did not provide concrete evidence that heating of the ionosphere with powerful HF transmitters can affect IFI development or generate intense ULF electromagnetic waves. However, during the experiment ground-based magnetometers in Alaska and Canada detected large-amplitude ULF waves in regions where the <span class="hlt">substorm</span> onset auroral arcs interacted with the ionosphere. The frequencies of these waves closely matched frequencies predicted by simulations of IFI for these particular geophysical conditions. These observations support the hypothesis that geomagnetic <span class="hlt">substorms</span>, the corresponding dynamics of discrete auroral arcs, and the ionospheric feedback instability are closely connected phenomena.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790062404&hterms=electrodynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Delectrodynamics','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790062404&hterms=electrodynamics&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Delectrodynamics"><span>The electric field and global electrodynamics of the <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stern, D. P.</p> <p>1979-01-01</p> <p>The conception of the electrodynamics of the quiet-time <span class="hlt">magnetosphere</span> obtained during the last four years of <span class="hlt">magnetospheric</span> study is presented. Current understandings of the open <span class="hlt">magnetosphere</span>, convective plasma flows in the plasma sheet, the shielding of the inner <span class="hlt">magnetosphere</span> from the convective <span class="hlt">magnetospheric</span> electric field, the space charge produced when injected electrons drift towards dawn and injected ions drift towards dusk, the disruption of the flow of the Birkeland current by plasma instabilities and the shielding of the convective electric field by the dayside magnetopause are discussed. Attention is also given to changes of magnetic field line topology magnetic storms and <span class="hlt">substorms</span>. Unresolved questions and new tools which may play a role in the further understanding of <span class="hlt">magnetospheric</span> electrodynamics and the role of the <span class="hlt">magnetospheric</span> electric field are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM11B2091C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM11B2091C"><span>Flow Pattern relative to the <span class="hlt">Substorm</span> Current Wedge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, X.; McPherron, R. L.; Hsu, T.</p> <p>2013-12-01</p> <p><span class="hlt">Magnetospheric</span> <span class="hlt">substorms</span> play a key role in the coupling of the solar wind and the <span class="hlt">magnetosphere</span>. The <span class="hlt">Substorm</span> Current Wedge (SCW) is a key element in the present physical model of <span class="hlt">substorms</span>. It is widely accepted that the SCW is created by earthward busty flows, but the generation mechanism is still unknown. Previous studies suggest pressure gradients and magnetic vortices are possible candidates. Due to the sparse coverage of satellites in space, these studies were strongly dependent on the assumption that the satellites were in the generation region of the field-aligned currents (FAC) forming the SCW. In this work, we take advantage of an inversion technique that determines the parameters describing the SCW and perform a statistical study on the plasma and magnetic field parameters of the flow pattern relative to the SCW. The inversion technique finds the location and the intensity of the SCW from midlatitude magnetic data. The technique has been validated using auroral observations, Equivalent Ionospheric Currents (EIC), SYM-H index from SuperMAG, and magnetic perturbations at geosynchronous orbit by the GOES satellite. A database of <span class="hlt">substorm</span> events has been created using midlatitude positive bays, which are the ground signature of the SCW at lower latitudes. The inversion technique is applied to each event in the database to determine the location of the origin of the SCW. The inversion results are also used to find conjunction events with space observations from VAP (RBSP), THEMIS and GOES. The plasma and magnetic field parameters such as the pressure gradient and magnetic vorticity are then categorized as a function of their location relative to the origin of the SCW. How the distribution/pattern of the pressure gradient and vorticity are related to the properties of the SCW (locations and intensity of the FAC), and flows (entropy, velocity and density) will be determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM23A2216H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM23A2216H"><span>Time development of high-altitude auroral acceleration region plasma, potentials, and field-aligned current systems observed by Cluster during a <span class="hlt">substorm</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hull, A. J.; Chaston, C. C.; Fillingim, M. O.; Mozer, F.; Frey, H. U.</p> <p>2013-12-01</p> <p>The auroral acceleration region is an integral link in the chain of events that transpire during <span class="hlt">substorms</span>, and the currents, plasma and electric fields undergo significant changes driven by complex dynamical processes deep in the magnetotail. These auroral acceleration processes in turn accelerate and heat the plasma that ultimately leads to some of the most intense global <span class="hlt">substorm</span> auroral displays. The complex interplay between field-aligned current system formation, the development of parallel electric fields, and resultant changes in the plasma constituents that <span class="hlt">occur</span> during <span class="hlt">substorms</span> within or just above the auroral acceleration zone remain unclear. We present Cluster multi-point observations within the high-altitude acceleration region (> 3 Re altitude) at key instances during the development of a <span class="hlt">substorm</span>. Of particular emphasis is on the time-development of the plasma, potentials and currents that <span class="hlt">occur</span> therein with the aim of ascertaining high-altitude drivers of <span class="hlt">substorm</span> active auroral acceleration processes and auroral emission consequences. Preliminary results show that the initial onset is dominated by Alfvenic activity as evidenced by the sudden occurrence of relatively intense, short-spatial scale Alfvenic currents and attendant energy dispersed, counterstreaming electrons poleward of the growth-phase arc. The Alfvenic currents are locally planar structures with characteristic thicknesses on the order of a few tens of kilometers. In subsequent passages by the other spacecraft, the plasma sheet region became hotter and thicker via the injection of new hot, dense plasma of <span class="hlt">magnetospheric</span> origins poleward of the pre-existing growth phase arc. In association with the heating and/or thickening of the plasma sheet, the currents appeared to broaden to larger scales as Alfven dominated activity gave way to either inverted-V dominated or mixed inverted-V and Alfvenic behavior depending on location. The transition from Alfven dominated to inverted-V dominated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMSM51B0534K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMSM51B0534K"><span>Relative Order of Auroral Transient Structure During <span class="hlt">Substorm</span> Activation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kozelov, B. V.; Rypdal, K.</p> <p>2007-12-01</p> <p>Variability of auroral structures is a manifestation of the <span class="hlt">magnetosphere</span>-ionosphere plasma dynamics. During the last decade the complexity of <span class="hlt">magnetosphere</span>-ionosphere plasma has been widely discussed in numerous papers. The most popular approaches are based on turbulence or/and self-organized criticality paradigms. However, there is no clear evidence that the dynamics during the discussed events is really organization, and not disorganization. The problem is that the <span class="hlt">magnetosphere</span>-ionosphere system is an open non-equilibrium system, therefore classical thermodynamics is not directly applicable. Here we use an approach based on the S-theorem by Yu.L. Klimontovich. This approach allows us to compare the ordering which characterize the current (non- equilibrium) state of the system with experimental data. The considered characteristic is an analogy of entropy which has been extended to non- equilibrium states. Television observations of the auroral structure during <span class="hlt">substorm</span> activation at the Barentsburg observatory (Svalbard) have been used as a data set. Dependence of the ordering on the spatial scale has been analyzed. We found that the ordering of the aurora increases during the <span class="hlt">substorm</span> development. The same approach has been applied to data sets generated by cellular automata models. Evolution of the systems in time and dependence on external control parameters are compared and discussed. Acknowledgements. This work was supported by grant No 171076/V30 of the Norwegian Research Council and partly by the Division of Physical Sciences of Russian Academy of Science.</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_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999PhPl....6.2198D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999PhPl....6.2198D"><span><span class="hlt">Magnetospheric</span> dynamics from a low-dimensional nonlinear dynamics model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doxas, I.; Horton, W.</p> <p>1999-05-01</p> <p>A physics based model for the coupled solar WIND-<span class="hlt">Magnetosphere</span>-Ionosphere system (WINDMI) is described. The model is based on truncated descriptions of the collisionless microscopic energy transfer processes <span class="hlt">occurring</span> in the quasineutral layer, and includes a thermal flux limit neglected in the Magnetohydrodynamic (MHD) closure of the moment equations. All dynamically relevant parameters of the model can be computed analytically. The system is both Kirchhoffian and Hamiltonian, ensuring that the power input from the solar wind is divided into physically realizable energy sub-components, a property not shared by data-based filters. The model provides a consistent mathematical formalism in which different models of the solar wind driver, ionospheric dissipation, global field configuration, and <span class="hlt">substorm</span> trigger mechanism can be inserted, and the coupling between the different parts of the system investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...632362H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...632362H"><span>Response of plasmaspheric configuration to <span class="hlt">substorms</span> revealed by Chang’e 3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Han; Shen, Chao; Wang, Huaning; Zhang, Xiaoxin; Chen, Bo; Yan, Jun; Zou, Yongliao; Jorgensen, Anders M.; He, Fei; Yan, Yan; Zhu, Xiaoshuai; Huang, Ya; Xu, Ronglan</p> <p>2016-08-01</p> <p>The Moon-based Extreme Ultraviolet Camera (EUVC) of the Chang’e 3 mission provides a global and instantaneous meridian view (side view) of the Earth’s plasmasphere. The plasmasphere is one inner component of the whole <span class="hlt">magnetosphere</span>, and the configuration of the plasmasphere is sensitive to <span class="hlt">magnetospheric</span> activity (storms and <span class="hlt">substorms</span>). However, the response of the plasmaspheric configuration to <span class="hlt">substorms</span> is only partially understood, and the EUVC observations provide a good opportunity to investigate this issue. By reconstructing the global plasmaspheric configuration based on the EUVC images observed during 20–22 April 2014, we show that in the observing period, the plasmasphere had three bulges which were located at different geomagnetic longitudes. The inferred midnight transit times of the three bulges, using the rotation rate of the Earth, coincide with the expansion phase of three <span class="hlt">substorms</span>, which implies a causal relationship between the <span class="hlt">substorms</span> and the formation of the three bulges on the plasmasphere. Instead of leading to plasmaspheric erosion as geomagnetic storms do, <span class="hlt">substorms</span> initiated on the nightside of the Earth cause local inflation of the plasmasphere in the midnight region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27576944','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27576944"><span>Response of plasmaspheric configuration to <span class="hlt">substorms</span> revealed by Chang'e 3.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>He, Han; Shen, Chao; Wang, Huaning; Zhang, Xiaoxin; Chen, Bo; Yan, Jun; Zou, Yongliao; Jorgensen, Anders M; He, Fei; Yan, Yan; Zhu, Xiaoshuai; Huang, Ya; Xu, Ronglan</p> <p>2016-08-31</p> <p>The Moon-based Extreme Ultraviolet Camera (EUVC) of the Chang'e 3 mission provides a global and instantaneous meridian view (side view) of the Earth's plasmasphere. The plasmasphere is one inner component of the whole <span class="hlt">magnetosphere</span>, and the configuration of the plasmasphere is sensitive to <span class="hlt">magnetospheric</span> activity (storms and <span class="hlt">substorms</span>). However, the response of the plasmaspheric configuration to <span class="hlt">substorms</span> is only partially understood, and the EUVC observations provide a good opportunity to investigate this issue. By reconstructing the global plasmaspheric configuration based on the EUVC images observed during 20-22 April 2014, we show that in the observing period, the plasmasphere had three bulges which were located at different geomagnetic longitudes. The inferred midnight transit times of the three bulges, using the rotation rate of the Earth, coincide with the expansion phase of three <span class="hlt">substorms</span>, which implies a causal relationship between the <span class="hlt">substorms</span> and the formation of the three bulges on the plasmasphere. Instead of leading to plasmaspheric erosion as geomagnetic storms do, <span class="hlt">substorms</span> initiated on the nightside of the Earth cause local inflation of the plasmasphere in the midnight region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5006020','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5006020"><span>Response of plasmaspheric configuration to <span class="hlt">substorms</span> revealed by Chang’e 3</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>He, Han; Shen, Chao; Wang, Huaning; Zhang, Xiaoxin; Chen, Bo; Yan, Jun; Zou, Yongliao; Jorgensen, Anders M.; He, Fei; Yan, Yan; Zhu, Xiaoshuai; Huang, Ya; Xu, Ronglan</p> <p>2016-01-01</p> <p>The Moon-based Extreme Ultraviolet Camera (EUVC) of the Chang’e 3 mission provides a global and instantaneous meridian view (side view) of the Earth’s plasmasphere. The plasmasphere is one inner component of the whole <span class="hlt">magnetosphere</span>, and the configuration of the plasmasphere is sensitive to <span class="hlt">magnetospheric</span> activity (storms and <span class="hlt">substorms</span>). However, the response of the plasmaspheric configuration to <span class="hlt">substorms</span> is only partially understood, and the EUVC observations provide a good opportunity to investigate this issue. By reconstructing the global plasmaspheric configuration based on the EUVC images observed during 20–22 April 2014, we show that in the observing period, the plasmasphere had three bulges which were located at different geomagnetic longitudes. The inferred midnight transit times of the three bulges, using the rotation rate of the Earth, coincide with the expansion phase of three <span class="hlt">substorms</span>, which implies a causal relationship between the <span class="hlt">substorms</span> and the formation of the three bulges on the plasmasphere. Instead of leading to plasmaspheric erosion as geomagnetic storms do, <span class="hlt">substorms</span> initiated on the nightside of the Earth cause local inflation of the plasmasphere in the midnight region. PMID:27576944</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM41B..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM41B..07C"><span>Dependence of poleward auroral and equatorward motion on <span class="hlt">substorm</span> current wedge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, X.; McPherron, R. L.; Hsu, T. S.; Angelopoulos, V.; Pu, Z.; Yao, Z.; Zhang, H.; Connors, M. G.</p> <p>2014-12-01</p> <p>Flux pileup from fast flows and dipolarization, physical processes in the magnetotail, cause auroral evolution (brightening, poleward expansion, and equatorward motion) in the ionosphere during <span class="hlt">substorms</span>. Although such flows have been shown to produce auroral brightening, the causes of auroral poleward expansion and equatorward motion remain unclear. Two mechanisms, tailward movement of the pileup region and dipolarization of the <span class="hlt">substorm</span> current wedge (SCW), are thought to contribute to auroral poleward expansion, but no study has addressed which mechanism makes the dominant contribution. The hypothesis that auroral poleward expansion is caused by the tailward-moving pileup region is based on the assumption of a steady <span class="hlt">magnetosphere</span>. This assumption is not necessarily true during <span class="hlt">substorms</span>, however, because dipolarization of the SCW changes <span class="hlt">magnetospheric</span> configuration and thus ionospheric footprints (and mapping) of the flows. Because they lack a dynamic SCW, previous <span class="hlt">magnetospheric</span> models are statistical and static. We evaluated the dynamic effect of the SCW using a dynamic <span class="hlt">magnetospheric</span> model in which the SCW is superimposed on Tsyganenko model. The current wedge is obtained from a recently developed inversion model using only ground magnetic field data as input, and model parameters are updated every minute. Applying our dynamic <span class="hlt">magnetospheric</span> model to data from an isolated <span class="hlt">substorm</span> observed by THEMIS and GOES 10 spacecraft and ground ASIs on 13 February 2008, we found that 1) our model predicts dipolarization at GOES 10 (it can predict near-Earth magnetic variations with ground data alone); 2) there is a good temporal correlation between successive auroral brightenings and flows; 3) flow footprints from our model are collocated with auroral poleward expansion and equatorward motion. These results suggest that in this event, auroral poleward expansion and equatorward motion are mainly caused by mapping changes in the dynamic <span class="hlt">magnetosphere</span> by the SCW.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980018999','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980018999"><span>Force Balance and <span class="hlt">Substorm</span> Effects in the Magnetotail</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufmann, Richard L.; Larson, Douglas J.; Kontodinas, Ioannis D.; Ball, Bryan M.</p> <p>1997-01-01</p> <p>A model of the quiet time middle magnetotail is developed using a consistent orbit tracing technique. The momentum equation is used to calculate geocentric solar <span class="hlt">magnetospheric</span> components of the particle and electromagnetic forces throughout the current sheet. Ions generate the dominant x and z force components. Electron and ion forces almost cancel in the y direction because the two species drift earthward at comparable speeds. The force viewpoint is applied to a study of some <span class="hlt">substorm</span> processes. Generation of the rapid flows seen during <span class="hlt">substorm</span> injection and bursty bulk flow events implies substantial force imbalances. The formation of a <span class="hlt">substorm</span> diversion loop is one cause of changes in the magnetic field and therefore in the electromagnetic force. It is found that larger forces are produced when the cross-tail current is diverted to the ionosphere than would be produced if the entire tail current system simply decreased. Plasma is accelerated while the forces are unbalanced resulting in field lines within a diversion loop becoming more dipolar. Field lines become more stretched and the plasma sheet becomes thinner outside a diversion loop. Mechanisms that require thin current sheets to produce current disruption then can create additional diversion loops in the newly thinned regions. This process may be important during multiple expansion <span class="hlt">substorms</span> and in differentiating pseudoexpansions from full <span class="hlt">substorms</span>. It is found that the tail field model used here can be generated by a variety of particle distribution functions. However, for a given energy distribution the mixture of particle mirror or reflection points is constrained by the consistency requirement. The study of uniqueness also leads to the development of a technique to select guiding center electrons that will produce charge neutrality all along a flux tube containing nonguiding center ions without the imposition of a parallel electric field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6518763','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6518763"><span>Energy storage and dissipation in the magnetotail during <span class="hlt">substorms</span>. 1. Particle simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Winglee, R.M. ); Steinolfson, R.S. )</p> <p>1993-05-01</p> <p>The authors present a simulation study of the particle dynamics in the magnetotail during the development of <span class="hlt">substorms</span>. They look at how energy flows into the magnetotail under external <span class="hlt">magnetospheric</span> conditions, and study the energy storage and dissipation in the magnetic field, and the role of particle dynamics in this process. They consider two primary external influences in their model. First is the pressure exerted by the <span class="hlt">magnetospheric</span> boundary layer, on the nightside magnetopause. This pressure is expected to grow in response to solar wind penetration into the <span class="hlt">magnetosphere</span> when the interplanetary magnetic field becomes southward in the initial phases of <span class="hlt">substorm</span> growth. Second is the dawn to dusk electric field. This field is expected to grow as the current sheet thins and energy stored in the magnetic field rises. The authors argue that the simultaneous increase in both the magnetic pressure and electric field can better model magnetotail response. One sees strong earthward flows in conjunction with increased energy storage in the tail, and at <span class="hlt">substorm</span> onset one sees the ejection of plasmoids in a tailward direction with increased particle heating. The clumping of particles in the current sheet due to the opposing effects of the magnetic pressure and electric field could be responsible for <span class="hlt">substorm</span> onset, rather than instabilities such as the tearing mode.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010021220&hterms=energy+comparison&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Denergy%2Bcomparison','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010021220&hterms=energy+comparison&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Denergy%2Bcomparison"><span>Energy Characteristics of Auroral Electron Precipitation: A Comparison of <span class="hlt">Substorms</span> and Pressure Pulse Related Auroral Activity</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chua, D.; Parks, G. K.; Brittnacher, M. J.; Peria, W.; Germany, G. A.; Spann, J. F., Jr.; Carlson, C.; Rose, M. Franklin (Technical Monitor)</p> <p>2000-01-01</p> <p>The Polar Ultraviolet Imager (UVI) observes auroral responses to incident solar wind pressure pulses and interplanetary shocks such as those associated with coronal mass ejections. The arrival of a CME pressure pulse at the front of the <span class="hlt">magnetosphere</span> results in highly disturbed geomagnetic conditions and a substantial increase in both dayside and nightside auroral precipitation. Our observations show a simultaneous brightening over broad areas of the dayside and nightside aurora in response to a pressure pulse, indicating that more <span class="hlt">magnetospheric</span> regions participate as sources for auroral precipitation than during isolated <span class="hlt">substorms</span>. We estimate the average energies of incident auroral electrons using Polar UVI images and compare the precipitation energies during pressure pulse associated events to those during isolated auroral <span class="hlt">substorms</span>. Electron precipitation during <span class="hlt">substorms</span> has average energies greater than 10 keV and is structured both in local time and magnetic latitude. For auroral intensifications following the arrival of a pressure pulse or interplanetary shock, electron precipitation is less spatially structured and has greater ux of lower energy electrons (Eave _ 7 keV) than during isolated <span class="hlt">substorm</span>, onsets. The average energies of the precipitating electrons inferred from UVI are consistent with those measured in-situ by the FAST spacecraft. These observations quantify the differences between global and local auroral precipitation processes and will provide a valuable experimental check for models of sudden storm commencements and <span class="hlt">magnetospheric</span> response to perturbations in the solar wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRA..118.7714M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRA..118.7714M"><span>The detailed spatial structure of field-aligned currents comprising the <span class="hlt">substorm</span> current wedge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murphy, Kyle R.; Mann, Ian R.; Rae, I. Jonathan; Waters, Colin L.; Frey, Harald U.; Kale, Andy; Singer, Howard J.; Anderson, Brian J.; Korth, Haje</p> <p>2013-12-01</p> <p>We present a comprehensive two-dimensional view of the field-aligned currents (FACs) during the late growth and expansion phases for three isolated <span class="hlt">substorms</span> utilizing in situ observations from the Active <span class="hlt">Magnetosphere</span> and Planetary Electrodynamics Response Experiment and from ground-based magnetometer and optical instrumentation from the Canadian Array for Realtime Investigations of Magnetic Activity and Time History of Events and Macroscale Interactions during <span class="hlt">Substorms</span> ground-based arrays. We demonstrate that the structure of FACs formed during the expansion phase and associated with the <span class="hlt">substorm</span> current wedge is significantly more complex than a simple equivalent line current model comprising a downward FAC in the east and upward FAC in the west. This two-dimensional view demonstrates that azimuthal bands of upward and downward FACs with periodic structuring in latitude form across midnight and can span up to 8 h of magnetic local time. However, when averaged over latitude, the overall longitudinal structure of the net FACs resembles the simpler equivalent line current description of the <span class="hlt">substorm</span> current wedge (SCW). In addition, we demonstrate that the upward FAC elements of the structured SCW are spatially very well correlated with discrete aurora during the <span class="hlt">substorm</span> expansion phase and that discrete changes in the FAC topology are observed in the late growth phase prior to auroral <span class="hlt">substorm</span> expansion phase onset. These observations have important implications for determining how the <span class="hlt">magnetosphere</span> and ionosphere couple during the late growth phase and expansion phase, as well as providing important constraints on the <span class="hlt">magnetospheric</span> generator of the FACs comprising the SCW.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM54A..03F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM54A..03F"><span>The Extent to Which Dayside Reconnection Drives Field-Aligned Currents During <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Forsyth, C.; Shortt, M. W.; Coxon, J.; Rae, J.; Freeman, M. P.; Kalmoni, N. M. E.; Jackman, C. M.; Anderson, B. J.</p> <p>2016-12-01</p> <p>Field-aligned currents, also known as Birkeland currents, are the agents by which energy and momentum is transferred to the ionosphere from the <span class="hlt">magnetosphere</span> and solar wind. In order to understand this coupling, it is necessary to analyze the variations in these current systems with respect to the main energy sources of the solar wind and <span class="hlt">substorms</span>. In this study, we perform a superposed epoch analysis of field-aligned currents determined by the Active <span class="hlt">Magnetosphere</span> and Planetary Electrodynamics Response Experiment (AMPERE) project with respect to <span class="hlt">substorm</span> expansion phase onsets identified using the <span class="hlt">Substorm</span> Onsets and Phases from Indices of the Electrojet (SOPHIE) technique. We examine the total upward and downward currents separately in the noon, dusk, dawn and midnight sectors. Our results show that the dusk and dawn currents have up to a 66% linear correlated with the dayside reconnection rate estimated from solar wind measurements, whereas the noon and midnight currents are not. The noon currents show little or no variation throughout the <span class="hlt">substorm</span> cycle. The midnight currents follows the dusk currents up to 20 min before onset, after which the midnight current increases more rapidly and exponentially. At <span class="hlt">substorm</span> onset, the exponential growth rate increases. While the midnight field-aligned currents grow exponentially after <span class="hlt">substorm</span> onset, the auroral indices vary with a 1/6th power law. Overall, our results show that the growth and decay rates of the Region 1 and 2 current systems, which are strongest at dawn and dusk, are directly driven by the solar wind, whereas the growth and decay rates of the <span class="hlt">substorm</span> current system, which are dominant at midnight, act independently of the upstream driver.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19810059602&hterms=Chestnut&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DChestnut','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19810059602&hterms=Chestnut&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DChestnut"><span>Propagating <span class="hlt">substorm</span> injection fronts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, T. E.; Arnoldy, R. L.; Feynman, J.; Hardy, D. A.</p> <p>1981-01-01</p> <p>It is argued that a series of two-satellite observations leads to a clarification of <span class="hlt">substorm</span> plasma injection, in which boundary motion plays a major role. Emphasis is put on a type of event characterized by abrupt, dispersionless changes in electron intensity and a coincident perturbation that consists of both a field magnitude increase and a small rotation toward more dipolar orientation. Comparing plasma observations at two points, it is found that in active, preinjection conditions the two most important features of the plasma sheet are: (1) the low-energy convection boundary for near-zero energy particles, determined by the magnitude of the large-scale convection electric field; and (2) the precipitation-flow boundary layer between the hot plasma sheet and the atmospherically contaminated inner plasma sheet.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011pre7.conf....1J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011pre7.conf....1J"><span>Saturn's Radio Emissions and their Relation to <span class="hlt">Magnetospheric</span> Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jackman, C. M.</p> <p></p> <p>With the arrival of the Cassini spacecraft at Saturn in July 2004, there have been quasi-continuous observations of Saturn Kilometric Radiation (SKR) emissions. In this paper we review the response of these emissions to dynamics in Saturn's <span class="hlt">magnetosphere</span>, driven by factors internal and external to the system. We begin by reviewing solar wind data upstream of Saturn and discuss the link between solar wind compressions and dynamics in Saturn's <span class="hlt">magnetosphere</span>, evidenced by intensifications and occasional phase changes in the SKR emission. We then review the link between magnetotail reconnection and planetary radio emissions. We begin in the well-sampled magnetotail of Earth and then move to Saturn where exploration of the nightside <span class="hlt">magnetosphere</span> has revealed evidence of plasmoid-like magnetic structures and other phenomena indicative of the kronian equivalent of terrestrial <span class="hlt">substorms</span>. In general, there is a good correlation between the timing of reconnection events and enhancements in the SKR emission, coupled with extension of the emission to lower frequencies. We interpret this as growth of the radio source region to higher altitudes along the field lines, stimulated by increased precipitation of energetic electrons into the auroral zones following reconnection. We also comment on the observation that the majority of reconnection events <span class="hlt">occur</span> at SKR phases where the SKR power would be expected to be rising with time, indicating that reconnection is most likely to <span class="hlt">occur</span> at a preferred phase. We conclude with a summary of the current knowledge of the link between Saturn's <span class="hlt">magnetospheric</span> dynamics and SKR emissions, and list a number of open questions to be addressed in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007Ge%26Ae..47..193V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007Ge%26Ae..47..193V"><span>Features of the planetary distribution of auroral precipitation characteristics during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vorobjev, V. G.; Yagodkina, O. I.; Starkov, G. V.; Feldstein, Ya. I.</p> <p>2007-04-01</p> <p>A planetary pattern of <span class="hlt">substorm</span> development in auroral precipitation has been constructed on the basis of the F6 and F7 satellite observations. The behavior of the auroral injection boundaries and characteristics of precipitating electrons in various precipitation regions during all phases of a statistically mean <span class="hlt">magnetospheric</span> <span class="hlt">substorm</span> with an intensity of AL ˜ -400 nT at a maximum is considered in detail. It is shown that during a <span class="hlt">substorm</span>, the zone of structured auroral oval precipitation AOP and the diffuse auroral zone DAZ are the widest in the nighttime and daytime sectors, respectively. In the daytime sector, all precipitation regions synchronously shift equatorward not only at the origination phase but during the <span class="hlt">substorm</span> development phase. The strongest shift to low latitudes of the daytime AOP region is observed at a maximum of the development phase. As a result of this shift, the area of the polar cap increases during the phases of <span class="hlt">substorm</span> origination and development. It is shown that the average position of the precipitation boundaries and the energy fluxes of precipitating electrons at each phase are linearly related to the intensity of a magnetic disturbance. This makes it possible to develop a model of auroral precipitation development during each phase of <span class="hlt">substorms</span> of any intensity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880059315&hterms=field+magnetic+Earth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfield%2Bmagnetic%2BEarth','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880059315&hterms=field+magnetic+Earth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfield%2Bmagnetic%2BEarth"><span>Plasma and magnetic field variations in the distant magnetotail associated with near-earth <span class="hlt">substorm</span> effects</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baker, D. N.; Bame, S. J.; Mccomas, D. J.; Zwickl, R. D.; Slavin, J. A.; Smith, E. J.</p> <p>1987-01-01</p> <p>Examination of many individual event periods in the ISEE 3 deep-tail data set has suggested that <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span> produce a characteristic pattern of effects in the distant magnetotail. During the growth, or tail-energy-storage phase of <span class="hlt">substorms</span>, the magnetotail appears to grow diametrically in size, often by many earth radii. Subsequently, after the <span class="hlt">substorm</span> expansive phase onset at earth, the distant tail undergoes a sequence of plasma, field, and energetic-particle variations as large-scale plasmoids move rapidly down the tail following their disconnection from the near-earth plasma sheet. ISEE 3 data are appropriate for the study of these effects since the spacecraft remained fixed within the nominal tail location for long periods. Using newly available auroral electrojet indices (AE and AL) and Geo particle data to time <span class="hlt">substorm</span> onsets at earth, superposed epoch analyses of ISEE 3 and near-earth data prior to, and following, <span class="hlt">substorm</span> expansive phase onsets have been performed. These analyses quantify and extend substantially the understanding of the deep-tail pattern of response to global <span class="hlt">substorm</span>-induced dynamical effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..12111729H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..12111729H"><span>Contributions of <span class="hlt">substorm</span> injections to SYM-H depressions in the main phase of storms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Zhaohai; Dai, Lei; Wang, Chi; Duan, Suping; Zhang, Lingqian; Chen, Tao; Roth, I.</p> <p>2016-12-01</p> <p><span class="hlt">Substorm</span> injections bring energetic particles to the inner <span class="hlt">magnetosphere</span>. But the role of the injected population in building up the storm time ring current is not well understood. By surveying Los Alamos National Laboratory geosynchronous data during 34 storm main phases, we show evidence that at least some <span class="hlt">substorm</span> injections can contribute to <span class="hlt">substorm</span>-time scale SYM-H/Dst depressions in the main phase of storms. For event studies, we analyze two typical events in which the main-phase SYM-H index exhibited stepwise depressions that are correlated with particle flux enhancement due to injections and with AL index. A statistical study is performed based on 95 storm time injection events. The flux increases of the injected population (50-400 keV) are found proportional to the sharp SYM-H depressions during the injection interval. By identifying dispersionless and dispersive injection signals, we estimate the azimuthal extent of the <span class="hlt">substorm</span> injection. Statistical results show that the injection regions of these storm time <span class="hlt">substorms</span> are characterized with an azimuthal extent larger than 06:00 magnetic local time. These results suggest that at least some <span class="hlt">substorm</span> injections may mimic the large-scale enhanced convection and contribute to sharp decreases of Dst in the storm main phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM44A..02N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM44A..02N"><span>Coupling between pre-onset flows and <span class="hlt">substorm</span> onset waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nishimura, T.; Lyons, L. R.; Angelopoulos, V.; Donovan, E.; Mende, S. B.</p> <p>2015-12-01</p> <p>A critical, long-standing problem in <span class="hlt">substorm</span> research is identification of the sequence of events leading to <span class="hlt">substorm</span> expansion phase onset. Recent THEMIS all-sky imager (ASI) array observations have shown a repeatable pre-onset sequence, which is initiated by a poleward boundary intensification (PBI) and is followed by auroral streamers moving equatorward (earthward flow in the plasma sheet) and then by <span class="hlt">substorm</span> onset. On the other hand, <span class="hlt">substorm</span> onset is also preceded by azimuthally propagating waves, indicating a possible importance of wave instability for triggering <span class="hlt">substorm</span> onset. However, it has been difficult to identify the link between fast flows and waves. We have found an isolated <span class="hlt">substorm</span> event that was well-instrumented with the Poker Flat incoherent scatter radar (PFISR), THEMIS white-light ASI, and multi-spectral ASI, where the auroral onset <span class="hlt">occurred</span> within the PFISR and ASI fields-of-view. This <span class="hlt">substorm</span> onset was preceded by a PBI, and ionospheric flows propagated equatorward from the polar cap, crossed the PBI and reached the growth phase arc. This sequence provides evidence that flows from open magnetic field lines propagate across the open-closed boundary and reach the near-Earth plasma sheet prior to the onset. Quasi-stable oscillations in auroral luminosity and ionospheric density are found along the growth phase arc. These pre-onset auroral waves amplified abruptly at the onset time, soon after the equatorward flows reached the onset region. This sequence suggests a coupling process where pre-existing stable waves in the near-Earth plasma sheet interact with flows from further downtail and then evolve to onset instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990078594&hterms=IMF&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DIMF','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990078594&hterms=IMF&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DIMF"><span>On the Predictability of <span class="hlt">Substorms</span> Following Sharp Northward Turnings of the IMF</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blanchard, G. T.; Lyons, Larry R.; Spann, James F., Jr.; Reeves, G. D.</p> <p>1998-01-01</p> <p>It has been shown that there is an association between changes of the interplanetary magnetic field (IMF) that are expected to lead to a reduction in <span class="hlt">magnetospheric</span> convection (northward turnings, reductions) and the onset of the expansion phase of <span class="hlt">substorms</span>. This has been previously demonstrated by analyses of IMF data during time intervals associated with identified <span class="hlt">substorm</span> onsets. Here we examine whether observations of northward turnings of the IMF can be used to predict the occurrence of <span class="hlt">substorms</span>. We first identified sharp northward turnings that follow an interval of steady, southward IMF using measurements from the Wind spacecraft during the first 180 days of 1997. We also required that the northward turning be observed by either IMP-8 or GEOTAIL, in addition to Wind, and that one of the observing satellites be sufficiently close to the Earth-Sun line, or that the two observing satellites be sufficiently separated, that we are reasonably certain that the northward turning affected the <span class="hlt">magnetosphere</span>. We also used the dual observations to estimate the arrival of the northward turning at the Earth. Using these criteria, we predicted 17 <span class="hlt">substorms</span>. We then searched for the following signatures of <span class="hlt">substorm</span> onset around the time of the predicted onset: auroral brightening followed by auroral bulge expansion observed by Polar UVI, geosynchronous particle injection, geosynchronous magnetic field dipolarization, and an appropriate magnetic disturbance at the surface of the Earth. Of the 17 predictions of <span class="hlt">substorms</span>, 10 were successful in that a <span class="hlt">substorm</span> onset was observed within 12 min of the predicted onset, 1 is indeterminate due to a lack of data at the Earth, 1 had unusual activity that we have not been able to identify, and 5 were unsuccessful. The failure of these last 5 predictions is explicable. Two of the northward turnings that failed to produce <span class="hlt">substorms</span> were preceded by the lowest average of the set. The remaining 3 were the only cases in which the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JGR...10410235P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JGR...10410235P"><span>Ballooning instability in the presence of a plasma flow: A synthesis of tail reconnection and current disruption models for the initiation of <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pu, Z. Y.; Kang, K. B.; Korth, A.; Fu, S. Y.; Zong, Q. G.; Chen, Z. X.; Hong, M. H.; Liu, Z. X.; Mouikis, C. G.; Friedel, R. W. H.; Pulkkinen, T.</p> <p>1999-05-01</p> <p>The drift ballooning mode (DBM) instability near the inner edge of the plasma sheet (IEPS) is studied further by including a nonstationary earthward flow and flow shear in the analysis. Both equatorial and off-equatorial regions are considered. It is found that the presence of a decelerated earthward flow destabilizes both the M- and M+ branches of the DBM in a large portion of the current sheet near the IEPS and substantially increases the growth rate of the instability. The flow shear in the premidnight sector causes the conventional ballooning mode to weakly subside, while it slightly enhances the growth rate for the Alfvénic ballooning mode. The combination of the earthward flow and flow shear makes both the Alfvénic ballooning mode and conventional ballooning mode grow much faster than they would without the flow, giving rise to coupled Alfvénic slow magnetosonic waves, field-aligned currents, and the formation of a current wedge. A synthesis of tail reconnection and cross-tail current disruption scenarios is proposed for the <span class="hlt">substorm</span> global initiation process: When the fast flow produced by magnetic reconnection in the midtail abruptly decelerates at the IEPS, it compresses the plasma populations earthward of the front, transports momentum to them, and pushes them farther earthward. This creates the configuration instability in a large portion of the inner tail magnetic field lines on both the tailward side and earthward side of the braking point. As soon as the ionospheric conductance increases over a threshold level, the auroral electrojet is greatly intensified, which leads to the formation of the <span class="hlt">substorm</span> current wedge and dipolarization of the magnetic field. This <span class="hlt">substorm</span> paradigm combines the near-Earth neutral line and near-Earth current disruption scenarios for the initiation of <span class="hlt">substorms</span> and may also synthesize dynamical processes in the <span class="hlt">magnetosphere</span>-ionosphere coupling and field line resonance during the <span class="hlt">substorm</span> onset. We intend to use this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSA31C..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSA31C..07K"><span>Equatorial counterelectrojets during geomagnetic storms and their possible dynamos in the <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kikuchi, T.; Hashimoto, K. K.; Ebihara, Y.; Tsuji, Y.; Veenadhari, B.; Nishimura, T.; Tanaka, T.; Fujita, S.; Nagatsuma, T.</p> <p>2012-12-01</p> <p>During the <span class="hlt">substorm</span> growth phase and storm main phase, the high pressure plasma accumulated in the cusp and mantle regions activates a dynamo for the dawn-to-dusk convection electric field and the Region-1 field-aligned currents (R1 FACs) [Tanaka, 1995]. The electric field and FACs are conveyed by the shear Alfven waves to the polar ionosphere and the electric field extends promptly to low latitude through the Earth-ionosphere waveguide [Kikuchi and Araki, 1979]. The electric field drives the DP2 currents at mid latitudes [Wilson et al., 2001; Tsuji et al., 2012] and intensifies the equatorial electrojet (EEJ) [Kikuchi et al., 1996, 2008]. The convection electric field extends to the inner <span class="hlt">magnetosphere</span> promptly [Nishimura et al., 2009] and energizes the plasma in the partial ring current region with the help of the gradient and curvature drift [Ebihara and Ejiri, 2000], which in turn works as a dynamo for the dusk-to-dawn electric field and the R2 FACs. The dusk-to-dawn electric field causes the counterelectrojet (CEJ) at the equator when the IMF turns northward [Rastogi, 1975]. The CEJ often appears during <span class="hlt">substorms</span> [Kobea et al., 2000; Kikuchi et al., 2000]. Both the R1 and R2 FACs are intensified by the <span class="hlt">substorm</span> expansion, with the R2 FACs strong enough to cause the CEJ [Hashimoto et al., 2011]. The CEJ often <span class="hlt">occurs</span> during the recovery phase of geomagnetic storms [Kikuchi et al., 2008; Tsuji et al., 2012], while the CEJ also appears during the storm main phase under the relatively stable southward IMF [Fejer et al., 2007; Veenadhari et al., 2010]. In this paper, we analyzed several storm events to identify the dynamo for the stormtime CEJ. The disturbance dynamo is a commonly accepted dynamo for the long lasting stormtime CEJ [Blanc and Richmond, 1980; Fejer and Scherliess 1997]. However, the observed rapid and periodic development of the CEJ should be attributed to the R2 FACs generated in the inner <span class="hlt">magnetosphere</span>. Based on the magnetometer and radar</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMSM43A1720Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMSM43A1720Z"><span>A Unified Scenario of Near-Earth <span class="hlt">Substorm</span> Onset: Analysis of THEMIS Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, P.; Raeder, J.; Bhattacharjee, A.; Germaschewski, K.; Hegna, C.</p> <p>2008-12-01</p> <p>We propose an alternative scenario for the <span class="hlt">substorm</span> onset process, based on ideal ballooning stability analysis of the near-Earth plasma sheet during recent THEMIS <span class="hlt">substorm</span> events. In this scenario, the ballooning instability is initiated by the magnetic reconnection in the near-Earth plasma sheet, which in turn directly contributes to the trigger of a full onset. Using the solar wind data from WIND satellite observation for the <span class="hlt">substorm</span> event as an input at dayside, we reconstructed a sequence of global <span class="hlt">magnetospheric</span> configurations around the <span class="hlt">substorm</span> onset by means of OpenGGCM simulation. These simulations have reproduced most of the salient features, including the onset timing, observed in the THEMIS <span class="hlt">substorm</span> events [Raeder et al, 2008]. The ballooning instability criterion and growth rate are evaluated for the near-Earth plasma sheet region where the configuration satisfies a quasi-static equilibrium condition. Our analysis of the evolution of the near-Earth magnetotail region during the <span class="hlt">substorm</span> events reveals a correlation between the breaching of the ballooning stability condition and the <span class="hlt">substorm</span> onset in both temporal and spatial domains. The analysis suggests that the Earthward bulk plasma flow induced by the reconnection event in the near- Earth plasma sheet, leads to the pressure build-up and creates a favorable condition for the initiation of the ballooning instability in that same region. This new alternative scenario further elaborates earlier conjectures on the roles of reconnection and ballooning instability [Bhattacharjee et al, 1998], and has the potential to integrate both the near-Earth neutral-line model [McPherron et al, 1973] and the near-Earth current-sheet- disruption model [Lui et al, 1988] into a unified model of the near-Earth <span class="hlt">substorm</span> onset. Research supported by U.S. NSF Grant No. ATM-0542954.</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_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013Ge%26Ae..53..613K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013Ge%26Ae..53..613K"><span>Isolated nighttime <span class="hlt">substorms</span> and morning geomagnetic Pc5 pulsations from ground-based and satellite (THEMIS) observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kauristie, K.; Uspensky, M. V.; Kleimenova, N. G.; Kozyreva, O. V.; Dubyagin, S. V.; Vlasov, A. A.</p> <p>2013-09-01</p> <p>The analysis results of a complex of phenomena that were developing in the evening and morning <span class="hlt">magnetospheric</span> and ionospheric sectors during two events (January 18 and February 19, 2008) are presented. The analysis is based on the observation data in the magnetotail from the THEMIS satellites and ground-based observations in the morning (MIRACLE network) and nighttime (THEMIS ground-based network) sectors. The events with moderate <span class="hlt">substorms</span> in the nighttime sector were preceded by strong geomagnetic Pc5 pulsations in the morning sector, the regime of which changed during the development of auroral disturbances. The <span class="hlt">substorms</span> were accompanied by dipolizations in the magnetotail at distances of ~10 Re and unexpected jump-like fluxes of ˜200-keV electrons. The fluxes appeared within several minutes after a breakup at three central THEMIS satellites simultaneously spaced up to 1.7 Re. According with the ASC data at the NAL observatory (3 frames/min) and with the THEMIS network of ASC data, onset of auroral activations in the night and morning sectors <span class="hlt">occurred</span> simultaneously. Probable reasons for the sudden suppression or intensification of Pc5 pulsations are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1914406T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1914406T"><span>Alfvénic solar wind powers <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanskanen, Eija; Hynönen, Reko; Mursula, Kalevi</p> <p>2017-04-01</p> <p>Alfvenic solar wind fluctuations (ALFs) are known to modulate geomagnetic activity. We have examined high-latitude geomagnetic activity over the solar cycle 23 and found out that increase of solar wind Alfvenicity enhance both auroral <span class="hlt">substorm</span> intensity and <span class="hlt">substorm</span> frequency. Alfvénic solar wind fluctuations are found throughout the solar cycle, but they are fastest, most frequent and geo-effective in the declining phase of the cycle, when the number of high-speed streams at the Earth's vicinity increases rapidly. We find a rapid transition from the predominance of slow (< 400 km/s) ALFs in 2002 to fast (> 600 km/s) ALFs in 2003, in coincidence with the rapid increase of <span class="hlt">substorm</span> activity from late 2002 to early 2003. The Alfvénicity of solar wind increased by 40% from 2002 to 2003. After the transition the fast ALFs <span class="hlt">occur</span> twice per solar rotation while in previous year only four fast ALF intervals were detected. Increase of solar wind Alfvénicity by 40% from 2002 to 2003, and transition from slow to fast Alfvén fluctuations coincide with the increase of auroral <span class="hlt">substorm</span> intensity by 28% and <span class="hlt">substorm</span> frequency by 43%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840014973','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840014973"><span>Energetics of the <span class="hlt">magnetosphere</span>, revised</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stern, D. P.</p> <p>1984-01-01</p> <p>The approximate magnitudes of power inputs and energies associated with the Earth's <span class="hlt">magnetosphere</span> were derived. The nearest 40 R sub E of the plasma sheet current receive some 3.10 to the 11th power watt, and much of this goes to the Birkeland currents, which require 1-3 10 to the 11th power watt. Of that energy, about 30% appears as the energy of auroral particles and most of the rest as ionosphere joule heating. The ring current contains about 10 to the 15th power joule at quiet times, several times as much during magnetic storms, and the magnetic energy stored in the tail lobes is comparable. <span class="hlt">Substorm</span> energy releases may range at 1.5 to 30 10 to the 11th power watt. Compared to these, the local energy release rate by magnetic merging in the <span class="hlt">magnetosphere</span> is small. Merging is essential for the existence of open field lines, which make such inputs possible. Merging also seems to be implicated in <span class="hlt">substorms</span>: most of the released energy only becomes evident far from the merging region, though some particles may gain appreciable energy in that region itself, if the plasma sheet is squeezed out completely and the high latitude lobes interact directly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950011849&hterms=election&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Delection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950011849&hterms=election&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Delection"><span>Energy dissipation in <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weiss, Loretta A.; Reiff, P. H.; Moses, J. J.; Heelis, R. A.; Moore, B. D.</p> <p>1992-01-01</p> <p>The energy dissipated by <span class="hlt">substorms</span> manifested in several ways is discussed: the Joule dissipation in the ionosphere; the energization of the ring current by the injection of plasma sheet particles; auroral election and ion acceleration; plasmoid ejection; and plasma sheet ion heating during the recovery phase. For each of these energy dissipation mechanisms, a 'rule of thumb' formula is given, and a typical dissipation rate and total energy expenditure is estimated. The total energy dissipated as Joule heat (approximately) 2 x 10(exp 15) is found about twice the ring current injection term, and may be even larger if small scale effects are included. The energy expended in auroral electron precipitation, on the other hand, is smaller than the Joule heating by a factor of five. The energy expended in refilling and heating the plasma sheets is estimated to be approximately 5 x 10(exp 14)J, while the energy lost due to plasmoid ejection is between (approximately) (10 exp 13)(exp 14)J.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950011849&hterms=Loretta&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DLoretta','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950011849&hterms=Loretta&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DLoretta"><span>Energy dissipation in <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weiss, Loretta A.; Reiff, P. H.; Moses, J. J.; Heelis, R. A.; Moore, B. D.</p> <p>1992-01-01</p> <p>The energy dissipated by <span class="hlt">substorms</span> manifested in several ways is discussed: the Joule dissipation in the ionosphere; the energization of the ring current by the injection of plasma sheet particles; auroral election and ion acceleration; plasmoid ejection; and plasma sheet ion heating during the recovery phase. For each of these energy dissipation mechanisms, a 'rule of thumb' formula is given, and a typical dissipation rate and total energy expenditure is estimated. The total energy dissipated as Joule heat (approximately) 2 x 10(exp 15) is found about twice the ring current injection term, and may be even larger if small scale effects are included. The energy expended in auroral electron precipitation, on the other hand, is smaller than the Joule heating by a factor of five. The energy expended in refilling and heating the plasma sheets is estimated to be approximately 5 x 10(exp 14)J, while the energy lost due to plasmoid ejection is between (approximately) (10 exp 13)(exp 14)J.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.6237K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.6237K"><span>The Bursts Series of Long-period Irregular Ipcl-type Geomagnetic Pulsations As A Element of <span class="hlt">Substorm</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kurazhkovskaya, N. A.; Klain, B. I.</p> <p></p> <p>The investigation of simultaneous observations of bursts series of pulsations ipcl in a frequency band 2.1-5.5 mHz during moderate geomagnetic activity (Kp ~ 2-3), ob- served in the dayside polar cusp and of long-period irregular pulsations apparent in a nightside of an auroral oval was carried out. For the analysis the records of a magnetic field in observatories Mirny (invariant geomagnetic latitude -76,93; longitude 122,92) and Yellownife (invariant geomagnetic latitude 69,94; longitude 294,38), located ap- proximately on one meridian noon - midnight, were used. It was revealed, that regime burst of pulsations ipcl is observed on a <span class="hlt">substorm</span> phase recovery. The beginning of bursts series of pulsations ipcl on the dayside of a <span class="hlt">magnetosphere</span> corresponds to the moment of a final stage of <span class="hlt">substorm</span> expansion phase in night sector. Besides regime burst ipcl begins in 60 minutes after change of a direction vertical component IMF with southward on northward. In dominant number of cases the excitation beginning of bursts series of pulsations ipcl lags from a oscillation beginning of pulsations of a type Pi3, accompanying development <span class="hlt">substorms</span>, on 40-60 of minutes. Thus, the anal- ysed bursts series of pulsations ipcl are an essential element of <span class="hlt">substorm</span>. The delay of bursts series ipcl in relation to time of pulsations Pi3-type occurrence and <span class="hlt">substorm</span> expansion phase can be explained within the framework of <span class="hlt">magnetospheric</span> <span class="hlt">substorm</span> model, in which the current across a tail is made through plasma mantle of a magneto- sphere, which field lines are project in dayside polar cusp and entry layes. The release of energy in a tail of <span class="hlt">magnetosphere</span> in a <span class="hlt">substorm</span> phase recovery subsequently leads to intensification of long-period perturbations in dayside polar cusp.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740012862','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740012862"><span>Electric and magnetic field observations during a <span class="hlt">substorm</span> of 24 February 1970</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gurnett, D. A.; Akasofu, S. I.</p> <p>1974-01-01</p> <p>A series of electric field measurements is reported which was obtained from the Injun 5 satellite along with a simultaneous magnetic disturbance observed in the interplanetary medium and on the ground during a magnetic <span class="hlt">substorm</span>. The <span class="hlt">substorm</span> analyzed took place on February 24, 1970. Prior to the onset of the <span class="hlt">substorm</span> a greatly enhanced anti-sunward plasma flow was observed over the polar cap. The enhanced plasma flow <span class="hlt">occurred</span> about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the <span class="hlt">substorm</span> were essentially unchanged indicating that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the <span class="hlt">substorm</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM23A4172S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM23A4172S"><span>A Double-Disruption <span class="hlt">Substorm</span> Model - The Growth Phase</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sofko, G. J.; McWilliams, K. A.; Hussey, G. C.</p> <p>2014-12-01</p> <p>When the IMF turns from Bz- to Bz+, dayside merging forms open lobe field lines at low latitudes. These lobe lines are populated with shocked solar wind and dayside <span class="hlt">magnetospheric</span> plasma from the reconnection inflow. As those lobe flux tubes pass tailward over the polar caps, they are also populated with outflow from the north and south polar cap ionospheres. As the lobe lines move tailward, they acquire a convex curvature that blocks the westward-flowing cross-tail current (XTJ). This constitutes the first stage of XTJ disruption, and it begins less than 10 min after the frontside merging.The disrupted XTJ closes dawn-to-dusk in the transition plasmasheet (TPS), where it produces a downward FAC to the ionosphere. This causes the proton arc, which is seen for the period from about 10 - 80 min after frontside merging begins at time t=0. The lobe lines eventually reconnect well downtail at about t=30 minutes. The middle section that closes the lobe lines has concave curvature and is called the Neutral Sheet (NSh). The resulting stretched field lines thus have a central NSh which separates the two convex-curvature regions to the north and south, regions which are called the Disruption Zones (DZs); the overall combination of the NDZ, NSh and SDZ is called the Stretched Plasmasheet (SPS). As the SPS continues to grow and the stretched lines are pulled earthward to relieve the magnetic tension, the filling of the NSh <span class="hlt">occurs</span> both from the DTNL with the higher energy <span class="hlt">magnetospheric</span> particle population on the lobe lines, but eventually also at about 25 earth radii when the polar cap ionospheric outflow (PCO) component finally reaches the NSh. A NSh FAC system forms, from which electrons flow down to the auroral ionosphere to create the pre-onset arc, starting at about t=65 min. At the same time, the Lyons-Speiser mechanism is initiated in the inner NSh, causing the PCO ions to become trapped and accelerated in the inner NSh region. Eventually, when the SPS grows earthward</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.4834C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.4834C"><span><span class="hlt">Substorm</span> onset: A switch on the sequence of transport from decreasing entropy to increasing entropy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, C. X.</p> <p>2016-05-01</p> <p>In this study, we propose a scenario about the trigger for <span class="hlt">substorm</span> onset. In a stable <span class="hlt">magnetosphere</span>, entropy is an increasing function tailward. However, in the growth phase of a <span class="hlt">substorm</span>, a later born bubble has lower entropy than earlier born bubbles. When a bubble arrives at its final destination in the near-Earth region, it will spread azimuthally because of its relatively uniform entropy. The magnetic flux tubes of a dying bubble, which cause the most equatorward aurora thin arc, would block the later coming bubble tailward of them, forming an unstable domain. Therefore, an interchange instability develops, which leads to the collapse of the unstable domain, followed by the collapse of the stretched plasma sheet. We regard the <span class="hlt">substorm</span> onset as a switch on the sequence of transport, i.e., from a decreasing entropy process to an increasing entropy process. We calculated the most unstable growth rates and the wavelengths of instability, and both are in agreement with observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Ge%26Ae..57..251B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Ge%26Ae..57..251B"><span>Effect of solar dynamics parameters on the formation of <span class="hlt">substorm</span> activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barkhatov, N. A.; Vorob'ev, V. G.; Revunov, S. E.; Yagodkina, O. I.</p> <p>2017-05-01</p> <p>An algorithm for retrieving the AL index dynamics from the parameters of solar-wind plasma and the interplanetary magnetic field (IMF) has been developed. Along with other geoeffective parameters of the solar wind, an integral parameter in the form of the cumulative sum Σ[N* V 2] is used to determine the process of <span class="hlt">substorm</span> formation. The algorithm is incorporated into a framework developed to retrieve the AL index of an Elman-type artificial neural network (ANN) containing an additional layer of neurons that provides an "internal memory" of the prehistory of the dynamical process to be retrieved. The ANN is trained on data of 70 eight-hour-long time intervals, including the periods of isolated <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>. The efficiency of this approach is demonstrated by numerical neural-network experiments on retrieving the dynamics of the AL index from the of solar wind and IMF parameters during <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711024O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711024O"><span>Bursty reconnection modulating the <span class="hlt">substorm</span> current wedge, a <span class="hlt">substorm</span> case study re-analysed by ECLAT tools.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Opgenoorth, Hermann; Palin, Laurianne; Ågren, Karin; Zivkovic, Tatjana; Facsko, Gabor; Sergeev, Victor; Kubyshkina, Marina; Nikolaev, Alexander; Milan, Steve; Imber, Suzanne; Kauristie, Kirsti; Palmroth, Minna; van de Kamp, Max; Nakamura, Rumi; Boakes, Peter</p> <p>2015-04-01</p> <p>Multi-instrumental data mining and interpretation can be tedious and complicated. In this context, the ECLAT (European Cluster Assimilation Technology) project was created to « provide a novel and unique data base and tools for space scientists, by providing an upgrade of the European Space Agency's Cluster Active Archive (CAA). » How can this new tool help the space plasma physics community? Here we demonstrate the power of coordinated global and meso-scale ground-based data to put satellite data into the proper context. We re-analyse a well-isolated <span class="hlt">substorm</span> with a strong growth phase, which starts right overhead the Scandinavian network of instruments on 8 September 2002. This event was previously studied in detail by Sergeev et al (2005), based on a THEMIS-like configuration near-midnight using a unique radial constellation of LANL (~6.6Re), Geotail and Polar (~9Re), and Cluster (~16Re). In this new study we add detailed IMAGE spacecraft and ground-based network data. <span class="hlt">Magnetospheric</span> models are specially adapted using solar wind conditions and in-situ observations. Simulation results are compared to the in-situ observations and discussed. We show how - both before and after <span class="hlt">substorm</span> onset - bursty reconnection in the tail modulates the localised field aligned current flow associated with the <span class="hlt">substorm</span> current wedge.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT........60P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT........60P"><span>Charged Particle Energization and Transport in the Magnetotail during <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pan, Qingjiang</p> <p></p> <p>This dissertation addresses the problem of energization of particles (both electrons and ions) to tens and hundreds of keV and the associated transport process in the magnetotail during <span class="hlt">substorms</span>. Particles energized in the magnetotail are further accelerated to even higher energies (hundreds of keV to MeV) in the radiation belts, causing space weather hazards to human activities in space and on ground. We develop an analytical model to quantitatively estimate flux changes caused by betatron and Fermi acceleration when particles are transported along narrow high-speed flow channels from the magnetotail to the inner <span class="hlt">magnetosphere</span>. The model shows that energetic particle flux can be significantly enhanced by a modest compression of the magnetic field and/or shrinking of the distance between the magnetic mirror points. We use coordinated spacecraft measurements, global magnetohydrodynamic (MHD) simulations driven by measured upstream solar wind conditions, and large-scale kinetic (LSK) simulations to quantify electron local acceleration in the near-Earth reconnection region and nonlocal acceleration during plasma earthward transport. Compared to the analytical model, application of the LSK simulations is much less restrictive because trajectories of millions of test particles are calculated in the realistically determined global MHD fields and the results are statistical. The simulation results validated by the observations show that electrons following a power law distribution at high energies are generated earthward of the reconnection site, and that the majority of the energetic electrons observed in the inner <span class="hlt">magnetosphere</span> are caused by adiabatic acceleration in association with magnetic dipolarizations and fast flows during earthward transport. We extend the global MHD+LSK simulations to examine ion energization and compare it with electron energization. The simulations demonstrate that ions in the magnetotail are first nonadiabatically accelerated in the weak</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.8773Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.8773Z"><span>Bursty bulk flows at different <span class="hlt">magnetospheric</span> activity levels: Dependence on IMF conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, L. Q.; Baumjohann, W.; Wang, C.; Dai, L.; Tang, B. B.</p> <p>2016-09-01</p> <p>Based on concurrent observations of the ACE and Geotail satellites from 1998 to 2005, we statistically analyzed and compared the earthward bursty bulk flows (BBFs) with local positive Bz under different interplanetary magnetic field (IMF) conditions. Four different <span class="hlt">magnetospheric</span> activity levels (MALs), including quiet times and <span class="hlt">substorm</span> growth/expansion/recovery phases, are considered. The properties of the BBFs, including their ion temperature (T), Vx component, x component of the energy flux density (Qx), and the solar wind dawn-dusk electric field Ey (observed at 1 AU), are analyzed. Main observations include the following: (1) BBF tends to have less penetration distance for northward IMF (NW-IMF) than for southward IMF (SW-IMF). Inward of 15 RE the BBFs for SW-IMF are dominant. Few BBFs for NW-IMF <span class="hlt">occur</span> within 15 RE. (2) The occurrence probabilities of the BBFs at each MAL depend highly on the orientations of the IMF. During quiet times, the BBFs for NW-IMF are dominant. Reversely, during the growth and expansion phases of a <span class="hlt">substorm</span>, the BBFs for SW-IMF are dominant. (3) The strengths of the BBF have significant evolution with <span class="hlt">substorm</span> development. For SW-IMF condition, the strengths of the BBFs are the lowest for quiet times. The strength of the BBFs tends to increase during the growth phase and reaches to the strongest value during the expansion phase, then, decays during the recovery phase. For NW-IMF condition, the strengths of the BBFs evolve with the <span class="hlt">substorm</span> development in a similar way as for SW-IMF condition. (4) For SW-IMF, the solar wind Ey evolves with the <span class="hlt">substorm</span> development in a similar way to the strength of the BBFs. However, no clear evolution is found for NW-IMF. (5) The strengths of the BBF Qx and solar wind Ey are closely related. Both tend to be stronger for growth phase than for quite time, reach the strongest for expansion phase, then decay for recovery phase. It appears that to trigger a <span class="hlt">substorm</span>, the strength of the BBFs should</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EP%26S...69..129N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EP%26S...69..129N"><span>Near-Earth plasma sheet boundary dynamics during <span class="hlt">substorm</span> dipolarization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakamura, Rumi; Nagai, Tsugunobu; Birn, Joachim; Sergeev, Victor A.; Le Contel, Olivier; Varsani, Ali; Baumjohann, Wolfgang; Nakamura, Takuma; Apatenkov, Sergey; Artemyev, Anton; Ergun, Robert E.; Fuselier, Stephen A.; Gershman, Daniel J.; Giles, Barbara J.; Khotyaintsev, Yuri V.; Lindqvist, Per-Arne; Magnes, Werner; Mauk, Barry; Russell, Christopher T.; Singer, Howard J.; Stawarz, Julia; Strangeway, Robert J.; Anderson, Brian; Bromund, Ken R.; Fischer, David; Kepko, Laurence; Le, Guan; Plaschke, Ferdinand; Slavin, James A.; Cohen, Ian; Jaynes, Allison; Turner, Drew L.</p> <p>2017-09-01</p> <p>We report on the large-scale evolution of dipolarization in the near-Earth plasma sheet during an intense (AL -1000 nT) <span class="hlt">substorm</span> on August 10, 2016, when multiple spacecraft at radial distances between 4 and 15 R E were present in the night-side <span class="hlt">magnetosphere</span>. This global dipolarization consisted of multiple short-timescale (a couple of minutes) B z disturbances detected by spacecraft distributed over 9 MLT, consistent with the large-scale <span class="hlt">substorm</span> current wedge observed by ground-based magnetometers. The four spacecraft of the <span class="hlt">Magnetospheric</span> Multiscale were located in the southern hemisphere plasma sheet and observed fast flow disturbances associated with this dipolarization. The high-time-resolution measurements from MMS enable us to detect the rapid motion of the field structures and flow disturbances separately. A distinct pattern of the flow and field disturbance near the plasma boundaries was found. We suggest that a vortex motion created around the localized flows resulted in another field-aligned current system at the off-equatorial side of the BBF-associated R1/R2 systems, as was predicted by the MHD simulation of a localized reconnection jet. The observations by GOES and Geotail, which were located in the opposite hemisphere and local time, support this view. We demonstrate that the processes of both Earthward flow braking and of accumulated magnetic flux evolving tailward also control the dynamics in the boundary region of the near-Earth plasma sheet.[Figure not available: see fulltext.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840003016','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840003016"><span>Saturn's outer <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schardt, A. W.; Behannon, K. W.; Carbary, J. F.; Eviatar, A.; Lepping, R. P.; Siscoe, G. L.</p> <p>1983-01-01</p> <p>Similarities between the Saturnian and terrestrial outer <span class="hlt">magnetosphere</span> are examined. Saturn, like Earth, has a fully developed magnetic tail, 80 to 100 RS in diameter. One major difference between the two outer <span class="hlt">magnetospheres</span> is the hydrogen and nitrogen torus produced by Titan. This plasma is, in general, convected in the corotation direction at nearly the rigid corotation speed. Energies of <span class="hlt">magnetospheric</span> particles extend to above 500 keV. In contrast, interplanetary protons and ions above 2 MeV have free access to the outer <span class="hlt">magnetosphere</span> to distances well below the Stormer cutoff. This access presumably <span class="hlt">occurs</span> through the magnetotail. In addition to the H+, H2+, and H3+ ions primarily of local origin, energetic He, C, N, and O ions are found with solar composition. Their flux can be substantially enhanced over that of interplanetary ions at energies of 0.2 to 0.4 MeV/nuc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020080669','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020080669"><span>Modeling <span class="hlt">Magnetospheric</span> Sources</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Walker, Raymond J.; Ashour-Abdalla, Maha; Ogino, Tatsuki; Peroomian, Vahe; Richard, Robert L.</p> <p>2001-01-01</p> <p>We have used global magnetohydrodynamic, simulations of the interaction between the solar wind and <span class="hlt">magnetosphere</span> together with single particle trajectory calculations to investigate the sources of plasma entering the <span class="hlt">magnetosphere</span>. In all of our calculations solar wind plasma primarily enters the <span class="hlt">magnetosphere</span> when the field line on which it is convecting reconnects. When the interplanetary magnetic field has a northward component the reconnection is in the polar cusp region. In the simulations plasma in the low latitude boundary layer (LLBL) can be on either open or closed field lines. Open field lines <span class="hlt">occur</span> when the high latitude reconnection <span class="hlt">occurs</span> in only one cusp. In the MHD calculations the ionosphere does not contribute significantly to the LLBL for northward IMF. The particle trajectory calculations show that ions preferentially enter in the cusp region where they can be accelerated by non-adiabatic motion across the high latitude electric field. For southward IMF in the MHD simulations the plasma in the middle and inner <span class="hlt">magnetosphere</span> comes from the inner (ionospheric) boundary of the simulation. Solar wind plasma on open field lines is confined to high latitudes and exits the tailward boundary of the simulation without reaching the plasma sheet. The LLBL is populated by both ionospheric and solar wind plasma. When the particle trajectories are included solar wind ions can enter the middle <span class="hlt">magnetosphere</span>. We have used both the MHD simulations and the particle calculations to estimate source rates for the <span class="hlt">magnetosphere</span> which are consistent with those inferred from observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM31F..01M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM31F..01M"><span>The Four-Part Field-Aligned Current System in the Ionosphere at <span class="hlt">Substorm</span> Onset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McWilliams, K. A.; Sofko, G. J.; Bristow, W. A.; Hussey, G. C.</p> <p>2015-12-01</p> <p>Whereas the plasma circulation in the ionosphere is driven by convective drift which is the same for ions and electrons, the <span class="hlt">magnetospheric</span> plasma circulation includes curvature and gradient drifts, which are charge-dependent. There is even a region of the Neutral Sheet in which the ions, but not the electrons, are "unmagnetized" and where charge separation can <span class="hlt">occur</span> even for convective drift, which the electrons execute but the ions do not. Due to the charge separations in the <span class="hlt">magnetosphere</span>, field-aligned currents are generated. The FACs and the associated electric fields play an important role in producing the convection pattern in the ionosphere. Here we argue that there are two pairs of FACs near <span class="hlt">substorm</span> onset. One pair involves the auroral zone portion of the convection. There, a downward D FAC <span class="hlt">occurs</span> in the poleward part of the auroral zone and an upward U FAC <span class="hlt">occurs</span> in the equatorward part. We show that the D-U auroral FAC pair results from the odd situation in the INSh, where the electrons can convect earthward while the unmagnetized ions do not and so remain further tailward of the electrons. The equatorward edge of the auroral zone is marked by a convection reversal, because the auroral zone flows have an eastward velocity component, whereas subauroral flows have a westward component. At the convection reversal, the flow is strictly southward and the electric field strictly westward. The subauroral zone maps out to the outer radiation belt, where the high-energy electrons precipitate tailward of the energetic electron trapping boundary,and high-energy ions precipitate tailward of the energetic ion trapping boundary, the latter being earthward of the former. As a result, another FAC pair forms on field lines in the ORB/subauroral regions. The U FAC of the latter region is adjacent but earthward of the U FAC of the auroral zone pair. The D-U auroral zone pair is poleward of the U-D subauroral (Radiation Belt) pair. Finally, we note that the electric field</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM52A..04L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM52A..04L"><span>Form the end of <span class="hlt">substorm</span> growth phase till the first 1-2 minutes of onset: Evidence of a transitional stage in optical auroral and in-situ observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, J.; Zhu, P.; Donovan, E.; Saito, M.</p> <p>2016-12-01</p> <p>A classical scenario of auroral <span class="hlt">substorm</span> usaully involves a quiescent preexisting arc during the growth phase and a significant brightening and poleward expansion of auroras characteristic of the <span class="hlt">substorm</span> expansion phase. However, optical auroral observations repeatedly reveal that there is often a 1-2 minute transitional stage between the quiescent growth-phase arc and the significant auroral expansion. Such a transitional stage is characterized by a gradual intensification and in many cases the emergence of azimuthally-spaced structures, aka the "auroral beads", along the preexisting arc. The auroral beads usually feature well-defined e-growth rate in optical intensity. Despite the beading and moderate intensification the arc shape is essentially maintained for the first minute of onset, until it is deformed by a violent poleward expansion of <span class="hlt">substorm</span> auroras which marks the full expansion phase of the <span class="hlt">substorm</span>. In this study, we investigate a number of onset auroral beading events with conjugate observations from THEMIS probes, with focus on potential <span class="hlt">magnetospheric</span> signatures of the transitional stage in in-situ data. These signatures typically consist of magnetic field/pressure perturbations that gradually grow in magnitude but are nevertheless limited as compared to those in the subsequent large-scale dipolarization/current disruption. The wave period of the perturbation is found to roughly conform to w kyvy , in which w is the frequency of perturbation, ky is the azimuthal wavenumber inferred from the separation of auroral beads, and vy is the azimuthal flow velocity. The perturbations detected on azimuthally separated probes are different in phase. Those potential clues of the transitional stage in in-situ observations <span class="hlt">occur</span> concurrently with or slightly precede the initial auroral brightening and beading seen in optical data. We find evidence of such a transitional stage in <span class="hlt">substorm</span> onset events with and without preceding fast earthward flows. The above</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/960799','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/960799"><span>Observational evidence for an inside-out <span class="hlt">substorm</span> onset scenario</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Henderson, Michael G</p> <p>2008-01-01</p> <p>We present observations which provide strong support for a <span class="hlt">substorm</span> onset scenario in which a localized inner <span class="hlt">magnetospheric</span> instability developed first and was later followed by the development of a Near Earth Neutral Line (NENL) farther down-tail. Specifically, we find that the onset began as a localized brightening of an intensified growth phase arc which developed as a periodic series of arc-aligned (i.e. azimuthally arrayed) bright spots. As the disturbance grew, it evolved into vortical structures that propagated poleward and eventually morphed into an east-west aligned arc system at the poleward edge of the auroral <span class="hlt">substorm</span> bulge. The auroral intensification shows an exponential growth with an estimated e-folding time of around 188 seconds (linear growth rate, {gamma} of 5.33 x 10{sup -3} s{sup -1}). During the initial breakup, no obvious distortions of auroral forms to the north were observed. However, during the expansion phase, intensifications of the poleward boundary of the expanding bulge were observed together with the equatorward ejection of auroral streamers into the bulge. A strong particle injection was observed at geosynchronous orbit, but was delayed by several minutes relative to onsel. Ground magnetometer data also shows a two phase development of mid-latitude positive H-bays, with a quasi-linear increase in H between the onset and the injection. We conclude that this event provides strong evidence in favor of the so-called 'inside-out' <span class="hlt">substorm</span> onset scenario in which the near Earth region activates first followed at a later time by the formation of a near-to-mid tail <span class="hlt">substorm</span> X-line. The ballooning instability is discussed as a likely mechanism for the initial onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001sps..proc..108G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001sps..proc..108G"><span>Understanding magnetic storms and <span class="hlt">substorms</span> through data closure with global MHD simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goodrich, C. C.; Lyon, J. G.; Wiltberger, M. J.; Fedder, J. A.; Slinker, S. P.</p> <p></p> <p>Magnetic storms and <span class="hlt">substorms</span> are the most dynamic expressions of the coupling of the solar wind flow into the geospace environment. Since first defined by their ionospheric signatures observed from the ground, their study has been dominated by the immense increase in observations available from the expansion in sophistication and coverage of ground based and satellite sensors. These observations have increased our understanding greatly regarding the conditions, characteristics and signatures of storms and <span class="hlt">substorms</span> in both the ionosphere and <span class="hlt">magnetosphere</span>. However, it has proven easier to compile increasingly detailed pictures for both storms and <span class="hlt">substorms</span> to constrain and validate models than to develop a fundamental understanding of their dynamics from the observations. Despite the expansion of observations, the immense and highly coupled solar wind <span class="hlt">magnetosphere</span> ionosphere system remains quite sparsely sampled, and will remain so in the foreseeable future. More recently numerical simulation models have developed to the point that global modeling of full geospace system is practical. Global MHD codes, using upstream solar wind observations, can easily model <span class="hlt">substorm</span> events lasting several hours or storms lasting several days. While the MHD codes can reproduce the global current systems and plasma and magnetic field structure, they can only approximately model the inner <span class="hlt">magnetosphere</span> and important boundary layers including the bow shock, magnetopause, and magnetotail current sheet. Kinetic codes Vlasov, particle in cell (PIC), or hybrid could in principle accurately model these structures. However, it remains impractical to perform a kinetic simulation on the global scale of geospace with realistic plasma and field parameters. Despite their limitations, global MHD codes are currently the only practical tool for modeling the global geospace system. These limitations of the observations and codes suggest the best strategy now for studying storms and <span class="hlt">substorm</span> is</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_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......583M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......583M"><span>A statistical study of plasmawaves and energetic particles in the outer <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Min, Kyungguk</p> <p></p> <p> method is not only fast enough for near real-time calculation of L*, enabling spacecraft tracking in this coordinates, but scalable to a large number of L * values that are often required for inter-comparison between simulation results and observations. (2) The relationship between the electron injection and the chorus waves was studied from the simultaneous observations of a <span class="hlt">substorm</span> event on 23March 2007 made in space and on ground. Timing analysis and a test particle simulation indicated that the electrons injected during the <span class="hlt">substorm</span> could form a pitch-angle distribution suitable for the whistler-mode instability when they arrive near the dawn-side magnetopause. (3) The EMIC waves are found to <span class="hlt">occur</span> ubiquitously throughout the outer <span class="hlt">magnetosphere</span> and their properties distribute asymmetrically in local time. The asymmetry in the wave properties seems to be correlated with the electron density distribution and ion temperature anisotropy, as supported by a linear EMIC instability model. (4) The size of coherent activity of the EMIC waves was estimated using the multi-spacecraft observations made by the THEMIS spacecraft and cross correlation analysis. It is found that the characteristic dimension in the direction transverse to the local magnetic field is 2--3 times the local EMIC wavelength. (5) The global distribution of the equatorial mass density was derived from the toroidal mode standing Alfven waves in an unprecedented spatial scale. The equatorial mass density is distributed asymmetrically with a bulge at the dusk sector and the magnitude falls logarithmically with increasing radial distance. It is confirmed that the variation in the derived mass density is only weakly related to the geomagnetic activity, but has strong correlation with the solar activity. The major contribution of this dissertation is the extension of the scope of previous understanding of various plasma wave properties and energetic particle dynamics in the inner <span class="hlt">magnetosphere</span> to outer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMSM54B..02Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMSM54B..02Z"><span>Identification of <span class="hlt">substorm</span> onset location and pre-onset sequence using Reimei, THEMIS GBO, PFISR and Geotail (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zou, S.; Moldwin, M.; Nishimura, Y.; Lyons, L. R.; Hirahara, M.; Sakanoi, T.; Asamura, K.; Nicolls, M. J.; Miyashita, Y.; Mende, S. B.; Heinselman, C. J.</p> <p>2010-12-01</p> <p>One of the most important questions puzzling the <span class="hlt">substorm</span> community is the location of the breakup arc relative to general auroral morphology, ionospheric convection, and particle precipitation, which are ionospheric signatures of dynamic processes in the <span class="hlt">magnetosphere</span>. We present a state-of-the-art ground and space-based imaging study of a <span class="hlt">substorm</span> that <span class="hlt">occurred</span> on 12 October 2007. The auroral breakup was observed simultaneously by the Reimei satellite, THEMIS all-sky imager and PFISR radar. The magnetic field footprint of the Geotail spacecraft was also near the ionospheric location of the <span class="hlt">substorm</span> onset. We report unique spaceborne high-spatial and temporal resolution images of a portion of a breakup arc and of a wave-like auroral enhancement captured by cameras onboard Reimei. This <span class="hlt">substorm</span> was isolated and <span class="hlt">occurred</span> in a thin, only ~1.5° wide, auroral oval. Observations from PFISR and Geotail suggest a sudden plasma sheet thinning initiated ~10 min prior to the onset. Wave-like auroral enhancements were observed twice along the most equatorward preexisting auroral arc about 3 min and 1 min before the auroral expansion. This most equatorward wavy arc did not initiate the auroral spatial expansion, but remained almost stable until being engulfed after onset by auroral equatorward expansion from slightly higher latitudes. The wave-like auroral enhancement was associated with three fine inverted-V structures and fully embedded within energetic ion precipitation and westward flows. Following this enhancement, an arc formed at higher latitude just adjacent to the PSBL, and was likely a poleward boundary intensification (PBI). This arc then extended southwestward and initiated the spatial expansion. The breakup arc, i.e., the arc initiated the spatial expansion, was located poleward of and separated from the wave-like auroral enhancement. Assuming longitudinal homogeneity of proton precipitation over one degree in geographic longitude, this breakup arc was located</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122..349K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122..349K"><span>Particle energization by a <span class="hlt">substorm</span> dipolarization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kabin, K.; Kalugin, G.; Donovan, E.; Spanswick, E.</p> <p>2017-01-01</p> <p>Magnetotail dipolarizations, often associated with <span class="hlt">substorms</span>, produce significant energetic particle enhancements in the nighttime <span class="hlt">magnetosphere</span>. In this paper, we apply our recently developed magnetotail dipolarization model to the problem of energizing electrons and ions. Our model is two-dimensional in the meridional plane and is characterized by the ability to precisely control the location of the transition from the dipole-like to tail-like magnetic fields. Both magnetic and electric fields are calculated, self-consistently, as the transition zone retreats farther into the tail and the area around the Earth occupied by dipole-like lines increases in size. These fields are used to calculate the motion of electrons and ions and changes in their energies. We consider the energizing effects of the fields restricted to ±15° and ±30° sectors around the midnight meridian, as well the axisymmetric case. Energies of some electrons increase by a factor of 25, which is more than enough to produce observable ionospheric signatures. Electrons are treated using the Guiding Center approximation, while protons and heavier particles generally require description based on the Lorentz equations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120..253C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120..253C"><span>Magnetic mapping effects of <span class="hlt">substorm</span> currents leading to auroral poleward expansion and equatorward retreat</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, Xiangning; McPherron, Robert L.; Hsu, Tung-Shin; Angelopoulos, Vassilis; Pu, Zuyin; Yao, Zhonghua; Zhang, Hui; Connors, Martin</p> <p>2015-01-01</p> <p>fast flows, magnetic field dipolarization, and its relaxation are linked to auroral brightening, poleward expansion, and equatorward motion during <span class="hlt">substorm</span> onset, expansion, and recovery, respectively. While auroral brightening is often attributed to the field-aligned currents produced by flow vorticity and pressure redistribution, the physical causes of auroral poleward expansion and equatorward retreat are not fully understood. Simplistically, such latitudinal changes can be directly associated to the tailward motion of the flux pileup region and the earthward flux transport toward the dayside that depletes the near-Earth plasma sheet. However, because the equatorial magnetic field profile and the <span class="hlt">magnetospheric</span> field-aligned current system change significantly, mapping is severely distorted. To investigate this distortion, we superimpose a <span class="hlt">substorm</span> current wedge model (dynamically driven by ground-based observations) on the global Tsyganenko model T96 during an isolated <span class="hlt">substorm</span> on 13 February 2008, observed by the Time History of Events and Macroscale Interactions during <span class="hlt">Substorms</span> and GOES 10 spacecraft and by ground all-sky imagers. We validate our model by showing that the timing and ionospheric projection of the flux pileup region and flow bursts observed at the spacecraft match auroral activations. We then use the improved mapping enabled by the model to demonstrate that in this event, auroral poleward expansion and equatorward retreat are mainly caused by <span class="hlt">substorm</span>-current-wedge-induced mapping changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.1973D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.1973D"><span>Modeling of <span class="hlt">substorm</span> development with a kinematic effect by the global MHD simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>den, Mitsue; Fujita, Shigeru; Tanaka, Takashi; Horiuchi, Ritoku</p> <p></p> <p>Magnetic reconnection is considered to play an important role in space phenomena such as <span class="hlt">substorm</span> in the Earth's <span class="hlt">magnetosphere</span>. Recently, Tanaka and Fujita reproduced <span class="hlt">substorm</span> evoution process by numerical simulation with the global MHD code. In the MHD framework, the dissipation model is used for modeling of the kinetic effects. They found that the normalized reconnection viscosity, one of the dessipation model employed there, gave a large effect for the <span class="hlt">substorm</span> development though that viscosity was assumed to be a constant parameter. It is well known that magnetric reconnection is controlled by microscopic kinetic mechanism. Horiuchi et al. investigated the roles of microscopic plasma instabilities on the violation of the frozen-in condition by examining the force balance equation based on explicit electromagnetic particle simulation for an ion-scale current sheet, and concluded that the growth of drift kink instability can create anomalous resistivity leading to the excitation of collisionless reconnection. They estimated the effective resistivity based on the particle simulation data. In this paper, we perform <span class="hlt">substorm</span> simulation by using the global MHD code with this anomalous resistivity obtained in their microscopic approach istead of the emprical resistivity model, and investigate the relationship between the <span class="hlt">substorm</span> development and the anomalous resistivity model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950045388&hterms=education+coexistence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Deducation%2Bcoexistence','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950045388&hterms=education+coexistence&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Deducation%2Bcoexistence"><span>Ground-based studies of ionospheric convection associated with <span class="hlt">substorm</span> expansion</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kamide, Y.; Richmond, A. D.; Emery, B. A.; Hutchins, C. F.; Ahn, B.-H.; De La Beaujardiere, O.; Foster, J. C.; Heelis, R. A.; Kroehl, H. W.; Rich, F. J.</p> <p>1994-01-01</p> <p>The instantaneous patterns of electric fields and currents in the high-latitude ionosphere are deduced by combining satellite and radar measurements of the ionospheric drift velocity, along with ground-based magnetometer observations for October 25, 1981. The period under study was characterized by a relatively stable southward interplanetary magnetic field (IMF), so that the obtained electric field patterns do reflect, in general, the state of sustained and enhanced plasma convection in the <span class="hlt">magnetosphere</span>. During one of the satellite passes, however, an intense westward electrojet caused by a <span class="hlt">substorm</span> intruded into the satellite (DE2) and radar (Chatanika, Alaska) field of view in the premidnight sector, providing a unique opportunity to differentiate the enhanced convection and <span class="hlt">substorm</span> expansion fields. The distributions of the calculated electric potential for the expansion and maximum phases of the <span class="hlt">substorm</span> show the first clear evidence of the coexistence of two physically different systems in the global convection pattern. The changes in the convection pattern during the <span class="hlt">substorm</span> indicate that the large-scale potential distributions are indeed of general two-cell patterns representing the southward IMF status, but the night-morning cell has two positive peaks, one in the midnight sector and the other in the late morning hours, corresponding to the <span class="hlt">substorm</span> expansion and the convection enhancement, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870048934&hterms=ISEE-3&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DISEE-3','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870048934&hterms=ISEE-3&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DISEE-3"><span>Simultaneous observations of the near-earth and distant geomagnetic tail during a <span class="hlt">substorm</span> by ISEE-1, ISEE-3 and geostationary spacecraft</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Richardson, I. G.; Scholer, M.; Tsurutani, B. T.; Daly, P. W.; Baker, D. N.</p> <p>1987-01-01</p> <p>The structure of the geomagnetic tail during a <span class="hlt">substorm</span> is investigated by combining plasma, magnetic field, and energetic particle data from the ISEE-3 spacecraft in the deep tail with similar near-earth observations from ISEE-1 and geostationary spacecraft. The observations can be interpreted in terms of the neutral-line model of <span class="hlt">substorms</span> and indicate the formation of a closed-loop field region (plasmoid) following <span class="hlt">substorm</span> onset, which is ejected down the tail. The plasmoid is observed to have a double-loop field strucure. This may be the result of a second <span class="hlt">substorm</span> onset <span class="hlt">occurring</span> about 25 min after the first, producing a further near-earth neutral line and closed field loop. During the <span class="hlt">substorm</span> recovery phase, the <span class="hlt">substorm</span> neutral line moves tailward to beyond 130 earth radii from earth by some 3 h after <span class="hlt">substorm</span> onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1910355N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1910355N"><span>Parameters of 1-4 mHz (Pc5/Pi3) ULF pulsations during the intervals preceding non-triggered <span class="hlt">substorms</span> at high geomagnetic latitudes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nosikova, Nataliya; Yagova, Nadezda; Baddeley, Lisa; Kozyreva, Olga; Lorentzen, Dag; Pilipenko, Vyacheslav</p> <p>2017-04-01</p> <p>One of the important questions for understanding <span class="hlt">substorm</span> generation is the possible existence of specific pre-<span class="hlt">substorm</span> variations of plasma, particles and electromagnetic field parameters. In this case analyzing of isolated non-triggered <span class="hlt">substorms</span> (i.e. <span class="hlt">substorms</span> that <span class="hlt">occur</span> under quiet geomagnetic conditions without any visible triggers in IMF or SW) gives benefits for investigation of processes of <span class="hlt">substorm</span> preparation. It was shown in previous studies that during a few hours preceding a non-triggered isolated <span class="hlt">substorm</span>, coherent geomagnetic and aurroral luminosity pulsations are observed. Moreover, PSD, amplitudes of geomagnetic fluctuations in Pc5/Pi3 (1-4 mHz) frequency range and some spectral parameters differ from those registered on days without <span class="hlt">substorms</span>. In present work this sort of pulsations has been studied in details. Features of longitudinal and latitudinal profiles are presented. Possible correlation with ULF disturbances in IMF and SW as well as in the magnetotail/magnetosheath are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.2796H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.2796H"><span>Flow bursts, breakup arc, and <span class="hlt">substorm</span> current wedge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haerendel, Gerhard</p> <p>2015-04-01</p> <p>Energy liberated by the reconnection process in the near-Earth tail is transported via flow bursts toward the dipolar <span class="hlt">magnetosphere</span> during <span class="hlt">substorms</span>. The breakup arc is a manifestation of the arrival of the bursts under flow braking and energy deposition. Its structure and behavior is analyzed on the basis of five striking spatial, temporal, and energetic properties, qualitatively and in part also quantitatively. A key element is the formation of stop layers. They are thin layers, of the width of an ion gyro radius, in which the magnetic field makes a transition from tail to near-dipolar <span class="hlt">magnetosphere</span> configurations and in which the kinetic energy of fast flows is converted into electromagnetic energy of kinetic Alfvén waves. The flows arise from the relaxation of the strong magnetic shear stresses in the leading part of the flow bursts. The bright narrow arcs of less than 10 km width inside the broad poleward expanding breakup arc, Alfvénic in nature and visually characterized by erratic short-lived rays, are seen as traces of the stop layers. The gaps between two narrow and highly structured arcs are filled with more diffuse emissions. They are attributed to the relaxation of the less strained magnetic field of the flow bursts. Eastward flows along the arcs are linked to the shrinking gaps between two successive arcs and the entry of auroral streamers into the dipolar <span class="hlt">magnetosphere</span> in the midnight sector. Flow braking in the stop layers forms multiple pairs of narrow balanced currents and cannot be behind the formation of the <span class="hlt">substorm</span> current wedge. Instead, its origin is attributed to the force exerted by the dipolarized magnetic field of the flow bursts on the high-beta plasma, after the high magnetic shears have relaxed and the fast flows and stop layer process have subsided, in other words, to the "dying flow bursts."</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850041177&hterms=1055&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2526%25231055','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850041177&hterms=1055&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3D%2526%25231055"><span>Solar wind control of <span class="hlt">magnetospheric</span> pressure (CDAW 6)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fairfield, D. H.</p> <p>1985-01-01</p> <p>The CDAW 6 data base is used to compare solar wind and <span class="hlt">magnetospheric</span> pressures. The flaring angle of the tail magnetopause is determined by assuming that the component of solar wind pressure normal to the tail boundary is equal to the total pressure within the tail. Results indicate an increase in the tail flaring angle from 18 deg to 32 deg prior to the 1055 <span class="hlt">substorm</span> onset and a decrease to 25 deg after the onset. This behavior supports the concept of tail energy storage before the <span class="hlt">substorm</span> and subsequent release after the onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850041177&hterms=1055&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231055','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850041177&hterms=1055&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231055"><span>Solar wind control of <span class="hlt">magnetospheric</span> pressure (CDAW 6)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fairfield, D. H.</p> <p>1985-01-01</p> <p>The CDAW 6 data base is used to compare solar wind and <span class="hlt">magnetospheric</span> pressures. The flaring angle of the tail magnetopause is determined by assuming that the component of solar wind pressure normal to the tail boundary is equal to the total pressure within the tail. Results indicate an increase in the tail flaring angle from 18 deg to 32 deg prior to the 1055 <span class="hlt">substorm</span> onset and a decrease to 25 deg after the onset. This behavior supports the concept of tail energy storage before the <span class="hlt">substorm</span> and subsequent release after the onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980038194','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980038194"><span>Studies of Westward Electrojets and Field-Aligned Currents in the Magnetotail During <span class="hlt">Substorms</span>: Implications for Magnetic Field Models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Spence, Harlan E.</p> <p>1996-01-01</p> <p> discrete features in the context of the global picture. We reported on our initial study at national and international meetings and published the results of our predictions of the low-altitude signatures of the plasma sheet. In addition, the PI was invited to contribute a publication to the so-called 'Great Debate in Space Physics' series that is a feature of EOS. The topic was on the nature of <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>. Specific questions of the when and where a <span class="hlt">substorm</span> <span class="hlt">occurs</span> and the connection between the auroral and <span class="hlt">magnetospheric</span> components were discussed in that paper. This paper therefore was derived exclusively from the research supported by this grant. Attachment: Empirical modeling of the quite time nightside <span class="hlt">magnetosphere</span>.' 'CRRES observations of particle flux dropout event.' The what, where, when, and why of <span class="hlt">magnetospheric</span> <span class="hlt">substorm</span> triggers'. and 'Low altitude signature of the plasma sheet: model prediction of local time dependence'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRA..117.3225M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRA..117.3225M"><span>Two Wide-Angle Imaging Neutral-Atom Spectrometers and Interstellar Boundary Explorer energetic neutral atom imaging of the 5 April 2010 <span class="hlt">substorm</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McComas, D. J.; Buzulukova, N.; Connors, M. G.; Dayeh, M. A.; Goldstein, J.; Funsten, H. O.; Fuselier, S.; Schwadron, N. A.; Valek, P.</p> <p>2012-03-01</p> <p>This study is the first to combine energetic neutral atom (ENA) observations from Two Wide-Angle Imaging Neutral-Atom Spectrometers (TWINS) and Interstellar Boundary Explorer (IBEX). Here we examine the arrival of an interplanetary shock and the subsequent geomagnetically effective <span class="hlt">substorm</span> on 5 April 2010, which was associated with the Galaxy 15 communications satellite anomaly. IBEX shows sharply enhanced ENA emissions immediately upon compression of the dayside <span class="hlt">magnetosphere</span> at 08:26:17+/-9 s UT. The compression drove a markedly different spectral shape for the dayside emissions, with a strong enhancement at energies >1 keV, which persisted for hours after the shock arrival, consistent with the higher solar wind speed, density, and dynamic pressure (˜10 nPa) after the shock. TWINS ENA observations indicate a slower response of the ring current and precipitation of ring current ions as low-altitude emissions ˜15 min later, with the >50 keV ion precipitation leading the <10 keV precipitation by ˜20 min. These observations suggest internal <span class="hlt">magnetospheric</span> processes are <span class="hlt">occurring</span> after compression of the <span class="hlt">magnetosphere</span> and before the ring current ions end up in the loss cone and precipitate into the ionosphere. We also compare MHD simulation results with both the TWINS and IBEX ENA observations; while the overall fluxes and distributions of emissions were generally similar, there were significant quantitative differences. Such differences emphasize the complexity of the <span class="hlt">magnetospheric</span> system and importance of the global perspective for macroscopic <span class="hlt">magnetospheric</span> studies. Finally, Appendix A documents important details of the TWINS data processing, including improved binning procedures, smoothing of images to a given level of statistical accuracy, and differential background subtraction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950029532&hterms=energy+participation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Denergy%2Bparticipation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950029532&hterms=energy+participation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Denergy%2Bparticipation"><span>Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Daglis, Loannis A.; Livi, Stefano; Sarris, Emmanuel T.; Wilken, Berend</p> <p>1994-01-01</p> <p>Comprehensive energy density studies provide an important measure of the participation of various sources in energization processes and have been relatively rare in the literature. We present a statistical study of the energy density of the near-Earth magnetotail major ions (H(+), O(+), He(++), He(+)) during <span class="hlt">substorm</span> expansion phase and discuss its implications for the solar wind/<span class="hlt">magnetosphere</span>/ionosphere coupling. Our aim is to examine the relation between auroral activity and the particle energization during <span class="hlt">substorms</span> through the correlation between the AE indices and the energy density of the major <span class="hlt">magnetospheric</span> ions. The data we used here were collected by the charge-energy-mass (CHEM) spectrometer on board the Active <span class="hlt">Magnetospheric</span> Particle Trace Explorer (AMPTE)/Charge Composition Explorer (CCE) satellite in the near-equatorial nightside <span class="hlt">magnetosphere</span>, at geocentric distances approximately 7 to 9 R(sub E). CHEM provided the opportunity to conduct the first statistical study of energy density in the near-Earth magnetotail with multispecies particle data extending into the higher energy range (greater than or equal to 20 keV/E). the use of 1-min AE indices in this study should be emphasized, as the use (in previous statistical studies) of the (3-hour) Kp index or of long-time averages of AE indices essentially smoothed out all the information on <span class="hlt">substorms</span>. Most distinct feature of our study is the excellent correlation of O(+) energy density with the AE index, in contrast with the remarkably poor He(++) energy density - AE index correlation. Furthermore, we examined the relation of the ion energy density to the electrojet activity during <span class="hlt">substorm</span> growth phase. The O(+) energy density is strongly correlated with the pre-onset AU index, that is the eastward electrojet intensity, which represents the growth phase current system. Our investigation shows that the near-Earth magnetotail is increasingly fed with energetic ionospheric ions during periods of enhanced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950029532&hterms=earth+hour&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dearth%2Bhour','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950029532&hterms=earth+hour&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dearth%2Bhour"><span>Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Daglis, Loannis A.; Livi, Stefano; Sarris, Emmanuel T.; Wilken, Berend</p> <p>1994-01-01</p> <p>Comprehensive energy density studies provide an important measure of the participation of various sources in energization processes and have been relatively rare in the literature. We present a statistical study of the energy density of the near-Earth magnetotail major ions (H(+), O(+), He(++), He(+)) during <span class="hlt">substorm</span> expansion phase and discuss its implications for the solar wind/<span class="hlt">magnetosphere</span>/ionosphere coupling. Our aim is to examine the relation between auroral activity and the particle energization during <span class="hlt">substorms</span> through the correlation between the AE indices and the energy density of the major <span class="hlt">magnetospheric</span> ions. The data we used here were collected by the charge-energy-mass (CHEM) spectrometer on board the Active <span class="hlt">Magnetospheric</span> Particle Trace Explorer (AMPTE)/Charge Composition Explorer (CCE) satellite in the near-equatorial nightside <span class="hlt">magnetosphere</span>, at geocentric distances approximately 7 to 9 R(sub E). CHEM provided the opportunity to conduct the first statistical study of energy density in the near-Earth magnetotail with multispecies particle data extending into the higher energy range (greater than or equal to 20 keV/E). the use of 1-min AE indices in this study should be emphasized, as the use (in previous statistical studies) of the (3-hour) Kp index or of long-time averages of AE indices essentially smoothed out all the information on <span class="hlt">substorms</span>. Most distinct feature of our study is the excellent correlation of O(+) energy density with the AE index, in contrast with the remarkably poor He(++) energy density - AE index correlation. Furthermore, we examined the relation of the ion energy density to the electrojet activity during <span class="hlt">substorm</span> growth phase. The O(+) energy density is strongly correlated with the pre-onset AU index, that is the eastward electrojet intensity, which represents the growth phase current system. Our investigation shows that the near-Earth magnetotail is increasingly fed with energetic ionospheric ions during periods of enhanced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JASTP.119..129D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JASTP.119..129D"><span>Eastward electrojet enhancements during <span class="hlt">substorm</span> activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Onofrio, M.; Partamies, N.; Tanskanen, E.</p> <p>2014-11-01</p> <p>In this study, we use a semi-automatic routine to identify negative and positive bays in the IMAGE magnetometer data during seven months in 2003. The IMAGE stations have been divided into three latitude regions to monitor the time evolution and temporal relationship between the regions during <span class="hlt">substorms</span>. In particular, we focus on the events where both positive and negative ground magnetic deflections are observed in different latitude regions. We found 101 events in total. We examine separately a subset of 32 events, for which the local electrojet index values are larger than the global ones, suggesting that the strongest activity at that time takes place within or very close to the local time sector of IMAGE. We systematically analyze the temporal difference and the intensity of the positive and negative bays. Our results show that the magnitude of the positive bay is on average about half of that of the negative bay. Two thirds of the positive bays within the IMAGE network peak earlier than the negative bays. Because the positive and negative bays <span class="hlt">occur</span> meridionally very close together, we suggest that the enhancements of the westward current at the poleward part of the auroral oval and the eastward current within the return flow are very tightly coupled through field-aligned currents and closing horizontal currents. The <span class="hlt">substorm</span> current system appears as a superposition on the large-scale current pattern in the vicinity of the evening sector shear flow region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990109130&hterms=Auroras&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAuroras','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990109130&hterms=Auroras&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAuroras"><span>GEOTAIL and POLAR Observations of Auroral Kilometric Radiation and Terrestrial Low Frequency Bursts and their Relationship to Energetic Particles, Auroras, and Other <span class="hlt">Substorm</span> Phenomena</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, R . R.; Gurnett, D. A.; Frank, L. A.; Thomsen, Michelle F.; Parks, G. K.; Brittnacher, M. J.; Spann, James F., Jr.; Imhoff, W. L.; Mobilia, J. H.</p> <p>1999-01-01</p> <p>Terrestrial low frequency (LF) bursts are plasma wave phenomena that appear to be a part of the low frequency end of the auroral kilometric radiation (AKR) spectrum and are observed during strong <span class="hlt">substorms</span>, GEOTAIL and POLAR plasma wave observations from within the <span class="hlt">magnetosphere</span> show that the AKR increases in intensity and its lower frequency limits decrease when LF bursts are observed. The first is expected as it is shows <span class="hlt">substorm</span> onset and the latter indicates that the AKR source region is expanding to higher altitudes. Images from the POLAR VIS Earth Camera operating in the far-UV range and the POLAR UVI experiment usually feature an auroral brightening and an expansion of the aurora to higher latitudes at the time of the LF bursts. Enhanced fluxes of X-rays from precipitating electrons have also been observed by POLAR PIXIE. High resolution ground Abstract: magnetometer data from the CANOPUS and IMAGE networks show that the LF bursts <span class="hlt">occur</span> when the expansive phase onset signatures are most intense. The ground magnetometer data and the CANOPUS meridian scanning photometer data sometimes show that during the LF burst events the expansive phase onset starts at unusually low latitudes and moves poleward. Large injections of energetic protons and electrons have also been detected by the GOES and LANL geosynchronous satellites during LF burst events. While most of the auroral brightenings and energetic particle injections associated with the LF bursts <span class="hlt">occur</span> near local midnight, several have been observed as early as mid-afternoon. From these various measurements, we are achieving a better understanding of the plasma and particle motions during <span class="hlt">substorms</span> that are associated with the generation and propagation of terrestrial LF bursts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E1264I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E1264I"><span>Ground and satellite observations of the low-latitude onsets of auroral <span class="hlt">substorm</span> during a major magnetic storm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ievenko, Igor; Parnikov, Stanislav; Alexeyev, Valeriy</p> <p></p> <p>It is known that the first onset of auroral <span class="hlt">substorm</span> expansion is connected with the brightness increase and breakup of the most equatorial arc. The subsequent <span class="hlt">substorm</span> activizations can be observed in the intensification of auroral arcs at higher latitudes. As a result a formation of auroral bulge and poleward shift of a westward electrojet maximum takes place. The development of auroral bulge maps the precipitation dynamics of energetic particles during <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>. In this work the research results of auroral <span class="hlt">substorm</span> during the major magnetic storm on March 20, 2001 (Dst =-150 nT) are submitted. The aurorae were registered at the Yakutsk meridian (130ºE; 200ºE, geom.) by the meridian-scanning and zenith photometers in the 630, 557.7 [OI], 427.8 (N2+) and 486.1 nm (H beta) emissions. Before the <span class="hlt">substorm</span> onset the equatorial arc is observed at low geomagnetic latitudes of 55-57ºN (the dipole L=3.0-3.3). The zenith photometer registers an intense H beta emission in the arc (~400 R). The fast increase of the 427.8, 557.7 nm emission intensity during two equatorial arc breakups is accompanied by the decrease of H beta intensity by a factor of ~5. The aurora dynamics is compared with the measurements of precipitating flux of electrons and protons aboard DMSP F15 satellite, <span class="hlt">substorm</span> injections at a geosynchronous orbit, variations in the solar wind and IMF and also images of the auroral oval from the IMAGE satellite. The ground and satellite observations are considered from a position of change of the magnetic field configuration during the low-latitude <span class="hlt">substorm</span>. We assume that the sharp drop of H beta emission intensity (precipitating protons flux) during the breakups of equatorial arc may testify to a connection of its location with a proton isotropic boundary in the inner <span class="hlt">magnetosphere</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JSWSC...6A..37E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JSWSC...6A..37E"><span>Effects of <span class="hlt">substorm</span> electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edvardsen, Inge; Johnsen, Magnar G.; Løvhaug, Unni P.</p> <p>2016-10-01</p> <p>The geomagnetic field often experiences large fluctuations, especially at high latitudes in the auroral zones. We have found, using simulations, that there are significant differences in the <span class="hlt">substorm</span> signature, in certain coordinate systems, as a function of longitude. This is confirmed by the analysis of real, measured data from comparable locations. Large geomagnetic fluctuations pose challenges for companies involved in resource exploitation since the Earth's magnetic field is used as the reference when navigating drilling equipment. It is widely known that geomagnetic activity increases with increasing latitude and that the largest fluctuations are caused by <span class="hlt">substorms</span>. In the auroral zones, <span class="hlt">substorms</span> are common phenomena, <span class="hlt">occurring</span> almost every night. In principle, the magnitude of geomagnetic disturbances from two identical <span class="hlt">substorms</span> along concurrent geomagnetic latitudes around the globe, at different local times, will be the same. However, the signature of a <span class="hlt">substorm</span> will change as a function of geomagnetic longitude due to varying declination, dipole declination, and horizontal magnetic field along constant geomagnetic latitudes. To investigate and quantify this, we applied a simple <span class="hlt">substorm</span> current wedge model in combination with a dipole representation of the Earth's magnetic field to simulate magnetic <span class="hlt">substorms</span> of different morphologies and local times. The results of these simulations were compared to statistical data from observatories and are discussed in the context of resource exploitation in the Arctic. We also attempt to determine and quantify areas in the auroral zone where there is a potential for increased space weather challenges compared to other areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17..848K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17..848K"><span>Jumps of the solar wind direction and the <span class="hlt">substorm</span> probability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kubyshkina, Daria; Kubyshkina, Marina; Semenov, Vladimir</p> <p>2015-04-01</p> <p><span class="hlt">Magnetospheric</span> <span class="hlt">substorm</span> commonly supposed to consist of two stages, loading and unloading. During the first stage the magnetic energy is stored in the magnetotail, which leads to increasing of the magnetic field intensity in the lobes and electric currents in the plasma sheet. The next uloading stage usually related to the reconnection process, which releases accumulated magnetic energy and produces the bursty bulk flows (BBFs) in the magnetotail. Such a scheme has been confirmed from both experimental and theoretical points of view. The weakest point of this scheme is the physical conditions which are necessary for the onset of the reconnection, but although the huge number of investigations was made to this end. Among them <span class="hlt">substorm</span> triggers such as pressure pulses, turning of the interplanetary magnetic field (IMF) to the north direction and so on. We would like to emphasize the role of the bent current sheets first proposed by Kivelson and Hughes in 1990. The idea is that in the asymmetric configurations gradients and current density growth, so these conditions are supposed to be favorable for the reconnection. Then the minimal stress of the system can lead to the <span class="hlt">substorm</span> onset. In the presented study we have analyzed the possibility of the current sheet asymmetry to be the trigger in theory and in observations (by statistical analysis of <span class="hlt">substorm</span> occurrences). The bent of the current sheet can be produced by different sources. The most evident of them are the dipole tilt angle variations and the changes of the solar wind direction. The first source, tilt variations, are slow, so in the current study we at first analyzed the fast changes of the solar wind. The experimental analysis includes the investigation of the number of the events against dipole tilt angle and the solar wind direction, which both produce the distortion and inclination of the dipole current sheet. Theoretical investigation of this issue is based on the analysis of the quasi</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_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><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> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM44A..01O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM44A..01O"><span>Current sheet thinning, reconnection onset, and auroral morphology during geomagnetic <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Otto, A.; Hsieh, M. S.</p> <p>2015-12-01</p> <p>Geomagnetic <span class="hlt">substorms</span> represent a fundamental energy release mechanism for the terrestrial <span class="hlt">magnetosphere</span>. Specifically, the evolution of thin currents sheets during the <span class="hlt">substorm</span> growth phase plays a key role for <span class="hlt">substorms</span> because such current sheets present a much lower threshold for the onset of tearing modes and magnetic reconnection than the usually thick magnetotail current sheet. Here we examine and compare two basic processes for current sheet thinning in the Earth's magnetotail: Current sheet thinning (1) through closed magnetic flux depletion (MFD) in the near Earth magnetotail caused by divergent flux transport to replace closed flux on the dayside and (2) through accumulation of open flux magnetic flux in the tail lobes also caused by dayside reconnection. Both processes are expected to operate during any period of enhanced dayside reconnection. It is demonstrated that closed magnetic flux depletion (MFD) in the near Earth magnetotail and the increase of open lobe magnetic flux can lead to the evolution of two separate thin current sheets in the near Earth and the mid tail regions of the <span class="hlt">magnetosphere</span>. While the auroral morphology associated with MFD and near Earth current sheet formation is well consistent with typical <span class="hlt">substorm</span> growth observation, midtail current sheet formation through lobe flux increase shows only a minor influence on the auroral ionosphere. We discuss the physics of the dual current sheet formation and local and auroral properties of magnetic reconnection in either current sheet. It is suggested that only reconnection onset in the near Earth current sheet may be consistent with <span class="hlt">substorm</span> expansion because the flux tube entropy depletion of mid tail reconnection appears insufficient to cause geosynchronous particle injection and dipolarization. Therefore reconnection in the mid tail current sheet is more likely associated with bursty bulk flows or dipolarization fronts which stop short of geosynchronous distances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E.696D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E.696D"><span>``Polar'' and ``high-latitude'' <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Despirak, Irina; Lubchich, Andris; Kleimenova, Natalia</p> <p></p> <p>All <span class="hlt">substorms</span> observed at high latitudes can be divided into 2 types - "polar" (observed only at > 70º latitudes in the absence of <span class="hlt">substorms</span> at <70º latitudes during the day) and "high-latitude" <span class="hlt">substorms</span> (propagating from auroral (<70º) to polar (> 70º) geomagnetic latitudes). The aim of this study was to compare solar wind conditions during these two types of <span class="hlt">substorms</span>. For this purpose, we used the data of IMAGE magnetometers and OMNI solar wind data for 1995, 2000, 2006-2011 periods. There were selected 105 "polar" and 55 "high-latitude" <span class="hlt">substorms</span>. It is shown that "polar" <span class="hlt">substorms</span> observed during the late recovery phase of a geomagnetic storm, after passing of the high speed stream of the solar wind (when the velocity is reduced from high to low values). "High-latitude" <span class="hlt">substorms</span>, on the contrary, are observed during passing of the recurrent high-speed stream of the solar wind, increased values of the southward B _{Z }component of the IMF and E _{Y} component of the electric field, increased temperature and pressure of the solar wind. Also, it is noted that variability of these solar wind parameters for the “high-latitude” <span class="hlt">substorms</span> is stronger than for “polar” <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM11A2134B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM11A2134B"><span>Particle tracing modeling of ion fluxes at geosynchronous orbit during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brito, T. V.; Jordanova, V.; Woodroffe, J. R.; Henderson, M. G.; Morley, S.; Birn, J.</p> <p>2016-12-01</p> <p>The SHIELDS project aims to couple a host of different models for different regions of the <span class="hlt">magnetosphere</span> using different numerical methods such as MHD, PIC and particle tracing, with the ultimate goal of having a more realistic model of the whole <span class="hlt">magnetospheric</span> environment capturing, as much as possible, the different physics of the various plasma populations. In that context, we present a modeling framework that can be coupled with a global MHD model to calculate particle fluxes in the inner <span class="hlt">magnetosphere</span>, which can in turn be used to constantly update the input for a ring current model. In that regard, one advantage of that approach over using spacecraft data is that it produces a much better spatial and temporal coverage of the nightside geosynchronous region and thus a possibly more complete input for the ring current model, which will likely produce more accurate global results for the ring current population. In this presentation, we will describe the particle tracing method in more detail, describe the method used to couple it to the BATS-R-US 3D global MHD code, and the method used to update the flux results to the RAM-SCB ring current model. We will also present the simulation results for the July 18, 2013 period, which showed significant <span class="hlt">substorm</span> activity. We will compare simulated ion fluxes on the nightside <span class="hlt">magnetosphere</span> with spacecraft observations to gauge how well our simulations are capturing <span class="hlt">substorm</span> dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM31E4247S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM31E4247S"><span>Is Mercury's <span class="hlt">Magnetosphere</span> Driven By Flux Transfer Events?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slavin, J. A.</p> <p>2014-12-01</p> <p>Mercury's <span class="hlt">magnetosphere</span> closely resembles that of Earth in terms of its topology and structure, but major differences are found when their dynamics are compared. The strong interplanetary magnetic fields at 0.3 to 0.5 AU result in low Alfven Mach numbers, weak bow shocks and low plasma β magnetosheaths at Mercury. These conditions support the development of strong plasma depletion layers adjacent to the magnetopause and intense magnetopause reconnection. MESSENGER observations indicate that reconnection <span class="hlt">occurs</span> for all non-zero shear angles across the magnetopause with magnetosheat β being the primary factor controlling its rate. Flux transfer events (FTEs) with ~ 1-2 s durations and flux rope topology are observed during nearlly all magnetopause crossings. In contrast with the Earth where FTEs are typically observed every ~ 8 min, FTE ecounters at Mercury are separated on average by only ~ 10 s. At lower altitudes near the cusp MESSENGER observes ~1-2-s-long strong decreases in mgnetic field intensity that are termed cusp plasma filaments. These filaments are beleived to be formed by the inflow of magnetosheath plasma associated with flux transfer events. Mercury's magnetotail exhibits magnetic flux loading/unloading events similar to those observed at Earth during <span class="hlt">substorms</span>. The Dungey cycle durations and lobe flux loading amplitudes are ~ 2 - 3 min and ~ 30 to 50% at Mercury as compared to ~ 1 - 2 hr and ~ 10 to 25% at Earth. However, FTEs at Earth account for only a few per cent of the magnetic flux carried by the Dungey cycle, while the contribution of FTEs at Mercury is estimated to be ~ 30 to 50%. Mercury also differs from Earth in that it lacks an ionosphere, but possesses a large, highly conducting iron core. The strong IMF and lack of an ionosphere results in a relatively large dawn-to-dusk cross-<span class="hlt">magnetosphere</span> potential drop of ~ 30 kV at Mercury. Inductive coupling between Mercury's <span class="hlt">magnetosphere</span> and its large iron core stiffens the dayside</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060013071&hterms=Halloween&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHalloween','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060013071&hterms=Halloween&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHalloween"><span>Plasma Circulation in the <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, T. E.; Fok, Mei-Ching; Delcourt, D. C.; Slinker, S.; Fedder, J. A.; Buenfil, M.</p> <p>2006-01-01</p> <p>We investigate the global structure and dynamics of plasma circulation produced by prototypical solar wind disturbances of the interplanetary magnetic field and dynamic pressure. We track the global circulation and energization of solar wind, polar wind, and auroral wind plasmas throughout the <span class="hlt">magnetosphere</span>, until they precipitate or escape into the downstream solar wind. We use the full equations of motion of the plasma ions within fields produced by a global MHD simulation of the dynamic solar wind interaction. We use the dynamic hot plasma density and Poynting energy flux specified at the inner boundary of the MHD simulation as drivers of conjugate ion outflow fluxes using local empirical relations obtained from the FAST and Polar missions. Birkeland currents computed by the MHD code are used to derive a field-parallel potential drop from a Knight-like relation [as modified by Lyons and Evans, 1980]. This potential drop is applied to each ion as an initial bulk energy, added to a thermal heating driven by the locally incident Poynting flux. The solar wind pressure increase case (B(sub Y) = 5; B(sub z) = 0 nT) produces an immediate <span class="hlt">substorm</span> owing to compression of pre-existing plasmas. The SB(sub z), interval (embedded in NB(sub z)) produces a <span class="hlt">substorm</span> after about one hour of development. Both disturbances enhance the auroral wind flux and heavy ion pressure of the <span class="hlt">magnetosphere</span> substantially, with complex dynamic structuring by auroral acceleration vortexes and dynamic reconnection. Comparisons are made with observations during disturbed periods including the Halloween 2003 super-storm and other periods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060013071&hterms=Magnetosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMagnetosphere','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060013071&hterms=Magnetosphere&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DMagnetosphere"><span>Plasma Circulation in the <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, T. E.; Fok, Mei-Ching; Delcourt, D. C.; Slinker, S.; Fedder, J. A.; Buenfil, M.</p> <p>2006-01-01</p> <p>We investigate the global structure and dynamics of plasma circulation produced by prototypical solar wind disturbances of the interplanetary magnetic field and dynamic pressure. We track the global circulation and energization of solar wind, polar wind, and auroral wind plasmas throughout the <span class="hlt">magnetosphere</span>, until they precipitate or escape into the downstream solar wind. We use the full equations of motion of the plasma ions within fields produced by a global MHD simulation of the dynamic solar wind interaction. We use the dynamic hot plasma density and Poynting energy flux specified at the inner boundary of the MHD simulation as drivers of conjugate ion outflow fluxes using local empirical relations obtained from the FAST and Polar missions. Birkeland currents computed by the MHD code are used to derive a field-parallel potential drop from a Knight-like relation [as modified by Lyons and Evans, 1980]. This potential drop is applied to each ion as an initial bulk energy, added to a thermal heating driven by the locally incident Poynting flux. The solar wind pressure increase case (B(sub Y) = 5; B(sub z) = 0 nT) produces an immediate <span class="hlt">substorm</span> owing to compression of pre-existing plasmas. The SB(sub z), interval (embedded in NB(sub z)) produces a <span class="hlt">substorm</span> after about one hour of development. Both disturbances enhance the auroral wind flux and heavy ion pressure of the <span class="hlt">magnetosphere</span> substantially, with complex dynamic structuring by auroral acceleration vortexes and dynamic reconnection. Comparisons are made with observations during disturbed periods including the Halloween 2003 super-storm and other periods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..12010466E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..12010466E"><span><span class="hlt">Substorm</span> simulation: Formation of westward traveling surge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ebihara, Y.; Tanaka, T.</p> <p>2015-12-01</p> <p>Auroral <span class="hlt">substorm</span> expansion is characterized by initial brightening of aurora, followed by a bulge expanding in all directions, and a westward traveling surge (WTS). On the basis of the result obtained by a global magnetohydrodynamic simulation, we propose a scenario for the onset and the subsequent formation of WTS. (1) Near-Earth neutral line releases magnetic tension in the near-Earth plasma sheet to compress plasma and accelerate it earthward. (2) Earthward, perpendicular flow is converted to parallel flow in the near-Earth tail region. (3) Plasma moves earthward parallel to a field line. The plasma pressure is additionally enhanced at off-equator with an expanding slow-mode variation. (4) Flow vorticities coexist near the off-equatorial high-pressure region. Resultant field-aligned current (FAC) is connected to the ionosphere, which may manifest initial brightening. (5) Due to continued earthward flow, the high-plasma pressure region continues to expand to the east and west. (6) The ionospheric conductivity continues to increase in the upward FAC region, and the conductivity gradient becomes steeper. (7) The convergence of the Hall current gives rise to divergent electric field near the steep gradient of the conductivity. (8) Due to the divergent electric field, <span class="hlt">magnetospheric</span> plasma moves counterclockwise at low altitude (in the Northern Hemisphere). (9) The additional flow vorticity generates a localized upward FAC at low altitudes, which may manifest WTS, and redistributes the ionospheric current and conductivity. Thus, WTS may be maintained in a self-consistent manner, and be a natural consequence of the overflow of the Hall current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6966195','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6966195"><span>Nuclear magnetohydrodynamic EMP, solar storms, and <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rabinowitz, M. ); Meliopoulous, A.P.S.; Glytsis, E.N. . School of Electrical Engineering); Cokkinides, G.J. )</p> <p>1992-10-20</p> <p>In addition to a fast electromagnetic pulse (EMP), a high altitude nuclear burst produces a relatively slow magnetohydrodynamic EMP (MHD EMP), whose effects are like those from solar storm geomagnetically induced currents (SS-GIC). The MHD EMP electric field E [approx lt] 10[sup [minus] 1] V/m and lasts [approx lt] 10[sup 2] sec, whereas for solar storms E [approx gt] 10[sup [minus] 2] V/m and lasts [approx gt] 10[sup 3] sec. Although the solar storm electric field is lower than MHD EMP, the solar storm effects are generally greater due to their much longer duration. <span class="hlt">Substorms</span> produce much smaller effects than SS-GIC, but <span class="hlt">occur</span> much more frequently. This paper describes the physics of such geomagnetic disturbances and analyzes their effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780068607&hterms=IMP&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DIMP','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780068607&hterms=IMP&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DIMP"><span>Imp 6 measurements in the distant polar cusp during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fairfield, D. H.; Hones, E. W., Jr.</p> <p>1978-01-01</p> <p>High time-resolution data from the magnetic field, plasma, energetic particle, and VLF wave experiments performed aboard Imp 6 in a study of the distant dayside cusp during <span class="hlt">substorms</span> are described. The cusp was studied when its location was slightly equatorward of its normal location and the geomagnetic dipole was tilted in the appropriate direction. The data support both reconnection and diffusion as methods of particle entry to the <span class="hlt">magnetosphere</span>. The evidence (1) indicates an acceleration process to explain enhancements of 400 to 600-km/sec protons above their magnetosheath intensities, and (2) suggests convection of field lines over the polar cap as a means of explaining the lack of low-energy protons near the low-latitude boundary of the cusp. Magnetic field fluctuations, a perturbation vector, ion cyclotron waves, and an abrupt change in the intensity of both whistler waves and electrostatic waves are characterized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AdSpR..54.2549K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AdSpR..54.2549K"><span>Anthropogenic trigger of <span class="hlt">substorms</span> and energetic particles precipitations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuznetsov, V. D.; Ruzhin, Yu. Ya.</p> <p>2014-12-01</p> <p>The high-frequency (HF) emission in near-Earth space from various powerful transmitters (radio communications, radars, broadcasting, universal time and navigation stations, etc.) form an integral part of the modern world that it cannot do without. In particular, special-purpose research facilities equipped with powerful HF transmitters are used successfully for plasma experiments and local modification of the ionosphere. In this work, we are using the results of a complex space-ground experiment to show that exposure of the subauroral region to HF emission can not only cause local changes in the ionosphere, but can also trigger processes in the <span class="hlt">magnetosphere</span>-ionosphere system that result in intensive <span class="hlt">substorm</span> activity (precipitations of high-energy particles, aurorae, significant variations in the ionospheric parameters and, as a consequence, in radio propagation conditions).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E.755G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E.755G"><span><span class="hlt">Substorms</span> observations over Apatity during geomagnetic storms in the period 2012 - 2016</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guineva, Veneta; Werner, Rolf; Despirak, Irina; Kozelov, Boris</p> <p>2016-07-01</p> <p>In this work we studied <span class="hlt">substorms</span>, generated during enhanced geomagnetic activity in the period 2012 - 2016. Observations of the Multiscale Aurora Imaging Network (MAIN) in Apatity have been used. Solar wind and interplanetary magnetic field parameters were judged by the 1-min sampled OMNI data base. <span class="hlt">Substorm</span> onset and further development were verified by the 10-s sampled data of IMAGE magnetometers and by data of the all-sky camera at Apatity. Subject of the study were <span class="hlt">substorms</span> <span class="hlt">occurred</span> during geomagnetic storms. The so-called "St. Patrick's day 2015 event" (17-21 March 2015), the events on 17-18 March 2013 and 7-17 March 2012 (a chain of events generated four consecutive storms) which were among the events of strongest geomagnetic activity during the current solar cycle 24, were part of the storms under consideration. The behavior of the <span class="hlt">substorms</span> developed during different phases of the geomagnetic storms was discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970016602&hterms=Traveling+time&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DTraveling%2Btime','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970016602&hterms=Traveling+time&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DTraveling%2Btime"><span>Traveling compression region observed in the mid-tail lobes near <span class="hlt">substorm</span> expansion phase onset</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Taguchi, S.; Slavin, J. A.; Lepping, R. P.; Nose, M.</p> <p>1996-01-01</p> <p>The characteristics of traveling compression regions (TCRs) in the midtail lobes are examined. Through the use of the AL index, isolated <span class="hlt">substorm</span> events with well developed expansion phases are selected. The TCR events which feature a field compression coincident with modified Bz variations are categorized into different types, and the magnetic variations are interpreted in terms of the relative location of the point of observation to the plasmoid at the time of release and the effects of tail flaring. In order to understand the relationship between the plasmoid release time and the <span class="hlt">substorm</span> onset time, the time difference between the different types of TCR and the <span class="hlt">substorm</span> onset determined by Pi 2 pulsations at mid-latitude ground stations, is examined. The results suggest that the downtail release of most of the plasmoids created earthwards of -38 earth radii <span class="hlt">occurs</span> at almost the same distance as the <span class="hlt">substorm</span> onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970016602&hterms=tcr&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtcr','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970016602&hterms=tcr&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtcr"><span>Traveling compression region observed in the mid-tail lobes near <span class="hlt">substorm</span> expansion phase onset</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Taguchi, S.; Slavin, J. A.; Lepping, R. P.; Nose, M.</p> <p>1996-01-01</p> <p>The characteristics of traveling compression regions (TCRs) in the midtail lobes are examined. Through the use of the AL index, isolated <span class="hlt">substorm</span> events with well developed expansion phases are selected. The TCR events which feature a field compression coincident with modified Bz variations are categorized into different types, and the magnetic variations are interpreted in terms of the relative location of the point of observation to the plasmoid at the time of release and the effects of tail flaring. In order to understand the relationship between the plasmoid release time and the <span class="hlt">substorm</span> onset time, the time difference between the different types of TCR and the <span class="hlt">substorm</span> onset determined by Pi 2 pulsations at mid-latitude ground stations, is examined. The results suggest that the downtail release of most of the plasmoids created earthwards of -38 earth radii <span class="hlt">occurs</span> at almost the same distance as the <span class="hlt">substorm</span> onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060011203&hterms=shin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dshin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060011203&hterms=shin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dshin"><span>Average Characteristics of Triggered and Nontriggered <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hsu, Tung-Shin; McPherron, Robert L.</p> <p>2004-01-01</p> <p>Magnetic field data from ground stations, geosynchronous orbit, and magnetotail are examined to study the response to <span class="hlt">substorm</span> activity with and without apparent interplanetary magnetic field (IMF) perturbations. Global <span class="hlt">substorms</span> are identified using a sudden, persistent decrease in the AL index. The onset of this global expansion is taken to be the time of the Pi2 burst nearest to the beginning of the AL decrease. IMF triggers were identified subjectively through visual scanning of the data. Both northward turnings of the IMF B, and decreases in the amplitude of the By component were considered as possible triggers. Two different solar wind monitors were used in the investigation: IMP 8 in a circular orbit with a distance between approx.12 and approx.35 R(sub E) from the Earth-Sun line and ISEE 2 in an elliptical orbit with a distance of only approx.5- 10 R(sub E) from the Earth-Sun line. The results of superposed epoch analysis show that the temporal response from ground stations, geosynchronous orbit, and magnetotail are nearly identical for triggered (with apparent IMF perturbation) and nontriggered (without apparent IMF perturbation) <span class="hlt">substorms</span>. It is therefore concluded that the nontriggered <span class="hlt">substorms</span> are not a different form of activity than triggered <span class="hlt">substorms</span>. However, we demonstrate that the magnitude of the response is different for the two types of substo&. By every measure considered, triggered <span class="hlt">substorm</span> are systematically larger than nontriggered <span class="hlt">substorms</span>. We interpret the fact that nearly 40% of all <span class="hlt">substorms</span> cannot be associated with an IMF trigger as evidence that <span class="hlt">substorms</span> are caused by an internal instability. However, the fact that so many appear to be triggered suggests that this internal instability is susceptible to external perturbations by the IMF. The fact that triggered <span class="hlt">substorms</span> are larger than nontriggered <span class="hlt">substorms</span> is counterintuitive, and we have no explanation for the observation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990108480','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990108480"><span>Mercury's <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slavin, J. A.</p> <p>1999-01-01</p> <p>Among the major discoveries made by the Mariner 10 mission to the inner planets was the existence of an intrinsic magnetic field at Mercury with a dipole moment of approx. 300 nT R(sup 3, sub M). This magnetic field is sufficient to stand off the solar wind at an altitude of about 1 R(sub M) (i.e. approx. 2439 km). Hence, Mercury possesses a '<span class="hlt">magnetosphere</span>' from which the so]ar wind plasma is largely excluded and within which the motion of charged particles is controlled by the planetary magnetic field. Despite its small size relative to the <span class="hlt">magnetospheres</span> of the other planets, a Mercury orbiter mission is a high priority for the space physics community. The primary reason for this great interest is that Mercury unlike all the other planets visited thus far, lacks a significant atmosphere; only a vestigial exosphere is present. This results in a unique situation where the <span class="hlt">magnetosphere</span> interacts directly with the outer layer of the planetary crust (i.e. the regolith). At all of the other planets the topmost regions of their atmospheres become ionized by solar radiation to form ionospheres. These planetary ionospheres then couple to electrodynamically to their <span class="hlt">magnetospheres</span> or, in the case of the weakly magnetized Venus and Mars, directly to the solar wind. This <span class="hlt">magnetosphere</span>-ionosphere coupling is mediated largely through field-aligned currents (FACs) flowing along the magnetic field lines linking the <span class="hlt">magnetosphere</span> and the high-latitude ionosphere. Mercury is unique in that it is expected that FACS will be very short lived due to the low electrical conductivity of the regolith. Furthermore, at the earth it has been shown that the outflow of neutral atmospheric species to great altitudes is an important source of <span class="hlt">magnetospheric</span> plasma (following ionization) whose composition may influence subsequent magnetotail dynamics. However, the dominant source of plasma for most of the terrestrial <span class="hlt">magnetosphere</span> is the 'leakage'of solar wind across the magnetopause and more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA263568','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA263568"><span>The Aurora at Quiet <span class="hlt">Magnetospheric</span> Conditions: Repeatability and Dipole Tilt Angle Dependence</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-03-01</p> <p>A tial to variation of the dipole tilt angle. Wu et al. [1991] images of the aurora borealis obtained by Polar BEAR at studied the <span class="hlt">substorm</span> westward... Aurora at Quiet <span class="hlt">Magnetospheric</span> Conditions: SRepeatability and Dipole Tilt Angle Dependence PE 62101F _PR 4643 6. AUTHCR(S) TA 11 I. Oznovich*, R.W...tilt angle at quiet <span class="hlt">magnetospheric</span> conditions? In order to address these questions, northern hemisphere images of the aurora at 1356 A, obtained by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5256148','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5256148"><span><span class="hlt">Magnetosphere</span>-ionosphere coupling during plasmoid evolution: First results</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hesse, M.; Birn, J. )</p> <p>1991-07-01</p> <p>The influence of <span class="hlt">magnetosphere</span>-ionosphere coupling on the dynamic evolution of the magnetotail is investigated by a three-dimensional resistive MHD code that includes the effects of the closure of field-aligned currents in a simple resistive model ionosphere. Particular emphasis is on the role of this coupling during <span class="hlt">substorm</span> evolution and the modification of the latter by the convection driven by the ionospheric electric fields. For comparison, the authors present results from a simulation which uses an infinitely conducting ionosphere but is otherwise identical. Comparison of the two simulations shows that the major impact of <span class="hlt">magnetosphere</span>-ionosphere communication is an acceleration of magnetotail evolution. Otherwise, phenomena in the two models are qualitatively similar. They conclude that ionospheric effects do not significantly affect <span class="hlt">substorm</span> associated magnetotail dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860030351&hterms=traveling+ionospheric+disturbances&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtraveling%2Bionospheric%2Bdisturbances','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860030351&hterms=traveling+ionospheric+disturbances&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtraveling%2Bionospheric%2Bdisturbances"><span>Simulation of the westward traveling surge and Pi 2 pulsations during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kan, J. R.; Sun, W.</p> <p>1985-01-01</p> <p>The westward traveling surge and the Pi2 pulsations are simulated as a consequence of an enhanced <span class="hlt">magnetospheric</span> convection in a model of <span class="hlt">magnetosphere</span> coupling. The coupling is characterized by the bouncing of Alfven waves launched by the enhanced convection. The reflection of Alfven waves from the ionosphere is treated in which the height-integrated conductivity is allowed to be highly nonuniform and fully anisotropic. The reflection of Alfven waves from the <span class="hlt">magnetosphere</span> is characterized by the coefficient Rm, depending on whether the field lines are open or closed. The conductivity in the model is self-consistently enhanced with increasing upward field-aligned current density. The results of the simulation, including the convection pattern, the electrojets, the field-aligned current, the conductivity enhancement, the oscillation of the westward electrojet, and the average speed of the westward surge are in reasonable agreement with the features of the westward traveling surge and the Pi 2 pulsations observed during <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMSM41A1841M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMSM41A1841M"><span>A Catapult (Slingshot) Current Sheet Relaxation Model for <span class="hlt">Substorm</span> Triggering</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machida, S.; Miyashita, Y.; Ieda, A.</p> <p>2010-12-01</p> <p>Based on the results of our superposed epoch analysis of Geotail data, we have proposed a catapult (slingshot) current sheet relaxation model in which earthward flows are produced in the central plasma sheet (CPS) due to the catapult (slingshot) current sheet relaxation, together with the rapid enhancement of Poynting flux toward the CPS in the lobe around X ~ -15 Re about 4 min before the substrom onset. These earthward flows are characterized by plasma pressure decrease and large amplitude magnetic field fluctuations. When these flows reach X ~ 12Re in the magnetotail, they give significant disturbances to the inner <span class="hlt">magnetosphere</span> to initiate some instability such as a ballooning instability or other instabilities, and the <span class="hlt">substorm</span> starts in the inner <span class="hlt">magnetosphere</span>. The occurrence of the magnetic reconnection is a natural consequence of the initial convective earthward flows, because the relaxation of a highly stretched catapult current sheet produces a very thin current at its tailward edge being surrounded by intense magnetic fields which were formerly the off-equatorial lobe magnetic fields. Recently, Nishimura et al. [2010] reported that the <span class="hlt">substorm</span> onset begins when faint poleward discrete arcs collide with equatorward quiet arcs. The region of earthward convective flows correlatively moves earthward prior to the onset. Thus, this region of the earthward convective flows seems to correspond to the faint poleward discrete arcs. Interestingly, our statistical analysis shows that the earthward convective flows are not produced by the magnetic reconnection, but they are attributed to the dominance of the earthward JxB force over the tailward pressure associated with the progress of the plasma sheet thinning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900033691&hterms=magnitude&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dmagnitude','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900033691&hterms=magnitude&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dmagnitude"><span>On the relationship between the energetic particle flux morphology and the change in the magnetic field magnitude during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lopez, R. E.; Lui, A. T. Y.; Sibeck, D. G.; Takahashi, K.; Mcentire, R. W.</p> <p>1989-01-01</p> <p>The relationship between the morphology of energetic particle <span class="hlt">substorm</span> injections and the change in the magnetic field magnitude over the course of the event is examined. Using the statistical relationships between the magnetic field during the growth phase and the change in the field magnitude during <span class="hlt">substorms</span> calculated by Lopez et al. (1988), a limited number of dispersionless ion injections observed by AMPTE CCE are selected. It is argued that this limited set is representative of a large set of events and that the conclusions drawn from examining those events are valid for <span class="hlt">substorms</span> in general in the inner <span class="hlt">magnetosphere</span>. It is demonstrated that in an event when CCE directly observed the disruption of the current sheet, the particle and field data show that the region of particle acceleration was highly turbulent and was temporally, and perhaps spatially, limited and that the high fluxes of energetic particles are qualitatively associated with intense inductive electric fields.</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('http://hdl.handle.net/2060/20130008184','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130008184"><span>Pulsars <span class="hlt">Magnetospheres</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Timokhin, Andrey</p> <p>2012-01-01</p> <p>Current density determines the plasma flow regime. Cascades are non-stationary. ALWAYS. All flow regimes look different: multiple components (?) Return current regions should have particle accelerating zones in the outer <span class="hlt">magnetosphere</span>: y-ray pulsars (?) Plasma oscillations in discharges: direct radio emission (?)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140002251','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140002251"><span>Global Simulation of Proton Precipitation Due to Field Line Curvature During <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gilson, M. L.; Raeder, J.; Donovan, E.; Ge, Y. S.; Kepko, L.</p> <p>2012-01-01</p> <p>The low latitude boundary of the proton aurora (known as the Isotropy Boundary or IB) marks an important boundary between empty and full downgoing loss cones. There is significant evidence that the IB maps to a region in the <span class="hlt">magnetosphere</span> where the ion gyroradius becomes comparable to the local field line curvature. However, the location of the IB in the <span class="hlt">magnetosphere</span> remains in question. In this paper, we show simulated proton precipitation derived from the Field Line Curvature (FLC) model of proton scattering and a global magnetohydrodynamic simulation during two <span class="hlt">substorms</span>. The simulated proton precipitation drifts equatorward during the growth phase, intensifies at onset and reproduces the azimuthal splitting published in previous studies. In the simulation, the pre-onset IB maps to 7-8 RE for the <span class="hlt">substorms</span> presented and the azimuthal splitting is caused by the development of the <span class="hlt">substorm</span> current wedge. The simulation also demonstrates that the central plasma sheet temperature can significantly influence when and where the azimuthal splitting takes place.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMSM61A0452C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMSM61A0452C"><span>On the Lévy-Nature of Magnetic Field Fluctuations During <span class="hlt">Magnetospheric</span> Tail Current Disruption</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Consolini, G.; Lui, A. T.; Zimbardo, G.</p> <p>2002-12-01</p> <p>One of the most relevant phenomena <span class="hlt">occurring</span> at the <span class="hlt">substorm</span> onset is the development of a current wedge, which is responsible for the <span class="hlt">magnetosphere</span>-ionosphere coupling during magnetic <span class="hlt">substorms</span>. This current wedge is generally associated with the diversion or disruption of the near cross-tail current system [Lui, 1996]. In the last years this near-Earth dipolarization phenomenon has been the subject of several observation, as well as, simulation studies, which suggested a multiscale and a non-MHD nature of the phenomenon [Sitnov et al., 2000; Malova et al., 2000; Zelenyi et al., 2000; Miura, 2000]. Here, using magnetic field data relative to 3 current disruption (CD) events as observed by AMPTEE/CCE spacecraft, we investigate the statistical features of magnetic field fluctuations. In the kinetic domain (i.e. above the ion cyclotron frequency during CD) the distribution function of magnetic field fluctuations shows non Gaussian tails and the probability of return Pt(0) scales as t-α with α !=q 1/2 which is compatible with a Lévy-statistics. Conversely, in the magnetohydrodynamic (MHD) region CD magnetic fluctuations are compatible with a classical Brownian motion. These findings seem to indicate that the near-Earth dipolarization process, associated with CD, is a non-MHD phenomenon, during which fast kinetic processes in collisionless plasmas take place.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993EOSTr..74..356H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993EOSTr..74..356H"><span>Sources, transport, energization, and loss of <span class="hlt">magnetospheric</span> plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Horwitz, J. L.; Moore, T. E.</p> <p></p> <p>Sources, transport, energization, and loss of <span class="hlt">magnetospheric</span> plasma was the theme of the third Huntsville Workshop on <span class="hlt">Magnetospheric</span> Plasma Models, which was held in Guntersville, Ala., from October 4 to 8, 1992. Approximately ninety researchers attended the workshop, which was supported in part by a grant from the National Science Foundation.The first topical session summarized our knowledge of plasma distributions and set the stage for the later sessions. Dennis Gallagher reviewed the distributions of bulk parameters and reported on the new results of his empirical model of the plasmasphere. Ed Shelley traced the origins of the plasma sheet, concluding that medium-energy <span class="hlt">magnetospheric</span> plasma is of between 5 and 50% ionospheric origin. Tony Lui addressed the distribution of energetic particles and noted that the observed pressure gradients account for the field-aligned currents in the inner <span class="hlt">magnetosphere</span>. Dan Baker pointed out the glaring problem of how electrons gain relativistic energies during <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5132797','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5132797"><span>Multipoint observations of a small <span class="hlt">substorm</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lopez, R.E. Applied Research Corp., Landover, MD ); Luehr, H. ); Anderson, B.J.; Newell, P.T.; McEntire, R.W. )</p> <p>1990-11-01</p> <p>In this paper the authors present multipoint observations of a small <span class="hlt">substorm</span> which <span class="hlt">occurred</span> just after 0110 UT on April 25, 1985. The observations were made by spacecraft (AMPTE CCE, AMPTE IRM, DMSP F6, and DMSP F7), ground auroral stations (EISCAT magnetometer cross, Syowa, Narssarssuaq, Great Whale River, and Fort Churchill), and mid-latitude stations (Furstenfeldbruck, Toledo, and Argentine Island). These data provide them with a broad range of observations, including the latitudinal extent of the polar cap, visual identification of <span class="hlt">substorm</span> aurorae and the magnetic perturbations produced directly beneath them, in situ magnetic field and energetic particle observations of the disruption of the cross-tail current sheet, and observations concerning the spatial expansion of the current disruption region from two radially aligned spacecraft. The DMSP data indicate that the event took place during a period when the polar cap was relatively contracted, yet the disruption of the current sheet was observed by CCE at 8.56 R{sub E}. They have been able to infer a considerable amount of detail concerning the structure and westward expansion of the auroral features associated with the event, and they show that those auroral surges were located more than 10{degree} equatorward of the boundary between open and closed field lines. Moreover, they present evidence that the current sheet disruption observed by CCE in the neutral sheet was located on field lines which mapped to the westward traveling surge observed directly overhead of the ground station at Syowa. Furthermore, the observations strongly imply that disruption of the cross-tail current began in the near-Earth region and that it had a component of expansion which was radially antisunward.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM51B2183K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM51B2183K"><span>Particle Energization During Magnetic Storms with Steady <span class="hlt">Magnetospheric</span> Convection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kissinger, J.; Kepko, L.; Baker, D. N.; Kanekal, S. G.; Li, W.; McPherron, R. L.; Angelopoulos, V.</p> <p>2013-12-01</p> <p>Relativistic electrons pose a space weather hazard to satellites in the radiation belts. Although about half of all geomagnetic storms result in relativistic electron flux enhancements, other storms decrease relativistic electron flux, even under similar solar wind drivers. Radiation belt fluxes depend on a complex balance between transport, loss, and acceleration. A critically important aspect of radiation belt enhancements is the role of the 'seed' population--plasma sheet particles heated and transported Earthward by magnetotail processes--which can become accelerated by wave-particle interactions with chorus waves. While the effect of <span class="hlt">substorms</span> on seed electron injections has received considerable focus, in this study we explore how quasi-steady convection during steady <span class="hlt">magnetospheric</span> convection (SMC) events affects the transport and energization of electrons. SMC events are long-duration intervals of enhanced convection without any <span class="hlt">substorm</span> expansions, and are an important mechanism in coupling magnetotail plasma populations to the inner <span class="hlt">magnetosphere</span>. We detail the behavior of the seed electron population for stormtime SMC events using the Van Allen Probes in the outer radiation belt and THEMIS in the plasma sheet and inner <span class="hlt">magnetosphere</span>. Together, the two missions provide the ability to track particle transport and energization from the plasma sheet into the radiation belts. We present SMC events with Van Allen Probes/THEMIS conjunctions and compare plasma sheet fast flows/enhanced transport to radiation belt seed electron enhancements. Finally we utilize statistical analyses to quantify the relative importance of SMC events on radiation belt electron acceleration in comparison to isolated <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhDT.......166T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhDT.......166T"><span>Ion acceleration and transport mechanisms in the Earth's <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tung, Yeh-Kai</p> <p></p> <p>This thesis examines the role of ion transport and acceleration in the earth's <span class="hlt">magnetosphere</span> in two important areas: (1) the entry of solar wind ions in the cusp region on the dayside, and (2) the outflow of ions in the form of ion conics from the pre-midnight aurora. On November 15, 1996, the Polar and FAST satellites were in magnetic conjunction in the cusp region near magnetic local noon. The ion data show that the solar wind plasma injections were bursty in time, but were spatially coherent for 5 hours of magnetic local time. Ion sensors on the two satellites measured particle populations of different energies, but a time-of-flight analysis indicated that Polar and FAST were observing the same bursts of plasma injections from the reconnection region. A convection model was used to estimate the size of the plasma bursts observed. A plasma width of 2412 km was mapped out to the magnetopause to obtain a reconnection injection region latitudinal width of 1.4 to 1.5 RE. On the nightside, the FAST satellite has observed large ion outflow fluxes (>108 cm-2 s-1) in the form of auroral ion conics adjacent to the polar cap boundary. A statistical study was performed to quantify the occurrence of the ion conics in magnetic local time, the relation of the ion conics to <span class="hlt">substorms</span>, and the total contribution of the ion conics to the plasma sheet. The ion conics <span class="hlt">occur</span> near magnetic midnight and are associated with <span class="hlt">substorm</span> expansion phase but not exclusively. Furthermore, using Polar UVI images to estimate the width of the ion conics in local time and FAST ion data to determine the outflow fluxes and latitudinal extent, an estimate of 1022 to 1024 ions/sec is calculated for the outflow. When this outflow is assumed to persist over the duration of a 1000 sec <span class="hlt">substorm</span>, the total contribution of 1025 to 1027 ions is only 0.01% to 0.1% of the plasma sheet ion number 1030 ions. (Abstract shortened by UMI.)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.1697H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.1697H"><span><span class="hlt">Substorm</span> onset: Current sheet avalanche and stop layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haerendel, Gerhard</p> <p>2015-03-01</p> <p>A new scenario is presented for the onset of a <span class="hlt">substorm</span> and the nature of the breakup arc. There are two main components, current sheet avalanche and stop layer. The first refers to an earthward flow of plasma and magnetic flux from the central current sheet of the tail, triggered spontaneously or by some unknown interaction with an auroral streamer or a suddenly appearing eastward flow at the end of the growth phase. The second offers a mechanism to stop the flow abruptly at the interface between <span class="hlt">magnetosphere</span> and tail and extract momentum and energy to be partially processed locally and partially transmitted as Poynting flux toward the ionosphere. The stop layer has a width of the order of the ion inertial length. The different dynamics of the ions entering freely and the magnetized electrons create an electric polarization field which stops the ion flow and drives a Hall current by which flow momentum is transferred to the magnetic field. A simple formalism is used to describe the operation of the process and to enable quantitative conclusions. An important conclusion is that by necessity the stop layer is also highly structured in longitude. This offers a natural explanation for the coarse ray structure of the breakup arc as manifestation of elementary paths of energy and momentum transport. The currents aligned with the rays are balanced between upward and downward directions. While the avalanche is invoked for explaining the spontaneous <span class="hlt">substorm</span> onset at the inner edge of the tail, the expansion of the breakup arc for many minutes is taken as evidence for a continued formation of new stop layers by arrival of flow bursts from the near-Earth neutral line. This is in line with earlier conclusions about the nature of the breakup arc. Small-scale structure, propagation speed, and energy flux are quantitatively consistent with observations. However, the balanced small-scale currents cannot constitute the <span class="hlt">substorm</span> current wedge. The source of the latter must be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730004648','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730004648"><span>Can the ionosphere regulate <span class="hlt">magnetospheric</span> convection?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coroniti, F. V.; Kennel, C. F.</p> <p>1972-01-01</p> <p>Following a southward shift of the interplanetary magnetic field, which implies enhanced reconnection at the nose of the <span class="hlt">magnetosphere</span>, the magnetopause shrinks from its Chapman-Ferraro equilibrium position. If the convective return of magnetic flux to the magnetopause equalled the reconnection rate, the magnetopause would not shrink. Consequently, there is a delay in the development of <span class="hlt">magnetospheric</span> convection following the onset of reconnection, which is ascribed to line tying by the polar cusp ionosphere. A simple model relates the dayside magnetopause displacement to the currents feeding the polar cap ionosphere, from which the ionospheric electric field, and consequently, the flux return rate, may be estimated as a function of magnetopause displacement. Flux conservation arguments then permit an estimate of the time scale on which convection increases, which is not inconsistent with that of the <span class="hlt">substorm</span> growth phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070018262','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070018262"><span>Effects of Finite Element Resolution in the Simulation of <span class="hlt">Magnetospheric</span> Particle Motion</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hansen, Richard</p> <p>2006-01-01</p> <p>This document describes research done in conjunction with a degree program. The purpose of the research was to compare particle trajectories in a specified set of global electric and magnetic fields; to study the effect of mesh spacing, resulting in an evaluation of adequate spacing resolution; and to study time-dependent fields in the context of <span class="hlt">substorm</span> dipolarizations of the <span class="hlt">magnetospheric</span> tail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.P43A1024B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.P43A1024B"><span><span class="hlt">Magnetospheric</span> Storms at Saturn and Earth</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandt, P. C.; Mitchell, D. G.; Carbary, J.; Rymer, A.; Hill, M. E.; Paranicas, C.; Dougherty, M. K.; Young, D. T.</p> <p>2007-12-01</p> <p>The terrestrial <span class="hlt">magnetospheric</span> storms are a well-known phenomenon in which plasma from the solar wind and the ionosphere is convected into the inner <span class="hlt">magnetosphere</span> ("ring current") and energized by betatron acceleration and rapid changes in the magnetic field (<span class="hlt">substorms</span>). Here we compare terrestrial storm characteristics with similar, newly found characteristics of Saturn's <span class="hlt">magnetosphere</span>. We characterize Saturn's <span class="hlt">magnetospheric</span> response to solar wind variability by using remote energetic neutral atom (ENA) measurements with simultaneous in-situ solar wind measurements when Cassini was outside the Saturnian <span class="hlt">magnetosphere</span>. The Ion and Neutral Camera on board the Cassini spacecraft have obtained global energetic neutral atom (ENA) images of the hot plasma of Saturn's <span class="hlt">magnetosphere</span> since February 2004. INCA obtains ENA images in the ~3-200 keV/nuc of protons and O+. The typical observations show hot plasma distributed roughly between 6 to 30 RS orbiting the planet with a period around the 10h45min rotation period depending on energy and species. However, some observations show how ENA intensity builds up on the nightside during intervals longer than the rotation period which indicates a gradual source of plasma. The intervals are often ended by a dramatic ENA intensification followed by a rotation of the newly injected plasma around the planet. We have selected a few of such intervals when Cassini was in the solar wind and could obtain solar wind parameters and simulataneous ENA image sequences. We use the Magnetic Field Experiment (MAG), the Cassini Charge Energy Mass Spectrometer (CHEMS), and the Cassini Plasma Spectrometer Subsystem (CAPS) to study the IMF, solar wind speed and density during these events and find that Saturn's <span class="hlt">magnetospheric</span> activity most likely depends more on solar wind pressure than magnetic field orientation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.3333N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.3333N"><span>Coordinated ionospheric observations indicating coupling between preonset flow bursts and waves that lead to <span class="hlt">substorm</span> onset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nishimura, Y.; Lyons, L. R.; Nicolls, M. J.; Hampton, D. L.; Michell, R. G.; Samara, M.; Bristow, W. A.; Donovan, E. F.; Spanswick, E.; Angelopoulos, V.; Mende, S. B.</p> <p>2014-05-01</p> <p>A critical, long-standing problem in <span class="hlt">substorm</span> research is identification of the sequence of events leading to <span class="hlt">substorm</span> expansion phase onset. Recent Time History of Events and Macroscale Interactions during <span class="hlt">Substorms</span> (THEMIS) all-sky imager (ASI) array observations have shown a repeatable preonset sequence, which is initiated by a poleward boundary intensification (PBI) and is followed by auroral streamers moving equatorward (earthward flow in the plasma sheet) and then by <span class="hlt">substorm</span> onset. On the other hand, <span class="hlt">substorm</span> onset is also preceded by azimuthally propagating waves, indicating a possible importance of wave instability for triggering <span class="hlt">substorm</span> onset. However, it has been difficult to identify the link between fast flows and waves. We have found an isolated <span class="hlt">substorm</span> event that was well instrumented with the Poker Flat incoherent scatter radar (PFISR), THEMIS white-light ASI, and multispectral ASI, where the auroral onset <span class="hlt">occurred</span> within the PFISR and ASI fields of view. This <span class="hlt">substorm</span> onset was preceded by a PBI, and ionospheric flows propagated equatorward from the polar cap, crossed the PBI, and reached the growth phase arc. This sequence provides evidence that flows from open magnetic field lines propagate across the open-closed boundary and reach the near-Earth plasma sheet prior to the onset. Quasi-stable oscillations in auroral luminosity and ionospheric density are found along the growth phase arc. These preonset auroral waves amplified abruptly at the onset time, soon after the equatorward flows reached the onset region. This sequence suggests a coupling process where preexisting stable waves in the near-Earth plasma sheet interact with flows from farther downtail and then evolve to onset instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900047779&hterms=disruption&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Ddisruption','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900047779&hterms=disruption&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Ddisruption"><span>A current disruption mechanism in the neutral sheet - A possible trigger for <span class="hlt">substorm</span> expansions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lui, A. T. Y.; Mankofsky, A.; Chang, C.-L.; Papadopoulos, K.; Wu, C. S.</p> <p>1990-01-01</p> <p>A linear analysis is performed to investigate the kinetic cross-field streaming instability in the earth's magnetotail neutral sheet region. Numerical solution of the dispersion equation shows that the instability can <span class="hlt">occur</span> under conditions expected for the neutral sheet just prior to the onset of <span class="hlt">substorm</span> expansion. The excited waves are obliquely propagating whistlers with a mixed polarization in the lower hybrid frequency range. The ensuing turbulence of this instability can lead to a local reduction of the cross-tail current causing it to continue through the ionosphere to form a <span class="hlt">substorm</span> current wedge. A <span class="hlt">substorm</span> expansion onset scenario is proposed based on this instability in which the relative drift between ions and electrons is primarily due to unmagnetized ions undergoing current sheet acceleration in the presence of a cross-tail electric field. The required electric field strength is within the range of electric field values detected in the neutral sheet region during <span class="hlt">substorm</span> intervals. The skew in local time of <span class="hlt">substorm</span> onset location and the three conditions under which <span class="hlt">substorm</span> onset is observed can be understood on the basis of the proposed scenario.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900047779&hterms=triggers+alone&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtriggers%2Balone','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900047779&hterms=triggers+alone&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dtriggers%2Balone"><span>A current disruption mechanism in the neutral sheet - A possible trigger for <span class="hlt">substorm</span> expansions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lui, A. T. Y.; Mankofsky, A.; Chang, C.-L.; Papadopoulos, K.; Wu, C. S.</p> <p>1990-01-01</p> <p>A linear analysis is performed to investigate the kinetic cross-field streaming instability in the earth's magnetotail neutral sheet region. Numerical solution of the dispersion equation shows that the instability can <span class="hlt">occur</span> under conditions expected for the neutral sheet just prior to the onset of <span class="hlt">substorm</span> expansion. The excited waves are obliquely propagating whistlers with a mixed polarization in the lower hybrid frequency range. The ensuing turbulence of this instability can lead to a local reduction of the cross-tail current causing it to continue through the ionosphere to form a <span class="hlt">substorm</span> current wedge. A <span class="hlt">substorm</span> expansion onset scenario is proposed based on this instability in which the relative drift between ions and electrons is primarily due to unmagnetized ions undergoing current sheet acceleration in the presence of a cross-tail electric field. The required electric field strength is within the range of electric field values detected in the neutral sheet region during <span class="hlt">substorm</span> intervals. The skew in local time of <span class="hlt">substorm</span> onset location and the three conditions under which <span class="hlt">substorm</span> onset is observed can be understood on the basis of the proposed scenario.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........36P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........36P"><span>Mercury's <span class="hlt">Magnetospheric</span> Cusps and Cross-Tail Current Sheet: Structure and Dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poh, Gang Kai</p> <p></p> <p> sheets than the dusk side. Using the Harris current sheet model, we determined the peak current sheet current density and reported an asymmetry pattern for peak current density consistent with observed asymmetries in current sheet thickness. We propose that enhancement of heavy ions in the dusk side current sheet, due to centrifugal acceleration and gradient-curvature drift of ions from the cusp and current sheet, provides a partial explanation of the dawn-dusk current sheet asymmetries observed in this study. Furthermore, our results are consistent with earlier studies on reconnection-related structures and phenomenon, which suggest that the asymmetries observed in this study are associated with the asymmetric nature of magnetotail reconnection at Mercury. We also report the possible observation of an Earth-like <span class="hlt">substorm</span> current wedge in the near-Mercury magnetotail. We calculate the total current in the Hermean <span class="hlt">substorm</span> current wedge and found that the current close via the conductive planetary core. The current closure mechanism may be similar to the Region 1 currents observed in an earlier study. From the above results, we conclude that the plasma processes <span class="hlt">occurring</span> at Mercury are different from those at Earth due to difference in internal plasma composition, relative size of Mercury's <span class="hlt">magnetosphere</span> and solar wind conditions at small heliospheric distances, despite many structural similarities in both <span class="hlt">magnetospheres</span>. The results reported in this thesis have far-reaching implications for the physical processes in Mercury's <span class="hlt">magnetospheres</span> and those of the other planets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6907757','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6907757"><span>Association of plasma sheet variations with auroral changes during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hones, E.W. Jr.; Craven, J.D.; Frank, L.A.; Parks, G.K.</p> <p>1988-01-01</p> <p>Images of the southern auroral oval taken by the University of Iowa auroral imaging instrumentation on the Dynamics Explorer 1 satellite during an isolated <span class="hlt">substorm</span> are correlated with plasma measurements made concurrently by the ISEE 1 satellite in the magnetotail. Qualitative magnetic field configuration changes necessary to relate the plasma sheet boundary location to the latitude of the auroras are discussed. Evidence is presented that the longitudinal advances of the auroras after expansive phase onset are mappings of a neutral line lengthening across the near-tail. We observe a rapid poleward auroral surge, <span class="hlt">occurring</span> about 1 hour after expansive phase onset, to coincide with the peak of the AL index and argue that the total set of observations at that time is consistent with the picture of a /open quotes/poleward leap/close quotes/ of the electrojet marking the beginning of the <span class="hlt">substorm</span>'s recovery. 9 refs. 3 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910036193&hterms=1983&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D1983','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910036193&hterms=1983&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D1983"><span>The <span class="hlt">substorm</span> event of 28 January 1983 - A detailed global study</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baker, D. N.; Fairfield, D. H.; Slavin, J. A.; Richardson, I. G.; Craven, J. D.</p> <p>1990-01-01</p> <p>A comprehensive timeline of the growth, expansion, and recovery phases of a small isolated <span class="hlt">substorm</span> with an expansion phase onset at 07:39 U.T. on January 28, 1983 is provided. The data sets examined include those from the electron-plasma, magnetometer, and energetic-particle instruments onboard ISEE-3. In addition to these data sets, a number of other spacecraft and ground-based data is utilized, including the <span class="hlt">magnetospheric</span> energy-input rates evaluated in the upstream solar wind and imaging sequences used for examining auroral features during growth and expansion phases. <span class="hlt">Substorm</span> energy-input and -output relationships are estimated quantitatively, and the timing and physical dimensions of the distant tail disturbance implied by global observations available are evaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720023744','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720023744"><span><span class="hlt">Magnetospheric</span> electrons</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coroniti, F. V.; Thorne, R. M.</p> <p>1972-01-01</p> <p>Coupling of source, transport, and sink processes produces a fairly accurate model for the macroscopic structure and dynamics of <span class="hlt">magnetospheric</span> electrons. Auroral electrons are controlled by convective transport from a plasma sheet source coupled with a precipitation loss due to whistler and electrostatic plasma turbulence. Outer and inner zone electrons are governed by radial diffusion transport from convection and acceleration sources external to the plasmapause and by parasitic precipitation losses arising from cyclotron and Landau interactions with whistler and ion cyclotron turbulence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AdSpR..36.2077K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AdSpR..36.2077K"><span>Transport and acceleration of plasma in the <span class="hlt">magnetospheres</span> of Earth and Jupiter and expectations for Saturn</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kivelson, M. G.</p> <p></p> <p>The first comparative <span class="hlt">magnetospheres</span> conference was held in Frascati, Italy thirty years ago this summer, less than half a year after the first spacecraft encounter with Jupiter's <span class="hlt">magnetosphere</span> (Formisano, V. (Ed.), The <span class="hlt">Magnetospheres</span> of the Earth and Jupiter, Proceedings of the Neil Brice Memorial Symposium held in Frascati, Italy, May 28-June 1, 1974. D. Reidel Publishing Co., Boston, USA, 1975). Disputes highlighted various issues still being investigated, such as how plasma transport at Jupiter deviates from the prototypical form of transport at Earth and the role of <span class="hlt">substorms</span> in Jupiter's dynamics. Today there is a wealth of data on which to base the analysis, data gathered by seven missions that culminated with Galileo's 8-year orbital tour. We are still debating how magnetic flux is returned to the inner <span class="hlt">magnetosphere</span> following its outward transport by iogenic plasma. We are still uncertain about the nature of sporadic dynamical disturbances at Jupiter and their relation to terrestrial <span class="hlt">substorms</span>. At Saturn, the centrifugal stresses are not effective in distorting the magnetic field, so in some ways the <span class="hlt">magnetosphere</span> appears Earthlike. Yet the presence of plasma sources in the close-in equatorial <span class="hlt">magnetosphere</span> parallels conditions at Jupiter. This suggests that we need to study both Jupiter and Earth when thinking about what to anticipate from Cassini's exploration of Saturn's <span class="hlt">magnetosphere</span>. This paper addresses issues relevant to plasma transport and acceleration in all three <span class="hlt">magnetospheres</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GSL.....3...14B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GSL.....3...14B"><span>Introduction to the special issue on history development of solar terrestrial sciences including auroral <span class="hlt">sub-storms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balan, N.; Parks, G.; Svalgaard, L.; Kamide, Y.; Lui, T.</p> <p>2016-12-01</p> <p>Solar terrestrial (ST) sciences started centuries ago and branched into different disciplines. Starting with naked eye to highly sophisticated novel experimental techniques, observations have revealed the secrets of the Sun, heliosphere, <span class="hlt">magnetosphere</span>, plasmasphere, and ionosphere-atmosphere components of the ST system. Theories and theoretical models have been developed for the different components independently and together. World-wide efforts under different umbrella are being persuaded to understand the challenges of the ST system. The onset problem and role of O+ ions in <span class="hlt">sub-storm</span> physics are two issues that are hotly debated. The onset problem is whether <span class="hlt">sub-storm</span> is triggered by magnetic reconnection in the tail region at 15-20 Re or by a current disruption at ~12 Re. The issue on O+ role is whether O+ ions affect the dynamics of <span class="hlt">sub-storms</span> under magnetic storm and non-storm conditions differently. This special issue of Geoscience Letters contains a collection of 15 papers on the history and development of solar terrestrial sciences including auroral <span class="hlt">sub-storms</span>. Over half of the papers are based on the presentations in a session on the same topic organized at the AOGS (Asia Oceania geosciences Society) General Assembly held in Singapore during 02-07 August 2015. The rest of the papers from outside the assembly also falls within the theme of the special issue. The papers are organized in the order of history and development of ST coupling, <span class="hlt">sub-storms</span>, and outer heliosphere.</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('http://adsabs.harvard.edu/abs/2015AGUFMSM41E2518F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM41E2518F"><span>Characterizing the <span class="hlt">Magnetospheric</span> State for Sawtooth Events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fung, S. F.; Tepper, J. A.; Cai, X.</p> <p>2015-12-01</p> <p><span class="hlt">Magnetospheric</span> sawtooth events, first identified in the early 1990's, are named for their characteristic appearance of multiple quasi-periodic intervals of slow decrease followed by sharp increase of proton energy fluxes in the geosynchronous region. The successive proton flux decrease-and-increase intervals have been interpreted as recurrences of stretching and dipolarization, respectively, of the nightside geomagnetic field [Reeves et al., 2003]. Due to their often-extended intervals with 2- 10 cycles, sawteeth occurrences are sometimes referred to as a <span class="hlt">magnetospheric</span> mode [Henderson et al., 2006]. Studies over the past two decades of sawtooth events (both event and statistical) have yielded a wealth of information on the conditions for the onset and occurrence of sawtooth events, but the occurrences of sawtooth events during both storm and non-storm periods suggest that we still do not fully understand the true nature of sawtooth events [Cai et al., 2011]. In this study, we investigate the characteristic <span class="hlt">magnetospheric</span> state conditions [Fung and Shao, 2008] associated with the beginning, during, and ending intervals of sawtooth events. Unlike previous studies of individual sawtooth event conditions, <span class="hlt">magnetospheric</span> state conditions consider the combinations of both <span class="hlt">magnetospheric</span> drivers (solar wind) and multiple geomagnetic responses. Our presentation will discuss the most probable conditions for a "sawtooth state" of the <span class="hlt">magnetosphere</span>. ReferencesCai, X., J.-C. Zhang, C. R. Clauer, and M. W. Liemohn (2011), Relationship between sawtooth events and magnetic storms, J. Geophys. Res., 116, A07208, doi:10.1029/2010JA016310. Fung, S. F. and X. Shao, Specification of multiple geomagnetic responses to variable solar wind and IMF input, Ann. Geophys., 26, 639-652, 2008. Henderson, M. G., et al. (2006), <span class="hlt">Magnetospheric</span> and auroral activity during the 18 April 2002 sawtooth event, J. Geophys. Res., 111, A01S90, doi:10.1029/2005JA011111. Reeves, G. D., et al. (2004), IMAGE</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AdSpR..58.1968S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AdSpR..58.1968S"><span>Contribution of Latin-American scientists to the study of the <span class="hlt">magnetosphere</span> of the Earth. A review</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stepanova, M.; Valdivia, J. A.</p> <p>2016-11-01</p> <p>Since the very beginning of the space era, Latin-American scientists have been contributing to the understanding of the <span class="hlt">magnetosphere</span> of the Earth. This review summarizes some significant contributions in this field with emphasis on results obtained during the last decade. Special attention is paid to most important topics of the <span class="hlt">magnetosphere</span> of the Earth such as geomagnetic storms and <span class="hlt">substorms</span> and possible relations between them, interplanetary origin of storms, role of turbulent processes in the <span class="hlt">magnetosphere</span> dynamics, and analysis of the dynamics of the <span class="hlt">magnetosphere</span> as a complex self-organized non-linear system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790020957','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790020957"><span>Investigation of the <span class="hlt">magnetospheric</span> boundary plasma and magnetic field data from Explorers 33, 43, and 50</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Siscoe, G. L.; Crooker, N. U.</p> <p>1979-01-01</p> <p>Understanding of the plasma depletion process in the dayside magnetosheath, the nature of magnetotail boundary motion, and the geometry of the <span class="hlt">magnetospheric</span> boundary layers was examined. A model of the dayside boundary layers, based on the hypothesis that merging <span class="hlt">occurs</span> only for strictly anitparallel fields was developed which provides a qualitative solution to the problem of the half-wave rectifier response of the <span class="hlt">magnetosphere</span> to the solar wind electric field. Regarding magnetotail boundary motion, consideration of the data led to the conclusion that at lunar distance, <span class="hlt">substorms</span> are associated with very large amplitude compressional wave motion of the sausage type. A study of IMF orientation for depletion and nondepletion cases suggests that depletion is most likely to <span class="hlt">occur</span> for angles between the IMF and the normal to the magnetopause at the measurement location near 90 deg, in agreement with predictions. Observations of the heat flux in the dayside magnetosheath plasma suggest that the energized plasma ions have their source along a given flux tube at that intersection with the bow shock where the magnetic field is most compressed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM23C4253F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM23C4253F"><span>Elements of M-I Coupling in Repetitive <span class="hlt">Substorm</span> Activity Driven by Interplanetary CMEs</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.</p> <p>2014-12-01</p> <p>By means of case studies we explore key elements of the <span class="hlt">magnetosphere</span>-ionosphere current system associated with repetitive <span class="hlt">substorm</span> activity during persistent strong forcing by ICMEs. Our approach consists of a combination of the <span class="hlt">magnetospheric</span> and ionospheric perspectives on the <span class="hlt">substorm</span> activity. The first aspect is the near-Earth plasma sheet with its repetitive excitations of the <span class="hlt">substorm</span> current wedge, as monitored by spacecraft GOES-10 when it traversed the 2100-0300 MLT sector, and its coupling to the westward auroral electrojet (WEJ) centered near midnight during the stable interplanetary (IP) conditions. The second aspect is the excitation of Bostrom type II currents maximizing at dusk and dawn and their associated ionospheric Pedersen current closure giving rise to EEJ (WEJ) events at dusk (dawn). As documented in our study, this aspect is related to the braking phase of Earthward-moving dipolarization fronts-bursty bulk flows. We follow the <span class="hlt">magnetospheric</span> flow/field events from spacecraft Geotail in the midtail (X = - 11 Re) lobe to geostationary altitude at pre-dawn MLTs (GOES 10). The associated M-I coupling is obtained from ground-satellite conjunctions across the double auroral oval configuration along the meridian at dusk. By this technique we distinguish between ionospheric manifestations in three latitude regimes: (i) auroral oval south, (ii) auroral oval north, and (iii) polar cap. Regime (iii) is characterized by events of enhanced antisunward convection near the polar cap boundary (flow channel events) and in the central polar cap (PCN-index events). The repetitive <span class="hlt">substorm</span> activity is discussed in the context of the level of IP driving as given by the geoeffective IP electric field (E_KL), magnetotail reconnection (inferred from the PCN-index and spacecraft Wind at X = - 77 Re) and the storm SYM-H index. We distinguish between different variants of the repetitive <span class="hlt">substorm</span> activity, giving rise to electrojet (AL)-plasma convection (PCN) events</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM13D2555R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM13D2555R"><span>Plasmasphere pulsations observed simultaneously by midlatitude SuperDARN radars, ground magnetometers and THEMIS spacecraft during an auroral <span class="hlt">substorm</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruohoniemi, J. M.; Shi, X.; Baker, J. B. H.; Frissell, N. A.; Hartinger, M.; Liu, J.</p> <p>2015-12-01</p> <p>We present simultaneous ground and space-based observations of ultra-low frequency (ULF) pulsations which <span class="hlt">occurred</span> during an auroral <span class="hlt">substorm</span> on September 25th, 2014. Expansion phase onset began at 06:04 UT at which time three midlatitude SuperDARN radars observed strong pulsations in the Pi2 frequency range with peak to peak amplitude reaching as high as 1km/s. Similar pulsations <span class="hlt">occurred</span> during a later auroral intensification which started at 06:20 UT. Both sets of pulsations were detected in a region of radar backscatter located inside the subauroral polarization stream (SAPS) equatorward of the auroral oval specified by THEMIS all sky imagers and inside the midlatitude density trough as mapped by GPS/TEC measurements. The amplitude of the pulsations was large enough to reverse the direction of the SAPS flow from westward to eastward. Similar pulsations were detected by electric field instrument aboard the THEMIS probe D located inside the plasmasphere. Simultaneous observations from several low-latitude ground magnetometers (some located on the dayside) further illustrate the global nature of the pulsations and suggest they may have been associated with a plasmaspheric cavity resonance (PCR). Pulsed tailward plasma flow observed by THEMIS probe E at the geosynchronous orbit suggests that the compressional energy to generate the PCR was from the Bursty Bulk Flows (BBFs) braking against the <span class="hlt">magnetospheric</span> dipolar region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002cosp...34E.765K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002cosp...34E.765K"><span>Synoptic observations of space weather processes in the inner <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koskinen, H.</p> <p></p> <p>Space weather in the <span class="hlt">magnetosphere</span> is driven by coronal mass ejections and other solar wind disturbances. The <span class="hlt">magnetosphere</span> has, in turn, a remarkable capability of further processing the energy and plasma coming from the solar wind. One way of determining the severeness of magnetic storms is to estimate the strength of the westward ring current carried by ions at energies of tens of keV that are transported to the inner <span class="hlt">magnetosphere</span> by a complicated interplay between strengthening of the <span class="hlt">magnetospheric</span> convection and <span class="hlt">substorm</span>-related injections. A particularly intriguing phenomenon is the appearance of relativistic electrons all over the inner <span class="hlt">magnetosphere</span>. These electrons are sometimes called "killer electrons", as they have been assigned to several serious damages of satellites. Finally, most of the storm and <span class="hlt">substorm</span> energy is dissipated in the polar ionospheres through Joule heating and electron precipitation. Sometimes the ionospheric currents vary extremely fast and may induce damaging currents in the large electric conductors on the Earth's surface. In order to understand these and related processes in a global perspective it is essential to make simultaneous and continuous observations of the entire energy and plasma transfer chain from the surface of the Sun to the Earth. Perhaps of the most severely neglected region in this chain is the equatorial <span class="hlt">magnetosphere</span> from low altitudes out to the geostationary orbit, i.e., the region from the inner radiation belt to the outer parts of the ring current. A valuable improvement to this state of affairs would be to deploy at least three satellites to nearly geostationary transfer orbits with roughly evenly spaced lines of apsides. These satellites should carry well-focused instruments for studies of the most critical particle species with measurements of electric and magnetic fields. The operations of these satellites should be performed synoptically and well-correlated with other observations of the Sun, solar</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800065048&hterms=Wind+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DWind%2Bpower','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800065048&hterms=Wind+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DWind%2Bpower"><span>The energy coupling function and the power generated by the solar wind-<span class="hlt">magnetosphere</span> dynamo</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kan, J. R.; Lee, L. C.; Akasofu, S.-I.</p> <p>1980-01-01</p> <p>A solar wind parameter epsilon, known as the energy coupling function, has been shown to correlate with the power consumption in the <span class="hlt">magnetosphere</span>. It is shown in the present paper that the parameter epsilon can be identified semi-quantitatively as the dynamo power delivered from the solar wind to an open <span class="hlt">magnetosphere</span>. This identification not only provides a theoretical basis for the energy coupling function, but also constitutes an observational verification of the solar wind-<span class="hlt">magnetosphere</span> dynamo along the magnetotail. Moreover, one can now conclude that a <span class="hlt">substorm</span> results when the dynamo power exceeds 10 to the 18th erg/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800065048&hterms=wind+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwind%2Bpower','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800065048&hterms=wind+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwind%2Bpower"><span>The energy coupling function and the power generated by the solar wind-<span class="hlt">magnetosphere</span> dynamo</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kan, J. R.; Lee, L. C.; Akasofu, S.-I.</p> <p>1980-01-01</p> <p>A solar wind parameter epsilon, known as the energy coupling function, has been shown to correlate with the power consumption in the <span class="hlt">magnetosphere</span>. It is shown in the present paper that the parameter epsilon can be identified semi-quantitatively as the dynamo power delivered from the solar wind to an open <span class="hlt">magnetosphere</span>. This identification not only provides a theoretical basis for the energy coupling function, but also constitutes an observational verification of the solar wind-<span class="hlt">magnetosphere</span> dynamo along the magnetotail. Moreover, one can now conclude that a <span class="hlt">substorm</span> results when the dynamo power exceeds 10 to the 18th erg/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918779G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918779G"><span>Solar wind control of the local time of <span class="hlt">substorm</span> onset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grocott, Adrian; Case, Nathan; Laundal, Karl; Laurens, Hannah; Milan, Steve</p> <p>2017-04-01</p> <p>We use solar wind and interplanetary magnetic field data, along with satellite global auroral imagery, to investigate what controls the magnetic local time (MLT) of <span class="hlt">substorm</span> onset. We find that <span class="hlt">substorm</span> onsets <span class="hlt">occur</span> over a wide range of MLTs (18 - 4 hrs), with a typical MLT (mode) of 23 hrs. In agreement with previous studies, IMF BY , acts to move the onset to an earlier/later local time in the northern hemisphere and a later/earlier local time in the southern hemisphere, depending on the sign of BY , consistent with a twist of the conjugate magnetic field line. This effect explains a small fraction of the observed MLT variation (˜ 1 hr), but cannot account for the tendency of onset to be often displaced to earlier (< 23 hrs) or later (> 23 hrs) MLTs in both hemispheres. We also inspect the relationship between solar wind V Y and onset MLT, which also has a small, but measurable effect on the local time of <span class="hlt">substorm</span> onset. This effect acts in the same sense in the northern and southern hemispheres, moving onset to earlier times for positive V Y and later times for negative V Y . We find that a function relating both BY and V Y to onset MLT produces a better fit than a function based on either parameter alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM51C4259W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM51C4259W"><span>The Differences in Onset Time of Conjugate <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weygand, J. M.; Zesta, E.; McPherron, R. L.; Hsu, T. S.</p> <p>2014-12-01</p> <p>The auroral electrojet (AE) index is traditionally calculated from 13 ground magnetometer stations located around the typical northern auroral oval location. Similar coverage in the Southern Hemisphere index (SAE) does not exist, so the AE calculation has only been performed using Northern Hemisphere data. In the present study, we use seven southern auroral region ground magnetometers as well as their conjugate Northern Hemisphere data to calculate conjugate AE indices for 274 days covering all four seasons. With this dataset over 1200 <span class="hlt">substorm</span> onsets have been identified in the SAE index using the technique of Hsu et al. [2012]. A comparison of the SAE index with the world data center standard AE index shows that the <span class="hlt">substorm</span> onsets do not always <span class="hlt">occur</span> at the same time with differences on the order of several minutes. In this study we examine the differences in the onset time and the reason for those differences using our conjugate AE indices and using pairs of conjugate ground magnetometer stations. Specifically, we used the pair of stations at West Antarctica Ice Sheet Divide and Sanikiluaq, Canada and Syowa, Antarctica and Tjörnes, Iceland. The largest differences in onset time appear to be related to the IMF Bz and magnetic field line length. Differences on the order of minutes for the onset time of conjugate <span class="hlt">substorms</span> have serious implications for <span class="hlt">substorm</span> theories. The problem is that waves from a current disruption region to the mid tail, or flows from the mid tail to the current disruption region take the same amount of time (~2 minutes), which makes it difficult to decide where the onset disturbance is initiated, particularly when onset indicators have differences on the order of minutes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009Ge%26Ae..49..961K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009Ge%26Ae..49..961K"><span>Energetics of the <span class="hlt">magnetospheric</span> superstorm on November 20, 2003</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karavaev, Yu. A.; Sapronova, L. A.; Bazarzhapov, A. D.; Saifudinova, T. I.; Kuz'minykh, Yu. V.</p> <p>2009-12-01</p> <p>The <span class="hlt">magnetospheric</span> storm on November 20, 2003 was one of two greatest events in 1957-2003. The D {st/*} index reached -472 nT, the polar cap potential drop exceeded 200 kV, the polar cap boundary expanded up to Φ = 60°, the plasma layer density in the synchronous orbit reached 5 cm-3, and the inner edge of the plasma sheet penetrated up to L ˜ 1.5 R E. The sequence of disturbance modes including some previously unknown is described. The distribution of the total power input into the <span class="hlt">magnetosphere</span> between the ionosphere (power Q i) and the ring current ( Q DR), as well as the relative roles of the spontaneous <span class="hlt">substorms</span> and the driven disturbances in the creation of the DR current, is analyzed. The values of the parameter α = Q DR/ Q i are calculated with a step of 5 min. It is shown that intervals with α ≪ 1 and with maximums α ≫ 1 were observed in the events under consideration. These results contradict the dominant opinion that the energy input into the <span class="hlt">magnetosphere</span> during disturbances is primarily dissipated in the ionosphere. The two types of α maximums are observed: one in the mode of a prevailing spontaneous <span class="hlt">substorm</span> and the other in the mixed mode of the <span class="hlt">substorm</span> and driven disturbance. It is concluded that both types of the maximums and corresponding enhancements of the DR current appeared due to the plasma turbulization processes in the <span class="hlt">substorm</span> current wedge. The parameter α appears to slowly increase from α ≪ 1 to α > 1 with increasing activity level; this trend supports the driven model of creating the DR current due to an increase in the electric field of the solar wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM51E4283C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM51E4283C"><span>A Seasonal Study of Uranus' <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cao, X.; Paty, C. S.</p> <p>2014-12-01</p> <p>The <span class="hlt">magnetospheres</span> of the ice giant planets Uranus and Neptune are distinct from those of other major planets, including Earth, Jupiter or Saturn, because of their unique magnetic geometry: large obliquity, off-centered dipole moment, highly tilted angel between rotational axis and magnetic axis, and rapid rotation. We investigate the locations and shapes of critical boundary layers within these <span class="hlt">magnetospheres</span>, specifically the bow shock, magnetopause and magnetotail, in order to more fully understand the complex interaction of the solar wind with these planets. To perform this study, we implement a multifluid MHD simulation capable of modeling the interplanetary solar wind interaction with the intrinsic magnetic field of the ice giant planets. These simulations are useful in that they can track individual fluids for electrons and different ion species and sources, which is important for understanding the interaction at the ice giant planets where differentiating between natively sourced ionospheric ions and externally sourced solar wind ions may be necessary due to their inherently different temperatures and compositions. Our simulations demonstrate that Uranus has an asymmetric and dynamic <span class="hlt">magnetosphere</span> during solstice conditions, and that the asymmetry of <span class="hlt">magnetosphere</span> might be quasi-periodic with rotation. We also investigate the magnetic structure and current systems in the magnetotail region, which can be used to understanding the global transport of plasma within the <span class="hlt">magnetosphere</span> and hence dynamic responses to solar wind forcing and <span class="hlt">substorms</span>. We will also present new simulations of Uranus' global <span class="hlt">magnetosphere</span> for equinox conditions, and provide predictions for auroral locations which we will then place in the context of recent Hubble Space Telescope observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM12A..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM12A..04M"><span>Dynamic Particle Injections in the <span class="hlt">Magnetospheres</span> of the Solar System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mauk, B.</p> <p>2014-12-01</p> <p>The occurrence of dynamic, planetward injections of plasma and energetic particles on the nightside <span class="hlt">magnetosphere</span> is one of the defining characteristics of <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span> at Earth. And yet, with the exploration of the solar system with planetary probes, it has become clear that dynamic planetward injections are if fact a ubiquitous characteristic of most strongly magnetized planets; only Neptune did not reveal the signatures of such processes when visited. But, within this diversity of <span class="hlt">magnetospheric</span> environments, it is clear that the driving forces associated with injections can be very different from those at Earth. Jupiter, for example, is known to be powered by planetary rotation rather than the solar wind. Saturn has injections that are clearly powered by rotations, but it also has nightside injections that are, at minimum, triggered by solar wind events if not powered by the solar wind. Even for those <span class="hlt">magnetospheres</span> clearly powered by rotation, there appears to be substantial similarity between the physical processes involved with the extraterrestrial planetary injections and recent formulations of injections within Earth's near-Earth magnetotail. With a focus on comparisons between Earth, Jupiter, Saturn, Uranus and Neptune, I here review the state of understanding generally of injections within extraterrestrial planets and what the comparisons might tell us about our understanding of <span class="hlt">substorm</span> phenomena at Earth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990100919&hterms=BZ&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DBZ','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990100919&hterms=BZ&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DBZ"><span>Dynamics of the Auroral Luminosity Boundary of the Polar Cap During <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brittnacher, M. J.; Chua, D.; Fillingim, M. O.; Parks, G. K.; Spann, James F., Jr.; Germany, G. A.</p> <p>1999-01-01</p> <p>The area of the polar cap during <span class="hlt">substorms</span> has been measured using images from the Polar Ultraviolet Imager (UVI) for different interplanetary magnetic field (IMF) conditions. Changes in the poleward boundary of auroral luminosity have been analyzed in relation to <span class="hlt">substorm</span> phase and IMF orientation. Reconnection models of flux transport into the polar cap during the <span class="hlt">substorm</span> growth phase, and loss from the polar cap during the expansion phase, provide a framework by which these UVI observations can be analyzed. By comparison of the observations with the model predictions we can determine to what extent these models accurately predict the polar cap dynamics, and also where anomalous behavior calls for a new understanding of the dynamics beyond what these models provide. It was found that the polar cap boundary near noon and midnight usually shifted down in latitude by 1-2 degrees and 3-4 degrees respectively, increasing the area of the polar cap during the <span class="hlt">substorm</span> growth phase as predicted. However, this growth phase phenomenon also unexpectedly <span class="hlt">occurs</span> independently of the IMF Bz component, as shown for a <span class="hlt">substorm</span> on January 9, 1997. The polar cap area also increased due to motion of the dawn and dusk aurora to lower latitudes, although the latitudinal shifts were asymmetric, not always concurrent, and continued well into the <span class="hlt">substorm</span> expansion phase. The polar cap area decreased immediately following the expansion phase due to the poleward motion of the aurora on the nightside, consistent with the model prediction. What is not explained by the models is that the poleward auroral boundary in the nightside region sometimes reached very high latitudes (greater than 80 degrees MLat) greatly decreasing the polar cap area, independent of the magnitude of the <span class="hlt">substorm</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/820115','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/820115"><span>Physics of <span class="hlt">Substorm</span> Growth Phase, Onset, and Dipolarization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>C.Z. Cheng</p> <p>2003-10-22</p> <p>A new scenario of <span class="hlt">substorm</span> growth phase, onset, and depolarization during expansion phase and the corresponding physical processes are presented. During the growth phase, as a result of enhanced plasma convection, the plasma pressure and its gradient are continued to be enhanced over the quiet-time values in the plasma sheet. Toward the late growth phase, a strong cross-tail current sheet is formed in the near-Earth plasma sheet region, where a local magnetic well is formed, the plasma beta can reach a local maximum with value larger than 50 and the cross-tail current density can be enhanced to over 10nA/m{sup 2} as obtained from 3D quasi-static <span class="hlt">magnetospheric</span> equilibrium solutions for the growth phase. The most unstable kinetic ballooning instabilities (KBI) are expected to be located in the tailward side of the strong cross-tail current sheet region. The field lines in the most unstable KBI region map to the transition region between the region-1 and region-2 currents in the ionosphere, which is consistent with the observed initial brightening location of the breakup arc in the intense proton precipitation region. The KBI explains the AMPTE/CCE observations that a low-frequency instability with a wave period of 50-75 seconds is excited about 2-3 minutes prior to <span class="hlt">substorm</span> onset and grows exponentially to a large amplitude at the onset of current disruption (or current reduction). At the current disruption onset higher frequency instabilities are excited so that the plasma and electromagnetic field fluctuations form a strong turbulent state. Plasma transport takes place due to the strong turbulence to relax the ambient plasma pressure profile so that the plasma pressure and current density are reduced and the ambient magnetic field intensity increases by more than a factor of 2 in the high-beta(sub)eq region and the field line geometry recovers from tail-like to dipole-like dipolarization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....14163K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....14163K"><span>On the role of ground-based observations in <span class="hlt">substorm</span> research: Can one recognize the beast from its foot prints?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kauristie, K.</p> <p>2003-04-01</p> <p>The first coordinated efforts of ground-based auroral observations were carried out already during the International Geophysical Year (IGY) 1957-1958, during which all-sky camera pictures and magnetometer data were collected from several stations in the northern polar regions. This huge amount of data were later organized by Syun-Ichi Akasofu to describe the original auroral <span class="hlt">substorm</span> concept, main parts of which belong also to the wider <span class="hlt">magnetospheric</span> <span class="hlt">substorm</span> schema which started to build up when satellite observations became available. Also the IGY concept is still living strong as versatile networks of ground-based instruments support the ambitious international satellite missions (like Cluster or ILWS) investigating the different solar-terrestrial coupling processes. Many <span class="hlt">magnetospheric</span> <span class="hlt">substorm</span> processes have their own specific ionospheric signatures. Consequently, ground-based observations are often used to provide the background context that helps the interpretation of the localized <span class="hlt">magnetospheric</span> satellite observations. The possibility to analyse phenomena of very different scale sizes is a further advantage. With the modern high-resolution imagers auroral structures of less than kilometer-scale can be analysed. On the other hand, with the combination of the data of the global SuperDARN network and several magnetometer networks the entire polar cap convection and current pattern can be monitored. The development of various data analysis tools and assimilation methods has pushed the interpretation of ground-based data towards more quantitative analysis and resulted in several important findings. In the presentation we will discuss the benefits and pitfalls of ground-based observations, review the most important contributions to <span class="hlt">substorm</span> research, and envisage some of the future challenges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760016701','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760016701"><span>Trajectory Traces of Charged Particles in the <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ejiri, M.</p> <p>1976-01-01</p> <p>The characteristic enhancements of ring current particles with energies of about 1 to 100 keV, associated with <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>, were observed by Explorer 45 around the plasmapause in the afternoon to midnight region, and showed the characteristic structure called a 'nose' in the proton spectrograms. The motion of these particles in the equatorial <span class="hlt">magnetosphere</span>, under a recently proposed convection electric field and a dipole magnetic field is described. Approximate equations of a bounce period, a second adiabatic invariant, and a bounce-average azimuthal velocity are given with inaccuracies less than about 0.001 for all pitch angles. The complete set of flow patterns of 90 deg pitch angle particles is also presented by means of stagnation lines through which radial drifts and/or azimuthal drifts change their directions. The particle tracings in the <span class="hlt">magnetosphere</span> give a basic concept to explain the observed nose characteristics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AnGeo..35..365Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AnGeo..35..365Y"><span>Non-triggered auroral <span class="hlt">substorms</span> and long-period (1-4 mHz) geomagnetic and auroral luminosity pulsations in the polar cap</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yagova, Nadezda; Nosikova, Natalia; Baddeley, Lisa; Kozyreva, Olga; Lorentzen, Dag A.; Pilipenko, Vyacheslav; Johnsen, Magnar G.</p> <p>2017-03-01</p> <p>A study is undertaken into parameters of the polar auroral and geomagnetic pulsations in the frequency range 1-4 mHz (Pc5/Pi3) during quiet geomagnetic intervals preceding auroral <span class="hlt">substorms</span> and non-<span class="hlt">substorm</span> background variations. Special attention is paid to <span class="hlt">substorms</span> that <span class="hlt">occur</span> under parameters of the interplanetary magnetic field (IMF) conditions typical for undisturbed days (<q>non-triggered <span class="hlt">substorms</span></q>). The spectral parameters of pulsations observed in auroral luminosity as measured by a meridian scanning photometer (Svalbard) in the polar cap and near the polar boundary of the auroral oval are studied and compared with those for the geomagnetic pulsations measured by the magnetometer network IMAGE in the same frequency range. It is found that Pc5/Pi3 power spectral density (PSD) is higher during pre-<span class="hlt">substorm</span> time intervals than for non-<span class="hlt">substorm</span> days and that specific variations of pulsation parameters (</q><q><span class="hlt">substorm</span> precursors</q>) <span class="hlt">occur</span> during the last 2-4 pre-<span class="hlt">substorm</span> hours.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810013460','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810013460"><span>Plasmas in Saturn's <span class="hlt">magnetosphere</span></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.; Burek, B. G.; Ackerson, K. L.; Wolfe, J. H.; Mihalov, J. D.</p> <p>1980-01-01</p> <p>The solar wind plasma analyzer on board Pioneer 2 provides first observations of low-energy positive ions in the <span class="hlt">magnetosphere</span> of Saturn. Measurable intensities of ions within the energy-per-unit charge (E/Q) range 100 eV to 8 keV are present over the planetocentric radial distance range about 4 to 16 R sub S in the dayside <span class="hlt">magnetosphere</span>. The plasmas are found to be rigidly corotating with the planet out to distances of at least 10 R sub S. At radial distances beyond 10 R sub S, the bulk flows appear to be in the corotation direction but with lesser speeds than those expected from rigid corotation. At radial distances beyond the orbit of Rhea at 8.8 R sub S, the dominant ions are most likely protons and the corresponding typical densities and temperatures are 0.5/cu cm and 1,000,000 K, respectively, with substantial fluctuations. It is concluded that the most likely source of these plasmas in the photodissociation of water frost on the surface of the ring material with subsequent ionization of the products and radially outward diffusion. The presence of this plasma torus is expected to have a large influence on the dynamics of Saturn's <span class="hlt">magnetosphere</span> since the pressure ratio beta of these plasmas approaches unity at radial distances as close to the planet as 6.5 R sub S. On the basis of these observational evidences it is anticipated that quasi-periodic outward flows of plasma, accompanied with a reconfiguration of the <span class="hlt">magnetosphere</span> beyond about 6.5 R sub S, will <span class="hlt">occur</span> in the local night sector in order to relieve the plasma pressure from accretion of plasma from the rings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900029436&hterms=1983&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D1983','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900029436&hterms=1983&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D1983"><span><span class="hlt">Substorms</span>, plasmoids, flux robes, and magnetotail flux loss on March 25, 1983 - CDAW-8</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fairfield, D. H.; Baker, D. N.; Richardson, L. G.; Slavin, J. A.; Craven, J. D.; Frank, L. A.; Elphic, R. C.; Fennell, J. F.; Singer, H. J.; Tsurutani, B. T.</p> <p>1989-01-01</p> <p>During a 9-hour period following a storm-sudden commencement, six spacecraft near geosynchronous orbit, one over the pole, and three in the mgnetotail, monitored a complex sequence of <span class="hlt">magnetospheric</span> variations. Magnetic field compressions associated with the sudden commencement were seen first by the near-earth spacecraft and subsequently by the three down-tail spacecraft with increasing time delays that were consistent with the tailward movement of an interplanetary-shock-associated pressure enhancement. Ground magnetograms and synchronous orbit data are used to identify 7 <span class="hlt">substorm</span> intensifications during this geomagnetically active period. Six of these intensifications are clearly associated with tail lobe field decreases about 18 R sub E behind the earth. Four of these intensifications are followed by both Bz field increases in the tail lobes at about 18 and about 30 R sub E and by the subsequent observation of rapidly flowing plasma sheet plasma at ISEE 3 about 110 R sub E down the tail. During two <span class="hlt">substorms</span> where DE 1 was optically observing the auroral oval, the area of the polar cap was observed to decrease as the tail lobe field decreased at 18 R sub E. All these observations are consistent with the <span class="hlt">substorm</span> associated release of a plasmoid at a neutral line near 20 R sub E.</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://ntrs.nasa.gov/search.jsp?R=19990098449&hterms=Analysis+interaction+network&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAnalysis%2Binteraction%2Bnetwork','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990098449&hterms=Analysis+interaction+network&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAnalysis%2Binteraction%2Bnetwork"><span>Analysis of Auroral Morphology: <span class="hlt">Substorm</span> Precursor and Onset on January 10, 1997</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Germany, G. A.; Parks, G. K.; Ranganath, H.; Elsen, R.; Richards, P. G.; Swift, W.; Spann, J. F., Jr.; Brittnacher, M. J.</p> <p>1998-01-01</p> <p>The solar wind interaction with the geomagnetic field is studied using global auroral images obtained by the Ultraviolet Imager (UVI) on Polar. We study the dynam,cs of the poleward and equatorward boundaries of the auroral oval in response to the solar wind IMF on January 10, 1997 using a neural network algorithm to perform an automated morphological analysis. Poleward and equatorward boundaries identified by the algorithm demonstrate a clear growth motion with the southward turning of the IMF and growth and poleward expansion at <span class="hlt">substorm</span> onset. The area poleward of the oval (polar cap) is found to increase in size coincident with the'southward turning of the IMF Bz component at 0220 UT and peaks at <span class="hlt">substorm</span> onset at 0334 UT. The area of the oval, however, decreases continuously throughout the period of the polar cap area increase with a slight recovery observed during the <span class="hlt">substorm</span> onset. These observations are consistent with the concept that <span class="hlt">magnetospheric</span> dynamics are directly driven by the solar wind-geomagnetic field interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900049922&hterms=IRM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DIRM','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900049922&hterms=IRM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DIRM"><span>A multisatellite case study of the expansion of a <span class="hlt">substorm</span> current wedge in the near-earth magnetotail</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lopez, R. E.; Lui, A. T. Y.</p> <p>1990-01-01</p> <p>Results are presented on observations from four satellites (GOES 5, GOES 6, AMPTE CCE, and AMPTE IRM) and two ground stations (San Juan and Tucson) on a <span class="hlt">substorm</span> that <span class="hlt">occurred</span> on April 19, 1985 at about 0830 UT. The four spacecraft were arrayed in a configuration that made it possible to separate the effects arising from the longitudinal versus the radial expansion of the <span class="hlt">substorm</span> current wedge and thus to examine its spatial evolution. The sequence of events that was observed suggests that, during this <span class="hlt">substorm</span>, the disruption of the cross-tail current sheet, the formation of the <span class="hlt">substorm</span> current wedge, and the expansion of the plasma sheet began in the near-earth region, and subsequently spread tailward as well as longitudinally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120011855','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120011855"><span>Multi-Scale Modeling of <span class="hlt">Magnetospheric</span> Dynamics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuznetsova, M. M.; Hesse, M.; Toth, G.</p> <p>2012-01-01</p> <p>Magnetic reconnection is a key element in many phenomena in space plasma, e.g. Coronal mass Ejections, <span class="hlt">Magnetosphere</span> <span class="hlt">substorms</span>. One of the major challenges in modeling the dynamics of large-scale systems involving magnetic reconnection is to quantifY the interaction between global evolution of the <span class="hlt">magnetosphere</span> and microphysical kinetic processes in diffusion regions near reconnection sites. Recent advances in small-scale kinetic modeling of magnetic reconnection significantly improved our understanding of physical mechanisms controlling the dissipation in the vicinity of the reconnection site in collisionless plasma. However the progress in studies of small-scale geometries was not very helpful for large scale simulations. Global <span class="hlt">magnetosphere</span> simulations usually include non-ideal processes in terms of numerical dissipation and/or ad hoc anomalous resistivity. Comparative studies of magnetic reconnection in small scale geometries demonstrated that MHD simulations that included non-ideal processes in terms of a resistive term 11 J did not produce fast reconnection rates observed in kinetic simulations. In collisionless <span class="hlt">magnetospheric</span> plasma, the primary mechanism controlling the dissipation in the vicinity of the reconnection site is nongyrotropic pressure effects with spatial scales comparable with the particle Larmor radius. We utilize the global MHD code BATSRUS and replace ad hoc parameters such as "critical current density" and "anomalous resistivity" with a physically motivated model of dissipation. The primary mechanism controlling the dissipation in the vicinity of the reconnection site in incorporated into MHD description in terms of non-gyrotropic corrections to the induction equation. We will demonstrate that kinetic nongyrotropic effects can significantly alter the global <span class="hlt">magnetosphere</span> evolution. Our approach allowed for the first time to model loading/unloading cycle in response to steady southward IMF driving. The role of solar wind parameters and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1810544S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1810544S"><span>Mercury's Dynamic <span class="hlt">Magnetosphere</span>: What Have We Learned from MESSENGER?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slavin, James A.</p> <p>2016-04-01</p> <p>Mercury's <span class="hlt">magnetosphere</span> is created by the solar wind interaction with its dipolar, spin-axis aligned, northward offset intrinsic magnetic field. Structurally it resembles that of the Earth in many respects, but the magnetic field intensities and plasma densities are all higher at Mercury due to conditions in the inner solar system. <span class="hlt">Magnetospheric</span> plasma at Mercury appears to be primarily of solar wind origin, i.e. H+ and He++, but with 10% Na+ derived from the exosphere. Solar wind sputtering and other processes promote neutrals from the regolith into the exosphere where they may be ionized and incorporated into the <span class="hlt">magnetospheric</span> plasma population. At this point in time, about one year after MESSENGER's impact and one year prior to BepiColombo's launch, we review MESSENGER's observations of <span class="hlt">magnetospheric</span> dynamics and structure. In doing so we will provide our best answers to the following six questions: Question #1: How do magnetosheath conditions at Mercury differ from what is found at the other planets? Question #2: How do conditions in Mercury's magnetosheath contribute to the dynamic nature of Mercury's <span class="hlt">magnetosphere</span>? How does magnetopause reconnection at Mercury differ from what is seen at Earth? Are flux transfer events (FTEs) a major driver of <span class="hlt">magnetospheric</span> convection at Mercury? Question #3: Does reconnection ever erode the dayside <span class="hlt">magnetosphere</span> to the point where the subsolar region of the surface is exposed to direct solar wind impact? To what extent do induction currents driven in Mercury's interior limit the solar wind flux to the surface? Do FTEs contribute significantly to the solar wind flux reaching the surface? Question #4: What effects do heavy planetary ions have on Mercury's <span class="hlt">magnetosphere</span>? Question #5: Does Mercury's magnetotail store and dissipate magnetic energy in a manner analogous to <span class="hlt">substorms</span> at Earth? How is the process affected by the lack of an ionosphere and the expected high electrical resistivity of the crust? Question #6: How</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22133909','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22133909"><span>DYNAMICS OF STRONGLY TWISTED RELATIVISTIC <span class="hlt">MAGNETOSPHERES</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Parfrey, Kyle; Beloborodov, Andrei M.; Hui, Lam</p> <p>2013-09-10</p> <p>Magnetar <span class="hlt">magnetospheres</span> are believed to be strongly twisted due to shearing of the stellar crust by internal magnetic stresses. We present time-dependent axisymmetric simulations showing in detail the evolution of relativistic force-free <span class="hlt">magnetospheres</span> subjected to slow twisting through large angles. When the twist amplitude is small, the <span class="hlt">magnetosphere</span> moves quasi-statically through a sequence of equilibria of increasing free energy. At some twist amplitude the <span class="hlt">magnetosphere</span> becomes tearing-mode unstable to forming a resistive current sheet, initiating large-scale magnetic reconnection in which a significant fraction of the magnetic free energy can be dissipated. This ''critical'' twist angle is insensitive to the resistive length scale. Rapid shearing temporarily stabilizes the <span class="hlt">magnetosphere</span> beyond the critical angle, allowing the <span class="hlt">magnetosphere</span> of a rapidly differentially rotating star to store and dissipate more free energy. In addition to these effects, shearing the surface of a rotating star increases the spindown torque applied to the star. If shearing is much slower than rotation, the resulting spikes in spindown rate can <span class="hlt">occur</span> on timescales anywhere from the long twisting timescale to the stellar spin period or shorter, depending both on the stellar shear distribution and the existing distribution of <span class="hlt">magnetospheric</span> twists. A model in which energy is stored in the <span class="hlt">magnetosphere</span> and released by a <span class="hlt">magnetospheric</span> instability therefore predicts large changes in the measured spindown rate before soft gamma repeater giant flares.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMSM11C..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMSM11C..01S"><span><span class="hlt">Magnetospheric</span> Convection as a Global Force Phenomenon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siscoe, G.</p> <p>2007-12-01</p> <p>Since 1959 when Thomas Gold showed that motions in the <span class="hlt">magnetosphere</span> were possible despite plasma being frozen to the magnetic field, <span class="hlt">magnetospheric</span> convection as a subject of study has gone through several stages (to be reviewed) leading to a recent one that integrates convection into a global system of balance of forces. This area of research has opened by focusing on the region 1 current system as a carrier of force between the solar wind and the ionosphere/thermosphere fluid. An important result to emerge from it is the realization that the force that the solar wind delivers to the <span class="hlt">magnetosphere</span> in being transferred by the region 1 current system to the ionosphere/thermosphere fluid is amplified by about an order of magnitude. (Vasyliunas refers to this as "leveraging.") The apparent violation of Newton's Third Law results from the main participants in the force balance being not the solar wind force but the JxB force on the ionosphere/thermosphere fluid and the mu-dot-grad-B force on the Earth's dipole. This talk extends the study by considering the global force-balance problem separately for the Pedersen current (a completion of the region 1 problem), the Hall current (thus introducing the region 2 current system), and the Cowling current (bringing in the <span class="hlt">substorm</span> current wedge). The approach is through representing the ionosphere/thermosphere fluid by the shallow water equations. Novelties that result include force balance by means of tidal bulges and tidal bores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930007347','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930007347"><span>Inferences Concerning the <span class="hlt">Magnetospheric</span> Source Region for Auroral Breakup</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lyons, L. R.</p> <p>1992-01-01</p> <p>It is argued that the <span class="hlt">magnetospheric</span> source region for auroral arc breakup and <span class="hlt">substorm</span> initiation is along boundary plasma sheet (BPS) magnetic field lines. This source region lies beyond a distinct central plasma sheet (CPS) region and sufficiently far from the Earth that energetic ion motion violates the guiding center approximation (i.e., is chaotic). The source region is not constrained to any particular range of distances from the Earth, and <span class="hlt">substorm</span> initiation may be possible over a wide range of distances from near synchronous orbit to the distant tail. It is also argued that the layer of low-energy electrons and velocity dispersed ion beams observed at low altitudes on Aureol 3 is not a different region from the region of auroral arcs. Both comprise the BPS. The two regions occasionally appear distinct at low altitudes because of the effects of arc field-aligned potential drops on precipitating particles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.3564O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.3564O"><span>Lower thermospheric wind variations in auroral patches during the <span class="hlt">substorm</span> recovery phase</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Oyama, Shin-ichiro; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Hosokawa, Keisuke; Watkins, Brenton J.; Kurihara, Junichi; Tsuda, Takuo T.; Fallen, Christopher T.</p> <p>2016-04-01</p> <p>Measurements of the lower thermospheric wind with a Fabry-Perot interferometer (FPI) at Tromsø, Norway, found the largest wind variations in a night during the appearance of auroral patches at the <span class="hlt">substorm</span> recovery phase. Taking into account <span class="hlt">magnetospheric</span> <span class="hlt">substorm</span> evolution of plasma energy accumulation and release, the largest wind amplitude at the recovery phase is a fascinating result. The results are the first detailed investigation of the <span class="hlt">magnetosphere</span>-ionosphere-thermosphere coupled system at the <span class="hlt">substorm</span> recovery phase using comprehensive data sets of solar wind, geomagnetic field, auroral pattern, and FPI-derived wind. This study used three events in November 2010 and January 2012, particularly focusing on the wind signatures associated with the auroral morphology, and found three specific features: (1) wind fluctuations that were isolated at the edge and/or in the darker area of an auroral patch with the largest vertical amplitude up to about 20 m/s and with the longest oscillation period about 10 min, (2) when the convection electric field was smaller than 15 mV/m, and (3) wind fluctuations that were accompanied by pulsating aurora. This approach suggests that the energy dissipation to produce the wind fluctuations is localized in the auroral pattern. Effects of the altitudinal variation in the volume emission rate were investigated to evaluate the instrumental artifact due to vertical wind shear. The small electric field values suggest weak contributions of the Joule heating and Lorentz force processes in wind fluctuations. Other unknown mechanisms may play a principal role at the recovery phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AnGeo..30...67A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AnGeo..30...67A"><span><span class="hlt">Substorms</span> and polar cap convection: the 10 January 2004 interplanetary CME case</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andalsvik, Y.; Sandholt, P. E.; Farrugia, C. J.</p> <p>2012-01-01</p> <p>The expansion-contraction model of Dungey cell plasma convection has two different convection sources, i.e. reconnections at the magnetopause and in the magnetotail. The spatial-temporal structure of the nightside source is not yet well understood. In this study we shall identify temporal variations in the winter polar cap convection structure during <span class="hlt">substorm</span> activity under steady interplanetary conditions. <span class="hlt">Substorm</span> activity (electrojets and particle precipitations) is monitored by excellent ground-satellite DMSP F15 conjunctions in the dusk-premidnight sector. We take advantage of the wide latitudinal coverage of the IMAGE chain of ground magnetometers in Svalbard - Scandinavia - Russia for the purpose of monitoring magnetic deflections associated with polar cap convection and <span class="hlt">substorm</span> electrojets. These are augmented by direct observations of polar cap convection derived from SuperDARN radars and cross-track ion drift observations during traversals of polar cap along the dusk-dawn meridian by spacecraft DMSP F13. The interval we study is characterized by moderate, stable forcing of the <span class="hlt">magnetosphere</span>-ionosphere system (EKL = 4.0-4.5 mV m-1; cross polar cap potential (CPCP), Φ (Boyle) = 115 kV) during Earth passage of an interplanetary CME (ICME), choosing an 4-h interval where the magnetic field pointed continuously south-west (Bz < 0; By < 0). The combination of continuous monitoring of ground magnetic deflections and the F13 cross-track ion drift observations in the polar cap allows us to infer the temporal CPCP structure on time scales less than the ~10 min duration of F13 polar cap transits. We arrived at the following estimates of the dayside and nightside contributions to the CPCP (CPCP = CPCP/day + CPCP/night) under two intervals of <span class="hlt">substorm</span> activity: CPCP/day ~110 kV; CPCP/night ~50 kV (45% CPCP increase during <span class="hlt">substorms</span>). The temporal CPCP structure during one of the <span class="hlt">substorm</span> cases resulted in a dawn-dusk convection asymmetry measured by DMSP F13 which</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5806189','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5806189"><span>Dynamics of the 1054 UT March 22, 1979, <span class="hlt">substorm</span> event: CDAW 6</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McPherron, R.L.; Manka, R.H.</p> <p>1985-02-01</p> <p>The physical processes involved in the transfer of energy from the solar wind to the <span class="hlt">magnetosphere</span>, and release associated with <span class="hlt">substorms</span>, have been examined in a sequence of Coordinated Data Analysis Workshops (CDAW 6). Magnetic storms of March 22 and 31, 1979, were chosen to study the problem, using a data base from 13 spacecraft and about 130 ground-based magnetometers. This paper describes the March 22 storm, in particular the large, isolated <span class="hlt">substorm</span> at 1054 UT which followed an interval of magnetic calm. We summarize the observations in the solar wind, in various regions of the magnetosphre, and at the ground, synthesizing these observations into a description of the substorn development. We then give our interpretation of these observations and test their consistency with the reconnection model. The <span class="hlt">substorm</span> appears to have been generated by a southward turning of the interplanetary magnetic field associated with a current sheet crossing. Models of ionospheric currents derived from ground data show the <span class="hlt">substorm</span> had three phases of development. During the first phase, a two-celled convection current system developed in the polar cap as synchronous spacecraft on the nightside recorded an increasingly tailike field and the ISEE measurements show that the near-earth plasma sheet thinned. In the second phase, possibly triggered by sudden changes in the solar wind, a one-celled current system was added to the first, enhancing the westward electrojet. During this phase the synchronous orbit field became more dipolar, and the plasma sheet magnetic field turned strongly southward as rapid tailward flow developed soon after expansion onset, suggesting that a neutral line formed in the near-earth plasma sheet with subsequent plasmoid ejection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/236788','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/236788"><span>Dynamical effects of <span class="hlt">substorms</span> in the middle and lower latitude ionosphere. Ph.D. Thesis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pi, Xiaoqing</p> <p>1995-01-01</p> <p>The Earth`s ionosphere, a region of the the upper atmosphere spanning altitudes from approximately 100 to 1000 km, contains a complex pattern of electron densities produced by solar emissions, atmospheric chemistry and dynamical processes. In this dissertation, a plasma disturbance effect is identified in long-term observations, characterized statistically, and analyzed using numerical modeling. Results drawn from the model are subjected to verification using a dedicated observational campaign. The distinctive feature treated is a pattern of diurnal double maxima (DDM) in total electron content (TEC) observations. The observed DDM events have a clear relationship with geomagnetic disturbances known as <span class="hlt">substorms</span>. A time-dependent ionospheric model is used to simulate observed DDM events over a latitudinal range of +/- 38 deg. (dip latitude), and in two longitude sectors (75 deg. W and 7 deg. E). Modeling results show that TEC DDM patterns can be created by a combined effect of ionospheric F region plasma vertical drifts and highly altitude-dependent chemical loss mechanisms. Modeling studies explore two possible <span class="hlt">substorm</span>-related dynamical sources for these perturbation: <span class="hlt">magnetospheric</span> electric field penetration and overshielding effects, or traveling disturbances in the neutral atmosphere. Local time, latitudinal, and longitudinal characteristics of these dynamical perturbations are investigated in order to define global-scale signatures of the ionosphere`s response to <span class="hlt">substorms</span>. An observational campaign was formulated and conducted to verify model predictions. The techniques included: magnetometer in the auroral zone for indications of <span class="hlt">substorm</span> activity; incoherent scatter radars, from high to low latitudes near 75 deg. W longitude, to measure ionospheric electron densities, plasma drifts and meridional neutral winds; and all sky CCD cameras and a Fabry-Perot interferometer for 6300 A airglow and neutral winds at a sub-auroral site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SpWea..15..131G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SpWea..15..131G"><span>The <span class="hlt">substorm</span> cycle as reproduced by global MHD models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gordeev, E.; Sergeev, V.; Tsyganenko, N.; Kuznetsova, M.; Rastäetter, L.; Raeder, J.; Tóth, G.; Lyon, J.; Merkin, V.; Wiltberger, M.</p> <p>2017-01-01</p> <p>Recently, Gordeev et al. (2015) suggested a method to test global MHD models against statistical empirical data. They showed that four community-available global MHD models supported by the Community Coordinated Modeling Center (CCMC) produce a reasonable agreement with reality for those key parameters (the <span class="hlt">magnetospheric</span> size, magnetic field, and pressure) that are directly related to the large-scale equilibria in the outer <span class="hlt">magnetosphere</span>. Based on the same set of simulation runs, here we investigate how the models reproduce the global loading-unloading cycle. We found that in terms of global magnetic flux transport, three examined CCMC models display systematically different response to idealized 2 h north then 2 h south interplanetary magnetic field (IMF) Bz variation. The LFM model shows a depressed return convection and high loading rate during the growth phase as well as enhanced return convection and high unloading rate during the expansion phase, with the amount of loaded/unloaded magnetotail flux and the growth phase duration being the closest to their observed empirical values during isolated <span class="hlt">substorms</span>. Two other models exhibit drastically different behavior. In the BATS-R-US model the plasma sheet convection shows a smooth transition to the steady convection regime after the IMF southward turning. In the Open GGCM a weak plasma sheet convection has comparable intensities during both the growth phase and the following slow unloading phase. We also demonstrate potential technical problem in the publicly available simulations which is related to postprocessing interpolation and could affect the accuracy of magnetic field tracing and of other related procedures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170008032&hterms=bat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dbat','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170008032&hterms=bat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dbat"><span>The <span class="hlt">Substorm</span> Cycle as Reproduced by Global MHD Models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gordeev, E.; Sergee, V.; Tsyganenko, N.; Kuznetsova, M.; Rastaetter, Lutz; Raeder, J.; Toth, G.; Lyon, J.; Merkin, V.; Wiltberger, M.</p> <p>2017-01-01</p> <p>Recently, Gordeev et al. (2015) suggested a method to test global MHD models against statistical empirical data. They showed that four community-available global MHD models supported by the Community Coordinated Modeling Center (CCMC) produce a reasonable agreement with reality for those key parameters (the <span class="hlt">magnetospheric</span> size, magnetic field, and pressure) that are directly related to the large-scale equilibria in the outer <span class="hlt">magnetosphere</span>. Based on the same set of simulation runs, here we investigate how the models reproduce the global loading-unloading cycle. We found that in terms of global magnetic flux transport, three examined CCMC models display systematically different response to idealized2 h north then 2 h south interplanetary magnetic field (IMF) Bz variation. The LFM model shows a depressed return convection and high loading rate during the growth phase as well as enhanced return convection and high unloading rate during the expansion phase, with the amount of loaded unloaded magnetotail flux and the growth phase duration being the closest to their observed empirical values during isolated <span class="hlt">substorms</span>. Two other models exhibit drastically different behavior. In the BATS-R-US model the plasma sheet convection shows a smooth transition to the steady convection regime after the IMF southward turning. In the Open GGCM a weak plasma sheet convection has comparable intensities during both the growth phase and the following slow unloading phase. We also demonstrate potential technical problem in the publicly available simulations which is related to post processing interpolation and could affect the accuracy of magnetic field tracing and of other related procedures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM23B2551F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM23B2551F"><span>Integrated Observations of ICME - Driven <span class="hlt">Substorm</span> - Storm Evolution on 7 August 1998: Traditional and Non-Traditional Aspects.</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.; Torbert, R. B.</p> <p>2015-12-01</p> <p>The aim of this study is to obtain an integrated view of <span class="hlt">substorm</span>-storm evolution in relation to well-defined interplanetary (IP) conditions, and to identify traditional and non-traditional aspects of the DP1 and DP2 current systems during <span class="hlt">substorm</span> activity. Specifically, we report a case study of <span class="hlt">substorm</span>/storm evolution driven by an ICME from ground observations around the oval in relation to geoeffective IP parameters (Kan-Lee electric field, E-KL, and dynamic pressure, Pdyn), geomagnetic indices (AL, SYM-H and PCN) and satellite observations (from DMSP F13 and F14, Geotail, and GOES spacecraft). A sudden enhancement of E-KL at a southward turning of the IMF led to an initial transient phase (PCN-enhancement) followed by a persistent stage of solar wind-<span class="hlt">magnetosphere</span>-ionosphere coupling. The persistent phase terminated abruptly at a steep E-KL reduction when the ICME magnetic field turned north after a 3-hour-long interval of enhanced E-KL. The persistent phase consisted of (i) a 45-min-long <span class="hlt">substorm</span> growth phase (DP2 current) followed by (ii) a classical <span class="hlt">substorm</span> onset (DP1 current) in the 0100 - 0300 MLT sector, (ii) a 30-min-long expansion phase, maximizing in the same sector, and (iii) a phase lasting for 1.5 hr of 10-15 min-long DP1 events in the 2100 - 2300 and 0400 - 0600 MLT sectors. In the morning sector the expansion phase was characterized by Ps6 pulsations and omega bands. The SYM-H evolution reached the level of a major storm after a 2.5-hour-long interval of E-KL ˜5 mV/m and elevated Pdyn in the <span class="hlt">substorm</span> expansion phase. Magetosphere - Ionosphere (M - I) coupling during a localized electrojet event at 0500 MLT in the late stage of the <span class="hlt">substorm</span> expansion is studied by ground - satellite conjunction data (Iceland - Geotail). The DP1 and DP2 components of geomagnetic activity are discussed in relation to M - I current systems and <span class="hlt">substorm</span> current wedge morphology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740029898&hterms=Hardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DHardening','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740029898&hterms=Hardening&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DHardening"><span><span class="hlt">Substorm</span> effects in auroral spectra. [electron spectrum hardening</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Eather, R. H.; Mende, S. B.</p> <p>1973-01-01</p> <p>A <span class="hlt">substorm</span> time parameter is defined and used to order a large body of photometric data obtained on aircraft expeditions at high latitudes. The statistical analysis demonstrates hardening of the electron spectrum at the time of <span class="hlt">substorm</span>, and it is consistent with the accepted picture of poleward expansion of aurora at the time of <span class="hlt">substorm</span> and curvature drift of <span class="hlt">substorm</span>-injected electrons. These features are not evident from a similar analysis in terms of magnetic time. We conclude that the <span class="hlt">substorm</span> time concept is a useful ordering parameter for auroral data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E.783H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E.783H"><span>Dying Flow Bursts as Generators of the <span class="hlt">Substorm</span> Current Wedge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haerendel, Gerhard</p> <p>2016-07-01</p> <p>Many theories or conjectures exist on the driver of the <span class="hlt">substorm</span> current wedge, e.g. rerouting of the tail current, current disruption, flow braking, vortex formation, and current sheet collapse. Magnitude, spatial scale, and temporal development of the related magnetic perturbations suggest that the generator is related to the interaction of the flow bursts with the dipolar <span class="hlt">magnetosphere</span> after onset of reconnection in the near-Earth tail. The question remains whether it is the flow energy that feeds the wedge current or the internal energy of the arriving plasma. In this presentation I argue for the latter. The current generation is attributed to the force exerted by the dipolarized magnetic field of the flow bursts on the preceding layer of high-beta plasma after flow braking. The generator current is the grad-B current at the outer boundary of the compressed high-beta plasma layers. It needs the sequential arrival of several flow bursts to account for duration and magnitude of the ionospheric closure current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM51E2602H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM51E2602H"><span>Dying Flow Bursts as Generators of the <span class="hlt">Substorm</span> Current Wedge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haerendel, G.</p> <p>2015-12-01</p> <p>Many theories or conjectures exist on the driver of the <span class="hlt">substorm</span> current wedge, e.g. rerouting of the tail current, current disruption, flow braking, vortex formation, and current sheet collapse. Magnitude, spatial scale, and temporal development of the related magnetic perturbations suggest that the generator is related to the interaction of the flow bursts with the dipolar <span class="hlt">magnetosphere</span> after onset of reconnection in the near-Earth tail. The question remains whether it is the flow energy that feeds the wedge current or the internal energy of the arriving plasma. In this presentation I argue for the latter. The current generation is attributed to the force exerted by the dipolarized magnetic field of the flow bursts on the preceding layer of high-beta plasma after flow braking. The generator current is the grad-B current at the outer boundary of the compressed high-beta plasma layers. It needs the sequential arrival of several flow bursts to account for duration and magnitude of the ionospheric closure current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950063690&hterms=explosive&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dexplosive','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950063690&hterms=explosive&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dexplosive"><span>Formation of a very thin current sheet in the near-earth magnetotail and the explosive growth phase of <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, L. C.; Zhang, L.; Choe, G. S.; Cai, H. J.</p> <p>1995-01-01</p> <p>A magnetofricional method is used to construct two-dimensional MHD equilibria of the Earth's <span class="hlt">magnetosphere</span> for a given distribution of entropy functions(S = pV(exp gamma), where p is the plasma pressure and V is the tube volume per unit magnetic flux. It is found that a very thin current sheet with B (sub zeta) is less than 0.5 nu T and thickness less than 1000 km can be formed in the near-earth magnetotail (x is approximately -8 to -20R(sub e) during the growth phase of <span class="hlt">substorm</span>. The tail current sheets are found to become thinner as the entropy or the entropy gradient increases. It is suggested that the new entropy anti-diffusion instability associated with plasma transport across field lines leads to magnetic field dipolarization and accelerates the formation of thin current sheet, which may explain the observed explosive growth phase of <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050092348&hterms=1995&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D1995','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050092348&hterms=1995&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D1995"><span>Observations of Plasma Transient on the Lobe Field Line During the <span class="hlt">Substorm</span>. Interball Tail Observations on October 3, 1995</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Avanov, L. A.; Smimov, V. N.; Chandler, M. O.</p> <p>2004-01-01</p> <p>On October 3, 1995 Interball Tail spacecraft was located on tail lobe field lines. Solar wind conditions monitored by WIND and Getail spacecraft were quiet stable. During the time of operation of SCA-1 plasma spectrometer typical plasma mantle is observed. However, at approx. 15:07 UT strong plasma transient with duration of approx. 10 minutes was detected. We found that magnetic field profile of this plasma transient correlates well with ground based H component of magnetic field measured by Tixie Bay station. Ground base data indicates that this transient is observed during strong <span class="hlt">substorm</span>. We argue that this transient is probably more dense mantle plasma which can be observed at the Interball Tail location provided that the current on the magnetopause is depressed. This depression probably reflects response of the tail magnetopause to changing of the global current system of the <span class="hlt">magnetosphere</span> caused by the <span class="hlt">substorm</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM53A..08N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM53A..08N"><span>Van Allen Probes observations of dipolarization and its associated O+ flux variations in the inner <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nose, M.; Keika, K.; Kletzing, C.; Smith, C. W.; MacDowall, R. J.; Reeves, G. D.; Spence, H. E.</p> <p>2015-12-01</p> <p>Recent study employing the MDS-1 satellite reveals that magnetic field dipolarization in the deep inner <span class="hlt">magnetosphere</span> is not unusual. When the MDS-1 satellite was located at L=3.5-5.0 near the auroral onset longitude (MLT difference of ≤2.5 h), the occurrence probability of local dipolarization was about 16%. Surprisingly, an event was found at L~3.6, far inside the geosynchronous altitude. It was also shown that after the dipolarization, the oxygen ENA flux in the nightside ring current region measured by the IMAGE satellite was predominantly enhanced by a factor of 2-5 and stayed at an enhanced level for more than 1 h, while clear enhancement was scarcely seen in the hydrogen ENA flux. To better understand mechanisms of the selective acceleration of O+ ions during dipolarization, an in-situ measurement of ion fluxes is needed. However, there are few studies investigating H+ and O+ flux variations during dipolarization in the deep inner <span class="hlt">magnetosphere</span>. In this study we investigate magnetic field dipolarization and its associated ion flux variations in the deep inner <span class="hlt">magnetosphere</span>, using magnetic field and ion flux data obtained by the Van Allen Probes. From the magnetic field data recorded on the nightside (1800-0600 MLT) in the inner <span class="hlt">magnetosphere</span> (L=3.0-6.6) in VDH coordinates, we select <span class="hlt">substorm</span>-related dipolarization events in which the H component increases by more than 20 nT and the absolute value of the V component decreases by more than 8 nT in 5 minutes. About 150 dipolarization events are identified from 1 October 2012 to 30 June 2015. We find that the dipolarization mostly <span class="hlt">occurs</span> at L=4.5-6.5 in the premidnight sector (2100-0000 MLT). No events are found at L<4.0. Some dipolarization events are accompanied by O+ flux enhancements in the energy range higher than a few keV, which have the pitch angle distribution peaked around 45 or 135 degrees. We also find that low energy O+ ions often appear after dipolarization with an energy dispersion starting from</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://ntrs.nasa.gov/search.jsp?R=20080032584&hterms=evolution+bats&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Devolution%2Bbats','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080032584&hterms=evolution+bats&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Devolution%2Bbats"><span>Magnetotail Current Sheet Thinning and Magnetic Reconnection Dynamics in Global Modeling of <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kuznetsova, M. M.; Hesse, M.; Rastaetter, L.; Toth, G.; DeZeeuw, D. L.; Gombosi, T. I.</p> <p>2008-01-01</p> <p>Magnetotail current sheet thinning and magnetic reconnection are key elements of <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>. We utilized the global MHD model BATS-R-US with Adaptive Mesh Refinement developed at the University of Michigan to investigate the formation and dynamic evolution of the magnetotail thin current sheet. The BATSRUS adaptive grid structure allows resolving magnetotail regions with increased current density up to ion kinetic scales. We investigated dynamics of magnetotail current sheet thinning in response to southwards IMF turning. Gradual slow current sheet thinning during the early growth phase become exponentially fast during the last few minutes prior to nightside reconnection onset. The later stage of current sheet thinning is accompanied by earthward flows and rapid suppression of normal magnetic field component $B-z$. Current sheet thinning set the stage for near-earth magnetic reconnection. In collisionless <span class="hlt">magnetospheric</span> plasma, the primary mechanism controlling the dissipation in the vicinity of the reconnection site is non-gyrotropic effects with spatial scales comparable with the particle Larmor radius. One of the major challenges in global MHD modeling of the magnetotail magnetic reconnection is to reproduce fast reconnection rates typically observed in smallscale kinetic simulations. Bursts of fast reconnection cause fast magnetic field reconfiguration typical for <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>. To incorporate nongyritropic effects in diffusion regions we developed an algorithm to search for magnetotail reconnection sites, specifically where the magnetic field components perpendicular to the local current direction approaches zero and form an X-type configuration. Spatial scales of the diffusion region and magnitude of the reconnection electric field are calculated self-consistently using MHD plasma and field parameters in the vicinity of the reconnection site. The location of the reconnection sites and spatial scales of the diffusion region are updated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014P%26SS..101..135N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014P%26SS..101..135N"><span>An influence of long-lasting and gradual magnetic flux transport on fate of magnetotail fast plasma flows: An energetic particle injection <span class="hlt">substorm</span> event study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nowada, Motoharu; Fu, Suiyan; Parks, George K.; Pulkkinen, Tuija I.; Pu, Zuyin</p> <p>2014-10-01</p> <p>Based on multi-satellite and ground observations, we investigated an influence of long-lasting and gradual enhancements of magnetic flux transport rate on the magnetotail fast flow duration. On March 10th, 2009, THEMIS-B, which was located in the central plasma sheet of middle distant magnetotail (XGSM ~-25.8 RE), observed the fast flows with the velocity exceeding 300 km/s, lasting over 3 h for intense southward Interplanetary Magnetic Field (IMF) period. During long-lasting fast flows, AL index variations were very extensive and their recovery was much slow. Pi 2 waves were observed at the ground observatories around the THEMIS's footpoints and at low-/mid-latitudes. The aspect for these AL variations suggests Steady <span class="hlt">Magnetospheric</span> Convection (SMC), but clear <span class="hlt">substorm</span> signatures were also observed. Further magnetic dipolarization was detected by THEMIS-A at XGSM ~-8.2 RE and its nearby THEMIS-E. Only THEMIS-A observed the associated energetic electron flux enhancements. Therefore, the fast flows <span class="hlt">occurred</span> during <span class="hlt">substorm</span> with energetic particle injections at “imitative” SMC, which would be driven by prolonged intense southward IMF. The cumulative transport rates of magnetic and Poynting fluxes consecutively and gradually enhanced. On the other hand, THEMIS-C detected much shorter fast flows with the duration of 37 min at XGSM ~-18.1 RE and weak/gradual <span class="hlt">substorm</span>-associated dipolarization. However, the cumulative magnetic flux transport rate was enhanced only during the fast flow interval and was saturated after the fast flows. From different magnetic transport rate profiles at THEMIS-B and THEMIS-C, the realms of dipolar-configured field lines expanded to near THEMIS-C's position responsible for long-lasting fast flow-associated consecutive and gradual magnetic flux pileup. Because the resultant “high-speed flow braking” region was retreated into a few RE tailward direction, long-lasting fast flows were almost stemmed. These results suggest that the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730001666','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730001666"><span>Electron precipitation pattern and <span class="hlt">substorm</span> morphology</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoffman, R. A.; Burch, J. L.</p> <p>1972-01-01</p> <p>Patterns of the precipitation of low energy electrons observed by polar satellites were examined as functions of <span class="hlt">substorm</span> phase. Precipitation boundaries are generally identifiable at the low latitude edge of polar cusp electron precipitation and at the poleward edge of precipitation in the premidnight sector. Both of these boundaries move equatorward when the interplanetary magnetic field turns southward.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E2480P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E2480P"><span>The concept of Magnetically Driven <span class="hlt">Magnetosphere</span>: key ideas and findings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pavlov, Nikolai</p> <p></p> <p>The concept has been elaborated for several years and at COSPAR-2014 there is its first presentation. Motivation came from the need to resolve controversies existing in <span class="hlt">magnetospheric</span> physics and to achieve clear physical understanding of the observed processes. Novel solutions and ideas are found for the following topics: organization of geomagnetic field; scenarios of geomagnetic storm/<span class="hlt">substorm</span>; particle acceleration; magnetic reconnection; evolutions of the plasmasphere; convection and storm in polar ionosphere; field-aligned and cross-field electric-current systems; auroral kilometric radiation; structure of the magnetopause on flanks; seasonal modulation of geomagnetic activity; etc. It is expected to address all this in the presentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950038020&hterms=qualitative+observation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dqualitative%2Bobservation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950038020&hterms=qualitative+observation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dqualitative%2Bobservation"><span>Observations of Earthward and tailward propagating flux rope plasmoids: Expanding the plasmoid model of geomagnetic <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moldwin, Mark B.; Hughes, W. Jeffrey</p> <p>1994-01-01</p> <p>A survey of Interplanetary Monitoring Platform (IMP 8) magnetometer data for plasmoid signatures during <span class="hlt">magnetospheric</span> intervals from 1981 through 1983 found 16 plasmoids and 37 traveling compression regions as well as two earthward propagating flux ropes and 19 south-north bipolar lobe signatures. The properties of these relatively near-Earth plasmoids, traveling compression regions, and earthward propagating flux ropes and a qualitative model for their formation are presented. The plasmoids have estimated sizes, durations, magnetic field signatures, downtail velocities, and <span class="hlt">substorm</span> associations very similar to those of the plasmoids identified in International Sun-Earth Explorer (ISEE) 3 deep-tail observations. The occurrence frequency of these near-Earth plasma sheet plasmoids is significantly smaller than that of plasmoids found in the mid- and deep tail with ISEE 3. The earthward propagating flux ropes are characterized by a south-north bipolar turning in the Geocentric Solar <span class="hlt">Magnetospheric</span> (GSM) B(sub z) component, are localized near the noon-midnight meridional plane, and are strongly correlated with interplanetary magnetic field B(sub z) north and small isolated high latitude geomagnetic <span class="hlt">substorms</span>. These events are also apparently very rare and/or spatially localized. We propose that these structures are 'proto-plasmoids,' i.e., plasmoids for which near-Earth magnetic reconnection stopped before all the closed plasma sheet field lines were reconnected. The proto-plasmoids are then 'trapped' inside closed magnetic field lines and propagate earthward owing to the effect of the distant X-line's earthward plasma flow. We suggest that the two different 'types' of plasmoids are due to the different energy states of the <span class="hlt">magnetosphere</span> during periods of southward and northward interplanetary magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.P12B..07I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.P12B..07I"><span>MESSENGER observations of dayside flux transfer events: Do they drive Mercury's <span class="hlt">substorm</span> cycle? (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Imber, S. M.; Slavin, J. A.; Boardsen, S. A.; Anderson, B. J.; Korth, H.; Baker, D. N.; McNutt, R. L.; Solomon, S. C.</p> <p>2013-12-01</p> <p>The large-scale dynamics of Mercury's <span class="hlt">magnetosphere</span> appear to be predominantly driven by magnetic reconnection, which promotes the transfer of energy and momentum from the solar wind to the <span class="hlt">magnetosphere</span>. Reconnection thus also drives Mercury's <span class="hlt">substorm</span> cycle, which circulates magnetic flux through the system. The rate of reconnection taking place at any given time can be determined by observations of reconnection-related signatures such as plasma jets, large magnetic field components normal to the magnetopause, and flux transfer events (FTEs). FTEs are flux ropes formed by reconnection at Mercury's magnetopause which transport magnetic flux from the dayside to the lobes of the tail. Ninety orbits of magnetic field data were surveyed, taken in February and May 2012 when the MESSENGER orbit was generally in a noon-midnight configuration. Fifty-eight FTEs were identified in the magnetosheath, with a core field larger than the planetary magnetic field just inside the magnetopause. The orientation of the events was determined by minimum variance analysis of the magnetic field data, and the results suggest that the FTEs were formed by multiple X-line reconnection at low latitudes on the dayside magnetopause. We show that these large-amplitude FTEs can carry substantial amounts of magnetic flux, driving a cross-polar-cap potential of tens of kV. Further, we show that the <span class="hlt">substorm</span> cycle at Mercury is both shorter in duration and larger in relative amplitude than that observed at the Earth, and that these large-amplitude FTEs play a major role in magnetic flux transport throughout the <span class="hlt">magnetosphere</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AnGeo..27.1035M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AnGeo..27.1035M"><span>Statistical visualization of the Earth's magnetotail based on Geotail data and the implied <span class="hlt">substorm</span> model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Machida, S.; Miyashita, Y.; Ieda, A.; Nosé, M.; Nagata, D.; Liou, K.; Obara, T.; Nishida, A.; Saito, Y.; Mukai, T.</p> <p>2009-03-01</p> <p>We investigated the temporal and spatial development of the near-Earth magnetotail during <span class="hlt">substorms</span> based on multi-dimensional superposed-epoch analysis of Geotail data. The start time of the auroral break-up (t=0) of each <span class="hlt">substorm</span> was determined from auroral data obtained by the Polar and IMAGE spacecraft. The key parameters derived from the plasma, magnetic-field, and electric-field data from Geotail were sorted by their meridional X(GSM)-Z(proxy) coordinates. The results show that the Poynting flux toward the plasma-sheet center starts at least 10 min before the <span class="hlt">substorm</span> onset, and is further enhanced at X~-12 RE (Earth radii) around 4 min before the onset. Simultaneously, large-amplitude fluctuations <span class="hlt">occurred</span>, and earthward flows in the central plasma sheet between X~-11 RE and X~-19 RE and a duskward flow around X=-10 RE were enhanced. The total pressure starts to decrease around X=-16 RE about 4 min before the onset of the <span class="hlt">substorm</span>. After the <span class="hlt">substorm</span> onset, a notable dipolarization is observed and tailward flows commence, characterised by southward magnetic fields in the form of a plasmoid. We confirm various observable-parameter variations based on or predicted by the relevant <span class="hlt">substorm</span> models; however, none of these can explain our results perfectly. Therefore, we propose a catapult (slingshot) current-sheet relaxation model, in which an earthward convective flow produced by catapult current-sheet relaxation and a converted duskward flow near the Earth are enhanced through flow braking around 4 min before the <span class="hlt">substorm</span> onset. These flows induce a ballooning instability or other instabilities, causing the observed current disruption. The formation of the magnetic neutral line is a natural consequence of the present model, because the relaxation of a highly stretched catapult current-sheet produces a very thin current at its tailward edge being surrounded by intense earthward and tailward magnetic fields which were formerly the off-equatorial lobe magnetic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM11D..09S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM11D..09S"><span>Energy cascade in the <span class="hlt">magnetosphere</span>-ionosphere system: A case study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Semeter, J. L.; Dahlgren, H.; Akbari, H.; Swoboda, J.; Hampton, D. L.; Anderson, B. J.; Dyrud, L. P.; Fentzke, J.</p> <p>2013-12-01</p> <p>Common to all geomagnetic storms and <span class="hlt">substorms</span> is the phenomenon of energy cascade, wherein an impulsive change in <span class="hlt">magnetospheric</span> free energy is dissipated in a hierarchy of spatial and temporal scales at the ionospheric footprint, extending down to the fundamental scales available in the system (electron gyro-radius, electron inertial length). This paper investigates energy cascade through a synthesis of multi-scale measurements of a particular <span class="hlt">substorm</span> (onset at ~10 UT on 01 March 2011). Fortuitous space-based measurements from the AMPERE experiment document the regional intensification of field-aligned currents. Conjugate ground-optical measurements of the subsequent auroral breakup are found to represent the optical manifestation of time-energy dispersive field-aligned electron bursts (FABs) [Dahlgren et al., 2013]. The 449-MHz Poker Flat Incoherent Scatter Radar connects these features with ion-acoustic turbulence at the expanding edge of the <span class="hlt">substorm</span>. The connection of large scale <span class="hlt">substorm</span> currents with decameter-scale ionospheric turbulence fills an important observational gap in our understanding of <span class="hlt">magnetosphere</span>-ionosphere coupling under disturbed conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750058178&hterms=atmosphere+super+earth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Datmosphere%2Bsuper%2Bearth','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750058178&hterms=atmosphere+super+earth&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Datmosphere%2Bsuper%2Bearth"><span>Is Jupiter's <span class="hlt">magnetosphere</span> like a pulsar's or earth's</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kennel, C. F.; Coroniti, F. V.</p> <p>1975-01-01</p> <p>Two possible models of Jupiter's <span class="hlt">magnetosphere</span> are compared: a pulsar-like radial-outflow model and an earth-like convection model. For the radial-outflow model, Pioneer 10 data are used to estimate the total particle and energy fluxes which must be provided by Jupiter (or its <span class="hlt">magnetosphere</span> within the Alfven radius) to power the outflow. The convection model is considered with emphasis on field-line reconnection, convection flow time, and the location of Jupiter's magnetopause and plasmapause. The imposition of corotation on Jupiter's ionosphere, <span class="hlt">magnetosphere</span>, and upper atmosphere is investigated in terms of an aligned rotator with either type of <span class="hlt">magnetosphere</span>. It is concluded that: (1) Jupiter's convection flow is likely to be super-Alfvenic in its outer <span class="hlt">magnetosphere</span>, (2) Jupiter may have earth-like magnetopauses near local dawn during <span class="hlt">substorms</span>, (3) the angular-momentum flux that can diffuse upward through Jupiter's polar-cap atmospheres seems insufficient to impose corotation upon a radial outflow or convective return flow, and (4) neither model can be definitively accepted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009APS..DPPUO6008K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009APS..DPPUO6008K"><span>Enabling Global Kinetic Simulations of the <span class="hlt">Magnetosphere</span> via Petascale Computing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karimabadi, H.; Vu, H. X.; Omelchenko, Y. A.; Tatineni, M.; Majumdar, A.; Catalyurek, U. V.; Saule, E.</p> <p>2009-11-01</p> <p>The ultimate goal in <span class="hlt">magnetospheric</span> physics is to understand how the solar wind transfers its mass, momentum and energy to the <span class="hlt">magnetosphere</span>. This problem has turned out to be much more complex intellectually than originally thought. MHD simulations have proven useful in predicting eminent features of <span class="hlt">substorms</span> and other global events. Given the complexity of solar wind-<span class="hlt">magnetosphere</span> interactions, hybrid (electron fluid, kinetic ion) simulations have recently been emerging in the studies of the global dynamics of the <span class="hlt">magnetosphere</span> with the goal of accurately predicting the energetic particle transport and structure of plasma boundaries. We take advantage of our recent innovations in hybrid simulations and the power of massively parallel computers to make breakthrough 3D global kinetic simulations of the <span class="hlt">magnetosphere</span>. The preliminary results reveal many major differences with global MHD simulations. For example, the hybrid simulations predict the formation of the quadruple structure associated with reconnection events, ion/ion kink instability in the tail, turbulence in the magnetosheath, and formation of the ion foreshock region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM43A4263K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM43A4263K"><span>A Statistical Study of EMIC Waves Observed at THEMIS Probes in the Outer (L > 7) <span class="hlt">Magnetosphere</span> Under Quiet Geomagnetic Conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, G. J.; Kim, K. H.; Park, J. S.; Lee, E.; Lee, D. H.</p> <p>2014-12-01</p> <p>Electromagnetic ion cyclotron (EMIC) waves can be generated in the equatorial <span class="hlt">magnetosphere</span> by an anisotropic temperature distribution (T⊥>T∥) of energetic (10-100 keV) ions. They are typically observed in the afternoon sector with a wide L range (L > 7) and <span class="hlt">occur</span> near the plasmapause. Thus, it has been suggested that the distribution of EMIC wave occurrence in the afternoon sector is associated with the plasmaspheric expansion (i.e., plasmapsheric bulge or plume). Since the plasmapause is further away the earth during times of low geomagnetic activity, it is expected that EMIC wave's spatial distribution under quiet geomagnetic conditions could be different from that under averaged geomagnetic conditions. In our study we investigate the spatial distribution of EMIC waves during quiet geomagnetic conditions (Kp ≤ 1) in the outer <span class="hlt">magnetosphere</span> (L > 7) using the magnetic field data from Time History of Events and Macroscale Interactions during <span class="hlt">Substorms</span> (THEMIS) spacecraft from 2008 to 2009. We also examine the spatial distribution of cold plasma density estimated from THEMIS spacecraft potential data and compare it with EMIC wave occurrence during quiet geomagnetic conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM41D2501C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM41D2501C"><span>Electric Fields Associated with Deep Injections of 10s to 100s keV Electrons in the Inner <span class="hlt">Magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Califf, S.; Li, X.; Jaynes, A. N.; Zhao, H.; Malaspina, D.</p> <p>2015-12-01</p> <p>Recent observations by HOPE and MagEIS onboard the Van Allen Probes show frequent penetration of 10s to 100s keV electrons through the slot region and into the inner belt, resulting in an abundant electron population below L=3. The conventional picture is that the source populations of these 10s to 100s keV electrons originate in the plasma sheet and are injected (along with plasma sheet ions) into the inner <span class="hlt">magnetosphere</span> either through enhancements in the large-scale convection electric field and/or through earthward propagating dipolarization fronts associated with <span class="hlt">substorms</span>. In such cases the inward radial limit of the injections should coincide with the plasmapause. However, these electron injections often extend inside the plasmasphere, are observed far earthward of the typically accepted "flow-braking" region for dipolarization fronts, and <span class="hlt">occur</span> at much lower L shells than injections of ions with similar energies. We investigate the electric fields associated with these deep electron injections using data from the Van Allen Probes and THEMIS in order to shed light on the underlying mechanisms that allow them to penetrate so far into the inner <span class="hlt">magnetosphere</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790002098','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790002098"><span>A set of satellite experiments for studying the <span class="hlt">magnetosphere</span>-ionosphere communications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gringauz, K. I.</p> <p>1978-01-01</p> <p><span class="hlt">Magnetospheric</span> <span class="hlt">substorms</span> are one of the basic problems in the physics of near earth space. They appear as magnetic and ionospheric perturbations, disturbances in radio communication, polar auroras and electromagnetic radiation in different frequency ranges. These phenomena were studied from single satellites. However, it is impossible to study these phenomena adequately without simultaneous measurements from at least two different positions with identical instruments. A suitable program can be developed based on the Interkosmos work using new achievements in electronics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720007674','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720007674"><span>Electric field variations during <span class="hlt">substorms</span>: OGO-6 measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Heppner, J. P.</p> <p>1972-01-01</p> <p>The OGO-6 electric field measurements make it clear that the general pattern of high latitude electric fields in magnetic time-invariant latitude coordinates is not highly variable and that when unusual variations, or field distributions, <span class="hlt">occur</span> they are relatively isolated in time and spatial extent. Thus, electric field changes on a global scale cannot, in general, be evoked as a direct cause of <span class="hlt">substorms</span>. Polar traverses along the 18(h) to 6(h) magnetic time meridian show that the sum of potential drops across the evening auroral belt and morning auroral belt approximately equals the potential drop across the polar cap. The integrated polar cap potential drop ranges from 20 to 100 keV and values in the center of this range are most common under conditions of moderate magnetic disturbance. Roughly near 18(h) magnetic local time, a latitudinally narrow strip at the transition between auroral belt and polar cap fields exhibits unusually large field fluctuations immediately following the sudden onset of a negative bay at later magnetic local times. It appears likely that this spatially isolated correlation is related to an effect rather than a cause of <span class="hlt">substorm</span> enhancement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780026072','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780026072"><span>Particle acceleration in pulsar <span class="hlt">magnetospheres</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baker, K. B.</p> <p>1978-01-01</p> <p>The structure of pulsar <span class="hlt">magnetospheres</span> and the acceleration mechanism for charged particles in the <span class="hlt">magnetosphere</span> was studied using a pulsar model which required large acceleration of the particles near the surface of the star. A theorem was developed which showed that particle acceleration cannot be expected when the angle between the magnetic field lines and the rotation axis is constant (e.g. radial field lines). If this angle is not constant, however, acceleration must <span class="hlt">occur</span>. The more realistic model of an axisymmetric neutron star with a strong dipole magnetic field aligned with the rotation axis was investigated. In this case, acceleration <span class="hlt">occurred</span> at large distances from the surface of the star. The magnitude of the current can be determined using the model presented. In the case of nonaxisymmetric systems, the acceleration is expected to <span class="hlt">occur</span> nearer to the surface of the star.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120002020','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120002020"><span>Dynamic Agents of <span class="hlt">Magnetosphere</span>-Ionosphere Coupling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Khazanov, George V.; Rowland, Douglas E.; Moore, Thomas E.; Collier, Michael</p> <p>2011-01-01</p> <p>VISIONS sounding rocket mission (VISualizing Ion Outflow via Neutral atom imaging during a <span class="hlt">Substorm</span>) has been awarded to NASA/GSFC (PI Rowland) in order to provide the first combined remote sensing and in situ measurements of the regions where ion acceleration to above 5 e V is <span class="hlt">occurring</span>, and of the sources of free energy and acceleration mechanisms that accelerate the ions. The key science question of VISIONS is how, when, and where, are ions accelerated to escape velocities in the auroral zone below 1000 km, following <span class="hlt">substorm</span> onset? Sources of free energy that power this ion acceleration process include (but not limited) electron precipitation, field-aligned currents, velocity shears, and Alfvenic Poynting flux. The combine effect of all these processes on ionospheric ion outflows will be investigated in a framework of the kinetic model that has been developed by Khazanov et al. in order to study the polar wind transport in the presence of photoelectrons.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM14A..02F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM14A..02F"><span>Modeling the Inner-<span class="hlt">Magnetosphere</span> Ionosphere with the CIMI Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fok, M. C. H.; Buzulukova, N.; Chen, S. H.; Glocer, A.; Nagai, T.; Valek, P. W.; Perez, J. D.</p> <p>2014-12-01</p> <p>We have combined two well developed models, the Comprehensive Ring Current Model (CRCM) and the Radiation Belt Environment (RBE) model to form a Comprehensive Inner-<span class="hlt">Magnetosphere</span> Ionosphere (CIMI) model. CIMI predicts ion and electron fluxes in the radiation belts and ring current, particle density in the plasmasphere, Region 2 current, subauroal electric field and particle precipitation in the ionosphere, and their responses to solar wind condition. CIMI considers important cross-energy interactions in the inner <span class="hlt">magnetosphere</span> and is able to identify the physical processes that are responsible for ring current, radiation belt enhancements and losses, such as, particle injection, adiabatic acceleration, wave-particle interactions and magnetopause shadowing. We demonstrate the capability of CIMI by simulating a magnetic storm on 5-9 April 2010 and a MHD <span class="hlt">substorm</span>. We also illustrate that CIMI is an excellent tool for analyzing and interpreting global energetic neutral atom data from TWINS and the in-situ measurements from the Van Allen Probes mission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080032512','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080032512"><span>New Understanding of Mercury's <span class="hlt">Magnetosphere</span> from MESSENGER'S First Flyby</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slavin, James A.; Acuna, Mario H.; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Gloeckler, George; Gold, Robert E.; Ho, George C.; Killen, M.; Korth, Haje; Krimigis, Stamatios M.; McNutt, Ralph L., Jr.; Raines, James M.; Schriver, David; Somomon, Sean C.; Starr, Richard; Travnicek, Pavel; Zurbuchen, Thomas H.</p> <p>2008-01-01</p> <p>Observations by the MESSENGER spacecraft on 14 January 2008 have revealed new features of the solar system's smallest planetary <span class="hlt">magnetosphere</span>. The interplanetary magnetic field orientation was unfavorable for large inputs of energy from the solar wind and no evidence of magnetic <span class="hlt">substorms</span>, internal magnetic reconnection, or energetic particle acceleration was detected. Large-scale rotations of the magnetic field were measured along the dusk flank of the <span class="hlt">magnetosphere</span> and ultra-tow frequency waves were frequently observed beginning near closest approach. Outbound the spacecraft encountered two current-sheet boundaries across which the magnetic field intensity decreased in a step-like manner. The outer current sheet is the magnetopause boundary. The inner current sheet is similar in structure, but weaker and -1000 km closer to the planet. Between these two current sheets the magnetic field intensity is depressed by the diamagnetic effect of planetary ions created by the photo-ionization of Mercury's exosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010033905&hterms=current+events&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcurrent%2Bevents','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010033905&hterms=current+events&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcurrent%2Bevents"><span>Freja Studies of the Current-Voltage Relation in <span class="hlt">Substorm</span>-Related Events</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Olsson, A.; Andersson, Laila; Eriksson, A. I.; Clemmons, J.; Erlandsson, R. E.; Reeves, G.; Hughes, T.; Murphee, J. S.</p> <p>2000-01-01</p> <p>Field-aligned currents and electrostatic potentials play important roles in the coupling between the <span class="hlt">magnetosphere</span> and the ionosphere. If one assumes that the ionosphere-<span class="hlt">magnetosphere</span> potential difference is mainly due to the mirror force, one can use the single particle adiabatic kinetic theory to describe the system. From this theory, a linear relationship j(sub II) = KV between field-aligned current density j(sub II) and potential drop V along the same field line can be derived, provided that the potential drop is not too large and not too small. With rare exceptions, observational tests of this relation have mainly concentrated on quiet <span class="hlt">magnetospheric</span> situations, with acceleration voltages V approx. less than 5 kV. Here we use observations from the Freja satellite of precipitating auroral electrons at 1.700 km altitude to study <span class="hlt">substorm</span> related events, with acceleration voltages up to 20 keV. The observations are found to be consistent with a linear current-voltage relation even i n these conditions, although with values of the field aligned K lower than previously reported (1-5 x 10(exp 11 S/sq m). This can be explained by lower densities and higher characteristic electron energies in the <span class="hlt">magnetospheric</span> source region of the precipitating electrons. We analyze the data by three different methods, which are all found to be in general agreement. The results are in agreement with a previous study, where the spectra of precipitating electrons --were indirectly inferred by inversion of data from the EISCAT incoherent scatter radar, thereby validating the use of radar data for studies of auroral electrons. Comparisons with previous studies are made, emphasizing the dependence of the results on the type of auroral structure and <span class="hlt">magnetospheric</span> conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920041911&hterms=central+heating&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcentral%2Bheating','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920041911&hterms=central+heating&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcentral%2Bheating"><span>Nonadiabatic heating of the central plasma sheet at <span class="hlt">substorm</span> onset</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huang, C. Y.; Frank, L. A.; Rostoker, G.; Fennell, J.; Mitchell, D. G.</p> <p>1992-01-01</p> <p>Heating events in the plasma sheet boundary layer and central plasma sheet are found to <span class="hlt">occur</span> at the onset of expansive phase activity. The main effect is a dramatic increase in plasma temperature, coincident with a partial dipolarization of the magnetic field. Fluxes of energetic particles increase without dispersion during these events which <span class="hlt">occur</span> at all radial distances up to 23 RE, the apogee of the ISEE spacecraft. A major difference between these heating events and those observed at geosynchronous distances lies in the heating mechanism which is nonadiabatic beyond 10 RE but may be adiabatic closer to earth. The energy required to account for the increase in plasma thermal energy is comparable with that required for Joule heating of the ionosphere. The plasma sheet must be considered as a major sink in the energy balance of a <span class="hlt">substorm</span>. Lobe magnetic pressures during these events are estimated. Change in lobe pressure are generally not correlated with onsets or intensifications of expansive phase activity.</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('http://adsabs.harvard.edu/abs/2014AGUFMSM12A..03P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM12A..03P"><span><span class="hlt">Substorm</span> Onset and the Possible Role of O+ IONS Flowing out during Pseudo-Breakup Auroras</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parks, G. K.; Lee, E.; Fillingim, M. O.; Fu, S.; Cui, Y.; Hong, J.</p> <p>2014-12-01</p> <p>An isolated <span class="hlt">substorm</span> onset event that <span class="hlt">occurred</span> on 14 February 2001 was recorded by the WIC on IMAGE. WIC observed an enhanced electron precipitation region that grew out of a pseudo-breakup auroral spot at the poleward boundary that moved southward and activitated an aurora. An isolated <span class="hlt">substorm</span> onset was triggered when the pseudo-breakup region connected to the activitated aurora at the lower boundary. This observation is a global scale phenomenon, whose behavior is similar but also different from observations of north-south motion at smaller localized scales that precede the onset of <span class="hlt">substorms</span> (Nishimura et al., 2010). Fortuitously, Cluster during this pseudo-break auroral activity, detected escape of low energy (20-50 eV) field-aligned O+ ions. The triggered onset was accompanied by the escape of more energetic O+ (80 eV -300 eV) ions. Our observations suggest that the escaping O+ ions during pseudo-breakup auroras may be the seed for the onset of isolated <span class="hlt">substorms</span> needed in some simulation models (Winglee and Harnett, 2010).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850051334&hterms=technologie&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtechnologie','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850051334&hterms=technologie&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtechnologie"><span>Correlated observations of <span class="hlt">substorm</span> effects in the near-earth region and the deep magnetotail</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scholer, M.; Baumjohann, W.; Baker, D. N.; Bame, S. J.; Gloeckler, G.; Ipavich, F. M.; Smith, E. J.; Tsurutani, B. T.</p> <p>1985-01-01</p> <p>Simultaneous observations of energetic particle measurements from the geosynchronous satellite 1982-019 and magnetic field, electron plasma, and energetic proton and electron measurements obtained with ISEE 3 in the deep tail are presented. The data are supplemented by ground magnetograms. A <span class="hlt">substorm</span> <span class="hlt">occurred</span> on March 22, 1983, close to 0300 UT as identified in the ground magnetograms and by a particle injection at geosynchronous orbit. About 10 min later, ISEE 3 observed (at a distance of approximately 130 RE in the deep tail) magnetic field, plasma, and energetic particle signatures consistent with the passage of a plasmoid. After the passage of the plasmoid the satellite enters shortly into a lobelike environment, in which an energetic proton beam is observed. High-resolution magnetic field data are indicative of small-scale structures in the postplasmoid plasma sheet. From the plasma sheet flow speed during the plasmoid's passage it is concluded that the 0300 UT <span class="hlt">substorm</span> is responsible for its origin. This allows an approximate timing of the plasmoid release at a near-earth neutral line and of the plasma sheet recovery after <span class="hlt">substorm</span> onset, and it indicates a close relationship between processes in the near-earth plasma sheet and the deep tail during <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GMS...216...99R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GMS...216...99R"><span>ULF Waves above the Nightside Auroral Oval during <span class="hlt">Substorm</span> Onset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rae, I. J.; Watt, C. E. J.</p> <p>2016-02-01</p> <p>This chapter reviews historical ground-based observations of ultra-low-frequency (ULF) waves tied to <span class="hlt">substorms</span>, and highlights new research linking these ULF waves explicitly to <span class="hlt">substorm</span> onset itself. There are several robust methods that can be used to determine the characteristics of a nonstationary time series such as the ULF magnetic field traces observed in the auroral zone during <span class="hlt">substorms</span>. These include the pure state filter, the Hilbert-Huang transform, and wavelet analysis. The first indication of a <span class="hlt">substorm</span> is a sudden brightening of one of the quiet arcs lying in the midnight sector of the oval. The chapter focuses on the properties of ULF waves that are seen in two-dimensional images of auroral intensity near <span class="hlt">substorm</span> expansion phase onset. It also discusses a wider range of magnetotail instabilities that could be responsible for the azimuthally structured auroral forms at <span class="hlt">substorm</span> onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-GSFC_20170927_Archive_e001126.png.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-GSFC_20170927_Archive_e001126.png.html"><span><span class="hlt">Magnetospheric</span> Multiscale (MMS)</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2017-09-27</p> <p>Propulsion engineer measures the flight filters during the receiving inspection. Learn more about MMS at www.nasa.gov/mms Credit NASA/Goddard The <span class="hlt">Magnetospheric</span> Multiscale, or MMS, will study how the sun and the Earth's magnetic fields connect and disconnect, an explosive process that can accelerate particles through space to nearly the speed of light. This process is called magnetic reconnection and can <span class="hlt">occur</span> throughout all space. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.2991L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.2991L"><span><span class="hlt">Magnetospheric</span> balance of solar wind dynamic pressure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lopez, Ramon E.; Gonzalez, Walter D.</p> <p>2017-04-01</p> <p>The magnetopause is the boundary established by pressure balance between the solar wind flow in the magnetosheath and the <span class="hlt">magnetosphere</span>. Generally, this pressure balance is represented to be between the solar wind, the dynamic pressure, and the magnetic pressure of Earth's dipole field. The plasma actually in contact with the <span class="hlt">magnetosphere</span> is the slowed, compressed, and heated solar wind downstream of the shock. The force exerted on the magnetosheath plasma is the J × B force produced by the Chapman-Ferraro current that flows on the magnetopause. Under typical solar wind conditions of relatively high magnetosonic Mach number flow (>6), this simple picture is a reasonable description of the situation. However, under conditions of low solar wind magnetosonic Mach number flow ( 2) the force on the solar wind plasma is not exerted at the magnetopause and must be exerted at the bow shock by currents that connect to the Region 1 currents. In this paper we present observations from two magnetopause crossings observed by the Time History of Events and Macroscale Interactions during <span class="hlt">Substorms</span> spacecraft to compare and contrast the force balance with the solar wind for two situations with very different solar wind magnetosonic Mach numbers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRA..120.5393L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRA..120.5393L"><span>The enhancement of cosmic radio noise absorption due to hiss-driven energetic electron precipitation during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Haimeng; Yuan, Zhigang; Yu, Xiongdong; Huang, Shiyong; Wang, Dedong; Wang, Zhenzhen; Qiao, Zheng; Wygant, John R.</p> <p>2015-07-01</p> <p>The Van Allen probes, low-altitude NOAA satellite, MetOp satellite, and riometer are used to analyze variations of precipitating energetic electron fluxes and cosmic radio noise absorption (CNA) driven by plasmaspheric hiss with respect to geomagnetic activities. The hiss-driven energetic electron precipitations (at L ~ 4.7-5.3, magnetic local time (MLT) ~ 8-9) are observed during geomagnetic quiet condition and <span class="hlt">substorms</span>, respectively. We find that the CNA detected by riometers increased very little in the hiss-driven event during quiet condition on 6 September 2012. The hiss-driven enhancement of riometer was still little during the first <span class="hlt">substorm</span> on 30 September 2012. However, the absorption detected by the riometer largely increased, while the energies of the injected electrons became higher during the second <span class="hlt">substorm</span> on 30 September 2012. The enhancement of CNA (ΔCNA) observed by the riometer and calculated with precipitating energetic electrons is in agreement during the second <span class="hlt">substorm</span>, implying that the precipitating energetic electrons increase CNA to an obviously detectable level of the riometer during the second <span class="hlt">substorm</span> on 30 September 2012. The conclusion is consistent with Rodger et al. (2012), which suggest that the higher level of ΔCNA prefers to <span class="hlt">occur</span> in the <span class="hlt">substorms</span>, because <span class="hlt">substorms</span> may produce more intense energetic electron precipitation associated with electron injection. Furthermore, the combination of the observations and theory calculations also suggests that higher-energy electron (>55 keV) precipitation contributes more to the ΔCNA than the lower energy electron precipitation. In this paper, the higher-energy electron precipitation is related to lower frequency hiss.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830065821&hterms=streaming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstreaming','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830065821&hterms=streaming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dstreaming"><span>Observations of ion streaming during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lui, A. T. Y.; Williams, D. J.; Eastman, T. E.; Frank, L. A.</p> <p>1983-01-01</p> <p>The ion beam phenomenon at the plasma sheet boundary is examined for individually identifiable <span class="hlt">substorms</span>, and the <span class="hlt">substorm</span>-associated particle phenomena are evaluated in terms of the energy-angle distributions of the plasma population and three-dimensional energetic ion distributions. In all seven cases studied it is found that ion beams streaming earthward and/or tailward are always present at the edge of the plasma sheet adjacent to the tail lobe. Ion beams penetrating into the plasma sheet region with no detectable density gradient are also observed. Beams at tens to hundreds of eV often stream tailward and are often long lasting, suggesting that they may be related to ionospheric sources. Both tailward and earthward streaming beams are detected for ion beams above 1 keV, consistent with an origin from the distant tail, propagation toward earth, and mirroring back under single particle motions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMSM31A0408P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMSM31A0408P"><span>The role of random fluctuations in the <span class="hlt">magnetosphere</span>-ionosphere system: a dynamic stochastic model for AE-index variations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pulkkinen, A.; Klimas, A.; Vassiliadis, D.; Uritsky, V.</p> <p>2005-12-01</p> <p>Understanding the evolution of bursts of activity in the <span class="hlt">magnetosphere</span>-ionosphere system has been one of the central challenges in space physics since, and even prior to the introduction of the term "<span class="hlt">substorm</span>". An extensive amount of work has been put to the characterization of the average near-space plasma environment behavior during <span class="hlt">substorms</span> and several more or less deterministic models have been introduced to explain the observations. However, although most of <span class="hlt">substorms</span> seem to have some common characteristics (otherwise any classification would be completely meaningless), like intensification of auroral electric currents, dipolarization of the magnetotail and injections of plasma sheet charged particles, each <span class="hlt">substorm</span> has its distinct features in terms of strong fluctuations around the average "typical" behavior. This highly complex nature of individual <span class="hlt">substorms</span> suggests that stochastic processes may play a role, even a central one in the evolution of <span class="hlt">substorms</span>. In this work, we develop a simple stochastic model for the AE-index variations to investigate the role of random fluctuations in the <span class="hlt">substorm</span> phenomenon. We show that by the introduction of a stochastic component, we are able to capture some fundamental features of the AE-index variations. More specifically, complex variations associated with individual bursts are a central part of the model. It will be demonstrated that by analyzing the structure of the constructed stochastic model some presently open questions about <span class="hlt">substorm</span>-related bursts of the AE-index can be addressed quantitatively. First and foremost, it will be shown that the stochastic fluctuations are a fundamental part of the AE-index evolution and cannot be neglected even when the average properties of the index are of interest.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870053920&hterms=motion+distance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmotion%2Bdistance','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870053920&hterms=motion+distance&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmotion%2Bdistance"><span>Latitudinal motions of the aurora during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Craven, J. D.; Frank, L. A.</p> <p>1987-01-01</p> <p>Sequences of auroral images obtained with Dynamics Explorer 1 are used to investigate latitudinal motions of the aurora in <span class="hlt">substorms</span>. Average speeds of poleward motion are about 230 m/s near local midnight for two isolated, small <span class="hlt">substorms</span> and about 1000 m/s during an intensification within a previously active auroral oval. The speed of poleward expansion measured at about 6-min temporal resolution can differ greatly from the average speed because of the episodic development of <span class="hlt">substorms</span>. Recovery of the high-latitude boundary of the aurora to presubstorm latitudes is first observed in the postmidnight sector. In the premidnight sector the discrete aurora can become stationary for a period of time or even continue further poleward before a retreat to lower latitudes begins. During the recovery phase, a prominent decrease in luminosities is first observed at intermediate latitudes within the auroral distribution. This region is bounded at higher latitudes by the discrete aurora and at lower latitudes by bright diffuse aurora. Given that magnetic field lines threading these auroral distributions map to the plasma sheet boundary layer and to the central plasma sheet, respectively, magnetic field lines at the intermediate auroral latitudes then map to the plasma sheet at distances of more than about 22 earth radii.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM23C2569M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM23C2569M"><span>On the formation and origin of <span class="hlt">substorm</span> growth phase/onset auroral arcs inferred from conjugate space-ground observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Motoba, T.; Ohtani, S.; Anderson, B. J.; Korth, H.; Mitchell, D. G.; Lanzerotti, L. J.; Shiokawa, K.; Connors, M. G.; Kletzing, C.; Reeves, G. D.</p> <p>2015-12-01</p> <p>Magnetotail processes and structures related to <span class="hlt">substorm</span> growth phase/onset auroral arcs remain poorly understood mostly due to the lack of adequate observations. In this study we make a comparison between ground-based optical measurements of the premidnight growth phase/onset arcs at subauroral latitudes and magnetically conjugate measurements made by the Active <span class="hlt">Magnetosphere</span> and Planetary Electrodynamics Response Experiment (AMPERE) at ~780 km in altitude and by the Van Allen Probe-B spacecraft crossing L values of ~5.0-5.6 in the premidnight inner tail region. The conjugate observations offer a unique opportunity to examine the detailed features of the arc location relative to large-scale Birkeland currents and of the <span class="hlt">magnetospheric</span> counterpart. The observations strongly suggest that the premidnight arc is connected to highly localized pressure gradients embedded in the near-tail R2 source region via a local upward FAC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM22A..05N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM22A..05N"><span><span class="hlt">Substorm</span> auroral onset triggering by flow-wave interaction detected with high-resolution radar and imager measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nishimura, T.; Lyons, L. R.; Zou, Y.; Bristow, W. A.; Hampton, D. L.; Nicolls, M. J.; Michell, R.; Samara, M.; Angelopoulos, V.; Donovan, E.; Spanswick, E.</p> <p>2013-12-01</p> <p>A critical, long-standing problem in <span class="hlt">substorm</span> research is identification of the sequence of events leading to <span class="hlt">substorm</span> auroral onset. THEMIS all-sky imager (ASI) array observations have revealed a repeatable pre-onset sequence that begins with a poleward boundary intensification (PBI) followed by a north-south oriented streamer moving equatorward. <span class="hlt">Substorm</span> auroral onset <span class="hlt">occurs</span> soon after the streamer reaches near the <span class="hlt">substorm</span> onset location. Since fast magnetotail flows are linked to PBIs and streamers, this sequence indicates that onset is preceded by enhanced earthward plasma flows associated with a localized reconnection region near the pre-existing open-closed field line boundary. On the other hand, THEMIS satellite and ASIs also show that <span class="hlt">substorms</span> are preceded by azimuthally propagating waves of ~1-2 min periodicity, indicating that a wave mode within the near-Earth plasma sheet is important for triggering <span class="hlt">substorm</span> onset. However, it has been difficult to identify the link between fast earthward flows and these near-Earth waves. We have found a <span class="hlt">substorm</span> event for which there is excellent coverage from the Poker Flat incoherent scatter radar (PFISR), THEMIS white light and multi-spectral ASIs, where the auroral onset <span class="hlt">occurred</span> within the PFISR field of view near the zenith of the ASIs. The <span class="hlt">substorm</span> onset was preceded by a PBI, and one of the radar beams going through the PBI detected equatorward flows and reaching the growth phase arc. The flows appear to propagate from open magnetic field lines across the open-closed boundary, leading to the PBI and then to onset soon after they reach the near-Earth plasma sheet. We also identified oscillations of auroral luminosity along the growth phase arc with a ~1 min period. These waves were propagating westward with only small intensity variations. Soon after the equatorward flows reached the growth phase arc, the wave luminosity amplified abruptly, denoting the onset of a <span class="hlt">substorm</span>. Based on this sequence, we suggest</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930046817&hterms=3815&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D3815','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930046817&hterms=3815&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D3815"><span>CDAW 9 analysis of <span class="hlt">magnetospheric</span> events on May 3, 1986 - Event C</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baker, D. N.; Pulkkinen, T. I.; Mcpherron, R. L.; Craven, J. D.; Frank, L. A.; Elphinstone, R. D.; Murphree, J. S.; Fennell, J. F.; Lopez, R. E.; Nagai, T.</p> <p>1993-01-01</p> <p>An intense geomagnetic <span class="hlt">substorm</span> event on May 3, 1986, <span class="hlt">occurring</span> toward the end of a strong storm period, is studied. The auroral electrojet indices and global imaging data from both the Northern and Southern Hemispheres clearly revealed the growth phase and expansion phase development for a <span class="hlt">substorm</span> with an onset at 0111 UT. An ideally located constellation of four spacecraft allowed detailed observation of the <span class="hlt">substorm</span> growth phase in the near-tail region. A realistic time-evolving magnetic field model provided a global representation of the field configuration throughout the growth and early expansion phase of the <span class="hlt">substorm</span>. Evidence of a narrowly localized <span class="hlt">substorm</span> onset region in the near-earth tail is found. This region spread rapidly eastward and poleward after the 0111 UT onset. The results are consistent with a model of late growth phase formation of a magnetic neutral line. This reconnection region caused plasma sheet current diversion before the <span class="hlt">substorm</span> onset and eventually led to cross-tail current disruption at the time of the <span class="hlt">substorm</span> onset.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.youtube.com/watch?v=TN0sPyQQQbA','SCIGOVIMAGE-NASA'); return false;" href="http://www.youtube.com/watch?v=TN0sPyQQQbA"><span><span class="hlt">Magnetospheric</span> Multiscale (MMS) Orbit</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p></p> <p>This animation shows the orbits of <span class="hlt">Magnetospheric</span> Multiscale (MMS) mission, a Solar-Terrestrial Probe mission comprising of four identically instrumented spacecraft that will study the Earth's magn...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880063863&hterms=selesnick&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dselesnick','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880063863&hterms=selesnick&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dselesnick"><span><span class="hlt">Magnetospheric</span> convection at Uranus</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Selesnick, R. S.</p> <p>1987-01-01</p> <p>The unusual configuration of the Uranian <span class="hlt">magnetosphere</span> leads to differences in the relative effects of solar wind induced <span class="hlt">magnetospheric</span> convection and plasma corotation from those at the other planets. At the present epoch the orientation of the rotation axis of Uranus with respect to the solar wind flow direction leads to a decoupling of the convective and corotational flows, allowing plasma from the tail to move unimpeded through the inner <span class="hlt">magnetosphere</span>. As Uranus progresses in its orbit around the sun, corotation plays a gradually more important role and the plasma residence times within the <span class="hlt">magnetosphere</span> increase. When the rotation axis finally becomes perpendicular to the solar wind flow, corotation is dominant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SSRv..tmp..107E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SSRv..tmp..107E"><span>The Scientific Foundations of Forecasting <span class="hlt">Magnetospheric</span> Space Weather</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eastwood, J. P.; Nakamura, R.; Turc, L.; Mejnertsen, L.; Hesse, M.</p> <p>2017-08-01</p> <p>The <span class="hlt">magnetosphere</span> is the lens through which solar space weather phenomena are focused and directed towards the Earth. In particular, the non-linear interaction of the solar wind with the Earth's magnetic field leads to the formation of highly inhomogenous electrical currents in the ionosphere which can ultimately result in damage to and problems with the operation of power distribution networks. Since electric power is the fundamental cornerstone of modern life, the interruption of power is the primary pathway by which space weather has impact on human activity and technology. Consequently, in the context of space weather, it is the ability to predict geomagnetic activity that is of key importance. This is usually stated in terms of geomagnetic storms, but we argue that in fact it is the <span class="hlt">substorm</span> phenomenon which contains the crucial physics, and therefore prediction of <span class="hlt">substorm</span> occurrence, severity and duration, either within the context of a longer-lasting geomagnetic storm, but potentially also as an isolated event, is of critical importance. Here we review the physics of the <span class="hlt">magnetosphere</span> in the frame of space weather forecasting, focusing on recent results, current understanding, and an assessment of probable future developments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......121P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......121P"><span>Simulations of Dynamic Relativistic <span class="hlt">Magnetospheres</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parfrey, Kyle Patrick</p> <p></p> <p>Neutron stars and black holes are generally surrounded by <span class="hlt">magnetospheres</span> of highly conducting plasma in which the magnetic flux density is so high that hydrodynamic forces are irrelevant. In this vanishing-inertia—or ultra-relativistic—limit, magnetohydrodynamics becomes force-free electrodynamics, a system of equations comprising only the magnetic and electric fields, and in which the plasma response is effected by a nonlinear current density term. In this dissertation I describe a new pseudospectral simulation code, designed for studying the dynamic <span class="hlt">magnetospheres</span> of compact objects. A detailed description of the code and several numerical test problems are given. I first apply the code to the aligned rotator problem, in which a star with a dipole magnetic field is set rotating about its magnetic axis. The solution evolves to a steady state, which is nearly ideal and dissipationless everywhere except in a current sheet, or magnetic field discontinuity, at the equator, into which electromagnetic energy flows and is dissipated. Magnetars are believed to have twisted <span class="hlt">magnetospheres</span>, due to internal magnetic evolution which deforms the crust, dragging the footpoints of external magnetic field lines. This twisting may be able to explain both magnetars' persistent hard X-ray emission and their energetic bursts and flares. Using the new code, I simulate the evolution of relativistic <span class="hlt">magnetospheres</span> subjected to slow twisting through large angles. The field lines expand outward, forming a strong current layer; eventually the configuration loses equilibrium and a dynamic rearrangement <span class="hlt">occurs</span>, involving large-scale rapid magnetic reconnection and dissipation of the free energy of the twisted magnetic field. When the star is rotating, the <span class="hlt">magnetospheric</span> twisting leads to a large increase in the stellar spin-down rate, which may take place on the long twisting timescale or in brief explosive events, depending on where the twisting is applied and the history of the system</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950011879&hterms=john+pedersen&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Djohn%2Bpedersen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950011879&hterms=john+pedersen&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Djohn%2Bpedersen"><span><span class="hlt">Magnetospheric</span> electric fields and auroral oval</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Laakso, Harri; Pedersen, Arne; Craven, John D.; Frank, L. A.</p> <p>1992-01-01</p> <p>DC electric field variations in a synchronous orbit (GEOS 2) during four <span class="hlt">substorms</span> in the time sector 19 to 01 LT were investigated. Simultaneously, the imaging photometer on board DE 1 provided auroral images that are also utilized. <span class="hlt">Substorm</span> onset is defined here as a sudden appearance of large electric fields. During the growth phase, the orientation of the electric field begins to oscillate some 30 min prior to onset. About 10 min before the onset GEOS 2 starts moving into a more tenuous plasma, probably due to a thinning of the current sheet. The onset is followed by a period of 10 to 15 min during which large electric fields <span class="hlt">occur</span>. This interval can be divided into two intervals. During the first interval, which lasts 4 to 8 min, very large fields of 8 to 20 mV/m are observed, while the second interval contains relatively large fields (2 to 5 mV/m). A few min after the onset, the spacecraft returns to a plasma region of higher electron fluxes which are usually larger than before <span class="hlt">substorm</span>. Some 30 min after onset, enhanced activity, lasting about 10 min, appears in the electric field. One of the events selected offers a good opportunity to study the formation and development of the Westward Traveling Surge (WST). During the traversal of the leading edge of the WTS (approximately 8 min) a stable wave mode at 5.7 mHz is detected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSM22A..03D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSM22A..03D"><span>Investigation of solar wind and <span class="hlt">magnetospheric</span> forcing effects on the outer Van Allen belt through multi-point measurements in the inner <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Daglis, I. A.; Katsavrias, C.; Georgiou, M.; Turner, D. L.; Sandberg, I.; Balasis, G.; Papadimitriou, K.</p> <p>2014-12-01</p> <p>We have investigated the response of the outer Van Allen belt electrons to various types of solar wind and internal <span class="hlt">magnetospheric</span> forcing - in particular to Interplanetary Coronal Mass Ejections (ICMEs), to geospace magnetic storms of different intensities and to intense <span class="hlt">magnetospheric</span> <span class="hlt">substorms</span>. We have employed multi-point particle and field observations in the inner <span class="hlt">magnetosphere</span> (both in-situ and through ground-based remote sensing), including the Cluster, THEMIS, Van Allen Probes and GOES constellations, the XMM and INTEGRAL spacecraft, and the CARISMA and IMAGE ground magnetometer arrays. The data provide a broad range of particle energies and a wide radial and azimuthal spatial coverage. This work has received support from the European Union's Seventh Framework Programme (FP7-SPACE-2011-1) under grant agreement no. 284520 for the MAARBLE (Monitoring, Analysing and Assessing Radiation Belt Energization and Loss) collaborative research project.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Ap%26SS.362..101M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Ap%26SS.362..101M"><span>Energy budget during an isolated <span class="hlt">substorm</span> using measurements of multi satellites and geomagnetic indices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ma, Yuduan; Yang, Jian; Dunlop, M. W.; An, An</p> <p>2017-05-01</p> <p>Measurements of multi satellites and geomagnetic indices are used to investigate the energy budget during an isolated <span class="hlt">substorm</span>. The calculation of the energy transfer from the solar wind to the <span class="hlt">magnetosphere</span> (parameter ɛ), the energy increase of the ring current (U_{{R}}), the Joule heating (U_{{J}}), the particle precipitation energy flux (U_{{A}}) and their time-integrated energy dissipation {W}_{ɛ}, {W}_{{R}}, {W}_{{J}}, {W}_{{A}} indicates that there should be energy dissipation such as plasma heating and the energy returned to the solar wind by plasmoid ejection from the tail. After calculating the spatial sizes of nine selected BBFs, the energy flux density and energy transported Earthward or tailward by BBFs, using observations from three satellites, are found to be different during an isolated <span class="hlt">substorm</span>. The flow thermal energy is dominant whether the energy is transported Earthward or tailward under the frozen-in condition in the inner plasma sheet. From results simultaneously observed by three satellites in the magnetotail, we find that the Earthward energy transported by the flows can provide the energy dissipation of {W}_{{J}} and {W}_{{A}}, where the flows are Earthward for more than 60% of the samples, while the tailward energy transport is far larger than {U}_{{A}} and close to {U}_{{J}}, where the flows are tailward for less than 40% of the samples. The maximum energy flux density is observed by one satellite to be accompanied by large variations, while the maximum energy transport is observed by another satellite with large energy flux density and small variations. This suggests misleading conclusions would be obtained if there were only data from single (or two) satellites. From our results, BBFs play an important role in the process of energy transport both Earthward and tailward during this isolated <span class="hlt">substorm</span>. Data based on observations from one satellite in the magnetotail could be easily misinterpreted and should be used cautiously.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM41E2537N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM41E2537N"><span>Generation mechanism of L-value dependence of oxygen flux enhancements during <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.</p> <p>2015-12-01</p> <p>The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures charged particles with an energy range from ~eV to ~ tens of keV. The observation shows that the energy flux of the particles increases inside the geosynchronous orbit during <span class="hlt">substorms</span>. For some night-side events around the apogee, the energy flux of O+ ion enhances below ~10 keV at lower L shell, whereas the flux below ~8 keV sharply decreases at higher L shells. This structure of L-energy spectrogram of flux is observed only for the O+ ions. The purpose of this study is to investigate the generation mechanism of the structure by using numerical simulations. We utilized the global MHD simulation developed by Tanaka et al (2010, JGR) to simulate the electric and magnetic fields during <span class="hlt">substorms</span>. We performed test particle simulation under the electric and magnetic fields by applying the same model introduced by Nakayama et al. (2015, JGR). In the test particle simulation each test particle carries the real number of particles in accordance with the Liouville theorem. Using the real number of particles, we reconstructed 6-dimensional phase space density and differential flux of O+ ions in the inner <span class="hlt">magnetosphere</span>. We obtained the following results. (1) Just after the <span class="hlt">substorm</span> onset, the dawn-to-dusk electric field is enhanced to ~ 20 mV/m in the night side tail region at L > 7. (2) The O+ ions are accelerated and transported to the inner region (L > ~5.5) by the large-amplitude electric field. (3) The reconstructed L-energy spectrogram shows a similar structure to the Van Allen Probes observation. (4) The difference in the flux enhancement between at lower L shell and higher L shells is due to two distinct acceleration processes: adiabatic and non-adiabatic. We will discuss the relationship between the particle acceleration and the structure of L-energy spectrogram of flux enhancement in detail.</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://ntrs.nasa.gov/search.jsp?R=19720049294&hterms=Sirens&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DSirens','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720049294&hterms=Sirens&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DSirens"><span><span class="hlt">Magnetospheric</span> electric fields deduced from drifting whistler paths.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carpenter, D. L.; Stone, K.; Siren, J. C.; Crystal, T. L.</p> <p>1972-01-01</p> <p>Results of a study in which the amplitude of the E-W component E sub w of the convection electric field in the nightside <span class="hlt">magnetosphere</span> has been inferred from the observed cross-L motions of whistler ducts within the plasmasphere, and several ducts distributed over 1 to 2 earth radii in L space and over plus or minus deg 15 around the longitude of the Eights, Antarctica, whistler station have been tracked simultaneously. The method appears capable of resolving fluctuations in E sub w with period T equal to approximately 15 min and rms amplitude as low as 0.05 mV/m. For variations with T greater than 1 hour the method has a sensitivity of the order of 0.01 mV/m. Three case studies are presented, two of which illustrate convection activity associated with relatively isolated <span class="hlt">substorms</span>. In these two cases E sub w reversed from westward to eastward for a period following the decay of <span class="hlt">substorm</span> bay activity. In the third case the <span class="hlt">substorm</span> bay activity was prolonged, and E sub w remained westward and at enhanced levels until local dawn. Evidence was found that, at least in a limited longitudinal sector, perturbing <span class="hlt">substorm</span> E sub w fields can penetrate deep within the plasmasphere. In two of the case studies comparisons of E sub w and the interplanetary magnetic-field theta component show evidence of a possible relation based on brief (less than or equal to 1 hour) southward excursions but not on long preceding southward events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..12110623M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..12110623M"><span>Observing the <span class="hlt">magnetosphere</span> through global auroral imaging: 1. Observables</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mende, Stephen B.</p> <p>2016-10-01</p> <p>Over the years, it has become clear that there are fundamental limitations in observing <span class="hlt">magnetospheric</span> processes through their auroral footprints. Most electron auroras are formed in the auroral acceleration region relatively close to the Earth at altitudes (<2 RE). There are four distinct auroral types: (1) downward field-aligned current (FAC) regions where ion precipitation is dominant, (2) pitch angle diffusion aurora (or briefly "diffusion aurora") region without significant FAC, (3) upward FAC regions of precipitating electrons and monoenergetic auroral arc formations, and (4) Alfvénic auroral regions, where low-energy electrons from the ionosphere are accelerated by incoming Alfvén waves. Alfvénic auroras are the footprints of <span class="hlt">magnetospheric</span> regions where waves are produced by dynamic events such as reconnection, <span class="hlt">substorm</span> onset initiation, and magnetic field dipolarization. Based on the mean energy and density of the precipitating electrons, ground-based and spacecraft-based optical observations can be used to distinguish between auroras where the source is the plasma sheet (types 1, 2, and 3) and Alfvénic auroras, where the source is the ionosphere (type 4). Imaging of the Alfvénic auroral region could be used to map the dynamically active regions of the <span class="hlt">magnetosphere</span>. The energy distribution of the most significant precipitating ions, protons, can be measured from the Doppler profile of the hydrogen emission lines. Mapping of the time dependent global energy distribution of proton precipitation would allow the observation of the associated <span class="hlt">magnetospheric</span> boundaries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100014874&hterms=Messenger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DMessenger','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100014874&hterms=Messenger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DMessenger"><span>MESSENGER Observations of Extreme Magnetic Tail Loading and Unloading During its Third Flyby of Mercury: <span class="hlt">Substorms</span>?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Slavin, James A.; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Gloeckler, George; Krimigis, Stamatios M.; McNutt, Ralph L., Jr.; Schriver, David; Solomon, Sean C.; Zurbuchen, Thomas H.</p> <p>2010-01-01</p> <p>During MESSENGER's third flyby of Mercury on September 29, 2009, a variable interplanetary magnetic field produced a series of several minute enhancements of the tail magnetic field hy factors of approx. 2 to 3.5. The magnetic field flaring during these intervals indicates that they result from loading of the tail with magnetic flux transferred from the dayside <span class="hlt">magnetosphere</span>. The unloading intervals were associated with plasmoids and traveling compression regions, signatures of tail reconnection. The peak tail magnetic flux during the smallest loading events equaled 30% of the magnetic flux emanating from Mercury, and may have reached 100% for the largest event. In this case the dayside magnetic shielding is reduced and solar wind flux impacting the surface may be greatly enhanced. Despite the intensity of these events and their similarity to terrestrial <span class="hlt">substorm</span> magnetic flux dynamics, no energetic charged particles with energies greater than 36 keV were observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/296780','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/296780"><span><span class="hlt">Substorm</span> effects in MHD and test particle simulations of magnetotail dynamics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Birn, J.; Hesse, M.</p> <p>1998-12-31</p> <p>Recent magnetohydrodynamic simulations demonstrate that a global tail instability, initiated by localized breakdown of MHD, can cause plasmoid formation and ejection as well as dipolarization and the current diversion of the <span class="hlt">substorm</span> current wedge. The connection between the reconnection process and the current wedge signatures is provided by earthward flow from the reconnection site. Its braking and diversion in the inner <span class="hlt">magnetosphere</span> causes dipolarization and the magnetic field distortions of the current wedge. The authors demonstrate the characteristic properties of this process and the current systems involved. The strong localized electric field associated with the flow burst and the dipolarization is also the cause of particle acceleration and energetic particle injections. Test particle simulations of orbits in the MHD fields yield results that are quite consistent with observed injection signatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRA..118..774P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRA..118..774P"><span>Observations of polar cap flow channel and plasma sheet flow bursts during <span class="hlt">substorm</span> expansion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>PitkäNen, T.; Aikio, A. T.; Juusola, L.</p> <p>2013-02-01</p> <p>We present the first simultaneous observations of an enhanced polar cap flow impinging on the nightside polar cap boundary (PCB), two flow bursts in the plasma sheet and a conjugate ionospheric flow burst within the auroral oval. The ionospheric measurements on 3 September 2006 were made by the European Incoherent Scatter (EISCAT) radars and the <span class="hlt">magnetospheric</span> measurements by the four Cluster spacecraft. In the end of a <span class="hlt">substorm</span> growth phase, EISCAT measured a channel of enhanced equatorward plasma flow within the polar cap, which was about 1° wide in latitude and drifted slowly equatorward. During the <span class="hlt">substorm</span> expansion phase, the PCB started to contract poleward. The interaction between the equatorward drifting polar cap flow channel and the poleward contracting PCB took 2-3 min. During this time, the F-region electron temperature was elevated at the PCB, which is interpreted as a possible signature of an auroral poleward boundary intensification (PBI). After that, enhanced equatorward flows were measured inside the auroral oval by EISCAT. During this period, the Cluster satellites measured two fast earthward flow bursts in the plasma sheet, which were associated with dipolarizations of the magnetic field, depletions in plasma density, and return flows. We suggest that the second flow burst in the plasma sheet represents the same flow burst that is seen in the ionosphere by EISCAT and propose that the plasma sheet flow bursts were triggered by the enhanced flow structure on open polar cap field lines. The suggestion is in line with Lyons et al. (2011).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/813623','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/813623"><span>Near-earth Thin Current Sheets and Birkeland Currents during <span class="hlt">Substorm</span> Growth Phase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sorin Zaharia; C.Z. Cheng</p> <p>2003-04-30</p> <p>Two important phenomena observed during the <span class="hlt">magnetospheric</span> <span class="hlt">substorm</span> growth phase are modeled: the formation of a near-Earth (|X| {approx} 9 R{sub E}) thin cross-tail current sheet, as well as the equatorward shift of the ionospheric Birkeland currents. Our study is performed by solving the 3-D force-balance equation with realistic boundary conditions and pressure distributions. The results show a cross-tail current sheet with large current (J{sub {phi}} {approx} 10 nA/m{sup 2}) and very high plasma {beta} ({beta} {approx} 40) between 7 and 10 R{sub E}. The obtained region-1 and region-2 Birkeland currents, formed on closed field lines due to pressure gradients, move equatorward and become more intense (J{sub {parallel}max} {approx} 3 {micro}A/m{sup 2}) compared to quiet times. Both results are in agreement with <span class="hlt">substorm</span> growth phase observations. Our results also predict that the cross-tail current sheet maps into the ionosphere in the transition region between the region-1 and region-2 currents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27.1138D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27.1138D"><span>Poleward Boundary of Auroral Bulge and Plasma Sheet Flow Reversal Region Location During <span class="hlt">Substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Despirak, I. V.; Yahnin, A. G.</p> <p></p> <p>Data from the Geotail spacecraft situated in the night side plasma sheet during 1996- 1997 were used to select events of the tailward-to-Earthward fast plasma flow rever- sals. Then a subset was extracted including those events when UV auroral images were available from the Polar satellite. The Polar data supported by ground-based ob- servations showed that the auroral <span class="hlt">substorms</span> were in progress during the flow reversal events. For every moment of the flow reversal observations we determined the au- roral bulge poleward boundary latitude at the meridian of the Geotail footprint and compared this latitude with the Geotail location in the <span class="hlt">magnetosphere</span>. We found that within the range of 10-30 RE the auroral bulge latitude increases proportionally to the reversal region distance from the Earth. Moreover, tailward (Earthward) flows have a tendency to be observed when Geotail footprint is poleward (equatorward) of the poleward edge of bright auroras. This agrees with the idea that reconnection is the source of discrete auroras during <span class="hlt">substorms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMSM52A..07O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMSM52A..07O"><span>CURRENT SHEET THINNING AND ENTROPY CONSTRAINTS DURING THE <span class="hlt">SUBSTORM</span> GROWTH PHASE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Otto, A.; Hall, F., IV</p> <p>2009-12-01</p> <p>A typical property during the growth phase of geomagnetic <span class="hlt">substorms</span> is the thinning of the near-Earth current sheet, most pronounced in the region between 6 and 15 R_E. We propose that the cause for the current sheet thinning is convection from the midnight tail region to the dayside to replenish <span class="hlt">magnetospheric</span> magnetic flux which is eroded at the dayside as a result of dayside reconnection. Adiabatic convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of the magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. It is proposed that the magnetic flux depletion in the near-Earth tail forces the formation of thin current layers. The process is documented by three-dimensional MHD simulations. It is shown that the simulations yield a time scale, location, and other general characteristics of the current sheet evolution during the <span class="hlt">substorm</span> growth phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMSM11C2314O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMSM11C2314O"><span>Convection Constraints and Current Sheet Thinning During the <span class="hlt">Substorm</span> Growth Phase</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Otto, A.; Hsieh, M.</p> <p>2012-12-01</p> <p>A typical property during the growth phase of geomagnetic <span class="hlt">substorms</span> is the thinning of the near-Earth current sheet, most pronounced in the region between 6 and 15 RE. We propose that the cause for this current sheet thinning is convection from the midnight tail region to the dayside to replenish <span class="hlt">magnetospheric</span> magnetic flux that is eroded at the dayside as a result of dayside reconnection. Slow (adiabatic) convection from the near-Earth tail region toward the dayside must conserve the entropy on magnetic field lines. This constraint prohibits a source of magnetic flux from a region further out in the magnetotail. Thus the near-Earth tail region is increasingly depleted of magnetic flux (the Erickson and Wolf [1980] problem) with entropy matching that of flux tubes that are eroded on the dayside. It is proposed that the magnetic flux depletion in the near-Earth tail forces the formation of thin current layers. The process is illustrated and examined by three-dimensional meso-scale MHD simulations. It is shown that the simulations yield a time scale, location, and other general characteristics of the current sheet evolution consistent with observations during the <span class="hlt">substorm</span> growth phase. The developing thin current sheet is easily destabilized and can undergo localized reconnection events. We present properties of the thinning current sheet, the associated entropy evolution, examples of localized reconnection onset and we discuss the dependence of this process on external parameters such the global reconnection rate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.1749L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.1749L"><span>On the presence and properties of cold ions near Earth's equatorial <span class="hlt">magnetosphere</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Justin H.; Angelopoulos, Vassilis</p> <p>2014-03-01</p> <p>Plasma flows related to <span class="hlt">magnetospheric</span> convection or ULF waves often increase cold ions' kinetic energy sufficiently above the spacecraft potential energy so that these ions can be detected by charged particle instrumentation. Other detection methods also reveal the presence of cold ions even in the absence of flows. By applying such methods to complementary data sets obtained from particle, electric field, and magnetic field measurements by the multiple Time History of Events and Macroscale Interactions during <span class="hlt">Substorms</span> spacecraft, we study the occurrence rates of cold ions and properties—composition, densities, and temperatures—of the dominant species (H+, He+, and O+) near the equatorial <span class="hlt">magnetosphere</span>. As plasma flows <span class="hlt">occur</span> at all magnetic local time (MLT) sectors, predominantly outside the plasmasphere, they enable studies of cold ion occurrence and properties as functions of geocentric distance (up to 13 RE) and MLT. Of the dominant cold ions, protons are most abundant on the dayside and coldest almost everywhere. By comparison, the heavier ions show evidence of larger abundance on the nightside and higher temperatures at most locations: median nHe+/nH+ is ≤0.1 in the afternoon, ≥1.0 on the nightside, and near 0.5 at dawn; median nO+/nH+ exceeds 1 throughout the nightside and around dawn at smaller geocentric distances but varies from 0.0 to 0.1 in the afternoon; and TO+ > THe+ everywhere. By isolating the convective particle drift component of measured ion flows, we deduce that nightside/dawn/prenoon cold ions are components of the warm plasma cloak while cold ions near noon/afternoon are likely of mixed origin, including nightside/cusp outflow, plasmaspheric plumes, and the solar wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM51D2512M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM51D2512M"><span>Relation of field-aligned currents measured by AMPERE project to solar wind and <span class="hlt">substorms</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McPherron, R. L.; Anderson, B. J.; Chu, X.</p> <p>2016-12-01</p> <p>Magnetic perturbations measured in the Active <span class="hlt">Magnetosphere</span> and Planetary Electrodynamics Response Experiment (AMPERE) by the Iridium constellation of spacecraft have been processed to obtain the time history of field-aligned currents (FAC) connecting the <span class="hlt">magnetosphere</span> to the ionosphere. We find that the strength of these currents is closely related to the strength of the solar wind driver defined as a running average of the previous three hours of the optimum AL (auroral lower) coupling function. The relation is well represented by a saturation model I = A*S*Ss/(S+Ss) with I the current strength in mega Amps, S the driver strength in mV/m, Ss the saturation value of 7.78 mV/m, and A = 2.55 scales the relation to units of current. We also find that in general the upward current on the nightside increases with each <span class="hlt">substorm</span> expansion onset defined by a combination of the SuperMag SML (SuperMag AL) and midlatitude positive bay (MPB) onset lists. A superposed epoch analysis using 700 onsets in 2010 shows the following: solar wind coupling peaks at expansion onset; dayside outward current starts to increase one hour before onset while nightside outward current starts suddenly at onset; nightside outward current reaches a peak at 28 minutes as do SML and MPB indices; FAC, SML, and MPB respectively take 1, 2, and 3 hours to decay to background. The data indicate that the <span class="hlt">substorm</span> current wedge is superposed on a pre-existing field-aligned current system and that the location and properties of the current wedge can be studied with the AMPERE data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMSM13D2534P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMSM13D2534P"><span>Role of dayside transients in a <span class="hlt">substorm</span> process: Results from the global kinetic simulation Vlasiator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palmroth, M.; Hoilijoki, S.; Pfau-Kempf, Y.; Hietala, H.; Nishimura, Y.; Angelopoulos, V.; Pulkkinen, T. I.; Ganse, U.; Hannuksela, O.; von Alfthan, S.; Battarbee, M. C.; Vainio, R. O.</p> <p>2015-12-01</p> <p>We investigate the dayside-nightside coupling of the <span class="hlt">magnetospheric</span> dynamics in a global kinetic simulation displaying the entire <span class="hlt">magnetosphere</span>. We use the newly developed Vlasiator (http://vlasiator.fmi.fi), which is the world's first global hybrid-Vlasov simulation modelling the ions as distribution functions, while electrons are treated as a charge-neutralising fluid. Here, we run Vlasiator in the 5-dimensional (5D) setup, where the ordinary space is presented in the 2D noon-midnight meridional plane, embedding in each grid cell the 3D velocity space. This approach combines the improved physical solution with fine resolution, allowing to investigate kinetic processes as a consequence of the global <span class="hlt">magnetospheric</span> evolution. The simulation is during steady southward interplanetary magnetic field. We observe dayside reconnection and the resulting 2D representations of flux transfer events (FTE). FTE's move tailwards and distort the magnetopause, while the largest of them even modify the plasma sheet location. In the nightside, the plasma sheet shows bead-like density enhancements moving slowly earthward. The tailward side of the dipolar field stretches. Strong reconnection initiates first in the near-Earth region, forming a tailward-moving magnetic island that cannibalises other islands forming further down the tail, increasing the island's volume and complexity. After this, several reconnection lines are formed again in the near-Earth region, resulting in several magnetic islands. At first, none of the earthward moving islands reach the closed field region because just tailward of the dipolar region exists a relatively stable X-line, which is strong enough to push most of the magnetic islands tailward. However, finally one of the tailward X-lines is strong enough to overcome the X-line nearest to Earth, forming a strong surge into the dipolar field region as there is nothing anymore to hold back the propagation of the structure. We investigate this <span class="hlt">substorm</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AnGeo..22.4165D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AnGeo..22.4165D"><span>Thinning and expansion of the <span class="hlt">substorm</span> plasma sheet: Cluster PEACE timing analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dewhurst, J.; Owen, C.; Fazakerley, A.; Balogh, A.</p> <p>2004-12-01</p> <p>The storage and subsequent removal of magnetic flux in the magnetotail during a geomagnetic <span class="hlt">substorm</span> has a dramatic effect on the thickness of the cross-tail plasma sheet. The near-Earth plasma sheet is thought to thin during the growth phase and then rapidly expand after onset of the <span class="hlt">substorm</span>. The direction of propagation, whether earthward or tailward along the GSM-X direction in the near-Earth tail, may suggest the time ordering of current-disruption and near-Earth reconnection, both of which are key to the <span class="hlt">substorm</span> process. Cluster's Plasma Electron And Current Experiment (PEACE) allows 4-point observations of electrons at the plasma sheet - lobe boundary as this interface passes over the Cluster tetrahedron. The relative timings of the boundary passage at each spacecraft allow a determination of this boundary's speed and direction of motion, assuming this is planar on the scale of the Cluster separation scale. For those boundaries corresponding to the expansion of the plasma sheet, this direction is fundamental to determining the direction of expansion. We present an example of isolated thinning and expansion of the plasma sheet, as well as a multiple thinning-expansion event that <span class="hlt">occurs</span> during a more active <span class="hlt">substorm</span>. Data from the 2001 and 2002 tail passes have been analysed and the average plasma sheet - lobe boundary normal vectors and normal component velocities have been calculated. A total of 77 crossings, typically between 10 and 20 RE downtail, correspond to <span class="hlt">substorm</span> associated expansion of the plasma sheet over the spacecraft. These had normal vectors predominantly in the GSM-YZ plane and provided no clear evidence for the formation of the near-Earth neutral line <span class="hlt">occurring</span> before current disruption or vice versa. The expansions of the plasma sheet generally exhibit the appropriate GSM-Z direction expected for the given lobe, and tend to have GSM-Y components that support onset <span class="hlt">occurring</span> near the origin of the GSM-YZ plane. This result is noteworthy in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA06345.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA06345.html"><span>Behold Saturn's <span class="hlt">Magnetosphere</span>!</span></a></p> <p><a target="_blank" href="https://images.nasa.gov/">NASA Image and Video Library</a></p> <p></p> <p>2004-07-01</p> <p>Saturn's <span class="hlt">magnetosphere</span> is seen for the first time in this image taken by the Cassini spacecraft on June 21, 2004. A <span class="hlt">magnetosphere</span> is a magnetic envelope of charged particles that surrounds some planets, including Earth. It is invisible to the human eye, but Cassini's <span class="hlt">Magnetospheric</span> Imaging Instrument was able to detect the hydrogen atoms (represented in red) that escape it. The emission from these hydrogen atoms comes primarily from regions far from Saturn, well outside the planet's rings, and perhaps beyond the orbit of the largest moon Titan. The image represents the first direct look at the shape of Saturn's <span class="hlt">magnetosphere</span>. Previously, NASA's Voyager mission had inferred what Saturn's <span class="hlt">magnetosphere</span> would look like in the same way that a blind person might feel the shape of an elephant. With Cassini, the "elephant" has been revealed in a picture. This picture was taken by the ion and neutral camera, one of three sensors that comprise the <span class="hlt">magnetosphereic</span> imaging instrument, from a distance of about 3.7 million miles (about 6 million kilometers) from Saturn. The <span class="hlt">magnetospheric</span> imaging instrument will continue to study Saturn's <span class="hlt">magnetosphere</span> throughout the mission's four-year lifetime. http://photojournal.jpl.nasa.gov/catalog/PIA06345</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800016220&hterms=Acad&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DAcad','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800016220&hterms=Acad&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3DAcad"><span><span class="hlt">Magnetosphere</span>-ionosphere interactions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Vondrak, R. R.; Chiu, Y. T.; Evans, D. S.; Patterson, V. G.; Romick, G. J.; Stasiewicz, K.</p> <p>1979-01-01</p> <p>The present understanding of <span class="hlt">magnetosphere</span> ionosphere interactions is described, and present and future predictive capabilities are assessed. Ionospheric features directly coupled to the <span class="hlt">magnetosphere</span> to a significant degree are considered, with emphasis given to those phenomena of major interest to forecasters and users.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMSM51E2543R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMSM51E2543R"><span>Low Frequency Extensions of the Saturn Kilometric Radiation as a Proxy for <span class="hlt">Magnetospheric</span> Dynamics.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reed, J.; Jackman, C. M.; Whiter, D. K.; Kurth, W. S.; Lamy, L.</p> <p>2016-12-01</p> <p>Saturn Kilometric Radiation (SKR) is a radio emission formed via the cyclotron maser instability on field aligned currents near the auroral regions of Saturn. The SKR has been found to respond to both internal and external driving, and to be linked to both solar wind compressions and magnetotail reconnection events. The radio emission is remotely sensed quasi-continuously and therefore offers the potential to be used as a proxy for <span class="hlt">magnetospheric</span> activity when the spacecraft is not in an ideal viewing region for observing signatures of reconnection. In this work we use data taken by the Cassini magnetometer and radio and plasma wave sensor while Cassini was executing its deepest tail orbits in 2006. We characterise the behaviour of the SKR over this period and develop an automatic method for finding low frequency extensions (LFE), where the SKR emission extends down to lower frequencies below the main band. LFEs have been shown to <span class="hlt">occur</span> in response to reconnection at Saturn (Jackman et al, 2009) and their appearance in Earth's analogous Auroral Kilometric Radiation (AKR) has been shown to coincide with <span class="hlt">substorm</span> onset (e.g. Morioka et al, 2007). Using a new catalogue of LFEs we discuss their correlation with known tail reconnection events and solar wind shocks (as inferred from the use of propagated solar wind models). We also look at their properties such as length and recurrence rate, as well as their relationship to the planetary periodicities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122.1600L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122.1600L"><span>"Zipper-like" periodic magnetosonic waves: Van Allen Probes, THEMIS, and <span class="hlt">magnetospheric</span> multiscale observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, J.; Bortnik, J.; Li, W.; Ma, Q.; Thorne, R. M.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Wygant, J.; Breneman, A.; Thaller, S.; Funsten, H. O.; Mitchell, D. G.; Manweiler, J. W.; Torbert, R. B.; Le Contel, O.; Ergun, R. E.; Lindqvist, P.-A.; Torkar, K.; Nakamura, R.; Andriopoulou, M.; Russell, C. T.</p> <p>2017-02-01</p> <p>An interesting form of "zipper-like" magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra was newly observed by the Van Allen Probes, the Time History of Events and Macroscale Interactions during <span class="hlt">Substorms</span> (THEMIS), and the <span class="hlt">Magnetospheric</span> Multiscale (MMS) missions. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. In one event, the zipper-like magnetosonic waves exhibit the same periodicity as a constant-frequency magnetosonic wave and an electrostatic emission, but the modulation comes from neither density fluctuations nor ULF waves. A statistical survey based on 3.5 years of multisatellite observations shows that zipper-like magnetosonic waves mainly <span class="hlt">occur</span> on the dawnside to noonside, in a frequency range between 10 fcp and fLHR. The zipper-like magnetosonic waves may provide a new clue to nonlinear excitation or modulation process, while its cause still remains to be fully understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006cosp...36.1091S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006cosp...36.1091S"><span>Study of plasma pressure distribution in the inner <span class="hlt">magnetosphere</span> using the low-altitude satellite data as one of important elements of the <span class="hlt">magnetospheric</span> dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stepanova, M.; Antonova, E. E.; Bosqued, J. M.</p> <p></p> <p>Plasma pressure distribution in the inner <span class="hlt">magnetosphere</span> is one of the key parameters for understanding the main <span class="hlt">magnetospheric</span> processes including geomagnetic storms and <span class="hlt">substorms</span> Therefore during the last decades many efforts were concentrated on the study of pressure distribution in the inner <span class="hlt">magnetosphere</span> However the pressure profiles obtained from in-situ particle measurements by the high-altitude satellites inside the plasma sheet and other regions of the <span class="hlt">magnetosphere</span> do not allow the tracking the pressure variations related to the <span class="hlt">magnetospheric</span> dynamics because a time interval neaded to do this generally exceeds the characteristic times of the main <span class="hlt">magnetospheric</span> processes On contrary fast movement of low-altitude satellites makes it possible to catch quasi-instantaneous radial or azimuthal profiles of plasma pressure along the satellite trayectory using the precipitating particle flux data in the regions of isotropic plasma pressure The low-altitude polar-orbiting Aureol-3 satellite was used for this study IGRF Tsyganenko 2001 and Tsyganenko 2004 storm time geomagnetic field models were used for the pressure mapping into the equatorial plane and also to evaluate the corresponding volume of the magnetic flux tube and the magnetic pressure Study of azumuthal plasma pressure gradients showed that these gradients can be a source of the Iijima and Potemra s field-aligned current system Study of radial plasma gradients showed that during quiet geomagnetic condition the profiles obtained coincide with the results obtained previously from the high-altitude</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AdSpR..38.1631S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AdSpR..38.1631S"><span>Study of plasma pressure distribution in the inner <span class="hlt">magnetosphere</span> using low-altitude satellites and its importance for the large-scale <span class="hlt">magnetospheric</span> dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stepanova, M.; Antonova, E. E.; Bosqued, J.-M.</p> <p>2006-01-01</p> <p>Plasma pressure distribution in the inner <span class="hlt">magnetosphere</span> is one of the key parameters for understanding main processes of the <span class="hlt">magnetospheric</span> dynamics including geomagnetic substroms. However, the pressure profiles obtained from in situ measurements by the high-altitude satellites do not allow the tracking of the <span class="hlt">magnetospheric</span> dynamics, because a time necessary to obtain these profiles (hours) generally exceeds the characteristic times of the main <span class="hlt">magnetospheric</span> processes (minutes or less). On contrary, fast movement of low-altitude satellites makes it possible to obtain quasi-instantaneous profiles of plasma pressure along the satellite trajectory - radial or azimuthal, depending on the satellite orbit. Precipitating particle fluxes, measured by the low-altitude Aureol-3 satellite were used. Mapping into the equatorial plane and determination of a volume of the magnetic flux tube were made using the Tsyganenko 96 and 01 geomagnetic field models. Study of radial plasma gradients showed that the inner <span class="hlt">magnetosphere</span> is stable for development of flute (interchange) instability. Modified interchange instability related to azimuthal plasma pressure gradients and field-aligned currents in equilibrium was proposed as a source of <span class="hlt">substorm</span> expansion phase onset. It can develop when the density of the field-aligned current reaches a definite threshold value. The growth rate of the instability is higher in the region of upward field-aligned current, where the existing field-aligned potential drop leads to the <span class="hlt">magnetosphere</span>-ionosphere decoupling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1076B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1076B"><span>The irregular Pi3 geomagnetic pulsations and its connection with the energetic particles in the <span class="hlt">magnetosphere</span> and ionosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Belakhovsky, Vladimir; Pilipenko, Vjacheslav</p> <p>2015-04-01</p> <p>In this study we investigate the nighttime irregular Pi3 type geomagnetic pulsations generated as during strong single <span class="hlt">substorms</span> as during sawtooth events using modern satellite (GOES, THEMIS) and ground-based observations (CARISMA, THEMIS, NORSTAR). These pulsations developed during all <span class="hlt">substorm</span> period but not only during <span class="hlt">substorm</span> growth phase as ordinary Pi2 pulsations. The maximum intensity of these pulsations lies in auroral zone (~66° CGL). It is seen a good correspondence between Pi3 geomagnetic pulsations on the ground-based magnetometers of the CARISMA network and on the GOES geostationary spacecraft, THEMIS spacecrafts which located at ~10 Re in the <span class="hlt">magnetosphere</span> tail. It is seen strong increase of the fluxes of the electrons on GOES, THEMIS spacecrafts, increase of CNA on the NORSTAR riometers, increase of the aurora intensity on the THEMIS all-sky imagers during the beginning of the substrom. The considered irregular Pi3 pulsations strongly modulate the fluxes of the electrons in the <span class="hlt">magnetosphere</span> at GOES, THEMIS spacecrafts and CNA, aurora intensity. But there is no close phase correspondence between the Pi3 pulsations in the geomagnetic field and fluxes of the trapped and precipitated electrons. At the same time there is no simultaneous geomagnetic pulsations in the same frequency rage was observed on the dayside (IMAGE network). We suppose that these Pi3 pulsations have another physical nature than dayside Pc5 pulsations. The Pi3 geomagnetic pulsations may be generated due to proper geomagnetic tail oscillations during <span class="hlt">substorm</span> development.</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('http://adsabs.harvard.edu/abs/2008cosp...37.3660Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008cosp...37.3660Z"><span>Multipoint measurements of <span class="hlt">substorm</span> timing and activations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zuyin, Pu; Cao, X.; Zhang, H.; Ma, Z. W.; Mishin, M. V.; Kubyshkina, M. V.; Pulkkinen, T.; Reeves, G. D.; Escoubet, C. Philippe</p> <p></p> <p><span class="hlt">Substorm</span> timing and activations are studied based on Double Star TC1, Cluster, Polar, IM- AGE, LANL satellites and ground-based Pi2 measurements. <span class="hlt">Substorm</span> expansion onset is found to begin in the near-Earth tail around X= -(8-9) Re, then progresses both earthward and tailward. About 8-10 minutes before aurora breakup, Cluster measured an earthward flow associated with plasma sheet thinning. A couple of minutes after the breakup, TC1 first detects plasma sheet expansion and then LANL satellites near the midnight measure energetic electron injections, or vise versus. About 20 minutes (or more) later, Cluster and Polar observe plasma sheet expansion successively. Of interest are also the following findings. Auroral bulge is found to quickly broaden and expand poleward when the open magnetic flux of the polar cap is rapidly dissipated, indicating the role of tail lobe reconnection of open field lines in the development of the expansion phase. In addition, poleward expansion of auroral bulges and tailward progression of <span class="hlt">substorm</span> expansion are shown to be closely related. An initial dipolarization in the near-Earth eventually evolve to enable disruption of the cross-tail current in a wide range of the magnetotail, until the open magnetic flux of the polar cap reaches its minimum. Acknowledgements This work is supported by the NSFC Grants 40390152 and 40536030 and Chinese Key Research Project Grant 2006CB806300. The authors acknowledge all PIs of instruments onboard Double Star and Cluster spacecraft. We also appreciate the useful discussions with R. L. McPherron and A. T. Y. Lui.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.5213J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.5213J"><span>Multiradar observations of <span class="hlt">substorm</span>-driven ULF waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>James, M. K.; Yeoman, T. K.; Mager, P. N.; Klimushkin, D. Yu.</p> <p>2016-06-01</p> <p>A recent statistical study of ULF waves driven by <span class="hlt">substorm</span>-injected particles observed using Super Dual Auroral Radar Network (SuperDARN) found that the phase characteristics of these waves varied depending on where the wave was observed relative to the <span class="hlt">substorm</span>. Typically, positive azimuthal wave numbers, m, were observed in waves generated to the east of the <span class="hlt">substorms</span> and negative m to the west. The magnitude of m typically increased with the azimuthal separation between the wave observation and the <span class="hlt">substorm</span> location. The energies estimated for the driving particles for these 83 wave events were found to be highest when the waves were observed closer to the <span class="hlt">substorm</span> and lowest farther away. Each of the 83 events studied by James et al. (2013) involved just a single wave observation per <span class="hlt">substorm</span>. Here a study of three individual <span class="hlt">substorm</span> events are presented, with associated observations of multiple ULF waves using various different SuperDARN radars. We demonstrate that a single <span class="hlt">substorm</span> is capable of driving a number of wave events characterized by different azimuthal scale lengths and wave periods, associated with different energies, W, in the driving particle population. We find that similar trends in m and W exist for multiple wave events with a single <span class="hlt">substorm</span> as was seen in the single