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Sample records for magnetospheric substorms occurring

  1. 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.

  2. 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.

  3. Postmidnight chorus - A substorm phenomenon. [outer magnetosphere

    NASA Technical Reports Server (NTRS)

    Tsurutani, B. T.; Smith, E. J.

    1974-01-01

    The ELF emissions were detected in the midnight sector of the magnetosphere in conjunction with magnetospheric substorms. The emissions were observed at local midnight and early morning hours and are accordingly called 'post-midnight chorus.' The characteristics of these emissions such as their frequency time structure, emission frequency with respect to the local equatorial electron gyrofrequency, intensity-time variation, and the average intensity were investigated. The occurrence of the chorus in the nightside magnetosphere was investigated as a function of local time, L shell, magnetic latitude, and substorm activity, and the results of this analysis are presented. Specific features of postmidnight chorus are discussed in the context of possible wave-particle interactions occurring during magnetospheric substorms.

  4. Magnetospheric substorms - A newly emerging model

    NASA Astrophysics Data System (ADS)

    Akasofu, S.-I.

    1981-10-01

    A surge of progress in magnetospheric substorm studies is expected by the following three recent developments: (1) the finding of the solar wind-magnetosphere energy coupling function epsilon, (2) the determination of the Pedersen current distribution over the entire polar region, and (3) a new understanding of the auroral potential structure. In this paper, the significance of the three developments and the newly emerging model of magnetospheric substorms is described.

  5. Multipoint Observations of Magnetospheric Processes Relevant to the Substorm Events

    NASA Astrophysics Data System (ADS)

    Sibeck, D. G.; Gutynska, O.; Fok, M. C. H.

    2015-12-01

    We present several case studies of simultaneous multipoint observations of hot ion (~30-2200 keV) injections that occur during substorms in the day- and night-side of magnetosphere from THEMIS, RBSP and MMS probes. We complement them with observations of magnetic field signatures to estimate time delays of earthward plasma flows at multiple probes. We discuss the mechanisms that trigger substorm onset comparing the observations with inner plasma sheet simulations.

  6. 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.

  7. Explosive magnetic reconnection - puzzle to be solved as the energy supply process for magnetospheric substorms

    SciTech Connect

    Akasofu, S.I.

    1985-01-01

    It is pointed out that magnetospheric substorms are perhaps the most basic type of disturbances which occur throughout the magnetosphere. There is little doubt that the energy for magnetospheric substorms is delivered from the sun to the magnetosphere by the solar wind, and theoretical and observational studies have been conducted to uncover the processes associated with the energy transfer from the solar wind to the magnetosphere, and the subsequent processes leading to various magnetospheric substorm phenomena. It has been widely accepted that explosive magnetic reconnection supplies the energy for magnetospheric substorm processes. It is indicated that the auroral phenomena must be various manifestations of a large-scale electrical discharge process which is powered by the solar wind-magnetosphere dynamo. Certain problems regarding explosive magnetic reconnection are discussed. 23 references.

  8. Explosive magnetic reconnection - Puzzle to be solved as the energy supply process for magnetospheric substorms?

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1985-01-01

    It is pointed out that magnetospheric substorms are perhaps the most basic type of disturbances which occur throughout the magnetosphere. There is little doubt that the energy for magnetospheric substorms is delivered from the sun to the magnetosphere by the solar wind, and theoretical and observational studies have been conducted to uncover the processes associated with the energy transfer from the solar wind to the magnetosphere, and the subsequent processes leading to various magnetospheric substorm phenomena. It has been widely accepted that explosive magnetic reconnection supplies the energy for magnetospheric substorm processes. It is indicated that the auroral phenomena must be various manifestations of a large-scale electrical discharge process which is powered by the solar wind-magnetosphere dynamo. Certain problems regarding explosive magnetic reconnection are discussed.

  9. 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.

  10. A global magnetosphere-ionosphere coupling model of substorms

    SciTech Connect

    Kan, J.R.

    1993-10-01

    A global model of substorms is proposed on the basis of observational synthesis and theoretical modeling. Since the theoretical basis of the present model is the magnetosphere-ionosphere coupling (MIC) process, it will be called the MIC model of substorms. Substorms can occur in the MIC model without a new X line formed in the near-Earth plasma sheet, in contrast to the highly popular near-Earth neutral line (NENL) model of substorms. Following enhanced dayside reconnection, the ionosphere overloads both the solar wind on open field lines and the plasma sheet on closed field lines. The solar wind responds to the overload by providing more driven energy from the dynamo action on open field lines. The plasma sheet responds to the overload by collapsing itself, i.e., dipolarizing its field configuration to form the substorm current wedge. The explosive intensification during the expansion phase is powered by releasing the magnetic energy stored on closed field lines in the plasma sheet. The stored energy is released by the unloading instability driven by a positive feedback in the substorm current wedge. 68 refs., 6 figs., 1 tab.

  11. 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.

  12. 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.

  13. 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.

  14. Injection of relativistic electrons into the internal magnetosphere during magnetic storms: Connection with substorms

    NASA Astrophysics Data System (ADS)

    Lazutin, L. L.

    2013-11-01

    The connection between rapid increases in the intensity of electrons with energies >0.3 MeV and magnetospheric substorms was studied for the first time by measurements of energetic electrons on the low-orbit SERVIS-1 satellite. In addition to the well-known process of radial diffusion detected at the recovery phase, the increases during a period of time no longer than 1.5 h at the main phase of six magnetic storms in a channel of 0.3-1.7 MeV (in three of them, in a channel of 1.7-3.4 MeV) were measured. An analysis of auroral zone magnetograms demonstrated that the increases occurred at the instant of magnetospheric substorm activation. A conclusion is made that the increases are caused by the radial injection of electrons by a pulse electric field induced during substorm activations. Pulse injections are shown to be one of the main mechanisms of electron radiation belt completion in the inner magnetosphere and, in combination with moderate radial diffusion, to be responsible for the appearance of large fluxes of energetic electrons ("killers") in the magnetosphere after magnetic storms.

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

    SciTech Connect

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

    1982-08-01

    Using substorm currents derived from the Rice computer simulation of the substorm event of September 19, 1976, we have computed theoretical magnetograms as a function of universal time for various stations. A theoretical Dst has also been computed. Our computed magnetograms were obtained by integrating the Biot-Savart law over a maze of approximately 2700 wires and bands that carry the ring currents, the Birkeland currents, and the horizontal ionospheric currents. Ground currents and dynamo currents were neglected. Computed contributions to the magnetic field perturbation from eleven different kinds of currents are displayed (e.g., ring currents, northern hemisphere Birkeland currents). First, overall agreement of theory and data is generally satisfactory, especially for stations at high and mid-magnetic latitudes. Second, model results suggest that the ground magnetic field perturbations arise from very complicated combinations of different kinds of currents and that the magnetic field disturbances due to different but related currents often cancel each other, despite the fact that complicated inhomogeneous conductivities in our model prevent rigorous application of Fukushima's theorem. Third, both the theoretical and observed Dst decrease during the expansion phase of the substorm, but data indicate that Dst relaxes back toward its initial value within about an hour after the peak of the substorm. Fourth, the dawn-dusk asymmetry in the horizontal component of magnetic field disturbance at low latitudes in a substorm is essentially due to a net downward Birkeland current at noon, net upward current at midnight, and generally antisunward flowing electrojets; it is not due to a physical partial ring current injected into the duskside of the inner magnetosphere.

  16. The reason for magnetospheric substorms and solar flares

    NASA Technical Reports Server (NTRS)

    Heikkila, W. J.

    1983-01-01

    It has been proposed that magnetospheric substorms and solar flares are a result of the same mechanism. It is suggested that this mechanism is connected with the escape, or attempted escape, of energized plasma from a region of closed magnetic field lines bounded by a magnetic bottle. In the case of the earth, it must be plasma that is able to maintain a discrete auroral arc, and it is proposed that the cross-tail current connected to the arc is filamentary in nature to provide the field-aligned current sheet above the arc.

  17. Problems with mapping the auroral oval and magnetospheric substorms

    NASA Astrophysics Data System (ADS)

    Antonova, E. E.; Vorobjev, V. G.; Kirpichev, I. P.; Yagodkina, O. I.; Stepanova, M. V.

    2015-10-01

    Accurate mapping of the auroral oval into the equatorial plane is critical for the analysis of aurora and substorm dynamics. Comparison of ion pressure values measured at low altitudes by Defense Meteorological Satellite Program (DMSP) satellites during their crossings of the auroral oval, with plasma pressure values obtained at the equatorial plane from Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite measurements, indicates that the main part of the auroral oval maps into the equatorial plane at distances between 6 and 12 Earth radii. On the nightside, this region is generally considered to be a part of the plasma sheet. However, our studies suggest that this region could form part of the plasma ring surrounding the Earth. We discuss the possibility of using the results found here to explain the ring-like shape of the auroral oval, the location of the injection boundary inside the magnetosphere near the geostationary orbit, presence of quiet auroral arcs in the auroral oval despite the constantly high level of turbulence observed in the plasma sheet, and some features of the onset of substorm expansion.

  18. 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.

  19. Coordinated observations of the magnetosphere - The development of a substorm.

    NASA Technical Reports Server (NTRS)

    Mende, S. B.; Sharp, R. D.; Shelley, E. G.; Haerendel, G.; Hones, E. W.

    1972-01-01

    Coordinated observations of a substorm are reported by using data from all-sky camera (ASCA) stations near the northern conjugate of the ATS 5 geostationary satellite, plasma and magnetic-field experiments on the ATS 5 satellite, Vela 5B at 18 earth radii in the magnetotail, the Heos 1 interplanetary probe, and ground-based magnetograms. The substorm event occurred after a very quiet day and was preceded by a development period during which the interplanetary field turned southward and the plasma energy density increased near the earth on the nightside. This period was also evidenced by a depression of the midlatitude H component of the geomagnetic field at the earth's surface. The auroral breakup was preceded by the appearance of quiet arcs, the leveling off of the plasma energy density increase at ATS, and the disappearance of the tail plasma at 18 earth radii.

  20. On the relationship between the growth and expansion phases of substorms and magnetospheric convection.

    NASA Technical Reports Server (NTRS)

    Mozer, F. S.

    1973-01-01

    The definition of the growth and expansion phases of substorms is considered in terms of temporal sequences of magnetospheric convection. It is suggested that the definition of these phases should rest on magnetospheric convection theories and data because of the ambiguities in the interpretation of ground magnetometer records from which these concepts arose originally. Reviewed data are shown to offer strong evidence for the validity and usefulness of the concepts of substorm growth and expansion phases.

  1. A Numerical Simulation of Impulses in the Magnetosphere Associated with Substorms: OpenGGCM Result

    NASA Astrophysics Data System (ADS)

    Ferdousi, B.; Raeder, J.

    2015-12-01

    The onset of substorms is still an unsolved problem in Space Physics even though many physical models explaining the substorm process have been proposed. Distinguishing the processes that occur during first 2 minutes of substorm process depends critically on the correct timing of different signals in the plasma sheet and the ionosphere. This has been difficult to accomplish with data alone, since signals are sometimes ambiguous, or they have not been observed at the right locations. To investigate signal propagation paths and signal travel times, we use OpenGGCM global simulation. By launching impulses from various locations in the tail, we investigate the path taken by the waves and the time it takes for different waves to reach the ionosphere. We find that it takes around 60 seconds for waves to travel from 30 RE to the ionosphere, contrary to many previous reports. We also find that the Tamao path is not generally the preferred path for waves originating in the plasma sheet, and that waves travel faster through the lobes. In addition, we find that a point source in the tail around 10-15 RE leads to spread-out signals in the ionosphere, whereas a point source further down in the tail around 20-30 RE leads to more localized signatures in the ionosphere. We also use the same technique to launch impulses in the dayside magnetosphere, and we find it takes less than 1 minute for wave to travel from the dayside to the nightside.

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. 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.

  6. Satellite studies of magnetospheric substorms on August 15, 1968. IX - Phenomenological model for substorms.

    NASA Technical Reports Server (NTRS)

    Mcpherron, R. L.; Russell, C. T.; Aubry, M. P.

    1973-01-01

    Observations made during three substorms on August 15, 1968, are shown to be consistent with current theoretical ideas about the cause of substorms. The phenomenological model described in several preceding papers is further expanded. This model follows closely the theoretical ideas presented more quantitatively in recent papers by Coronti and Kennel (1972 and 1973).

  7. 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

  8. 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.

  9. Correlation between convection electric fields in the nightside magnetosphere and several wave and particle phenomena during two isolated substorms.

    NASA Technical Reports Server (NTRS)

    Carpenter, D. L.; Fraser-Smith, A. C.; Unwin, R. S.; Hones, E. W., Jr.; Heacock, R. R.

    1971-01-01

    Correlation of several magnetoionospheric wave and particle phenomena previously linked observationally to magnetospheric substorms and inferred to involve convection electric fields with whistler measurements of convection activity during two relatively isolated substorms. The events occurred at about 0600 UT on July 15, 1965, and about 0500 UT on Oct. 13, 1965. The correlated phenomena include cross-L inward plasma drifts near midnight within the plasmaphere, diffuse auroral radar echoes observed near the dusk meridian, IPDP micropulsations (intervals of pulsations of diminishing period) in the premidnight sector, apparent contractions and expansions of the plasma sheet at about 20 earth radii in the magnetotail, and Pc 1/Pi 1 micropulsation events near or before midnight. Two new vlf phenomena occurred during the October 13 event - a noise band within the plasmasphere associated with a convecting whistler path, and ?hisslers,' falling-tone auroral-hiss forms repeated at intervals of about 2 sec.

  10. 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.

  11. Pseudobreakup and substorm growth phase in the ionosphere and magnetosphere

    SciTech Connect

    Koskinin, H.E.J.; Pellinen, R.J.; Pulkkinen, T.I. ); Lopez, R.E. ); Baker, D.N. ); Boesinger, T. )

    1993-04-01

    The authors present space and ground based observations made during the growth phase and the onset of a substorm on August 31, 1986. Roughly 20 minutes after the [var epsilon] parameter at the magnetopause had exceeded 10[sup 11] W, the AMPTE Charge Composition Explorer spacecraft observed an increase in energetic particle fluxes consistent with magnetic field depolarization. The craft was close to magnetic midnight at a geocentric distance of 8.7R[sub E]. The event had the initial signature of a substorm onset, but it did not lead to a full-scale substorm expansion based on several ground based observations. There were no large particle injection events at geostationary orbit. After another 20 minutes the event did enter a normal substorm expansion phase. The authors interpret the initial activation as a [open quotes]pseudobreakup[close quotes]. They correlate observations made by spacecraft in the near-Earth plasma sheet, with ground based observations of the ionospheric development from magnetometer and electric field measurements from the STARE radar. The strength and the consequences are concluded to be the main differences of pseudobreakups and ordinary breakups.

  12. 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.

  13. A Modeling substorm Dynamics of the Magnetosphere Using Self-Organized Criticality Approach

    NASA Astrophysics Data System (ADS)

    Bolzan, Mauricio; Rosa, Reinaldo

    2016-07-01

    Responses of Earth magnetic field during substorms exhibits a number of characteristics features such as the power-law spectra of fluctuations on different scales and signatures of low effective dimensions. Due the magnetosphere are constantly out-equilibrium their behavior is similar to real sandpiles during substorms, features of self-organized criticality (SOC) systems. Thus, in this work we presented a simple mathematical model to AE-index based on self-organizing sandpile mentioned by Uritsky and Pudovkin (1998), but we input the dissipation process inside the model. The statistical and multifractal tools to characterization of dynamical processes was used.

  14. Response of dayside Pc 5 pulsations to substorm activity in the nighttime magnetosphere

    NASA Astrophysics Data System (ADS)

    Samson, J. C.; Rostoker, G.

    1981-02-01

    The possibility of using ULF (1-20 mHz) waves to diagnose the structure of the magnetosphere has recently given new impetus to the study of Pc 4,5 magnetic pulsations. In this paper it is demonstrated that the frequency spectrum of dayside Pc 4,5 pulsations near noon may be significantly altered in association with the onset of a magnetospheric substorm near midnight. The response time for the dayside Pc pulsations to a substorm onset can be as short as 2-3 min, suggesting information transfer across the magnetosphere at velocities of the order of the Alfven speed. The characteristic response of the dayside pulsations is a marked increase in the dominant frequency at stations inside the dayside auroral oval. The results taken together with the observations of dayside auroras by Eather et al. (1979) suggest that substorm onsets are accompanied by a sudden inward motion of the center of the partial ring current. It is proposed that this ring current motion causes changes in the magnetic field in the equatorial plane of the magnetosphere that result in changes in the Alfven velocity on field lines where the magnetic pulsations are observed. Possible mechanisms for the generation of Pc 4,5 pulsations are discussed in the light of the observations reported.

  15. Response of dayside Pc 5 pulsations to substorm activity in the nighttime magnetosphere

    SciTech Connect

    Samson, J.C.; Rostoker, G.

    1981-02-01

    The possibility of using ULF (1-20 mHz) waves to diagnose the structure of the magnetosphere has recently given new impetus to the study of Pc 4,5 magnetic pulsations. In this paper we demonstrate that the frequency spectrum of dayside Pc 4,5 pulsations near noon may be significantly altered in association with the onset of a magnetospheric substorm near midnight. The response time for the dayside Pc pulsations to a substorm onset can be as short as 2-3 min, suggesting information transfer across the magnetosphere at velocities of the order of the Alfven speed. The characteristic response of the dayside pulsations is a marked increase in the dominant frequency at stations inside the dayside auroral oval. Our results taken together with the observations of dayside auroras by Eather et al. (1979) suggest that substorm onsets are accompanied by a sudden inward motion of the center of the partial ring current. We propose that this ring current motion causes changes in the magnetic field in the equatorial plane of the magnetosphere that result in changes in the Alfven velocity on field lines where the magnetic pulsations are observed. Possible mechanisms for the generation of Pc 4,5 pulsations are discussed in the light of the observations reported in this paper.

  16. 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.

  17. 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.

  18. 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

  19. Substorm and magnetosphere characteristic scales inferred from the SuperMAG auroral electrojet indices

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    A generalization of the traditional 12-station auroral electrojet (AE) index to include more than 100 magnetometer stations, SME, is an excellent predictor of global auroral power (AP), even at high cadence (1 min). We use this index, and a database of more than 53,000 substorms derived from it, covering 1980-2009, to investigate time and energy scales in the magnetosphere, during substorms and otherwise. We find, contrary to common opinion, that substorms do not have a preferred recurrence rate but instead have two distinct dynamic regimes, each following a power law. The number of substorms recurring after a time Δt, N(Δt), varies as Δt-1.19 for short times (<80 min) and as Δt-1.76 for longer times (>3 hours). Other evidence also shows these distinct regimes for the magnetosphere, including a break in the power law spectra for SME at about 3 hours. The time between two consecutive substorms is only weakly correlated (r = 0.18 for isolated and r = 0.06 for recurrent) with the time until the next, suggesting quasiperiodicity is not common. However, substorms do have a preferred size, with the typical peak SME magnitude reaching 400-600 nT, but with a mean of 656 nT, corresponding to a bit less than 40 GW AP. More surprisingly, another characteristic scale exists in the magnetosphere, namely, a peak in the SME distribution around 61 nT, corresponding to about 5 GW precipitating AP. The dominant form of auroral precipitation is diffuse aurora; thus, these values are properties of the magnetotail thermal electron distribution. The characteristic 5 GW value specifically represents a preferred minimum below which the magnetotail rarely drops. The magnetotail experiences continuous loss by precipitation, so the existence of a preferred minimum implies driving that rarely disappears altogether. Finally, the distribution of SME values across all times, in accordance with earlier work on AE, is best fit by the sum of two distributions, each normal in log(SME). The lower

  20. Simultaneous observations of earthward flow bursts and plasmoid ejection during magnetospheric substorms

    NASA Astrophysics Data System (ADS)

    Slavin, J. A.; Fairfield, D. H.; Lepping, R. P.; Hesse, M.; Ieda, A.; Tanskanen, E.; Østgaard, N.; Mukai, T.; Nagai, T.; Singer, H. J.; Sutcliffe, P. R.

    2002-07-01

    Examination of observations taken by radially aligned International Solar Terrestrial Physics spacecraft in the nightside magnetosphere on 9 July 1997 has revealed close temporal correlations between earthward flow bursts in the plasma sheet and the ejection of plasmoids. A one-dimensional model of plasma sheet flow is applied to these observations to determine the time and location for the initiation of lobe flux tube reconnection. For the single clear flow burst-plasmoid pair observed during the first substorm and the three pairs produced by the second substorm, lobe flux reconnection was inferred to have started at X ~ -15 to -18 RE, respectively, about 2-5 min prior to the observations of substorm expansion phase onset. These time delays and propagation speeds are shown to be consistent with the measured plasma sheet bulk flow speeds. Substorm expansion phase onset was essentially coincident with the arrival of the flow bursts at Geotail, which was located near the inner edge of the plasma sheet at X ~ -9 RE. The dipolarization of the magnetic field at geosynchronous orbit, auroral kilometric radiation (AKR) emissions, Pi2 pulsations, high-latitude negative magnetic bays, and auroral breakup marking substorm expansion onset are all coincident within the +/-1 min resolution of the measurements. Accordingly, it appears that earthward of the inner edge of the plasma sheet, where Geotail was located, substorm effects propagated at speeds comparable to the Alfven speed characteristic of the high-latitude inner magnetosphere, ~103 km s-1. In summary, the results of our investigation strongly support the modern near-Earth neutral line (NENL) model of substorms in which the onset of lobe flux tube reconnection in the near tail is followed ~2-5 min later by the braking of earthward flow bursts as they encounter the inner magnetosphere and within ~1 min, by Pi2s generations, current wedge development, and AKR and auroral expansion, and finally, ~10-20 min later, by the

  1. 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.

  2. Cellular Model Analogy of The Magnetosphere-ionosphere Substorm Activity Driven By Solar Wind With Finite Velocity of Penetration Into Magnetosphere

    NASA Astrophysics Data System (ADS)

    Kozelov, B. V.; Kozelova, T. V.

    The cellular model as an analogy of the dynamic magnetosphere-ionosphere system related with the substorm activity is presented. Each cell in the model contains two connected parts, one of which may be associated with the magnetosphere current sheet pieces, and other part may be associated with ionosphere region at the same magnetic field line. The magnetospheric part of the model system is organised as a rectangu- lar cellular automation with local redistribution of the stored energy from the cells where the threshold value is exceeded. We suppose that the threshold value in each cell depends on external driver (solar wind parameters) which influences on the long boundaries of the rectangular array. The finite velocity is assumed for the influence penetration into the array and along boundaries. Observational studies of magneto- spheric activity suggest that the magnetosphere-ionosphere coupling plays a critical role in the physical processes leading up to substorm onset. The local reallocation of energy in the magnetosphere causes a local change of conductivity of the ionosphere in the same magnetic tube (the particles, diffused by pitch-angle, are precipitated in the loss-cone along the magnetic field, and ionize atmospheric gases). In turn, the iono- spheric conductivity influences the value of energy, which may be reallocated in the magnetic tube at the following time moment. This positive feedback has been included in the model also. The state (conductivity) of the ionospheric part of a cell is supposed to depend on the cell history (by analogy with the recombination coefficient). Dynam- ics of the model for different parameters and for driving by real Bz IMF is discussed. The model demonstrates the small-scale transients which are directly driven by Bz, and the large-scale transients which depends on the system history also. The onsets of the large scale-transients (which associate with substorms) are occurred at the differ- ent positions in the array (as

  3. 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.

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

    DOE PAGESBeta

    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.; et al

    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

  5. 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.

  6. 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.

  7. 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.

  8. Aspects of magnetosphere-ionosphere coupling in sawtooth substorms: a case study

    NASA Astrophysics Data System (ADS)

    Sandholt, P. E.; Farrugia, C. J.

    2014-10-01

    In a case study we report on repetitive substorm activity during storm time which was excited during Earth passage of an interplanetary coronal mass ejection (ICME) on 18 August 2003. Applying a combination of magnetosphere and ground observations during a favourable multi-spacecraft configuration in the plasma sheet (GOES-10 at geostationary altitude) and in the tail lobes (Geotail and Cluster-1), we monitor the temporal-spatial evolution of basic elements of the substorm current system. Emphasis is placed on activations of the large-scale substorm current wedge (SCW), spanning the 21:00-03:00 MLT sector of the near-Earth plasma sheet (GOES-10 data during the interval 06:00-12:00 UT), and magnetic perturbations in the tail lobes in relation to ground observations of auroral electrojets and convection in the polar cap ionosphere. The joint ground-satellite observations are interpreted in terms of sequential intensifications and expansions of the outer and inner current loops of the SCW and their respective associations with the westward electrojet centred near midnight (24:00 MLT) and the eastward electrojet observed at 14:00-15:00 MLT. Combined magnetic field observations across the tail lobe from Cluster and Geotail allow us to make estimates of enhancements of the cross-polar-cap potential (CPCP) amounting to ≈ 30-60 kV (lower limits), corresponding to monotonic increases of the PCN index by 1.5 to 3 mV m-1 from inductive electric field coupling in the magnetosphere-ionosphere (M-I) system during the initial transient phase of the substorm expansion.

  9. 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.

  10. PC index as a proxy of the solar wind energy that entered into the magnetosphere: Development of magnetic substorms

    NASA Astrophysics Data System (ADS)

    Troshichev, O. A.; Podorozhkina, N. A.; Sormakov, D. A.; Janzhura, A. S.

    2014-08-01

    The Polar Cap (PC) index has been approved by the International Association of Geomagnetism and Aeronomy (IAGA XXII Assembly, Merida, Mexico, 2013) as a new index of magnetic activity. The PC index can be considered to be a proxy of the solar wind energy that enters the magnetosphere. This distinguishes PC from AL and Dst indices that are more related to the dissipation of energy through auroral currents or storage of energy in the ring current during magnetic substorms or storms. The association of the PC index with the direct coupling of the solar wind energy into the magnetosphere is based upon analysis of the relationship of PC with parameters in the solar wind, on the one hand, and correlation between the time series of PC and the AL index (substorm development), on the other hand. This paper (the first of a series) provides the results of statistical investigations that demonstrate a strong correlation between the behavior of PC and the development of magnetic substorms. Substorms are classified as isolated and expanded. We found that (1) substorms are preceded by growth in the RS index, (2) sudden substorm expansion onsets are related to "leap" or "reverse" signatures in the PC index which are indicative of a sharp increase in the PC growth rate, (3) substorms start to develop when PC exceeds a threshold level 1.5 ± 0.5 mV/m irrespective of the length of the substorm growth phase, and (4) there is a linear relation between the intensity of substorms and PC for all substorm events.

  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. 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.

  13. 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.

  14. Ground-based and in-situ timing of substorm expansion phase onset: Locating the initiation region and determining the timescale of magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

    Rae, I. J.; Mann, I. R.; Murphy, K. R.; Milling, D. K.; Watt, C. E.; Angelopoulos, V.; Frey, H. U.; Glassmeier, K.; Auster, U.; Sibeck, D.; Singer, H.

    2009-05-01

    Despite the characterisation of the auroral substorm more than 40 years ago, controversy still surrounds the processes triggering substorm onset initiation. Using ground-based magnetometers from CARISMA and THEMIS and in-situ magnetic observations by THEMIS and GOES, we present the results obtained from an objective wavelet-based technique to determine the first onset of ULF wave activity during expansion phase onset on the ground and in space. We validate ground-based ULF timing against the large-scale IMAGE FUV and smaller-scale THEMIS ASI auroral observations. We find clear, coherent and repeatable characteristics of these ULF waves on the ground indicating a localized onset epicentre that provides a clear and strong constraint on the location in time and space of expansion phase onset. Furthermore, we show that the onset of ULF wave activity in space occurs contemporaneously with the onset of ULF wave activity on the ground, suggesting that magnetosphere-ionosphere coupling may occur remarkably fast during the onset process, perhaps by means of energetic electron precipitation that have been accelerated via shear Alfvén waves. Furthermore, we outline the characteristics of ULF pulsations in both the Pi1 and Pi2 bands in the nightside ionosphere and magnetosphere during substorms. We describe the use of these techniques in creating a substorm onset database during the THEMIS era for use by the scientific community. Finally, we detail the development of a Canadian AE calculation that will be routinely available at the Canadian Space Sciences Data Portal (www.cssdp.ca)

  15. 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

  16. 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.

  17. Numerical experiments on possible impact of substorms on energetic electrons in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Ebihara, Y.; Fok, M. C. H.; Tanaka, T.

    2014-12-01

    The abrupt reconstruction of the outer radiation belt is often observed after substorms, and is believed to result from internal acceleration or external transport. The internal acceleration is thought to take place outside the plasmapause through Doppler shifted cyclotron resonance, or relativistic turning acceleration with whistler mode chorus waves. Electrons are thought to be accelerated by the waves when characteristic pitch angle distribution, hard energy spectrum and earthward gradient of phase space density are identified, but it seems that direct observational evidence for the energy transfer from waves to electrons has not been explicitly provided. The external transport is thought to take place when electrons are accelerated by strong electric fields. We have solved bounce-averaged drift transport equations under the electric and magnetic fields given by the recently developed global MHD simulation. We reproduced the sequence of a substorm, and determined onset as a sudden decrease in the AL index and a sudden increase in the ionospheric conductivity (a proxy of aurora). Near the onset, a strong electric field is formed in the inner magnetosphere in a longitudinally narrow region with a thickness of the order of earth radius (Re), which rapidly transported relativistic electrons inward. Simultaneously, keV electrons were also injected inward, which may become a seed of relativistic electrons. Temperature anisotropy becomes large near the leading edge of the injected hot electrons. As the plasmapause shrinks, the ratio of the plasma frequency to the cyclotron frequency becomes small outside the plasmapause, which may favor the growth of chorus waves. We estimated the evolution of the phase space density of electrons due to the interaction with chorus waves under the assumption that the wave amplitude is small. We will demonstrate the results of numerical experiments on the energy spectrum, pitch angle distribution and radial gradient of the phase space

  18. 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.

  19. 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.

  20. A quantitative study of magnetospheric magnetic field line deformation by a two-loop substorm current wedge

    NASA Astrophysics Data System (ADS)

    Nikolaev, A. V.; Sergeev, V. A.; Tsyganenko, N. A.; Kubyshkina, M. V.; Opgenoorth, H.; Singer, H.; Angelopoulos, V.

    2015-04-01

    Substorm current wedge (SCW) formation is associated with global magnetic field reconfiguration during substorm expansion. We combine a two-loop model SCW (SCW2L) with a background magnetic field model to investigate distortion of the ionospheric footpoint pattern in response to changes of different SCW2L parameters. The SCW-related plasma sheet footprint shift results in formation of a pattern resembling an auroral bulge, the poleward expansion of which is controlled primarily by the total current in the region 1 sense current loop (I1). The magnitude of the footprint latitudinal shift may reach ∼ 10° corrected geomagnetic latitude (CGLat) during strong substorms (I1= 2 MA). A strong helical magnetic field around the field-aligned current generates a surge-like region with embedded spiral structures, associated with a westward traveling surge (WTS) at the western end of the SCW. The helical field may also contribute to rotation of the ionospheric projection of narrow plasma streams (auroral streamers). Other parameters, including the total current in the second (region 2 sense) loop, were found to be of secondary importance. Analyzing two consecutive dipolarizations on 17 March 2010, we used magnetic variation data obtained from a dense midlatitude ground network and several magnetospheric spacecraft, as well as the adaptive AM03 model, to specify SCW2L parameters, which allowed us to predict the magnitude of poleward auroral expansion. Auroral observations made during the two substorm activations demonstrate that the SCW2L combined with the AM03 model nicely describes the azimuthal progression and the observed magnitude of the auroral expansion. This finding indicates that the SCW-related distortions are responsible for much of the observed global development of bright auroras.

  1. Connections between large-scale transport to the inner magnetosphere from the distant plasma sheet, region 2 coupling to the ionosphere, and substorm and storm dynamics (Invited)

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Wang, C.; Zou, S.; Gkioulidou, M.; Nishimura, Y.; Shi, Y.; Kim, H.; Xing, X.; Nicolls, M. J.; Heinselman, C. J.

    2009-12-01

    Studies using a variety of ground-based and spacecraft observations, as well as the Rice Convection Model, have taught us much about the connection between plasma sheet transport and particle distributions within the inner plasma sheet. These studies have shown that plasma moves earthward (equatorward in the ionosphere) after enhancements in convection to reach the near-Earth plasma sheet, leading to the enhancements in plasma sheet pressure that are responsible for the growth phase of substorms and the partial ring current. The highest inner plasma sheet pressures likely occur in the subauroral polarization streams (SAPS) region of the evening-side convection cell, lying equatorward of the Harang reversal. Both the Harang reversal and SAPS are manifestations of the region 2 (R2) electrodynamical coupling, so that transport to the near-Earth plasma sheet is strongly influenced by the R2 magnetosphere-ionosphere coupling. Modeling results show that this transport, together with the concurrent R2 coupling, is also strongly dependent on the plasma distributions that enter the plasma sheet. However, the entering plasma distribution is expected to have substantial spatial and temporal structure, which should impart substantial spatial structure and time dependencies to the inner plasma sheet particle distributions. In addition, very recent analyses indicate that the temporal variations of the particle distribution entering the plasma sheet, and the ensuing transport of new particle distributions within the plasma sheet, is fundamental to understanding the substorm expansion phase. Taken together, the above results indicate that an important understanding of inner magnetosphere particle distributions and their dynamics, as well as of major geomagnetic disturbances, is likely to come from integrated studies of plasma sheet particle entry, particle transport, and electrodynamical coupling to the ionosphere.

  2. Active experiments, magnetospheric modification, and a naturally occurring analogue

    NASA Technical Reports Server (NTRS)

    Kivelson, M. G.; Russell, C. T.

    1973-01-01

    Recently, a scheme has been proposed which would modify the magnetosphere by injecting plasma near the equator beyond the plasmapause and initiating wave-particle instabilities. The expected effects have been examined theoretically. Injection of plasma into this region is also a naturally occurring phenomenon produced by the cross-tail electric fields which are associated with geomagnetic activity. For further investigation of magnetospheric instabilities, the advantages of examining artificially injected plasma (control of time and location of injection and of the volume of plasma injected) contrast with the advantages of studying natural enhancements (no extra payload, frequent occurrence). Thus, the two types of experiments are complementary. In preliminary studies of natural plasma enhancements both ULF and ELF emissions have been observed. The ELF noise is consistent with generation by the electron cyclotron instability.

  3. 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.

  4. 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.

  5. 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 (

  6. 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.

  7. Micro- and meso-scale simulations of magnetospheric processes related to the aurora and substorm morphology. Final technical report, June 1989-November 1991

    SciTech Connect

    Swift, D.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.

  8. Field-aligned fluxes of energetic electrons related to the onset of magnetospheric substorms

    NASA Astrophysics Data System (ADS)

    Kremser, G.; Korth, A.; Ullaland, S. L.; Roux, A.; Perraut, S.; Pedersen, A.; Schmidt, R.; Tanskanen, P.

    1987-08-01

    Observations of bidirectional field-aligned fluxes of energetic electrons (16 to 80 keV) at magnetic substorm onset are discussed. The electron fluxes appear 4 min after the onset of the expansion phase, last 1.5 min, and are associated with strong spatial gradients of the ion intensity. The observations are interpreted in terms of a model in which a surface wave develops at the transition from dipolelike to taillike geomagnetic fieldlines. The surface wave couples into kinetic Alfven waves that propagate along the fieldlines, are reflected at the ionosphere, and interact with mirrored electrons on their way back towards the equatorial plane.

  9. 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.

  10. 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.

  11. A theory of substorms: Onset and subsidence

    SciTech Connect

    Kan, J.R.; Zhu, L.; Akasofu, S.I. )

    1988-06-01

    It is shown by a computer simulation study of the magnetosphere-ionosphere (M-I) coupling that an enhanced magnetospheric convection can lead to auroral substorm onset in about 40 min after a southward turning of IMF. The simulation results show that the enhanced M-I coupling can produce intense upward field-aligned currents in the midnight sector near the poleward boundary of a high-conductance belt associated with the diffuse auroral precipitation. Two necessary conditions for substorm onset are that (1) the polar cap potential must exceed a certain value and (2) the convection reversal region must overlap with the poleward gradient of the diffuse auroral conductance in the ionosphere in the midnight sector. The matching ensures that the divergence of the Pedersen current colocates with the divergence of the Hall current to maximize the upward field-aligned current near the poleward boundary of the diffuse aurora in the midnight sector for substorm onset. Without the matching, the auroral brightening would not occur, even if the electrojets are appreciable. Substorm subsides when one of the two necessary conditions is no longer satisfied. This can occur owing either to a northward turning of the IMF or weakening of Alfven shielding due to substorm enhancement of the ionospheric conductance during a prolonged southward IMF.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Tail reconnection triggering substorm onset.

    PubMed

    Angelopoulos, Vassilis; McFadden, James P; Larson, Davin; Carlson, Charles W; Mende, Stephen B; Frey, Harald; Phan, Tai; Sibeck, David G; Glassmeier, Karl-Heinz; Auster, Uli; Donovan, Eric; Mann, Ian R; Rae, I Jonathan; Russell, Christopher T; Runov, Andrei; Zhou, Xu-Zhi; Kepko, Larry

    2008-08-15

    Magnetospheric substorms explosively release solar wind energy previously stored in Earth's magnetotail, encompassing the entire magnetosphere and producing spectacular auroral displays. It has been unclear whether a substorm is triggered by a disruption of the electrical current flowing across the near-Earth magnetotail, at approximately 10 R(E) (R(E): Earth radius, or 6374 kilometers), or by the process of magnetic reconnection typically seen farther out in the magnetotail, at approximately 20 to 30 R(E). We report on simultaneous measurements in the magnetotail at multiple distances, at the time of substorm onset. Reconnection was observed at 20 R(E), at least 1.5 minutes before auroral intensification, at least 2 minutes before substorm expansion, and about 3 minutes before near-Earth current disruption. These results demonstrate that substorms are likely initiated by tail reconnection. PMID:18653845

  19. Role of sudden commencements in triggering magnetospheric substorms. M.S. Thesis; [based on ATS 1 data

    NASA Technical Reports Server (NTRS)

    Newell, R. E.

    1974-01-01

    Sudden commencement events are examined in terms of available auroral-zone and low-latitude magnetic field, data, interplanetary plasma and magnetic field data, and magnetospheric electron flux and magnetic field data from the geostationary satellite ATS 1.

  20. Ionospheric influence on the global characteristics of electron precipitation during auroral substorms

    NASA Astrophysics Data System (ADS)

    Chua, Damien Han

    Global auroral images from the Polar Ultraviolet Imager (UVI) and in situ, low altitude particle measurements from the Fast Auroral Snapshot Explorer (FAST) spacecraft are used to investigate the effects of solar wind variations and seasonal variability in the ionosphere on electron precipitation during auroral substorms. Isolated substorms and storm-time, pressure pulse-driven intensifications are compared and we show that the global patterns of precipitating electron energy flux and average energy are markedly different for each class of auroral phenomena. Field-aligned acceleration of auroral electrons in the upward current regions is found to be an essential aspect of the global aurora during isolated substorms. In contrast, the electron precipitation during pressure pulse-driven intensifications is less structured with no indication of field-aligned acceleration. A new method of quantifying the time scales and phases of magnetospheric substorms using the hemispheric power derived from the UVI images is described. We show that substorm time scales vary most strongly with season while IMF orientation plays a secondary role. The recovery time for substorm activity is roughly a factor of two longer when the nightside auroral zone is in darkness (winter and equinox) than when it is sunlit. We find that the longer time scale of substorms occurring in darkness is sustained by discrete auroral features associated with field-aligned potential drops and inertial Alfven waves. These discrete structures exist for shorter time scales, if they are observed at all, during substorms that occur under sunlit conditions. The observed seasonal variations in global auroral structure during substorms are most consistent with the hypothesis that ionospheric boundary conditions strongly influence the effectiveness of auroral acceleration mechanisms that include parallel potentials and Alfven waves. The results presented in this thesis will enhance our understanding of substorm

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

    SciTech Connect

    Elphinstone, R.D.; Hearn, D.J.; Cogger, L.L.

    1995-05-01

    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. The azimuthal wavelengths associated with these onsets were found to range between 132 and 583 km with a mean value of 307 {plus_minus} 115 km. The occurrence rate increased with decreasing wavelength down to a cutoff wavelength near 130 km. 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. The average location of the peak intensity for 80 onsets was 65.9 {plus_minus} 3.5 CGMlat, 22.9 {plus_minus} 1.2 Mlt. AAF onsets occur during time periods when the solar wind pressure is relatively high. These low-latitude wavelike onsets appear as precursors in the form of long-period magnetic pulsations (Pc 5 band) and frequently occur on the equatorward portion of the double oval distribution. AAFs brighten in conjunction with substorm onset leading to the conclusion that they are a growth phase activity causally 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. 88 refs., 20 figs., 3 tabs.

  2. 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

  3. Statistical study of interplanetary condition influence on the geomagnetic substorm onset location inferred from SuperMAG auroral electrojet indices

    NASA Astrophysics Data System (ADS)

    Huang, Sheng; Du, Aimin; Cao, Xin

    2015-04-01

    It is well known that the magnetospheric substorm occurs every few hours, in response with the interplanetary condition variation and the increase of energy transfer from the solar wind to the magnetosphere. Since the substorm activity correlated well with the geomagnetic index, Newell and Gjerloev [2011] identified the substorm onset and its contributing station, using the SuperMag auroral electrojet indices. In this study, we investigate the distribution of these substorm onset locations and its response to the varied interplanetary condition. It is surprise that the substorm onset locations show double-peak structure with one peak around pre-midnight sector and the other at the dawn side. The substorm onset tends to occur in pre-midnight sector during non-storm time while it often takes place in late morning sector (~4 MLT) during storm time. Furthermore, substorms, appearing in magnetic storm main phase predominate in late morning. As the geomagnetic index Dst decreases, the substorm onset occurs in late morning more frequently. The substorm onset locations were also classified based on the solar wind parameters. It is shown that the peak number ratio of the substorm onset location in late morning over pre-midnight increases as IMF Bz decreases from positive to negative and the solar wind velocity Vsw enhances. The more intense interplanetary electric field E promotes the substorm onset occurring in late morning. It is widely accepted that both the directly driven (DD) and loading/unloading (LL/UL) processes play an essential role in the energy dispensation from the solar wind into the magnetosphere-ionosphere system. In general, the former one corresponds to the DP2 current system, which consists of the eastward electrojet centered near the dusk and the westward electrojet centered in the dawn, while the latter one corresponds to the DP1 current system, which is dominated by the westward electrojet in the midnight sector. Our statistical results of substorm

  4. 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.

  5. 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.

  6. The Disruption Zone Model of Magnetospheric Substorms: Reconnection at the Very-near-Earth Neutral Line and the Shape of the Resulting Plasmoid

    NASA Astrophysics Data System (ADS)

    Sofko, G. J.; McWilliams, K. A.; Bryant, C. R.

    2011-12-01

    In the near-Earth magnetotail, the neutral sheet (NSh) is bounded by closed stretched field line regions, which we call Disruption Zones (DZs). There, the magnetic field lines have both outward curvature and an outward gradient, away from the deep minimum in the NSh near about 8 - 12 RE. As a result, there is eastward ion drift and current in the DZs, in contrast to the westward ion drift and current in the NSh. This eastward current interrupts the normal westward plasmasheet current from the dawn to dusk LLBL regions, and is the current disruption that causes the Substorm Current Wedge. A double solenoidal current system develops in which eastward current in the DZs closes to westward current in the NSh. This system supplies more closed magnetic flux to the inner DZs and exerts more magnetic pressure on the NSh, causing it to thin further and move earthward. The DZ eastward ion drifts and currents are strongest where the curvature and the outward gradient of the magnetic field are most intense, namely at the earthward end of the NSh. As a result, that is where reconnection occurs near substorm onset. This location is not the usual near-Earth neutral line (NENL), but is a very near-Earth neutral line (VNENL) in the ~ X = 7 - 11 RE range. Once the reconnection occurs between two antiparallel magnetic field lines in the thin earthward part of the NSh, the tailward line of the reconnection pair becomes the "plasmoid". It has a very distinct shape, namely that of a bottle. The bottle has a long neck which is simply the thinned NSh extending from about 7 to 20 RE. Beyond that is the body of the bottle. When reconnection occurs at the VNENL, sealing the neck of the bottle, the NSh plasma in the neck moves tailward at ~ 200 - 300 km/s and spills into the body of the bottle. In the meantime, the next closed field line moves in to replace the previously reconnected line, plasma from the DZs refills the NSh, and the reconnection continues at the VNENL. When the plasma from

  7. 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.

  8. 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.

  9. 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.

  10. Electron precipitation patterns and substorm morphology.

    NASA Technical Reports Server (NTRS)

    Hoffman, R. A.; Burch, J. L.

    1973-01-01

    Statistical analysis of data from the auroral particles experiment aboard OGO 4, performed in a statistical framework interpretable in terms of magnetospheric substorm morphology, both spatial and temporal. Patterns of low-energy electron precipitation observed by polar satellites are examined as functions of substorm phase. The implications of the precipitation boundaries identifiable at the low-latitude edge of polar cusp electron precipitation and at the poleward edge of precipitation in the premidnight sector are discussed.

  11. Observations of the Ionospheric Response to a Weak Substorm Onset

    NASA Astrophysics Data System (ADS)

    Chartier, A.; Gjerloev, J. W.; Ohtani, S.; Nikoukar, R.; Forte, B.

    2015-12-01

    We present observations of substorm onset at Tromsø, Norway. This event was unusually well observed by ground magnetometers, incoherent scatter radar, satellites, an allsky camera and a scintillation monitor in the vicinity of the onset location. At onset, ground magnetometer observations indicate the formation of a westward electrojet above Tromsø and, at the same location, allsky camera images show an arc brightening and moving poleward. Satellite observations are consistent with an onset location at Tromsø, followed by a westward surge of dipolarization. Two features of the ionospheric response are observed by the incoherent scatter radar at Tromsø: 1) At onset, ion drift velocities reduce sharply from 100-400 m/s to roughly zero, consistent with a field-aligned potential drop shielding the ionosphere from magnetospheric convection. 2) There is a two-stage enhancement of the westward electrojet, with each stage directly preceded by an increase of ionization. Both these features are consistent with the theory that the inner magnetosphere acts neither as a current nor a voltage generator during substorm onset. Figure shows EISCAT observations of line-of-sight ion drifts, electron and ion temperatures. There is a transition from ExB drift, indicated by a decrease in ion velocity in panel (a), to electron precipitation indicated by increased electron temperatures in panel (b). Substorm onset occurs at the transition time, around 20:02:30 UT.

  12. 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.

  13. 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

  14. Generation of BBFs and DFs, Formation of Substorm Auroras and Triggers of Substorm Onset

    NASA Astrophysics Data System (ADS)

    Song, Y.; Lysak, R. L.

    2014-12-01

    Substorm onset is a dynamical response of the MI coupling system to external solar wind driving conditions and to internal dynamical processes. During the growth phase, the solar wind energy and momentum are transferred into the magnetosphere via MHD mesoscale Alfvenic interactions throughout the magnetopause current sheet. A decrease in momentum transfer from the solar wind into the magnetosphere starts a preconditioning stage, and produces a strong earthward body force acting on the whole magnetotail within a short time period. The strong earthward force will cause localized transients in the tail, such as multiple BBFs, DFs, plasma bubbles, and excited MHD waves. On auroral flux tubes, FACs carried by Alfven waves are generated by Alfvenic interactions between tail earthward flows associated with BBFs/DFs/Bubbles and the ionospheric drag. Nonlinear Alfvenic interaction between the incident and reflected Alfven wave packets in the auroral acceleration region can produce localized parallel electric fields and substorm auroral arcs. During the preconditioning stage prior to substorm onset, the generation of parallel electric fields and auroral arcs can redistribute perpendicular mechanical and magnetic stresses, "decoupling" the magnetosphere from the ionosphere drag. This will enhance the tail earthward flows and rapidly build up stronger parallel electric fields in the auroral acceleration region, leading to a sudden and violent tail energy release and substorm auroral poleward expansion. We suggest that in preconditioning stage, the decrease in the solar wind momentum transfer is a necessary condition of the substorm onset. Additionally, "decoupling" the magnetosphere from ionosphere drag can trigger substorm expansion onset.

  15. Plasma sheet behavior during substorms

    SciTech Connect

    Hones, E.W. Jr.

    1983-01-01

    Auroral or magnetic substorms are periods of enhanced auroral and geomagnetic activity lasting one to a few hours that signify increased dissipation of energy from the magnetosphere to the earth. Data acquired during the past decade from satellites in the near-earth sector of the magnetotail have suggested that during a substorm part of the plasma sheet is severed from earth by magnetic reconnection, forming a plasmoid, i.e., a body of plasma and closed magnetic loops, that flows out of the tail into the solar wind, thus returning plasma and energy that have earlier been accumulated from the solar wind. Very recently this picture has been dramatically confirmed by observations, with the ISEE 3 spacecraft in the magnetotail 220 R/sub E/ from earth, of plasmoids passing that location in clear delayed response to substorms. It now appears that plasmoid release is a fundamental process whereby the magnetosphere gives up excess stored energy and plasma, much like comets are seen to do, and that the phenomena of the substorm seen at earth are a by-product of that fundamental process.

  16. Indications for ionospheric participation in the substorm process from AMPTE/CCE observations. [Charge Composition Explorer

    NASA Technical Reports Server (NTRS)

    Daglis, I. A.; Sarris, E. T.; Kremser, G.

    1990-01-01

    Observations with the AMPTE/CCE spacecraft in the near-earth nightside magnetosphere show a significant enhancement of ionospheric particle presence, mainly O(+), at the beginning of the substorm growth phase. Such an enhancement indicates not only an ionospheric participation in the substorm initiation, but also an active role in the substorm growth phase.

  17. 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.

  18. Substorm-induced energetic electron precipitation: Impact on atmospheric chemistry

    NASA Astrophysics Data System (ADS)

    Seppälä, A.; Clilverd, M. A.; Beharrell, M. J.; Rodger, C. J.; Verronen, P. T.; Andersson, M. E.; Newnham, D. A.

    2015-10-01

    Magnetospheric substorms drive energetic electron precipitation into the Earth's atmosphere. We use the output from a substorm model to describe electron precipitation forcing of the atmosphere during an active substorm period in April-May 2007. We provide the first estimate of substorm impact on the neutral composition of the polar middle atmosphere. Model simulations show that the enhanced ionization from a series of substorms leads to an estimated ozone loss of 5-50% in the mesospheric column depending on season. This is similar in scale to small to medium solar proton events (SPEs). This effect on polar ozone balance is potentially more important on long time scales (months to years) than the impulsive but sporadic (few SPE/year versus three to four substorms/day) effect of SPEs. Our results suggest that substorms should be considered an important source of energetic particle precipitation into the atmosphere and included in high-top chemistry-climate models.

  19. 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.

  20. Geomagnetic substorm association of plasmoids

    SciTech Connect

    Moldwin, M.B.; Hughes, W.J. )

    1993-01-01

    The relationship of geomagnetic substorms and plasmoids is examined by determining the correlation of the 366 plasmoids identified by Moldwin and Hughes (1992) with ground auroral zone magnetograms and geosynchronous particle data signatures of substorm onsets. Over 84% of the plasmoid events occurred between 5 and 60 min after a substorm onset. We also find near one-to-one correlation between large isolated substorm signatures in the near-Earth region and signatures consistent with a passing plasmoid in the distant tail (i.e., a traveling compression region, or an actual plasmoid observation). However, there does not appear to be an absolute correspondence of every substorm onset to a plasmoid signature in the deep tail especially, for periods of prolonged disturbance that have multiple substorm insets. A correlation of inter-planetary magnetic field B. south with plasmoid observations was also found. The locations of the near- and far-Earth reconnection sites are estimated using the time of flight of the plasmoids from substorm onset to their observation at ISEE 3. The estimates of the near- and far-Earth reconnection sites are highly variable and range from 10 to 140 RE, 32 refs., 4 figs. 2 tabs.

  1. A multisatellite study of a pseudo-substorm onset in the near-Earth magnetotail

    NASA Technical Reports Server (NTRS)

    Ohtani, S.; Anderson, B. J.; Sibeck, D. G.; Newell, P. T.; Zanetti, L. J.; Potemra, T. A.; Takahashi, K.; Lopez, R. E.; Angelopoulos, V.; Nakamura, R.

    1993-01-01

    This paper reports the multisatellite and ground observations of two pseudo-substorm onset events that occurred successively at 0747 UT and 0811 UT, May 30, 1985, with more attention to the 0747 UT onset. The distinguishing features of the 0747 UT event are as follows. (1) The substorm-associated tail reconfiguration started in a very localized region in the near-Earth magnetotail. (2) The magnitude of the current disruption decreased markedly as the disruption region expanded tailward. (3) On the ground the onset of a very small negative bay (approx. 40 nT) was observed simultaneously with the onset of the current disruption, but over a much wider local time sector than the near-Earth tail reconfiguration. Positive bay onsets at mid-latitudes also had a longitudinally wide distribution. From these features we infer than in the present event the current disruption took place filamentarily near AMPTE/CCE at approx. 8.8 R(sub E). It is also inferred that pseudo-substorm onsets are distinguished from standard substorm onsets by the absence of a global expansion of the current disruption, and that the spatial scales of the onset region in the magnetosphere is not a major difference between the two. The present study suggests that the spatial distribution of the magnetic distortion before onsets is an important factor to determine the expansion scale of the current disruption. It is also suggested that the current disruption is basically an internal process of the magnetosphere.

  2. Complexity and Turbulence at the Substorm Onset

    NASA Astrophysics Data System (ADS)

    Consolini, G.; De Marco, R.; Acquaviva, E.

    2014-12-01

    Geomagnetic substorms are one of the principal manifestations of the Earth's magnetospheric complex dynamics in response to solar wind changes. In the last two decades, in-situ susbtorm related studies showed that the onset of this phenomenon is accompanied by fluctuations covering a wide range of scales from the MHD domain to the small non-MHD one. Furthermore, these fluctuations have a turbulent, sporadic and intermittent character. This is particularly true for the well-known current disruption (CD) process, occurring at the substorm onset. Here, the features of the turbulence observed during a CD phenomenon are investigated, with a particular attention to the genereation of a 1/f spectrum in the MHD domain and its connection with a competing direct and inverse cascading process. A comparison with Hall-MHD shell-model simulations will be presented and discussed. This research has received funding from the European Community's Seventh Framework Programme ([FP7/2007-2013]) under Grant agreement no. 313038/STORM.

  3. 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.

  4. 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

  5. Theory for substorms triggered by sudden reductions in convection

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1996-01-01

    Many substorm expansions are triggered by interplanetary magnetic field changes that reduce magnetospheric convection. This suggests that expansion onsets are a result of a reduction in the large-scale electric field imparted to the magnetosphere from the solar wind. Such a reduction disrupts the inward motion and energization of plasma sheet particles that occur during the growth phase. It is proposed that the resulting magnetic drift of particles and a large dawn to dusk gradient in the ion energies leads to a longitudinally localized reduction in the plasma pressure, and thus, to the current wedge formation. This theory accounts for the rapid development of the expansion phase relative to growth phase, the magnitude of the wedge currents, the speeds of tailward and westward expansion of the current reduction region in the equatorial plane, and the speeds of the poleward and westward motion of active aurora in the ionosphere.

  6. Magnetospheric ULF waves with increasing amplitude related to solar wind dynamic pressure changes: The Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations

    NASA Astrophysics Data System (ADS)

    Shen, X. C.; Zong, Q.-G.; Shi, Q. Q.; Tian, A. M.; Sun, W. J.; Wang, Y. F.; Zhou, X. Z.; Fu, S. Y.; Hartinger, M. D.; Angelopoulos, V.

    2015-09-01

    Ultralow frequency (ULF) waves play an important role in transferring energy by buffeting the magnetosphere with solar wind pressure impulses. The amplitudes of magnetospheric ULF waves, which are induced by solar wind dynamic pressure enhancements or shocks, are thought to damp in one half a wave cycle or an entire wave cycle. We report in situ observations of solar wind dynamic pressure impulse-induced magnetospheric ULF waves with increasing amplitudes. We found six ULF wave events induced by solar wind dynamic pressure enhancements with slow but clear wave amplitude increase. During three or four wave cycles, the amplitudes of ion velocities and electric field of these waves increased continuously by 1.3-4.4 times. Two significant events were selected to further study the characteristics of these ULF waves. We found that the wave amplitude growth is mainly contributed by the toroidal mode wave. Three possible mechanisms of causing the wave amplitude increase are discussed. First, solar wind dynamic pressure perturbations, which are observed in a duration of 20-30 min, might transfer energy to the magnetospheric ULF waves continually. Second, the wave amplitude increase in the radial electric field may be caused by superposition of two wave modes, a standing wave excited by the solar wind dynamic impulse and a propagating compressional wave directly induced by solar wind oscillations. When superposed, the two wave modes fit observations as does a calculation that superposes electric fields from two wave sources. Third, the normal of the solar wind discontinuity is at an angle to the Sun-Earth line. Thus, the discontinuity will affect the dayside magnetopause continuously for a long time.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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

  12. Rice Convection Model Simulation of Injection of an Observed Plasma Bubble Into the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Wolf, R. A.; Zhang, J.; Erickson, G. M.; Toffoletto, F. R.; Yang, J.

    2008-12-01

    An RCM simulation has been carried out for the growth and early expansion phase of a substorm that occurred on July 22, 1998. This is the first substorm simulation for which the RCM boundary conditions and the inputted magnetic field model have been carefully tailored for consistency with measurements made in the inner plasma sheet during the event (Geotail near X=-9, Y=0 in GSM coordinates). The simulation focuses on the injection into the inner magnetosphere of a bubble (region with low specific entropy) that was observed by Geotail. Potential and inductive contributions to the magnetospheric electric field are both important, and their patterns are compared and discussed. One preliminary conclusion from the simulation is that the bubble drifts in a channel that narrows as it approaches the inner magnetosphere, which results in a plasma-sheet inner edge that resembles the injection boundary proposed many years ago by Carl McIlwain. The corresponding distinctive pattern in the auroral electric field is compared with published substorm observations. The model also predicts a distinctive substorm-onset-associated prompt-penetration electric field in the low- and mid-latitude ionosphere.

  13. Ionospheric irregularities during a substorm event: Observations of ULF pulsations and GPS scintillations

    NASA Astrophysics Data System (ADS)

    Kim, H.; Clauer, C. R.; Deshpande, K.; Lessard, M. R.; Weatherwax, A. T.; Bust, G. S.; Crowley, G.; Humphreys, T. E.

    2014-07-01

    Plasma instability in the ionosphere is often observed as disturbances and distortions of the amplitude and phase of the radio signals, which are known as ionospheric scintillations. High-latitude ionospheric plasma, closely connected to the solar wind and magnetospheric dynamics, produces very dynamic and short-lived Global Positioning System (GPS) scintillations, making it challenging to characterize them. It is observed that scintillations in the high-latitude ionosphere occur frequently during geomagnetic storms and substorms. In addition, it is well known that Ultra Low Frequency (ULF) pulsations (Pi2 and Pi1B) are closely associated with substorm activity. This study reports simultaneous observations of Pi2 and Pi1B pulsations and GPS phase scintillations during a substorm using a newly designed Autonomous Adaptive Low-Power Instrument Platform (AAL-PIP) installed at the South Pole. The magnetic field and GPS data from the instruments appear to be associated in terms of their temporal and spectral features. Moreover, the scintillation events were observed near the auroral latitudes where Pi1B pulsations are commonly detected. The temporal, spectral and spatial association between the scintillation and geomagnetic pulsation events suggests that the magnetic field perturbations and enhanced electric fields caused by substorm currents could contribute to the creation of plasma instability in the high-latitude ionosphere, leading to GPS scintillations.

  14. The magnetotail and substorms. [magnetic flux transport model

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Mcpherron, R. L.

    1973-01-01

    The tail plays a very active and important role in substorms. Magmetic flux eroded from the dayside magnetosphere is stored here. As more and more flux is transported to the magnetotail and stored, the boundary flares more, the field strength in the tail increases, and the currents strengthen and move closer to the earth. Further, the plasma sheet thins and the magnetic flux crossing the neutral sheet lessens. The experimental evidence for these processes is discussed and a phenomenological or qualitative model of the substorm sequence is presented. In this model, the flux transport is driven by the merging of the magnetospheric and interplanetary magnetic fields. During the growth phase of substorms the merging rate on the dayside magnetosphere exceeds the reconnection rate in the neutral sheet.

  15. 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.

  16. 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.

  17. Prescribing the Kp, AE and Dst Response Using the Magnetospheric State Technique

    NASA Astrophysics Data System (ADS)

    Fung, S. F.; Van Artsdalen, K. J.; Shao, X.

    2014-12-01

    The magnetosphere exhibits a variety of geomagnetic activities in response to different solar wind and interplanetary magnetic field (IMF) input. Global-scale geomagnetic activities, such as those due to substorms and storms, are reflected in the Kp, AE and Dst indices, which are constructed from ground-based magnetometer observations. Understanding how and the conditions under which a geomagnetic storm or substorm occurs are outstanding questions in heliophysics and space weather predication. While it is generally accepted that Earth-directed coronal mass ejections from the sun can cause geomagnetic storms and substorms in the magnetosphere, the specific necessary and sufficient conditions, in terms of both the solar wind drivers and pre-existing magnetospheric conditions, for triggering different types of geomagnetic activities are yet to be delineated. For example, while it is generally thought that geomagnetic storms can be triggered by extended intervals of southward IMF Bz, it is still not clear how and at what point during the southward-IMF Bz interval a storm will arise, and how the storm-triggering process may be affected by the pre-existing state of the magnetosphere. To address these specific questions, we have applied the magnetospheric state prescription technique developed by Fung and Shao [2008]. We have used solar wind and geomagnetic indices data taken in 1970-2009 to constructed a magnetospheric state lookup table and applied the table to perform out-of-sample predictions or prescriptions of the Kp, AE and Dst indices during different geomagnetic storm intervals (with minimum Dst ≤ -100 nT) that occurred after 2009. Our presentation will discuss the validity of the magnetospheric state prescription technique and the role of different magnetopsheric state parameters in prescribing geomagnetic storm development. Fung, S. F. and X. Shao, Specification of multiple geomagnetic responses to variable solar wind and IMF input, Ann. Geophys., 26, 639

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Latitudinal Changes of Polar Hiss and Plasmapause Hiss Associated with Magnetospheric Processes

    NASA Astrophysics Data System (ADS)

    Ondoh, T.

    Latitudinal variations of magnetospheric VLF hiss observed at low altitudes reflect dynamical changes of the magnetosphere, since VLF hiss signals at low altitudes are integrated signals of the whistler-mode VLF hiss propagating along geomagnetic field lines from wide-altitude sources in the magnetosphere. Analysis of narrow-band intensity data of ISIS-2 (1400 km) VLF electric field (50 Hz-30 kHz) shows that the broad-band polar hiss occurs at invariant latitudes for 68-85 degrees and the narrow-band plasmapause hiss occurs fro 50-64 degrees in geomagnetic quiet periods, and that the polar hiss region shifts to lower latitudes or inner L-shells and finally joins to the plasmapause hiss region as the substorm develops. The polar hiss is interpreted as the whistler-mode Cerenkov radiations from inverted-V electrons precipitating from the plasmasheet boundary layer and the plasmapause hiss is the whistler-mode emissions due to the electron cyclotron instability around the equatorial plasmapause. The substorm changes of polar hiss and plasmapause hiss regions observed at low altitudes are studied in relation to dynamical changes of inward shift of the plasmasheet horns and of the plasmaspheric plumes as observed by the IMAGE in substorm periods.

  3. 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.

  4. The solar wind-magnetosphere energy coupling and magnetospheric disturbances

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.

    1980-01-01

    Energy coupling between the solar wind and the magnetosphere is examined and the influence of this coupling on magnetospheric disturbances is discussed. Following a review of the components of the total energy production rate of the magnetosphere and progress in the study of solar wind-magnetosphere correlations, the derivation of the solar wind-magnetosphere energy coupling function, which has been found to correlate well with the total magnetospheric energy production rate, is presented. Examination of the relations between the energy coupling function and the type of magnetic disturbance with which it is associated indicates that magnetic storms with a large sudden storm commencement and a weak main phase are associated with small energy coupling, while values of the coupling function greater than 5 x 10 to the 18th to 10 to the 19th erg/sec are required for the development of a major geomagnetic storm. The magnetospheric substorm is shown to be a direct result of increased solar wind-magnetosphere energy coupling rather than the sudden conversion of stored magnetic energy. Finally, it is indicated that at energy couplings greater than 10 to the 19th erg/sec, the positive feedback process responsible for substorms breaks down, resulting in the abnormal growth of the ring current.

  5. 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.

  6. From discovery to prediction of magnetospheric processes

    NASA Astrophysics Data System (ADS)

    Kamide, Y.

    2000-11-01

    Over the last 50 years magnetospheric research has transferred its focus from geomagnetism to space physics, or from inferring the intensity of extraterrestrial currents, through discoveries of the main plasma regions in the magnetosphere, to predicting the processes occurring in the entire solar wind-magnetosphere-ionosphere system. Relating advances in magnetospheric physics to the framework of substorm research, this review paper demonstrates that the ``recent'' space age since 1960s consisted of /(1) an exploratory//discovery phase in which the magnetotail, the plasma sheet, and the acceleration region of auroral particles were identified, and /(2) a phase of comprehensive understanding in which we have attempted to comprehend the nature and significance of the near-Earth space environment. This progress in solar-terrestrial physics has coincided with a number of new discoveries of solar and interplanetary phenomena such as magnetic clouds, coronal mass ejections and coronal holes. Computer simulation techniques have been developed to the degree that satellite observations from a very limited number of points can be used to trace and reproduce the main energy processes. We are now entering a new phase in which we hope to be able to predict the dynamic processes that take place in the solar-terrestrial environment.

  7. Mapping ionospheric convection patterns to the magnetosphere

    NASA Astrophysics Data System (ADS)

    Maynard, Nelson C.; Denig, William F.; Burke, William J.

    1995-02-01

    While convection patterns in the high-latitude ionosphere are usually presented in a corotating frame of reference, those of the magnetosphere are given in inertial coordinates. In the corotating representation the convection throat, which is frequently associated with the cusp, opens between 1000 and 1100 MLT. Cusp precipitation, however, centers about noon. We find that transforming the convection patterns of Heppner and Maynard (1987) (hereinafter H-M) into inertial coordinates aligns the throat region with local noon. We present projections of the H-M patterns to the magnetosphere in both corotating and inertial coordinates using the magnetic field model of Tsyganenko (1989). In inertial coordinates the mapped H-M convection throat opens at noon. Consistent with predictions of the Rice convection model for magnetospheric electric fields late in the substorm cycle, only a small fraction of the equipotential contours penetrate to the subsolar region. This suggests that a significant portion of flux tube merging occurs on magnetic field lines whose equatorial mapping is on the flanks of the magnetosphere. Nonconjugacy between the mapping of H-M patterns for both positive and negative interplanetary magnetic field B(sub Y), especially in the 1400-1600 LT sector, may explain the B(sub Y) dependence of the electron precipitation 'hot spot' discovered by Evans (1985). A separate lobe cell is not required to explain the central, equipotential contours of the large convection cell.

  8. 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.

  9. 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.

  10. Relativistic electrons near geostationary orbit: Evidence for internal magnetospheric acceleration

    SciTech Connect

    Baker, D. N.; Blake, J. B.; Callis, L. B.; Belian, R. D.; Cayton, T. E.

    1989-06-01

    At times, relativistic electron fluxes in Earth's outer magnetosphere are not obviously related to an external (Jovian or solar) source. This finding suggests that an internal magnetospheric acceleration mechanism may operate under some circumstances. A possible mechanism identified for Jupiter's magnetosphere could also be considered in the terrestrial case. Such a model requires the substorm- generation of a spectrally-soft electron component with subsequent inward radial diffusion (violating the third adiabatic invariant). A large electron energy gain transverse to the magnetic field occurs in this process. Eventually, deep within the magnetosphere, substantial pitch angle scattering occurs violating all adiabatic invariants. Then, at low L-values, there occurs an energy-preserving outward transport of energetic electrons near the mirror points. This leads to a return of the accelerated population to the outer magnetosphere. Such low-altitude processes should result in ''conic'' or ''butterfly'' pitch angle distributions at very high energies as the electrons execute trans-L diffusion at the mirror altitudes and then are magnetically focussed near the equator. Data collected concurrently at geostationary orbit at three widely-spaced local times during a relativisic electron event show a butterfly pitch angle distribution, while lower energy electrons simultaneously show pancake-like distributions. The butterfly pitch angle distributions appear in /similar to/25% of the examined relativistic electron events, thereby providing support for acceleration by a recirculation process. /copyright/ American Geophysical Union 1989

  11. 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.

  12. Dynamical effects of geomagnetic storms and substorms in the middle-latitude ionosphere: An observational campaign

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing; Mendillo, Michael; Hughes, W. Jeffrey; Buonsanto, Michael J.; Sipler, Dwight P.; Kelly, John; Zhou, Qihou; Lu, Gang; Hughes, Terrence J.

    2000-04-01

    An observational campaign was conducted in October 1992 for ~36 hours, at three high- to low-latitude sites near 75°W longitude (Sondre Stromfjord, Millstone Hill, and Arecibo). Vector plasma drift velocities are obtained using the incoherent scatter radar technique at each site. Neutral winds were measured using a Fabry-Perot interferometer, and 6300 Å airglow structures were imaged at the midlatitude site. Electric fields and meridional winds for the period were perturbed when magnetic storms and substorms occurred on the day and night of the campaign. The penetration of magnetospheric electric field and the following interplays between ionospheric electrodynamics and thermospheric wind perturbations in the midlatitude ionosphere are assessed using the multidiagnostic measurements. Evidence for traveling atmospheric disturbances (TADs) and large-scale gravity waves induced by auroral heating effects upon the thermosphere is identified. Diffuse aurora and a stable aurora red (SAR) arc were observed from Millstone Hill during the night of the campaign. The SAR arc moved southward when there were westward electric field perturbations, indicating plasmasphere compression in the postmidnight sector under substorm conditions. The SAR arc location was used to infer the motion of the magnetospheric shielding layer past the Millstone Hill site. Ionospheric F region disturbances in hmF2, NmF2, and total electron content were driven by the observed dynamics, exhibiting a complex mix of wind and electric field perturbations. While standard model episodes of penetration and shielding/overshielding occurred during the daytime event, such unambiguous clarifications were far less obvious during the nighttime event. This is perhaps due to the prolonged period of moderate geomagnetic activity that served as the background conditions for the substorms that occurred during the campaign.

  13. 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

  14. Impulse Travel Time from the Magnetotail to the Aurora Region during substorm: OpenGGCM Simulation

    NASA Astrophysics Data System (ADS)

    Ferdousi, Banafsheh; Raeder, Jimmy

    2016-07-01

    The onset of substorms is an unsolved problem in Space Physics although there are many models explaining the substorm process. Studying the processes that occur during first 2 minutes of substorm depends critically on the correct timing between different signals in the plasma sheet and the ionosphere. This has been difficult to accomplish with data alone, since signals are sometimes ambiguous, or they have not been observed in the right locations. To investigate signal propagation paths and signal travel times, we use Magnetohydrodynamic global simulations of the Earth magnetosphere: OpenGGCM. The waves are created at different locations in the magnetotail by perturbing plasma pressure in the plasma sheet. Thus, we can study wave path in the magnetotail and determine its travel time to the ionosphere. Contrary to previous studies, we find that wave travel reach the ionosphere from the midtail around 60 seconds. We also find that waves travel faster through the lobes, and the Tamao path is not generally the preferred path for waves originating in the plasma sheet. Furthermore, we find that the impulses that are generated closer to earth lead to dispersed ionosphere signatures, whereas the impulses originated in midtail region lead to more localized signatures.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  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. 2-D Convection and Electrodynamic Features of Substorms Revealed by Multiple Radar Observations (Invited)

    NASA Astrophysics Data System (ADS)

    Zou, S.

    2010-12-01

    Substorms are one of the fundamental elements of geomagnetic activity, which involve complex magnetosphere-ionosphere coupling processes. In this work, we aim to better understand the evolution of high latitude ionospheric convection and the relevant current systems associated with substorms, with emphasis on these features near the nightside Harang reversal region. Three different types of radars, including the Super Dual Auroral Radar Network (SuperDARN) coherent-scatter radars, the new advanced modular incoherent-scatter radar at Poker Flat (PFISR), and the Sondrestrom ISR, have been utilized. Observations from these radars, together with those from complementary instruments, including satellites and other ground-based instruments, have enabled fundamental new understanding of the ionospheric electrodynamic properties associated with substorms. In this presentation, I focus on electrodynamics near the nightside Harang reversal region. Observations from the SuperDARN and the PFISR radars revealed that auroral activity at substorm onset is located near the center of the Harang reversal, which represents a key feature of magnetospheric and ionospheric convection and is part of the Region 2 system. The observations also show nightside convection flows exhibit repeatable, distinct variations at different locations relative to the substorm-related auroral activity. Taking advantage of the simultaneous flow and ionization measurements from PFISR, a current closure relation has been found between the Region 2 and the substorm field-aligned current systems. By synthesizing these observations, a 2-D comprehensive view of the nightside ionospheric electrodynamical features, including electrical equipotentials, flows and FACs, and their evolution associated with substorms has been constructed, which has revealed a strong coupling between the substorm and the Region 2 current systems. This study sheds new light on substorm-related magnetosphere-ionosphere coupling and

  1. ULF Waves and Magnetic Substorms: Their Onset and Excitation Mechanism

    NASA Astrophysics Data System (ADS)

    Murphy, Kyle; Milling, David; Rae, Jonathan; Mann, Ian; Russell, Christopher; Angelopoulos, V.; Glassmeier, K.-H.; Auster, Uli; McFadden, James; Larson, Davin

    Impulsive Ultra-Low Frequency (ULF) waves known as Pi1s (1-40s period) and Pi2s (40-150s period) are predominantly observed during substorm onset. Primarily due a lack of high-fidelity and conjugate in-situ and ground-based observations, determining the excitation mechanism for these ULF waves and their role in magnetic substorms has proved to be challenging. However, with new multi-point magnetotail observations provided by the 5 THEMIS probes and expanded ground-based coverage, the potential now exists to unambiguously characterise the ULF phenomena observed at substorm onset. Utilising favourable conjunctions of the tailaligned THEMIS probes, and the THEMIS and CARISMA ground-based magnetometers, we determine a probable ionospheric location of substorm onset, and characterise the associated ULF wave phenomena. Utilising wavelets, we determine the onset and time of arrival of the ionospheric Pi1s and Pi2s, and compare these observations to the in-situ signatures at the THEMIS probes, developing a causal timeline of substorm expansion. The onset of the ULF pulsations on the ground can then be compared to a MHD time-of-flight simulation to constrain the onset region in space. Recent work has suggested that impulsive Pi2 waveforms are directly-driven by plasma flows emanating from the substorm onset location in the magnetotail. Other studies suggest these waves are a natural oscillatory mode of the magnetosphere, resulting in a field line resonance or inner magnetospheric cavity mode. In several case studies we consider each possibility and examine the most likely excitation mechanism for impulsive Pi1 and Pi2 ULF waves observed during magnetic substorm onset on the ground and in space.

  2. 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

  3. 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.

  4. 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.

  5. Spontaneous and trigger-associated substorms compared: Electrodynamic parameters in the polar ionosphere

    NASA Astrophysics Data System (ADS)

    Liu, Jun-Ming; Zhang, Bei-Chen; Kamide, Y.; Wu, Zhen-Sen; Hu, Ze-Jun; Yang, Hui-Gen

    2011-01-01

    An attempt is made to study the difference, if any, between the response of the polar ionosphere to spontaneous substorms and that to trigger-associated substorms in terms of electrodynamic parameters including ionospheric current vectors, the electric potential, and the current function. The results show that, in the first approximation, the ionospheric parameters for the two types of substorms are quite similar. It is therefore conceived that spontaneous substorms are not very different from trigger-associated substorms in the development of substorm processes in the magnetosphere-ionosphere system. We demonstrate, however, that spontaneous substorms seem to have a more clearly identifiable growth phase, whereas trigger-associated substorms have a more powerful unloading process. Changes in the current intensity and the electric potential drop across the polar cap in the recovery phase are also quite different from each other. Both the current intensity and the cross-polar cap potential drop show a larger decrease in the recovery phase of trigger-associated substorms, but the potential drop decreases only slightly and the currents in the late morning sector are still strong for spontaneous substorms. We interpret these findings as an indication of the relative importance of the unloading process and the directly driven process in conjunction with the north-south polarity of the interplanetary magnetic field. There still exists a strong directly driven process in the recovery phase of spontaneous substorms. For trigger-associated substorms, however, both the directly driven process and the unloading process become weak after the peak time.

  6. 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

  7. 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

  8. Evolution of high latitude ionospheric convection associated with substorms: Multiple radar observations

    NASA Astrophysics Data System (ADS)

    Zou, Shasha

    The work presented in this dissertation concerns evolution of the high latitude ionospheric convection and the relevant current systems associated with substorms, with emphasize on these features near the nightside Harang reversal region. Three different types of radars, including the Super Dual Auroral Radar Network (SuperDARN) coherent-scatter radars, the new advanced modular incoherent-scatter radar at Poker Flat (PFISR), and the Sondrestrom incoherent-scatter radar (ISR), have been utilized. Observations from those radars, together with those from complementary instruments, including satellites and other ground-based instruments, have revealed fundamental new understand of the ionospheric electrodynamic properties associated with substorms. By using the SuperDARN and the PFISR radars, we found that the auroral activity at substorm onset is located in the center of the Harang reversal, which represents a key region in the magnetospheric and ionospheric convection and is part of the Region 2 system. We have also shown that nightside convection flows exhibit repeatable, distinct variations at different locations relative to the substorm-related auroral activity. Taking advantage of the simultaneous flow and ionization measurements from PFISR, a current closure relation has been found between the Region 2 and the substorm field-aligned current systems. These observations demonstrate a strong coupling between the Region 2 system and the substorm dynamics. This study sheds new light on the substorm-related magnetosphere-ionosphere coupling and contributes to the building of a holistic picture of the substorm dynamics. The third radar has been used to study the dayside ionospheric convection response to the external soar wind and IMF driving and its role in substorm dynamics. The results have been applied to study substorm triggering and in the future could be used to study the relation between the external driving and the formation of the Harang reversal.

  9. 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.

  10. 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.

  11. 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.

  12. Dynamics of Mars' magnetosphere

    NASA Astrophysics Data System (ADS)

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

    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 shear 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.

  13. The effect of magnetic substorms on near-ground atmospheric current

    NASA Astrophysics Data System (ADS)

    Belova, E.; Kirkwood, S.; Tammet, H.

    2000-12-01

    Ionosphere-magnetosphere disturbances at high latitudes, e.g. magnetic substorms, are accompanied by energetic particle precipitation and strong variations of the ionospheric electric fields and currents. These might reasonably be expected to modify the local atmospheric electric circuit. We have analysed air-earth vertical currents (AECs) measured by a long wire antenna at Esrange, northern Sweden during 35 geomagnetic substorms. Using superposed epoch analysis we compare the air-earth current variations during the 3 h before and after the time of the magnetic X-component minimum with those for corresponding local times on 35 days without substorms. After elimination of the average daily variation we can conclude that the effect of substorms on AEC is small but distinguishable. It is speculated that the AEC increases observed during about 2 h prior to the geomagnetic X-component minimum, are due to enhancement of the ionospheric electric field. During the subsequent 2 h of the substorm recovery phase, the difference between substorm and quiet atmospheric currents decreases. The amplitude of this substorm variation of AEC is estimated to be less than 50% of the amplitude of the diurnal variation in AEC during the same time interval. The statistical significance of this result was confirmed using the Van der Waerden X-test. This method was further used to show that the average air-earth current and its fluctuations increase during late expansion and early recovery phases of substorms.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Substorm Timing and Location Using The Combined CARISMA and THEMIS GMAG Magnetometers

    NASA Astrophysics Data System (ADS)

    Rae, I. J.; Milling, D. K.; Mann, I. R.; Murphy, K. R.; Glassmeier, K.; Auster, U.; Angelopoulos, V.; Russell, C. T.

    2007-12-01

    With the successful launch of the THEMIS spacecraft, the expansion of the CARISMA magnetometer array, and the deployment of the THEMIS GBOs, there now exists an exceptional opportunity to study fundamental ULF wave science in the nightside magnetosphere around substorm onset. Traditionally, substorm onset is usually determined by location and timing of ULF waves in the Pi2 (40-200 second period) range. With the current configuration of ground magnetometers, it is now possible to resolve frequencies in the Pi1 (1-40 second period) band using novel techniques such as Wavelet Analysis. With this technique, the entire spectrum of ULF waves associated with substorm onset can be accurately timed to approximately half of the wave period. We use a substorm location modeling algorithm [Cramoysan et al., 1995] to produce initial estimates of the locations of the upward and downward field aligned currents and the westward electrojet. We present results from several isolated substorms and find that the onset location of the Pi1 waves starts at or close to the location of the downward field-aligned current region and propagate isotropically away from this location. We discuss the implications of this result in terms of potential generation mechanisms for Pi1 waves at substorm onset, and for the physical processes operating at the onset of the substorm expansion phase.

  1. From Space Weather Toward Space Climate Time Scales: Substorm Analysis from 1993 to 2008

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    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 (R(sub ss)), substorm 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 substorms during the declining solar cycle phase (absolute value of A(sub ss,decl)) - 500 nT) were 25% larger than the spring substorms during the ascending solar cycle years ((absolute value of A(sub ss,asc) = 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-Io-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. M-I coupling across the auroral oval at dusk and midnight: repetitive substorm activity driven by interplanetary coronal mass ejections (CMEs)

    NASA Astrophysics Data System (ADS)

    Sandholt, P. E.; Farrugia, C. J.; Denig, W. F.

    2014-04-01

    We study substorms from two perspectives, i.e., magnetosphere-ionosphere coupling across the auroral oval at dusk and at midnight magnetic local times. By this approach we monitor the activations/expansions of basic elements of the substorm current system (Bostrøm type I centered at midnight and Bostrøm type II maximizing at dawn and dusk) during the evolution of the substorm activity. Emphasis is placed on the R1 and R2 types of field-aligned current (FAC) coupling across the Harang reversal at dusk. We distinguish between two distinct activity levels in the substorm expansion phase, i.e., an initial transient phase and a persistent phase. These activities/phases are discussed in relation to polar cap convection which is continuously monitored by the polar cap north (PCN) index. The substorm activity we selected occurred during a long interval of continuously strong solar wind forcing at the interplanetary coronal mass ejection passage on 18 August 2003. The advantage of our scientific approach lies in the combination of (i) continuous ground observations of the ionospheric signatures within wide latitude ranges across the auroral oval at dusk and midnight by meridian chain magnetometer data, (ii) "snapshot" satellite (DMSP F13) observations of FAC/precipitation/ion drift profiles, and (iii) observations of current disruption/near-Earth magnetic field dipolarizations at geostationary altitude. Under the prevailing fortunate circumstances we are able to discriminate between the roles of the dayside and nightside sources of polar cap convection. For the nightside source we distinguish between the roles of inductive and potential electric fields in the two substages of the substorm expansion phase. According to our estimates the observed dipolarization rate (δ Bz/δt) and the inferred large spatial scales (in radial and azimuthal dimensions) of the dipolarization process in these strong substorm expansions may lead to 50-100 kV enhancements of the cross

  3. Direct impact of substorm on outer radiation belt

    NASA Astrophysics Data System (ADS)

    Ebihara, Y.; Tanaka, T.

    2012-12-01

    According to Akebono satellite observations, substorms may have a direct impact on relativistic electrons in the heart of the outer radiation belt, but its underlying mechanism remains unsolved. The difficulties arise from uncertainty in identifying and modeling the electric field associated with substorms. We solved a set of 4-D drift kinetic equations for trapped electrons in the inner magnetosphere (L<7.4) under the electric and magnetic fields provided by a global magnetohydrodynamics (MHD) simulation. We found that relativistic electrons are effectively redistributed by two types of electric fields that are self-consistently induced. The first is a large-amplitude, highly fluctuating electric field (type-1 electric field) caused by imbalance between the JxB force and the grad-P force. The other is a large-amplitude, fairly stable electric field (type-2 electric field) associated with a localized flow propagating earthward. The relativistic electrons are effectively transported inward by the type-2 electric field because it persists for several drift periods of the relativistic electrons. The transport process appears to be different from radial diffusion because its direction is primarily earthward. Our simulations suggest that the force-induced processes, which are self-consistently coupled to the electromagnetic processes, play an essential role in the substorm-associated redistribution of particles in the inner magnetosphere.

  4. In-situ measurement of the substorm onset instability

    NASA Astrophysics Data System (ADS)

    Murphy, K. R.; Rae, J.; Watt, C.; Forsyth, C.; Mann, I. R.; Yao, Z.; Kalmoni, N.

    2015-12-01

    The substorm 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 magnetosphere 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 substorms, we focus here on observations of the unmistakeable signs of a plasma instability acting at substorm 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 substorm 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.

  5. Simulations of Steady Magnetospheric Convection

    NASA Astrophysics Data System (ADS)

    Lemon, C.; Toffoletto, F.; Sazykin, S.; Wolf, R.

    2003-12-01

    Steady Magnetospheric Convection in the Earth's magnetosphere is typically defined as a period of several hours of enhanced solar wind driving of the magnetosphere (i.e. the Interplanetary Magnetic Field is southward) during which the magnetosphere is nonetheless devoid of substorm signatures. We present and discuss model results of generic Steady Magnetospheric Convection (SMC) events using the Self-consistent Rice Convection Model. The SRCM consists of two coupled models that are used to separately compute the plasma and magnetic field evolution. The Rice Convection Model (RCM) is a multi-fluid guiding-center plasma drift code used to simulate plasma dynamics under the assumption that convection can be modeled quasi-statically as a sequence of force-balanced states. The RCM has been coupled to an equilibrium solver that computes a magnetic field that is in force-balance (and is therefore self-consistent) with the RCM's plasma distribution. Various levels of steady external driving conditions are imposed in order to contrast the ability of the model magnetosphere to respond to differing rates of energy input and form a steady-state convection pattern. Model results will be compared with empirical SMC morphology.

  6. Nuclear burst plasma injection into the magnetosphere and resulting spacecraft charging

    NASA Technical Reports Server (NTRS)

    Pavel, A. L.; Cipolla, J. A.; Silevitch, M. B.; Golden, K. I.

    1977-01-01

    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 occur in the loss cone exits of the nuclear debris bubble, and the accelerated ambient ions will freestream along the magnetic field lines into the magnetosphere. 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 magnetospheric substorms. 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.

  7. Substorm development and ballooning mode signatures at GEOS--2/SCATHA

    NASA Astrophysics Data System (ADS)

    Holter, O.; Galopeau, P.; Roux, A.; Perraut, S.; Pedersen, A.; Korth, A.

    2003-04-01

    The substorm event considered here was recorded on May 22, 1979 at GEOS--2 and SCATHA when the two s/c were separated by less than 30 minutes in local time. The dipolarization onset associated with the substorm occurred within a time interval of less than one minute at the two s/c when they were located around 2100 LT. GEOS--2 was situated close to the magnetic equatorial surface, while SCATHA was presumably close to the current sheet boundary. The observed delay of the magnetic field dipolarization onset and the injection of electrons and ions for the two s/c indicated a westward expansion of the substorm with an angular velocity ˜ 7.7^o/s. At substorm onset, a strong azimuthal magnetic field component(˜ 50 nT) of finite duration (2--3 min) was recorded on SCATHA, indicating strong field aligned Birkeland currents below the magnetic equator. We have related the observed magnetic field component variations during the substorm to the field aligned current as indicated by the azimuthal magnetic field component. The first sign of an approaching substorm was an initial two minute tailward stretching of the magnetic field. Concurrent with the initial stretching was a reduction of the electron flux intensity. The electron injection started simultaneous with the dipolarization process. The measured field and particle fluxes are related to signatures suggested by a simple Rayleigh--Taylor drift ballooning instability model.

  8. Occurrency frequency of substorm field and plasma signatures observed near-earth by ISEE-1/2

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    The onset of the majority of substorms occurs when the tail field stops growing more tail-like and begins to become more dipolar. This corresponds to the onset signatures on the ground and in geosynchronous orbit. The AE indices and the IGS Pi 2 data were used to determine the major substorm onsets of 1978 and 1979. The time delay between successive substorms, the distribution of the substorm growth phase duration and the probability of tailward flows were determined as a function of spacecraft location. About a half of the substorms exhibit a plasma signature including earthward or tailward flows or plasma sheet drop out and recovery. Earthward flows are often seen at substorm onset, and almost always during substorm recovery. Tailward flows are occasionally seen at onset as the spacecraft is close enough to the neutral sheet. The experimental results are compared to predictions based on the neutral line and current sheet disruption models.

  9. Time development of high-altitude auroral acceleration region plasma, potentials, and field-aligned current systems observed by Cluster during a substorm

    NASA Astrophysics Data System (ADS)

    Hull, A. J.; Chaston, C. C.; Fillingim, M. O.; Mozer, F.; Frey, H. U.

    2013-12-01

    The auroral acceleration region is an integral link in the chain of events that transpire during substorms, 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 substorm 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 occur during substorms 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 substorm. Of particular emphasis is on the time-development of the plasma, potentials and currents that occur therein with the aim of ascertaining high-altitude drivers of substorm 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 magnetospheric 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

  10. MESSENGER: Exploring Mercury's Magnetosphere

    NASA Technical Reports Server (NTRS)

    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.

    2005-01-01

    The MESSENGER mission to Mercury offers our first opportunity to explore this planet s miniature magnetosphere since the brief flybys of Mariner 10. Mercury s magnetosphere is unique in many respects. The magnetosphere 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 magnetosphere 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 magnetosphere 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, substorm-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 magnetosphere 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, magnetosphere, and regolith. The electrodynamics of Mercury s magnetosphere 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

  11. MESSENGER: Exploring Mercury's Magnetosphere

    NASA Astrophysics Data System (ADS)

    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.

    2007-08-01

    The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury offers our first opportunity to explore this planet’s miniature magnetosphere since the brief flybys of Mariner 10. Mercury’s magnetosphere is unique in many respects. The magnetosphere 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 magnetosphere, 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 magnetosphere 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, substorm-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 magnetosphere 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, magnetosphere, and regolith. The electrodynamics of Mercury’s magnetosphere 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

  12. Flow Pattern relative to the Substorm Current Wedge

    NASA Astrophysics Data System (ADS)

    Chu, X.; McPherron, R. L.; Hsu, T.

    2013-12-01

    Magnetospheric substorms play a key role in the coupling of the solar wind and the magnetosphere. The Substorm Current Wedge (SCW) is a key element in the present physical model of substorms. 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 substorm 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.

  13. Statistical survey on sawtooth events, SMCs and isolated substorms

    NASA Astrophysics Data System (ADS)

    Partamies, N.; Pulkkinen, T. I.; McPherron, R. L.; McWilliams, K.; Bryant, C. R.; Tanskanen, E.; Singer, H. J.; Reeves, G. D.; Thomsen, M. F.

    2009-08-01

    Solar wind driving can cause a variety of different responses in the magnetosphere. Strong and steady driving during geomagnetic storms may result in sawtooth events. Strong to moderate driving may be followed by either sawtooth events or steady magnetospheric convection (SMC) events. Lower solar wind energy input typically leads to the formation of isolated non-storm substorms. This study uses superposed epoch analysis to reveal the typical properties of these three event groups as well as their similarities and differences. We use IMF and solar wind parameters, as well as ground-based indices (AL, SYM-H, ASY-H, PCN) to examine the level of solar wind driving and its response in the magnetosphere. Our results show that sawtooth events are associated with the strongest ionospheric activity. The subgroups of events during constant solar wind EY show that the key difference between the events is the average solar wind speed. Particularly, the high activity during sawtooth events is driven by high solar wind speed, while the lowest average speed during the SMCs may explain the lack of substorm activity during the steady convection periods.

  14. Response of plasmaspheric configuration to substorms revealed by Chang’e 3

    PubMed Central

    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

    2016-01-01

    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 magnetosphere, and the configuration of the plasmasphere is sensitive to magnetospheric activity (storms and substorms). However, the response of the plasmaspheric configuration to substorms 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 substorms, which implies a causal relationship between the substorms and the formation of the three bulges on the plasmasphere. Instead of leading to plasmaspheric erosion as geomagnetic storms do, substorms initiated on the nightside of the Earth cause local inflation of the plasmasphere in the midnight region. PMID:27576944

  15. Probing the first few minutes of substorm expansion phase onset using ULF wave techniques

    NASA Astrophysics Data System (ADS)

    Rae, Jonathan; Mann, Ian; Milling, David; Murphy, Kyle; Angelopoulos, V.; Frey, Harald; Russell, Christopher; Glassmeier, Karl-Heinz; Auster, Uli; Mende, Stephen

    With the successful launch of the THEMIS spacecraft, the expansion of the CARISMA magnetometer array, and the deployment of the THEMIS GBOs, there exist exceptional opportunities to study the initiation of ULF waves surrounding substorm onset during the first THEMIS tail season. In this talk, we outline a number of techniques with which to diagnose the nightside magnetosphere around expansion phase onset. We use ULF pulsations to determine magnetospheric characteristics using both Pi2 (40-150s period) and long-period Pi1 (1-40s period) waveforms and investigate their relationship to substorm expansion phase onset. We present case studies whereby a ULF wave detection algorithm based upon a discrete wavelet transform [ e.g., Nose et al., 1998] is used to determine the very first signatures of ULF wave activity observed subsequent to substorm onset. We compare these results to the optical onset location in the ionosphere and the in-situ location of ULF wave initiation using the THEMIS and GOES satellites. Finally, we compare the location of the optical and magnetic signatures in the ionsosphere with results from a simple substorm current wedge model [e.g., Cramoysan et al., 1995] that produces estimates of the locations of the upward and downward field aligned currents and the Westward electrojet during the first few minutes of expansion phase onset. We propose to use these techniques to produce a substorm onset database during the THEMIS era.

  16. Response of plasmaspheric configuration to substorms revealed by Chang'e 3.

    PubMed

    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

    2016-01-01

    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 magnetosphere, and the configuration of the plasmasphere is sensitive to magnetospheric activity (storms and substorms). However, the response of the plasmaspheric configuration to substorms 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 substorms, which implies a causal relationship between the substorms and the formation of the three bulges on the plasmasphere. Instead of leading to plasmaspheric erosion as geomagnetic storms do, substorms initiated on the nightside of the Earth cause local inflation of the plasmasphere in the midnight region. PMID:27576944

  17. Response of plasmaspheric configuration to substorms revealed by Chang’e 3

    NASA Astrophysics Data System (ADS)

    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

    2016-08-01

    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 magnetosphere, and the configuration of the plasmasphere is sensitive to magnetospheric activity (storms and substorms). However, the response of the plasmaspheric configuration to substorms 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 substorms, which implies a causal relationship between the substorms and the formation of the three bulges on the plasmasphere. Instead of leading to plasmaspheric erosion as geomagnetic storms do, substorms initiated on the nightside of the Earth cause local inflation of the plasmasphere in the midnight region.

  18. Random and periodic substorms and their origins in the solar wind

    SciTech Connect

    Borovsky, J.E.; Belian, R.D.; Nemzek, R.J.; Smith, C.W.

    1994-05-01

    Substorms occur (recur) in two fashions: periodically with time or randomly in time. A statistical analysis of the time intervals {Delta}t between subsequent substorm onsets clearly shows these two types of substorms. When substorms are recurring periodically, the period is 3.1 {plus_minus} 1.2 hours, and the distribution of periods is gaussian. When substorms are occurring randomly, the time intervals {Delta}t between successive substorm onsets are distributed according to the exponential distribution exp({minus}{delta}t//5 hours), with a 5-hour mean interval between random onsets. With the use of the Los Alamos geosynchronous energetic-particle dam and the OMNI solar-wind data, it is shown that periodic substorms are associated with time intervals when the average value of the IMF is southward for extended periods of time and it is shown that randomly occurring substorms are statistically correlated with randomly occurring northward-to-southward reversals of the 1-hour-averaged values of the IMF B{sub z}.

  19. Force Balance and Substorm Effects in the Magnetotail

    NASA Technical Reports Server (NTRS)

    Kaufmann, Richard L.; Larson, Douglas J.; Kontodinas, Ioannis D.; Ball, Bryan M.

    1997-01-01

    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 magnetospheric 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 substorm processes. Generation of the rapid flows seen during substorm injection and bursty bulk flow events implies substantial force imbalances. The formation of a substorm 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 substorms and in differentiating pseudoexpansions from full substorms. 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.

  20. Energy storage and dissipation in the magnetotail during substorms. 1. Particle simulations

    SciTech Connect

    Winglee, R.M. ); Steinolfson, R.S. )

    1993-05-01

    The authors present a simulation study of the particle dynamics in the magnetotail during the development of substorms. They look at how energy flows into the magnetotail under external magnetospheric 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 magnetospheric boundary layer, on the nightside magnetopause. This pressure is expected to grow in response to solar wind penetration into the magnetosphere when the interplanetary magnetic field becomes southward in the initial phases of substorm 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 substorm 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 substorm onset, rather than instabilities such as the tearing mode.

  1. Magnetospheric plasma regions and boundaries

    NASA Technical Reports Server (NTRS)

    Heikkila, W. J.

    1975-01-01

    The boundaries of the various regions of the magnetospheric plasma are considered, taking into account the bow shock, the magnetopause, the outer boundary of the plasma sheet, the inner boundary of the plasma sheet, and the trapping boundary for energetic particles. Attention is given to the steady state, or quasi-steady state, to substorm effects in which temporal changes are important, and to primary auroral processes. A description is presented of the high latitude lobes of the magnetotail. The characteristics of magnetic field topology associated with interconnected interplanetary and geomagnetic field lines are illustrated with the aid of a graph.

  2. Plasma and magnetic field variations in the distant magnetotail associated with near-earth substorm effects

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Bame, S. J.; Mccomas, D. J.; Zwickl, R. D.; Slavin, J. A.; Smith, E. J.

    1987-01-01

    Examination of many individual event periods in the ISEE 3 deep-tail data set has suggested that magnetospheric substorms produce a characteristic pattern of effects in the distant magnetotail. During the growth, or tail-energy-storage phase of substorms, the magnetotail appears to grow diametrically in size, often by many earth radii. Subsequently, after the substorm 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 substorm onsets at earth, superposed epoch analyses of ISEE 3 and near-earth data prior to, and following, substorm expansive phase onsets have been performed. These analyses quantify and extend substantially the understanding of the deep-tail pattern of response to global substorm-induced dynamical effects.

  3. Propagating substorm injection fronts

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Arnoldy, R. L.; Feynman, J.; Hardy, D. A.

    1981-01-01

    It is argued that a series of two-satellite observations leads to a clarification of substorm 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.

  4. BARREL observations of a electron precipitation during a substorm

    NASA Astrophysics Data System (ADS)

    Halford, Alexa

    2016-07-01

    During the first Balloon Array for Relativistic Radiation belt Electron Loss (BARREL) campaign in January - February of 2013, many of the precipitation events observed were found to occur during geomagnetic substorms. Here we will look at one substorm in particular which occurred on 2 February 2013. During this event, there was an array of four payloads afloat above 27 km. Two of the payloads in particular mapped to the same L-shell and where bounded on either side by the two Van Allen Probes, LANL, and GOES satellites. The entire array also mapped to the CARISMA array and other ground based instruments in northern Canada. This set of unique observations allowed us to observe the substorm injection and the resultant region of electron precipitation.

  5. Recurrent embedded substorms during the 19 October 1998 GEM storm

    NASA Astrophysics Data System (ADS)

    Henderson, M. G.

    2016-08-01

    The 18-19 October 1998 GEM (Geospace Environment Modeling) storm was associated with a long interval of remarkably steady southward interplanetary magnetic field. In this study we demonstrate that classical substorms occurred throughout the interval and that the storm appears to be composed of the typical two-mode response consisting of a recurrent loading/unloading cycle on a timescale of approximately 2-4 h together with an episodic/bursty continuously driven component operating on a timescale of 5-15 min. The loading/unloading activity is manifested as typical poleward expanding "embedded" substorms (embedded into the auroral oval) emerging from the equatorward regions of the auroral distribution, while the continuously driven component is manifested by the episodic ejection of streamers equatorward from poleward boundary activations. The streamers subsequently produce torches and eastward drifting omega bands which likely moderate the need for substorms to occur more frequently than observed.

  6. Equatorial counterelectrojets during geomagnetic storms and their possible dynamos in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Kikuchi, T.; Hashimoto, K. K.; Ebihara, Y.; Tsuji, Y.; Veenadhari, B.; Nishimura, T.; Tanaka, T.; Fujita, S.; Nagatsuma, T.

    2012-12-01

    During the substorm 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 magnetosphere 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 substorms [Kobea et al., 2000; Kikuchi et al., 2000]. Both the R1 and R2 FACs are intensified by the substorm expansion, with the R2 FACs strong enough to cause the CEJ [Hashimoto et al., 2011]. The CEJ often occurs 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 magnetosphere. Based on the magnetometer and radar

  7. Energetics of the magnetosphere, revised

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1984-01-01

    The approximate magnitudes of power inputs and energies associated with the Earth's magnetosphere 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. Substorm 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 magnetosphere is small. Merging is essential for the existence of open field lines, which make such inputs possible. Merging also seems to be implicated in substorms: 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.

  8. Where and when does reconnection occur in the tail?

    NASA Astrophysics Data System (ADS)

    McPherron, Robert L.

    2016-05-01

    We comment on the question of when and where reconnection begins in the tail and how it is related to the onset of auroral expansion. This question was addressed in a workshop dedicated to Unsolved Problems in Magnetospheric Physics held in Scarborough, UK, in September 2015. The answer is that it typically occurs first in the midtail a little beyond 20 Re somewhat before midnight about 55 min after a southward turning of the solar wind magnetic field. It appears to be a consequence of plasma sheet thinning down to the scale of an ion gyroradius. The onset of the activation and expansion of auroral activity and accompanying magnetic signatures typically occur within 1 or 2 min of the appearance of signatures of midtail reconnection. The unanswered question is which comes first and whether reconnection is the cause of the auroral expansion. We point out that older observations clearly established that plasmoids (flux ropes) are released from near 20 Re within a few minutes of the usual signatures of expansion onset. This is only possible if reconnection occurs close to the Earth. More detailed observations with modern spacecraft have led to the development of new explanations for the cause of the substorm expansion that appear to neglect older observations. We conclude that it is essential to carefully define the various terms used in the study of substorms and to develop quantitative methods that enable statistical studies of the various processes associated with auroral expansion onset.

  9. Substorm onset: A switch on the sequence of transport from decreasing entropy to increasing entropy

    NASA Astrophysics Data System (ADS)

    Chen, C. X.

    2016-05-01

    In this study, we propose a scenario about the trigger for substorm onset. In a stable magnetosphere, entropy is an increasing function tailward. However, in the growth phase of a substorm, 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 substorm 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.

  10. Bursty reconnection modulating the substorm current wedge, a substorm case study re-analysed by ECLAT tools.

    NASA Astrophysics Data System (ADS)

    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

    2015-04-01

    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 substorm 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. Magnetospheric 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 substorm onset - bursty reconnection in the tail modulates the localised field aligned current flow associated with the substorm current wedge.

  11. A Double-Disruption Substorm Model - The Growth Phase

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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 magnetospheric 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 occurs both from the DTNL with the higher energy magnetospheric 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

  12. Charged Particle Energization and Transport in the Magnetotail during Substorms

    NASA Astrophysics Data System (ADS)

    Pan, Qingjiang

    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 substorms. 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 magnetosphere. 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 magnetosphere 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

  13. Observational evidence for an inside-out substorm onset scenario

    SciTech Connect

    Henderson, Michael G

    2008-01-01

    We present observations which provide strong support for a substorm onset scenario in which a localized inner magnetospheric 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 substorm 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' substorm onset scenario in which the near Earth region activates first followed at a later time by the formation of a near-to-mid tail substorm X-line. The ballooning instability is discussed as a likely mechanism for the initial onset.

  14. Calibrating a Magnetotail Model for Storm/Substorm Forecasting

    NASA Astrophysics Data System (ADS)

    Horton, W.; Siebert, S.; Mithaiwala, M.; Doxas, I.

    2003-12-01

    The physics network model called WINDMI for the solar WIND driven Magnetosphere-Ionosphere weather system is calibrated on substorm databases [1] using a genetic algorithm. We report on the use of the network as a digital filter to classify the substorms into three types; a process traditionally performed individual inspection. We then turn to using the filter on the seven Geospace Environmental Modeling (GEM) Storms designated for community wide study. These storms cover periods of days and contain many substorms. First the WINDMI model is run with the 14 parameters set from the study based on the Blanchard-McPherron database of 117 isolated substorms with 80% of the data having the AL below -500nT. In contrast, the GEM storms have long periods with AL in the range of -1000nT. The prediction error measured with the average-relative variance (ARV) is of approximately unity. Reapplying the genetic algorithm the parameters shift such that the one long storm has an ARV=0.59. Physics modifications of the basic WINDMI model including the injection of sheet plasma into the ring current are being evaluated in terms of their impact on the ARV and comparisons with non-physics based signal processing prediction filters. Ensembles of initial conditions are run with 700MHz G3 CPU run times of order 17 sec per orbit per day of real data. The AMD AthlonXP 1700+ processor takes 5sec per orbit per day. The IBM SP-2 speed will be reported. With such speeds it is possible to run balls of initial conditions. Substrom Classification with the WINDMI Model, W. Horton, R.S. Weigel, D. Vassiliadis, and I. Doxas, Nonlinear Processes in Geophysics, 1-9, 2003. This work was supported by the National Science Foundation Grant ATM-0229863.

  15. Saturn's outer magnetosphere

    NASA Technical Reports Server (NTRS)

    Schardt, A. W.; Behannon, K. W.; Carbary, J. F.; Eviatar, A.; Lepping, R. P.; Siscoe, G. L.

    1983-01-01

    Similarities between the Saturnian and terrestrial outer magnetosphere are examined. Saturn, like Earth, has a fully developed magnetic tail, 80 to 100 RS in diameter. One major difference between the two outer magnetospheres 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 magnetospheric particles extend to above 500 keV. In contrast, interplanetary protons and ions above 2 MeV have free access to the outer magnetosphere to distances well below the Stormer cutoff. This access presumably occurs 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.

  16. A statistical study of plasmawaves and energetic particles in the outer magnetosphere

    NASA Astrophysics Data System (ADS)

    Min, Kyungguk

    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 substorm event on 23March 2007 made in space and on ground. Timing analysis and a test particle simulation indicated that the electrons injected during the substorm 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 occur ubiquitously throughout the outer magnetosphere 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 magnetosphere to outer

  17. Magnetic cloud passage at Earth and associated substorm activity

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Freeman, M. P.; Burlaga, L. F.

    1992-01-01

    An approach to the study of the solar wind-magnetosphere interaction by signal type, that is, by examining the effect in the magnetosphere of well defined interplanetary structures, is presented. Focus is on the response of the magnetosphere to interplanetary magnetic clouds. Among their properties are: the slow and smooth variation of the magnetic field vector, with fluctuation level well below common interplanetary values; the similarly well behaved bulk flow; the wide range of field and flow parameters; and the longevity of passage (1 to 2 days). If the magnetic cloud is oriented such that a long period of uninterruptedly northward pointing field is followed by a long interval of continuously southward pointing field, then the transition of the magnetosphere from a quiescent state (the 'ground state') to a very active state can be studied, the latter being sustained by continued forcing from the magnetic cloud. A synopsis of the main findings of a recent study in such an interaction is given, concentrating on the substorm activity attending the second part of cloud passage.

  18. Modeling of substorm development with a kinematic effect by the global MHD simulations

    NASA Astrophysics Data System (ADS)

    den, Mitsue; Fujita, Shigeru; Tanaka, Takashi; Horiuchi, Ritoku

    Magnetic reconnection is considered to play an important role in space phenomena such as substorm in the Earth's magnetosphere. Recently, Tanaka and Fujita reproduced substorm 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 substorm 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 substorm 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 substorm development and the anomalous resistivity model.

  19. Nightside auroral zone and polar cap ion outflow as a function of substorm size and phase

    NASA Astrophysics Data System (ADS)

    Wilson, G. R.; Ober, D. M.; Germany, G. A.; Lund, E. J.

    2004-02-01

    Because the high latitude ionosphere is an important source of plasma for the magnetosphere under active conditions, we have undertaken a study of the way ion outflow from the nightside auroral zone and polar cap respond to substorm activity. We have combined data from the Ultraviolet Imager (UVI) on Polar with ion upflow measurements from the TEAMS instrument on the FAST spacecraft to construct a picture of ion upflow from these regions as a function of substorm size and as a function of time relative to substorm onset. We use data taken during solar minimum in the northern hemisphere between December 1996 and February 1997. We find that the total nightside auroral zone ion outflow rate (averaged over substorm phase) depends on the size of the substorm, increasing by about a factor of 10 for both O+ and H+ from the smallest to the largest substorms in our study. The combined outflow rate from both the polar cap and the nightside auroral zone goes up by a factor of 7 for both ions for the same change in conditions. Regardless of storm size, the nightside auroral zone outflow rate increases by about a factor of 2 after onset, reaching its peak level after about 20 min. These results indicate that the change in the nightside auroral zone ion outflow rate that accompanies substorm onset is not as significant as the change from low to high magnetic activity. As a consequence, the prompt increase in the near earth plasma sheet energy density of O+ and H+ ions that accompanies onset [, 1996] is likely due to local energization of ions already present rather than to the sudden arrival and energization of fresh ionospheric plasma.

  20. A comprehensive analysis of the geomagnetic storms occurred dur

    NASA Astrophysics Data System (ADS)

    Ghamry, Essam; Lethy, Ahmed; Arafa-Hamed, Tareq; Abd Elaal, Esmat

    2016-06-01

    The Geomagnetic storms are considered as one of the major natural hazards. Egyptian geomagnetic observatories observed multiple geomagnetic storms during 18 February to 2 March 2014. During this period, four interplanetary shocks successively hit the Earth's magnetosphere, leading to four geomagnetic storms. The storm onsets occurred on 18, 20, 23 and 27 February. A non-substorm Pi2 pulsation was observed on 26 February. This Pi2 pulsation was detected in Egyptian observatories (Misallat and Abu Simbel), Kakioka station in Japan and Carson City station in US with nearly identical waveforms. Van Allen Probe missions observed non-compressional Pc4 pulsations on the recovery phase of the third storm. This Pc4 event is may be likely attributed to the decay of the ring current in the recovery phase.

  1. Solar wind control of magnetospheric pressure (CDAW 6)

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1985-01-01

    The CDAW 6 data base is used to compare solar wind and magnetospheric 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 substorm onset and a decrease to 25 deg after the onset. This behavior supports the concept of tail energy storage before the substorm and subsequent release after the onset.

  2. Flow bursts, breakup arc, and substorm current wedge

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    2015-04-01

    Energy liberated by the reconnection process in the near-Earth tail is transported via flow bursts toward the dipolar magnetosphere during substorms. 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 magnetosphere 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 magnetosphere 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 substorm 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."

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

    NASA Technical Reports Server (NTRS)

    Spence, Harlan E.

    1996-01-01

    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 magnetospheric substorms. Specific questions of the when and where a substorm occurs and the connection between the auroral and magnetospheric 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 magnetosphere.' 'CRRES observations of particle flux dropout event.' The what, where, when, and why of magnetospheric substorm triggers'. and 'Low altitude signature of the plasma sheet: model prediction of local time dependence'.

  4. Electrodynamics of solar wind-magnetosphere-ionosphere interactions

    SciTech Connect

    Kan, J.R.; Akasofu, S.I.

    1989-04-01

    Significant progress has been made in the last two decades in understanding the workings of the solar wind-magnetosphere-ionosphere (SW-M-I) coupling system. In this paper the authors present a coherent picture of fundamental physical processes in three basic elements of the SW-M-I coupling system: (i) The field-aligned potential structure which leads to the formation of auroral arcs; (ii) the magnetosphere-ionosphere coupling which leads to the onset of magnetospheric substorms, and (iii) the solar wind-magnetosphere dynamo which supplies the power for driving various magnetospheric processes. Future research efforts to improve our understanding of the SW-M-I coupling processes should focus on integrating these three elements into a single quantitative model.

  5. Two Wide-Angle Imaging Neutral-Atom Spectrometers and Interstellar Boundary Explorer energetic neutral atom imaging of the 5 April 2010 substorm

    NASA Astrophysics Data System (ADS)

    McComas, D. J.; Buzulukova, N.; Connors, M. G.; Dayeh, M. A.; Goldstein, J.; Funsten, H. O.; Fuselier, S.; Schwadron, N. A.; Valek, P.

    2012-03-01

    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 substorm 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 magnetosphere 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 magnetospheric processes are occurring after compression of the magnetosphere 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 magnetospheric system and importance of the global perspective for macroscopic magnetospheric 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.

  6. Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during substorms

    NASA Technical Reports Server (NTRS)

    Daglis, Loannis A.; Livi, Stefano; Sarris, Emmanuel T.; Wilken, Berend

    1994-01-01

    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 substorm expansion phase and discuss its implications for the solar wind/magnetosphere/ionosphere coupling. Our aim is to examine the relation between auroral activity and the particle energization during substorms through the correlation between the AE indices and the energy density of the major magnetospheric ions. The data we used here were collected by the charge-energy-mass (CHEM) spectrometer on board the Active Magnetospheric Particle Trace Explorer (AMPTE)/Charge Composition Explorer (CCE) satellite in the near-equatorial nightside magnetosphere, 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 substorms. 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 substorm 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

  7. GEOTAIL and POLAR Observations of Auroral Kilometric Radiation and Terrestrial Low Frequency Bursts and their Relationship to Energetic Particles, Auroras, and Other Substorm Phenomena

    NASA Technical Reports Server (NTRS)

    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.

    1999-01-01

    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 substorms, GEOTAIL and POLAR plasma wave observations from within the magnetosphere 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 substorm 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 occur 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 occur 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 substorms that are associated with the generation and propagation of terrestrial LF bursts

  8. DP 1 and DP 2 current systems for the March 22, 1979 substorms

    NASA Astrophysics Data System (ADS)

    Clauer, C. R.; Kamide, Y.

    1985-02-01

    The March 22, 1979 substorm interval selected for analysis by the CDAW 6 has been investigared using a ground magnetic data inversion scheme which computes equivalent current patterns as well as real ionospheric and field aligned current distributions. These have been computed at 5-minute increments during the two substorm intervals on this day. The computed results have been analyzed using a differential technique which permits us to isolate the current development which occurs during selected time intervals. We find that both DP1 and DP 2 currents develop during the course of the substorm activity. The first substorm is characterized by the gradual enhancement of a DP 2 equivalent current system following the southward turning of the interplanetary magnetic field. The major magnetic disturbance associated with the expansion phase of the substorm is dominated by the development of a Dp 1 current system. During the second interval which consists of several hours of magnetic disturbance, the DP 2 system grows to be much stronger and is the dominant contribution to much of the auroral magnetic activity. The peak of the activity during the second substorm interval appears to be composed of both strong DP 2 and DP 1 currents coexisting. Following the decay of the DP 1 system a strong DP 2 system continues to exist during the enhanced convection phase of the substorm.

  9. Effects of substorm electrojet on declination along concurrent geomagnetic latitudes in the northern auroral zone

    NASA Astrophysics Data System (ADS)

    Edvardsen, Inge; Johnsen, Magnar G.; Løvhaug, Unni P.

    2016-10-01

    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 substorm 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 substorms. In the auroral zones, substorms are common phenomena, occurring almost every night. In principle, the magnitude of geomagnetic disturbances from two identical substorms along concurrent geomagnetic latitudes around the globe, at different local times, will be the same. However, the signature of a substorm 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 substorm current wedge model in combination with a dipole representation of the Earth's magnetic field to simulate magnetic substorms 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.

  10. Azimuthal structure of substorm breakup arcs prior to expansive phase onset using ISUAL/FORMOSAT-2

    NASA Astrophysics Data System (ADS)

    Chang, T.; Cheng, C.; Chiang, C.; Tam, S. W.; Chen, A. B.; Hsu, R.; Su, H.

    2008-12-01

    Substorm breakup arcs are investigated for substorm onset that occurs at the location of "Harang discontinuity" at pre-midnight. The auroral breakup arc images are obtained by the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) onboard FORMOSAT-2 satellite. We identify that the auroral breakup arc brightening occurs at the same time as the associated negative H-Bay and Pi 2 pulsations. It begins with a brightening on the arc and evolves into clear bead-like structure with approximate equally spaced separation along the arc direction. The enhanced auroral arcs finally break up into several parts. The azimuthal mode number of auroral breakup arcs prior to expansive phase onset ranges from ~200 to ~300. Based on the observations, we suggest that the substorm initial breakup arcs are consistent with kinetic ballooning instability, which is localized at the center of cross tail current sheet at about -(8-10) RE for strong substorms.

  11. Jumps of the solar wind direction and the substorm probability

    NASA Astrophysics Data System (ADS)

    Kubyshkina, Daria; Kubyshkina, Marina; Semenov, Vladimir

    2015-04-01

    Magnetospheric substorm 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 substorm 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 substorm 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 substorm 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

  12. Current sheet thinning, reconnection onset, and auroral morphology during geomagnetic substorms

    NASA Astrophysics Data System (ADS)

    Otto, A.; Hsieh, M. S.

    2015-12-01

    Geomagnetic substorms represent a fundamental energy release mechanism for the terrestrial magnetosphere. Specifically, the evolution of thin currents sheets during the substorm growth phase plays a key role for substorms 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 magnetosphere. While the auroral morphology associated with MFD and near Earth current sheet formation is well consistent with typical substorm 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 substorm 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.

  13. Towards a synthesis of substorm electrodynamics: HF radar and auroral observations

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Lester, M.; Parkinson, M. L.; Yeoman, T. K.; Dyson, P. L.; Devlin, J. C.; Frey, H. U.

    2006-12-01

    At 08:35 UT on 21 November 2004, the onset of an interval of substorm activity was captured in the southern hemisphere by the Far UltraViolet (FUV) instrument on board the IMAGE spacecraft. This was accompanied by the onset of Pi2 activity and subsequent magnetic bays, evident in ground magnetic data from both hemispheres. Further intensifications were then observed in both the auroral and ground magnetic data over the following ~3 h. During this interval the fields-of-view of the two southern hemisphere Tasman International Geospace Enviroment Radars (TIGER) moved through the evening sector towards midnight. Whilst initially low, the amount of backscatter from TIGER increased considerably during the early stages of the expansion phase such that by ~09:20 UT an enhanced dusk flow cell was clearly evident. During the expansion phase the equatorward portion of this flow cell developed into a narrow high-speed flow channel, indicative of the auroral and sub-auroral flows identified in previous studies (e.g. Freeman et al., 1992; Parkinson et al., 2003). At the same time, higher latitude transient flow features were observed and as the interval progressed the flow reversal region and Harang discontinuity became very well defined. Overall, this study has enabled the spatial and temporal development of many different elements of the substorm process to be resolved and placed within a simple conceptual framework of magnetospheric convection. Specifically, the detailed observations of ionospheric flows have illustrated the complex interplay between substorm electric fields and associated auroral dynamics. They have helped define the distinct nature of different substorm current systems such as the traditional substorm current wedge and the more equatorward currents associated with polarisation electric fields. Additionally, they have revealed a radar signature of nightside reconnection which provides the promise of quantifying nightside reconnection in a way which has

  14. Ionospheric loop currents and associated ULF oscillations at geosynchronous altitudes during preonset intervals of substorm aurora

    NASA Astrophysics Data System (ADS)

    Saka, O.; Hayashi, K.; Leonovich, A. S.

    2015-04-01

    A substorm aurora was observed at 04:52 UT on 27 January 1986 by an all-sky imager installed at Shamattawa (66.3°N, 336.0° in corrected geomagnetic coordinates) and a magnetometer on board a conjugate satellite (GOES 6) at geosynchronous altitudes. In the preonset intervals lasting for approximately 50 min prior to the expansion onset, an equatorward drift of the auroras beginning from 71°N to 64°N was observed. Meanwhile, GOES 6 observed ULF oscillations in 25-200 s periods at geosynchronous altitudes after about 10 min following the start of the equatorward drift. During the equatorward drift of the arc, the flow reversal occurred, where the auroral arc propagating eastward was replaced by a westward propagation. Simultaneously, the major axes of the ULF oscillations rotated clockwise by ~90° in the equatorial plane. We conclude that the ULF oscillations are azimuthally small-scale Alfvén waves excited in the magnetosphere by field-aligned currents associated with ionospheric loop currents.

  15. Substorm features in MHD (magnetohydrodynamics) simulations of magnetotail dynamics

    SciTech Connect

    Birn, J.; Hesse, M.

    1990-01-01

    We present a review and extended analysis of characteristic results from our nonideal three-dimensional MHD simulations of unstable magnetotail evolution, which develops without the necessity of external driving or prescribed localization on nonideal effects. These modes involve magnetic reconnection at a near-Earth site in the tail, consistent with the near-Earth neutral line model of substorms. The evolution tailward of the reconnection site is characterized by plasmoid formation and ejection into the far tail, plasma sheet thinning between the near-Earth neutral line (X line) and the departing plasmoid, and fast tailward flow, which occupies large sections of the plasma sheet at larger distance from the X line, while it occurs only in very limited space and time sections close to the X line. The region earthward of the X line is characterized by dipolarization, propagating from midnight toward the flank regions and, perhaps, tailward. It is associated with the signatures of the substorm current wedge: reduction and diversion of cross-tail current from a region surrounding the reconnection site and increase of Region 1 type field-aligned currents. A mapping of these currents to the Earth on the basis of an empirical magnetic field model shows good agreement of the mapped current system with the observed Region 1 field-aligned current system and its substorm associated changes, including also a nightward and equatorward shift of the peaks of the field-aligned current density. The evolution of the mappings of the boundaries of the closed field line region bears strong resemblance to the formation and expansion of he auroral bulge. The consistency of all of these details with observed substorm features strongly supports the idea that substorm evolution in the tail is that of a large scale nonideal instability.

  16. Electrostatic waves in the magnetosphere.

    NASA Technical Reports Server (NTRS)

    Scarf, F. L.; Fredricks, R. W.

    1972-01-01

    Electric dipole antennas on magnetospheric spacecraft measure E field components of many kinds of electromagnetic waves. In addition, lower hybrid resonance emissions are frequently observed well above the ionosphere. The Ogo 5 plasma wave experiment has also detected new forms of electrostatic emissions that appear to interact very strongly with the local plasma particles. Greatly enhanced wave amplitudes have been found during the expansion phases of substorms, and analysis indicates that these emissions produce strong pitch angle diffusion. Intense broadband electrostatic turbulence is also detected at current layers containing steep magnetic field gradients. This current-driven instability is operative at the bow shock and also at field null regions just within the magnetosheath, and at the magnetopause near the dayside polar cusp. The plasma turbulence appears to involve ion acoustic waves, and the wave particle scattering provides an important collisionless dissipation mechanism for field merging.

  17. Role of cross-field current instability in substorm onsets and intensifications

    NASA Technical Reports Server (NTRS)

    Lui, Anthony T. Y.

    1992-01-01

    A cross field current instability is investigated as a potential mechanism for current reduction/disruption during substorm onsets and intensifications. Linear stability analysis shows that, for sufficiently strong current density, the instability can occur in the plasma sheet with a growth time comparable to the substorm onset time and excite waves with a significant electromagnetic component. Nonlinear analysis shows that the wave growth reaches the nonlinear stage in less than one ion gyroperiod and can reduce the cross tail current by approximately 15 to 28 of its initial value at saturation. The resulting anomalous resistivity is 11 to 12 orders of magnitude above the classical value. For a typical current reduction, the plasma in the disruption region is subjected to an earthward force. The substorm development scenario constructed based on this instability can readily account for a large number of substorm features.

  18. Substorms observations over Apatity during geomagnetic storms in the period 2012 - 2016

    NASA Astrophysics Data System (ADS)

    Guineva, Veneta; Werner, Rolf; Despirak, Irina; Kozelov, Boris

    2016-07-01

    In this work we studied substorms, 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. Substorm 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 substorms occurred 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 substorms developed during different phases of the geomagnetic storms was discussed.

  19. The Relationship Between Magnetotail Dynamics and Substorm Onset Longitudes Determined from Spacecraft Images

    NASA Technical Reports Server (NTRS)

    Ieda, A.; Fairfield, D. H.; Mukai, T.; Saito, Y.

    1999-01-01

    Geotail plasma and magnetic field observations of plasmoids between 25 and 30 Re have been compared to Polar UVI observations of auroral brightenings. Plasmoids almost always corresponded to brightenings but the brightenings were sometimes weak and spatially limited and did not always grow to a global substorm. Even a case where a plasmoid event occurred with fast post-plasmoid flow corresponded to a weak brightening but no substorm. Some brightenings did not correspond to plasmoids, but these events were observed away from the longitude of Geotail. The plasmoids are observed 0-2 min after the brightenings in most cases. It seems likely that formation of a near-Earth neutral line causes each brightening in the polar ionosphere, but these formations do not have a one-to-one relationship with a substorm onset. What causes development of the full, large-scale substorm remains an open question.

  20. Plasma Circulation in the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Fok, Mei-Ching; Delcourt, D. C.; Slinker, S.; Fedder, J. A.; Buenfil, M.

    2006-01-01

    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 magnetosphere, 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 substorm owing to compression of pre-existing plasmas. The SB(sub z), interval (embedded in NB(sub z)) produces a substorm after about one hour of development. Both disturbances enhance the auroral wind flux and heavy ion pressure of the magnetosphere 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.

  1. Nuclear magnetohydrodynamic EMP, solar storms, and substorms

    SciTech Connect

    Rabinowitz, M. ); Meliopoulous, A.P.S.; Glytsis, E.N. . School of Electrical Engineering); Cokkinides, G.J. )

    1992-10-20

    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. Substorms produce much smaller effects than SS-GIC, but occur much more frequently. This paper describes the physics of such geomagnetic disturbances and analyzes their effects.

  2. Physical Mechanism of Substorm Breakup Arcs and Onset

    NASA Astrophysics Data System (ADS)

    Peng, A.; Cheng, C.; Zaharia, S.; Gorelenkov, N.; Chang, T.

    2008-12-01

    Observations show that Pi 2 waves are excited prior to the appearance of breakup auroral arcs that break up after substorm expansion onset. The Pi2 waves and the breakup arcs are modeled by the Kinetic Ballooning Instability (KBI), which is destabilized by plasma pressure gradient and magnetic field curvature in the high beta magnetic well region in the near-Earth plasma sheet. Our model is based on the theoretical analysis and numerical solutions of the gyrokinetic mode equations for late growth phase 3D magnetospheric equilibria. The results show that the KBI has a real frequency associated with the ion magnetic drift frequency, which is in the Pi2 frequency range, and the most unstable KBI has an azimuthal mode number on the order of 200- 300. The theoretical KBI features are consistent with observational features in both the aurora breakup arcs and the near-Earth plasma sheet. Comparison between our KBI model and substorm breakup arc observations by FORMOSAT-2's ISUAL and THEMIS All Sky Imagers will be presented.

  3. Equatorial magnetospheric particles and auroral precipitations

    NASA Astrophysics Data System (ADS)

    McIlwain, C. E.

    The injection boundary beyond which fresh hot plasma appears each magnetospheric substorm is generalized and extended to circle the Earth. The concept of an auroral shell representing the inner limit of active auroral processes is introduced. It is proposed that at low altitudes, this shell marks the equatorward edge of the auroral ovals, and that at high altitudes, it marks the injection boundary. The auroral ring is defined as the intersection of the auroral shell with the magnetic equator. A simple equation for computing the expected location of the auroral ring as a function of local time and magnetic disturbance level is obtained. Tests indicate that the model is valid and reasonably accurate.

  4. Magnetosphere-ionosphere coupling during plasmoid evolution - First results

    NASA Technical Reports Server (NTRS)

    Hesse, Michael; Birn, Joachim

    1991-01-01

    The influence of magnetosphere-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 substorm evolution and the modification of the latter by the convection driven by the ionospheric electric fields. For comparison, results are presented from a simulation which uses an infinitely conducting ionosphere but is otherwise identical. Comparison of the two simulations shows that the major impact of magnetosphere-ionospheric communication is an acceleration of magnetotail evolution. Otherwise, phenomena in the two models are qualitatively similar. It is concluded that ionospheric effects do not significantly affect substorm associated magnetotail dynamics.

  5. On the relationship between the energetic particle flux morphology and the change in the magnetic field magnitude during substorms

    NASA Technical Reports Server (NTRS)

    Lopez, R. E.; Lui, A. T. Y.; Sibeck, D. G.; Takahashi, K.; Mcentire, R. W.

    1989-01-01

    The relationship between the morphology of energetic particle substorm 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 substorms 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 substorms in general in the inner magnetosphere. 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.

  6. Quantifying the spatio-temporal correlation during a substorm using dynamical networks formed from the SuperMAG database of ground based magnetometer stations.

    NASA Astrophysics Data System (ADS)

    Dods, J.; Chapman, S. C.; Gjerloev, J. W.; Barnes, R. J.

    2014-12-01

    The overall morphology and dynamics of magnetospheric substorms is well established in terms of observed qualitative auroral features and signatures seen in ground based magnetometers. The detailed evolution of a given substorm is captured by typically ~100 ground based magnetometer observations and this work seeks to synthesise all these observations in a quantitative manner. We present the first analysis of the full available set of ground based magnetometer observations of substorms using dynamical networks. SuperMAG offers a database containing ground station magnetometer data at a cadence of 1min from 100s stations situated across the globe. We use this data to form dynamic networks which capture spatial dynamics on timescales from the fast reconfiguration seen in the aurora, to that of the substorm cycle. Windowed linear cross-correlation between pairs of magnetometer time series along with a threshold is used to determine which stations are correlated and hence connected in the network. Variations in ground conductivity and differences in the response functions of magnetometers at individual stations are overcome by normalizing to long term averages of the cross-correlation. These results are tested against surrogate data in which phases have been randomised. The network is then a collection of connected points (ground stations); the structure of the network and its variation as a function of time quantify the detailed dynamical processes of the substorm. The network properties can be captured quantitatively in time dependent dimensionless network parameters and we will discuss their behaviour for examples of 'typical' substorms and storms. The network parameters provide a detailed benchmark to compare data with models of substorm dynamics, and can provide new insights on the similarities and differences between substorms and how they correlate with external driving and the internal state of the magnetosphere.

  7. A Catapult (Slingshot) Current Sheet Relaxation Model for Substorm Triggering

    NASA Astrophysics Data System (ADS)

    Machida, S.; Miyashita, Y.; Ieda, A.

    2010-12-01

    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 magnetosphere to initiate some instability such as a ballooning instability or other instabilities, and the substorm starts in the inner magnetosphere. 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 substorm 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.

  8. Mercury's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Slavin, J. A.

    1999-01-01

    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 'magnetosphere' 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 magnetospheres 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 magnetosphere 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 magnetospheres or, in the case of the weakly magnetized Venus and Mars, directly to the solar wind. This magnetosphere-ionosphere coupling is mediated largely through field-aligned currents (FACs) flowing along the magnetic field lines linking the magnetosphere 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 magnetospheric plasma (following ionization) whose composition may influence subsequent magnetotail dynamics. However, the dominant source of plasma for most of the terrestrial magnetosphere is the 'leakage'of solar wind across the magnetopause and more

  9. Global Simulation of Proton Precipitation Due to Field Line Curvature During Substorms

    NASA Technical Reports Server (NTRS)

    Gilson, M. L.; Raeder, J.; Donovan, E.; Ge, Y. S.; Kepko, L.

    2012-01-01

    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 magnetosphere where the ion gyroradius becomes comparable to the local field line curvature. However, the location of the IB in the magnetosphere 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 substorms. 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 substorms presented and the azimuthal splitting is caused by the development of the substorm current wedge. The simulation also demonstrates that the central plasma sheet temperature can significantly influence when and where the azimuthal splitting takes place.

  10. Saw-tooth substorms: inconsistency of repetitive bay-like magnetic disturbances with behavior of aurora

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Stauning, Peter; Liou, Kan; Reeves, Geoffrey

    The relationships between the magnetic disturbances in the auroral zone, aurora dynamics and particles injections at the geostationary orbit have been analyzed in detail for 62 repetitive bay-like magnetic disturbances (sawtooth substorms). It is shown that lack of the auroral breakup is typical of the powerful repetitive bay-like disturbances, unlike the isolated ("classi-cal") magnetospheric substorms. In case of sawtooth substorms the aurora in the oval usually demonstrates high activity well before (up to few hours) the magnetic disturbance onset. One of the distinguishing features of the auroral activity is the double oval structure, which is most noticeable near the dusk meridian. The close relation of the auroral behavior to the parti-cle injections at geostationary orbit breaks down. The conclusion is made, that the powerful repetitive bay-like magnetic disturbances display that kind of disturbance, which is regulated by the ionospheric electric field variations unlike to the isolated ("classical") substorms strongly related to the varying auroral particle precipitation.

  11. Shape-Constrained Sparse and Low-Rank Decomposition for Auroral Substorm Detection.

    PubMed

    Yang, Xi; Gao, Xinbo; Tao, Dacheng; Li, Xuelong; Han, Bing; Li, Jie

    2016-01-01

    An auroral substorm is an important geophysical phenomenon that reflects the interaction between the solar wind and the Earth's magnetosphere. Detecting substorms is of practical significance in order to prevent disruption to communication and global positioning systems. However, existing detection methods can be inaccurate or require time-consuming manual analysis and are therefore impractical for large-scale data sets. In this paper, we propose an automatic auroral substorm detection method based on a shape-constrained sparse and low-rank decomposition (SCSLD) framework. Our method automatically detects real substorm onsets in large-scale aurora sequences, which overcomes the limitations of manual detection. To reduce noise interference inherent in current SLD methods, we introduce a shape constraint to force the noise to be assigned to the low-rank part (stationary background), thus ensuring the accuracy of the sparse part (moving object) and improving the performance. Experiments conducted on aurora sequences in solar cycle 23 (1996-2008) show that the proposed SCSLD method achieves good performance for motion analysis of aurora sequences. Moreover, the obtained results are highly consistent with manual analysis, suggesting that the proposed automatic method is useful and effective in practice. PMID:25826810

  12. Compressional ULF waves in the outer magnetosphere. I - Statistical study

    NASA Technical Reports Server (NTRS)

    Zhu, Xiaoming; Kivelson, Margaret G.

    1991-01-01

    Statistical properties of the ULF waves of period 2-20 min in the outer magnetosphere were studied using 14 months of magnetic field and plasma data obtained by the ISEE 1 and 2 spacecraft. It was found that intense compressional waves with typical wave periods of 10 min are a persistent feature near the two flanks of the magnetosphere; they are mainly polarized in a meridian plane with comparable compressional and transverse amplitudes and have larger amplitudes at higher latitudes. Transverse waves polarized in the azimuthal direction are found to be mainly a nightside phenomenon, and they seem to be associated with substorm activity.

  13. Magnetic energy storage and the nightside magnetosphere-ionosphere coupling

    SciTech Connect

    Horton, W.; Pekker, M.; Doxas, I.

    1998-05-01

    The change m in the magnetic energy stored m in the Earth`s magnetotail as a function of the solar wind, BIF conditions are investigated using an empirical magnetic field model. The results are used to calculate the two normal modes contained m in the low-dimensional global model called WINDMI for the solar wind driven magnetosphere-ionosphere system. The coupling of the magnetosphere-ionosphere (MI) through the nightside region 1 current loop transfers power to the ionosphere through two modes: a fast (period of minutes) oscillation and a slow (period of one hour) geotail cavity mode. The solar wind drives both modes m in the substorm dynamics.

  14. Stepwise tailward retreat of magnetic reconnection: THEMIS observations of an auroral substorm

    NASA Astrophysics Data System (ADS)

    Ieda, A.; Nishimura, Y.; Miyashita, Y.; Angelopoulos, V.; Runov, A.; Nagai, T.; Frey, H. U.; Fairfield, D. H.; Slavin, J. A.; Vanhamäki, H.; Uchino, H.; Fujii, R.; Miyoshi, Y.; Machida, S.

    2016-05-01

    Auroral stepwise poleward expansions were clarified by investigating a multiple-onset substorm that occurred on 27 February 2009. Five successive auroral brightenings were identified in all-sky images, occurring at approximately 10 min intervals. The first brightening was a faint precursor. The second brightening had a wide longitude; thus, it represented the Akasofu substorm onset. Other brightenings expanded poleward; thus, they were interpreted to be auroral breakups. These breakups occurred stepwise; that is, later breakups were initiated at higher latitudes. Corresponding reconnection signatures were studied using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations between 8 and 24 RE down the magnetotail. The Akasofu substorm onset was not accompanied by a clear reconnection signature in the tail. In contrast, the three subsequent auroral breakups occurred simultaneously (within a few minutes) with three successive fast flows at 24 RE; thus, these were interpreted to be associated with impulsive reconnection episodes. These three fast flows consisted of a tailward flow and two subsequent earthward flows. The flow reversal at the second breakup indicated that a tailward retreat of the near-Earth reconnection site occurred during the substorm expansion phase. In addition, the earthward flow at the third breakup was consistent with the classic tailward retreat near the end of the expansion phase; therefore, the tailward retreat is likely to have occurred in a stepwise manner. We interpreted the stepwise characteristics of the tailward retreat and poleward expansion to be potentially associated by a stepwise magnetic flux pileup.

  15. Pulsars Magnetospheres

    NASA Technical Reports Server (NTRS)

    Timokhin, Andrey

    2012-01-01

    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 magnetosphere: y-ray pulsars (?) Plasma oscillations in discharges: direct radio emission (?)

  16. Different magnetospheric modes: solar wind driving and coupling efficiency

    NASA Astrophysics Data System (ADS)

    Partamies, N.; Pulkkinen, T. I.; McPherron, R. L.; McWilliams, K.; Bryant, C. R.; Tanskanen, E.; Singer, H. J.; Reeves, G. D.; Thomsen, M. F.

    2009-11-01

    This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC) intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential), particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to) the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/EY). Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading-unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations) during geomagnetically active conditions.

  17. Particle Energization During Magnetic Storms with Steady Magnetospheric Convection

    NASA Astrophysics Data System (ADS)

    Kissinger, J.; Kepko, L.; Baker, D. N.; Kanekal, S. G.; Li, W.; McPherron, R. L.; Angelopoulos, V.

    2013-12-01

    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 substorms on seed electron injections has received considerable focus, in this study we explore how quasi-steady convection during steady magnetospheric convection (SMC) events affects the transport and energization of electrons. SMC events are long-duration intervals of enhanced convection without any substorm expansions, and are an important mechanism in coupling magnetotail plasma populations to the inner magnetosphere. 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 magnetosphere. 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 substorms.

  18. Effects of Finite Element Resolution in the Simulation of Magnetospheric Particle Motion

    NASA Technical Reports Server (NTRS)

    Hansen, Richard

    2006-01-01

    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 substorm dipolarizations of the magnetospheric tail.

  19. A current disruption mechanism in the neutral sheet - A possible trigger for substorm expansions

    NASA Technical Reports Server (NTRS)

    Lui, A. T. Y.; Mankofsky, A.; Chang, C.-L.; Papadopoulos, K.; Wu, C. S.

    1990-01-01

    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 occur under conditions expected for the neutral sheet just prior to the onset of substorm 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 substorm current wedge. A substorm 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 substorm intervals. The skew in local time of substorm onset location and the three conditions under which substorm onset is observed can be understood on the basis of the proposed scenario.

  20. Constraining the substorm problem using ULF wave techniques

    NASA Astrophysics Data System (ADS)

    Rae, I. J.; Mann, I. R.; Murphy, K. R.; Milling, D. K.; Team, T.

    2008-12-01

    substorm onset We outline the characteristics of ULF pulsations in both the Pi1 and Pi2 bands in the nightside ionosphere and magnetosphere during substorms. We describe the use of these techniques in creating a substorm onset database during the THEMIS era for use by the scientific community. Finally, we detail the development of a Canadian AE calculation that will be routinely available at the Canadian Space Sciences Data Portal (www.cssdp.ca)

  1. Substorm onset: Current sheet avalanche and stop layer

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    2015-03-01

    A new scenario is presented for the onset of a substorm 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 magnetosphere 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 substorm 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 substorm current wedge. The source of the latter must be

  2. Association of plasma sheet variations with auroral changes during substorms

    SciTech Connect

    Hones, E.W. Jr.; Craven, J.D.; Frank, L.A.; Parks, G.K.

    1988-01-01

    Images of the southern auroral oval taken by the University of Iowa auroral imaging instrumentation on the Dynamics Explorer 1 satellite during an isolated substorm 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, occurring 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 substorm's recovery. 9 refs. 3 figs.

  3. Magnetospheric feedbacks in solar wind energy transfer

    NASA Astrophysics Data System (ADS)

    Palmroth, Minna; Pulkkinen, Tuija I.; Anekallu, Chandrasekhar R.; Honkonen, Ilja; Koskinen, Hannu E. J.; Lucek, Elizabeth A.; Dandouras, Iannis

    2010-05-01

    The solar wind kinetic energy, fueling all dynamical processes within the near-Earth space, is extracted by a dynamo process at the magnetopause converting kinetic energy into magnetic energy. We investigate the magnetopause energy transfer both in small and large scales; using Cluster observations as well as a three-dimensional global magnetohydrodynamic (MHD) simulation GUMICS-4. In the simulation, the spatial distribution of the energy transfer exhibits a dependence on the interplanetary magnetic field (IMF) orientation, which is shown to agree with observational local estimates from Cluster spacecraft recordings. In both sythetic runs with artificial solar wind input as well as in reproductions of the observed solar wind we observe a "hysteresis" effect, where the magnetopause energy input stays enhanced longer than the traditional energy transfer proxies (e.g., epsilon) indicate. Specifically we focus in the simulation of a substorm sequence on Feb 18, 2004, during which an exceptional agreement between the simulation results and spacecraft recordings was observed on several orbits within the near-Earth space. In this event, we again observe the hysteresis effect and investigate the processes causing it at the magnetopause. We argue that since GUMICS-4 reproduces the observed signatures of the substorm sequence in question, the simulation results represent physical processes within the magnetosphere. We conclude that as the simulation energy input exhibits delays already at the magnetopause, the delays in the classical substorm loading - unloading cycle may be interpreted in a new light.

  4. Transport and acceleration of plasma in the magnetospheres of Earth and Jupiter and expectations for Saturn

    NASA Astrophysics Data System (ADS)

    Kivelson, M. G.

    The first comparative magnetospheres conference was held in Frascati, Italy thirty years ago this summer, less than half a year after the first spacecraft encounter with Jupiter's magnetosphere (Formisano, V. (Ed.), The Magnetospheres 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 substorms 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 magnetosphere 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 substorms. At Saturn, the centrifugal stresses are not effective in distorting the magnetic field, so in some ways the magnetosphere appears Earthlike. Yet the presence of plasma sources in the close-in equatorial magnetosphere 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 magnetosphere. This paper addresses issues relevant to plasma transport and acceleration in all three magnetospheres.

  5. Boundary layers of the earth's outer magnetosphere

    NASA Technical Reports Server (NTRS)

    Eastman, T. E.; Frank, L. A.

    1984-01-01

    The magnetospheric boundary layer and the plasma-sheet boundary layer are the primary boundary layers of the earth's outer magnetosphere. Recent satellite observations indicate that they provide for more than 50 percent of the plasma and energy transport in the outer magnetosphere although they constitute less than 5 percent by volume. Relative to the energy density in the source regions, plasma in the magnetospheric boundary layer is predominantly deenergized whereas plasma in the plasma-sheet boundary layer has been accelerated. The reconnection hypothesis continues to provide a useful framework for comparing data sampled in the highly dynamic magnetospheric environment. Observations of 'flux transfer events' and other detailed features near the boundaries have been recently interpreted in terms of nonsteady-state reconnection. Alternative hypotheses are also being investigated. More work needs to be done, both in theory and observation, to determine whether reconnection actually occurs in the magnetosphere and, if so, whether it is important for overall magnetospheric dynamics.

  6. Jupiter's Dynamic Magnetosphere

    NASA Astrophysics Data System (ADS)

    Vogt, M. F.; Bunce, E. J.; Kronberg, E. A.; Jackman, C. M.

    2014-12-01

    Jupiter's magnetosphere is a highly dynamic environment. Hundreds of reconnection events have been identified in Jupiter's magnetotail through analysis of magnetic field and particle measurements collected by the Galileo spacecraft. Quasi-periodic behavior, suggestive of reconnection, has been intermittently observed on a ~2-3 day time scale in several data sets, including magnetic field dipolarizations, flow bursts, auroral polar dawn spots, and the hectometric radio emission. In this paper we review the present state of knowledge of Jovian magnetospheric dynamics. Throughout the discussion, we highlight similarities and differences to Saturn's magnetosphere. For example, recent analysis of plasmoid signatures at both Jupiter and Saturn has established the role of tail reconnection in the overall mass and flux transport in the outer planet magnetospheres. The results for both Jupiter and Saturn suggest that the observed mass loss rate due to tail reconnection and plasmoid release is insufficient to account for the mass input rate from the moons Io and Enceladus, respectively. We also present new analysis in which we use the Michigan mSWiM propagated solar wind MHD model to estimate the solar wind conditions upstream of Jupiter. This information allows us to determine whether reconnection events occur preferentially during certain solar wind conditions, or whether there is evidence that the solar wind modulates the quasi-periodicity seen in the field dipolarizations and flow bursts.

  7. Contribution of Latin-American scientists to the study of the magnetosphere of the Earth. A review

    NASA Astrophysics Data System (ADS)

    Stepanova, M.; Valdivia, J. A.

    2016-11-01

    Since the very beginning of the space era, Latin-American scientists have been contributing to the understanding of the magnetosphere 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 magnetosphere of the Earth such as geomagnetic storms and substorms and possible relations between them, interplanetary origin of storms, role of turbulent processes in the magnetosphere dynamics, and analysis of the dynamics of the magnetosphere as a complex self-organized non-linear system.

  8. Simultaneous ground-satellite observation of Pi 2 pulsations associated with upward/downward FACs of the substorm current wedge

    NASA Astrophysics Data System (ADS)

    Uozumi, T.; Yumoto, K.; Imajo, S.; Koga, K.; Obara, T.; Baishev, D. G.; Shevtsov, B. M.; Milling, D. K.; Mann, I. R.; Ikeda, A.; Abe, S.; Yoshikawa, A.; Kawano, H.

    2011-12-01

    The formation of a substorm current wedge (SCW) is one of the fundamental processes in the expansion phase of the magnetospheric substorm [e.g. McPherron et al., 1973]. Uozumi et al. [2011] found that the ground Pi 2 timeseries had high coherencies with simultaneously observed AKR timeseries, regardless of whether the Pi 2 timeseries were associated with upward FAC or downward FAC; this fact suggests that the upward SCW and the downward SCW oscillated in a synchronized manner. This aspect was deduced from ground observations, and should be verified by a simultaneous observation on the ground and in the magnetosphere. In order to clarify the timing relation of Pi 2s that are associated with SCW oscillations, we made a comparative study by combining the ground and satellite data. We analyzed simultaneous ground-satellite observation of Pi 2 pulsation at the ETS-VIII geosynchronous orbit [Koga and Obara, 2008] and at MAGDAS/CPMN [Yumoto and the MAGDAS Group, 2006] high-, middle- and low-latitude stations. We picked up a Pi 2 event that exhibited a high coherency in the waveform among the ground and satellite Pi 2. A typical Pi 2 occurred around 1121UT on July 28, 2008. MLT of each ground station and ETS-VIII at the occurrence of the Pi 2 was as follows: TIK: 19.5h, KUJ: 20.0h, ETS-VIII: 20.8h, ZYK: 20.9h, MGD: 21.0h, PTK: 21.5h and WAD: 3.7h. Characteristics of the Pi 2 event are summarized as follows: (1) the initial deflection of the ground Pi 2s and magnetic bay variations in the D (eastward) component indicate the signature of the upward (at TIK, ZYK, MGD and PTK) and downward (at WAD) FAC of the SCW. (2) Pi 2 oscillated in- or 180deg out-of-phase among the D on the ground and N (eastward) components at the geosynchronous altitude (correlation coefficient: |Υ|> 0.75, phase delay: |ΔT|<10s). (3) Pi 2 oscillations in the H (northward) and P (parallel to the earth rotation axis) component exhibited phase (time) difference among them (|ΔT| < ~50s). By taking into

  9. Elements of M-I Coupling in Repetitive Substorm Activity Driven by Interplanetary CMEs

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Sandholt, P. E.

    2014-12-01

    By means of case studies we explore key elements of the magnetosphere-ionosphere current system associated with repetitive substorm activity during persistent strong forcing by ICMEs. Our approach consists of a combination of the magnetospheric and ionospheric perspectives on the substorm activity. The first aspect is the near-Earth plasma sheet with its repetitive excitations of the substorm 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 magnetospheric 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 substorm 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 substorm activity, giving rise to electrojet (AL)-plasma convection (PCN) events

  10. Plasmasphere pulsations observed simultaneously by midlatitude SuperDARN radars, ground magnetometers and THEMIS spacecraft during an auroral substorm

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Shi, X.; Baker, J. B. H.; Frissell, N. A.; Hartinger, M.; Liu, J.

    2015-12-01

    We present simultaneous ground and space-based observations of ultra-low frequency (ULF) pulsations which occurred during an auroral substorm 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 occurred 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 magnetospheric dipolar region.

  11. The energy coupling function and the power generated by the solar wind-magnetosphere dynamo

    NASA Technical Reports Server (NTRS)

    Kan, J. R.; Lee, L. C.; Akasofu, S.-I.

    1980-01-01

    A solar wind parameter epsilon, known as the energy coupling function, has been shown to correlate with the power consumption in the magnetosphere. 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 magnetosphere. This identification not only provides a theoretical basis for the energy coupling function, but also constitutes an observational verification of the solar wind-magnetosphere dynamo along the magnetotail. Moreover, one can now conclude that a substorm results when the dynamo power exceeds 10 to the 18th erg/s.

  12. Features of steady magnetospheric convection

    NASA Technical Reports Server (NTRS)

    Yahnin, A.; Malkov, M. V.; Sergeev, V. A.; Pellinen, R. J.; Aulamo, O.; Vennergstrom, S.; Friis-Christensen, E.; Lassen, K.; Danielsen, C.; Craven, J. D.

    1994-01-01

    The large-scale patterns of ionospheric convection and particle precipitation are described during two intervals of steady magnetospheric convection (SMC) on November 24, 1981. The unique data set used in the analysis includes recordings from the worldwide network of magnetometers and all-sky cameras, global auroral images from the Dynamics Explorer (DE) 1 spacecraft, and particle precipitation data from low-altitude National Oceanic and Atmospheric Administration (NOAA) 6 and NOAA 7 spacecraft. The data show that intense magnetospheric convection continued during more than 10 hours under the steady southward interplanetary magnetic field without any distinct substorm signatures. All data sets available confirmed the stable character of the large-scale magnetospheric configuration during this period. In particular, the magnetic flux threading the polar cap was stable (within 10%) during 3.5 hours of continued DE 1 observations. The dayside cusp was located at an unusually low latitude (70 deg CGL). The nightside auroral pattern consisted of two distinct regions. The diffuse aurora in the equatorward half of the expanded (10 deg wide) auroral oval was well-separated from the bright, active auroral forms found in the vicinity of the poleward boundary of the oval. The twin-vortex convection pattern had no signature of the Harang discontinuity; its nightside 'convection throat' was spatially coincident with the poleward active auroras. This region of the auroral oval was identified as the primary site of the short-lived transient activations during the SMC intervals. The energetic particle observations show that the auroral precipitation up to its high-latitude limit is on closed field lines and that particle acceleration up to greater than 30-keV energy starts close to this limit. The isotropic boundaries of the greater than 30-keV protons and electrons were found close to each other, separating regions of discrete and diffuse precipitation. This suggests that these

  13. Study of a substorm on May 4, 1986

    NASA Astrophysics Data System (ADS)

    Hones, E. W.; Craven, J. D.; Frank, L. A.; Galvin, A. B.; Murphree, J. S.; Elphinstone, R. D.; Elphic, R. C.

    A substorm on May 4, 1986, midway through the PROMIS campaign of coordinated data acquisition, was uniquely well documented. Both in its aspects at earth and in its magnetotail aspects. The expansive phase onset was imaged by the Viking satellite at 20-second time resolution. Most of the expansive phase was also imaged by DE 1 at 6-minute time resolution. ISEE 1 and 2 were near the tail's axis 18.5 R sub e from earth operating at high data rate and data were recorded by several geosynchronous satellites. This multi-satellite study provides evidence that the active substorm aurora occurs at the feet of field lines that map to a magnetic X-line in the near tail. The longitudinal extension of the aurora during a substorm is associated with cross-rail lengthening of the near-earth neutral line. The concept of the poleward leap of the auroral electrojet (and the auroras) as the culminating feature of the expansive phase finds further support in these data.

  14. The Differences in Onset Time of Conjugate Substorms

    NASA Astrophysics Data System (ADS)

    Weygand, J. M.; Zesta, E.; McPherron, R. L.; Hsu, T. S.

    2014-12-01

    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 substorm 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 substorm onsets do not always occur 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 substorms have serious implications for substorm 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.

  15. Low energy electrons in the inner Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Ganushkina, Natalia; Sillanpaa, Ilkka; Dugyagin, Stepan; Pitchford, David; Rodriguez, Juan; Runov, Andrei

    2016-04-01

    The fluxes of electrons with energies < 100 keV are not usually analyzed and modeled in details when studying the electron radiation belts. These fluxes constitute the low energy part of the seed population, which is critically important for radiation belt dynamics. Moreover, energetic electrons with energies less than about 100 keV are responsible for hazardous space-weather phenomena such as surface charging. The electron flux at these energies varies highly with geomagnetic activity and even during quiet-time periods. Significant variations in the low-energy electrons can be seen during isolated substorms, not related to any storm periods. Moreover, electron flux variations depend on the electron energy. Statistical analysis of AMC 12 CEASE II ESA instrument data (5-50 keV) and GOES MAGED data (40, 75, 150 keV) have revealed that electron fluxes increase by the same order of magnitude during isolated substorms with 200 nT of AE index and storm-time substorms with 1200 nT of AE index. If substorms are represented as electromagnetic pulses which transport and accelerate electrons additionally, how are their amplitudes determined, if not related directly to a substorm's strength? Another factor of crucial importance is the specification of boundary conditions in the electron plasma sheet. We developed a new model for electron number density and temperature in the plasma sheet as dependent on solar wind and IMF conditions based on THEMIS data analysis. We present observational and modeling results on low energy electrons in the inner magnetosphere with newly-developed, time-dependent boundary conditions with a special focus on the role of substorms for electron transport and acceleration.

  16. Fundamental Aspects of External Triggers and Non-Triggers of Substorm Particle Injections, and Implications on Sawtooth Events and Repetitive Substorms

    NASA Astrophysics Data System (ADS)

    Lee, D.; Lyons, L.; Reeves, G.

    2005-12-01

    It is important to understand what specific types of solar wind disturbances lead to a substorm and what other specific types do not. The types of solar wind disturbances include a variation in either IMF or dynamic pressure or a combination of simultaneous variations in both. We used observations of geosynchronous particle fluxes at energies of tens to hundreds of keV and found the following features. (1) A northward turning of the IMF is found to trigger the typical substorm injection as well known already. The injection front is wider when it is triggered by a northward turning under a strongly southward IMF condition. (2) The effect by the northward turning can however be cancelled out by a simultaneous increase of the IMF By magnitude and/or a simultaneous decrease of the dynamic pressure, leading to no substorm. (3) Generally a pressure increase leads to a compression effect which appears as flux increase or decrease or even no change, depending on the radial profile of the particle distribution at constant adiabatic invariants. This compression effect can be different between different MLTs and different particle species. (4) However, a pressure increase under strongly southward IMF conditions leads to not only the typical compression effect but also a nightside substorm injection, i.e., a two-mode response. (5) This pressure-induced substorm injection can however be cancelled out by a simultaneous (further) decrease of the already-southward IMF and/or by a simultaneous increase of the IMF By magnitude. (6) In addition, the effects by a simultaneous increase of both IMF Bz and dynamic pressure add up to lead to a substorm injection accompanied by the typical compression effect, while no substorm injection is expected by a pressure decrease or a decrease of the IMF Bz or a simultaneous decrease of both. We suggest that a substorm injection is triggered only by a variation or a combination of variations that results in a convection reduction within the inner

  17. On the role of ground-based observations in substorm research: Can one recognize the beast from its foot prints?

    NASA Astrophysics Data System (ADS)

    Kauristie, K.

    2003-04-01

    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 substorm concept, main parts of which belong also to the wider magnetospheric substorm 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 magnetospheric substorm 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 magnetospheric 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 substorm research, and envisage some of the future challenges.

  18. Physics of Substorm Growth Phase, Onset, and Dipolarization

    SciTech Connect

    C.Z. Cheng

    2003-10-22

    A new scenario of substorm 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 magnetospheric 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 substorm 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.

  19. Multipoint measurements of energetic particles in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Baker, D. N.

    1988-01-01

    The benefits of energetic-particle measurements in the study of magnetospheric physics are reviewed, including the particles' relative ease of detection, their high rectilinear speed, their range of gyroradii, and their immunity to large-scale electric fields. With such particles, it is possible to observationally separate distinctive plasma regions, uniquely assess field-line topologies, examine connectivity from the magnetospheric equator to the ionosphere, and sense global changes in magnetospheric configuration. Multipoint measurements of energetic particles have contributed substantially to the understanding of the earth magnetopause, the leakage of particles into the upstream region, the effect of sudden storm compressions, the global nature of substorm dynamics, and the location and character of high-energy acceleration processes.

  20. Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude

    NASA Astrophysics Data System (ADS)

    Nosé, M.; Iyemori, T.; Wang, L.; Hitchman, A.; Matzka, J.; Feller, M.; Egdorf, S.; Gilder, S.; Kumasaka, N.; Koga, K.; Matsumoto, H.; Koshiishi, H.; Cifuentes-Nava, G.; Curto, J. J.; Segarra, A.; ćElik, C.

    2012-08-01

    Geomagnetic field data with high time resolution (typically 1 s) have recently become more commonly acquired by ground stations. Such high time resolution data enable identifying Pi2 pulsations which have periods of 40-150 s and irregular (damped) waveforms. It is well-known that pulsations of this type are clearly observed at mid- and low-latitude ground stations on the nightside at substorm onset. Therefore, with 1-s data from multiple stations distributed in longitude around the Earth's circumference, substorm onset can be regularly monitored. In the present study we propose a new substorm index, the Wp index (Wave and planetary), which reflects Pi2 wave power at low-latitude, using geomagnetic field data from 11 ground stations. We compare the Wp index with the AE and ASY indices as well as the electron flux and magnetic field data at geosynchronous altitudes for 11 March 2010. We find that significant enhancements of the Wp index mostly coincide with those of the other data. Thus the Wp index can be considered a good indicator of substorm onset. The Wp index, other geomagnetic indices, and geosynchronous satellite data are plotted in a stack for quick and easy search of substorm onset. The stack plots and digital data of the Wp index are available at the Web site (http://s-cubed.info) for public use. These products would be useful to investigate and understand space weather events, because substorms cause injection of intense fluxes of energetic electrons into the inner magnetosphere and potentially have deleterious impacts on satellites by inducing surface charging.

  1. Comprehensive ground-based and in situ observations of substorm expansion phase onset

    NASA Astrophysics Data System (ADS)

    Walsh, A. P.; Rae, J.; Fazakerley, A. N.; Murphy, K. R.; Mann, I. R.; Watt, C. E.; Volwerk, M.; Forsyth, C.; Singer, H. J.; Donovan, E. F.; Zhang, T.

    2010-12-01

    We present comprehensive ground-based and space-based in situ geosynchronous observations of a substorm expansion phase onset on 1 October 2005. The Double Star TC2 and GOES12 spacecraft were both located within the substorm current wedge during the substorm expansion phase onset, which occurred over the Canadian sector. We find that an onset of ULF waves in space was observed after onset on the ground by extending the AWESOME timing algorithm into space. Furthermore a population of low energy field-aligned electrons was detected by the TC2 PEACE instrument contemporaneous with the ULF waves in space. These electrons appear to be associated with an enhancement of field-aligned Poynting flux into the ionosphere which is large enough to power visible auroral displays. The observations are most consistent with a near-Earth initiation of substorm expansion phase onset, such as the Near Geosynchronous Onset (NGO) substorm scenario. A lack of data from further downtail, however, means other mechanisms cannot be ruled out.

  2. Comprehensive ground-based and in situ observations of substorm expansion phase onset

    NASA Astrophysics Data System (ADS)

    Walsh, A. P.; Rae, I. J.; Fazakerley, A. N.; Murphy, K. R.; Mann, I. R.; Watt, C. E. J.; Volwerk, M.; Forsyth, C.; Singer, H. J.; Donovan, E. F.; Zhang, T. L.

    2010-12-01

    In this paper, we present comprehensive ground-based and space-based in situ geosynchronous observations of a substorm expansion phase onset on 1 October 2005. The Double Star TC-2 and GOES-12 spacecraft were both located within the substorm current wedge during the substorm expansion phase onset, which occurred over the Canadian sector. We find that an onset of ULF waves in space was observed after onset on the ground by extending the AWESOME timing algorithm into space. Furthermore, a population of low-energy field-aligned electrons was detected by the TC-2 PEACE instrument contemporaneous with the ULF waves in space. These electrons appear to be associated with an enhancement of field-aligned Poynting flux into the ionosphere which is large enough to power visible auroral displays. The observations are most consistent with a near-Earth initiation of substorm expansion phase onset, such as the Near-Geosynchronous Onset (NGO) substorm scenario. A lack of data from further downtail, however, means other mechanisms cannot be ruled out.

  3. A new technique for determining Substorm Onsets and Phases from Indices of the Electrojet (SOPHIE)

    NASA Astrophysics Data System (ADS)

    Forsyth, C.; Rae, I. J.; Coxon, J. C.; Freeman, M. P.; Jackman, C. M.; Gjerloev, J.; Fazakerley, A. N.

    2015-12-01

    We present a new quantitative technique that determines the times and durations of substorm expansion and recovery phases and possible growth phases based on percentiles of the rate of change of auroral electrojet indices. By being able to prescribe different percentile values, we can determine the onset and duration of substorm phases for smaller or larger variations of the auroral index or indeed any auroral zone ground-based magnetometer data. We apply this technique to the SuperMAG AL (SML) index and compare our expansion phase onset times with previous lists of substorm onsets. We find that more than 50% of events in previous lists occur within 20 min of our identified onsets. We also present a comparison of superposed epoch analyses of SML based on our onsets identified by our technique and existing onset lists and find that the general characteristics of the substorm bay are comparable. By prescribing user-defined thresholds, this automated, quantitative technique represents an improvement over any visual identification of substorm onsets or indeed any fixed threshold method.

  4. Plasmas in Saturn's magnetosphere

    NASA Technical Reports Server (NTRS)

    Frank, L. A.; Burek, B. G.; Ackerson, K. L.; Wolfe, J. H.; Mihalov, J. D.

    1980-01-01

    The solar wind plasma analyzer on board Pioneer 2 provides first observations of low-energy positive ions in the magnetosphere 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 magnetosphere. 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 magnetosphere 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 magnetosphere beyond about 6.5 R sub S, will occur in the local night sector in order to relieve the plasma pressure from accretion of plasma from the rings.

  5. Evolution of auroral acceleration region field-aligned current systems, plasma, and potentials observed by Cluster during substorms

    NASA Astrophysics Data System (ADS)

    Hull, A. J.; Chaston, C. C.; Fillingim, M. O.; Frey, H. U.; Goldstein, M. L.; Bonnell, J. W.; Mozer, F.

    2015-12-01

    The auroral acceleration region is an integral link in the chain of events that transpire during substorms, and the currents, plasma and electric fields undergo significant changes driven by complex dynamical processes deep in the magnetotail. The acceleration processes that occur therein accelerate and heat the plasma that ultimately leads to some of the most intense global substorm auroral displays. Though this region has garnered considerable attention, the temporal evolution of field-aligned current systems, associated acceleration processes, and resultant changes in the plasma constituents that occur during key stages of substorm development remain unclear. In this study we present a survey of Cluster traversals within and just above the auroral acceleration region (≤3 Re altitude) during substorms. Particular emphasis is on the spatial morphology and developmental sequence of auroral acceleration current systems, potentials and plasma constituents, with the aim of identifying controlling factors, and assessing auroral emmission consequences. Exploiting multi-point measurements from Cluster in combination with auroral imaging, we reveal the injection powered, Alfvenic nature of both the substorm onset and expansion of auroral particle acceleration. We show evidence that indicates substorm onsets are characterized by the gross-intensification and filamentation/striation of pre-existing large-scale current systems to smaller/dispersive scale Alfven waves. Such an evolutionary sequence has been suggested in theoretical models or single spacecraft data, but has not been demonstrated or characterized in multispacecraft observations until now. It is also shown how the Alfvenic variations over time may dissipate to form large-scale inverted-V structures characteristic of the quasi-static aurora. These findings suggest that, in addition to playing active roles in driving substorm aurora, inverted-V and Alfvenic acceleration processes are causally linked. Key

  6. Multi-Scale Modeling of Magnetospheric Dynamics

    NASA Technical Reports Server (NTRS)

    Kuznetsova, M. M.; Hesse, M.; Toth, G.

    2012-01-01

    Magnetic reconnection is a key element in many phenomena in space plasma, e.g. Coronal mass Ejections, Magnetosphere substorms. 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 magnetosphere 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 magnetosphere 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 magnetospheric 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 magnetosphere 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

  7. Mercury's Dynamic Magnetosphere: What Have We Learned from MESSENGER?

    NASA Astrophysics Data System (ADS)

    Slavin, James A.

    2016-04-01

    Mercury's magnetosphere 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. Magnetospheric 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 magnetospheric 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 magnetospheric 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 magnetosphere? How does magnetopause reconnection at Mercury differ from what is seen at Earth? Are flux transfer events (FTEs) a major driver of magnetospheric convection at Mercury? Question #3: Does reconnection ever erode the dayside magnetosphere 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 magnetosphere? Question #5: Does Mercury's magnetotail store and dissipate magnetic energy in a manner analogous to substorms 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

  8. Auroral Substorms during Prolonged Northward IMF

    NASA Astrophysics Data System (ADS)

    Du, Aimin

    Multiple observations by satellites and ground-based magnetometers identify the occurrence of substorm events during prolonged northward interplanetary magnetic field (IMF). The func-tion, as an expression of the solar wind energy flow, and the energy dissipation in the ionosphere (UI) are calculated during substorm periods. The delay time of the UI to the function and UI for seven substorm events with AL values of -231 -1500 nT under northward IMF condition are 45 95 min with a mean value of 70.86 min. For comparison, 23 substorm events with the AL index of -316 -1685 nT under southward IMF condition are detected to have the delay time of 21 66 min with a mean value of 42.04 min. The longer delay time for substorms during northward IMF can be presumably attributed to the contribution of IMF By component to merging between IMF and the Earth's magnetic field. A tendency of the decrease of the delay time with increasing absolute values of IMF By is noted. Acknowledgement: This work is supported by NSFC(40774086).

  9. Inferences Concerning the Magnetospheric Source Region for Auroral Breakup

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1992-01-01

    It is argued that the magnetospheric source region for auroral arc breakup and substorm 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 substorm 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.

  10. Magnetospheric Convection as a Global Force Phenomenon

    NASA Astrophysics Data System (ADS)

    Siscoe, G.

    2007-12-01

    Since 1959 when Thomas Gold showed that motions in the magnetosphere were possible despite plasma being frozen to the magnetic field, magnetospheric 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 magnetosphere 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 substorm 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.

  11. DYNAMICS OF STRONGLY TWISTED RELATIVISTIC MAGNETOSPHERES

    SciTech Connect

    Parfrey, Kyle; Beloborodov, Andrei M.; Hui, Lam

    2013-09-10

    Magnetar magnetospheres 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 magnetospheres subjected to slow twisting through large angles. When the twist amplitude is small, the magnetosphere moves quasi-statically through a sequence of equilibria of increasing free energy. At some twist amplitude the magnetosphere 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 magnetosphere beyond the critical angle, allowing the magnetosphere 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 occur 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 magnetospheric twists. A model in which energy is stored in the magnetosphere and released by a magnetospheric instability therefore predicts large changes in the measured spindown rate before soft gamma repeater giant flares.

  12. Substorms and polar cap convection: the 10 January 2004 interplanetary CME case

    NASA Astrophysics Data System (ADS)

    Andalsvik, Y.; Sandholt, P. E.; Farrugia, C. J.

    2012-01-01

    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 substorm activity under steady interplanetary conditions. Substorm 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 substorm 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 magnetosphere-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 substorm activity: CPCP/day ~110 kV; CPCP/night ~50 kV (45% CPCP increase during substorms). The temporal CPCP structure during one of the substorm cases resulted in a dawn-dusk convection asymmetry measured by DMSP F13 which

  13. Lower thermospheric wind variations in auroral patches during the substorm recovery phase

    NASA Astrophysics Data System (ADS)

    Oyama, Shin-ichiro; Shiokawa, Kazuo; Miyoshi, Yoshizumi; Hosokawa, Keisuke; Watkins, Brenton J.; Kurihara, Junichi; Tsuda, Takuo T.; Fallen, Christopher T.

    2016-04-01

    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 substorm recovery phase. Taking into account magnetospheric substorm 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 magnetosphere-ionosphere-thermosphere coupled system at the substorm 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.

  14. Aurora and Magnetospheric Teacher Guides: Bringing Data into the Classroom

    NASA Astrophysics Data System (ADS)

    Peticolas, L. M.; Odenwald, S.; Walker, A.

    2008-06-01

    The NASA missions Fast Auroral SnapshoT (FAST) and Time History of Events and Macroscale Interactions during Substorms (THEMIS) study Earth's aurora and magnetosphere. As part of the THEMIS Education and Public Outreach (EPO) program, magnetometers were placed in twelve schools in ten states in the Northern US where auroras are often or occasionally detected. In order to bring the science of auroras and Earth's magnetosphere and the data associated with these missions, we have created several teacher guides with middle and high school teachers. Many of these teachers were the ones we worked with in the twelve schools with magnetometers. These guides cover a wide array of topics including 1) Earth's magnetic field to create electrical current; 2) Earth's changing magnetic field on timescales of hundreds of thousands of years, hours, and seconds; 3) space weather effects on the magnetosphere and aurora; 4) universal time; 5) the creation of aurora; 5) auroral substorms; 6) the calculation of the total magnetic field at a particular location over months and years; and 7) the prediction of whether or not auroras will be visible using magnetometer data. We will share the review feedback about these guides from both teachers and a NASA review panel and explain what we did to address these suggested changes. From our evaluation results, we will reveal the challenges of bringing data into the classroom as well as the enormous capacity of these missions to inspire students to get involved with data and NASA missions.

  15. Integrated Observations of ICME - Driven Substorm - Storm Evolution on 7 August 1998: Traditional and Non-Traditional Aspects.

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Sandholt, P. E.; Torbert, R. B.

    2015-12-01

    The aim of this study is to obtain an integrated view of substorm-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 substorm activity. Specifically, we report a case study of substorm/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-magnetosphere-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 substorm growth phase (DP2 current) followed by (ii) a classical substorm 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 substorm expansion phase. Magetosphere - Ionosphere (M - I) coupling during a localized electrojet event at 0500 MLT in the late stage of the substorm 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 substorm current wedge morphology.

  16. Large-scale FAC in the nightside magnetosphere: simultaneous observation by Double Star and Cluster

    NASA Astrophysics Data System (ADS)

    Shi, Jiankui; Cheng, Zhengwei; Dunlop, Malcolm; Zhang, Tielong; Liu, Zhenxing

    The data from the coordinated observation of the TC-1, TC-2 and Cluster in the nightside magnetosphere are used for analysis the large scale Field Aligned Current (FAC) along the field lines between the magnetotail and polar ionosphere. Two cases during the substorm times were chosen to do study. One was on the September 14, 2004 and the other was on the September 17, 2004. It is the first time to give a confirmation by observation that the FAC is a lager scale phenomenon from the polar ionosphere to the magnetotail. The results also show that the FAC in the magnetotail just takes place in the Plasma sheet Boundary layers (PSBL). During the whole substorm time, the FAC disturbance has a positive co-relation with the AE index. In the beginning of the substorm, sometime Cluster couldn't observe the FAC in the magnetotail because of the plasma sheet thinning.

  17. Substorm effects in auroral spectra. [electron spectrum hardening

    NASA Technical Reports Server (NTRS)

    Eather, R. H.; Mende, S. B.

    1973-01-01

    A substorm 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 substorm, and it is consistent with the accepted picture of poleward expansion of aurora at the time of substorm and curvature drift of substorm-injected electrons. These features are not evident from a similar analysis in terms of magnetic time. We conclude that the substorm time concept is a useful ordering parameter for auroral data.

  18. Formation of a very thin current sheet in the near-earth magnetotail and the explosive growth phase of substorms

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Zhang, L.; Choe, G. S.; Cai, H. J.

    1995-01-01

    A magnetofricional method is used to construct two-dimensional MHD equilibria of the Earth's magnetosphere 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 substorm. 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 substorms.

  19. Observations of Plasma Transient on the Lobe Field Line During the Substorm. Interball Tail Observations on October 3, 1995

    NASA Technical Reports Server (NTRS)

    Avanov, L. A.; Smimov, V. N.; Chandler, M. O.

    2004-01-01

    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 substorm. 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 magnetosphere caused by the substorm.

  20. Van Allen Probes observations of dipolarization and its associated O+ flux variations in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Nose, M.; Keika, K.; Kletzing, C.; Smith, C. W.; MacDowall, R. J.; Reeves, G. D.; Spence, H. E.

    2015-12-01

    Recent study employing the MDS-1 satellite reveals that magnetic field dipolarization in the deep inner magnetosphere 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 magnetosphere. In this study we investigate magnetic field dipolarization and its associated ion flux variations in the deep inner magnetosphere, 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 magnetosphere (L=3.0-6.6) in VDH coordinates, we select substorm-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 occurs 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

  1. Modeling Substorm Injections with a Simple Magnetotail model

    NASA Astrophysics Data System (ADS)

    Kabin, Konstantin; Spanswick, Emma; Donovan, Eric; Kalugin, German

    2016-07-01

    Magnetotail dipolarizations, often associated with substorms, produce significant energetic particle enhancements in the night-time magnetosphere. We developed a simple yet self-consistent model for the electric and magnetic fields during dipolarizations, which is based on our earlier work (Kabin et al., JGR 2010). This model is very flexible and is particularly well suited for describing transition from the dipole-like to tail-like magnetic fields. We perform test particle simulations in the electric and magnetic fields specified by the model and find substantial energization of both electron and protons associated with the motion of this transition region. This energy gain is sufficient to explain many features of Dispersionless Injections. The energization of the particles is caused by betatron acceleration due to both the local increases in the magnetotail field strength during a dipolarization and to the particles drift closer to the Earth. In some cases the energy of an electron was found to increase by a factor of 25 or more. Our results are particularly well suited for comparison with riometer observations which often show clear signatures of Dispersionless Injections.

  2. Dying Flow Bursts as Generators of the Substorm Current Wedge

    NASA Astrophysics Data System (ADS)

    Haerendel, G.

    2015-12-01

    Many theories or conjectures exist on the driver of the substorm 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 magnetosphere 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.

  3. Dying Flow Bursts as Generators of the Substorm Current Wedge

    NASA Astrophysics Data System (ADS)

    Haerendel, Gerhard

    2016-07-01

    Many theories or conjectures exist on the driver of the substorm 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 magnetosphere 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.

  4. Magnetotail Current Sheet Thinning and Magnetic Reconnection Dynamics in Global Modeling of Substorms

    NASA Technical Reports Server (NTRS)

    Kuznetsova, M. M.; Hesse, M.; Rastaetter, L.; Toth, G.; DeZeeuw, D. L.; Gombosi, T. I.

    2008-01-01

    Magnetotail current sheet thinning and magnetic reconnection are key elements of magnetospheric substorms. 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 magnetospheric 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 magnetospheric substorms. 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

  5. Statistical visualization of the Earth's magnetotail based on Geotail data and the implied substorm model

    NASA Astrophysics Data System (ADS)

    Machida, S.; Miyashita, Y.; Ieda, A.; Nosé, M.; Nagata, D.; Liou, K.; Obara, T.; Nishida, A.; Saito, Y.; Mukai, T.

    2009-03-01

    We investigated the temporal and spatial development of the near-Earth magnetotail during substorms based on multi-dimensional superposed-epoch analysis of Geotail data. The start time of the auroral break-up (t=0) of each substorm 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 substorm onset, and is further enhanced at X~-12 RE (Earth radii) around 4 min before the onset. Simultaneously, large-amplitude fluctuations occurred, 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 substorm. After the substorm 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 substorm 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 substorm 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

  6. Magnetospheric vortices and their global effect after a solar wind dynamic pressure decrease

    NASA Astrophysics Data System (ADS)

    Zhao, H. Y.; Shen, X. C.; Tang, B. B.; Tian, A. M.; Shi, Q. Q.; Weygand, J. M.; Yao, Z. H.; Zong, Q.-G.; Fu, S. Y.; Yao, S. T.; Xiao, T.; Pu, Z. Y.

    2016-02-01

    Using multipoint data from three Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites, we report a magnetospheric flow vortex driven by a negative solar wind dynamic pressure pulse. The observed vortex rotated in a direction opposite to that associated with positive solar wind dynamic pressure pulses. The vortex was moving tailward, as confirmed by a global magnetohydrodynamics (MHD) simulation. In addition, the equivalent ionospheric currents (EICs) deduced from ground magnetometer station data reveal that a current vortex in the ionosphere near the foot point of the satellites has a rotation sense consistent with that observed in the magnetosphere. The field-aligned current (FAC) density estimated from three THEMIS satellites is about 0.15 nA/m2, and the total FAC of the vortex is about 1.5-3 × 105 A, on the order of the total FAC in a pseudobreakup, but less than the total FAC in most moderate substorms, 106 A.

  7. Electric Fields Associated with Deep Injections of 10s to 100s keV Electrons in the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Califf, S.; Li, X.; Jaynes, A. N.; Zhao, H.; Malaspina, D.

    2015-12-01

    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 magnetosphere either through enhancements in the large-scale convection electric field and/or through earthward propagating dipolarization fronts associated with substorms. 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 occur 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 magnetosphere.

  8. Magnetospheres: Jupiter, Satellite Interactions

    NASA Astrophysics Data System (ADS)

    Neubauer, F.; Murdin, P.

    2000-11-01

    Most of the satellites of Jupiter, notably the large Galilean satellites Io, Europa, Ganymede and Callisto (see JUPITER: SATELLITES), orbit deep inside the magnetosphere of Jupiter (see JUPITER: MAGNETOSPHERE) and are therefore immersed in the flow of magnetospheric plasma (made of a mixture of electrons and ions) and subjected to an interaction with the strong Jovian magnetic field. These intera...

  9. Determining pre-onset field magnetotail topology from multi-point magnetospheric and ground-based measurements

    NASA Astrophysics Data System (ADS)

    Rae, J.; Murphy, K. R.; Forsyth, C.; Walsh, A. P.; Waters, C. L.; Mann, I. R.; Taylor, M. G.; Angelopoulos, V.; Carr, C.; Singer, H. J.

    2013-12-01

    The temporal sequence of events at substorm onset requires the generation and propagation of electromagnetic waves as the system evolves from its pre- to post-onset state. Such waves offer a unique diagnostic for the dynamics of this system, and the important coupling between the equatorial magnetosphere and auroral onset dynamics in the ionosphere. ULF waves have been shown to be a pivotal aspect of the substorm onset process, their arrival denoting the epicentre of the magnetic and auroral displays in the ionosphere, however the magnetotail region to which this ULF wave epicentre maps is unknown. Equally, what hinders progress in finding the ionospheric counterpart to magnetospheric features is the uncertainty in mapping high-precision but sparse magnetotail measurements of substorm-related phenomena into the ionosphere. We use ULF waves to diagnose pre-onset magnetic field topology by studying the in-situ eigenfrequencies in the magnetotail using cross-phase techniques. We utilise the new multi-point multi-instrument conjunctions in 2013 from THEMIS, Cluster and GOES and the CARISMA and THEMIS ground-based magnetometer arrays to determine field line eigenfrequencies both on the ground and in at least two separate regions in the near- and mid-tail. The field line eigenfrequencies provide a new way to constrain the location of magnetospheric substorm onset, and provide reliable field line mapping estimates.

  10. Energetic ion and electron phase space densities in the magnetosphere of Uranus

    NASA Astrophysics Data System (ADS)

    Cheng, Andrew F.; Krimigis, S. M.; Mauk, B. H.; Keath, E. P.; Maclennan, C. G.

    1987-12-01

    Voyager 2 low-energy charged particle (LECP) data from the magnetosphere of Uranus have been analyzed to obtain proton and electron phase space density profiles. The Uranus proton profiles show an approximately exponential decline with decreasing radius for L ⪉ 9 in a relatively dense thermal plasma region with intense plasma wave activity. An analogy with the magnetospheres of Earth, Jupiter, and Saturn suggests a plasmasphere at Uranus. The ion flux tube content in the Uranian radiation belt is less than that in the other three cases. Proton and electron profiles are presented and discussed in detail. The magnetosphere of Uranus is the third planetary magnetosphere for which evidence of substorm activity has been adduced, after those of Earth and Mercury.

  11. Dynamic Agents of Magnetosphere-Ionosphere Coupling

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.; Rowland, Douglas E.; Moore, Thomas E.; Collier, Michael

    2011-01-01

    VISIONS sounding rocket mission (VISualizing Ion Outflow via Neutral atom imaging during a Substorm) 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 occurring, 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 substorm 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.

  12. Energy density of ionospheric and solar wind origin ions in the near-Earth magnetotail during substorms

    SciTech Connect

    Daglis, I.A.; Livi, S.; Sarris, E.T.

    1994-04-01

    The authors present a study of hydrogen, oxygen, and helium ions observed in the magnetotail, where measurements of enegy densities were made, and correlated with indexes related to substorm behaviour. The objective is to study relations between the solar wind/magnetosphere/ionosphere. Data were collected using an instrument on the AMPTE/CCE satellite. Strong correlations were observed between different ions and auroral indexes. Energetic ions are found to be increasing in density in the magnetotail in periods when auroral currents are dissipating.

  13. New Understanding of Mercury's Magnetosphere from MESSENGER'S First Flyby

    NASA Technical Reports Server (NTRS)

    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.

    2008-01-01

    Observations by the MESSENGER spacecraft on 14 January 2008 have revealed new features of the solar system's smallest planetary magnetosphere. The interplanetary magnetic field orientation was unfavorable for large inputs of energy from the solar wind and no evidence of magnetic substorms, internal magnetic reconnection, or energetic particle acceleration was detected. Large-scale rotations of the magnetic field were measured along the dusk flank of the magnetosphere 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.

  14. Modeling the Inner-Magnetosphere Ionosphere with the CIMI Model

    NASA Astrophysics Data System (ADS)

    Fok, M. C. H.; Buzulukova, N.; Chen, S. H.; Glocer, A.; Nagai, T.; Valek, P. W.; Perez, J. D.

    2014-12-01

    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-Magnetosphere 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 magnetosphere 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 substorm. 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.

  15. Particle acceleration in pulsar magnetospheres

    NASA Technical Reports Server (NTRS)

    Baker, K. B.

    1978-01-01

    The structure of pulsar magnetospheres and the acceleration mechanism for charged particles in the magnetosphere 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 occur. 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 occurred 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 occur nearer to the surface of the star.

  16. Correlated observations of substorm effects in the near-earth region and the deep magnetotail

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Baumjohann, W.; Baker, D. N.; Bame, S. J.; Gloeckler, G.; Ipavich, F. M.; Smith, E. J.; Tsurutani, B. T.

    1985-01-01

    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 substorm occurred 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 substorm 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 substorm onset, and it indicates a close relationship between processes in the near-earth plasma sheet and the deep tail during substorms.

  17. PC index as a ground-based characteristic for the solar wind energy input into the magnetosphere

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Stauning, Peter

    The solar wind energy input into the magnetosphere is usually evaluated by power of the magnetic disturbances detected at the Earth and estimated by the AE(AL) and Dst indices, characterizing, correspondingly, the magnetospheric substorm and geomagnetic storm dynamics and intensity. It is generally agreed, however, that the magnetospheric substorms and magnetic storms are the result of release of the energy accumulated by that time in the magnetosphere. Theoretical estimations of the solar wind energy input, making allowance for the actually observed solar wind parameters (for example, -function of Akasofu), turned out impracticable on the reasons of their imperfection and impossibility to organize the reliable monitoring the solar wind parameters in the key points of the space. By now the only PC index is serving as an on-line ground-based indicator of the geoeffective solar wind impact on the magnetosphere. The PC index characterizes the polar cap magnetic activity, generated by the geeffective interplanetary electric field (GIEF). The index is derived by magnetic data of only two stations Thule and Vostok, located in the northern (PCN) and southern (PCS) near-pole regions. The index was put into practice about 25 years ago, but obtained his final design as late as 2006. The unified procedure provides the on-line calculation of the PCN and PCS indices consistent with the GIEF value irrespective of the UT time, season and solar cycle. The proper response of the PC index to actual changes in the interplanetary electric field and the solar wind dynamic pressure is demonstrated. The main attention is given to relationships between the PC index behavior and development of the magnetospheric substorms and geomagnetic storms. It is shown that the magnetospheric substorms intensity and the substorm growth phase duration can be predicted by the PC index growth rate, whereas the geomagnetic storms magnitude and their lenght is indicated by the PC values averaged for the

  18. Freja Studies of the Current-Voltage Relation in Substorm-Related Events

    NASA Technical Reports Server (NTRS)

    Olsson, A.; Andersson, Laila; Eriksson, A. I.; Clemmons, J.; Erlandsson, R. E.; Reeves, G.; Hughes, T.; Murphee, J. S.

    2000-01-01

    Field-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere 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 magnetospheric 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 substorm 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 magnetospheric 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 magnetospheric conditions.

  19. ULF Waves above the Nightside Auroral Oval during Substorm Onset

    NASA Astrophysics Data System (ADS)

    Rae, I. J.; Watt, C. E. J.

    2016-02-01

    This chapter reviews historical ground-based observations of ultra-low-frequency (ULF) waves tied to substorms, and highlights new research linking these ULF waves explicitly to substorm 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 substorms. These include the pure state filter, the Hilbert-Huang transform, and wavelet analysis. The first indication of a substorm 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 substorm expansion phase onset. It also discusses a wider range of magnetotail instabilities that could be responsible for the azimuthally structured auroral forms at substorm onset.

  20. Magnetic field fluctuations of THEMIS substorm events

    NASA Astrophysics Data System (ADS)

    Cheng, C. Z.; Chang, T.

    2009-12-01

    We investigate the origin of waves leading to current disruption and dipolarization observed by THEMIS satellites in the near-Earth plasma sheet near substorm expansion onset events on 29 January 2008. Based on the Hilbert-Huang Transform (HHT) technique we analyze the magnetic activity associated with current disruption which shows clearly low frequency fluctuations in the Pi 2 range growing exponentially before the time of magnetic field depolarization and continuing well into the expansion phase. Higher frequency waves are excited at or after the depolarization process starts. These features of magnetic activities are present in almost all three substorm events on January 29, 2008. We identify the low frequency instability as the kinetic ballooning modes destabilized by the free energy associated with the plasma pressure gradient in the bad magnetic field curvature via the wave-particle magnetic drift resonance effect.

  1. Intense energetic-electron flux enhancements in Mercury's magnetosphere: An integrated view with high-resolution observations from MESSENGER

    NASA Astrophysics Data System (ADS)

    Dewey, R. M.; Baker, D. N.; Slavin, J. A.; Raines, J. M.; Lawrence, D. J.; Goldsten, J. O.; Peplowski, P. N.; Korth, H.; Krimigis, S. M.; Anderson, B. J.; Ho, G. C.; McNutt, R. L., Jr.; Schriver, D.; Solomon, S. C.

    2015-12-01

    One of the surprising observations by Mariner 10 during its March 1974 flyby of Mercury was the detection of intense bursts of energetic particles in Mercury's magnetosphere in association with substorm-like magnetic field reconfigurations. A full understanding of where, when, and how such particle bursts occur was not possible from the limited Mariner 10 data. The MESSENGER mission to Mercury has provided a wealth of new data about energetic particle phenomena. With observations from MESSENGER's Energetic Particle Spectrometer (EPS), as well as data arising from energetic electrons recorded by the X-Ray Spectrometer (XRS) and Gamma-Ray and Neutron Spectrometer (GRNS) instruments, recent work has greatly extended our record of the acceleration, transport, and loss of energetic electrons at Mercury. The combined data sets include measurements from a few keV up to several hundred keV in electron kinetic energy and have permitted relatively good spatial and temporal resolution for many events. We focus here on the detailed nature of energetic electron bursts measured by the GRNS system, and we place these events in the context of solar wind and magnetospheric forcing at Mercury. Our examination of data at high temporal resolution (10 ms) during the period March 2013 through October 2014 supports strongly the view that energetic electrons are accelerated in the near-tail region of Mercury's magnetosphere and are subsequently "injected" onto closed magnetic field lines on the planetary night side. The electrons evidently fill the plasma sheet volume and drift rapidly eastward toward the dawn and pre-noon sectors, at time executing multiple complete drifts around the planet to form "quasi-trapped" populations.

  2. Inferences concerning the magnetospheric source region for auroral breakup

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1992-01-01

    Inferences concerning the magnetospheric source region for auroral arcs obtained from particle measurements on polar orbiting satellites are presented and contrasted with other ideas. An argument that the magnetospheric source region for auroral arc breakup and substorm initiation is along Boundary Plasma Sheet (BPS) magnetic field lines is given. This source region lies beyond a distinct central plasma sheet region and sufficiently far from the Earth that energetic ion motion violates the guiding center approximation (is chaotic). The source region is not constrained to any particular range of distances from the Earth, and substorm 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.

  3. Investigation of solar wind and magnetospheric forcing effects on the outer Van Allen belt through multi-point measurements in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Daglis, I. A.; Katsavrias, C.; Georgiou, M.; Turner, D. L.; Sandberg, I.; Balasis, G.; Papadimitriou, K.

    2014-12-01

    We have investigated the response of the outer Van Allen belt electrons to various types of solar wind and internal magnetospheric forcing - in particular to Interplanetary Coronal Mass Ejections (ICMEs), to geospace magnetic storms of different intensities and to intense magnetospheric substorms. We have employed multi-point particle and field observations in the inner magnetosphere (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.

  4. Timing substorm onsets via travel-time magnetoseismology: A case for the outside-in model

    NASA Astrophysics Data System (ADS)

    Chi, Peter; Russell, Christopher; Ohtani, Shin

    The time history of events during substorms is an important, outstanding problem in magnetospheric physics. The sequence has been described either by the "outside-in" model, in which the fast plasma flow ejected by reconnection in the mid-tail moves Earthward, or by the "inside-out" model, in which the onset starts with the cross-tail current sheet collapse at 8 to 12 RE in the tail that later initiates reconnection further downtail. In this study we examined the Pi 2 pulsations observed by ground magnetometers and the observations of auroral brightening to lay out the time history of events during a substorm on July 22, 1998. The arrival time of Pi 2, which refers to the first peak in Pi 2 amplitude, observed by IGPP-LANL and CARISMA magnetometers presents a strong function of latitude. Using the Tamao travel time as the forward model, the inversion from the observed Pi 2 arrival time infers that the onset in the magnetotail started at X = -22 RE at 0653:40 UT, or approximately one minute earlier than the Pi 2 onset time identified in ground data. The CARISMA photometer data at Fort Smith and Gillam show that the auroral brightening started at approximately 0656 UT, or more than two minutes after the estimated onset time in the magnetotail. The comparison between the impulse start time in the tail and the onset time of auroral brightening presents a clear case where the time history of events follows the outside-in model. The model identification is made more confidently by using the magnetoseismic method that can time substorm onsets in the magnetotail.

  5. Generation mechanism of L-value dependence of oxygen flux enhancements during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.

    2015-12-01

    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 substorms. 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 substorms. 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 magnetosphere. We obtained the following results. (1) Just after the substorm 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.

  6. Simulating the Thinning Magnetotail Current Sheet During a Substorm Growth Phase with the Rice Convection Model-Equilibrium

    NASA Astrophysics Data System (ADS)

    Lemon, C. L.; Crabtree, C. E.; Chen, M.; Guild, T. B.

    2015-12-01

    Modeling the progression of the magnetotail configuration during a substorm growth phase is challenging because the current sheet becomes very thin, and is difficult to resolve while keeping the problem computationally tractable. Magnetohydrodynamics (MHD) models have dealt with this problem in various ways, and many claim to be driven by physical rather than numerical considerations. The Rice Convection Model-Equilibrium (RCM-E) is not an MHD model, and has advantages and disadvantages compared to MHD. The notable advantages are the characterization of the full energy distribution of the plasma (including the associated gradient/curvature drift), as well as its generally more comprehensive treatment of the electrodynamics of magnetosphere-ionosphere coupling. The disadvantages include the bounce-averaging of plasma drift, which limits the domain to closed field lines, and the assumption of slow flow relative to the Alfvén speed. The RCM-E has been used in the past to model a substorm growth phase, but its assumptions do not allow it to properly treat the onset mechanism or the formation of x-lines. It can simulate the approach to onset, but is limited by its ability to resolve the thinning current sheet. In this presentation, we present advances in the technique used to calculate the self-consistent magnetic field, which allows us to resolve thinner current sheets than were previously possible. We combine this with a generalized ballooning mode analysis of specific flux tubes in order to assess the stability of the magnetotail to substorm onset.

  7. Magnetospheric Multiscale (MMS) Orbit

    NASA Video Gallery

    This animation shows the orbits of Magnetospheric Multiscale (MMS) mission, a Solar-Terrestrial Probe mission comprising of four identically instrumented spacecraft that will study the Earth's magn...

  8. Electric field evidence for tailward flow at substorm onset

    NASA Technical Reports Server (NTRS)

    Nishida, A.; Tulunay, Y. K.; Mozer, F. S.; Cattell, C. A.; Hones, E. W., Jr.; Birn, J.

    1983-01-01

    Electric field observations made near the neutral sheet of the magnetotail provide additional support for the view that reconnection occurs in the near-earth region of the tail. Southward turnings of the magnetic field that start at, or shortly after, substorm onsets are accompanied by enhancements in the dawn-to-dusk electric field, resulting in a tailward E x B drift velocity. Both the magnetic and the electric fields in the tailward-flowing plasma are nonuniform and vary with inferred spatial scales of several earth radii in the events examined in this paper. These nonuniformities may be the consequence of the tearing-mode process. The E x B flow was also towards the neutral sheet and away from midnight in the events studied.

  9. Simulations of Dynamic Relativistic Magnetospheres

    NASA Astrophysics Data System (ADS)

    Parfrey, Kyle Patrick

    Neutron stars and black holes are generally surrounded by magnetospheres 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 magnetospheres 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 magnetospheres, 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 magnetospheres 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 occurs, involving large-scale rapid magnetic reconnection and dissipation of the free energy of the twisted magnetic field. When the star is rotating, the magnetospheric 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

  10. Near-earth Thin Current Sheets and Birkeland Currents during Substorm Growth Phase

    SciTech Connect

    Sorin Zaharia; C.Z. Cheng

    2003-04-30

    Two important phenomena observed during the magnetospheric substorm 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 substorm 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.

  11. Improved electron and ion temperatures and application to the Nov-24-12 substorm

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Ridley, A. J.

    2014-12-01

    Improved energy equations have been implemented for both electrons and ions in the Global Ionosphere Thermosphere Model (GITM). The sources of the electron temperature include heating due to photoionization, elastic collisions with ions, elastic and inelastic collisions with neutrals, as well as energy fluxes from the magnetosphere. The sources of the ion temperature include elastic collisions with electrons, and energy exchanges with neutrals accounting for Joule heating and due to temperature difference. The model was constructed using a semi-implicit method on the thermal conduction and all of the temperature-dependent source terms [Huba and Joyce, 2000]. The Nov-24-2012 substorm is investigated using the improved model. The Joule heating and its effect on the ion and neutral temperatures in high-latitudes between the improved and basic models are compared. It is also shown that a decrease in the electron temperature exists in the region of the aurora oval with high electron densities. The partitioning of energy between different source terms and loss terms is investigated throughout the substorm and as a function of location.

  12. Substorm effects in MHD and test particle simulations of magnetotail dynamics

    SciTech Connect

    Birn, J.; Hesse, M.

    1998-12-31

    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 substorm 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 magnetosphere 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.

  13. MESSENGER Observations of Extreme Magnetic Tail Loading and Unloading During its Third Flyby of Mercury: Substorms?

    NASA Technical Reports Server (NTRS)

    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.

    2010-01-01

    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 magnetosphere. 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 substorm magnetic flux dynamics, no energetic charged particles with energies greater than 36 keV were observed.

  14. Role of dayside transients in a substorm process: Results from the global kinetic simulation Vlasiator

    NASA Astrophysics Data System (ADS)

    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.

    2015-12-01

    We investigate the dayside-nightside coupling of the magnetospheric dynamics in a global kinetic simulation displaying the entire magnetosphere. 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 magnetospheric 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 substorm

  15. The irregular Pi3 geomagnetic pulsations and its connection with the energetic particles in the magnetosphere and ionosphere

    NASA Astrophysics Data System (ADS)

    Belakhovsky, Vladimir; Pilipenko, Vjacheslav

    2015-04-01

    In this study we investigate the nighttime irregular Pi3 type geomagnetic pulsations generated as during strong single substorms as during sawtooth events using modern satellite (GOES, THEMIS) and ground-based observations (CARISMA, THEMIS, NORSTAR). These pulsations developed during all substorm period but not only during substorm 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 magnetosphere 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 magnetosphere 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 substorm development.

  16. Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data

    NASA Astrophysics Data System (ADS)

    Machida, S.; Miyashita, Y.; Ieda, A.; Nosé, M.; Angelopoulos, V.; McFadden, J. P.

    2014-02-01

    To investigate the physical mechanism responsible for substorm triggering, we performed a superposed-epoch analysis using plasma and magnetic-field data from THEMIS probes. Substorm onset timing was determined based on auroral breakups detected by all-sky imagers at the THEMIS ground-based observatories. We found earthward flows associated with north-south auroral streamers during the substorm growth phase. At around X = -12 Earth radii (RE), the northward magnetic field and its elevation angle decreased markedly approximately 4 min before substorm onset. Moreover, a northward magnetic-field increase associated with pre-onset earthward flows was found at around X = -17 RE. This variation indicates that local dipolarization occurs. Interestingly, in the region earthwards of X = -18 RE, earthward flows in the central plasma sheet (CPS) reduced significantly approximately 3 min before substorm onset, which was followed by a weakening of dawn-/duskward plasma-sheet boundary-layer flows (subject to a 1 min time lag). Subsequently, approximately 1 min before substorm onset, earthward flows in the CPS were enhanced again and at the onset, tailward flows started at around X = -20 RE. Following substorm onset, an increase in the northward magnetic field caused by dipolarization was found in the near-Earth region. Synthesizing these results, we confirm our previous results based on GEOTAIL data, which implied that significant variations start earlier than both current disruption and magnetic reconnection, at approximately 4 min before substorm onset roughly halfway between the two regions of interest; i.e. in the catapult current sheet.

  17. Multiradar observations of substorm-driven ULF waves

    NASA Astrophysics Data System (ADS)

    James, M. K.; Yeoman, T. K.; Mager, P. N.; Klimushkin, D. Yu.

    2016-06-01

    A recent statistical study of ULF waves driven by substorm-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 substorm. Typically, positive azimuthal wave numbers, m, were observed in waves generated to the east of the substorms and negative m to the west. The magnitude of m typically increased with the azimuthal separation between the wave observation and the substorm 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 substorm and lowest farther away. Each of the 83 events studied by James et al. (2013) involved just a single wave observation per substorm. Here a study of three individual substorm events are presented, with associated observations of multiple ULF waves using various different SuperDARN radars. We demonstrate that a single substorm 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 substorm as was seen in the single wave events of James et al. (2013). The variety of wave periods present on similar L shells in this study may also be evidence for the detection of both poloidal Alfvén and drift compressional mode waves driven by substorm-injected particles.

  18. Spatial distribution of magnetic fluctuation power with period 40 to 600 s in the magnetosphere observed by THEMIS

    NASA Astrophysics Data System (ADS)

    Wang, Guoqiang; Zhang, Tielong; Ge, Yasong

    2016-04-01

    Ultralow frequency (ULF) fluctuations are ubiquitous in the magnetosphere and have significant influence on the energetic particle transport. We use Time History of Events and Macroscale Interactions During Substorms (THEMIS) data to give the spatial distribution of the Pi2/Pc4- and Pc5-band magnetic fluctuation amplitude near the magnetic equator in the magnetosphere. Statistical results can be summarized as follows: (1) Strong ULF fluctuations are common in the magnetotail plasma sheet; The amplitude of all three components of magnetic fluctuations decreases with decreasing radial distance; (2) During periods of high AE index, fluctuations can propagate toward the Earth as far as the data cutoff in the nightside of the magnetosphere, and the amplitude of magnetic fluctuations is clearly stronger near the dusk sector of the synchronous orbit than that near the dawn sector, suggesting that the substorm particle injection has significant contribution to these fluctuations; (3) Intense compressional Pc5-band magnetic fluctuations are a persistent feature near two flanks of the magnetosphere. Clear peaks of the compressional Pi2/Pc4-band magnetic fluctuation power near two flanks can be found during periods of fast solar wind, while the power of compressional Pi2/Pc4-band fluctuations is weak when the solar wind is slow. (4) Solar wind dynamic pressure and its variations can globally affect the ULF fluctuation power in the magnetosphere. Magnetic fluctuations near the noon side can penetrate from the magnetopause to the synchronous orbit or inner when solar wind pressure variations are large.

  19. A simulation study of the thermosphere mass density response to substorms using GITM

    NASA Astrophysics Data System (ADS)

    Liu, Xianjing; Ridley, Aaron

    2015-09-01

    The temporal and spatial variations of the thermospheric mass density during a series of idealized substorms were investigated using the Global Ionosphere Thermosphere Model (GITM). The maximum mass density perturbation of an idealized substorm with a peak variation of hemispheric power (HP) of 50 GW and interplanetary magnetic field (IMF) Bz of -2 nT was ~14% about 50 min after the substorm onset in the nightside sector of the auroral zone. The mass density response to different types of energy input has a strong local time dependence, with the mass density perturbation due to only an IMF Bz variation peaking in the dusk sector and the density perturbation due to only HP variation peaks in the nightside sector. Simulations with IMF Bz changes only and HP changes only showed that the system behaves slightly nonlinearly when both IMF and HP variations are included (a maximum of 6% of the nonlinearity) and that the nonlinearity grows with energy input. The neutral gas heating rate due to Joule heating was of same magnitude as the heating rate due to precipitation, but the majority of the temperature enhancement due to the heating due to precipitation occurs at lower altitude as compared to the auroral heating. About 110 min after onset, a negative mass density perturbation (~-5%) occurred in the night sector, which was consistent with the mass density measurement of the CHAMP satellite.

  20. A current disruption mechanism in the neutral sheet for triggering substorm expansions

    NASA Technical Reports Server (NTRS)

    Lui, A. T. Y.; Mankofsky, A.; Chang, C.-L.; Papadopoulos, K.; Wu, C. S.

    1989-01-01

    Two main areas were addressed in support of an effort to understand mechanism responsible for the broadband electrostatic noise (BEN) observed in the magnetotail. The first area concerns the generation of BEN in the boundary layer region of the magnetotail whereas the second area concerns the occassional presence of BEN in the neutral sheet region. For the generation of BEN in the boundary layer region, a hybrid simulation code was developed to perform reliable longtime, quiet, highly resolved simulations of field aligned electron and ion beam flow. The result of the simulation shows that broadband emissions cannot be generated by beam-plasma instability if realistic values of the ion beam parameters are used. The waves generated from beam-plasma instability are highly discrete and are of high frequencies. For the plasma sheet boundary layer condition, the wave frequencies are in the kHz range, which is incompatible with the observation that the peak power in BEN occur in the 10's of Hz range. It was found that the BEN characteristics are more consistent with lower hybrid drift instability. For the occasional presence of BEN in the neutral sheet region, a linear analysis of the kinetic cross-field streaming instability appropriate to the neutral sheet condition just prior to onset of substorm expansion was performed. By solving numerically the dispersion relation, it was found that the instability has a growth time comparable to the onset time scale of substorm onset. The excited waves have a mixed polarization in the lower hybrid frequency range. The imposed drift driving the instability corresponds to unmagnetized ions undergoing current sheet acceleration in the presence of a cross-tail electric field. The required electric field strength is in the 10 mV/m range which is well within the observed electric field values detected in the neutral sheet during substorms. This finding can potentially account for the disruption of cross-tail current and its diversion to

  1. Magnetospheric Image Unfolding

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Grant was a three year grant funded under the Space Physics Supporting Research and Technology and Suborbital Program. Our objective was to develop automated techniques needed to unfold or "invert" global images of the magnetospheric ion populations obtained by the new magnetospheric imaging techniques (ENA, EUV) in anticipation of future missions such as the Magnetospheric Imager and, now, IMAGE. Our focus on the present three year grant is to determine the degree to which such images can quantitatively constrain the global electromagnetic properties of the magnetosphere. In a previous three year grant period we successfully automated a forward modeling inversion algorithm, demonstrated that these inversions are robust in the face of realistic instrumental considerations such as counting statistics and backgrounds, applied error analysis techniques to the extracted parameters using variational procedures, implemented very realistic magnetospheric test images to test the inversion algorithms using the Rice University Magnetospheric Specification Model, and began the process of generating parametric models with the flexibility to handle the realistic magnetospheric images (e.g. Roelof et al, 1992; 1993). Our plan for the present 3 year grant period was to complete the development of the inversion tools needed to handle realistic magnetospheric images, assess the degree to which global electrodynamics is quantitatively constrained by ENA images of the magnetosphere, and bring the inversion of EUV images up to the maturity that we will have achieved for the ENA imaging. Below the accomplishments of our three year effort are present followed by a list of our presentations and publications. The accomplishments of all three years are presented here, and thus some of these items appeared on interim progress reports.

  2. Theory of the auroral magnetosphere

    NASA Technical Reports Server (NTRS)

    Schulz, M.; Chiu, Y. T.; Cornwall, J. M.

    1981-01-01

    The aurora has come to be understood as a manifestation of energy transfer and plasma transfer from the solar wind to the magnetosphere. The auroral oval seems to be a mapping of the boundary layer that lies just inside the magnetospheric surface, which consists of the magnetopause and neutral sheet. The auroral oval is consequently a region of reversal for the meridional (r,8) component of the magnetospheric convection electric field and thus a region of strong shear in the plasma drift velocity field. The velocity shear seems to account for the formation of eddies in the auroral "curtain". Moreover, the Kinematical impedance associated with hot auroral plasma perpendicular electric field across a narrow region of latitude to occur without the formation of a large parallel electric field. The signature of the parallel electric field is such as to produce upgoing ion beams and precipitating electron beams in the PM (afternoon-evening) sector of local time, and to account for the polarity of Region-1 currents as a function of local time.

  3. Saturn's Magnetospheric Cusp: Cassini Observations

    NASA Astrophysics Data System (ADS)

    Jasinski, J. M.; Arridge, C. S.; Sergis, N.; Coates, A. J.; Jones, G. H.

    2015-12-01

    The first in-situ analysis of the high-latitude magnetospheric cusp region at Saturn is presented using data from the Cassini spacecraft. The cusp is a funnel-shaped region where shocked solar wind plasma is able to enter the magnetosphere via the process of magnetic reconnection. The analysis is presented in three sections: Firstly, a high-latitude spacecraft trajectory is shown to cross the northern cusp where magnetosheath plasma is observed in-situ. The ion observations are shown to be a result of `bursty' reconnection occurring at the dayside magnetopause. A different interval is also presented where the southern cusp is observed to oscillate with a period the same as Saturn's rotational period. Secondly, the locations of all the cusp crossings are shown. The field-aligned distances (calculated from observed ion energy-pitch angle dispersions) from the reconnection site are presented. The cusp events are also compared to solar wind propagation models to investigate any correlations. Finally, the magnetic field observations of the cusps are analysed focusing on the diamagnetic depressions. The data are subtracted from a magnetic field model, and the calculated magnetic pressure deficits are compared to the particle pressures. A high plasma pressure layer in the magnetosphere adjacent to the cusp is discovered to also depress the magnetic field.

  4. Magnetospheric-ionospheric Poynting flux

    NASA Technical Reports Server (NTRS)

    Thayer, Jeffrey P.

    1994-01-01

    Over the past three years of funding SRI, in collaboration with the University of Texas at Dallas, has been involved in determining the total electromagnetic energy flux into the upper atmosphere from DE-B electric and magnetic field measurements and modeling the electromagnetic energy flux at high latitudes, taking into account the coupled magnetosphere-ionosphere system. This effort has been very successful in establishing the DC Poynting flux as a fundamental quantity in describing the coupling of electromagnetic energy between the magnetosphere and ionosphere. The DE-B satellite electric and magnetic field measurements were carefully scrutinized to provide, for the first time, a large data set of DC, field-aligned, Poynting flux measurement. Investigations describing the field-aligned Poynting flux observations from DE-B orbits under specific geomagnetic conditions and from many orbits were conducted to provide a statistical average of the Poynting flux distribution over the polar cap. The theoretical modeling effort has provided insight into the observations by formulating the connection between Poynting's theorem and the electromagnetic energy conversion processes that occur in the ionosphere. Modeling and evaluation of these processes has helped interpret the satellite observations of the DC Poynting flux and improved our understanding of the coupling between the ionosphere and magnetosphere.

  5. The magnetosphere of Saturn

    NASA Technical Reports Server (NTRS)

    Schardt, A. W.

    1982-01-01

    Information about the magnetosphere of Saturn is provided: the magnetic dipole moment is axisymmetric, the bow shock stand-off distance is about 22 R sub S. The satellites Titan, Dione, and Tethys are probably the primary sources of magnetospheric plasma. Outside of approx. 4 R sub S, energetic particles are energized by diffusing inward while conserving their first and second adiabatic invariants. Particles are lost by satellite sweep-out, absorption byt the E ring and probably also by plasma interactions. The inner magnetosphere is characterized.

  6. Response of northern winter polar cap to auroral substorms

    NASA Astrophysics Data System (ADS)

    Liou, Kan; Sotirelis, Thomas

    2016-05-01

    The three-phase substorm sequence has been generally accepted and is often tied to the Dungey cycle. Although previous studies have mostly agreed on the increase and decrease in the polar cap area during an episode of substorm, there are disparate views on when the polar cap starts to contract relative to substorm onset. Here we address this conflict using high-resolution (~1-3 min) snapshot global auroral images from the ultraviolet imager on board the Polar spacecraft. On the basis of 28 auroral substorm events, all observed in the Northern Hemispheric winter, it is found that the polar cap inflated prior to onset in all events and it attained the largest area ~6 min prior to the substorm expansion phase onset, while the dayside polar cap area remained steady around the onset. The onset of nightside polar cap deflation is found to be attributed to intensifications of aurora on the poleward edge of the nightside oval, mostly in the midnight sector. Although this result supports the loading-unloading and reconnection substorm models, it is not clear if the initial polar cap deflation and the substorm expansion are parts of the same process.

  7. 0.5-4 Å X-RAY BRIGHTENINGS IN THE MAGNETOSPHERE OBSERVED BY THE GEOSTATIONARY OPERATIONAL ENVIRONMENTAL SATELLITES

    SciTech Connect

    Yamamoto, Tetsuya T.; Miyoshi, Y.

    2013-10-01

    We found 217 X-ray brightening events in Earth's magnetosphere. These events occur in the high-energy band (0.5-4 Å) of the Geostationary Operational Environmental Satellite (GOES) X-ray light curves, although GOES X-ray light curves are frequently used as indices of solar flare magnitudes. We found that (1) brightening events are absent in the low-energy band (1-8 Å), unlike those associated with solar flares; and (2) the peak fluxes, durations, and onset times of these events depend on the magnetic local time (MLT). The events were detected in 2006, 2010, and 2011 at around 19-10 MLT, that is, from night to morning. They typically lasted for 2-3 hr. Their peak fluxes are less than 3 × 10{sup –8} W m{sup –2} in the 0.5-4 Å band and are maximized around 0-5 MLT. From these MLT dependencies, we constructed an MLT time profile of X-ray brightening events. Because 0.5-4 and 1-8 Å fluxes were observed and had the same order of magnitude when GOES 14 passed through Earth's shadow, we expected that X-ray brightening events in the 1-8 Å band are obscured by high-background X-ray fluxes coming from the Sun. We also found coincidence between X-ray brightening events and aurora substorms. In the majority of our events, the minimum geomagnetic field values (AL index) are below –400 nT. From these results and consideration of the GOES satellite orbit, we expect that these X-ray brightening events occur in the magnetosphere. We cannot, however, clarify the radiative process of the observed X-ray brightening events.

  8. Energy storage and dissipation in the magnetotail during substorms. 2. MHD simulations

    SciTech Connect

    Steinolfson, R.S. ); Winglee, R.M. )

    1993-05-01

    The authors present a global MHD simulation of the magnetotail in an effort to study magnetic storm development. They address the question of energy storage in the current sheet in the early phases of storm growth, which previous simulations have not shown. They address this problem by dealing with the variation of the resistivity throughout the magnetosphere. They argue that MHD theory should provide a suitable representation to this problem on a global scale, even if it does not handle all details adequately. For their simulation they use three different forms for the resistivity. First is a uniform and constant resistivity. Second is a resistivity proportional to the current density, which is related to argument that resistivity is driven by wave-particle interactions which should be strongest in regions where the current is the greatest. Thirdly is a model where the resistivity varies with the magnetic field strength, which was suggested by previous results from particle simulations of the same problem. The simulation then gives approximately the same response of the magnetosphere for all three of the models. Each results in the formation and ejection of plasmoids, but the energy stored in the magnetotail, the timing of substorm onset in relation to the appearance of a southward interplanetary magnetic field, and the speed of ejection of the plasmoids formed differ with the resistivity models.

  9. Inferring the energy density in the tail as a function of the interplanetary conditions during the growth phase of substorms

    NASA Astrophysics Data System (ADS)

    Jacquey, C.; Sauvaud, J.; Budnik, E.; Hitier, R.

    2006-12-01

    The expansion phase corresponds to the dissipative phase of substorm and typically lasts for 30~45 minutes. During the expansion phase, a large amount of energy is explosively dissipated into the inner magnetosphere and the ionosphere. This energy originally coming from the solar wind via its electromagnetic coupling with the magnetosphere is firstly stored in the tail during the growth phase lasting for 1~3 hours.In this paper, we present case studies and preliminary statistical analysis based on the simultaneous measurements obtained both in the solar wind by IMP-8 and in the tail lobes by the pair of the ISEE 1/2 probes. We show that the tail energy density temporal profiles can be reproduced with the help of a model taking into account the pressure balance at the magnetopause and the storage of input energy from the solar wind. We analyse the changes of the values of the model parameters in regards of the interplanetary conditions, the geomagnetic activity and the observation location. We also study the radial gradient of the tail energy density by comparing the results obtained by the model and by the multi-point analysis of the ISEE 1/2 measurements. The implications of these results in substorm and magnetospheric field models are discussed. We finally present the methodology envisioned for extending in a semi-automated way this study to a vast database including the data obtained in the tail by ISEE 1/2, AMPTE-IRM, GEOTAIL, INTERBALL, CLUSTER and the up-coming THEMIS mission and in the solar wind by IMP-8, WIND and ACE.

  10. Enabling Breakthrough Kinetic Simulations of the Magnetosphere Using Petascale Computing

    NASA Astrophysics Data System (ADS)

    Vu, H. X.; Karimabadi, H.; Omelchenko, Y.; Tatineni, M.; Majumdar, A.; Krauss-Varban, D.; Dorelli, J.

    2009-12-01

    Currently global magnetospheric simulations are predominantly based on single-fluid magnetohydrodynamics (MHD). MHD simulations have proven useful in studies of the global dynamics of the magnetosphere with the goal of predicting eminent features of substorms and other global events. But it is well known that the magnetosphere is dominated by ion kinetic effects, which is ignored in MHD simulations, and many key aspects of the magnetosphere relating to transport and structure of boundaries await global kinetic simulations. We are using our recent innovations in hybrid (electron fluid, kinetic ions) simulations, as being developed in our Hybrid3D (H3D) code, and the power of massively parallel machines to make, breakthrough 3D global kinetic simulations of the magnetosphere. The innovations include (i) multi-zone (asynchronous) algorithm, (ii) dynamic load balancing, and (iii) code adaptation and optimization to large number of processors. In this presentation we will show preliminary results of our progress to date using from 512 to over 8192 cores. In particular, we focus on what we believe to be the first demonstration of the formation of a flux rope in 3D global hybrid simulations. As in the MHD simulations, the resulting flux rope has a very complex structure, wrapping up field lines from different regions and appears to be connected on at least one end to Earth. Magnetic topology of the FTE is examined to reveal the existence of several separators (3D X-lines). The formation and growth of this structure will be discussed and spatial profile of the magnetic and plasma variables will be compared with those from MHD simulations.

  11. Ionospheric and magnetospheric plasmapauses'

    NASA Technical Reports Server (NTRS)

    Grebowsky, J. M.; Hoffman, J. H.; Maynard, N. C.

    1977-01-01

    During August 1972, Explorer 45 orbiting near the equatorial plane with an apogee of about 5.2 R sub e traversed magnetic field lines in close proximity to those simultaneously traversed by the topside ionospheric satellite ISIS 2 near dusk in the L range 2-5.4. The locations of the Explorer 45 plasmapause crossings during this month were compared to the latitudinal decreases of the H(+) density observed on ISIS 2 near the same magnetic field lines. The equatorially determined plasmapause field lines typically passed through or poleward of the minimum of the ionospheric light ion trough, with coincident satellite passes occurring for which the L separation between the plasmapause and trough field lines was between 1 and 2. Vertical flows of the H(+) ions in the light ion trough as detected by the magnetic ion mass spectrometer on ISIS were directed upward with velocities between 1 and 2 kilometers/sec near dusk on these passes. These velocities decreased to lower values on the low latitude side of the H(+) trough but did not show any noticeable change across the field lines corresponding to the magnetospheric plasmapause.

  12. Plasma and magnetospheric research

    NASA Technical Reports Server (NTRS)

    Comfort, R. H.; Horwitz, J. L.

    1985-01-01

    Research and development in plasmas and magnetospheric environments is reported. Topics discussed include: analysis and techniques of software development; data analysis and modeling; spacecraft sheath effects; laboratory plasma flow studies; instrument development.

  13. Magnetospheric polar cap

    NASA Astrophysics Data System (ADS)

    Akasofu, S. I.; Kan, J. R.

    Mount Denali (McKinley), the Alaska Range, and countless glaciers welcomed all 86 participants of the Chapman Conference on the Magnetospheric Polar Cap, which was held on the University of Alaska, Fairbanks campus (UAF), on August 6-9, 1984. The magnetospheric polar cap is the highest latitude region of the earth which is surrounded by the ring of auroras (the auroral oval). This particular region of the earth has become a focus of magnetospheric physicists during the last several years. This is because a number of upper atmospheric phenomena in the polar cap are found to be crucial in understanding the solar wind—magnetosphere interaction. The conference was opened by J. G. Roederer, who was followed by the UAF Chancellor, P. J. O'Rourke, who officially welcomed the participants.

  14. LANL Studies Earth's Magnetosphere

    ScienceCinema

    Daughton, Bill

    2016-07-12

    A new 3-D supercomputer model presents a new theory of how magnetic reconnection works in high-temperature plasmas. This Los Alamos National Laboratory research supports an upcoming NASA mission to study Earth's magnetosphere in greater detail than ever.

  15. Solar and magnetospheric science

    NASA Technical Reports Server (NTRS)

    Timothy, A. F.; Schmerling, E. R.; Chapman, R. D.

    1976-01-01

    The current status of the Solar Physics Program and the Magnetospheric Physics Program is discussed. The scientific context for each of the programs is presented, then the current programs and future plans are outlined.

  16. LANL Studies Earth's Magnetosphere

    SciTech Connect

    Daughton, Bill

    2011-04-15

    A new 3-D supercomputer model presents a new theory of how magnetic reconnection works in high-temperature plasmas. This Los Alamos National Laboratory research supports an upcoming NASA mission to study Earth's magnetosphere in greater detail than ever.

  17. A comparison of the probability distribution of observed substorm magnitude with that predicted by a minimal substorm model

    NASA Astrophysics Data System (ADS)

    Morley, S. K.; Freeman, M. P.; Tanskanen, E. I.

    2007-11-01

    We compare the probability distributions of substorm magnetic bay magnitudes from observations and a minimal substorm model. The observed distribution was derived previously and independently using the IL index from the IMAGE magnetometer network. The model distribution is derived from a synthetic AL index time series created using real solar wind data and a minimal substorm model, which was previously shown to reproduce observed substorm waiting times. There are two free parameters in the model which scale the contributions to AL from the directly-driven DP2 electrojet and loading-unloading DP1 electrojet, respectively. In a limited region of the 2-D parameter space of the model, the probability distribution of modelled substorm bay magnitudes is not significantly different to the observed distribution. The ranges of the two parameters giving acceptable (95% confidence level) agreement are consistent with expectations using results from other studies. The approximately linear relationship between the two free parameters over these ranges implies that the substorm magnitude simply scales linearly with the solar wind power input at the time of substorm onset.

  18. Principal component analysis of Birkeland currents determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Carter, J. A.; Korth, H.; Anderson, B. J.

    2015-12-01

    Principal component analysis is performed on Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment. Principal component analysis (PCA) identifies the patterns in the FACs that respond coherently to different aspects of geomagnetic activity. The regions 1 and 2 current system is shown to be the most reproducible feature of the currents, followed by cusp currents associated with magnetic tension forces on newly reconnected field lines. The cusp currents are strongly modulated by season, indicating that their strength is regulated by the ionospheric conductance at the foot of the field lines. PCA does not identify a pattern that is clearly characteristic of a substorm current wedge. Rather, a superposed epoch analysis of the currents associated with substorms demonstrates that there is not a single mode of response, but a complicated and subtle mixture of different patterns.

  19. Principle Component Analysis of Birkeland Currents Determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Carter, J. A.; Korth, H.; Anderson, B. J.

    2015-12-01

    Principle Component Analysis is performed on northern and southern hemisphere Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). PCA identifies the patterns in the FACs that respond coherently to different aspects of geomagnetic activity. The region 1 and 2 current system is shown to be the most reproducible feature of the currents, followed by cusp currents associated with magnetic tension forces on newly-reconnected field lines. The cusp currents are strongly modulated by season, indicating that their strength is regulated by the ionospheric conductance at the foot of the field lines. PCA does not identify a pattern that is clearly characteristic of a substorm current wedge. Rather, a superposed epoch analysis of the currents associated with substorms demonstrates that there is not a single mode of response, but a complicated and subtle mixture of different patterns. Other interhemispheric differences are discussed.

  20. Transient composite electric field disturbances near dip equator associated with auroral substorms

    SciTech Connect

    Hanumath Sastri, J.; Ramesh, K.B.; Ranganath Rao, H.N. )

    1992-07-24

    Ionosonde data of Kodaikanal and Huancayo are used to show the simultaneous occurrence of a transient disturbance in F region height of composite polarity in day and night sectors near the dip equator during the auroral substorm activity on 20 August 1979. At Kodaikanal which is on the nightside at the time of the substorm activity, h[prime]F first underwent an abrupt and rapid decrease (80km in 1 hr) followed by a much larger increase (120km in 1 hr). Perturbation in hpF2 of exactly opposite polarity was simultaneously seen at Huancayo which is on the dayside. The decrease in h[prime]F at Kodaikana (increase in hpF2 at Huancayo) occurred in association with an increase in polar cap potential drop, [phi] (estimated from IMF parameters), and the subsequent increase (decrease at Huancayo) with a decrease in polar cap potential. The F-region height disturbance is interpreted as the manifestation of a global transient composite disturbance in equatorial zonal electric field caused by the prompt penetration of substorm-related high latitude electric fields into the equatorial ionosphere. The polarity pattern of the electric field disturbance is consistent with the global convection models which predict westward (eastward) electric fields at night (by day) near the geomagnetic equator in response to an increase in polar cap potential drop, and fields of opposite signs for a decrease in polar cap potential.

  1. Particle scattering and current sheet stability in the geomagnetic tail during the substorm growth phase

    SciTech Connect

    Pulkkinen, T.I.; Pellinen, R.J.; Koskinen, H.E.J. ); Baker, D.N. ); Buechner, J. ); Lopez, R.E. ); Dyson, R.L.; Frank, L.A. )

    1992-12-01

    The degree of pitch angle scattering and chaotization of various particle populations in the geomagnetic tail during the substorm growth phase is studied by utilizing the Tsyganenko 1989 magnetic field model. A temporally evolving magnetic field model for the growth phase is constructed by enhancing the near-Earth currents and thinning the current sheet from the values given by the static Tsyganenko model. Changing the field geometry toward an increasingly taillike configuration leads to pitch angle scattering of particles whose Larmor radii become comparable to the field line radius of curvature. Several different cases representing substorms with varying levels of magnetic disturbance have been studied. In each case, the field development during the growth phase leads to considerable scattering of the thermal electrons relatively close to the Earth. The current sheet regions where the electron motion is chaotic are magnetically mapped to the ionosphere and compared with low-altitude measurements of electron precipitation. The chaotization of the thermal electron population occurs within a few minutes of the substorm onset, and the ionospheric mappings of the chaotic regions in the equatorial plane compare well with the region of brightening auroras. Even though the temporal evolution of the complex plasma system cannot be self-consistently described by the temporal evolution of the empirical field model, these models can provide the most accurate estimates of the field parameters for tail stability calculations.

  2. From the Sun to the Earth: impact of the 27-28 May 2003 solar events on the magnetosphere, ionosphere and thermosphere

    NASA Astrophysics Data System (ADS)

    Hanuise, C.; Cerisier, J. C.; Auchère, F.; Bocchialini, K.; Bruinsma, S.; Cornilleau-Wehrlin, N.; Jakowski, N.; Lathuillère, C.; Menvielle, M.; Valette, J.-J.; Vilmer, N.; Watermann, J.; Yaya, P.

    2006-03-01

    During the last week of May 2003, the solar active region AR 10365 produced a large number of flares, several of which were accompanied by Coronal Mass Ejections (CME). Specifically on 27 and 28 May three halo CMEs were observed which had a significant impact on geospace. On 29 May, upon their arrival at the L1 point, in front of the Earth's magnetosphere, two interplanetary shocks and two additional solar wind pressure pulses were recorded by the ACE spacecraft. The interplanetary magnetic field data showed the clear signature of a magnetic cloud passing ACE. In the wake of the successive increases in solar wind pressure, the magnetosphere became strongly compressed and the sub-solar magnetopause moved inside five Earth radii. At low altitudes the increased energy input to the magnetosphere was responsible for a substantial enhancement of Region-1 field-aligned currents. The ionospheric Hall currents also intensified and the entire high-latitude current system moved equatorward by about 10°. Several substorms occurred during this period, some of them - but not all - apparently triggered by the solar wind pressure pulses. The storm's most notable consequences on geospace, including space weather effects, were (1) the expansion of the auroral oval, and aurorae seen at mid latitudes, (2) the significant modification of the total electron content in the sunlight high-latitude ionosphere, (3) the perturbation of radio-wave propagation manifested by HF blackouts and increased GPS signal scintillation, and (4) the heating of the thermosphere, causing increased satellite drag. We discuss the reasons why the May 2003 storm is less intense than the October-November 2003 storms, although several indicators reach similar intensities.

  3. Comparison of substorms near two solar cycle maxima: (1999-2000 and 2012-2013)

    NASA Astrophysics Data System (ADS)

    Despirak, I.; Lubchich, A.; Kleimenova, N.

    2016-05-01

    We present the comparative analysis of the substorm behavior during two solar cycle maxima. The substorms, observed during the large solar cycle maximum (1999- 2000, with Wp> 100) and during the last maximum (2012-2013 with Wp~60), were studied. The considered substorms were divided into 3 types according to auroral oval dynamic. First type - substorms which are observed only at auroral latitudes ("usual" substorms); second type - substorms which propagate from auroral latitudes (<70?) to polar geomagnetic latitudes (>70°) ("expanded" substorms, according to expanded oval); third type - substorms which are observed only at latitudes above ~70° in the absence of simultaneous geomagnetic disturbances below 70° ("polar" substorms, according to contracted oval). Over 1700 substorm events have been analyzed. The following substorm characteristics have been studied: (i) the seasonal variations, (ii) the latitudinal range of the occurrence, (iii) solar wind and IMF parameters before substorm onset, (iiii) PC-index before substorm onset. Thus, the difference between two solar activity maxima could be seen in the difference of substorm behavior in these periods as well.

  4. Ground-based and satellite observations of substorm onset features

    NASA Astrophysics Data System (ADS)

    Chang, T.; Cheng, C. Z.; Chiang, C.; Tam, S. W.; Chen, A. B.; Hsu, R.; Su, H.

    2009-12-01

    We present the ground-based and satellite observations of substorm onset events. In the observations from Ground Based Observatories (GBO) and the ISUAL/FORMOSAT-2 satellite, we find structures which consist of periodic bright spots on the auroral arc prior to the substorm expansion phase onset. The intensity of arc grows exponentially before breakup with a linear growth rate of ~O(1-3)sec-1. Under the arc, the negative H-bay associated with the substorm is evident in the ground-based magnetometer data. From ISUAL observations, the first auroral brightening is identified roughly at the beginning of the negative H-bay. The auroral arc is breaks up before dispersionless particle injections are observed at geosynchronous orbit. Based on analysis of these observations, we suggest that this event can be a support of the scenario of substorm onset which is caused by a kinetic ballooning instability which is localized at ~ -10RE.

  5. Using Global Simulations of the Magnetosphere for Multi-Satellite Mission Planning and Data Analysis

    NASA Technical Reports Server (NTRS)

    Raeder, Joachim; Angelopoulos, Vassilis

    1998-01-01

    We use global simulations of Earth's magnetosphere to assess the scientific return from a multi-satellite mission in the magnetosphere. We examine 4 different scenarios with 20, 40, 80, and 160 satellites, respectively. The satellite orbits are randomized with perigee distances ranging from 2 to 5R(sub E), apogee distances between 10 and 50 R(sub E), and within +/-5R(sub E) of the geocentric solar ecliptic (GSE) equator. For each of these satellite configurations we examine the expected observations during a typical substorm by using time traces obtained from a global simulation at the satellite positions. The 160 satellite configuration yields sufficient information to distinguish between different substorm models without any temporal/spatial ambiguities. An 80 satellite configuration still provides sufficient information for this task, however for fewer events with good satellite conjunctions and with less statistical certainty. For constellations with fewer than 40 satellites time-space ambiguities are likely to remain in the observation. However, any multi-satellite constellation would be a quantum leap in magnetospheric research because of the unprecedented coverage of other regions, because it would enable new measurement techniques that are unique to multi-satellite missions, and because it would enable the use of data assimilation techniques in global models for the first time.

  6. Nonlinear, relativistic Langmuir waves in astrophysical magnetospheres

    NASA Technical Reports Server (NTRS)

    Chian, Abraham C.-L.

    1987-01-01

    Large amplitude, electrostatic plasma waves are relevant to physical processes occurring in the astrophysical magnetospheres wherein charged particles are accelerated to relativistic energies by strong waves emitted by pulsars, quasars, or radio galaxies. The nonlinear, relativistic theory of traveling Langmuir waves in a cold plasma is reviewed. The cases of streaming electron plasma, electronic plasma, and two-streams are discussed.

  7. Storm/substorm signatures in the outer belt

    SciTech Connect

    Korth, A.; Friedel, R.H.W.; Mouikis, C.; Fennell, J.F.

    1998-12-01

    The response of the ring current region is compared for periods of storm and substorm activity, with an attempt to isolate the contributions of both processes. The authors investigate CRRES particle data in an overview format that allows the display of long-term variations of the outer radiation belt. They compare the evolution of the ring current population to indicators of storm (Dst) and substorm (AE) activity and examine compositional changes. Substorm activity leads to the intensification of the ring current at higher L (L {approximately} 6) and lower ring current energies compared to storms (L {approximately} 4). The O{sup +}/H{sup +} ratio during substorms remains low, near 10%, but is much enhanced during storms (can exceed 100%). They conclude that repeated substorms with an AE {approximately} 900 nT lead to a {Delta}Dst of {approximately} 30 nT, but do not contribute to Dst during storm main phase as substorm injections do not form a symmetric ring current during such disturbed times.

  8. Unusual satellite-electron signature within the Uranian magnetosphere and its implications regarding whistler electron loss processes

    NASA Technical Reports Server (NTRS)

    Mauk, B. H.; Keath, E. P.; Krimigis, S. M.

    1994-01-01

    It has been reported that during the outbound (nightside) portion of the Voyager 2 encounter with the Uranian magnetosphere, intense whistler mode emissions were observed near the magnetic equator (lambda(sub m) approx. 16 deg) and at L shell values between approx. 5.5 and approx. 9 R(sub U). Comprehensive calculations of whistler-driven pitch angle diffusion, in previous work, have yielded strong diffusion electron lifetimes of approx. 1 hour for 20 to 40 keV electrons. In this paper we report on an unusual and sharply defined charged particle feature that: (1) involved electrons between 22 and 35 keV, (2) was observed during the time period of the intense whistler mode observations, (3) was aligned very accurately and sharply with the minimum L shell position (L approx. 7.5) of the satellite Ariel, and (4) has an appearance that suggests that electrons were removed only at and beyond Ariel's minimum-L. On the basis of our conclusion that the signature was caused by electron interactions with either Ariel or materials distributed along Ariel's orbit, the signature could not have been generated for at least 10 hours prior to its observation. Thus the calculated whistler loss times are in apparent conflict with the signature observation. A scenario of events is proposed to explain the data that involves substormlike electron acceleration on the Uranian nightside and a subsequent sculpting of the electron spatial distributions via interactions with Ariel or materials distributed along Ariel's orbit. The possibility exists that the accurate alignment of the sharp electron feature with Ariel's minimum-L, and the absorptionlike character of the feature, are accidental, and that the feature is caused by dynamical processes (e.g., substorms). In this case the dynamical processes must be quite dissimilar to those occurring in the Earth's magnetosphere.

  9. Global electric field determination in the Earth's outer magnetosphere using energetic charged particles

    NASA Technical Reports Server (NTRS)

    Eastman, Timothy E.; Sheldon, R.; Hamilton, D.

    1995-01-01

    Although many properties of the Earth's magnetosphere have been measured and quantified in the past 30 years since it was discovered, one fundamental measurement (for zeroth order MHD equilibrium) has been made infrequently and with poor spatial coverage - the global electric field. This oversight is due in part to the neglect of theorists. However, there is renewed interest in the convection electric field because it is now realized to be central to many magnetospheric processes, including the global MHD equilibrium, reconnection rates, Region 2 Birkeland currents, magnetosphere ionosphere coupling, ring current and radiation belt transport, substorm injections, and several acceleration mechanisms. Unfortunately the standard experimental methods have not been able to synthesize a global field (excepting the pioneering work of McIlwain's geostationary models) and we are left with an overly simplistic theoretical field, the Volland-Stern electric field model. Single point measurements of the plasmapause were used to infer the appropriate amplitudes of this model, parameterized by K(sub p). Although this result was never intended to be the definitive electric field model, it has gone nearly unchanged for 20 years. The analysis of current data sets requires a great deal more accuracy than can be provided by the Volland-Stern model. The variability of electric field shielding has not been properly addressed although effects of penetrating magnetospheric electric fields has been seen in mid-and low-latitude ionospheric data sets. The growing interest in substorm dynamics also requires a much better assessment of the electric fields responsible for particle injections. Thus we proposed and developed algorithms for extracting electric fields from particle data taken in the Earth's magnetosphere. As a test of the effectiveness of these new techniques, we analyzed data taken by the AMPTE/CCE spacecraft in equatorial orbit from 1984 to 1989.

  10. SMILE - New mission to image the magnetosphere

    NASA Astrophysics Data System (ADS)

    Escoubet, C.-Philippe; Wang, Chi; Branduardi-Raymont, Graziella; Sembay, Steve; Dai, Lei; Li, Lei; Donovan, Eric; Spanswick, Emma; Sibeck, David; Read, Andy; Rebuffat, Denis; Wielders, Arno; Zheng, Jianhua; Romstedt, Jens; Raab, Walfried; Lumb, David

    2016-04-01

    Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a novel self-standing mission to be jointly developed between ESA and the Chinese Academy of Sciences (CAS). It will observe the solar wind-magnetosphere coupling via simultaneous in situ solar wind/magnetosheath plasma and magnetic field measurements, X-Ray images of the magnetosheath and polar cusps, and UV images of global auroral distributions. Remote sensing of the cusps with X-ray imaging is now possible thanks to the relatively recent discovery of solar wind charge exchange (SWCX) X-ray emission, first observed at comets, and subsequently found to occur in the vicinity of the Earth's magnetosphere. The SMILE science as well as the results of the on-going study undertaken jointly by ESA and CAS will be presented.

  11. Ion observations at Mercury's Magnetospheric Cusp

    NASA Astrophysics Data System (ADS)

    Jasinski, Jamie; Raines, Jim; Slavin, James

    2016-04-01

    The magnetospheric cusp is a region of direct entry for solar wind mass, energy and momentum into a planetary magnetosphere. Dayside magnetic reconnection between the interplanetary magnetic field and the planetary field allows shocked solar wind plasma to flow down open magnetospheric field lines. Whilst this is occurring these magnetic field lines convect poleward. For a spacecraft travelling through the high latitudes, this causes a velocity filter effect to be observed in the ion data, whereby higher energy ions are observed at lower latitudes. Here we present the ion observations from the MESSENGER spacecraft at Mercury's cusp, specifically focusing on ions latitudinally dispersed in energy. From these dispersions, the distance to the reconnection site is calculated and used to better understand the process of reconnection at Mercury's dayside magnetopause.

  12. Magnetic field drift shell splitting: Cause of unusual dayside particle pitch angle distributions during storms and substorms

    SciTech Connect

    Sibeck, D.G.; McEntire, R.W.; Lui, A.T.Y.; Lopez, R.E.; Krimigis, S.M.

    1987-12-01

    We present a magnetic field drift shell--splitting model for the unusual butterfly and head-and-shoulder energetic (E>25 keV) particle pitch angle distributions (PADs) which appear deep within the dayside magnetosphere during the course of storms and substorms. Drift shell splitting separates the high and low pitch angle particles in nightside injections as they move to the dayside magnetosphere, so that the higher pitch angle particles move radially away from Earth. Consequently, butterfly PADs with a surplus of low pitch angle particles form on the inner edge of the injection, but head-and-shoulder PADs with a surplus of high pitch angle particles from on the outer edge. A similar process removes high pitch angle particles from the inner dayside magnetosphere during storms, leaving the remaining lower pitch angle particles to form butterfly PADs on the inner edge of the ring current. A detailed case and statistical study of CCE/MEPA observations, as well as a review of previous work, shows most examples of unusual PADs to be consistent with the model. copyright American Geophysical Union 1987

  13. Magnetic field drift shell splitting - Cause of unusual dayside particle pitch angle distributions during storms and substorms

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.; Mcentire, R. W.; Lui, A. T. Y.; Lopez, R. E.; Krimigis, S. M.

    1987-01-01

    This paper presents a magnetic field drift shell-splitting model for the unusual butterfly and head-and-shoulder energetic (E greater than 25 keV) particle pitch angle distributions (PADs) which appear deep within the dayside magnetosphere during the course of storms and substorms. Drift shell splitting separates the high and low pitch angle particles in nightside injections as they move to the dayside magnetosphere, so that the higher pitch angle particles move radially away from earth. Consequently, butterfly PADs with a surplus of low pitch angle particles form on the inner edge of the injection, but head-and-shoulder PADs with a surplus of high pitch angle particles form on the outer edge. A similar process removes high pitch angle particles from the inner dayside magnetosphere during storms, leaving the remaining lower pitch angle particles to form butterfly PADs on the inner edge of the ring current. A detailed case and statistical study of Charge Composition Explorer/Medium-energy Particle Analyzer observations, as well as a review of previous work, shows most examples of unusual PADs to be consistent with the model.

  14. A Study of Steady Magnetospheric Convection Using High Latitude Magnetometers

    NASA Astrophysics Data System (ADS)

    de Silva, J. T.; Erickson, K. N.; Engebretson, M. J.; Murr, D. L.; Hughes, W. J.

    2001-05-01

    Magnetometer data from the MACCS and CANOPUS arrays in northern North America have been analyzed during two of the intervals of steady magnetospheric convection identified by the GEM community, January 29-30 and February 3-4, 1998. These intervals were characterized by extended periods of southward interplanetary magnetic field (negative IMF Bz), and by the absence of substorms. The patterns of ionospheric current flow on the dayside were found to be in general agreement with the disturbance current system, SD, originally described by Silsbee and Vestine [1942]. This indicates that during extended periods of southward IMF the convection on the dayside is the same whether or not there are substorms. When plasma flow patterns measured by the SuperDARN auroral radar network were available for comparison, these patterns agreed with the patterns inferred from magnetometers. Further study will investigate convection patterns on the nightside, and a similar study of convection for the southern high latitude region will be conducted using data from Antarctic stations.

  15. Kinetic Simulation and Energetic Neutral Atom Imaging of the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Fok, Mei-Ching H.

    2011-01-01

    Advanced simulation tools and measurement techniques have been developed to study the dynamic magnetosphere and its response to drivers in the solar wind. The Comprehensive Ring Current Model (CRCM) is a kinetic code that solves the 3D distribution in space, energy and pitch-angle information of energetic ions and electrons. Energetic Neutral Atom (ENA) imagers have been carried in past and current satellite missions. Global morphology of energetic ions were revealed by the observed ENA images. We have combined simulation and ENA analysis techniques to study the development of ring current ions during magnetic storms and substorms. We identify the timing and location of particle injection and loss. We examine the evolution of ion energy and pitch-angle distribution during different phases of a storm. In this talk we will discuss the findings from our ring current studies and how our simulation and ENA analysis tools can be applied to the upcoming TRIO-CINAMA mission.

  16. Building a Coupled Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind-Superthermal Electron System

    NASA Astrophysics Data System (ADS)

    Omelchenko, Y.; Karimabadi, H.; Schunk, R. W.; Barakat, A. R.; Gardner, L. C.; Khazanov, G. V.; Glocer, A.; Kistler, L. M.

    2013-12-01

    Recent spacecraft observations have revealed that the critical plasma processes regulating mass and energy transfer in the magnetosphere take place at relatively thin ion-scale regions (e.g., bow shock, magnetopause, magnetotail) where kinetic ions control the physics. All parts of the magnetosphere are strongly coupled: the ionosphere's finite conductivity affects the field line tying as well as the size of the magnetosphere; multi-species ionospheric outflows limit the cross-polar cap potential, provide a sink for the energy flowing into the auroral region, modify the open/closed boundary during storms and substorms and determine the distribution of energetic particles in the ring current and plasma sheet. We propose to develop the next generation global modeling framework which will, for the first time, retain full ion kinetic effects throughout the entire magnetosphere. This will be achieved through coupling independent hybrid models for two separate parts of the magnetosphere: (i) the outer magnetosphere, modeled with a new asynchronous (event-driven) global hybrid code, HYPERS, and (ii) the ionosphere-plasmasphere-polar-wind (IPPW) system, modeled with a different hybrid code coupled with a new superthermal electron (SE) transport model. Thus, in our asynchronous framework the HYPERS code will provide self-consistent electric field and ion flows (sinks) to the IPPW-SE model which will self-consistently compute ionospheric kinetic ion flows (sources) and conductivity to enable seamless continuation of the kinetic-ion physics towards the outer magnetosphere.

  17. Geospace Magnetospheric Dynamics Mission

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Kluever, C.; Burch, J. L.; Fennell, J. F.; Hack, K.; Hillard, G. B.; Kurth, W. S.; Lopez, R. E.; Luhmann, J. G.; Martin, J. B.; Hanson, J. E.

    1998-01-01

    The Geospace Magnetospheric Dynamics (GMD) mission is designed to provide very closely spaced, multipoint measurements in the thin current sheets of the magnetosphere to determine the relation between small scale processes and the global dynamics of the magnetosphere. Its trajectory is specifically designed to optimize the time spent in the current layers and to minimize radiation damage to the spacecraft. Observations are concentrated in the region 8 to 40 R(sub E) The mission consists of three phases. After a launch into geostationary transfer orbit the orbits are circularized to probe the region between geostationary orbit and the magnetopause; next the orbit is elongated keeping perigee at the magnetopause while keeping the line of apsides down the tail. Finally, once apogee reaches 40 R(sub E) the inclination is changed so that the orbit will match the profile of the noon-midnight meridian of the magnetosphere. This mission consists of 4 solar electrically propelled vehicles, each with a single NSTAR thruster utilizing 100 kg of Xe to tour the magnetosphere in the course of a 4.4 year mission, the same thrusters that have been successfully tested on the Deep Space-1 mission.

  18. Magnetosphere of Saturn

    NASA Technical Reports Server (NTRS)

    Siscoe, G. L.

    1978-01-01

    Models of the Saturnian magnetosphere based on the application of magnetospheric scaling relations to a spin-aligned planetary magnetic dipole, that produces a surface equatorial field strength in the range 0.5 to 2 gauss, exhibit the following properties: (1) The orbit of Titan lies inside of the magnetosphere essentially all of the time, even when variations in the size of the magnetosphere resulting from solar wind pressure changes are taken into account; (2) the Brice-type planetary plasmasphere reaches a peak density of about 10 protons cm/3 at L approximately 7 (L = planetocentric distance in units of planetary radii); (3) Saturn's rings have a profound effect on the energetic particle population and the plasmaspheres derived from interstellar neutrals and Titan's torus; (4) the model calculation suggests that the Titan-derived plasmasphere may be self-amplifying with a feed-back factor greater than unity, which implies the possibility of a non-linearly saturated, highly inflated Saturnian magnetosphere; and (5) this same source can have important eroding effects on the outer edge of the rings determined by Brown-Lauzerotti sputtering rates.

  19. Multipoint observations of the spatial distribution and temporal evolution of the "Nose-like" structures in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Luo, Hao; Du, Aimin; Ge, Yasong; Cao, Xin; Zhang, Ying; Huang, Sheng

    2016-04-01

    The "Nose-like" ion spectral structures are formed by ions in the near-Earth plasma sheet penetrating into the inner magnetosphere. Many studies had shown that the distribution of the Nose structures was controlled by the large-scale convection electric field, gradient-curvature drift and corotation electric field in the inner magnetosphere during geomagnetic quiet condition. However, during geomagnetic active periods, especially during the storms and substorms, the spatial and temporal characteristics and formation mechanism of different ions are still under debate. In this study, joint observations from Van Allen Probes, THEMIS, and Cluster will be used to statistically study the spatial distribution and temporal evolution of the "Nose-like" ion spectral structures in the inner magnetosphere. Backward tracing method based on Weimer 96 electric field and dipole magnetic field model was applied to simulate the ion structures and compared to the observations. The results show some important characteristics of the ion structures and will help us understand the injection mechanism of the ions from the plasma sheet into the inner magnetosphere and the relation between the storm and substorm, and thus provide important information for ring current formation.

  20. Magnetospheres of the outer planets

    NASA Technical Reports Server (NTRS)

    Vanallen, James A.

    1987-01-01

    The five qualitatively different types of magnetism that a planet body can exhibit are outlined. Potential sources of energetic particles in a planetary magnetosphere are discussed. The magnetosphere of Uranus and Neptune are then described using Pioneer 10 data.

  1. Saturn's variable magnetosphere.

    PubMed

    Gombosi, Tamas I; Hansen, Kenneth C

    2005-02-25

    Since the Cassini spacecraft reached Saturn's orbit in 2004, its instruments have been sending back a wealth of data on the planet's magnetosphere (the region dominated by the magnetic field of the planet). In this Viewpoint, we discuss some of these results, which are reported in a collection of reports in this issue. The magnetosphere is shown to be highly variable and influenced by the planet's rotation, sources of plasma within the planetary system, and the solar wind. New insights are also gained into the chemical composition of the magnetosphere, with surprising results. These early results from Cassini's first orbit around Saturn bode well for the future as the spacecraft continues to orbit the planet.

  2. Is the Current Disruption Region the Genesis Region for the Substorm X-Line?

    NASA Astrophysics Data System (ADS)

    Erickson, G. M.; Maynard, N. C.; Wilson, G. R.

    2002-12-01

    The nominal location for the substorm near-Earth X-line (NEXL) has been found to be outside but near 20RE in the tail. The modified Near-Earth Neutral Line (NENL) model postulates that braking of fast, earthward flows and pile up of magnetic flux accounts for the initiation of the substorm current wedge and dipolarization within 10RE, and its tailward expansion. Current disruption (CD) and CD-like magnetic activity accompanies dipolarization in the 8--12RE range and commences in close temporal proximity to auroral onset. We report here, based on Geotail observations, that 70% of CD-like activity in the 9 (perigee) to 12 RE range of the pre-midnight and midnight plasma sheet begins in the absence of earthward flow. In only 20% of the cases does CD-like activity start coincident with arrival of earthward flow. Indeed, in a like number of cases, CD-like activity starts coincident with a clear signal (tailward Poynting flux) arriving from nearer Earth. When auroral coverage is adequate, we have shown that these substorms proceed in two stages, with reconnection occurring during the second stage. But this is not the entire story. We note three pieces of evidence that lead us to suggest that the CD region is the genesis region for the NEXL. (1) In 10% of CD-like events, magnetic fluctuations commence like typical CD events, but rather than dipolarizing, the magnetic field diminishes. Whereas the distribution for the typical CD signature shows a strong peak near 10RE, these hybrid events are more uniformly distributed between 9 and 19 RE, and from 13--19RE represent 30% of all CD-like activity. (2) Signatures of a substorm NEXL earthward of Geotail can be found as near Earth as 13RE on occasion. (3) A minimum in equatorial magnetic field strength is believed to evolve during the substorm growth phase near 10RE. Hau and Wolf [JGR, 92, 4745, 1987] discuss how, in the presence of resistivity, the B-minimum structure diffuses tailward, and the minimum deepens, until a NEXL

  3. A Study of Multiple and Single Onset Substorms Selected Using GOES 10 Magnetic Field Data

    NASA Astrophysics Data System (ADS)

    Stoner, J. M.; Larson, R. B.; Erickson, K. N.; Engebretson, M. J.; Singer, H. J.

    2008-05-01

    A return to a more dipolar configuration of the magnetic field on the night side, near synchronous orbit, is one good indicator of a substorm expansion phase onset. Substorm expansion phase onsets for this study were selected by requiring a well-defined increase in the z-component of the magnetic field measured by the GOES 10 satellite. Event selection was subject to 2 restrictions: an increase in the z-component of the magnetic field greater than 10 nT in GSM coordinates and GOES 10 was located on the night side within 3 hours either side of local midnight during the months of August through November of the years 2000 through 2004. These time restrictions allowed for events selected using GOES 10 to be compared with events selected using the HYDRA electron flux instrument on the Polar satellite, as presented by Larson et al. [Fall 2007 AGU Meeting]. Of the 119 events selected using GOES 10, 9 events overlapped with this previous study. As expected, the 119 events closely correlated with ground-based auroral zone Pi2 data. Substorms were classified as either single or multiple onset, the latter being differentiated from the former by observing one or more subsequent Pi2 intensifications. The ratio of multiple onset to single onset substorms was found to be 2:1. Using ground-based Pi2 data it was found that in general the magnetic latitude of the initial onset of the multiple onset events was lower than the magnetic latitude of single onset events. Multiple onset events were found between 62 and 67 degrees and single onset events between 65 and 73 degrees, with single onset events being an average of one degree higher in latitude. Additionally, the time interval between Pi2 intensifications for multiple onset events was found to have a range of 9 to 30 minutes with an average of 19 minutes. The local time distribution of events used in this study corresponded to 63 percent of events occurring before local midnight. An analysis of the value of the z-component of the

  4. Planet/magnetosphere/satellite couplings: Observations from the moon

    NASA Astrophysics Data System (ADS)

    Prange, Renee

    1994-06-01

    The general characteristics of planetary magnetospheres depend upon a few key parameters, such as the magnetic dipole strength, the planetary rotation rate, and the strength of the internal plasma sources (satellites, rings, ionosphere). The present knowledge of the acceleration and of the large scale circulation of plasma in these magnetospheres is still rather poor. Plasma and energetic particle losses occur largely through precipitation into the atmosphere along magnetic field lines, giving rise to the planetary aurorae. These losses can be initiated by various kinds of magnetospheric processes, and, if clearly understood, could give major insights into the physics of the global magnetospheric system. After a brief comparative review of the planetary magnetospheres, it will be shown how our understanding of their dynamics could benefit from increased instrumental performances in terms of remote sensing in the X rays, UV to IR, and radio wavelength range, and what breakthroughs could be expected from lunar based observations.

  5. Modeling Saturn's Magnetospheric Field

    NASA Astrophysics Data System (ADS)

    Khurana, K. K.; Leinweber, H. K.; Russell, C. T.; Dougherty, M. K.

    2015-12-01

    The Cassini spacecraft has now provided an excellent coverage of radial distances, local times and latitudes in Saturn's magnetosphere. The magnetic field observations from Cassini continue to provide deep insights on the structure and dynamics of Saturn's magnetosphere. Two of the unexpected findings from Saturn's magnetosphere are that the current sheet of Saturn assumes a shallow saucer like shape from the forcing of the solar wind on the magnetosphere and that rotational diurnal periodicities are ubiquitous in a magnetosphere formed by an axisymmetric internal field from Saturn. We have used the comprehensive magnetic field data from Cassini to construct a versatile new model of Saturn's magnetospheric field for use in current and future data analysis. Our model consists of fully shielded modules that specify the internal spherical harmonic field of Saturn, the ring current and the magnetotail current systems and the interconnection magnetic field from the solar wind IMF. The tilt and hinging of the current sheet is introduced by using the general deformation technique [Tsyganenko, 1998]. In the new model, Saturn's current sheet field is based on Tsyganenko and Peredo [1994] formalism for disk-shaped current sheets. The shielding field from the magnetopause for the equatorial current sheet and the internal field is specified by Cartesian and cylindrical harmonics, respectively. To derive the shielding fields we use a model of the magnetopause constructed from magnetopause crossings observed by both Cassini and Voyager (Arridge et al. 2006). The model uses observations from Pioneer, Voyager and Cassini. A comparison of model field with the observations will be presented. Finally, we discuss both the applications of the new model and its further generalization using data from the proximal orbit phase of Cassini.

  6. Midtail plasma flows and the relationship to near-Earth substorm activity: A case study

    NASA Astrophysics Data System (ADS)

    Lopez, R. E.; Goodrich, C. C.; Reeves, G. D.; Belian, R. D.; Taktakishvili, A.

    1994-12-01

    Recent simulations of magnetotail reconnection have pointed to a link between plasma flows, dipolarization, and the substorm current wedge. In particular, Hesse and Birn (1991) have proposed that earthward jetting of plasma from the reconnection region transports flux into the near-Earth region. At the inner edge of the plasma sheet this flux piles up, producing a dipolarization of the magnetic field. The vorticity produced by the east-west deflection of the flow at the inner edge of the plasma sheet gives rise to field-aligned currents that have region 1 polarity. Thus in this scenario the earthward flow from the reconnection region produces the dipolarization ad the current wedge in a self-consistent fashion. In this study we examine observations made on April 8, 1985 by the Active Magnetospheric Particle Tracer Explorers (AMPTE)/Ion Release Module (IRM), the geosynchronous satellites 1979-053, 1983-019, and 1984-037, and Syowa station, as well as AE. This event is unique because IRM was located near the neutral sheet in the midnight sector for am extended period of time. Ground data show that there was ongoing activity in the IRM local time sector for several hours, beginning at 1800 UT and reaching a crescendo at 2300 UT. This activity was also accompanied by energetic particle variations, including injections, at geosynchronous orbit in the nighttime sector. Significantly, there were no fast flows at the neutral sheet until the great intensification of activity at 2300 UT. At that time, IRM recorded fast eartheard flow simultaneous with a dipolatization of the magetic field. We conclude that while the aforementioned scenario for the creation of the current wedge encounters serious problems explaining the earlier activity, the observations at 2300 UT are consistent with the scenario of Hesse and Birn (1191). On that basis it is argued that the physics of substorms is not exclusively rooted in the development of a global tearing mode. Processes at the inner edge

  7. Midtail plasma flows and the relationship to near-Earth substorm activity: A case study

    NASA Astrophysics Data System (ADS)

    Lopez, R. E.; Goodrich, C. C.; Reeves, G. D.; Belian, R. D.; Taktakishvili, A.

    1994-12-01

    Recent simulations of magnetotail reconnection have pointed to a link between plasma flows, dipolarization, and the substorm current wedge. In particular, Hesse and Birn (1991) have proposed that earthward jetting of plasma from the reconnection region transports flux into the near-Earth region. At the inner edge of the plasma sheet this flux piles up, producing a dipolarization of the magnetic field. The vorticity produced by the east-west deflection of the flow at the inner edge of the plasma sheet gives rise to field-aligned currents that have region 1 polarity. Thus in this scenario the earthward flow from the reconnection region produces the dipolarization and the current wedge in a self-consistent fashion. In this study we examine observations made on April 8, 1985 by the Active Magnetospheric Particle Tracer Explorers/Ion Release Module (IRM), the geosynchronous satellites 1979-053, 1983-019, and 1984-037, and Syowa station, as well as AE. This event is unique because IRM was located near the neutral sheet in the midnight sector for an extended period of time. Ground data show that there was ongoing activity in the IRM local time sector for several hours, beginning at 1800 UT and reaching a crescendo at 2300 UT. This activity was also accompanied by energetic particle variations, including injections, at geosynchronous orbit in the nighttime sector. Significantly, there were no fast flows at the neutral sheet until the great intensification of activity at 2300 UT. At that time, IRM recorded fast earthward flow simultaneous with a dipolarization of the magnetic field. We conclude that while the aforementioned scenario for the creation of the current wedge encounters serious problems explaining the earlier activity, the observations at 2300 UT are consistent with the scenario of Hesse and Birn (1991). On that basis it is argued that the physics of substorms is not exclusively rooted in the development of a global tearing mode. Processes at the inner edge of

  8. Midtail plasma flows and the relationship to near-Earth substorm activity: A case study

    NASA Technical Reports Server (NTRS)

    Lopez, R. E.; Goodrich, C. C.; Reeves, G. D.; Belian, R. D.; Taktakishvili, A.

    1994-01-01

    Recent simulations of magnetotail reconnection have pointed to a link between plasma flows, dipolarization, and the substorm current wedge. In particular, Hesse and Birn (1991) have proposed that earthward jetting of plasma from the reconnection region transports flux into the near-Earth region. At the inner edge of the plasma sheet this flux piles up, producing a dipolarization of the magnetic field. The vorticity produced by the east-west deflection of the flow at the inner edge of the plasma sheet gives rise to field-aligned currents that have region 1 polarity. Thus in this scenario the earthward flow from the reconnection region produces the dipolarization ad the current wedge in a self-consistent fashion. In this study we examine observations made on April 8, 1985 by the Active Magnetospheric Particle Tracer Explorers (AMPTE)/Ion Release Module (IRM), the geosynchronous satellites 1979-053, 1983-019, and 1984-037, and Syowa station, as well as AE. This event is unique because IRM was located near the neutral sheet in the midnight sector for am extended period of time. Ground data show that there was ongoing activity in the IRM local time sector for several hours, beginning at 1800 UT and reaching a crescendo at 2300 UT. This activity was also accompanied by energetic particle variations, including injections, at geosynchronous orbit in the nighttime sector. Significantly, there were no fast flows at the neutral sheet until the great intensification of activity at 2300 UT. At that time, IRM recorded fast eartheard flow simultaneous with a dipolatization of the magetic field. We conclude that while the aforementioned scenario for the creation of the current wedge encounters serious problems explaining the earlier activity, the observations at 2300 UT are consistent with the scenario of Hesse and Birn (1191). On that basis it is argued that the physics of substorms is not exclusively rooted in the development of a global tearing mode. Processes at the inner edge

  9. Two substorm intensifications compared: Onset, expansion, and global consequences

    SciTech Connect

    Pulkkinen, T.I.; Baker, D.N.; Opgenoorth, H.J.; Sigwarth, J.B. Opgenoorth, H.J. Greenwald, R. Friis-Christensen, E. Mukai, T. Nakamura, R. Singer, H. Reeves, G.D. Lester, M.

    1998-01-01

    We present observations of two sequential substorm onsets on May 15, 1996. The first event occurred during persistently negative IMF B{sub Z}, whereas the second expansion followed a northward turning of the interplanetary magnetic field (IMF). While the first onset remained localized, the second event led to a major reconfiguration of the magnetotail. The two very different events are contrasted, and it is suggested that the IMF direction controls the evolution of the expansion phase after the initial onset. Magnetic field modeling and field-aligned mappings are used to find the high-altitude source region of the auroral features and currents giving rise to ground magnetic disturbances: It is shown that the auroral brightening is related to processes near the inner edge of the plasma sheet but that the initial field-aligned currents couple to the midtail region. Ground magnetograms show an abrupt, large-scale weakening of the electrojet during the recovery phase. This event is followed by eastward drifting omega bands in a double-oval configuration. During that period, the Geotail plasma data show oscillations at {lt}100km/s amplitude. We argue that both these features are connected with the global tail evolution as the neutral line ceases to be active and reforms in the distant tail. {copyright} 1998 American Geophysical Union

  10. The Unreasonable Success of Magnetosphere-Ionosphere Coupling Theory

    NASA Astrophysics Data System (ADS)

    Vasyliūnas, V. M.

    2002-12-01

    The description of plasma dynamics on the basis of self-consistent coupling between magnetosphere and ionosphere, as first systematized in the early 1970's, is arguably one of the most successful theories in magnetospheric physics. It accounts for the pattern of magnetospheric convection at auroral and low latitudes, the distribution of Birkeland currents, and the dependence on changing orientation of the interplanetary magnetic field. It can incorporate assumed effects, e.g. of particle sources or conductance variations, to almost any degree of complexity at moderate cost in additional computing effort (compare the levels of physics included in advanced versions of the Rice Convection Model and of global MHD simulations, respectively). Such success combined with relative simplicity, however, is possible only because the theory has limited itself in significant ways. It treats the system in effect as doubly two-dimensional: height-integrated ionosphere plus field-line-integrated magnetosphere, with the background magnetic field structure treated as known or derived from some empirical model. It assumes that the system is always in slowly evolving quasi-equilibrium and deals only with time scales long compared to wave propagation times. Hence the theory is not easily applied where genuine 3D aspects (e.g. height and field-line dependence), poorly known or variable magnetic fields (e.g. open field lines), or transient responses e.g. to rapid solar-wind changes are important, and it is intrinsically incapable of describing explosive non-equilibrium developments such as substorm onset. Possible extensions of the theory, comparison with numerical-simulation approaches, and implications for general space plasma physics (E-J vs. B-V) will be discussed.

  11. Comparison between the two basic modes of magnetospheric convection

    NASA Astrophysics Data System (ADS)

    Siscoe, George L.; Farrugia, Charlie J.; Sandholt, Per Even

    2011-05-01

    Magnetic flux in the magnetosphere can circulate in a forward sense (southward IMF) and a reverse sense (northward IMF). The point of this paper is to compare and contrast these two modes of circulation. Both have transient and persistent phases in response to a suddenly applied southward or northward IMF that then is held steady. In the initial, transient phases, reconnection voltage exceeds transpolar potential in the ionosphere because for forward circulation there is an inductive-like time lag while the region 1 current builds up in association with a net flow of magnetic flux from the dayside to the tail (magnetospheric erosion). For the transient phase of reverse convection, reconnection voltage exceeds transpolar potential because instead of over-the-pole, night-to-day transport to undo preexisting magnetospheric erosion, magnetic flux accretes directly onto the dayside magnetosphere. The persistent phase of forward circulation almost always manifests substorms, which modulate the amounts of open and closed flux on the nightside by about 25% in a zero-sum game that leaves the dayside flux mostly unaltered. Energy to power the transient and persistent phases of forward circulation comes from the solar wind flow through magnetic stresses created as the field advects tailward. Energy to power the transient phase of reverse convection, however, comes from tapping magnetic energy stored inductively in association with the region 1 and tail current systems. The persistent phase of reverse circulation is driven possibly by the Song-Russell mechanism, which operates on a day-to-night pressure gradient of plasma entrained by dayside flux accretion. The resulting circulation is slow.

  12. The Two Basic Modes of Magnetospheric Convection Compared

    NASA Astrophysics Data System (ADS)

    Siscoe, G. L.; Farrugia, C. J.; Sandholt, P. E.

    2010-12-01

    Magnetic flux in the magnetosphere can circulate in a forward sense (southward IMF) and a reverse sense (northward IMF). The point of this presentation is to compare and contrast these two modes of circulation. Both have transient and persistent phases. In the transient phases, reconnection voltage exceeds transpolar potential because for forward circulation there is an inductive time-lag while the region 1 current builds up in association with a net flow of magnetic flux from the dayside to the tail (magnetospheric erosion). For the transient phase of reverse convection, reconnection voltage exceeds transpolar potential because magnetospheric erosion is undone by magnetic flux accretion directly onto the dayside magnetosphere with no night-to-day flow of magnetic flux needed. Energy to power the transient and persistent phases of forward circulation comes from the solar wind flow by means of the creation of magnetic stresses as the field is advected tailward. Energy to power the transient phase of reverse convection comes from tapping magnetic energy stored inductively in association with the region 1 and tail current systems. The persistent phase of forward circulation almost always manifests substorms, which modulate the amounts of open and closed flux on the nightside by about 25% in a zero-sum game that leaves the dayside flux mostly unaltered. Having exhausted its driving energy source during the transient phase, the persistent phase of reverse circulation is powered possibly by the Song-Russell mechanism, which operates on a day-to-night pressure gradient of plasma entrained by dayside flux accretion. The resulting circulation is slow. We present observations that show a predicted winter-summer asymmetry in polar cap precipitation diagnostic of a rare occurrence of the persistent phase of reverse convection.

  13. Magnetospheric conditions near the equatorial footpoints of proton isotropy boundaries

    NASA Astrophysics Data System (ADS)

    Sergeev, V. A.; Chernyaev, I. A.; Angelopoulos, V.; Ganushkina, N. Y.

    2015-12-01

    Data from a cluster of three THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft during February-March 2009 frequently provide an opportunity to construct local data-adaptive magnetospheric models, which are suitable for the accurate mapping along the magnetic field lines at distances of 6-9 Re in the nightside magnetosphere. This allows us to map the isotropy boundaries (IBs) of 30 and 80 keV protons observed by low-altitude NOAA POES (Polar Orbiting Environmental Satellites) to the equatorial magnetosphere (to find the projected isotropy boundary, PIB) and study the magnetospheric conditions, particularly to evaluate the ratio KIB (Rc/rc; the magnetic field curvature radius to the particle gyroradius) in the neutral sheet at that point. Special care is taken to control the factors which influence the accuracy of the adaptive models and mapping. Data indicate that better accuracy of an adaptive model is achieved when the PIB distance from the closest spacecraft is as small as 1-2 Re. For this group of most accurate predictions, the spread of KIB values is still large (from 4 to 32), with the median value KIB ~13 being larger than the critical value Kcr ~ 8 expected at the inner boundary of nonadiabatic angular scattering in the current sheet. It appears that two different mechanisms may contribute to form the isotropy boundary. The group with K ~ [4,12] is most likely formed by current sheet scattering, whereas the group having KIB ~ [12,32] could be formed by the resonant scattering of low-energy protons by the electromagnetic ion-cyclotron (EMIC) waves. The energy dependence of the upper K limit and close proximity of the latter event to the plasmapause locations support this conclusion. We also discuss other reasons why the K ~ 8 criterion for isotropization may fail to work, as well as a possible relationship between the two scattering mechanisms.

  14. Electron pitch angle distributions throughout the magnetosphere as observed on Ogo 5.

    NASA Technical Reports Server (NTRS)

    West, H. I., Jr.; Buck, R. M.; Walton, J. R.

    1973-01-01

    A survey of the equatorial pitch angle distributions of energetic electrons is provided for all local times out to radial distances of 20 earth radii on the night side of the earth and to the magnetopause on the day side of the earth. In much of the inner magnetosphere and in the outer magnetosphere on the day side of the earth, the normal loss cone distribution prevails. The effects of drift shell splitting - i.e., the appearance of pitch angle distributions with minimums at 90 deg, called butterfly distributions - become apparent in the early afternoon magnetosphere at extended distances, and the distribution is observed in to 5.5 earth radii in the nighttime magnetosphere. Inside about 9 earth radii the pitch angle effects are quite energy-dependent. Beyond about 9 earth radii in the premidnight magnetosphere during quiet times the butterfly distribution is often observed. It is shown that these electrons cannot survive a drift to dawn without being considerably modified. The role of substorm activity in modifying these distributions is identified.

  15. Transient, small-scale field-aligned currents in the plasma sheet boundary layer during storm time substorms

    NASA Astrophysics Data System (ADS)

    Nakamura, R.; Sergeev, V. A.; Baumjohann, W.; Plaschke, F.; Magnes, W.; Fischer, D.; Varsani, A.; Schmid, D.; Nakamura, T. K. M.; Russell, C. T.; Strangeway, R. J.; Leinweber, H. K.; Le, G.; Bromund, K. R.; Pollock, C. J.; Giles, B. L.; Dorelli, J. C.; Gershman, D. J.; Paterson, W.; Avanov, L. A.; Fuselier, S. A.; Genestreti, K.; Burch, J. L.; Torbert, R. B.; Chutter, M.; Argall, M. R.; Anderson, B. J.; Lindqvist, P.-A.; Marklund, G. T.; Khotyaintsev, Y. V.; Mauk, B. H.; Cohen, I. J.; Baker, D. N.; Jaynes, A. N.; Ergun, R. E.; Singer, H. J.; Slavin, J. A.; Kepko, E. L.; Moore, T. E.; Lavraud, B.; Coffey, V.; Saito, Y.

    2016-05-01

    We report on field-aligned current observations by the four Magnetospheric Multiscale (MMS) spacecraft near the plasma sheet boundary layer (PSBL) during two major substorms on 23 June 2015. Small-scale field-aligned currents were found embedded in fluctuating PSBL flux tubes near the separatrix region. We resolve, for the first time, short-lived earthward (downward) intense field-aligned current sheets with thicknesses of a few tens of kilometers, which are well below the ion scale, on flux tubes moving equatorward/earthward during outward plasma sheet expansion. They coincide with upward field-aligned electron beams with energies of a few hundred eV. These electrons are most likely due to acceleration associated with a reconnection jet or high-energy ion beam-produced disturbances. The observations highlight coupling of multiscale processes in PSBL as a consequence of magnetotail reconnection.

  16. On the three-dimensional magnetic structure of the plasmoid created in the magnetotail at substorm onset

    NASA Technical Reports Server (NTRS)

    Hones, E. W., Jr.; Bame, S. J.; Birn, J.; Paschmann, G.; Russell, C. T.

    1982-01-01

    The magnetic field in the plasmoid which is created by the reconnection of magnetic field lines at a neutral line formed in the near-earth region of the plasma sheet at substorm onset, and which flows out of the magnetotail into the magnetosphere's wake, displays a strong positive or negative Y(SM) component that has been difficult to reconcile with the standard, two-dimensional reconnection geometry. It is shown that this deviation of the magnetic field is a manifestation of the newly-reconnected field line loop's draping toward the tail's central or midnight meridian, and that the draping is a consequence of the three-dimensional plasma flow associated with the reconnection process.

  17. Ion Dynamics during Substorm Events Modeled with Coupled Global MHD and Kinetic Models

    NASA Astrophysics Data System (ADS)

    Lapenta, G.; Ashour-Abdalla, M.; Walker, R. J.; El-Alaoui, M.

    2014-12-01

    We have studied ion dynamics during a substorm by using a coupled fluid-kinetic approach. The UCLA global magnetospheric model was applied first and its results in a region encompassing a magnetotail reconnection site and earthward propagating dipolarization fronts was selected as input state for a full kinetic simulation based on the iPic3D code [1]. The coupling is one-way: the MHD result is used to create a full kinetic initial state by using the approach described by [2] and to force the boundary conditions. The kinetic results are not fed back into the MHD run. This approach previously has been shown [3] to provide correctly the large scale picture for a kinetic approach when the duration of the kinetic run is not so long as to alter significantly the macroscopic state captured by MHD. Here we focus especially on the ions. The electrons were described in [3]. Three aspects are analyzed. First, the ions are accelerated during the event and we track the localization of the energy exchanged, separating the contributions to the directed energy and those to the thermal energy. Second, we consider the ion motion to identify the regions where the finite Larmor radius effects violate the drift approximation and the frozen-in condition, thereby identifying the ion diffusion region. Our approach follows individual electrons and ions fully kinetically and no approximation is made in the particle orbit, so our code is equipped to study accurately the regions where the drift approximation is valid. Finally, we consider the ion distribution as a possible source of instabilities, focusing especially on temperature anisotropy instabilities and on the firehose instability. The novelty of the approach is this kinetic study is done for a specific substorm by using the global state of the magnetosphere as provided by a global MHD simulation. This differs sharply from previous approaches based on analytical approximations such as the Harris or the (quasi)-parabolic equilibria. [1

  18. Origins of magnetospheric plasma

    SciTech Connect

    Moore, T.E. )

    1991-01-01

    A review is given of recent (1987-1990) progress in understanding of the origins of plasmas in the earth's magnetosphere. In counterpoint to the early supposition that geomagnetic phenomena are produced by energetic plasmas of solar origin, 1987 saw the publication of a provocative argument that accelerated ionospheric plasma could supply all magnetospheric auroral and ring current particles. Significant new developments of existing data sets, as well as the establishment of entirely new data sets, have improved the ability to identify plasma source regions and to track plasma through the magnetospheric system of boundary layers and reservoirs. These developments suggest that the boundary between ionospheric and solar plasmas, once taken to lie at the plasmapause, actually lies much nearer to the magnetopause. Defining this boundary as the surface where solar wind and ionosphere contribute equally to the plasma, it is referred to herein as the 'geopause'. It is now well established that the infusion of ionospheric O(+) plays a major role in the storm-time distention of the magnetotail and inflation of the inner magnetosphere. After more than two decades of observation and debate, the question remains whether magnetosheric are protons of solar or terrestrial origin. 161 refs.

  19. Magnetosphere of Mercury

    NASA Technical Reports Server (NTRS)

    Whang, Y. C.

    1975-01-01

    A model magnetosphere of Mercury using Mariner 10 data is presented. Diagrams of the bow shock wave and magnetopause are shown. The analysis of Mariner 10 data indicates that the magnetic field of the planet is intrinsic. The magnetic tail and secondary magnetic fields, and the influence of the solar wind are also discussed.

  20. Examination of time-variable input effects in a nonlinear analogue magnetosphere model

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Klimas, A. J.; Roberts, D. A.

    1991-01-01

    The plasma physical analog model (an extension of the damped, harmonic-oscillator dripping faucet model) is employed to consider explicitly the effect of time-varying the inputs. This work is equivalent to considering the effects of northward and southward turnings of the interplanetary magnetic field for various periods of time. It is found that relatively extended episodes (not less than 2 hours) of turned-on input with shorter (about 1 hour) periods of turned-off input lead to model behavior much like the continuously driven case. Going to short input intervals with longer periods of zero input leads to highly irregular and dramatically fluctuating episodes of magnetotail unloading. These results give an insight into the diversity of apparent magnetospheric responses during relatively isolated substorm conditions. This work shows the absolutely critical interdependence (in a nonlinear dynamical system) of input phasing and internal magnetospheric response cycles.

  1. How Enceladus Powers the Saturnian Magnetosphere

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Leisner, J. S.; Jia, Y. D.; Khurana, K. K.; Dougherty, M. K.

    2009-04-01

    . We note that the same process occurs at Io in the jovian magnetosphere possibly accounting for the Io ribbon and the system IV rotation period.

  2. Intensity variation of ELF hiss and chorus during isolated substorms

    NASA Technical Reports Server (NTRS)

    Thorne, R. M.; Fiske, K. F.; Church, S. R.; Smith, E. J.

    1974-01-01

    Electromagnetic ELF emissions (100-1000 Hz) observed on the polar-orbiting OGO-6 satellite within three hours of the dawn-dusk meridian consistently exhibit a predictable response to isolated substorm activity. Near dawn, the emissions intensify during the substorm and then subside following the magnetic activity; the waves are most intense at L greater than 4, exhibit considerable structure and have been primarily identified as chorus. At dusk the response is entirely different; the wave intensity falls to background levels during substorm activity but subsequently intensifies, usually reaching levels well in excess of that before the disturbance. The emissions near dusk extend to low L, are relatively featureless, and have been identified as plasmaspheric hiss. These features are interpreted in terms of changes in the drift orbits of outer-zone electrons which cyclotron resonate with ELF waves.

  3. Magnetotail Flow Bursts: Association to Global Magnetospheric Circulation, Relationship to Ionospheric Activity and Direct Evidence for Localization

    NASA Technical Reports Server (NTRS)

    Angelopoulos, V.; Phan, T. D.; Larson, D. E.; Mozer, F. S.; Lin, R. P.; Parks, G. K.; Brittnacher, M. J.; Germany, G. A.; Spann, J. F., Jr.

    1998-01-01

    A series of bursty bulk flow events (BBFs) were observed by GEOTAIL and WIND in the geomagnetotail. IMP8 at the solar wind showed significant energy coupling into the magnetosphere, while the UVI instrument of POALR evidenced significant energy transfer to the ionosphere during two substorms. There was good correlation between BBFs and ionospheric activity observed by UVI even when ground magnetic signatures were absent, suggesting that low ionospheric conductivity at the active sector may be responsible for this observation. During the second substorm no significant flux transport was evidenced past WIND in stark contrast to GEOTAIL and despite the small intersatellite separation ((3.54, 2.88, -0.06) Re). Throughout the intervals studied there were significant differences in the individual flow bursts at the two satellites, even during longitudinally extended ionospheric activations. We conclude that the half-scale-size of transport bearing flow bursts is less than 3 Re.

  4. Substorm Evolution in the Near-Earth Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Erickson, Gary M.

    2004-01-01

    This grant represented one-year, phase-out funding for the project of the same name (NAG5-9110 to Boston University) to determine precursors and signatures of local substorm onset and how they evolve in the plasma sheet using the Geotail near-Earth database. We report here on two accomplishments: (1) Completion of an examination of plasma velocity signature at times of local onsets in the current disruption (CD) region. (2) Initial investigation into quantification of near-Earth flux-tube contents of injected plasma at times of substorm injections.

  5. The Lewis Research Center geomagnetic substorm simulation facility

    NASA Technical Reports Server (NTRS)

    Berkopec, F. D.; Stevens, N. J.; Sturman, J. C.

    1977-01-01

    A simulation facility was established to determine the response of typical spacecraft materials to the geomagnetic substorm environment and to evaluate instrumentation that will be used to monitor spacecraft system response to this environment. Space environment conditions simulated include the thermal-vacuum conditions of space, solar simulation, geomagnetic substorm electron fluxes and energies, and the low energy plasma environment. Measurements for spacecraft material tests include sample currents, sample surface potentials, and the cumulative number of discharges. Discharge transients are measured by means of current probes and oscilloscopes and are verified by a photomultiplier. Details of this facility and typical operating procedures are presented.

  6. Ultra-low-frequency wave power in the magnetotail lobes. I - Relation to substorm onsets and the auroral electrojet index

    NASA Technical Reports Server (NTRS)

    Smith, R. A.; Goertz, C. K.; Harrold, B. G.; Goldstein, M. L.; Lepping, R. P.; Fitch, C. A.; Sands, M. R.

    1990-01-01

    Time-series observations of the magnetotail-lobe magnetic field have been Fourier analyzed to compute the frequency-weighted energy density Pfz in the range 1-30 mHz. Pfz is generally observed in the range 0.0001-0.01 gamma-squared Hz with a mean value of 0.0012 during substorm growth phases and 0.001 in the comparison intervals. No strong correlation of Pfz is found with the auroral electrojet index in either set of intervals, but during substorm growth phases Pfz may vary by an order of magnitude over time scales of 30 min, with a tendency for higher power levels to occur later in the growth phase. Increases in Pfz precede by about 10 min localized expansive phase activity observed in individual magnetograms.

  7. Observations of field-aligned currents, waves, and electric fields at substorm onset

    NASA Technical Reports Server (NTRS)

    Smits, D. P.; Hughes, W. J.; Cattell, C. A.; Russell, C. T.

    1986-01-01

    Substorm onsets, identified Pi 2 pulsations observed on the Air Force Geophysics Laboratory Magnetometer Network, are studied using magnetometer and electric field data from ISEE 1 as well as magnetometer data from the geosynchronous satellites GOES 2 and 3. The mid-latitude magnetometer data provides the means of both timing and locating the substorm onset so that the spacecraft locations with respect to the substorm current systems are known. During two intervals, each containing several onsets or intensifications, ISEE 1 observed field-aligned current signatures beginning simultaneously with the mid-latitude Pi 2 pulsation. Close to the earth broadband bursts of wave noise were observed in the electric field data whenever field-aligned currents were detected. One onset occurred when ISEE 1 and GOES 2 were on the same field line but in opposite hemispheres. During this onset ISEE 1 and GOES 2 saw magnetic signatures which appear to be due to conjugate field-aligned currents flowing out of the western end of the westward auroral electrojets. The ISEE 1 signature is of a line current moving westward past the spacecraft. During the other interval, ISEE 1 was in the near-tail region near the midnight meridian. Plasma data confirms that the plasma sheet thinned and subsequently expanded at onset. Electric field data shows that the plasma moved in the opposite direction to the plasma sheet boundary as the boundary expanded which implies that there must have been an abundant source of hot plasma present. The plasma motion was towards the center of the plasma sheet and earthwards and consisted of a series of pulses rather than a steady flow.

  8. A Simulation Study of the Thermosphere Mass Density Response to Substorms Using GITM Model

    NASA Astrophysics Data System (ADS)

    Liu, X.; Ridley, A. J.

    2014-12-01

    The temporal and spatial variations of the thermosphere mass density during a variety of idealized substorms were investigated using the Global Ionosphere Thermosphere Model (GITM) simulation and Challenging Minisatellite Payload (CHAMP) satellite. From the GITM simulation, the maximum mass density perturbation of an idealized substorm with a peak variation of Hemispheric Power (HP) Index of 50 GW and interplanetary magnetic field (IMF) Bz of -2 nT was ~14% about 50 min after the substorm onset in the nightside sector of the aurora zone. About 110 min after onset, a negative mass density perturbation (~-5%) occurred in the night sector, which was consistent with the mass density measurement of the CHAMP satellite. Further investigation suggests that a large scale in situ gravity wave was generated in the aurora zone and propagated to the mid and low latitudes. Simulations with IMF Bz changes, with HP being constant and HP changing and IMF Bz being constant were run to investigate any nonlinearities in the combined response. The mass density perturbation due the IMF Bz variation peaks in the dusk sector and the density perturbation due to HP input peaks in the nightside sector. The non-linear of the mass density response to different energy input is less than 6%. The thermospheric mass density at higher altitudes is more sensitive to the Joule heating energy input. The change in hemisphere power adds electron density to lower altitudes, so the heating due to the HP change is at lower altitudes than the heating due to the IMF Bz change. This causes the density change due to the HP change to be larger than the density change due to the IMF change.

  9. The magnetospheric trough

    SciTech Connect

    Thomsen, M.F.; McComas, D.J.; Elphic, R.C.; Borovsky, J.E.

    1997-03-04

    The authors review the history of the concepts of the magnetospheric cold-ion trough and hot-electron trough and conclude that the two regions are actually essentially the same. The magnetospheric trough may be viewed as a temporal state in the evolution of convecting flux tubes. These flux tubes are in contact with the earth`s upper atmosphere which acts both as a sink for precipitating hot plasma sheet electrons and as a source for the cold ionospheric plasma leading to progressive depletion of the plasma sheet and refilling with cold plasma. Geosynchronous plasma observations show that the rate of loss of plasma-sheet electron energy density is commensurate with the precipitating electron flux at the low-latitude edge of the diffuse aurora. The rate at which geosynchronous flux tubes fill with cold ionospheric plasma is found to be consistent with previous estimates of early-time refilling. Geosynchronous observations further indicate that both Coulomb collisions and wave-particle effects probably play a role in trapping ionospheric material in the magnetosphere.

  10. Solar wind influence on Jupiter's magnetosphere and aurora

    NASA Astrophysics Data System (ADS)

    Vogt, Marissa; Gyalay, Szilard; Withers, Paul

    2016-04-01

    Jupiter's magnetosphere is often said to be rotationally driven, with strong centrifugal stresses due to large spatial scales and a rapid planetary rotation period. For example, the main auroral emission at Jupiter is not due to the magnetosphere-solar wind interaction but is driven by a system of corotation enforcement currents that arises to speed up outflowing Iogenic plasma. Additionally, processes like tail reconnection are also thought to be driven, at least in part, by processes internal to the magnetosphere. While the solar wind is generally expected to have only a small influence on Jupiter's magnetosphere and aurora, there is considerable observational evidence that the solar wind does affect the magnetopause standoff distance, auroral radio emissions, and the position and brightness of the UV auroral emissions. We will report on the results of a comprehensive, quantitative study of the influence of the solar wind on various magnetospheric data sets measured by the Galileo mission from 1996 to 2003. Using the Michigan Solar Wind Model (mSWiM) to predict the solar wind conditions upstream of Jupiter, we have identified intervals of high and low solar wind dynamic pressure. We can use this information to quantify how a magnetospheric compression affects the magnetospheric field configuration, which in turn will affect the ionospheric mapping of the main auroral emission. We also consider whether there is evidence that reconnection events occur preferentially during certain solar wind conditions or that the solar wind modulates the quasi-periodicity seen in the magnetic field dipolarizations and flow bursts.

  11. A statistical study on the timescales involved into the solar wind-magnetosphere interaction during the March 17, 2015 storm

    NASA Astrophysics Data System (ADS)

    Alberti, Tommaso; Consolini, Giuseppe; Lepreti, Fabio; Vecchio, Antonio; Carbone, Vincenzo

    2016-04-01

    The magnetospheric dynamics in response to solar wind changes in the course of magnetic substorms and storms can be investigated via a set of geomagnetic indices, which monitor the changes of some of the most important current systems: the Auroral Electrojet indices (AE, AU, AL and AO) and the low latitude geomagnetic ones (Dst, Sym-H, ...). The variations of these indices are, indeed, associated with the changes of the auroral electrojets and ring current systems during geomagnetic substorms and storms. In this work, we present a case study of the relevant timescales responsible for coupling between the solar wind changes and the magnetospheric response during the St. Patrick's Day Geomagnetic Storm of 2015, by investigating the behavior of the IMF-Bz component and the AE, AL and Sym-H indices at different timescales using the Empirical Mode Decomposition (EMD). Indeed, the EMD allows us to extract the intrinsic oscillations (modes) present into the different datasets. The relevance of the different timescales in the solar wind-magnetosphere coupling is further investigated by means of the Delayed Mutual Information (DMI).

  12. Substorm simulation: Insight into the mechanisms of initial brightening

    NASA Astrophysics Data System (ADS)

    Ebihara, Y.; Tanaka, T.

    2015-09-01

    Initial brightening of the aurora is an optical manifestation of the beginning of a substorm expansion and is accompanied by large-amplitude upward field-aligned currents (FACs). Based on global magnetohydrodynamic simulation, we suggest the possible generation mechanism of the upward FAC that may manifest the initial brightening. (1) A formation of the near-Earth neutral line (NENL) releases the tension force that accelerates plasma earthward. (2) The earthward (perpendicular) flow is converted to a field-aligned flow when flow braking takes place. (3) A high-pressure region propagates earthward along a field line. (4) The off-equatorial high-pressure region pulls in and discharges ambient plasma, which generates a flow vorticity around it. (5) Region 1-sense FAC is generated in the upper part of the off-equatorial high-pressure region. (6) The upward FAC is connected with the ionosphere in the center of the Harang discontinuity, causing the initial brightening. Additional dynamo is generated in the near-Earth region, which transmits electromagnetic energy. Upward FAC that manifests the initial brightening seems to be necessarily originated in the near-Earth off-equatorial region where the magnitude of the perpendicular (diamagnetic) current is relatively small in comparison with that of the FAC. Near the equatorial plane, the perpendicular current is comparable to or larger than FAC so that a current line is diverted from a magnetic field line and that the FAC generated near the equatorial plane is not necessarily connected with the ionosphere. The proposed mechanism occurs regardless of the location of the NENL and may explain some of auroral forms.

  13. Low-energy electrons (5-50 keV) in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Ganushkina, N. Y.; Liemohn, M. W.; Amariutei, O. A.; Pitchford, D.

    2014-01-01

    Transport and acceleration of the 5-50 keV electrons from the plasma sheet to geostationary orbit were investigated. These electrons constitute the low-energy part of the seed population for the high-energy MeV particles in the radiation belts and are responsible for surface charging. We modeled one nonstorm event on 24-30 November 2011, when the presence of isolated substorms was seen in the AE index. We used the Inner Magnetosphere Particle Transport and Acceleration Model (IMPTAM) with the boundary at 10 RE with moment values for the electrons in the plasma sheet. The output of the IMPTAM modeling was compared to the observed electron fluxes in 10 energy channels (from 5 to 50 keV) measured on board the AMC 12 geostationary spacecraft by the Compact Environmental Anomaly Sensor II with electrostatic analyzer instrument. The behavior of the fluxes depends on the electron energy. The IMPTAM model, driven by the observed parameters such as Interplanetary Magnetic Field (IMF) By and Bz, solar wind velocity, number density, dynamic pressure, and the Dst index, was not able to reproduce the observed peaks in the electron fluxes when no significant variations are present in those parameters. We launched several substorm-associated electromagnetic pulses at the substorm onsets during the modeled period. The observed increases in the fluxes can be captured by IMPTAM when substorm-associated electromagnetic fields are taken into account. Modifications of the pulse front velocity and arrival time are needed to exactly match the observed enhancements.

  14. Saturn: atmosphere, ionosphere, and magnetosphere.

    PubMed

    Gombosi, Tamas I; Ingersoll, Andrew P

    2010-03-19

    The Cassini spacecraft has been in orbit around Saturn since 30 June 2004, yielding a wealth of data about the Saturn system. This review focuses on the atmosphere and magnetosphere and briefly outlines the state of our knowledge after the Cassini prime mission. The mission has addressed a host of fundamental questions: What processes control the physics, chemistry, and dynamics of the atmosphere? Where does the magnetospheric plasma come from? What are the physical processes coupling the ionosphere and magnetosphere? And, what are the rotation rates of Saturn's atmosphere and magnetosphere?

  15. Overview - Electric fields. [in magnetosphere

    NASA Technical Reports Server (NTRS)

    Cauffman, D. P.

    1979-01-01

    The electric fields session is designed to review progress in observation, theory, and modeling of magnetospheric electric fields, and to expose important new results. The present report comments on the state and prospects of electric field research, with particular emphasis on relevance to quantitative modeling of the magnetospheric processes. Attention is given to underlying theories and models. Modeling philosophy is discussed relative to explanatory models and representative models. Modeling of magnetospheric electric fields, while in its infancy, is developing rapidly on many fronts employing a variety of approaches. The general topic of magnetospheric electric fields is becoming of prime importance in understanding space plasmas.

  16. Saturn: atmosphere, ionosphere, and magnetosphere.

    PubMed

    Gombosi, Tamas I; Ingersoll, Andrew P

    2010-03-19

    The Cassini spacecraft has been in orbit around Saturn since 30 June 2004, yielding a wealth of data about the Saturn system. This review focuses on the atmosphere and magnetosphere and briefly outlines the state of our knowledge after the Cassini prime mission. The mission has addressed a host of fundamental questions: What processes control the physics, chemistry, and dynamics of the atmosphere? Where does the magnetospheric plasma come from? What are the physical processes coupling the ionosphere and magnetosphere? And, what are the rotation rates of Saturn's atmosphere and magnetosphere? PMID:20299587

  17. Large-scale kinetic simulation of the magnetosphere

    NASA Astrophysics Data System (ADS)

    Palmroth, Minna; Hoilijoki, Sanni; Pfau-Kempf, Yann; Hietala, Heli; Nishimura, Toshi; Angelopoulos, Vassilis; Pulkkinen, Tuija; Ganse, Urs; von Alfthan, Sebastian; Vainio, Rami

    2016-04-01

    Vlasiator is a newly developed, global hybrid-Vlasov simulation, which solves the six-dimensional phase space utilising the Vlasov equation for protons, while electrons are a charge-neutralising fluid. The outcome of the simulation is a global reproduction of ion-scale physics. Vlasiator produces the ion distribution functions and the related kinetic physics in unprecedented detail, in the global scale magnetospheric scale with the resolution required by kinetic physics. Here, we review the recent progress made in the Vlasiator development, highlight newest physical findings, and look forward to future challenges by presenting our upcoming new project awarded by the European Research Council. Specifically, we investigate the dayside-nightside coupling of the magnetospheric dynamics. 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. The simulation is during steady southward interplanetary magnetic field. We observe dayside reconnection and the resulting 2D representations of flux transfer events (FTE). In the nightside, the plasma sheet first shows slight density enhancements moving slowly earthward. Second, 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. We investigate this substorm process holistically as a result of dayside-nightside coupling. In particular, we concentrate on the role of the FTE's in the magnetospheric dynamics.

  18. Reconstructing the magnetosphere from data using radial basis functions

    NASA Astrophysics Data System (ADS)

    Andreeva, Varvara A.; Tsyganenko, Nikolai A.

    2016-03-01

    A new method is proposed to derive from data magnetospheric magnetic field configurations without any a priori assumptions on the geometry of electric currents. The approach utilizes large sets of archived satellite data and uses an advanced technique to represent the field as a sum of toroidal and poloidal parts, whose generating potentials Ψ1 and Ψ2 are expanded into series of radial basis functions (RBFs) with their nodes regularly distributed over the 3-D modeling domain. The method was tested by reconstructing the inner and high-latitude field within geocentric distances up to 12RE on the basis of magnetometer data of Geotail, Polar, Cluster, Time History of Events and Macroscale Interactions during Substorms, and Van Allen space probes, taken during 1995-2015. Four characteristic states of the magnetosphere before and during a disturbance have been modeled: a quiet prestorm period, storm deepening phase with progressively decreasing SYM-H index, the storm maximum around the negative peak of SYM-H, and the recovery phase. Fitting the RBF model to data faithfully resolved contributions to the total magnetic field from all principal sources, including the westward and eastward ring current, the tail current, diamagnetic currents associated with the polar cusps, and the large-scale effect of the field-aligned currents. For two main phase conditions, the model field exhibited a strong dawn-dusk asymmetry of the low-latitude magnetic depression, extending to low altitudes and partly spreading sunward from the terminator plane in the dusk sector. The RBF model was found to resolve even finer details, such as the bifurcation of the innermost tail current. The method can be further developed into a powerful tool for data-based studies of the magnetospheric currents.

  19. Observational evidence for a kinetic ballooning instability during substorm

    NASA Astrophysics Data System (ADS)

    Chang, T.; Cheng, C. Z.; Chiang, J. C.; Chen, A. B.

    2010-12-01

    A theory of kinetic ballooning instability has been proposed to explain the trigger of substorm expansion phase. It results from the energy release of nonuiform plasma pressure with gradient along the direction of the magnetic field curvature. Recent plasma observations also show the possible evidence for a kinetic ballooning instability. In this study, we investigate the wave activities around the onset of substorm expansion phase based on the THEMIS satellites observations and evolution of auroral activities during substorm. Pi 2 low frequency perturbation prior to current disruption can be identified in the magnetic fluctuations. When Pi 1 high frequency perturbation is also excited, it enters the turbulent state. During the late growth phase, the auroral arc is forming with an azimuthally-spaced structure with high mode number and growing with a linear growth rate. The theory of kinetic ballooning instability can explain the physical mechanism of Pi 2 instability excited prior to the current disruption, the properties of substorm onset arc, and the cause of eventual arc breakup.

  20. Relativistic Electron Response to the Combined Magnetospheric Impact of a Coronal Mass Ejection Overlapping with a High-Speed Stream: Van Allen Probes Observations

    NASA Technical Reports Server (NTRS)

    Kanekal, S. G.; Baker, D. N.; Henderson, M. G.; Li, W.; Fennell, J. F.; Zheng, Y.; Richardson, I. G.; Jones, A.; Ali, A. F.; Elkington, S. R.; Jaynes, A.; Li, X.; Blake, J. B.; Reeves, G. D.; Spence, H. E.; Kletzing, C. A.

    2015-01-01

    During early November 2013, the magnetosphere experienced concurrent driving by a coronal mass ejection (CME) during an ongoing high-speed stream (HSS) event. The relativistic electron response to these two kinds of drivers, i.e., HSS and CME, is typically different, with the former often leading to a slower buildup of electrons at larger radial distances, while the latter energizing electrons rapidly with flux enhancements occurring closer to the Earth. We present a detailed analysis of the relativistic electron response including radial profiles of phase space density as observed by both Magnetic Electron and Ion Sensor (MagEIS) and Relativistic Electron Proton Telescope instruments on the Van Allen Probes mission. Data from the MagEIS instrument establish the behavior of lower energy (<1 MeV) electrons which span both intermediary and seed populations during electron energization. Measurements characterizing the plasma waves and magnetospheric electric and magnetic fields during this period are obtained by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probes, Search Coil Magnetometer and Flux Gate Magnetometer instruments on board Time History of Events and Macroscale Interactions during Substorms, and the low-altitude Polar-orbiting Operational Environmental Satellites. These observations suggest that during this time period, both radial transport and local in situ processes are involved in the energization of electrons. The energization attributable to radial diffusion is most clearly evident for the lower energy (<1 MeV) electrons, while the effects of in situ energization by interaction of chorus waves are prominent in the higher-energy electrons.

  1. Relativistic electron response to the combined magnetospheric impact of a coronal mass ejection overlapping with a high-speed stream: Van Allen Probes observations

    NASA Astrophysics Data System (ADS)

    Kanekal, S. G.; Baker, D. N.; Henderson, M. G.; Li, W.; Fennell, J. F.; Zheng, Y.; Richardson, I. G.; Jones, A.; Ali, A. F.; Elkington, S. R.; Jaynes, A.; Li, X.; Blake, J. B.; Reeves, G. D.; Spence, H. E.; Kletzing, C. A.

    2015-09-01

    During early November 2013, the magnetosphere experienced concurrent driving by a coronal mass ejection (CME) during an ongoing high-speed stream (HSS) event. The relativistic electron response to these two kinds of drivers, i.e., HSS and CME, is typically different, with the former often leading to a slower buildup of electrons at larger radial distances, while the latter energizing electrons rapidly with flux enhancements occurring closer to the Earth. We present a detailed analysis of the relativistic electron response including radial profiles of phase space density as observed by both Magnetic Electron and Ion Sensor (MagEIS) and Relativistic Electron Proton Telescope instruments on the Van Allen Probes mission. Data from the MagEIS instrument establish the behavior of lower energy (<1 MeV) electrons which span both intermediary and seed populations during electron energization. Measurements characterizing the plasma waves and magnetospheric electric and magnetic fields during this period are obtained by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probes, Search Coil Magnetometer and Flux Gate Magnetometer instruments on board Time History of Events and Macroscale Interactions during Substorms, and the low-altitude Polar-orbiting Operational Environmental Satellites. These observations suggest that during this time period, both radial transport and local in situ processes are involved in the energization of electrons. The energization attributable to radial diffusion is most clearly evident for the lower energy (<1 MeV) electrons, while the effects of in situ energization by interaction of chorus waves are prominent in the higher-energy electrons.

  2. A Study of Single and Multiple Onset Substorms

    NASA Astrophysics Data System (ADS)

    Larson, R. B.; Stoner, J. M.; Erickson, K. N.; Engebretson, M. J.; Scudder, J. D.; Frey, H. U.; Russell, C. T.

    2007-12-01

    A good indicator of substorm expansion phase onset is a well-defined increase and/or energization of the HYDRA electron flux measured onboard POLAR when the satellite is on the night side in the central region of the near earth plasmasheet. This signature is usually, but not always, accompanied by a dipolarization of the magnetic field. Another clear indicator of expansion phase onset is a well-defined increase in the z-component of the magnetic field which is indicative of dipolarization on the night side at geostationary orbit. Substorm events for this study were selected using these two indicators. 34 expansion phase onsets were found using the HYDRA instrument and 119 onsets were found using GOES 10 satellite data. For event selection the GSM coordinates of POLAR were constrained as follows: -9 < x < -7, -2 < y < 2, -1 < z < 1 in units of earth radii. The GOES 10 location was subject to the requirement that the satellite was located within 3 hours either side of local midnight. As expected these onset times were found to be closely correlated with the onset of ground-based auroral zone enhanced Pi2 activity and magnetic bays. Multiple onset substorms were distinguished from single onset events by observing the occurrence of one or more additional subsequent Pi2 intensifications and negative bays corresponding to enhancements of the westward electrojet. For several events, when data was available, auroral brightenings at the equatorward edge of discrete arcs as observed by the FUV experiment onboard the IMAGE spacecraft were also found to be closely correlated with not only the initial Pi2 intensification but also with subsequent Pi2 intensifications. The ratio of multiple onset to single onset substorms was found to be 2.3:1. Using Pi2 and IMAGE FUV data it was found that the initial onset of a multiple onset substorm usually corresponds to Pi2 intensifications and auroral brightening signatures at a lower auroral zone latitude than for a single onset event. In

  3. Magnetospheric state of sawtooth events

    NASA Astrophysics Data System (ADS)

    Fung, Shing F.; Tepper, Julia A.; Cai, Xia

    2016-08-01

    Magnetospheric sawtooth events, first identified in the early 1990s, are named for their characteristic appearance of multiple quasiperiodic intervals of slow decrease followed by sharp increase of proton differential energy fluxes in the geosynchronous region. The successive proton flux oscillations have been interpreted as recurrences of stretching and dipolarization of the nightside geomagnetic field. Due to their often extended intervals with 2-10 cycles, sawteeth occurrences are sometimes referred to as a magnetospheric mode. While studies of sawtooth events over the past two decades have yielded a wealth of information about such events, the magnetospheric state conditions for the occurrence of sawtooth events and how sawtooth oscillations may depend on the magnetospheric state conditions remain unclear. In this study, we investigate the characteristic magnetospheric state conditions (specified by Psw interplanetary magnetic field (IMF) Btot, IMF Bz Vsw, AE, Kp and Dst, all time shifted with respect to one another) associated with the intervals before, during, and after sawteeth occurrences. Applying a previously developed statistical technique, we have determined the most probable magnetospheric states propitious for the development and occurrence of sawtooth events, respectively. The statistically determined sawtooth magnetospheric state has also been validated by using out-of-sample events, confirming the notion that sawtooth intervals might represent a particular global state of the magnetosphere. We propose that the "sawtooth state" of the magnetosphere may be a state of marginal stability in which a slight enhancement in the loading rate of an otherwise continuous loading process can send the magnetosphere into the marginally unstable regime, causing it to shed limited amount of energy quickly and return to the marginally stable regime with the loading process continuing. Sawtooth oscillations result as the magnetosphere switches between the marginally

  4. AKR breakup and auroral particle acceleration at substorm onset

    NASA Astrophysics Data System (ADS)

    Morioka, A.; Miyoshi, Y.; Tsuchiya, F.; Misawa, H.; Yumoto, K.; Parks, G. K.; Anderson, R. R.; Menietti, J. D.; Donovan, E. F.; Honary, F.; Spanswick, E.

    2008-09-01

    The dynamical behavior of auroral kilometric radiation (AKR) is investigated in connection with auroral particle acceleration at substorm onsets using high-time-resolution wave spectrograms provided by Polar/PWI electric field observations. AKR develops explosively at altitudes above a preexisting low-altitude AKR source at substorm onsets. This "AKR breakup" suggests an abrupt formation of a new field-aligned acceleration region above the preexisting acceleration region. The formation of the new acceleration region is completed in a very short time (amplitude increases 10,000 times in 30 seconds), suggesting that the explosive development is confined to a localized region. AKR breakups are usually preceded (1-3 minutes) by the appearance and/or gradual enhancement of the low-altitude AKR. This means that the explosive formation of the high-altitude electric field takes place in the course of the growing low-altitude acceleration. The development of the low-altitude acceleration region is thus a necessary condition for the ignition of the high-altitude bursty acceleration. The dH/dt component from a search-coil magnetometer at ground shows that a few minutes prior to substorm onsets, the quasi-DC component begins a negative excursion that is nearly synchronized with the start of the gradual enhancement of the low-altitude AKR, indicating a precursor-like behavior for the substorm. This negative variation of dH/dt suggests an exponentially increasing ionospheric current induced by the upward field-aligned current. At substorm onsets, the decrease in the quasi-DC variation of dH/dt further accelerates, indicating a sudden reinforcement of the field-aligned current.

  5. The Role of Solar and Solar Wind Forcing of Magnetospheric Particle Enhancements

    NASA Astrophysics Data System (ADS)

    Baker, D. N.

    2015-12-01

    Observational and numerical modeling results demonstrate that solar wind streams and coronal mass ejections drive coherent processes within the coupled magnetosphere-ionosphere system. The magnetosphere progresses through a specific sequence of energy-loading and stress-developing states until the entire system suddenly reconfigures. Long-term studies of high-energy particle fluxes in the Earth's magnetosphere have revealed many of their temporal occurrence characteristics and their relationships to solar wind drivers. In order to observe major energetic particle 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 are normally a key first step in the acceleration of magnetospheric particles 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, magnetospheric storms and 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 events examined whether associated with high-speed streams or with CME-related changes, but not all. In this work, we address transient solar wind phenomena as they pertain to high-energy particle acceleration and transport. We also discuss various models of particle energization that have recently been advanced. We present remarkable new results from the Van Allen Probes mission and the Magnetospheric Multiscale (MMS) mission that confirm and greatly extend these key ideas.

  6. Nitrogen In Saturn's Magnetosphere

    NASA Astrophysics Data System (ADS)

    Smith, H. T.; Sittler, E. C.; Johnson, R. E.; McComas, D. J.; Reisenfeld, D.; Shappirio, M. D.; Baragiola, R.; Michael, M.; Shematovich, V. I.; Crary, F.; Young, D. T.

    2004-12-01

    We are analyzing CAPS instrument data on Cassini to look for nitrogen ions in Saturn's magnetosphere. Because Voyager could not separate oxygen and nitrogen, there has been considerable controversy on nitrogen's presence and relative importance. Two principal sources have been suggested: Titan's atmosphere and nitrogen species trapped in Saturn's icy satellite surfaces (Sittler et al 2004). The latter may be primordial nitrogen, likely as NH3 in ice (Stevenson 1982; Squyers et al. 1983) or nitrogen ions that have been implanted in the surface (Delitsky and Lane 2002). We will present the results of Saturnian nitrogen cloud modeling and relevant CAPS observations. We recently described the Titan source (Michael, et al. 2004; Shematovich et al. 2003; Smith et al. 2004; Sittler et al. 2004) in preparation for Cassini's Saturnian plasma measurements. Two components were identified: energetic nitrogen ions formed near Titan and energized as they diffused inward (Sittler et al. 2004) and neutrals in orbits with small perigee that became ionized in the inner magnetosphere (Smith et al 2004). The latter component would be a source of lower energy, co-rotating nitrogen ions in the inner magnetosphere. Such a component would have an energy spectrum similar to nitrogen species sputtered from the icy satellite surfaces (Johnson and Sittler 1990). However, the mass spectrum would differ, likely containing NHx and NOx species also, and, hence, may be separated from the Titan source. Our preliminary analysis for nitrogen species in the CAPS data will be compared to our models. Of interest will be the energy spectra, which can indicate whether any nitrogen present is formed locally or near Titan's orbit and diffused inward. This work is supported by the NASA Planetary Atmospheres, NASA Graduate Student Research, Virginia Space Grant Consortium Graduate Research Fellowship and CAPS Cassini instrument team programs.

  7. Magnetospheric dynamo processes

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1984-01-01

    Three processes are examined whereby an effective electromotive force and energy input arise in circuits of magnetospheric currents, even in the absence of time-varying magnetic fields. The first involves currents on 'open' field lines, linking the ionosphere with the solar wind, and it underscores the role of polarization currents. The second may exist on the current filament observed in the vicinity of Jupiter's satellite Io. The third may operate along the high-latitude boundary of the earth's magnetic tail, from where it pumps energy into the plasma sheet.

  8. PC index as a proxy of the solar wind energy that entered into the magnetosphere and energy accumulated in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Troshichev, Oleg; Sormakov, Dmitry

    The PC index has been approved by the International Association of Geomagnetism and Aeronomy (Merida, Mexico, 2013) as a new international index of magnetic activity. Application of the PC index as a proxy of a solar wind energy that entered into the magnetosphere determines a principal distinction of the PC index from AL and Dst indices, which are regarded as characteristics of the energy that realized in magnetosphere in form of substorms 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. In this study the relationships between the PC and Dst indices in course of more than 200 magnetic storms observed in epoch of solar maximum (1998-2004) have been examined for different classes of storms separated by their kind and intensity. Results of statistical analysis demonstrate that depression of geomagnetic field starts to develop as soon as PC index steadily excess the threshold level ~1.5 mV/m; the storm intensity (DstMIN) follows, with delay ~ 1 hour, the maximum of PC in course of the storm. Main features of magnetic storms are determined, irrespective of their class and intensity, by the accumulated-mean PC value (PCAM): storm is developed as long as PCAM increases, comes to maximal intensity when PCAM attains the maximum, and starts to decay as soon as PCAM value displays decline. The run of “anomalous” magnetic storm on January 21-22, 2005, lasting many hours (with intensity of ≈ -100 nT) under conditions of northward or close to zero BZ component, is perfectly governed by behavior of the accumulated-mean PCAM index and, therefore, this storm should be regarded as an ordinary phenomenon. The conclusion is made that the PC index provides the unique on-line information on solar wind

  9. External versus internal triggering of substorms: An information-theoretical approach

    NASA Astrophysics Data System (ADS)

    Johnson, Jay R.; Wing, Simon

    2014-08-01

    The role of external triggering of substorms through northward turning of the interplanetary magnetic field has been examined in a number of recent studies. While Hsu and McPherron (2002, 2004) argue that the strong association between external triggers defined by Lyons et al. (1997) and substorm onsets could be responsible for most substorms, Morley and Freeman (2007) argue that the association between northward interplanetary magnetic field (IMF) turnings and substorm onsets are coincidental rather than causal, because the same external triggers are also closely associated with an artificial list of substorm onsets generated with the Minimal Substorm Model, which has no requirement of northward IMF turning. We examine an expanded list of substorms using conditional redundancy, an entropy-based measure of conditional dependency, to examine whether northward IMF turning as an external trigger provides any additional information about substorm onset beyond knowing that there has been a period of sustained loading of energy flux (southward IMF). Our analysis reveals that only a few percent additional information is provided by the northward turning criterion, which is consistent with the statistics of surrogate data sets of external triggers constructed to coincide with 2% of substorms. We therefore conclude that northward turning of the IMF is, in general, coincidentally, rather than causally, associated with substorm onsets.

  10. Characteristics of the near-Earth magnetotail variations at the time of substorm onset

    NASA Astrophysics Data System (ADS)

    Machida, S.; Miyashita, Y.; Ieda, A.; Saito, Y.

    2013-12-01

    From the result of our statistical analysis with GEOTAIL and THEMIS data, we confirmed that tailward plasma flows are created in association with the plasma flows that propagate from X ~ -12 Re toward the earth at the time of substorm onset. To understand the physical mechanism of the formation of such tailward flows, we have performed a case study of substorm event occurred at 10:46 UT on June 22, 1997 when the GEOTAIL was located at (X, Y) ~ (-9, 6) Re and encountered with the flow bursts. The event started with earthward flows for about 2 min with the northward magnetic field enhancement, followed by slow tailward flows. Such an earthward and tailward flow sequence repeated three times. By calculating the electric current from electron and ion moment data, we found the variation in the X-component of JxB force that can be interpreted to have close relationship with the enhancement of earthward flows. Namely, the flows are not simply generated at a distant location and reach the GEOTAIL, but they are still under acceleration at X ~ -10 Re. After the passage of the flow front, the (JxB)x term takes negative values. The time derivative of Vx does not necessarily correspond to (JxB)x/mn. This inconsistency might be due to the contribution of the terms such as -grad P or (Vgrad) V. It is also necessary to check the possibility of the decoupling between electrons and ions as well as the effect of anomalous resistivity.

  11. TWISTING, RECONNECTING MAGNETOSPHERES AND MAGNETAR SPINDOWN

    SciTech Connect

    Parfrey, Kyle; Beloborodov, Andrei M.; Hui, Lam

    2012-07-20

    We present the first simulations of evolving, strongly twisted magnetar magnetospheres. Slow shearing of the magnetar crust is seen to lead to a series of magnetospheric expansion and reconnection events, corresponding to X-ray flares and bursts. The axisymmetric simulations include rotation of the neutron star and the magnetic wind through the light cylinder. We study how the increasing twist affects the spindown rate of the star, finding that a dramatic increase in spindown occurs. Particularly spectacular are explosive events caused by the sudden opening of large amounts of overtwisted magnetic flux, which may be associated with the observed giant flares. These events are accompanied by a short period of ultrastrong spindown, resulting in an abrupt increase in spin period, such as was observed in the giant flare of SGR 1900+14.

  12. Identification of substorm precursor and expansion onsets by applying Singular Spectrum Transformation to ground-magnetometer data

    NASA Astrophysics Data System (ADS)

    Tokunaga, T.; Nakamura, K.; Higuchi, T.; Yoshikawa, A.; Uozumi, T.; Morioka, A.; Yumoto, K.

    2009-12-01

    Until now, several substorm studies have discussed that about substorm precursors, which are observed in the auroral region and preceded to onset of substorm expansion phase by 1-3 minutes. Kepko et al., [2004] indicated that high-latitude magnetogram shows a very small negative deflection in the H-component before auroral arc brightening. Morioka et al. [2008] reported the dH/dt component from a search-coil magnetometer at ground shows that a few minutes prior to high-altitude AKR breakup, the quasi-DC component begins a negative exclusion that is nearly synchronized with the start of the gradual enhancement of the low-altitude AKR. These observations suggest that the precursor signature on the H-comp. of geomagnetic filed observed in the auroral region reflects the gradual enhancement of parallel electric filed before expansion onset and it plays an essential role to drive a subsequent enhancement of the upward FAC. Therefore, it is important to elucidate spatio-temporal evolutions of the substorm precursors to understand the onset mechanism associated with the rapid development of the M-I coupling via FAC. In most cases, it is difficult to determine the accurate timing because substorm precursor has a gradual onset. In this paper, we will present a new algorithm based on Singular Spectrum Analysis (SSA), described in the next paragraph, for determining the onset times of substorm precursors and expansion phase. SSA has been developed and applied in the field of geophysics. Ide and Inoue [2005] demonstrated the effectiveness of a SSA based change-point detection method, which is called Singular Spectrum Transformation (SST), to detect a structure change of various types of time series. Since this approach is completely data adaptive, it is probably a powerful method for our aim: to detect a small and irregular perturbation such as substorm precursors on the geomagnetic data observed in the auroral region. We have applied SST for a substorm event occurred on

  13. The magnetosphere of Saturn

    NASA Astrophysics Data System (ADS)

    Beard, D. B.; Gast, M. A.

    1987-06-01

    Pioneer 11 and Voyager 1 and 2 magnetic field measurements over the entire flyby of Saturn's magnetic field have been analyzed by fitting a magnetospheric dipole field (i.e., a dipole field plus the field due to currents in the magnetopause), higher moments of the internal field aligned with the dipole along the rotation axis, and the field due to an equatorial sheet current to the magnetic measurements. A dipole moment of 21,431 nT R(s) exp 3, a quadrupole moment of 2403 nT R(s) exp 4, an octopole moment of 2173 nT R(s) exp 5, and an equatorial sheet current of half thickness 2.0 R(s) from about 5 R(s) to the solar edge of the magnetopause, fit the measurements over the entire magnetosphere with an rms deviation of 3.2 nT where R(s) is the planet radius, 66,330 km. The primary feature of the present analysis is the explicit inclusion of the calculated magnetopause current field, which reduces the overall rms deviation over the entire flyby from sigma values of 4.7 and 5.9 nT, using previous models, to 3.2 nT using the present.

  14. Black hole magnetospheres

    SciTech Connect

    Nathanail, Antonios; Contopoulos, Ioannis

    2014-06-20

    We investigate the structure of the steady-state force-free magnetosphere around a Kerr black hole in various astrophysical settings. The solution Ψ(r, θ) depends on the distributions of the magnetic field line angular velocity ω(Ψ) and the poloidal electric current I(Ψ). These are obtained self-consistently as eigenfunctions that allow the solution to smoothly cross the two singular surfaces of the problem, the inner light surface inside the ergosphere, and the outer light surface, which is the generalization of the pulsar light cylinder. Magnetic field configurations that cross both singular surfaces (e.g., monopole, paraboloidal) are uniquely determined. Configurations that cross only one light surface (e.g., the artificial case of a rotating black hole embedded in a vertical magnetic field) are degenerate. We show that, similar to pulsars, black hole magnetospheres naturally develop an electric current sheet that potentially plays a very important role in the dissipation of black hole rotational energy and in the emission of high-energy radiation.

  15. Magnetospheric Multiscale Overview and Science Objectives

    NASA Astrophysics Data System (ADS)

    Burch, J. L.; Moore, T. E.; Torbert, R. B.; Giles, B. L.

    2016-03-01

    Magnetospheric Multiscale (MMS), a NASA four-spacecraft constellation mission launched on March 12, 2015, will investigate magnetic reconnection in the boundary regions of the Earth's magnetosphere, particularly along its dayside boundary with the solar wind and the neutral sheet in the magnetic tail. The most important goal of MMS is to conduct a definitive experiment to determine what causes magnetic field lines to reconnect in a collisionless plasma. The significance of the MMS results will extend far beyond the Earth's magnetosphere because reconnection is known to occur in interplanetary space and in the solar corona where it is responsible for solar flares and the disconnection events known as coronal mass ejections. Active research is also being conducted on reconnection in the laboratory and specifically in magnetic-confinement fusion devices in which it is a limiting factor in achieving and maintaining electron temperatures high enough to initiate fusion. Finally, reconnection is proposed as the cause of numerous phenomena throughout the universe such as comet-tail disconnection events, magnetar flares, supernova ejections, and dynamics of neutron-star accretion disks. The MMS mission design is focused on answering specific questions about reconnection at the Earth's magnetosphere. The prime focus of the mission is on determining the kinetic processes occurring in the electron diffusion region that are responsible for reconnection and that determine how it is initiated; but the mission will also place that physics into the context of the broad spectrum of physical processes associated with reconnection. Connections to other disciplines such as solar physics, astrophysics, and laboratory plasma physics are expected to be made through theory and modeling as informed by the MMS results.

  16. A Small Postmidnight Substorm During IMF Bz+ and By+ Conditions -- Joint Optical, Radar, Magnetic and Satellite Observations

    NASA Astrophysics Data System (ADS)

    Liang, J.; Sofko, G.; Donovan, E.; Greenwald, R.

    2002-12-01

    Multi-instrument observations of a small postmidnight substorm event during a period of IMF dominated by Bz+ and By+ conditions on October 9, 2000, showed the substorm structure with high time resolution. Three optical intensifications and Pi2 bursts occurred. The last and strongest Pi2 burst was associated with an expansive phase (EP) onset, characterized by a 100 nT magnetic bay at Fort Churchill and an auroral breakup in which the 630 nm emissions moved poleward about 2.5 degrees. About 11 minutes after the first EP onset, a second stage of auroral brightening occurred. For each of the three initial optical intensifications, there was an eastward-moving discrete azimuthal structure. SuperDARN HF radar line-of-sight velocity measurements revealed eastward electric fields within each Pi2 wave train. The observations are interpreted as resulting from the drift-Alfven-ballooning (DAB) mode instability at near-geosynchronous orbit (NGO) locations. Within the NGO drift waves, regions of charge separation led to electric fields and field-aligned currents (FACs) of alternating direction. The ionospheric reflection of Alfven wave energy likely generated the Pi2 pulsations observed on the ground. The multi-instrument ground observations agree quite well with the substorm onset scenario based upon CRRES satellite observations by Erickson et al. [2000]. There was a single, relatively confined (~4 hour in MLT) counterclockwise convection cell during the growth phase and EP onset. A clearly defined vortex at its center defined the center of the downward FAC. This vortex, initially northward of the optical aurora, moved eastward and then suddenly southward just prior to the EP onset. At that time, the FAC structure was typical of the substorm current wedge (SCW). Reasons for the convection cell motion and SCW development are discussed. Erickson, G. M., N. C. Maynard, W. J. Burke, G. R. Wilson, and M. A. Heinemann, Electromagnetics of substorm onsets in the near

  17. "Ion spectral gaps" and stationary "Nose structures" in the quiet inner magnetosphere: observations from the ION experiment onboard the INTERBALL satellite, modeling and relations between these two phenomena

    NASA Astrophysics Data System (ADS)

    Buzulukova, N.; Ganushkina, N.; Kovrazhkin, R.; Pulkkinen, T.; Sauvaud, J.-A.; Glazunov, A.

    2003-04-01

    We analyze measurements of ion spectral gaps (ISGs) and "nose structures" observed by the ION particle spectrometer onboard the INTERBALL-2 satellite. ISGs are a sharp decreases of H+ flux at a particular narrow energy range, and were first observed by McIlwain (1972) onboard the geostationary satellite ATS-5 during relatively quiet times. Clear examples of ISG in the morning, dayside, evening and nightside sectors of the magnetosphere are selected for detailed analysis and modeling. To obtain a model ISG, the trajectories of ions drifting in the equatorial plane from their nightside source to the observation point were computed for the energy range 0.1-15 keV. It is shown that the ISGs observed by the ION spectrometer throughout the inner magnetosphere are the result of superposition of the two effects: 1. ISGs due to excessive drift time for particular "resonant energy" ions from the source to the observation point; 2. ISGs due to the existence of "forbidden" zones disconnected from the source in a particular energy range. Both factors were described in the literature, but considered separately, while the observed global pattern actually includes both of them but in particular MLT sectors. The term "nose structures" was first introduced by Smith and Hoffman (1974) to describe the penetration of particles H+ in the inner magnetosphere during substorms. From statistical analysis of ION spectrometer observations it is clear seen that the nose structures not only the characteristic of the substorm processes but its are often observed in the quiet magnetosphere. From modeling of observed by ION spectrometer nose structures we conclude that these nose structures are formed together with ISGs from "forbidden" zones, and can be observed in all MLT sectors on L-shells 4.5 - 6. We call this type of nose structures "stationary nose structures" to distinguish its from substorm nose structures, and to underline the formation of stationary nose structures due to motion of H

  18. Magnetospheric energy principle for spherically symmetric monopolar magnetospheres.

    PubMed

    Miura, Akira

    2013-05-24

    A new magnetospheric energy principle is developed for spherically symmetric monopolar magnetospheres with open straight field lines. The principle is based on the self-adjointness of the force operator, which ensures energy conservation in the unperturbed magnetospheric plasma volume. A Neuman-type boundary condition for the perpendicular displacement at the ionosphere yields a negative contribution to the potential energy variation. This contribution makes high-mode-number incompressible field-line-bending modes unstable owing to the plasma displacement over the spherical ionospheric surface. PMID:23745887

  19. Alfven Waves in the Solar Wind, Magnetosheath, and Outer Magnetosphere

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.

    2007-01-01

    Alfven waves Propagating outward from the Sun are ubiquitous in the solar wind and play a major role in the solar wind-magnetosphere interaction. The passage of the waves generally occurs in the form of a series of discrete steepened discontinuities, each of which results in an abrupt change in the interplanetary magnetic field direction. Some orientations of the magnetic field permit particles energized at the Earth's bow shock to gain access to the foreshock region immediately upstream from the Earth's bow shock. The thermal pressure associated with these particles can greatly perturb solar wind plasma and magnetic field parameters shortly prior to their interaction with the Earth's bow shock and magnetosphere. The corresponding dynamic pressure variations batter the magnetosphere, driving magnetopause motion and transient compressions of the magnetospheric magnetic field. Alfven waves transmit information concerning the dynamic pressure variations applied to the magnetosphere to the ionosphere, where they generate the traveling convection vortices (TCVs) seen in high-latitude ground magnetograms. Finally, the sense of Alfvenic perturbations transmitted into the magnetosheath reverses across local noon because magnetosheath magnetic field lines drape against the magnetopause. The corresponding change in velocity perturbations must apply a weak torque to the Earth's magnetosphere.

  20. Titan Ion Composition at Magnetosphere-Ionosphere Transition Region

    NASA Technical Reports Server (NTRS)

    Sittler, Edward C.; Hartle, R. E.; Shappirio, M.; Simpson, D. J.; COoper, J. F.; Burger, M. H.; Johnson, R. E.; Bertucci, C.; Luhman, J. G.; Ledvina, S. A.; Szego, K.; Coates, A. J.; Young, D. T.

    2006-01-01

    Using Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS) ion composition data, we will investigate the compositional changes at the transition region between Saturn's magnetospheric flow and Titan's upper ionosphere. It is this region where scavenging of Titan's upper ionosphere can occur, where it is then dragged away by the magnetospheric flow as cold plasma for Saturn's magnetosphere. This cold plasma may form plumes as originally proposed by (1) during the Voyager 1 epoch. This source of cold plasma may have a unique compositional signature such as methane group ions. Water group ions that are observed in Saturn's outer magnetosphere (2,3) are relatively hot and probably come from the inner magnetosphere where they are born from fast neutrals escaping Enceladus (4) and picked up in the outer magnetosphere as hot plasma (5). This scenario will be complicated by pickup methane ions within Titan's mass loading region, as originally predicted by (6) based on Voyager 1 data and observationally confirmed by (3,7) using CAPS IMS data. But, CH4(+) ions or their fragments can only be produced as pickup ions from Titan's exosphere which can extend beyond the transition region of concern here, while CH5(+) ions can be scavenged from Titan's ionosphere. We will investigate these possibilities.

  1. A Solar Cycle Dependence of Nonlinearity in Magnetospheric Activity

    SciTech Connect

    Johnson, Jay R; Wing, Simon

    2005-03-08

    The nonlinear dependencies inherent to the historical K(sub)p data stream (1932-2003) are examined using mutual information and cumulant based cost as discriminating statistics. The discriminating statistics are compared with surrogate data streams that are constructed using the corrected amplitude adjustment Fourier transform (CAAFT) method and capture the linear properties of the original K(sub)p data. Differences are regularly seen in the discriminating statistics a few years prior to solar minima, while no differences are apparent at the time of solar maximum. These results suggest that the dynamics of the magnetosphere tend to be more linear at solar maximum than at solar minimum. The strong nonlinear dependencies tend to peak on a timescale around 40-50 hours and are statistically significant up to one week. Because the solar wind driver variables, VB(sub)s and dynamical pressure exhibit a much shorter decorrelation time for nonlinearities, the results seem to indicate that the nonlinearity is related to internal magnetospheric dynamics. Moreover, the timescales for the nonlinearity seem to be on the same order as that for storm/ring current relaxation. We suggest that the strong solar wind driving that occurs around solar maximum dominates the magnetospheric dynamics suppressing the internal magnetospheric nonlinearity. On the other hand, in the descending phase of the solar cycle just prior to solar minimum, when magnetospheric activity is weaker, the dynamics exhibit a significant nonlinear internal magnetospheric response that may be related to increased solar wind speed.

  2. Proton Acceleration at Injection Fronts in the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Ukhorskiy, A. Y.; Sitnov, M. I.; Gkioulidou, M.; Merkin, V. G.

    2015-12-01

    During geomagnetic storms a large volume of ions are transported from the magnetotail deep into the inner magnetosphere leading to ion acceleration to the energies of tens to hundreds keV. Energized ions become the dominant source of plasma pressure in the inner magnetosphere. Hot plasma pressure drives large electrical currents which determine global electrodynamics and coupling of the inner magnetosphere-ionosphere system. Recent analysis of ion measurements from the RBSPICE experiment of the Van Allen Probes mission showed that the buildup of plasma pressure in the inner magnetosphere largely occurs in the form of localized discrete injections similar to dipolarization fronts observed in the magnetotail. Previous studies proposed several mechanisms that can rapidly accelerate protons to ~100 keV at injection fronts in the magnetotail including betatron-line acceleration, reflection and the synchrotron effect. None of these mechanisms, however, can operate in the inner magnetosphere where the ambient magnetic field is much higher and the propagation speeds of injection fronts are much lower. In this paper we discuss a new mechanism of stable proton trapping and acceleration inherent to the inner magnetosphere that can rapidly energize particles to >200 keV.

  3. The magnetospheres of the outer planets

    SciTech Connect

    Mcnutt, R.L., Jr. )

    1991-01-01

    Research on the magnetospheres of all of the outer planets including Jupiter, Uranus, Neptune, and Pluto is reviewed for the 1987-1990 time period. Particular attention is given to magnetospheric structure, plasma transport, Jovian aurora, Io and the plasma torus, Titan and its magnetospheric interactions, rings and dusty plasmas, magnetospheric convection, and satellite interactions.

  4. M-I coupling across the Harang reversal during storm--substorm activity driven by an interplanetry ICMEs

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Sandholt, P. E.; Denig, W. F.

    2013-12-01

    By ground - satellite conjunctions across the auroral oval at dusk we study events of dynamical magnetosphere--ionosphere (M-I) coupling from the plasma sheet - ring current system via R1 and R2 field-aligned currents (FACs) during auroral electrojet activations appearing on the poleward and equatorward sides of the Harang reversal (HR), respectively. The interval of ICME passage at Earth we study is characterized by repetitive substorm activity appearing as a series of westward expansions--eastward retreats of the westward electrojet (WEJ) across the 1800 MLT meridian. Harang region-north (HR-N) is characterized by R1 FAC closure, WEJ activity, poleward boundary intensifications (PBIs) - equatorward - moving auroral streamers (inverted V - arcs), and (at different times) poleward auroral expansions. Harang region-south (HR-S) is characterized by R2 FAC closure leading to eastward electrojet (EEJ) activity and precipitation in the southern auroral branch. Using this approach we documented the detailed temporal evolution of polar cap convection, as derived from the PCN index, in relation to direct observations of the dynamical behaviour of the two basic branches of the substorm current system, i. e. the R2 FAC coupling from the partial ring current (PRC) and the R1 FAC coupling from the plasma sheet. We distinguish between two activity levels: (i) major AL-excursions beyond -1000 nT (accompanied by large-scale field dipolarizations in the inner magnetotail), followed by SYM-H dips (plasma injections enhancing the PRC) and R2 FAC - EEJ enhancements, and (ii) partial AL - recovery (AL within -300 to -600 nT) characterized by a series of M - I coupling events with manifestations on both sides of the HR, including streamer events in HR-N, leading to equatorward/poleward motions of the HR boundary.

  5. The Extended Pulsar Magnetosphere

    NASA Technical Reports Server (NTRS)

    Constantinos, Kalapotharakos; Demosthenes, Kazanas; Ioannis, Contopoulos

    2012-01-01

    We present the structure of the 3D ideal MHD pulsar magnetosphere to a radius ten times that of the light cylinder, a distance about an order of magnitude larger than any previous such numerical treatment. Its overall structure exhibits a stable, smooth, well-defined undulating current sheet which approaches the kinematic split monopole solution of Bogovalov 1999 only after a careful introduction of diffusivity even in the highest resolution simulations. It also exhibits an intriguing spiral region at the crossing of two zero charge surfaces on the current sheet, which shows a destabilizing behavior more prominent in higher resolution simulations. We discuss the possibility that this region is physically (and not numerically) unstable. Finally, we present the spiral pulsar antenna radiation pattern.

  6. The Magnetospheric Multiscale Constellation

    NASA Astrophysics Data System (ADS)

    Tooley, C. R.; Black, R. K.; Robertson, B. P.; Stone, J. M.; Pope, S. E.; Davis, G. T.

    2016-03-01

    The Magnetospheric Multiscale (MMS) mission is the fourth mission of the Solar Terrestrial Probe (STP) program of the National Aeronautics and Space Administration (NASA). The MMS mission was launched on March 12, 2015. The MMS mission consists of four identically instrumented spin-stabilized observatories which are flown in formation to perform the first definitive study of magnetic reconnection in space. The MMS mission was presented with numerous technical challenges, including the simultaneous construction and launch of four identical large spacecraft with 100 instruments total, stringent electromagnetic cleanliness requirements, closed-loop precision maneuvering and pointing of spinning flexible spacecraft, on-board GPS based orbit determination far above the GPS constellation, and a flight dynamics design that enables formation flying with separation distances as small as 10 km. This paper describes the overall mission design and presents an overview of the design, testing, and early on-orbit operation of the spacecraft systems and instrument suite.

  7. Magnetospheric Plasma Physics

    NASA Astrophysics Data System (ADS)

    Mauk, Barry H.

    Magnetospheric Plasma Physics is volume 4 of an ongoing series of review books entitled Developments in Earth and Planetary Sciences organized by the Center for Academic Publications Japan. The series is intended to stress Japanese work; however, the present volume was written by seven internationally selected authors who have reviewed works from a broad range of sources. This volume is composed of articles drawn from five lecture series presented at the Autumn College o f Plasma Physics, International Center for Theoretical Physics, Trieste, Italy, October-November 1979. The audiences for these lecture series were plasma and/or space plasma physicists, or students of the same, and the level and tone of this volume clearly reflect that condition.

  8. Magnetosphere of Uranus

    SciTech Connect

    Ness, N.F.

    1986-12-01

    The magnetosphere and magnetic field of Uranus are analyzed using Voyager 2 data. It is observed that the magnetic axis of Uranus is tilted 60 deg from its rotation axis; the magnetic dipole center is displaced almost 7700 km from the center of the planet; the magnetic field intensity varies over its surface between 24,000-69,000 gammas; and the rotation rate of the planet is 17.24 hours. The dynamo generation of the planetary magnetic field is examined. Consideration is given to the auroral activity, magnetic tails, moons, and radiation belts of charged particles of Uranus. The significance of the large tilt and offset magnetic axis for the interior of Uranus is discussed.

  9. Features and Mechanisms of Substorm Onset and Expansion

    NASA Astrophysics Data System (ADS)

    Cheng, C. Z.; Chang, T.

    2010-12-01

    We present key features of substorm observations by THEMIS satellites and high cadence optical observations by THEMIS All Sky Imagers and the Imager of Sprites and Upper Atmospheric Lightnings (ISUAL) aboard the FORMOSAT-2 satellite. In particular, we emphasize the fine structure in the onset arc and the associated magnetic fluctuations in Pi1 and Pi2 frequency ranges and their exponential growing behaviors before the onset of expansion phase. We will discuss the possible physical mechanism of substorm onset and the formation of onset arc. We will also present the nonlinear evolution of the onset arc breakup and magnetic fluctuations into turbulent states, the current disruption and magnetic field dipolarization processes and the dispersionless particle injection during the expansion phase.

  10. Early MITHRAS results - The electric field response to substorms

    NASA Astrophysics Data System (ADS)

    de La Beaujardiere, O.; Holt, J.; Nielsen, E.

    1983-12-01

    The MITHRAS data base offers a unique opportunity to observe simultaneously the auroral-zone ion convection pattern with three radars, widely separated in longitude. It is attempted to separate local-time versus universal-time effects in a study of the electric field signature associated with substorms. Preliminary results indicate that this signature is similar at a given local time, regardless of the longitude of the station. In the dawn and dusk sectors the electric field is intensified, whereas around noon and midnight the electric field appears to reverse during a substorm. The potential drop across the polar cap can be estimated from the potential across the auroral oval. The radar data agree well with the relationship found by Reiff and co-workers between the solar wind energy parameter epsilon and the cross-tail potential.

  11. Magnetospheres of the outer planets

    SciTech Connect

    Cheng, A.F.

    1986-12-01

    The magnetospheres of the outer planets have been shown by Voyager explorations to strongly interact with the surfaces and atmospheres of their planetary satellites and rings. In the cases of Jupiter, Saturn and Uranus, the processes of charged particle sputtering, neutral gas cloud formation, and rapid plasma injection from the ionization of the neutral clouds, have important implications both for the magnetospheres as a whole and for the surfaces and atmospheres of their satellites. The general methodology employed in these researches has involved comparisons of the planetary magnetospheres in order to identify common physical processes. 16 references.

  12. Spectacular ionospheric flow structures associated with substorm auroral onset

    NASA Astrophysics Data System (ADS)

    Gallardo-Lacourt, B. I.; Nishimura, Y.; Lyons, L. R.; Zou, Y.; Angelopoulos, V.; Donovan, E.; Mende, S. B.; Ruohoniemi, J.; McWilliams, K. A.; Nishitani, N.

    2013-12-01

    Auroral observations have shown that brightening at substorm auroral onset consists of azimuthally propagating beads forming along a pre-existing arc. However, the ionospheric flow structure related to this wavy auroral structure has not been previously identified. We present 2-d line-of-sight flow observations and auroral images from the SuperDARN radars and the THEMIS ground-based all-sky-imager array to investigate the ionospheric flow pattern associated with the onset. We have selected events where SuperDARN was operating in the THEMIS mode, which provides measurements along the northward looking radar beam that have time resolution (6 s) comparable to the high time resolution of the imagers and gives us a unique tool to detect properties of flows associated with the substorm onset instability. We find very fast flows (~1000 m/s) that initiated simultaneously with the onset arc beads propagating across the THEMIS-mode beam meridian. The flows show oscillations at ~9 mHz, which corresponds to the periodicity of the auroral beads propagating across the radar beam. 2-d radar measurements also show a wavy pattern in the azimuthal direction with a wavelength of ~74 km, which is close to the azimuthal separation of individual beads, although this determination is limited by the 2 minute radar scan period. These strong correlations (in time and space) between auroral beading and the fast ionospheric flows suggest that these spectacular flows are an important feature of the substorm onset instability within the inner plasma sheet. Also, a clockwise flow shear was observed in association with individual auroral beads, suggesting that such flow shear is a feature of the unstable substorm onset waves.

  13. The response of the near earth magnetotail to substorm activity

    NASA Technical Reports Server (NTRS)

    Kivelson, M. G.; McPherron, R. L.; Thompson, S.; Khurana, K. K.; Weygand, J. M.; Balogh, Andrew

    2005-01-01

    The large scale structure of the current sheet in the terrestrial magnetotail is often represented as the superposition of a constant northward-oriented magnetic field component (B(sub z)) and a component along the Earth-Sun direction (B(sub x)) that varies with distance from the center of the sheet (z(sub o) in GSM) as in a Hams neutral sheet. The latter implies that B(sub x) = B(sub Lx) tanh((z - z(sub o))/h) where B(sub Lx) is the magnitude of the B(sub x) component in the northern lobe. Correspondingly, the cross-tail current should be approximated by J(sub y) = (B(sub Lx)/h) sech(sup 2)((z - z(sub o))/h). Using data from the fluxgate magnetometer (FGM) on the Cluster I1 spacecraft tetrad, we have used measured fields and currents to ask if this model represents the large-scale properties of the system. During very quiet crossings of the plasmasheet, we find that the model gives a reasonable estimate of the trend of the average current and field distributions, but during disturbed intervals, the best fit fails to represent the data. If, however, the parameters z(sub o) and h of the model are taken as variable functions of time, the fits can be reasonably good. The temporal variation of the fit parameter h that characterizes the thickness of the current sheet can be interpreted in terms of thinning during the growth phase of a substorm and thickening following the expansion phase. Ground signatures that give insight into the local time of substorm onset can be used to interpret the response of the plasmasheet to substorm related changes of the global system. During a substorm, the field magnitude in the central plasmasheet fluctuates at the period of Pi2 pulsations.

  14. MESSENGER observations of substorm activity in Mercury's near magnetotail

    NASA Astrophysics Data System (ADS)

    Sun, Wei-Jie; Slavin, James; Fu, Suiyan; Raines, Jim; Zong, Qiu-Gang; Yao, Zhonghua; Pu, Zuyin; Shi, Quanqi; Poh, Gangkai; Boardsen, Scott; Imber, Suzanne; Sundberg, Torbjörn; Anderson, Brian; Korth, Haje; Baker, Daniel

    2015-04-01

    MESSENGER magnetic field and plasma measurements taken during crossings of Mercury's magnetotail from 2011 to 2014 have been examined for evidence of substorm activity. A total of 32 events were found during which an Earth-like growth phase was followed by clear near-tail expansion phase signatures. During the growth phase, the lobe of the tail loads with magnetic flux while the plasma sheet thins due to the increased lobe magnetic pressure. MESSENGER is often initially in the plasma sheet and then moves into the lobe during the growth phases. The averaged time scale of the loading is around 1 min, consistent with previous observations of Mercury's Dungey cycle. The dipolarization front that marks the initiation of the substorm expansion phase is only a few seconds in duration. The spacecraft then abruptly enters the plasma sheet due to the plasma sheet expansion as reconnection-driven flow from the near-Mercury neutral line encounters the stronger magnetic fields closer to the planet. Substorm activity in the near tail of Mercury is quantitatively very similar to the Earth despite the very compressed time scale.

  15. Statistical Mapping of Bursty Bulk Flows in the Magnetosphere Supported by the Virtual Magnetospheric Observatory

    NASA Astrophysics Data System (ADS)

    Merka, J.; Sibeck, D. G.; Narock, T. W.

    2011-12-01

    Fast transient plasma flows in the magnetosphere are usually associated with magnetic reconnection and/or rapid changes in the magnetospheric configuration. Using a common methodology to analyze data from the THEMIS satellites we map the statistical occurrence rate of bursty bulk flows (BBFs) in the magnetosphere. Such a task involves obtaining and processing of large amount of data (5 THEMIS satellites provide measurements since spring of 2007), then writing custom code and searching for intervals of interests. The existence of a Virtual Magnetospheric Observatory (VMO) offers, however, a less laborious alternative. We discuss how the VMO made our research faster and easier and also point out the inherent limitations of the VMO use. The VMO's goal is to help researches by creating a single point of uniform discovery, access, and use of magnetospheric data. Available data can be searched based on various criteria as, for example, spatial location, time of observation, measurement type, parameter values, etc. The results can then be saved, downloaded or displayed as, for example, spatial-temporal plots that quickly reveal where and how often was the searched-for phenomenon observed. Our analysis revealed that the BBFs were found more frequently with increasing distance from Earth and the peak occurrence rate of earthward BBFs was at Xgsm = 29 Re and Ygsm = -2 Re. The tailward BBFs were very rarely observed even between Xgsm = -20 and -30 Re but they occurred over a wide range of local times. The positions with highest BBF occurrence rates differ from previous reports that used IRM and ISEE2 data.

  16. Assessment of inductive electric fields contribution to the overall particle energization in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Ilie, R.; Liemohn, M. W.; Daldorff, L. K. S.

    2015-12-01

    The terrestrial magnetosphere has the capability to rapidly accelerate charged particles up to very high energies over relatively short times and distances. These energetic particles are injected from the magnetotail into the inner magnetosphere through two primary mechanisms. One transport method is the potential-driven convection during periods of southward IMF, which allows part of the dawn-to-dusk solar wind electric field to effectively map down to the polar ionosphere. The second transport process, substorm activity, involves a sudden reconfiguration of the magnetic field and the creation of transient induced electric fields. However, it is not possible to distinguish the two terms by only measuring the electric field, which is typically just the potential field. Assessing the relative contribution of potential versus inductive electric fields at the energization of the hot ion population in the inner magnetosphere is only possible by thorough examination of the time varying magnetic field and current systems using global modeling of the entire system. We calculate the induced electric field via a 3D integration over the entire magnetosphere domain. This full volume integration approach removes the need to trace independent field lines and lifts the assumption that the magnetic field lines can be treated as frozen in a stationary ionosphere. We quantify the relative contributions of potential and inductive electric fields at driving plasma sheet ions into the inner magnetosphere during disturbed conditions. The consequence of these injections on the distortion of the near-Earth magnetic field and current systems have been rarely separated in order to determine their relative effectiveness from a global perspective.

  17. Physics of magnetospheric boundary layers

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    1995-01-01

    This final report was concerned with the ideas that: (1) magnetospheric boundary layers link disparate regions of the magnetosphere-solar wind system together; and (2) global behavior of the magnetosphere can be understood only by understanding its internal linking mechanisms and those with the solar wind. The research project involved simultaneous research on the global-, meso-, and micro-scale physics of the magnetosphere and its boundary layers, which included the bow shock, the magnetosheath, the plasma sheet boundary layer, and the ionosphere. Analytic, numerical, and simulation projects were performed on these subjects, as well as comparisons of theoretical results with observational data. Other related activity included in the research included: (1) prediction of geomagnetic activity; (2) global MHD (magnetohydrodynamic) simulations; (3) Alfven resonance heating; and (4) Critical Ionization Velocity (CIV) effect. In the appendixes are list of personnel involved, list of papers published; and reprints or photocopies of papers produced for this report.

  18. The Magnetosphere of Ganymede (Invited)

    NASA Astrophysics Data System (ADS)

    Kivelson, M.

    2013-12-01

    Before the 1980s who would have guessed that Jupiter's moon Ganymede was destined to become an exemplar of extremes? Titan had long been described as the largest moon in the solar system with a radius > 2800 km [e.g., Smith, 1980]. Only after Voyager 1 measured the scale of its atmosphere did Titan (radius 2575 km) cede its place as the largest moon in the solar system to Ganymede (radius 2634.1 km). Thereafter Galileo's flybys established additional extraordinary properties of Ganymede. It is the only moon with an intrinsic magnetic field, the only body in the solar system whose magnetosphere forms in a sub-Alfvénic flow, and the only body that does not rotate relative to the symmetry axis of its magnetosphere. Its magnetospheric structure is of special interest as a prototype for magnetospheres in a parameter regime not found in the solar wind. Our knowledge of its properties is based on a combination of in situ and remote sensing measurements, somewhat sketchy but most informative, supplemented by results from computer simulations. To some extent Ganymede's magnetosphere is remarkable for what it lacks. It has no bow shock, no radiation belts, and no plasmasphere. Its shape is also unique, with Alfvén wings stretched almost transverse to the upstream flow replacing tail lobes folded back in the flow direction. It is the only magnetosphere embedded within a magnetosphere, a situation that implies highly predictable and slowly changing upstream plasma and field conditions. This predictability has enabled us to characterize the properties of reconnection under known, steady upstream conditions. Ganymede's magnetosphere becomes even more interesting when compared with other planetary magnetospheres. Using Mach numbers to order magnetospheres from Ganymede to the gas giants, we learn a great deal about the physics relevant to such systems. Even the heliosphere can be fit into the picture. The IBEX spacecraft [McComas et al., 2009] measures the spatial distribution

  19. Substorm simulation: Quiet and N-S arcs preceding auroral breakup

    NASA Astrophysics Data System (ADS)

    Ebihara, Y.; Tanaka, T.

    2016-02-01

    Auroral breakup at the onset of substorm expansion is sometimes preceded by auroral forms known as quiet arcs and N-S arcs. Observations have shown that both the auroral forms tend to move equatorward, and the initial brightening takes place in or near one of the quiet arcs. The auroral forms attract great attention, but generation of auroral forms and their association with the initial brightening are poorly understood. Recent global magnetohydrodynamic simulations are capable of producing upward field-aligned currents (FACs) that resemble the auroral forms in both shape and temporal evolution. Based on the simulation results, we propose the following scenarios: (1) When the convection electric field is weak (northward interplanetary magnetic field (IMF)), the high-pressure region is elongated from the plasma sheet toward higher latitudes and is structured by a coupling between the magnetosphere and the ionosphere (interchange-like instabilities). (2) When the convection electric field is strong (southward IMF), the structured high-pressure region moves equatorward (toward the plasma sheet). Upward currents are generated around it, which can be observed as arcs in the ionosphere. The upward current can be tentatively intensified in the course of the equatorward movement before the formation of a near-Earth neutral line (NENL). (3) The NENL releases magnetic tension and results in the enhancement of plasma pressure at off-equator in the near-Earth region. Sudden formation of the off-equatorial high-pressure region generates the onset current system that manifests initial brightening. Our scenario can explain the observational fact that poleward arcs remained undisturbed at the onset.

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

    SciTech Connect

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

    1992-01-01

    Simultaneous ground-based observations of narrowband and broadband VLF radio waves and of cloud-to-ground lightning were made at widely spaced locations during the 1987 Wave-Induced Particle Precipitation (WIPP) campaign, conducted from Wallops Island, Virginia. Based on these observations, the first case study has been made of the relationships among located cloud-to-ground (CG) lightning flashes, whistlers, and associated ionospheric effects during a substorm particle injection event. This event took place 2 days after the strongest geomagnetic storm of 1987, during a reintensification in geomagnetic activity that did not affect the high rate of whistlers observed at Faraday Station, Antarctica. At the time of the injection event, several intense nighttime thunderstorms were located over Long Island and the coast of New England, between 400 km northwest and 600 km north of the region geomagnetically conjugate to Faraday. About two thirds of the CG flashes that were detected in these thunderstorms during the hour following the injection event onset were found to be causatively associated with whistlers received at Faraday. During the same period the amplitude of the 24.0-kHz signal from the NAA transmitter in Cutler, Maine, propagating over the thunderstorm centers toward Wallops Island was repeatedly perturbed in a manner characteristic of previously reported VLF signatures of transient and localized ionization enhancements at D region altitudes. Though such enhancements may have been caused by whistler-induced bursts electron precipitation from the magnetosphere, the data in this case are insufficient to establish a clear connection between the NAA amplitude perturbations and the Faraday Station whistlers. In view of the proximity of the NAA great circle path to the storm center, having the lower ionosphere by intense radiation from lightning may also have played a role in the observed VLF perturbations.

  1. Acceleration and injection of particles inside the magnetosphere changes during duskward IMF By: statistical approach

    NASA Astrophysics Data System (ADS)

    Yan, X.; Cai, D.; Lembege, B.; Nishikawa, K.

    2005-12-01

    The change of the interplanetary magnetic field (IMF) direction from northward to duskward has an important impact on the inner magnetosphere as analyzed in a recent paper [Yan et al, GRL, to appear] . This impact is analyzed with the help of a new parallel version of the global three-dimensional full particle simulation. As the newly duskward-oriented IMF interacts with the magnetosphere, bands of weak magnetic field (sash) move to the equator (within opposite quadrants), reach lower latitude and merge into each other to form characteristic ``Crosstail-S" structures within the neutral sheet of the magnetotail. The analysis of particle fluxes shows that ``sashs" and ``Crosstail-S" act as magnetic groove to facilitate the entry and injection of magnetosheath particles into the inner magnetosphere. Injected particles are accelerated after the IMF changes its direction from northward to duskward. Characteristic times associated to the changes of the particle dynamics are estimated from the simulations. These informations are thought to be helpful as pre-signatures announcing the triggering of magnetic substorms.

  2. Joule Heating as a Signature of Magnetosphere-Ionosphere-Thermosphere Coupling

    NASA Astrophysics Data System (ADS)

    Ceren Kalafatoglu Eyiguler, Emine; Kaymaz, Zerefsan

    2016-07-01

    Since its first proposal by Birkeland in the early 1900s, the link between magnetosphere and ionosphere (M-I) has been immensely studied but there are still great variety of unsolved problems ranging from how to correctly balance the field aligned current (FAC) closure in the ionosphere to the resulting interactions between ions and neutrals in the ionosphere, and how the ionospheric conductivity and neutral wind control the M-I feedback to the mapping of the ionospheric regions to the magnetotail. It is now well known that during magnetically disturbed periods, the energy deposited to the magnetosphere by the solar wind is partitioned mainly between three domains: the ring current, ionosphere (via auroral particle precipitation and Joule heating) and the plasmoid release in the magnetotail. It is previously found that large part of this transferred energy is in the form of Joule heating which is the increase in ion-neutral collisions due to the increased energy input. However, Joule heating is also affected by the enhanced neutral wind motion during geomagnetic storms and substorms. Thus, it is one of the key manifestations of the M-I-T coupling. In this talk, we first give a through review of the present studies and recent advancements in the M-I-T research area then show the link between the magnetosphere and ionosphere by investigating the activity-time Joule heating variations as well as paying special attention to the neutral wind effects on Joule heating.

  3. Interplanetary Studies: Propagation of Disturbances Between the Sun and the Magnetosphere

    NASA Astrophysics Data System (ADS)

    Dryer, Murray

    1994-09-01

    This review is concerned with the interplanetary ‘transmission line’ between the Sun and the Earth's magnetosphere. It starts with comments about coronal mass ejections (CMEs) that are associated with various forms of solar activities. It then continues with some of the current views about their continuation through the heliosphere to Earth and elsewhere. The evolution of energy, mass, and momentum transfer is of prime interest since the temporal/spatial/magnitude behavior of the interplanetary electric field and transient solar wind dynamic pressure is relevant to the magnetospheric response (the presence or absence of geomagnetic storms and substorms) at Earth. Energetec particle flux predictions are discussed in the context of solar activity (flares, prominence eruptions) at various positions on the solar disk relative to Earth's central meridian. A number of multi-dimensional magnetohydrodynamic (MHD) models, applied to the solar, near-Sun, and interplanetary portions of the ‘transmission line’, are discussed. These model simulations, necessary to advancing our understanding beyond the phenomenological or morphological stages, are directed to deceptively simple questions such as the following: can one-to-one associations be made between specific forms of solar activity and magnetosphere response?

  4. On the origin of falling-tone chorus elements in Earth's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Breuillard, H.; Agapitov, O.; Artemyev, A.; Krasnoselskikh, V.; Le Contel, O.; Cully, C. M.; Angelopoulos, V.; Zaliznyak, Y.; Rolland, G.

    2014-12-01

    Generation of extremely/very low frequency (ELF/VLF) chorus waves in Earth's inner magnetosphere has received increased attention recently because of their significance for radiation belt dynamics. Though past theoretical and numerical models have demonstrated how rising-tone chorus elements are produced, falling-tone chorus element generation has yet to be explained. Our new model proposes that weak-amplitude falling-tone chorus elements can be generated by magnetospheric reflection of rising-tone elements. Using ray tracing in a realistic plasma model of the inner magnetosphere, we demonstrate that rising-tone elements originating at the magnetic equator propagate to higher latitudes. Upon reflection there, they propagate to lower L-shells and turn into oblique falling tones of reduced power, frequency, and bandwidth relative to their progenitor rising tones. Our results are in good agreement with comprehensive statistical studies of such waves, notably using magnetic field measurements from THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft. Thus, we conclude that the proposed mechanism can be responsible for the generation of weak-amplitude falling-tone chorus emissions.

  5. Formation of Kappa Distribution Functions and Eddy Diffusion in the Magnetosphere of the Earth

    NASA Astrophysics Data System (ADS)

    Antonova, Elizaveta; Stepanova, Marina; Kirpichev, Igor; Vovchenko, Vadim; Ovchinnikov, Ilyav

    2016-07-01

    One of the main features of collisionless magnetospheric plasma is the comparatively quick relaxation of distribution functions to kappa distributions. The form of the kappa distribution consists of a Maxwellian core at low energies and a power law spectrum at high energies. Kappa functions describe particle distributions for the systems that are in stationary state but out of thermal equilibrium. Simultaneous determination of the parameters of kappa distributions in different magnetospheric regions is important for understanding the role of different processes of particle acceleration and relaxation of kappa distribution functions to the Maxwellian ones. We analyze the applicability of kappa approximation for different magnetocpheric regions using the data of the Time History of Events and Macroscale Interactions during Substorms spacecraft (THEMIS) mission. We selected events when at least four satellites of THEMIS mission were aligned along the tail between approximately 7 and 30Re. It was found that for the majority of events the values of power index is increased tailwards. We consider such feature as the result of the existence of the inner magnetosphere sources of particle acceleration. We analyze the role of regular bulk transport and the turbulent transport by eddies of different scale in the formation of observed dependences.

  6. First Observations of a Foreshock Bubble at Earth: Implications for Magnetospheric Activity and Energetic Particle Acceleration

    NASA Technical Reports Server (NTRS)

    Turner, D. L.; Omidi, N.; Sibeck, D. G.; Angelopoulos, V.

    2011-01-01

    Earth?s foreshock, which is the quasi-parallel region upstream of the bow shock, is a unique plasma region capable of generating several kinds of large-scale phenomena, each of which can impact the magnetosphere resulting in global effects. Interestingly, such phenomena have also been observed at planetary foreshocks throughout our solar system. Recently, a new type of foreshock phenomena has been predicted: foreshock bubbles, which are large-scale disruptions of both the foreshock and incident solar wind plasmas that can result in global magnetospheric disturbances. Here we present unprecedented, multi-point observations of foreshock bubbles at Earth using a combination of spacecraft and ground observations primarily from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission, and we include detailed analysis of the events? global effects on the magnetosphere and the energetic ions and electrons accelerated by them, potentially by a combination of first and second order Fermi and shock drift acceleration processes. This new phenomena should play a role in energetic particle acceleration at collisionless, quasi-parallel shocks throughout the Universe.

  7. A magnetospheric magnetic field model with flexible current systems driven by independent physical parameters

    NASA Technical Reports Server (NTRS)

    Hilmer, Robert V.; Voigt, Gerd-Hannes

    1995-01-01

    A tilt-dependent magnetic field model of the Earth's magnetosphere with variable magnetopause standoff distance is presented. Flexible analytic representations for the ring and cross-tail currents, each composed of the elements derived from the Tsyganenko and Usmanov (1982) model, are combined with the fully shielded vacuum dipole configurations of Voigt (1981). Although the current sheet does not warp in the y-z plane, changes in the shape and position of the neutral sheet with dipole tilt are consistent with both MHD equilibrium theory and observations. In addition, there is good agreement with observed Delta B profiles and the average equatorial contours of magnetic field magnitude. While the dipole field is rigorously shielded within the defined magnetopause, the ring and cross-tails currents are not similarly confined, consequently, the model's region of validity is limited to the inner magnetosphere. The model depends on four independent external parameters. We present a simple but limited method of simulating several substorm related magnetic field changes associated with the disrupion of the near-Earth cross-tail current sheet and collapse of the midnight magnetotail field region. This feature further facilitates the generation of magnetic field configuration time sequences useful in plasma convection simulations of real magnetospheric events.

  8. The Magnetospheric Multiscale Mission

    NASA Astrophysics Data System (ADS)

    Burch, James

    Magnetospheric Multiscale (MMS), a NASA four-spacecraft mission scheduled for launch in November 2014, will investigate magnetic reconnection in the boundary regions of the Earth’s magnetosphere, particularly along its dayside boundary with the solar wind and the neutral sheet in the magnetic tail. Among the important questions about reconnection that will be addressed are the following: Under what conditions can magnetic-field energy be converted to plasma energy by the annihilation of magnetic field through reconnection? How does reconnection vary with time, and what factors influence its temporal behavior? What microscale processes are responsible for reconnection? What determines the rate of reconnection?
In order to accomplish its goals the MMS spacecraft must probe both those regions in which the magnetic fields are very nearly antiparallel and regions where a significant guide field exists. From previous missions we know the approximate speeds with which reconnection layers move through space to be from tens to hundreds of km/s. For electron skin depths of 5 to 10 km, the full 3D electron population (10 eV to above 20 keV) has to be sampled at rates greater than 10/s. The MMS Fast-Plasma Instrument (FPI) will sample electrons at greater than 30/s. Because the ion skin depth is larger, FPI will make full ion measurements at rates of greater than 6/s. 3D E-field measurements will be made by MMS once every ms. MMS will use an Active Spacecraft Potential Control device (ASPOC), which emits indium ions to neutralize the photoelectron current and keep the spacecraft from charging to more than +4 V. Because ion dynamics in Hall reconnection depend sensitively on ion mass, MMS includes a new-generation Hot Plasma Composition Analyzer (HPCA) that corrects problems with high proton fluxes that have prevented accurate ion-composition measurements near the dayside magnetospheric boundary. Finally, Energetic Particle Detector (EPD) measurements of electrons and

  9. The "Alfvénic surge" at substorm onset/expansion and the formation of "Inverted Vs": Cluster and IMAGE observations

    NASA Astrophysics Data System (ADS)

    Hull, A. J.; Chaston, C. C.; Frey, H. U.; Fillingim, M. O.; Goldstein, M. L.; Bonnell, J. W.; Mozer, F. S.

    2016-05-01

    From multipoint, in situ observations and imaging, we reveal the injection-powered, Alfvénic nature of auroral acceleration during onset and expansion of a substorm. It is shown how Alfvénic variations over time dissipate to form large-scale, inverted-V structures characteristic of quasistatic aurora. This characterization is made possible through the fortuitous occurrence of a substorm onset and expansion phase on field lines traversed by Cluster in the high-altitude acceleration region. Substorm onset was preceded by the occurrence of multiple poleward boundary intensifications (PBIs) and subsequent development/progression of a streamer toward the growth phase arc indicating that this is of the PBI-/streamer-triggered class of substorms. Onset on Cluster is marked by the injection of hot, dense magnetospheric plasma in a region tied to one of the preexisting PBI current systems. This was accompanied by a surge of Alfvénic activity and enhanced inverted-V acceleration, as the PBI current system intensified and striated to dispersive scale Alfvén waves. The growth of Alfvén wave activity was significant (up to a factor of 300 increase in magnetic field power spectral density at frequencies 20 mHz ≲f≲ few hertz) and coincided with moderate growth (factor 3-5) in the background PBI current. This sequence is indicative of a cascade process whereby small-scale/dispersive Alfvén waves are generated from large-scale Alfvén waves or current destabilization. It also demonstrates that the initial PBIs and their subsequent evolution are an intrinsic part of the global auroral substorm response to injection and accompanying wave energy input from the magnetotail. Alfvénic activity persisted poleward of the PBI currents composing a broad Alfvén wave-dominated region extending to the polar cap edge. These waves have transverse scales ranging from a few tens of kilometers to below the ion gyroradius and are associated with large electric fields (up to 200 mV/m) and

  10. A unified approach to inner magnetospheric state prediction

    NASA Astrophysics Data System (ADS)

    Bortnik, J.; Li, W.; Thorne, R. M.; Angelopoulos, V.

    2016-03-01

    This brief technique paper presents a method of reconstructing the global, time-varying distribution of some physical quantity Q that has been sparsely sampled at various locations within the magnetosphere and at different times. The quantity Q can be essentially any measurement taken on the satellite including a variety of waves (chorus, hiss, magnetosonic, and ion cyclotron), electrons of various energies ranging from cold to relativistic, and ions of various species and energies. As an illustrative example, we chose Q to be the electron number density (inferred from spacecraft potential) measured by three Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes between 2008 and 2014 and use the SYM-H index, taken at a 5 min cadence for the 5 h preceding each observed data point as the main regressor, although the predictor can also be any suitable geomagnetic index or solar wind parameter. Results show that the equatorial electron number density can be accurately reconstructed throughout the whole of the inner magnetosphere as a function of space and time, even capturing the dynamics of elementary plasmaspheric plume formation and corotation, suggesting that the dynamics of various other physical quantities could be similarly captured. For our main model, we use a simple, fully connected feedforward neural network with two hidden layers having sigmoidal activation functions and an output layer with a linear activation function to perform the reconstruction. The training is performed using the Levenberg-Marquardt algorithm and gives typical RMS errors of ~1.7 and regression of >0.93, which is considered excellent. We also present a discussion on the different applications and future extensions of the present model, for modeling various physical quantities.

  11. Average patterns of precipitation and plasma flow in the plasma sheet flux tubes during steady magnetospheric convection

    NASA Technical Reports Server (NTRS)

    Sergeev, V. A.; Lennartsson, W.; Pellinen, R.; Vallinkoski, M.; Fedorova, N. I.

    1990-01-01

    Average patterns of plasma drifts and auroral precipitation in the nightside auroral zone were constructed during a steady magnetospheric convection (SMC) event on February 19, 1978. By comparing these patterns with the measurements in the midtail plasma sheet made by ISEE-1, and using the corresponding magnetic field model, the following features are inferred: (1) the concentration of the earthward convection in the midnight portion of the plasma sheet (convection jet); (2) the depleted plasma energy content of the flux tubes in the convection jet region; and (3) the Region-1 field-aligned currents generated in the midtail plasma sheet. It is argued that these three elements are mutually consistent features appearing in the process of ionosphere-magnetosphere interaction during SMC periods. These configurational characteristics resemble the corresponding features of substorm expansions (enhanced convection and 'dipolarized' magnetic field within the substorm current wedge) and appear to play the same role in regulating the plasma flow in the flux tubes connected to the plasma sheet.

  12. The Magnetospheric Multiscale Magnetometers

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Anderson, B. J.; Baumjohann, W.; Bromund, K. R.; Dearborn, D.; Fischer, D.; Le, G.; Leinweber, H. K.; Leneman, D.; Magnes, W.; Means, J. D.; Moldwin, M. B.; Nakamura, R.; Pierce, D.; Plaschke, F.; Rowe, K. M.; Slavin, J. A.; Strangeway, R. J.; Torbert, R.; Hagen, C.; Jernej, I.; Valavanoglou, A.; Richter, I.

    2016-03-01

    The success of the Magnetospheric Multiscale mission depends on the accurate measurement of the magnetic field on all four spacecraft. To ensure this success, two independently designed and built fluxgate magnetometers were developed, avoiding single-point failures. The magnetometers were dubbed the digital fluxgate (DFG), which uses an ASIC implementation and was supplied by the Space Research Institute of the Austrian Academy of Sciences and the analogue magnetometer (AFG) with a more traditional circuit board design supplied by the University of California, Los Angeles. A stringent magnetic cleanliness program was executed under the supervision of the Johns Hopkins University's Applied Physics Laboratory. To achieve mission objectives, the calibration determined on the ground will be refined in space to ensure all eight magnetometers are precisely inter-calibrated. Near real-time data plays a key role in the transmission of high-resolution observations stored on board so rapid processing of the low-resolution data is required. This article describes these instruments, the magnetic cleanliness program, and the instrument pre-launch calibrations, the planned in-flight calibration program, and the information flow that provides the data on the rapid time scale needed for mission success.

  13. Origins of magnetospheric physics

    SciTech Connect

    Van Allen, J.A.

    1983-01-01

    The history of the scientific investigation of the earth magnetosphere during the period 1946-1960 is reviewed, with a focus on satellite missions leading to the discovery of the inner and outer radiation belts. Chapters are devoted to ground-based studies of the earth magnetic field through the 1930s, the first U.S. rocket flights carrying scientific instruments, the rockoon flights from the polar regions (1952-1957), U.S. planning for scientific use of artificial satellites (1956), the launch of Sputnik I (1957), the discovery of the inner belt by Explorers I and III (1958), the Argus high-altitude atomic-explosion tests (1958), the confirmation of the inner belt and discovery of the outer belt by Explorer IV and Pioneers I-V, related studies by Sputniks II and III and Luniks I-III, and the observational and theoretical advances of 1959-1961. Photographs, drawings, diagrams, graphs, and copies of original notes and research proposals are provided. 227 references.

  14. Magnetospheric space plasma investigations

    NASA Technical Reports Server (NTRS)

    Comfort, Richard H.; Horwitz, James L.

    1995-01-01

    Topics and investigations covering this period of this semiannual report period (August 1994 - January 1995) are as follows: (1) Generalized SemiKinetic (GSK) modeling of the synergistic interaction of transverse heating of ionospheric ions and magnetospheric plasma-driven electric potentials on the auroral plasma transport. Also, presentations of GSK modeling of auroral electron precipitation effects on ionospheric plasma outflows, of ExB effects on such outflow, and on warm plasma thermalization and other effects during refilling with pre-existing warm plasmas; (2) Referees' reports received on the statistical study of the latitudinal distributions of core plasmas along the L = 4.6 field line using DE-1/RIMS data. Other work is concerned in the same field, field-aligned flows and trapped ion distributions; and (3) A short study has been carried out on heating processes in low density flux tubes in the outer plasmasphere. The purpose was to determine whether the high ion temperatures observed in these flux tubes were due to heat sources operating through the thermal electrons or directly to the ions. Other investigations center along the same area of plasmasphere-ionosphere coupling. The empirical techniques and model, the listing of hardware calibrated, and/or tested, and a description of notable meetings attended is included in this report, along with a list of all present publication in submission or accepted and those reference papers that have resulted from this work thus far.

  15. Response of the ionosphere thermosphere system to magnetospheric processes

    NASA Astrophysics Data System (ADS)

    Schunk, R. W.; Zhu, L.

    2008-12-01

    The magnetosphere-ionosphere-thermosphere system at high latitudes is strongly coupled via electric fields, particle precipitation, plasma and neutral outflows, and field-aligned currents. Although the climatology of the coupled system is fairly well established, our understanding of the variability of the disturbed state (weather) is rudimentary. This variability is associated with magnetic storms and substorms, nonlinear processes that operate over a range of spatial scales, time delays, and feedback mechanisms between the different domains. The variability and resultant structure of the ionosphere can appear in the form of propagating plasma patches and polar wind jets, pulsing ion and neutral polar winds, auroral and boundary blobs, and ionization channels associated with polar cap arcs, discrete auroral arcs, and storm-enhanced densities (SEDs). The variability and structure of the thermosphere can appear in the form of propagating atmospheric holes, neutral gas fountains, neutral density patches, and transient neutral jets. In addition, during periods of enhanced plasma convection, the neutral winds can become supersonic in relatively narrow regions of the polar cap. The spatial structure in the ionosphere-thermosphere system not only affects the local environment, but the cumulative effect of multiple structures may affect the global circulation and energy balance. A focused topical review of recent results in our modeling the variability and structure of the high-latitude ionosphere-thermosphere system is presented. This review was given at the Greenland Space Science Symposium (May 2007).

  16. Modeling of the Convection and Interaction of Ring Current, Plasmaspheric and Plasma Sheet Plasmas in the Inner Magnetosphere

    NASA Technical Reports Server (NTRS)

    Fok, Mei-Ching; Chen, Sheng-Hsien; Buzulukova, Natalia; Glocer, Alex

    2010-01-01

    Distinctive sources of ions reside in the plasmasphere, plasmasheet, and ring current regions at discrete energies constitute the major plasma populations in the inner/middle magnetosphere. They contribute to the electrodynamics of the ionosphere-magnetosphere system as important carriers of the global current system, in triggering; geomagnetic storm and substorms, as well as critical components of plasma instabilities such as reconnection and Kelvin-Helmholtz instability at the magnetospheric boundaries. Our preliminary analysis of in-situ measurements shoves the complexity of the plasmas pitch angle distributions at particularly the cold and warm plasmas, vary dramatically at different local times and radial distances from the Earth in response to changes in solar wind condition and Dst index. Using an MHD-ring current coupled code, we model the convection and interaction of cold, warm and energetic ions of plasmaspheric, plasmasheet, and ring current origins in the inner magnetosphere. We compare our simulation results with in-situ and remotely sensed measurements from recent instrumentation on Geotail, Cluster, THEMIS, and TWINS spacecraft.

  17. A study of atmosphere-ionosphere-magnetosphere coupling

    NASA Technical Reports Server (NTRS)

    Raitt, W. J.; Paris, J. L.

    1982-01-01

    The properties of low energy plasma in the magnetosphere were predicted. The effects of wave particle interactions involving the concept of plasmons are studied, and quantum mechanical formulations are used for the processes occurring and bulk energization of the low energy plasma are investigated through the concept of the energy momentum tensor for the plasma and its electromagnetic environment.

  18. Quantitative maps of geomagnetic perturbation vectors during substorm onset and recovery

    PubMed Central

    Pothier, N M; Weimer, D R; Moore, W B

    2015-01-01

    We have produced the first series of spherical harmonic, numerical maps of the time-dependent surface perturbations in the Earth's magnetic field following the onset of substorms. Data from 124 ground magnetometer stations in the Northern Hemisphere at geomagnetic latitudes above 33° were used. Ground station data averaged over 5 min intervals covering 8 years (1998–2005) were used to construct pseudo auroral upper, auroral lower, and auroral electrojet (AU*, AL*, and AE*) indices. These indices were used to generate a list of substorms that extended from 1998 to 2005, through a combination of automated processing and visual checks. Events were sorted by interplanetary magnetic field (IMF) orientation (at the Advanced Composition Explorer (ACE) satellite), dipole tilt angle, and substorm magnitude. Within each category, the events were aligned on substorm onset. A spherical cap harmonic analysis was used to obtain a least error fit of the substorm disturbance patterns at 5 min intervals up to 90 min after onset. The fits obtained at onset time were subtracted from all subsequent fits, for each group of substorm events. Maps of the three vector components of the averaged magnetic perturbations were constructed to show the effects of substorm currents. These maps are produced for several specific ranges of values for the peak |AL*| index, IMF orientation, and dipole tilt angle. We demonstrate an influence of the dipole tilt angle on the response to substorms. Our results indicate that there are downward currents poleward and upward currents just equatorward of the peak in the substorms' westward electrojet. Key Points Show quantitative maps of ground geomagnetic perturbations due to substorms Three vector components mapped as function of time during onset and recovery Compare/contrast results for different tilt angle and sign of IMF Y-component PMID:26167445

  19. Investigation of triggering mechanism of substorm through the analysis of Geotail and Themis data

    NASA Astrophysics Data System (ADS)

    Machida, S.; Miyashita, Y.; Ieda, A.; Nose, M.; Angelopoulos, V.; McFadden, J. P.; Auster, H.

    2011-12-01

    In our previous study, we have adopted a superposed epoch analysis method to the Geotail data to understand the triggering mechanism of substorm. Further, we have proposed a new scheme of substorm called "Catapult Current Sheet Relaxation Model" to explain our results. As an extension of these works, we adopted the same method of analysis to the Themis spacecraft data, and found that there are both the same and different characteristics between the results of Themis and Geotail. It is of interest that clear differences are present even if we use the same data set of Themis but adopting different lists of auroral breakups, i.e., substorm onsets. These differences seem to be attributed to the intensity of substorm. Large substorms tend to have southward magnetic field variations related to the plasma sheet thinning which is known as a notable characteristic during a growth phase, near the Earth compared to small substorms. However, the convective earthward flows are weakened just for a few minutes prior to the onset, followed by notable enhancement of the earthward flows after the onset. On the other hand, the southward variations in the magnetic field for small substorms can be seen in the tailward side compared to large substorms. While, the northward magnetic field variations after the onset can be also seen in the tailward side. Furthermore, the earthward convective flows which are not produced by magnetic reconnection seem to develop for moderate class of substorms just prior to the onset. Those differences can be a crucial clue to solve the issue of substorm triggering.

  20. Dynamical complexity of multipoint geospace observations related to magnetosphere-ionosphere coupling

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    We explore, evaluate and compare the applicability, effectiveness and interdisciplinary character of a variety of modern and sophisticated methods, from complex systems sciences, for the investigation of dynamical complexity of the near-Earth electromagnetic environment. We identify and inter-compare complementary analysis concepts, allowing for a systematic study of geospace magnetic storms and magnetospheric substorms and regime shifts between normal and abnormal states of the Earth's magnetic field, based on observational data from both ground and space. We expect these concepts to allow identifying previously unrecognized precursory structures in the dynamical complexity and, thus, contribute to a better understanding of dynamical processes manifested in observable magnetic field fluctuations prior to possible space weather-related hazards.

  1. Analysis of EMIC waves in relation to magnetospheric heavy ion density

    NASA Astrophysics Data System (ADS)

    Kim, H.; Kim, E. H.; Johnson, J.; Lee, D. H.; Clauer, C. R.; Lessard, M.; Engebretson, M. J.; Xu, Z.

    2014-12-01

    This study presents observations of EMIC wave events and their relation to heavy ion density in the magnetosphere. It is well known that EMIC waves play an important role in particle acceleration and loss via wave-particle interaction. It is critical to know the ion composition in the plasma with which EMIC waves interact in order to understand wave generation and propagation because it controls ion cyclotron resonance frequencies of EMIC waves. The presence of heavy ions (He+ and O+) causes the wave modes to be more complex with two additional resonance (ion-ion hybrid and Buchsbaum resonances) and polarization changes, making it challenging to analyze wave generation and propagation. In this study, we show wave polarization and Poynting flux using data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) and Van Allen Probes (VAP) satellites and their ground conjunctions and compare them with the heavy ion density estimated by a wave model.

  2. RESISTIVE SOLUTIONS FOR PULSAR MAGNETOSPHERES

    SciTech Connect

    Li, Jason; Spitkovsky, Anatoly; Tchekhovskoy, Alexander

    2012-02-10

    The current state of the art in the modeling of pulsar magnetospheres invokes either the vacuum or force-free limits for the magnetospheric plasma. Neither of these limits can simultaneously account for both the plasma currents and the accelerating electric fields that are needed to explain the morphology and spectra of high-energy emission from pulsars. To better understand the structure of such magnetospheres, we combine accelerating fields and force-free solutions by considering models of magnetospheres filled with resistive plasma. We formulate Ohm's law in the minimal velocity fluid frame and construct a family of resistive solutions that smoothly bridges the gap between the vacuum and the force-free magnetosphere solutions. The spin-down luminosity, open field line potential drop, and the fraction of open field lines all transition between the vacuum and force-free values as the plasma conductivity varies from zero to infinity. For fixed inclination angle, we find that the spin-down luminosity depends linearly on the open field line potential drop. We consider the implications of our resistive solutions for the spin-down of intermittent pulsars and sub-pulse drift phenomena in radio pulsars.

  3. MESSENGER Observations of Mercury's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Slavin, James A.

    2010-01-01

    During MESSENGER's second and third flybys of Mercury on October 6, 2008 and September 29, 2009, respectively, southward interplanetary magnetic field (IMF) produced intense reconnection signatures in the dayside and nightside magnetosphere and markedly different system-level responses. The IMF during the second flyby was continuously southward and the magnetosphere appeared very active, with large magnetic field components normal to the magnetopause and the generation of flux transfer events at the magnetopause and plasmoids in the tail current sheet every 30 to 90 s. However, the strength and direction of the tail magnetic field was stable. In contrast, the IMF during the third flyby varied from north to south on timescales of minutes. Although the MESSENGER measurements were limited during that encounter to the nightside magnetosphere, numerous examples of plasmoid release in the tail were detected, but they were not periodic. Instead, plasmoid release was highly correlated with four large enhancements of the tail magnetic field (i.e. by factors > 2) with durations of approx. 2 - 3 min. The increased flaring of the magnetic field during these intervals indicates that the enhancements were caused by loading of the tail with magnetic flux transferred from the dayside magnetosphere. New analyses of the second and third flyby observations of reconnection and its system-level effects provide a basis for comparison and contrast with what is known about the response of the Earth s magnetosphere to variable versus steady southward IMF.

  4. On the formation and origin of substorm growth phase/onset auroral arcs inferred from conjugate space-ground observations

    SciTech Connect

    Motoba, T.; Ohtani, S.; Anderson, B. J.; Korth, H.; Mitchell, D.; Lanzerotti, L. J.; Shiokawa, K.; Connors, M.; Kletzing, C. A.; Reeves, G. D.

    2015-10-27

    In this study, magnetotail processes and structures related to substorm 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 Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) at ~780 km in altitude and by the Van Allen Probe B (RBSP-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 magnetospheric counterpart. Our main findings include (1) at the early stage of the growth phase the quiet auroral arc emerged ~4.3° equatorward of the boundary between the downward Region 2 (R2) and upward Region 1 (R1) currents; (2) shortly before the auroral breakup (poleward auroral expansion) the latitudinal separation between the arc and the R1/R2 demarcation narrowed to ~1.0°; (3) RBSP-B observed a magnetic field signature of a local upward field-aligned current (FAC) connecting the arc with the near-Earth tail when the spacecraft footprint was very close to the arc; and (4) the upward FAC signature was located on the tailward side of a local plasma pressure increase confined near L ~5.2–5.4. These findings strongly suggest that the premidnight arc is connected to highly localized pressure gradients embedded in the near-tail R2 source region via the local upward FAC.

  5. On the formation and origin of substorm growth phase/onset auroral arcs inferred from conjugate space-ground observations

    DOE PAGESBeta

    Motoba, T.; Ohtani, S.; Anderson, B. J.; Korth, H.; Mitchell, D.; Lanzerotti, L. J.; Shiokawa, K.; Connors, M.; Kletzing, C. A.; Reeves, G. D.

    2015-10-27

    In this study, magnetotail processes and structures related to substorm 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 Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) at ~780 km in altitude and by the Van Allen Probe B (RBSP-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 arcmore » location relative to large-scale Birkeland currents and of the magnetospheric counterpart. Our main findings include (1) at the early stage of the growth phase the quiet auroral arc emerged ~4.3° equatorward of the boundary between the downward Region 2 (R2) and upward Region 1 (R1) currents; (2) shortly before the auroral breakup (poleward auroral expansion) the latitudinal separation between the arc and the R1/R2 demarcation narrowed to ~1.0°; (3) RBSP-B observed a magnetic field signature of a local upward field-aligned current (FAC) connecting the arc with the near-Earth tail when the spacecraft footprint was very close to the arc; and (4) the upward FAC signature was located on the tailward side of a local plasma pressure increase confined near L ~5.2–5.4. These findings strongly suggest that the premidnight arc is connected to highly localized pressure gradients embedded in the near-tail R2 source region via the local upward FAC.« less

  6. Two satellite study of substorm expansion near geosynchronous orbit

    NASA Astrophysics Data System (ADS)

    Holter, Ø.; Galopeau, P.; Roux, A.; Perraut, S.; Pedersen, A.; Korth, A.; Bösinger, T.

    2004-12-01

    During several time intervals in 1979-1980 the satellites GEOS-2 and SCATHA were situated relatively close on the nightside of the Earth at geosynchronous distances. Several substorm events were identified during these periods. The event considered in this paper was recorded on 22 May 1979, when the satellites were separated by less than 30min in local time around 21:00 LT. The observed 45 to 60 s delay of magnetic signatures observed at the two s/c indicates a westward expansion of ~7.7°/min. At the two s/c, the magnetic signatures are, in particular for the azimuthal magnetic field components, quite different. At GEOS-2, being close to the magnetic equator, the dominant feature is a dipolarization with a weak field-aligned current signature corresponding to a symmetric current which cancels at the equator. On SCATHA, however, being close to the current sheet boundary, the azimuthal magnetic field indicates a strong field-aligned Birkeland current structure. On both s/c the first indication of an approaching substorm was an increase in the high energy ion flux followed by a reduction in the flux intensity of energetic electrons and a further tailward stretching of the magnetic field, starting ~2min before the onset of the magnetic field dipolarization. The tailward stretching, the observed variations of the magnetic field components, and the subsequent dipolarization are interpreted in terms of an azimuthally tilted field-aligned current system passing the s/c on the tailward side from east to west. The westward expansion and dipolarization observed at the two s/c are consistent with the propagation of a Rayleigh-Taylor type instability. The increased radial ion flux corresponds to the ExB-drift due to the substorm associated electric field.

  7. On the velocity distribution of ion jets during substorm recovery

    NASA Technical Reports Server (NTRS)

    Birn, J.; Forbes, T. G.; Hones, E. W., Jr.; Bame, S. J.; Paschmann, G.

    1981-01-01

    The velocity distribution of earthward jetting ions that are observed principally during substorm recovery by satellites at approximately 15-35 earth radii in the magnetotail is quantitatively compared with two different theoretical models - the 'adiabatic deformation' of an initially flowing Maxwellian moving into higher magnetic field strength (model A) and the field-aligned electrostatic acceleration of an initially nonflowing isotropic Maxwellian including adiabatic deformation effects (model B). The assumption is made that the ions are protons or, more generally, that they consist of only one species. It is found that both models can explain the often observed concave-convex shape of isodensity contours of the distribution function.

  8. Magnetospheres of the outer planets. Progress report

    SciTech Connect

    Van Allen, J.A.

    1985-04-01

    The physical conditions that are necessary for the existence of a planetary magnetosphere are reviewed. These general considerations and some specific evidence are then combined to make forecasts of the probable existence and nature of magnetospheres of Uranus and Neptune.

  9. Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times.

    PubMed

    Shi, Q Q; Zong, Q-G; Fu, S Y; Dunlop, M W; Pu, Z Y; Parks, G K; Wei, Y; Li, W H; Zhang, H; Nowada, M; Wang, Y B; Sun, W J; Xiao, T; Reme, H; Carr, C; Fazakerley, A N; Lucek, E

    2013-01-01

    An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times. PMID:23403567

  10. Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times.

    PubMed

    Shi, Q Q; Zong, Q-G; Fu, S Y; Dunlop, M W; Pu, Z Y; Parks, G K; Wei, Y; Li, W H; Zhang, H; Nowada, M; Wang, Y B; Sun, W J; Xiao, T; Reme, H; Carr, C; Fazakerley, A N; Lucek, E

    2013-01-01

    An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times.

  11. Unipolar induction in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1972-01-01

    A theory is described for the production of electric currents in the magnetosphere and for the transfer of energy from the solar wind to the magnetosphere. Assuming that the magnetosheath has ohmic-type conduction properties, it is shown that unipolar induction can energize several current flows, explaining the correlation of the east-west component of the interplanetary magnetic field with polar electric fields and polar magnetic variations. In the tail region, unipolar induction can account for effects correlated with the north-south component of the interplanetary magnetic field.

  12. The Inner Magnetosphere Imager mission

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.

    1994-01-01

    The Inner Magnetosphere Imager (IMI) mission will carry instruments to globally image energetic neutral atoms, far and extreme ultraviolet light, and X-rays. These imagers will see the ring current, inner plasmasheet, plasmasphere, aurora, and geocorona. With these observations it will be possible, for the first time, to develop an understanding of the global shape of the inner magnetosphere and the interrelationships between its parts. Seven instruments are currently envisioned on a single spinning spacecraft with a despun platform. IMI will be launched into an elliptical, polar orbit with an apogee of approximately 7 Earth radii altitude and perigee of 4800 km altitude.

  13. The Inner Magnetosphere Imager Mission

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.

    1994-01-01

    The Inner Magnetosphere Imager (IMI) mission will carry instruments to globally image energetic neutral atoms, far and extreme ultraviolet light, and X rays. These imagers will see the ring current inner plasmasheet, plasmasphere, aurora, and geocorona. With these observations it will be possible, for the first time, to develop an understanding of the global shape of the inner magnetosphere and the interrelationships between its parts. Seven instruments are currently envisioned on a single spinning spacecraft with a despun platform. IMI will be launched into an elliptical, polar orbit with an apogee of approximately 7 Earth radii altitude and perigee of 4800 km altitude.

  14. Configuration of the Jovian magnetosphere

    NASA Technical Reports Server (NTRS)

    Hill, T. W.; Dessler, A. J.; Michel, F. C.

    1974-01-01

    A model is presented in which the Jovian magnetosphere is severely inflated by the centrifugal stress of partially corotating plasma streaming out along field lines from the ionosphere. The model is consistent with observations reported from the Pioneer 10 encounter, including the disk-like field configuration, the diurnal modulation of trapped-particle fluxes, and the inferred departure from rigid corotation in the outer magnetosphere. The field configuration is closed on the dayside, but on the nightside the plasma can force the magnetic field open to form a planetary wind flowing in the antisolar direction.

  15. Plasma convection in Neptune's magnetosphere

    NASA Technical Reports Server (NTRS)

    Selesnick, R. S.

    1990-01-01

    The magnetosphere of Neptune changes its magnetic configuration continuously as the planet rotates, leading to a strong modulation of the convection electric field. Even though the corotation speed is considerably larger, the modulation causes the small convection speed to have a cumulative effect, much like the acceleration of particles in a cyclotron. A model calculation shows that plasma on one side of the planet convects out of the magnetosphere in a few planetary rotations, while on the other side it convects slowly planetward. The observation of nitrogen ions from a Triton plasma torus may provide a critical test of the model.

  16. Global MHD simulations of Neptune's magnetosphere

    NASA Astrophysics Data System (ADS)

    Mejnertsen, L.; Eastwood, J. P.; Chittenden, J. P.; Masters, A.

    2016-08-01

    A global magnetohydrodynamic (MHD) simulation has been performed in order to investigate the outer boundaries of Neptune's magnetosphere at the time of Voyager 2's flyby in 1989 and to better understand the dynamics of magnetospheres formed by highly inclined planetary dipoles. Using the MHD code Gorgon, we have implemented a precessing dipole to mimic Neptune's tilted magnetic field and rotation axes. By using the solar wind parameters measured by Voyager 2, the simulation is verified by finding good agreement with Voyager 2 magnetometer observations. Overall, there is a large-scale reconfiguration of magnetic topology and plasma distribution. During the "pole-on" magnetospheric configuration, there only exists one tail current sheet, contained between a rarefied lobe region which extends outward from the dayside cusp, and a lobe region attached to the nightside cusp. It is found that the tail current always closes to the magnetopause current system, rather than closing in on itself, as suggested by other models. The bow shock position and shape is found to be dependent on Neptune's daily rotation, with maximum standoff being during the pole-on case. Reconnection is found on the magnetopause but is highly modulated by the interplanetary magnetic field (IMF) and time of day, turning "off" and "on" when the magnetic shear between the IMF and planetary fields is large enough. The simulation shows that the most likely location for reconnection to occur during Voyager 2's flyby was far from the spacecraft trajectory, which may explain the relative lack of associated signatures in the observations.

  17. Overview of Results from the Cassini Magnetospheric Imaging Instrument (MIMI) During the First Year of Operations

    NASA Technical Reports Server (NTRS)

    Krimigis, S. M.; Mitchell, D. G.; Hamilton, D. C.; Krupp, N.; Livi, S.; Roelof, E. C.; Dandouras, J.; Mauk, B. H.; Brandt, J. P.; Paranicas, C.

    2005-01-01

    The MIMI investigation comprises three sensors covering the indicated energy ranges: the Ion and Neutral Camera (INCA) -- 7 keV/nuc Magnetospheric Measurement System (LEMMS) 0.02 3 Mev) and protons (1.6 < E < 160 Mev) from the back end of the dual field-of-view telescope. The Saturn observation sequences began in January, 2004 and culminated in Saturn Orbit Insertion on July 1, 2004. The MIMI sensors observed substantial activity in interplanetary space for several months prior to SOI, including several interplanetary shocks associated with corotating interaction regions, numerous increases most likely originating from particle streams in the vicinity of the Saturnian bow shock and energetic neutral atoms (ENA) emanating from Saturn s magnetosphere. Results following SOI revealed: a dynamical magnetosphere with a day-night asymmetry and an 11-hour periodicity; several water-product ions (O+, OH+, H2O+), but little N+; inferred quantities of neutral gas sufficient to cause major losses in the trapped ions and electrons in the middle and inner magnetosphere; a Titan exosphere that is a copious source of ENA; INCA imaging through ENA has also revealed a previously unknown radiation belt residing inward of the D-ring that is most likely the result of double charge-exchange between the main radiation belt and the upper layers of Saturn s exosphere. Finally, there is ample evidence for the presence of substorm-like injections of plasma that subsequently corotates for a number of days before dissipating on the night-side magnetotail. The observations will be presented and discussed in the context of current theoretical models.

  18. Interplanetary Magnetic Field Control of the Entry of Solar Energetic Particles into the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Richard, R. L.; El-Alaoui, M.; Ashour-Abdalla, M.; Walker, R. J.

    2002-01-01

    We have investigated the entry of energetic ions of solar origin into the magnetosphere as a function of the interplanetary magnetic field orientation. We have modeled this entry by following high energy particles (protons and 3 He ions) ranging from 0.1 to 50 MeV in electric and magnetic fields from a global magnetohydrodynamic (MHD) model of the magnetosphere and its interaction with the solar wind. For the most part these particles entered the magnetosphere on or near open field lines except for some above 10 MeV that could enter directly by crossing field lines due to their large gyroradii. The MHD simulation was driven by a series of idealized solar wind and interplanetary magnetic field (IMF) conditions. It was found that the flux of particles in the magnetosphere and transport into the inner magnetosphere varied widely according to the IMF orientation for a constant upstream particle source, with the most efficient entry occurring under southward IMF conditions. The flux inside the magnetosphere could approach that in the solar wind implying that SEPs can contribute significantly to the magnetospheric energetic particle population during typical SEP events depending on the state of the magnetosphere.

  19. Electron acceleration in the near-Earth magnetotail in substorms

    NASA Astrophysics Data System (ADS)

    Asano, Y.; Shinohara, I.; Retino, A.; Daly, P.; Kronberg, E.; Khotyaintsev, Y.; Vaivads, A.; Owen, C. J.; Fazakerley, A. N.; Nakamura, R.; Baumjohann, W.; Nagai, T.; Takada, T.; Miyashita, Y.; Fujimoto, M.; Lucek, E. A.; Reme, H.

    2008-12-01

    We investigate substorm events in the near-Earth magnetotail in order to examine acceleration signatures of electrons using data from the Cluster satellites with separation larger than 1 RE. Thermal electrons detected by the PEACE instrument and the high-energy electron flux from the RAPID instrument are analyzed and compared with simultaneous magnetic field, electric field, and ion observations from FGM, EFW, and CIS instruments, respectively. It is found that electrons with energies up to a few hundreds keV exhibit the hardest spectra in the initial stage of the events. These electrons are associated with fast Earthward ion flows and the enhancement of the dipolar magnetic field and the electric field. Although most of the distributions are isotropic, electrons sometimes show the preferential increase of the perpendicular flux, suggesting the effect of betatron acceleration. These electron signatures last only for about one minute, and after that either the flux quickly decreases or a more isotropic flux is observed. The spectra gradually become softer in the course of substorms, and the spectra are softer than the initial state in some cases. The soft spectra are sometimes associated with the temporal drop of the perpendicular electrons. The larger flux is observed by the satellite closer to the Earth, while the satellite on the tailward side shows a faster response to magnetotail perturbations. We discuss possible acceleration mechanisms and the flux transport in the magnetotail.

  20. Analysis of a Prototypical Substorm with Conjugate Ground Magnetic Data

    NASA Astrophysics Data System (ADS)

    Connors, M. G.; Engebretson, M. J.; Chu, X.; Gjerloev, J. W.; Angelopoulos, V.; McPherron, R. L.; Weatherwax, A. T.

    2015-12-01

    The substorm at about 5 UT on February 26, 2008 (Angelopoulos et al., Science, 2008) has been taken as prototypical of reconnection in the Near-Earth Neutral Line model. Further examination by Pu et al. (JGR, 2010) showed that the event was preceded an hour earlier by one with very similar signatures. Traditional use of AE-related indices suggests that the first event was smaller in terms of electric currents than the second. More detailed examination of ground magnetic data shows that it was in fact comparable: in addition, the second event was considerably further to the west. We present results from Automated Meridian Modeling showing that a simple electrojet model with only three parameters (electrojet borders and current) matches data well with approximately 0.2 MA cross-meridian current in both subevents. There was also good conjugacy between hemispheres for both, as indicated by Antarctic magnetometers and inversion based on them. SuperMag data gives dense enough magnetometer coverage that the layout of the substorm current wedge, with auroral zone westward electrojet and subauroral perturbations mainly due to field-aligned current, can be determined. The quantitative data from the ground provides a context in which flows, magnetic fields, and other parameters at the THEMIS constellation and other conjugate spacecraft may be interpreted.

  1. Role of inductive electric fields in substorm development

    NASA Technical Reports Server (NTRS)

    Heikkila, Walter J.

    1992-01-01

    A study discussing and investigating the role of inductive electric fields in substorm development is presented. It is common to use the scalar potential phi to calculate the electrostatic field E(sup ES)-(inverted Delta)(phi). However, vector potential A has not been extensively used to analyze results by the relation for the inductive electric field E(sup IND)-delta A/delta t. Because of the weak dependence in distance (1/r) these potentials show the effect of distant sources, unlike MHD (Magnetohydrodynamic) theory which is strictly local. The two can be separated by the choice of the Coulomb (transverse) gauge. It is proper to consider that the plasma polarizes to counteract the activation of the inductive electric field; this is a matter of cause and effect. However, such polarization produces a curl free electrostatic field and thus cannot alter the electromotive force due to induction. This idea has some interesting consequences for plasma physics, including violations of MHD theory, creation of the substorm current diversion, and a fresh look at dayside merging via plasma transfer events.

  2. Quantitative maps of geomagnetic perturbation vectors during substorm onset and recovery

    NASA Astrophysics Data System (ADS)

    Pothier, N. M.; Weimer, D. R.; Moore, W. B.

    2015-02-01

    We have produced the first series of spherical harmonic, numerical maps of the time-dependent surface perturbations in the Earth's magnetic field following the onset of substorms. Data from 124 ground magnetometer stations in the Northern Hemisphere at geomagnetic latitudes above 33° were used. Ground station data averaged over 5 min intervals covering 8 years (1998-2005) were used to construct pseudo auroral upper, auroral lower, and auroral electrojet (AU*, AL*, and AE*) indices. These indices were used to generate a list of substorms that extended from 1998 to 2005, through a combination of automated processing and visual checks. Events were sorted by interplanetary magnetic field (IMF) orientation (at the Advanced Composition Explorer (ACE) satellite), dipole tilt angle, and substorm magnitude. Within each category, the events were aligned on substorm onset. A spherical cap harmonic analysis was used to obtain a least error fit of the substorm disturbance patterns at 5 min intervals up to 90 min after onset. The fits obtained at onset time were subtracted from all subsequent fits, for each group of substorm events. Maps of the three vector components of the averaged magnetic perturbations were constructed to show the effects of substorm currents. These maps are produced for several specific ranges of values for the peak |AL*| index, IMF orientation, and dipole tilt angle. We demonstrate an influence of the dipole tilt angle on the response to substorms. Our results indicate that there are downward currents poleward and upward currents just equatorward of the peak in the substorms' westward electrojet.

  3. Open flux in Saturn’s magnetosphere

    NASA Astrophysics Data System (ADS)

    Badman, Sarah V.; Jackman, Caitriona M.; Nichols, Jonathan D.; Clarke, John T.; Gérard, Jean-Claude

    2014-03-01

    We characterise the interaction between the solar wind and Saturn’s magnetosphere by evaluating the amount of ‘open’ magnetic flux connected to the solar wind. This is deduced from a large set of Hubble Space Telescope images of the ultraviolet aurora, using the poleward boundary of the main aurora as a proxy for the open-closed field line boundary in the ionosphere. The amount of open flux is found to be 10-50 GWb, with a mean of 35 GWb. The typical change in open flux between consecutive observations separated by 10-60 h is -5 or +7 GWb. These changes are a result of imbalance between open flux creation at the dayside magnetopause and its closure in the magnetotail. The 5 GWb typical decrease in open flux is consistent with in situ measurements of the flux transported following a reconnection event. Estimates of average, net reconnection rates are found to be typically a few tens of kV, with some extreme examples of unbalanced magnetopause or tail reconnection occurring at ∼300 kV. The range of values determined suggest that Saturn’s magnetosphere does not generally achieve a steady state between flux opening at the magnetopause and flux closure in the magnetotail. The percentage of magnetic flux which is open in Saturn’s magnetosphere is similar to that measured at the Earth (2-11%), but the typical percentage that is closed between observations is significantly lower (13% compared to 40-70%). Therefore, open flux is usually closed in smaller (few GWb) events in Saturn’s magnetosphere. The exception to this behaviour is large, rapid flux closure events which are associated with solar wind compressions. While the rates of flux opening and closure should be equal over long timescales, they are evidently different on shorter (up to tens of hours) timescales. The relative independence of the magnetopause and tail reconnection rates can be attributed to the long loading timescales required to transport open field lines into the tail.

  4. Ion Acceleration at Injection Fronts in the Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Ukhorskiy, A. Y.; Sitnov, M. I.; Gkioulidou, M.; Merkin, V. G.; Artemyev, A.

    2014-12-01

    During geomagnetic storms a large volume of ions are transported from the magnetotail deep into the inner magnetosphere leading to ion acceleration to the energies of tens to hundreds keV. Energized ions become the dominant source of plasma pressure in the inner magnetosphere. Hot plasma pressure drives large electrical currents which determine global electrodynamics and coupling of the inner magnetosphere-ionosphere system. Recent analysis of ion measurements from the RBSPICE experiment of the Van Allen Probes mission showed that the buildup of plasma pressure in the inner magnetosphere largely occurs in the form of localized discrete injections similar to dipolarization fronts observed in the magnetotail. According to previous studies, in the magnetotail ions can be rapidly energized to ~100 keV in the process of nonlinear trapping enabled by magnetic field reconnection and/or an electrostatic field ahead of dipolarization fronts. It is not clear whether similar processes can operate in the inner magnetosphere where the ambient magnetic field is much higher and the propagation speeds of injection fronts are much lower. The goal of this paper is to investigate the mechanisms of ion energization at injection fronts in the inner magnetosphere with the use three-dimensional test-particle simulations and the comparison with ion measurements at RBSPICE. For this purpose we construct an analytical model of the electric and magnetic field perturbations associated with the injection fronts which are superimposed onto the ambient magnetic field. The model reproduces characteristic properties of injection fronts derived from spacecraft measurements and particle-in-cell kinetic simulations.

  5. Wave emissions from planetary magnetospheres

    NASA Technical Reports Server (NTRS)

    Grabbe, Crockett L.

    1989-01-01

    An important development in the Earth magnetosphere was the discovery of the boundary of the plasma sheet and its apparent role in the dynamics of the magnetotails. Three instabilities (negative energy mode, counterstreaming, and the Buneman instability) were investigated through analytical and numerical studies of their frequency and growth rate as a function of the angle of propagation.

  6. Physics of magnetospheric boundary layers