Winslow , 1 Harlan E. Spence , 1, 2 and Nathan A. Schwadron 1, 2. Charles J. Reka M. Harlan E. Nathan A. Author information Article notes Copyright and License information Disclaimer. Received Apr 29; Accepted Aug This work is licensed under a Creative Commons Attribution 4. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material.
Open in a separate window. Figure 1. Solar wind measurements and geomagnetic indices on 17—18 January Results Bow shock and magnetopause locations To determine the location of the bow shock and magnetopause, we used a combination of satellite crossings and typical models for their location 1 , 2 as shown in Fig. Figure 2.
Measured and modeled magnetopause black and bow shock red nose locations. Figure 3. Dayside magnetospheric and solar wind measurements. Radiation belt measurements Measurements in the radiation belts further confirm that the state of Earth's inner magnetosphere was far from typical. Figure 4. Measurements of energetic electrons in the radiation belts. Figure 5.
Long-term measurements of relativistic electrons in the radiation belts. Additional information How to cite this article: Lugaz, N. Peer Review File: Click here to view. Footnotes Author contributions N. References Shue J. Magnetopause location under extreme solar wind conditions. Determining the standoff distance of the bow shock: Mach number dependence and use of models.
Anomalous magnetosheath properties during Earth passage of an interplanetary magnetic cloud. Altered solar wind-magnetosphere interaction at low Mach numbers: coronal mass ejections. Hot Jupiters and hot spots: the short- and long-term chromospheric activity on stars with giant planets. Magnetospheric structure and atmospheric joule heating of habitable planets orbiting M-dwarf stars. Solar Phys. Space Sci. Downstream structures of interplanetary fast shocks associated with coronal mass ejections.
Planar magnetic structures in coronal mass ejection-driven sheath regions. The location of low Mach number bow shocks at Earth. Is the magnetopause Rayleigh-Taylor unstable sometimes? A sub-Alfvenic solar wind—Interplanetary and magnetosheath observations. Scaling of asymmetric magnetic reconnection: general theory and collisional simulations.
Physics of Plasmas 14 , Day the solar wind almost disappeared: magnetic field fluctuations, wave refraction and dissipation. Van Allen Probes observation of localized drift resonance between poloidal mode ultra-low frequency waves and 60 keV electrons.
Simulation of Van Allen Probes plasmapause encounters. It is generally suggested that this seed population is later accelerated due to wave—particle interactions, with different wave modes producing powerful fluxes of relativistic electrons. The most developed model considers whistler-mode chorus waves as a main source of acceleration. However, such processes strongly depend on the amplitudes of the observed waves and require comparatively long time, which is much larger than the timescale of substorms.
In particular, Horne et al. Similarly, Thorne et al. The theory is based on the suggestion that the process of acceleration may be described as the diffusion using the two-dimensional Fokker—Planck equation. The developed model can reproduce observed timing, magnitude, energy and pitch angle distribution of relativistic electron phase space density PSD obtained using Van Allen Probes observations and Tsyganenko and Sitnov model of storm time magnetic field distribution. However, the developed model does not take into account possible contribution of nonlinear processes see, for example Omura and Summers ; Demekhov et al.
It is also well known that during storms and large substorms, the whole auroral oval is filled by electrostatic and electromagnetic fluctuations with large amplitudes at different frequency ranges. Therefore, the simultaneous observations of chorus waves and relativistic electrons may mean that both phenomena develop in the same region but not necessarily have a cause—effect relationship. This is why it is interesting to analyze other possibilities. For example, Shklyar and Kliem showed that interactions of relativistic electrons with upper hybrid waves could significantly change the electron dynamics.
Variations of the magnetic field inside the ring current region are also not well known yet. Kim and Chan studied the role of purely adiabatic processes assuming the conservation of all three adiabatic invariants for storm time relativistic flux dynamics and showed that the simple conservation of these invariants during storms can explain most drops in the relativistic electron fluxes observed at geosynchronous orbit during storms.
However, the obtained result strongly depends on the magnetic field model in use. Nevertheless, it clearly indicates that the impact of magnetic field variations on the dynamics of relativistic electrons cannot be neglected.
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For example, it is possible to suggest that the injection of electrons with a power-law energy spectrum in the region of depressed by ring current magnetic field can lead to the appearance of large fluxes of relativistic electrons when the magnetic field restores after the storm. Such possibility was discussed by Tverskoy and Antonova They proposed that the fluxes of ORB electrons can increase due to substorm injections of seed population electrons into the region of the magnetic field depressed by the storm time ring current. Later these electrons are adiabatically accelerated during the storm recovery phase when the magnetic field turns back to the pre-storm level.
Here c is the coefficient of proportionality equal to 2. The Tverskaya relation has been validated by many researches for magnetic storms with well-defined main and recovery phases see Tverskaya ; Kuznetsov et al. Recently, Antonova and Stepanova proved this relation for the October magnetic storm, an event in which the position of the ORB maximum maximum of the phase space density of relativistic electrons after the storm was clearly determined by Reeves et al.
Antonova and Stepanova also showed that for this storm some other important predictions are valid: a sharp peak of plasma pressure and the equatorial boundary of the westward electrojet, both located near L max. Theoretical suggestions about the role of substorm activity during storms and the action of adiabatic mechanisms of electron acceleration have not been verified yet.
In this work, we discuss the potential importance of the role of substorm activity in the electron acceleration but do not analyze it in detail. We also try to evaluate the role of adiabatic processes in the acceleration of ORB electrons at comparatively low latitudes. The paper is organized as follows: in the data analysis section, we first examine high-energy electron fluxes and substorm activity during the storm recovery phase of 78 storms, using data of the Van Allen Probes mission.
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We then analyze the variations of relativistic electron fluxes for magnetic storm where the electron flux after the storm was similar to the pre-storm flux. Last sections are dedicated to discussion and conclusions. Black line on panels b and c indicate the L -shell with maximum electron flux at any given time bin during each event. We are expanding the analysis in Moya et al. Vertical blue dashed line marks the time of SYM-H minimum. From top to bottom: a the SYM-H index; b , c the differential omnidirectional fluxes of 1.
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The same as in Fig. This storm can be considered as the first type magnetic storm. Such increase is practically coinciding with a comparatively large substorm activity as measured by AL index. ORB depletion starts with the storm main phase onset, and particle fluxes do not recover to the pre-storm levels.
Magnetic storm of September 30, Fig. This storm was analyzed by Turner et al. The ORB losses at large L were explained by outward radial transport and magnetopause shadowing Turner et al.
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Stable character of particle fluxes at the center of ORB was not discussed by Turner et al. In accordance with Turner et al. However, Fig.
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The existence of a period with very low geomagnetic activity during a large portion of the storm recovery phase and the classification of this storm as no-change event regarding the response of relativistic electron fluxes allow us to analyze this event additionally to clarify the possible role of adiabatic effects see below. We checked all 78 storms from Moya et al. Increase in relativistic electron fluxes takes place when storm time substorms are observed during storm recovery phase. In Fig. In addition, following Moya et al. Vertical dashed lines separate the distribution in three groups, according to their average AL index.
Similar numbers are also found for 3. Such finding agrees with Tverskoy and Antonova suggestion that substorm injections during storm recovery phase can lead to appearance of powerful fluxes of relativistic electrons and that the probability of enhancement increases as average AL increases during the recovery phase of a storm. Interestingly, the ratio of fluxes can be relatively lower than expected for the event with the highest AL average, which may suggest a change in the response for extreme events.