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[PEM16-19] Energy and L dependence of relativistic electron variations in the outer radiation belt during the recovery phases of magnetic storms: Arase/XEP observations
Keywords:Arase, ERG, XEP, radiation belts
In order to investigate the electron acceleration processes, we examine variations of relativistic electrons based on observations by the extremely high-energy electron experiments (XEP) onboard the Arase satellite during six geomagnetic storms that occurred on March 21, March 27, April 4, May 28, September 8 and September 27 2017, respectively. XEP onboard Arase measures electrons in the energy range from 400 keV to 20 MeV. In this study, we focus on time variations of the flux profile of the fixed magnetic moments as a function of the geocentric distance at the magnetic equatorial plane (L), which gives the essential clues to understand the acceleration locations [e.g., Green and Kivelson, 2004]. In events on March 21 and on September 27, relativistic electrons in the outer belt showed a typical time variation, i.e., decrease in the main phase and then increase in the recovery phase under 1.2 MeV. In events on March 27, on May 28 and on September 8, relativistic electrons in the outer belt showed a typical time variation, i.e., decrease in the main phase and then increase in the recovery phase for all energies up to 5MeV. In events on April 4, flux of electrons in the recovery phase is equal to flux before geomagnetic storm.
The timing and location of the flux recovery/increase during the recovery phases depend on storms. Detailed characteristics such as the energy and L dependences and their comparison between the geomagnetic storms will be also reported.
Green, J. C., and M. G. Kivelson (2004), J. Geophys. Res. 109, A03213.
Reeves, G. D., K. L. McAdams, R. H. W. Friedel, T. P. O’Brien (2003), Geophys. Res. Lett. 30, 1529.