Energetic electron response to the March 1 storm: coordinated observations between Van Allen Probes and THEMIS spacecraft

Earth's outer radiation belt is highly dynamic. The mechanisms responsible for the source, loss and transport of outer radiation belt electrons have long been a subject of intense study. Here we examine the energetic electron response to the 1 March 2013 geomagnetic storm using coordinated observations by both Van Allen Probes and THEMIS spacecraft. The storm was moderate with Dst reaching as low as -50 nT, followed by an extended quiet period (several days). The Van Allen Probes and THEMIS spacecraft were located at ~02 and ~09 MLT, respectively, and measured both fields and particles. Electron phase space densities (PSD) are estimated from the electron flux observations made by the RBSPICE instrument of the Van Allen Probes and from the SST instrument of THEMIS, utilizing a series of Tsyganenko magnetic field models to calculate adiabatic invariants. Whistler-mode and ULF wave powers are calculated from the observations of electric and magnetic fields on both missions. The initial results show that the PSDs of the energetic electrons between 100 and 700 keV increased by an order of magnitude within less than a day during the main phase compared to the pre-storm level, followed by slow decay for the rest of the recovery phase. Strong whistler-mode waves with wave frequency in the band 0.1-0.8 fce (where fce is the electron gyrofrequency) were present during the main phase and diminished significantly soon after Dst reached minimum. In contrast, the upper boundary of hiss waves moved down in spatial extent to L* ~ 3.5 during the main phase and extended to L* ~ 4.5 for about 5 days after the Dst minimum. Loss rates after the PSD peak are L*- and energy-dependent and may have two distinct lifetimes: they are faster initially and then become slower. These dependences appear to have a good correlation with the hiss activity. We investigate and discuss the contribution of the various acceleration and/or loss mechanisms to the PSD variation using the coordinated observations.