Phase space density distributions of energetic electrons in the outer radiation belt during two Geospace Environment Modeling Inner Magnetosphere/Storms selected storms

The phase space density distributions of energetic electrons during two storm periods, including the two storms on 21-23 October 2001 and 4-9 September 2002 selected by Geospace Environment Modeling Inner Magnetosphere/ Storms campaign as the radiation belt assessment challenge in 2004 workshop, are presented in this paper. Electron data from the Synchronous Orbit Particle Analysis instrument aboard three Los Alamos National Laboratory geosynchronous satellites as well as the Comprehensive Energetic Particle and Pitch Angle Distribution instrument aboard Polar are used. The Tsyganenko 2001 storm model is chosen for the storm time magnetic field presentation, compared to the best-fitting magnetic model achieved in a previous study. By tracing the temporally evolving radial distributions, we conclude that while the dropout of electron phase space density during storm main phases appears to be energy-independent, the enhancement in recovery phases shows an energy-dependent pattern. The average outwardly decreasing radial gradients of phase space density obtained during the recovery phases of the two storm periods strongly suggest the in situ acceleration is most likely the main source of new energetic electrons, along with a possible contribution from an external source.