Modeling gradual diffusion and prompt changes in radiation belt electron phase space density for the March 2013 Van Allen Probes case study

Two approaches are taken to studying the disparate timescale outer zone electron phenomena which have been identified in March 2013 from Van Allen Probes measurements (Baker et al., 2013). The first is a radial diffusion simulation (Li et al., 2013) which uses an outer boundary constraint based on a statistical model of flux measured by THEMIS at r = 7.5 Re, parameterized by solar wind density and velocity as input (Shin and Lee, 2013). This statistical model has been benchmarked against use of LANL geosynchronous flux for the outer boundary for other CME-driven storms, and both outer boundaries have been tested against GPS measurements at lower L* (Li et al., 2013). In order to investigate flux dropout at higher time resolution on 17 March, MHD test particle simulations were performed. This method uses the Lyon-Fedder-Mobarry global simulation model, coupled with the Rice Convection Model representation of ring current drift physics, to calculate the magnetopause stand-off distance at noon on the dayside, using measured solar wind input at L1 from ACE and Wind. The timescale of the magnetopause evolution in the MHD simulations, when used to advance test particle electron trajectories, includes features which occur on a faster time scale than can be resolved by the radial diffusion code. The two approaches are both compared with data from the ECT instrument on the Van Allen Probes Spacecraft