Modeling the Magnetopause Shadowing Loss During the June 2015 Dropout Event

Fast dropout of relativistic and ultrarelativistic electrons at both high and low L* regions were observed during the intense coronal mass ejection driven storm in June 2015. An improved radial diffusion model, using an event-specific last closed drift shell and newly available radial diffusion coefficients (D-LL), is implemented to simulate the magnetopause shadowing loss of electrons. The model captures the fast shadowing loss of electrons well at high L* regions after both interplanetary shocks, and reproduces the initial adiabatic loss of the high-energy storage ring at low L* regions after the second strong shock. We show for the first time that using the event-specific and K-dependent last closed drift shell and improved D-LL is critical to reproduce the observed dropout features, including the timing, location, and the butterfly electron pitch angle distribution. Future inclusion of the electromagnetic ion cyclotron wave scattering process is needed to model the observed further depletion of the storage ring.