Advective process modeling for radiation belt electrons

Abstract:

The relativistic electron dynamics in the radiation belts falls into two categories: diffusive process, in which particles are scattered randomly, and advective process, in which particles are collectively driven in one direction in energy or space. In this work, we include both effects by adding an advection term in the Fokker-Planck equation. Test-particle simulation is done in the electric and magnetic fields generated by LFM global MHD model, and the advection coefficient is calculated. Then, we apply the advection coefficient to the Fokker-Planck equation with advection term and solve for phase space density. March 1991 CME-driven storm, which shows strong injection of relativistic electrons for all energy up to the 10-30 MeV channel, is used as an example to demonstrate our method. The result shows inward motion of electrons for all first invariant, with the phase space density increasing by two orders of magnitude at L=2.5.