Chorus-Driven Outer Radiation Belt Electron Dynamics at Different L-Shells

Abstract

Energetic outer radiation belt electron phase space density (PSD) evolution due to interaction with whistler-mode chorus at different L-shells is investigated by solving the diffusion equation including cross diffusion terms. It is found that the difference of diffusion rates for different L-shells occurs primarily at pitch angles 0°-50° and around 90°. In particular, diffusion rates for L = 6.5 are found to be 5–10 times larger than that for L = 3.5 at these pitch angles. In the presence of cross terms, PSD for ∼ MeV electrons after 24 h decreases by about 25, 12, 10 and 8 times at L = 3.5, 4.5, 5.5 and 6.5 near the loss cone, and increases by about 55, 45, 30 and 20 times at larger pitch angles, respectively. After 24 h, the ratios between ∼ MeV electron PSDs from simulations without and with cross diffusion at L = 3.5, 4.5, 5.5 and 6.5 are about 350, 600, 800 and 800 near the loss cone, and become 5, 5.5, 6.5 and 8 at pitch angle 90°, respectively. These results demonstrate that neglect of cross diffusion generally results in the overestimate of PSD, and the cross diffusion plays a more significant role in the resonant interaction between chorus waves and outer radiation belt electrons at larger L.