Dynamic Evolution of Outer Radiation Belt Electrons due to Whistler-Mode Chorus

Abstract

Following our preceding work, we perform a further study on dynamic evolution of energetic electrons in the outer radiation belt L = 4.5 due to a band of whistler-mode chorus frequency distributed over a standard Gaussian spectrum. We solve the 2D bounce-averaged Fokker–Planck equation by allowing incorporation of cross diffusion rates. Numerical results show that whistler-mode chorus can be effective in acceleration of electrons at large pitch angles, and enhance the phase space density for energies of about 1 MeV by a factor of 102 or above in about one day, consistent with observation of significant enhancement in flux of energetic electrons during the recovery phase of a geomagnetic storm. Moreover, neglecting cross diffusion often leads to overestimates of the phase space density evolution at large pitch angle by a factor of 5–10 after one day, with larger errors at smaller pitch angle, suggesting that cross diffusion also plays an important role in wave—particle interaction.