Effect of seed electron injection on chorus-driven acceleration of radiation belt electrons

Abstract

Using the hybrid finite difference method, we solve the Fokker-Planck equation to study the effect of seed electron injection on acceleration of radiation belt electrons driven by chorus waves. Numerical results show that in the absence of injection chorus waves can accelerate electrons at large pitch angles (alpha(e)>60 degrees), producing enhancements in the phase space density (PSD) of (1-2 MeV) electrons by a factor of 100-1000 within 1-2 days. In the presence of injection, chorus waves yield increase in PSD of electrons by accelerating the injected seed electrons. Meanwhile, the PSD evolution increases as the pitch angle increases but decreases as electron energy increases. Moreover, the PSD evolution can extend to higher energies with a time scale of 1-2 days for 1-2 MeV energies. When the injection increases by a factor of 10 higher than the initial value and remains for about two days, maximum values of PSD for 1 or 2 MeV increase to 6 or 3 times respectively higher than those without injection in two days. The current results suggest that the injected seed electrons play an important role in the evolution of the radiation belt electrons.