Correlated observations and simulations on the buildup of radiation belt electron fluxes driven by substorm injections and chorus waves

Abstract

We report the multi-satellite (LANL, GOES-10 and Cluster) observation data of electron flux evolutions and chorus wave excitation in the radiation belt during the geomagnetic storm and substorm from 10 to 14 January, 2002. The seed (50–225 keV) electron flux increased 50 times in five hours during the storm main phase, and the relativistic (>0.6 MeV) electron flux increased about 60 times at night side during the recovery phase. In the meanwhile, the Cluster satellites detected intense chorus waves (the wave power up to ∼10−3 nT2 Hz−1) at MLT≈3 when passing through the outer radiation belt. Using a Gaussian fit to the observed chorus spectra, we calculate the drift-averaged diffusion coefficients and then solve a 2-D Fokker-Planck diffusion equation. We simulate the energetic electron flux evolutions driven by chorus waves in two cases: with and without seed electron injections. We show that the energetic electron flux increases 79 times in three days with injection, comparable to the observation. However, the flux increases only 3 times in three days without injection, far below the observation. The current results suggest that the injected seed electrons and chorus waves play important roles in the buildup of the radiation belt electrons.