Quantifying storm-time variation of Van Allen belt relativistic electrons associated with radial diffusion

Abstract:

Local acceleration and radial diffusion both play critical role in the outer radiation belt dynamics. Previous works have demonstrated the distinct figure of local acceleration that the electron seed population from plasma sheet transported into the heart of outer radiation belt by inward diffusion or enhanced convection, is accelerated by subsequent local acceleration to produce build-ups of relativistic electron fluxes. In this study, We report a possibly different process during the 2 October 2013 storm by surveying the collected data of Van Allen Probes and THEMIS satellites. THEMIS observed pronounced chorus waves and highly energetic electron enhancement at higher L-shell and Van Allen Probes observed relativistic electron flux enhancement and enhanced radial diffusion without distinct chorus. We calculate the bounce-averaged momentum diffusion coefficient to verify the efficient acceleration effect of the observed chorus waves. We also calculate the diffusion coefficients and perform a one-dimensional simulation for the radial diffusion which shows remarkable agreements in PSD temporal evolution. The current results provide a new approach of the violent electron variations in the inner magnetosphere that chorus waves produce local acceleration at higher L-shell providing external source, then radial diffusion transport the relativistic electrons into the heart of outer radiation belt within the time scale of a very few hours.