Radiation belt electron dynamics driven by adiabatic transport, radial diffusion, and wave-particle interactions

Abstract

The adiabatic transport process is introduced into our recently developed three-dimensional physics-based electron radiation belt model (STEERB, Storm-Time Evolution of Electron Radiation Belt) via adopting a time-varying Hilmer-Voigt geomagnetic field. The current STEERB model contains more complete physical processes: adiabatic transport, radial diffusion, and various in situ wave-particle interactions. In particular, the influence of adiabatic transport on storm time radiation belt electron dynamics is investigated by some idealized simulations. It is found that the adiabatic transport alone (without plume hiss and electromagnetic ion cyclotron (EMIC) waves) is unable to reproduce the observed main phase loss of energetic outer radiation belt electron fluxes in the presence of a strong chorus-driven acceleration process. However, these adiabatic and nonadiabatic processes for radiation belt electron dynamics are coupled to each other. The adiabatic transport, together with radial diffusion and cyclotron resonant interactions with chorus, plume hiss, and EMIC waves, contributes significantly to the main phase loss and the recovery phase enhancement of energetic electron fluxes. In the absence of adiabatic transport, the energetic outer radiation belt electron fluxes are found to be overestimated by a factor of 5-30 over all the pitch angles during the main phase and to be underestimated by a factor of 2-5 at larger pitch angles (alpha(e) > 50 degrees) during the recovery phase. These numerical results suggest that the adiabatic transport in a time-varying geomagnetic field model should be incorporated into the future radiation belt models for space weather application.