Modeling energetic electron penetration into the slot region and inner radiation belt

The inner radiation belt is thought to be quite stable, and only the most intense geomagnetic storms can cause energetic electron variations in the slot region and inner belt. In this paper, using energetic electron flux data from Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite, we show that 100s keV electron flux enhancements in the slot region and inner belt are seen quite often and can occur even during moderate geomagnetic storms. In addition, by transforming the energetic electron flux data into the phase space density (PSD), we model the inward radial transport of two different electron populations, =30 MeV/G (K=0) and =15MeV/G (K=0), using a 1-D radial diffusion model in which the radial diffusion coefficient is directly associated with solar wind parameters and L shell. The model results reproduce the PSD data well in the slot region and inner belt, indicating that the flux enhancement in the inner belt and slot region can be well explained by inward radial transport. The radial diffusion coefficients used in our model are much larger than the widely used Kp-dependent electromagnetic radial diffusion coefficient but are smaller than the Kp-dependent electrostatic radial diffusion coefficient (Brautigam and Albert, 2000), suggesting that the Kp-dependent diffusion coefficient cannot be simply extended to lower L region to account for the observed enhancements of energetic electrons in the slot region and inner belt.