Understanding the dynamic evolution of the relativistic electron slot region including radial and pitch angle diffusion

It has been suggested that the equilibrium structure of the slot region, which separates the inner and outer radiation belts, forms as the result of a balance between inward radial diffusion and pitch angle scattering of relativistic electrons by interactions with three types of whistler mode waves: plasmaspheric hiss, lightening‐generated whistlers, and ground‐based Very Low Frequency (VLF) transmitters. In this study, using the time‐dependent 3D Versatile Electron Radiation Belt (VERB) code, we examine how effectively the slot can be formed by a combination of radial diffusion and pitch angle diffusion, together with Coulomb scattering, and compare the simulations with the CRRES MEA 1 MeV electron observations to examine the viability of the various scattering mechanisms. The results show that the overall time evolution of the observed two‐zone structure is in a good agreement with our model simulations, which suggests a balance between inward radial diffusion due to Ultra Low Frequency (ULF) electromagnetic fluctuations and pitch angle scattering due to plasmaspheric hiss and lightning‐generated whistlers. However, when inward radial diffusion due to the electrostatic fluctuations is included, agreement between the observed and simulated fluxes becomes weaker, suggesting that it is important to understand and quantify the radial diffusion rates in the slot region. Key Points This paper includes dynamic evolution of the relativistic electron slot region Plasmaspheric hiss is the dominant loss process in the slot region 3D VERB simulations are compared with CRRES MEA 1 MeV observations