Radial Diffusion as a Potential Source and Loss Mechanism of Relativistic Electrons in the Outer Radiation Belt

Abstract

Abstract : The loss mechanisms responsible for the sudden depletions of the outer electron radiation belt are examined based on observations and radial diffusion modeling. SAMPEX data for Oct-Dec 2003, indicates that depletions are correlated with increases in geomagnetic activity and are also correlated with sudden increases in the solar wind dynamic pressure. Multi-channel HEO observations show that depletions at higher L are seen at energies as low as a few hundred keV. For the same events, high-energy proton channels also show decrease in fluxes at higher L-values. These observations are consistent with outward radial diffusion driven by the loss to magnetopause at L>4. We further examine the viability of the outward radial diffusion loss by comparing CRRES observations with a radial diffusion model simulation. Model-data comparison shows that flux variation near geosynchronous orbit can be effectively propagated by the outward radial diffusion to L=4 and can account for the main phase storm depletions.