Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm

The response of outer radiation belt relativistic electrons to the October 9, 1990, magnetic storm is analyzed in detail using a radial diffusion mode l and data from the Combined Release and Radiation Effects Satellite (CRRES ) and the Los Alamos National Laboratory (LANL) geosynchronous satellite 19 89-046. Electron measurements are expressed in terms of phase space density as a function of the three adiabatic invariants determined from CRRES magn etic field data and the Tsyganenko 1989 Kp-dependent magnetic field model. The radial diffusion model is implemented with a time-dependent radial diff usion coefficient parameterized by Kp, and a time-dependent outer boundary condition scaled by geosynchronous electron data, The results show that rad ial diffusion propagates outer boundary variations into the heart of the ou ter radiation belt, accounting for both significant decreases and increases in the <1 MeV electron flux throughout that region. It is further shown th at the gradual increase throughout the recovery phase of the >1 MeV electro ns is inconsistent with the radial diffusion model given the parameter regi me chosen for this study. Greatly enhanced whistler chorus waves observed b y CRRES throughout the recovery phase suggest that a possible explanation f or the inconsistency may be electron acceleration via wave-particle interac tion.