RELATIVISTIC ELECTRON ACCELERATION AND DECAY TIME SCALES IN THE INNERAND OUTER RADIATION BELTS - SAMPEX

High-energy electrons have been measured systematically in a low-altit ude (520 x 675 km), nearly polar (inclination = 82-degrees) orbit by s ensitive instruments onboard the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX). Count rate channels with electron energy t hresholds ranging from 0.4 MeV to 3.5 MeV in three different instrumen ts have been used to examine relativistic electron variations as a fun ction of L-shell parameter and time. A long run of essentially continu ous data (July 1992 - July 1993) shows substantial acceleration of ene rgetic electrons throughout much of the magnetosphere on rapid time sc ales. This acceleration appears to be due to solar wind velocity enhan cements and is surprisingly large in that the radiation belt ''slot'' region often is filled temporarily and electron fluxes are strongly en hanced even at very low L-values (L approximately 2). A superposed epo ch analysis shows that electron fluxes rise rapidly for 2.5 less than or similar L less than or similar 5. These increases occur on a time s cale of order 1-2 days and are most abrupt for L-values near 3. The te mporal decay rate of the fluxes is dependent on energy and L-value and may be described by J = Ke-t/to with t(O) almost-equal-to 5-10 days. Thus, these results suggest that the Earth's magnetosphere is a cosmic electron accelerator of substantial strength and efficiency.