ON THE PRECIPITATION OF RELATIVISTIC ELECTRONS FROM THE OUTER BELT

Data from the DMSP satellite due to relativistic electrons (E > 1 MeV) in the region of the outer belt are investigated. The data are interpreted by means of a model in which a partially filled drift loss cone plays a prominent role. The model of SHELDON et al. (1987, Adv. Space Res. 7, 49), which described the loss of outer belt electrons at L = 4 through gradient and curvature drift in the drift loss cone, has been modified to also include the effect of wave-particle interactions. Predictions of the model are found to be in good agreement with the DMSP data. This result indicates that electron drift in the drift loss cone, known to dominate electron precipitation phenomena at lower latitudes, is important at outer belt latitudes, as well. This effect, and the degree of partial filling of the drift loss cone which is consistent with the DMPS data, indicates that slow pitch angle diffusion dominates the morphology of outer belt electrons, a point which appears to be controversial. Finally, it is concluded that half of the electron precipitation from the outer belt is caused by wave-particle interactions, and the other half by auroral activity and electron drift per se in the drift loss cone.