Energetic and relativistic electrons near the polar magnetopause

More than 2 years of Geos 2 observations in the high-latitude outer magnetosphere and magnetosheath have confirmed the presence of a layer of energetic and relativistic electrons near the polar tail magnetopause. This layer, appearing as 'electron spike' on almost every magnetopause crossing, contains electrons over a wide range of energies up to relativistic energies of >2MeV. Their differential energy spectrum, if fitted by a power law, an average spectral index between 3 and 4.5. The spikes are typically 1--2R/sub E/ wide extending more into the mangetosheath than into magnetosphere. The electron intensity in the magnetopause layer decreases with distance along the tail, away from the polar cusp, and increase with K/sub P/ values. It tends to be higher when the magnetosheath field is parallel or antiparallel to the tail magnetic field. In many cases the magnetopause spikes in the magnetosheath which often follow closely the fluctuations of the magnetosheath field direction and/or intensity. A map of the average electron distribution in the polar magnetosphere and magnetosheath is presented