On the origin of electron precipitation in the auroral zone related to the onset of magnetospheric substorms

Observations of electron precipitation via X-ray measurements with balloon-borne instruments and electron measurements onboard the geostationary satellite GEOS-2 are used to analyse the relationship between electron precipitation and magnetospheric processes at the onset of a magnetospheric substorm. The observations are interpreted in terms of electron scattering and different acceleration processes at the outer boundary of the plasma sheet and simultaneous movements of its inner boundary.