Strong electron acceleration in the Earth's magnetosphere

Electron data are examined over long periods in the outer zone of electron trapping (L greater than or similar to 3). Energetic particle detectors at geostationary orbit and onboard the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite show evidence of strong electron acceleration in Earth's outer radiation belts. Data are studied according to L-value and are compared with concurrent solar.wind and geomagnetic conditions. Evidence is presented of a strong correlation between high-speed solar wind speeds and the occurrence of high energy electrons in the Earth's outer radiation belts. Thus, high-speed solar wind streams apparently drive the acceleration of electrons throughout the outer zone on time scales of days. The processes by which electrons are accelerated to high energies (E>1 MeV) are found to consist of two temporally distinct steps. The first involves prompt, relatively modest, acceleration of many electrons during magnetospheric substorms. The second step involves higher energy acceleration of a portion of the substorm electrons throughout the outer trapping region on a time scale of days. (C) 1998 COSAR. Published by Elsevier Science Ltd.