Experimental study of magnetospheric motions and the acceleration of energetic electrons during substorms

From a statistical study of 500- to 1000-kev electrons at synchronous orbit, it is concluded that near local midnight there exists a ‘fault line,’ west of which substorms are accompanied by geomagnetic inflation and east of which they are accompanied by collapse. Published studies have shown that the large, transient, substorm-associated fluxes of 50- to 150-kev electrons observed at synchronous orbit are produced near local midnight and subsequently drift longitudinally to other local times. A study of these lower-energy electron spikes and the concurrent geomagnetic data indicates that the electrons are produced during and within the geomagnetic collapse. Using measured magnetic data, it is concluded that the collapse is an inward convective surge of field lines with an average convective velocity estimated at 0.5 RE/min. Magnetotail plasma particles of initial energies up to 10-20 kev are convected inward and energized tenfold; protons drift longitudinally westward (producing the observed evening inflation, and perhaps establishing a partial ring current), and electrons drift eastward. The model proposed is similar in many respects to others already proposed. However, our model exhibits the asymmetric inflation and collapse behavior about the fault line shown by observations at synchronous orbit.