Particle boundary structures at the magnetopause and the plasma sheet

There are three classes of particle events in the vicinity of the magnetopause: a layer of particles right at the magnetopause which we identify with the boundary layer particles; spikes of particles just ahead of the magnetopause; and, sometimes, magnetosheath-like ions appearing inside the magnetosphere, the inclusion events. The energy spectra of these three classes of events are very similar, indicating a common particle source. The presence of a particle layer at the outer boundary of the plasma sheet is shown. This layer has typical dimensions of a few thousand km at 20 Earth radii. A typical velocity is a few tens of km/sec. These velocities and dimensions projected to ionospheric heights resemble those of visual auroras and suggest that aurorally associated particle phenomena are being detected.