Electromagnetic hiss and relativistic electron losses in the inner zone

Abstract

It is shown that ELF hiss is present in the inner radiation zone (L less than 2) during both storms and substorms. This presence is ascribed to propagation of waves into this region from a distributed source located at high altitude near the equatorial plasmapause. Two major effects allow hiss to reach the inner zone during storms and substorms: (1) the observed tendency for plasmaspheric hiss to be greatly intensified during the recovery phase as the outward-moving plasmapause encounters the electrons that have been freshly injected into the magnetosphere; (2) the displacement of the plasmapause, and the presumed source region, to low altitudes during high levels of magnetic activity.