Relativistic electron precipitation during magnetic storm main phase

Relativistic electrons can have cyclotron resonances with electromagnetic ion‐cyclotron waves. The resonant energy is generally well above 1 Mev throughout the magnetosphere, but it can fall to near 1 Mev just within the plasmapause. This also corresponds to the region where ring current (10–50 kev) protons are expected to be strongly unstable. The resulting ion‐cyclotron wave amplitude necessary to precipitate ring current protons leads to electron lifetimes near the strong diffusion limit. Thus, >1‐Mev electrons whose drift orbits intersect the stormtime plasmapause should rapidly be precipitated in the region 3< L <5 during the initial phase of a magnetic storm.