Wave-particle interactions in the Van Allen radiation belts with implications for space weather science

Danny Summers

RISH, Kyoto University, Uji, Kyoto 611-0011, Japan
On leave from
Memorial University of Newfoundland, St. John's, Canada

The Earth's Van Allen radiation belts play an important role in space weather science. During magnetic storms, fluxes of relativistic (>1 MeV) electrons in the outer radiation belt (3<L<7) can increase by several orders of magnitude over pre-storm values. These relativistic electrons have been called "killer electrons" because they can disrupt or even shut down instruments in orbiting spacecraft. Relativistic electrons in the outer zone are also precipitated into the Earth's atmosphere, and can influence the chemical and electrical properties of the stratosphere and mesosphere. Wave-particle interactions largely control the dynamics of radiation belt electrons. Outer-zone electrons can undergo gyroresonant interaction with various magnetospheric wave modes including VLF whistler-mode chorus outside the plasmasphere, and both ELF whistler-mode hiss and electromagnetic ion cyclotron (EMIC) waves inside the plasmasphere. Quasi-linear theory is used to calculate timescales for electron momentum diffusion and pitch-angle diffusion. We show that momentum diffusion due to VLF chorus can generate relativistic (MeV) electrons in less than a day in the outer radiation belt. We further show that VLF chorus, plasmaspheric ELF hiss, and EMIC waves can each cause significant scattering loss of MeV electrons from the outer zone.