Simultaneous Observations of EMIC-Induced Drifting Electron Holes (EDEHs) in the Earth's Radiation Belt by the Arase Satellite, Van Allen Probes, and THEMIS

We present an observation of rapid flux depressions in relativistic electrons, which is referred to as EMIC-induced drifting electron holes (EDEHs). The Arase, Van Allen Probes, and THEMIS detected simultaneously electron flux fluctuations. The time variation of flux shows depressions of 1-min scale with energy dispersion, which appear only in the relativistic energy range and small pitch angles. These characteristics of the flux depression indicate that electromagnetic ion cyclotron waves caused pitch angle scattering on a short time scale in a longitudinally limited region. The Arase satellite detected the local depression of the phase space density of 1,000 MeV/G electron, indicating that EMIC waves cause the true loss of electrons. Tracing the energy dispersion profile of EDEHs, we show that EDEHs are formed at localized region in the dusk side. Multisatellite observations demonstrate that a series of EDEHs eventually cause a substantial depression of the radiation belt on 1-hr time scale.

Automated summary

The study observed rapid flux depressions in relativistic electrons, known as EMIC-induced drifting electron holes (EDEHs), caused by electromagnetic ion cyclotron waves on a short timescale in a limited region. These flux depressions occur in the relativistic energy range and small pitch angles, potentially leading to significant depression of the radiation belt.