Simultaneous observations of precipitating radiation belt electrons and ring current ions associated with the plasmaspheric plume

摘要

The wave-particle interactions and associated precipitation of energetic ions/electrons play an important role in the coupling between the inner magnetosphere and the ionosphere. In this paper, we present characteristics of precipitating ring current (RC) ions/electrons and precipitating radiation belt electrons associated with wave-particle interactions in the plasmaspheric plume in the main phase of a geomagnetic storm during 8-9 May 2001. With observations of the NOAA 16 satellite, within the anisotropic zone, the peak of precipitating RC electron flux was equatorward to that of precipitating RC proton flux in a plasmaspheric plume recognized by the IMAGE and LANL-91/94 satellites. An enhancement of precipitating flux for >3 MeV electrons was simultaneously observed by NOAA 16 with the increase of precipitating RC proton flux within the anisotropic zone. Theoretical calculations of pitch angle diffusion coefficients for RC protons and for radiation belt electrons caused by electromagnetic ion cyclotron (EMIC) waves demonstrated that precipitating flux enhancements of RC protons and >3 MeV radiation belt electrons are a result of EMIC wave-particle interactions in the plasmaspheric plume. Our result suggests that EMIC waves in the plasmaspheric plume can scatter not only RC ions but also radiation belt electrons into the loss cone, which cause the loss of the RC ions and radiation belt electrons.