Precipitation of Radiation Belt Electrons by Electromagnetic Ion Cyclotron Rising-Tone Emissions

Electromagnetic Ion Cyclotron (EMIC) rising-tone emissions are excited by nonlinear interaction with energetic protons both inside and outside the plasmasphere. The coherent EMIC emissions interact with relativistic electrons and scatter them to lower pitch angles efficiently by nonlinear wave trapping described by the pendulum equation and the anomalous trapping at low pitch angles, resulting in significant precipitation of radiation belt electrons as well as energetic protons. In the nonlinear wave trapping, the rising-tone frequencies of the emissions and the gradient of the background magnetic field play essential roles in changing pitch angles. We present recent development of nonlinear theory, simulations, and observations of coherent EMIC rising-tone emissions and associated rapid precipitation of the outer radiation belt electrons.