This session is dedicated to the electromagnetic environment and the physical processes responsible for variations in the radiation belts in the near-Earth region (L<4.5), particularly those associated with precipitation into the atmosphere at high latitude. In the inner belt, most processes have long timescales and the radiation is persistent. Complexity arises from the dependence of the waves/processes on longitude and local-time and from the geomagnetic activities involving solar drivers and MLT variations. Conversely, in the slot region and the outer belt, loss associated with wave-particle interactions and causing atmospheric precipitation can be much faster and suffer from larger variations. Fast particle injections also occur, competing with and obscuring the slower processes. This session solicits observational studies from satellite missions and/or ground measurements, and numerical studies of particles (electrons/ions) dynamics (particle loss, injections...), electromagnetic waves (existence, properties...), wave-particle interactions, large-scale electric/magnetic fields, the plasmasphere, plasmaspheric coupling, atmospheric precipitation, and ionosphere heating.