Loss effects for energetic protons associated with a magnetic storm in the inner magnetosphere

Development of the ring current is one of major phenomena during a magnetic storm in the Earth\u27s magnetosphere. Ring current protons collide with other particles (e.g., geocoronal hydrogen and plasmaspheric electrons) and lose their energies within a few days. The primary loss processes for ring current protons are considered as; (i) charge exchange with the geocoronal neutral hydrogen, and (ii) Coulomb collision with the plasmaspheric thermal electrons. In order to estimate the loss rate caused by both loss processes numerically, it is essential to trace each particle along their trajectories because the drift paths basically depend on energy, pitch angle, initial position of charged particles and the magnetospheric electric and magnetic fields. For this purpose, we have developed a particle simulation code including the charge exchange and the Coulomb collision as the major loss processes with a time-dependent magnetospheric electric field. A new plasmaspheric density model is also developed to evaluate the Coulomb collision between the ring current protons and the plasmaspheric thermal electrons. This model is a two dimensional and time-development on plasmaspheric number density, derived from a continuity equation along a magnetic flux tube connecting with the conjugate ionospheres in both hemispheres. Using this model, we obtained the electron density distribution in the plasmasphere which was fairly consistent with the one obtained by EXOS-B satellite observation. In this paper, we demonstrate the trajectory of 100 eV (lower energy) and 100keV (higher energy) protons associated with a magnetic storm. Their energies are lost effectively by Coulomb collisions more than charge exchange loss process, and hence, thermal electron distribution in the inner plasmasphere gives an important effect for lower and/or higher energy protons