The GEMSIS-Magnetosphere project: New models of the inner magnetosphere to investigate high-energy particle variation and the ERG science center

Geospace storms are the largest electromagnetic disturbance in near-Earth space and facilitate extensive particle acceleration in the inner magnetosphere, which causes development of the ring current and a drastic increase of relativistic electrons in the radiation belt. GEMSIS (Geospace Environment Modeling System for Integrated Studies) of STEL, Nagoya University, is the observation-based modeling project for understanding energy and mass transportation from the Sun to the Earth in the geospace environment. Aiming at understanding the dynamics of the inner magnetosphere during the geospace storms, the GEMSIS-Magnetosphere working team has addressed the development of new physics-based models for the global dynamics of the ring current (GEMSIS-RC model) and radiation belt (GEMSIS-RB model). The GEMSIS-RC model is a self-consistent and kinetic numerical simulation code solving the five-dimensional collisionless drift-kinetic equation for the ring-current ions in the inner-magnetosphere coupled with Maxwell equations. It is demonstrated that the propagation of magnetohydrodynamic waves can successfully be described by the present model. It is also found that the self-consistent coupling could affect the transport of energetic particles especially at low energies as well as the intensity and spatial distribution of field-aligned currents. Our approach is unique in the sense that it includes MHD wave modes as well as deformation of magnetic field configuration due to the ring current self-consistently. To understand the dynamics of the radiation belt, we have developed the GEMSIS-RB model that calculates relativistic charged particle trajectories in the magnetosphere. By applying time-varying magnetic field data calculated from the Tsyganenko model and using observed solar wind data and the Dst index, we first examined the drift loss of relativistic electrons by magnetopause shadowing (MPS). Initial results show a split in the outer radiation belt after the enhancement of the solar wind dynamic pressure. Isolated electrons outside of the split have a narrow pitch angle distribution around 90° and are confined to a narrow range of the L shell. The existence of the isolated electrons depends on the large geomagnetic tilt angle. It indicates that the split can be seen during summer and winter after MPS occurs. We suggest that this split in the outer radiation belt during summer and winter is evidence that MPS actually causes the loss of the outer radiation belt. Another important task of the GEMSIS project is contribution to the ERG science center that facilitates the close collaboration between the satellite, ground-based observation, and theory/simulation/modeling for geospace studies by providing integrated data analysis tools and combined database. In this presentation, we report on some of recent studies and activities from the GEMSIS-Magnetosphere project with an emphasis on the models of the ring current and radiation belt.