Ring current development in MHD simulations

A signature feature of magnetic storms is the development of a ring current. Recent ideas on ring current formation suggest that during the main phase of storms the ring current is primarily asymmetric, becoming symmetric only during the recovery phase. In this paper, we examine ring current formation during a magnetic storm using global magnetohydrodynamic simulations of the interaction between the solar wind and the magnetosphere. The magnetohydrodynamic simulation uses solar wind data as a boundary condition, allowing the modeling of actual events. The event modeled here is the January 1997 storm. Although the code does not develop a true ring current, the simulated electromagnetic potentials predict the trajectory of drifting energetic particles in a non-self-consistent manner. Comparing drift paths of ring current-energy particles during the main phase and the recovery phase, we find that the MHD simulation predicts an asymmetric main phase ring current that evolves into a symmetric ring current during the recovery phase.