The Global Magnetosphere Under Storm-Time Conditions

Dr. George Siscoe
Center for Space Physics
Boston University

MHD simulations give about the same dependence of transpolar potential on solar wind electric field (IEF) as the Hill model of transpolar potential, including saturation under storm-time conditions. MHD simulations reveal further that transpolar potential saturation most likely results from solar wind ram pressure limiting the amount to which region 1 currents can grow rather than from a limit on total reconnection potential. Total reconnection potential is unrestricted by the ram-pressure limitation and continues to grow approximately linearly with IEF. The resulting difference between transpolar potential and reconnection potential that arises when the magnetosphere enters the saturation (storm-time) domain implies parallel potential drops, which, during magnetic storms, can reach tens to hundreds of kilovolts. The resulting parallel electric fields could pull ions in large numbers out of the ionosphere, energize them to ring-current energies. The suggestion therefore presents itself that transpolar potential saturation and magnetic storms are aspects of one phenomena: region 1 current saturation by solar wind ram pressure.