Ionospheric control of the magnetospheric configuration: Thermospheric neutral winds

Abstract

In this study we present the first results from the University of Michigan's coupled magnetosphere-ionosphere-thermosphere general circulation model. This code is a combination of the Michigan MHD model with the NCAR thermosphere-ionosphere-electrodynamics general circulation model (TIEGCM). The MHD code provides specification of the high-latitude ionospheric electric potential and the particle precipitation pattern, while the TIEGCM provides the divergence of the height-integrated neutral wind multiplied by the conductance. This can be easily incorporated into the electric potential solver in the MHD code. We show in this study that the neutral winds cause an approximately 6% increase in the cross polar cap potential when the IMF is strongly southward. This causes the magnetospheric field aligned currents to decrease by a small amount. In the magnetosphere, the flow speeds are increased by only a small amount while the IMF is strongly southward, but when it turns northward the differences become 10-20%. When the IMF is northward, the pressure on the dayside magnetosphere is reduced while the pressure on the nightside is increased by ∼ 10% of the total pressure. Copyright 2003 by the American Geophysical Union.