Dependence of the High-Latitude Lower Thermospheric Momentum Forcing on the Interplanetary Magnetic Field

At high latitudes the thermospheric winds are strongly influenced by energy and momentum sources associated with magnetosphere-ionosphere coupling, such as the magnetospheric convective electric field and the precipitation of energetic electrons and ions into the auroral regions. The wind patterns in the high-latitude lower thermosphere depend on the direction of the IMF, indicating that the forcing also varies with respect to the direction of the IMF. In this study, to understand the physical processes that control the high-latitude lower thermospheric dynamics (below 170 km) with respect to the direction of the IMF, we quantify the forces responsible for maintaining the wind system in the southern hemisphere as a function of the IMF orientation. We analyze steady-state forcing for different IMF directions, for summer conditions, based on simulations with the National Center for Atmospheric Research Thermosphere-Ionosphere Electrodynamics General Circulation Model (NCAR TIE-GCM).