Solar wind control of auroral Alfvénic power generated in the magnetotail

The effects of solar wind driving conditions on the polar distribution of large-scale, nondispersive Alfvénic Poynting flux at low altitude during steady magnetosphere convections are studied using three-dimensional global simulations of the solar wind-magnetosphere-ionosphere interaction. Results from 18 test simulations driven by steady upstream solar wind (SW) and interplanetary magnetic field (IMF) conditions are used to investigate the relationship between SW/IMF driving and low-altitude signatures of large-scale Alfvénic Poynting flux. When the IMF is southward, the intensity of the Alfvénic Poynting flux increases, and the hemispheric integrated Alfvénic Poynting flux exhibits a linear relation with the SW electric field. When the IMF has a B_y component, the simulated hemispheric Alfvénic power does not fit to the same linear relation. During steady IMF B_y driving conditions, the low-altitude regions with enhanced Alfvénic Poynting flux are magnetically connected with magnetospheric dynamo regions on both open and closed field lines. The physical origin of low-altitude Alfvénic Poynting flux connecting to the closed field line region is similar with that during southward IMF B_z driving. However, the Alfvénic Poynting flux flowing from the open field line dynamo region may be related to the physical process on the magnetopause, and only shear-mode waves are generated.