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 By component, the simulated hemispheric Alfvénic power does not fit to the same linear relation. During steady IMF By 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 Bz 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.