Interplanetary Control of High-Latitude Thermospheric Winds: Results From HIWIND and Model Simulations

Based on the observations from the balloon-borne instrument High-altitude Interferometer WIND experiment (HIWIND) and the simulations from the Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM), the Grid Agnostic MHD Environment for Research Applications (GAMERA)-TIEGCM (GT), and the GAMERA-TIEGCM-RCM (GTR), we investigate the variations of summer high-latitude thermospheric winds and their physical mechanisms from 25 to 30 June, 2018. HIWIND observations show that the meridional winds were the largest at midnight and exhibited strong day-to-day variations during the 6-day period, which were generally reproduced by those three models. The day-to-day variations of winds were mainly associated with the interplanetary magnetic field (IMF) (Formula presented.) perturbations, while the magnetic latitude variations also contributed to the large day-to-day variations of the winds seen in the observations. Meanwhile, the zonal winds were mostly westward during the daytime, and the wind speed became large, especially in the afternoon, which is related to the westward ion drift velocity. The observed meridional winds tend to turn equatorward during the daytime on some days, while the simulated winds blow mostly poleward except for simulations by the GTR model on 26 June. The GTR model revealed that the equatorward meridional winds on 26 June were associated with strong and negative IMF (Formula presented.) conditions, which tilts the convection pattern to the prenoon sector. The simulations also revealed that the ring current could contribute to affecting the neutral wind variations, especially under geomagnetically active conditions.