First U.S.-China joint ground-based Fabry-Perot interferometer observations of longitudinal variations in the thermospheric winds

For the first time, three Fabry-Perot interferometers from the U.S. (Boulder, 40°N, 105°W, 49°N magnetic latitude (MLAT)) and China (Xinglong: 40°N,115°E, 34°N, MLAT; Kelan: 39°N, 112°E, 33°N MLAT) were used to examine the longitudinal variations in the thermospheric winds due to the geomagnetic latitude differences between the American and Asian sectors. During a case of quiet geomagnetic condition, the meridional winds were very similar at the U.S. and Chinese stations. The meridional winds at Boulder reached most equatorward winds after midnight, whereas in China, the largest equatorward winds were found near midnight. The Boulder zonal winds turned westward earlier in the morning hours and had larger diurnal variations because of its higher magnetic latitude. During the case of low geomagnetic activity (Kp~2), the meridional winds were still similar in the U.S. and in China. Boulder zonal winds had much larger diurnal variation compared to the quiet condition (Kp~1). Thermosphere-ionosphere-electrodynamics general circulation model simulations show a very good agreement with observation for the meridional winds. The simulated zonal winds exhibit noticeable differences with observations, but the general tendencies in longitudinal variations with a larger diurnal variation near the auroral oval are correct. Simulations showed that the ion drift is not directly responsible for the longitudinal variations in the winds. The pressure gradient had more direct effect on the longitudinal changes in the winds. The simulation results also showed larger diurnal variations at higher geomagnetic latitudes due to the auroral oval heating. Nonmigrating tides were not observed in the two cases in October 2012.