First Observations of Antarctic Mesospheric Tidal Wind Responses to Recurrent Geomagnetic Activity

We report an analysis of the response of tides in neutral atmospheric mesospheric winds to recurrent geomagnetic activity in 2005 over Antarctica. The mesospheric winds were observed by the Davis meteor and medium frequency radars (68.5°S, 77.9°E; magnetic latitude, 74.6°S). The zonal component of the daily prevailing winds showed a westward increase as the geomagnetic activity increased, while the meridional prevailing winds did not show a clear response. The semidiurnal tides responded greatly to geomagnetic activity, with significant increases in amplitude. The zonal and meridional semidiurnal tides both showed a clear upward propagating phase but responded differently to geomagnetic activity. The amplitude of the meridional component of the diurnal tides increased significantly, while the zonal diurnal tidal amplitude showed no apparent change. These results indicate that geomagnetic activity can significantly influence mesospheric dynamics. Plain Language Summary The mesosphere is strongly influenced by the vertical upward propagation of atmospheric tides through the transport of energy and momentum from the lower atmosphere. In addition, a few studies have reported the mesospheric tidal response to geomagnetic storms, but the results have been contradictory. In this study, we first report the clear response of tides in neutral atmospheric mesospheric winds to recurrent geomagnetic activity related to the high‐speed solar wind stream. The zonal component of the daily prevailing wind showed a westward increase as the geomagnetic activity increases. The semidiurnal tides responded greatly to geomagnetic activity, with significant increases in amplitude. The zonal and meridional semidiurnal tides both showed a clear upward propagating phase but responded differently to geomagnetic activity. These results demonstrate a direct coupling between Sun's corona (upper atmosphere) and the Earth's mesosphere. Key Points The zonal component of the daily prevailing wind showed a westward increase as the geomagnetic activity increases The amplitudes of semidiurnal tides increased significantly during geomagnetic activity The zonal and meridional components of the diurnal tides responded differently to geomagnetic activity