High-Latitude Observations of a Localized Wind Wall and Its Coupling to the Lower Thermosphere

Reversals in the thermospheric zonal winds at altitudes of 140 to 250\ km from eastward to westward have been found at southern geographic latitudes between 60\textdegree and 70\textdegree. These are confined to a narrow region between 100\textdegree and 200\textdegree in longitude with zonal velocities regularly of -400\ m/s, sometimes reaching -600\ m/s, so sharply defined that the authors describe it as a \textquotedblleftwind wall.\textquotedblright The observations were made by the Wind Imaging Interferometer on National Aeronautics and Space Administration\textquoterights Upper Atmosphere Research Satellite, and they occur as the field of view crosses the high polar cap wind field. The wind reversals at the wall boundaries create a convergence on the west side of the wall and a divergence on the east side that potentially generate vertical flows, consistent with observed perturbations in the O(1S) emission rate. They are present about one half of the time in local summer and autumn.