A global study of meridional winds in the thermosphere

We present neutral meridional winds derived from existing ground-based measurements of the height of the F2-layer maximum electron density (h_max). The method of calculation uses an ionospheric model to determine the relationship between h_max and the neutral wind along a magnetic meridian. The meridional wind is derived from a comparison of the modeled layer height with the measured height. This method is used in the global mapping of thermospheric winds using radar and ionosonde measurements from the Global Thermospheric Mapping Study at the summer and winter solstices. The diurnal behavior of the meridional wind is calculated for the two seasons from Millstone Hill radar measurements and from several ionosonde stations. The major features of the winds calculated from Millstone Hill radar data are a 200 m/s southward wind between 0200 and 0400 hours local time at the summer solstice and a northward daytime wind in winter. A sampling of winds derived from ionosonde data shows the diurnal pattern to vary with geographic latitude and longitude. Nighttime equatorward winds are found to be larger in Europe than at other locations of similar latitude.