Ionospheric winds in the F-region and their effects on the limiting periods of gravity waves

Spectrum analyses of ionospheric electron density and content fluctuations show periods with a lower limit near 5 min. Interpretation of this cut off in terms of gravity waves in a windless atmosphere leads to unacceptably low thermospheric temperatures near 180°K. It is concluded that neutral winds reduce the apparent cut-off period in the ionosphere. The maximum horizontal wind speed obtained from cut-off data is about 100 m/sec.