Abstract
The ratio of the values of the F 2, layer critical frequencies 2 h after the sunset and at 1400 LT has been considered. It is assumed that this ratio is a good indicator of the intensity of wind processes in the thermosphere. For 18 ionospheric stations, the dependences of this ratio on the F wl, solar activity index have been constructed for the period before 1980. It has been found that the standard deviation (S), from this dependence has been increased after 1980 at all stations. An increase in S, is interpreted as an indication of the existence of long-term trends in th e wind regime after approximately 1980.
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Original Russian Text © A.D. Danilov, L.B. Vanina-Dart, 2010, published in Geomagnetizm i Aeronomiya, 2010, Vol. 50, No. 1, pp. 61–66.
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Danilov, A.D., Vanina-Dart, L.B. Comparison of foF2 values in the daytime and after sunset. Geomagn. Aeron. 50, 58–63 (2010). https://doi.org/10.1134/S001679321001007X
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DOI: https://doi.org/10.1134/S001679321001007X