Indications of long-term changes in the lower thermosphere...

INTERNATIONAL JOURNAL OF GEOMAGNETISM AND AERONOMY VOL. 5, GI3010, doi:10.1029/2004GI000085, 2005

Indications of long-term changes in the lower thermosphere prevailing zonal wind regime

E. S. Kazimirovsky , V. D. Kokourov , and G. V. Vergasova
Institute of Solar-Terrestrial Physics, Irkutsk, Russia

Abstract

[1] To take a new approach to the lower thermosphere (80-100 km) long-term behavior, the variations of the dates of the equinoctial rearrangements of the zonal wind circulation were considered. We have evaluated the duration of unstable equinoctial rearrangements periods and duration of rather stable summer and winter circulation periods as well. The identical multiyear radio measurements of the horizontal winds in the lower thermosphere/ionosphere at two midlatitude (52^oN) observatories (Irkutsk (Badary Observatory), East Siberia, and Collm, central Europe) during 1981-1996 were used. It is shown that there are significant nonzonality and regional differences in the character of the circulation rearrangements. The duration of the winter circulation in East Siberia is systematically longer than in central Europe. However, the tendency to a decrease of the summer circulation duration for the years under consideration is observed for both regions.

Received 26 October 2004; revised 18 January 2005; accepted 6 May 2005; published 30 June 2005.

Keywords: Lower thermosphere/ionosphere; Prevailing wind; Long-term changes.

Index Terms: 0341 Atmospheric Composition and Structure: Middle atmosphere: constituent transport and chemistry; 2437 Ionosphere: Ionospheric dynamics; 2427 Ionosphere: Ionosphere/atmosphere interactions.

Citation: Kazimirovsky, E. S., V. D. Kokourov, and G. V. Vergasova (2005), Indications of long-term changes in the lower thermosphere prevailing zonal wind regime, Int. J. Geomagn. Aeron., 5, GI3010, doi:10.1029/2004GI000085.