ARS Advances in Radio Science ARS Adv. Radio Sci. 1684-9973 Copernicus Publications Göttingen, Germany 10.5194/ars-9-343-2011 Some anomalies of mesosphere/lower thermosphere parameters during the recent solar minimum Jacobi Ch. 1 Hoffmann P. 1 Placke M. 2 Stober G. 2 Institute for Meteorology, University of Leipzig, Stephanstr. 3, 04103 Leipzig, Germany Leibniz Institute of Atmospheric Physics at the Rostock University, Schlossstraße 6, 18225 Kühlungsborn, Germany 01 08 2011 9 343 348 Copyright: © 2011 Ch. Jacobi et al. 2011 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://ars.copernicus.org/articles/9/343/2011/ars-9-343-2011.html The full text article is available as a PDF file from https://ars.copernicus.org/articles/9/343/2011/ars-9-343-2011.pdf

The recent solar minimum has been characterized by an anomalous strong decrease of thermospheric density since 2005. Here we analyze anomalies of mesosphere/lower thermosphere parameters possibly connected with this effect. In particular, nighttime mean LF reflection heights measured at Collm, Germany, show a very strong decrease after 2005, indicating a density decrease. This decrease is also visible in mean meteor heights measured with VHF meteor radar at Collm. This density decrease is accompanied by an increase of gravity wave (GW) amplitudes in the upper mesosphere and a decrease in the lower thermosphere. On the decadal scale, GWs are negatively correlated with the background zonal wind, but this correlation is modulated in the course of the solar cycle, indicating the combined effect of GW filtering and density decrease.

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