Some anomalies of mesosphere/lower thermosphere parameters during the recent solar minimum

[摘要] The recent solar minimum has been characterized by an anomalous strongdecrease of thermospheric density since 2005. Here we analyze anomalies ofmesosphere/lower thermosphere parameters possibly connected with thiseffect. In particular, nighttime mean LF reflection heights measured atCollm, Germany, show a very strong decrease after 2005, indicating a densitydecrease. This decrease is also visible in mean meteor heights measured withVHF meteor radar at Collm. This density decrease is accompanied by anincrease of gravity wave (GW) amplitudes in the upper mesosphere and adecrease in the lower thermosphere. On the decadal scale, GWs are negativelycorrelated with the background zonal wind, but this correlation is modulatedin the course of the solar cycle, indicating the combined effect of GWfiltering and density decrease.

[学科分类] 电子、光学、磁材料