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Author: Jacobi, C. × Author: Stober, G. × End date: 2019 × Start date: 2010 × Publisher: Göttingen : Copernicus × WGL Institute: IAP ×

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Now showing 1 - 2 of 2
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    Some anomalies of mesosphere/lower thermosphere parameters during the recent solar minimum
    (Göttingen : Copernicus, 2011) Jacobi, C.; Hoffmann, P.; Placke, M.; Stober, G.
    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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    Distortion of meteor count rates due to cosmic radio noise and atmospheric particularities
    (Göttingen : Copernicus, 2010) Stober, G.; Jacobi, C.; Keuer, D.
    The determination of the meteoroid flux is still a scientifically challenging task. This paper focusses on the impact of extraterrestrial noise sources as well as atmospheric phenomena on the observation of specular meteor echoes. The effect of cosmic radio noise on the meteor detection process is estimated by computing the relative difference between radio loud and radio quiet areas and comparing the monthly averaged meteor flux for fixed signal-to-noise ratios or fixed electron line density measurements. Related to the cosmic radio noise is the influence of D-layer absorption or interference with sporadic E-layers, which can lead to apparent day-to-day variation of the meteor flux of 15-20%. © 2010 Author(s).