Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8139667 | Journal of Atmospheric and Solar-Terrestrial Physics | 2018 | 8 Pages |
Abstract
For the first time, long-term data sets of ground-based observations of noctilucent clouds (NLC) around the globe have been analyzed in order to investigate a response of NLC to solar UV irradiance variability on a day-to-day scale. NLC brightness has been considered versus variations of solar Lyman-alpha flux. We have found that day-to-day solar variability, whose effect is generally masked in the natural NLC variability, has a statistically significant effect when considering large statistics for more than ten years. Average increase in day-to-day solar Lyman-α flux results in average decrease in day-to-day NLC brightness that can be explained by robust physical mechanisms taking place in the summer mesosphere. Average time lags between variations of Lyman-α flux and NLC brightness are short (0-3 days), suggesting a dominant role of direct solar heating and of the dynamical mechanism compared to photodissociation of water vapor by solar Lyman-α flux. All found regularities are consistent between various ground-based NLC data sets collected at different locations around the globe and for various time intervals. Signatures of a 27-day periodicity seem to be present in the NLC brightness for individual summertime intervals; however, this oscillation cannot be unambiguously retrieved due to inevitable periods of tropospheric cloudiness.
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Authors
P. Dalin, N. Pertsev, V. Perminov, A. Dubietis, A. Zadorozhny, M. Zalcik, I. McEachran, T. McEwan, K. Äernis, J. Grønne, T. Taustrup, O. Hansen, H. Andersen, D. Melnikov, A. Manevich, V. Romejko, D. Lifatova,