The winter anomaly in ionospheric absorption and the D-region ion chemistry |
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Authors: | Miguel A Hidalgo |
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Institution: | a Departamento de Física Fundamental, Facultad de Ciencias, Universidad de Zaragoza, Zaragoza, Spain b Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012, Bern, Switzerland |
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Abstract: | A detailed analysis of the D-region ion composition measurements performed by Zbinden et al. (1975), during a winter day of high ionospheric absorption, has been carried out. The study examines the interactive mesosphere-D-region processes which occur in such anomalous conditions and their implication for water cluster ion chemistry. Two clustering regimes for NO+ have been observed in the data. Association with N2 is identified as the dominant process below 76 km. Between 76 and 78 km altitude the effective loss rate of NO+ drops by two orders of magnitude. Above 77 km, the three-body reaction NO+ + CO2+M→NO+CO2+M seems to be the main NO+ loss. A mesospheric temperature profile could be derived from the ion composition data. This indicates the presence of a strong inversion above 76 km altitude. The wavelike structure obtained, is shown to be consistent with in situ winter temperature measurements. The sharp suppression of the N2 association reaction could, thus, be explained by an increase in the collisional break-up of the NO+N2 ion because of the enhanced temperature. In conclusion, our study indicates that, besides the increase in the production of NO+ and O2+, due to an enhancement in the minor ionizable constituents, an additional thermal mesosphere-D-region interaction seems necessary to explain this winter anomalous ion composition data. |
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