Model studies of hydroxyl airglow under the influence of ionization.

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Emissions of vibrationally excited hydroxyl molecules OH* are useful indicators for dynamical and chemical processes in the terrestrial mesosphere. The response of OH* to sporadic ionization events provides an interesting opportunity to test our understanding of these chemical and dynamical processes. However, the observed perturbations of OH* emissions during ionization events are hardly understood. Solar particle events give rise to pronounced OH* emission disturbances which have not been reproduced by atmospheric models yet. Furthermore, the bright OH* emissions due to electric breakdown events above active thunderstorms are much stronger than the predictions of plasma chemistry simulations. The aim of this project is to investigate the effects of ionization on OH* in the mesosphere. For this purpose, existing ion and plasma chemistry models will be improved and used to study the chemical processes in detail. In particular, the proposed production of OH* through vibrationally excited nitrogen molecules in electric discharges will be considered. Additionally, the potential effect of temperature enhancements due to ionization events will be investigated. The model results will be compared to satellite observations of OH* emissions.