Stuttgart 2012 – scientific programme
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EP: Fachverband Extraterrestrische Physik
EP 1: Erdnaher Weltraum
EP 1.5: Talk
Monday, March 12, 2012, 15:30–15:45, V55.02
Solar influence on the MLT region: NOx production during solar proton events and ion chemistry — •Holger Nieder1, Miriam Sinnhuber1, Holger Winkler2, Jan Maik Wissing3, Daniel Marsh4, and Johannes Orphal1 — 1Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research — 2University of Bremen, Institute of Environmental Physics — 3University of Osnabrück — 4National Center for Atmospheric Research, Boulder
The chemistry in the mesosphere/lower thermosphere (MLT) region is always driven by forcing from solar radiation and energetic particles. The resulting ionisation, dissociation and excitation of the constituents lead to production of reactive species such as NOx (N, NO, NO2) and HOx (H, OH, HO2), both directly from dissociation as well as indirectly from subsequent ion chemistry reactions. While the ions and HOx are short lived and disappear when the forcing is over, NOx is transported downwards and contributes to ozone depletion.
Approximately, the production rate of NOx is proportional to the ionisation rate, while the loss primarily results from the photolytic dissociation of NO. High ionisation rates usually occur during Solar Proton Events (SPEs) and geomagnetic storms (aurora and radiation belt particles) where energetic electrons and protons penetrate the earth's atmosphere in polar latitudes.
The production rates of NOx are modeled using an ion chemistry model and their dependency on various parameters such as altitude and ionisation rate is discussed.