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Model-data comparisons for Titan's nightside ionosphere |
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| Authors: | TE Cravens IP Robertson RV Yelle AJ Coates K Agren V De La Haye FM Neubauer |
| Institution: | a Department of Physics and Astronomy, Malott Hall, 1251 Wescoe Hall Dr., University of Kansas, Lawrence, KS 66045, USA b Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228-0510, USA c Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721-0092, USA d University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK e Swedish Institute of Space Physics, Uppsala Division, Box 537, SE-751 21 Uppsala, Sweden f Institut für Geophysik und Meteorologie, Universität zu Köln, Cologne, Germany |
| Abstract: | Solar and X-ray radiation and energetic plasma from Saturn's magnetosphere interact with the upper atmosphere producing an ionosphere at Titan. The highly coupled ionosphere and upper atmosphere system mediates the interaction between Titan and the external environment. A model of Titan's nightside ionosphere will be described and the results compared with data from the Ion and Neutral Mass Spectrometer (INMS) and the Langmuir probe (LP) part of the Radio and Plasma Wave (RPWS) experiment for the T5 and T21 nightside encounters of the Cassini Orbiter with Titan. Electron impact ionization associated with the precipitation of magnetospheric electrons into the upper atmosphere is assumed to be the source of the nightside ionosphere, at least for altitudes above 1000 km. Magnetospheric electron fluxes measured by the Cassini electron spectrometer (CAPS ELS) are used as an input for the model. The model is used to interpret the observed composition and structure of the T5 and T21 ionospheres. The densities of many ion species (e.g., CH+5 and C2H+5) measured during T5 exhibit temporal and/or spatial variations apparently associated with variations in the fluxes of energetic electrons that precipitate into the atmosphere from Saturn's magnetosphere. |
| Keywords: | Titan Saturn magnetosphere Ionospheres Atmospheres chemistry Atmospheres composition |
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