Model calculations of the ionosphere of Titan during eclipse conditions

This report is based on data from the Cassini spacecraft and the main aim of this work is to model the ionosphere of Titan and compare it with data from the sixth flyby (T5). It occurred April 16, 2005, and was chosen as it was a nightside pass of the moon. We have shown that magnetospheric impacting electrons alone can account for the observed ionisation during T5. Data from Cassini show that the main constituents of Titan's atmosphere are molecular nitrogen, methane and molecular hydrogen, with nitrogen being the most common species at low altitudes. There are also several minor species contributing to the chemical reactions taking place in the atmosphere. A method by M. H. Rees is used to calculate the ionisation rate height profiles. It can be shown that modifications of the flux value change the magnitude of the ionisation rate and that the electrons penetrate deeper into the ionosphere the more energy they are given. For electrons of energies lower than 200 eV the ionisation rate cannot be calculated by the method mentioned above. We therefore have to introduce a model by Prof. D. Lummerzheim to infer the ionisation rates of lower energy electrons in order to achieve a more complete picture. Combining the results, we can look at the dependence between the ionisation maxima in kilometres and the electron energy. The electrons penetrate deeper into the ionosphere given more energy, with a steep gradient for low energies, which gradually decreases for higher energies. By looking at the main chemical reactions that take place in Titan's ionosphere we can calculate the densities of the ion species. These results are compared with actual data with good agreement. Finally, we look at the electron density received from our model and compare it to the density measured by the Langmuir probe on Cassini, which leads us to the conclusion that magnetospheric electrons do account for the observed electron density.Validerat; 20101217 (root