thesis

Titan's interaction with the Saturnian magnetosphere

Abstract

In this thesis, a combination of data analysis and test particle simulations is used in order to study several aspects of the complex interaction of Titan with the Saturnian magnetosphere. First, the energetic charged particles environment at the orbital distance of Titan is studied using data from the MIMI/LEMMS instrument. Average fluxes and spectral slopes for energetic ions and electrons are analysed. A large variability is found, and it is interpreted as originated from the high mobility of the energetic ions and electrons, making a simple classification of this environment practically impossible, with only a weak correlation between the ion average fluxes with the plasma environment detectable and an asymmetry between the noon-to-dusk and midnight-to-dawn sectors. Second, the effect of local electromagnetic field disturbances in the access of energetic H+ and O+ ions is studied. By studying the trajectories of individual particles to predict where they will deposit their energy, differences in ionisation rates at different locations around the moon of almost 80% are found for H+ ions and of more than 15% for the case of O+ ions. Finally, the contribution of freshly produced pickup ions to the overall mass loss of the atmosphere is investigated by looking at particular signatures left by these ions in the thermal plasma data from the CAPS/IMS instrument. A statistical survey of all the flybys with available data leads to a constraint of the region around the moon where these ions are detected. Mass losses on the anti-Saturn side of the moon of between 570 kg/day and 1 tonne/day are derived depending on the species, accounting for a small fraction of the total losses estimated from distant tail observations

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