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Cassini observations of ionospheric plasma sources and plasma distribution in Saturn’s magnetosphere

Felici, M; (2016) Cassini observations of ionospheric plasma sources and plasma distribution in Saturn’s magnetosphere. Doctoral thesis , UCL (University College London).

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Abstract

This thesis utilises data from the Cassini spacecraft in the analysis of the Saturnian system focusing on two areas of research. The first is estimating the impact of the ionosphere as a plasma source in the system, from a case study that uses data from the thermal plasma spectrometer, the UV imager, the energetic particle detectors, and radio and plasma wave detector, when the spacecraft was located at ~ 2200 hours Saturn local time at 36 RS in Saturns magnetotail, and the second consists in a survey of the bulk plasma composition using time-of-flight data from CAPS/IMS, from 2004 to 2013, that is, at the moment, the most extensive survey conducted on TOF/IMS data. We find the first evidence of polar ionospheric outflow from Saturn. During several entries into the magnetotail lobe, cold ions (mainly H+ and (m/q=2)), and electrons, dispersed in energy, were observed directly adjacent to the plasma sheet and, apparently, extending into the lobe. Moreover, ions were flowing downtail. The unique nature of this event led to two survey studies, with different resolutions and coordinate systems, to investigate typical and atypical characteristics in bulk plasma composition and its relations to Enceladus, Dione, Rhea, and Titan. We studied [(m/q=2)]/[H+], [W+]/[H+], and [O+, OH+, H2O+, H3O+]/[W+] ratios, where we indicate with W+ ions produced from water, as a function of position in the magnetosphere, radial distance and local time, and distance from the planet and longitude in respect to the moons. We found that the plasma composition in Saturn’s magnetosphere presents significant local time asymmetries and variability. Some evidence of displacement of the stagnation point towards earlier local times (~ 1900 LT) compared to Cowley et al. [2004]’s plasma circulation model, suggests that the solar wind has greater influence on Saturn’s magnetosphere.

Type: Thesis (Doctoral)
Title: Cassini observations of ionospheric plasma sources and plasma distribution in Saturn’s magnetosphere
Event: UCL (University College London)
Language: English
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1530897
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