Solar wind influences on Saturn's magnetospheric and auroral dynamics
thesisposted on 15.12.2014, 10:40 by Sarah V. Badman
This thesis is concerned with the interaction between the solar wind and Saturn's magnetic and plasma environment. Four studies are presented, each investigating a different aspect of this interaction. In the first study estimates of the amount of open flux in Saturn's magnetosphere were made by analysing a sequence of images of Saturn's southern aurorae. Cassini spacecraft measurements of the upstream interplanetary conditions were then used to estimate the rate at which flux was opened on the dayside. These rates were compared with the observed amounts of open flux to deduce the average rate of flux closure between successive auroral images. Two types of flux closure event were identified: small, intermittent bursts during solar wind rare function regions, and large events during solar wind compressions. More auroral images were analysed in the second study as part of a statistical analysis of the location and width of Saturn's southern aurorae. The auroral oval was found typically to lie at ~15Â° co-latitude, with a width of ~2Â°, although with much variability between images. This typical location and the variability in the location suggest that Saturn's aurorae are generated by the varying interaction with the solar wind, rather than by steadier corotation-enforcement currents deeper within Saturn's magnetosphere. Next, the significance of the solar wind-driven flows in both Saturn's and Jupiter's magnetospheres was investigated. Under solar wind compression conditions these flows were predicted to form a significant layer a few planetary radii wide, adjacent to the dayside magnetopause, and composed of light solar wind ions. Finally, an investigation into the effect of solar wind compression on the emission of Saturn Kilometric Radiation (SKR) was carried out, concluding that the intensity of the SKR emissions increased during solar wind compressions, but the intensified emissions continued to pulse with the same periodicity as before the compression.