Magnetic Field and Plasma in Saturn's Near Space Environment

Abstract

This thesis concerns spacecraft observations of magnetic field and plasma in Saturn’s near space environment and compares these observations with those made in and near the Jovian magnetosphere. Such comparisons are equivalent to ‘turning the experimental dial’ in planetary magnetospheres and provide a valuable insight into the way different parameters govern the structure and dynamics of magnetospheres throughout the solar system. Saturn and its magnetosphere is currently being studied by the Cassini spacecraft which, arriving at Saturn in the summer of 2004, became the first spacecraft ever to enter orbit around the planet. As a result there has never been a better time to study the Saturn system and the vast majority of the data utilized in this thesis were obtained by the Cassini spacecraft and its onboard instrumentation. Additional data were also obtained from the Pioneer, Voyager, Ulysses and Galileo spacecraft. Chapter 1 provides a general overview of space plasma and magnetospheric physics while Chapter 2 discusses the Saturn system in more detail. Chapter 3 describes the spacecraft and instrumentation used in this thesis with particular emphasis placed on magnetometer instruments and the Cassini-Huygens spacecraft. Chapter 4 compares the structure of Jupiter’s and Saturn’s outer magnetospheres and discusses the similarities and differences between the two. Chapter 5 presents a new empirical model of Saturn’s dayside bow shock and discusses the three dimensional shape of this surface while, finally, Chapter 6 presents observations of a magnetic cavity in the Saturnian magnetosphere which, as of writing, has yet to be explained. Chapter 7 summarises and concludes the thesis. The three independent investigations described above each shed light on a different aspect of Saturn’s magnetospheric structure and dynamics and contributes to an improved understanding of magnetospheric physics in general.