Saturn's Magnetospheric Cusp: Cassini Observations

Wednesday, 16 December 2015
Poster Hall (Moscone South)
Jamie Matthew Jasinski1,2, Christopher Stephen Arridge3, Nick Sergis4, Andrew J Coates5 and Geraint H Jones5, (1)University College London, London, United Kingdom, (2)University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, (3)University of Lancaster, Department of Physics, Lancaster, United Kingdom, (4)National and Kapodistrian University of Athens, Athens, Greece, (5)University College London, Centre for Planetary Sciences (at UCL/Birkbeck), London, United Kingdom
The first in-situ analysis of the high-latitude magnetospheric cusp region at Saturn is presented using data from the Cassini spacecraft. The cusp is a funnel-shaped region where shocked solar wind plasma is able to enter the magnetosphere via the process of magnetic reconnection. The analysis is presented in three sections:

Firstly, a high-latitude spacecraft trajectory is shown to cross the northern cusp where magnetosheath plasma is observed in-situ. The ion observations are shown to be a result of `bursty' reconnection occurring at the dayside magnetopause. A different interval is also presented where the southern cusp is observed to oscillate with a period the same as Saturn’s rotational period.

Secondly, the locations of all the cusp crossings are shown. The field-aligned distances (calculated from observed ion energy-pitch angle dispersions) from the reconnection site are presented. The cusp events are also compared to solar wind propagation models to investigate any correlations.

Finally, the magnetic field observations of the cusps are analysed focusing on the diamagnetic depressions. The data are subtracted from a magnetic field model, and the calculated magnetic pressure deficits are compared to the particle pressures. A high plasma pressure layer in the magnetosphere adjacent to the cusp is discovered to also depress the magnetic field.