Investigation of Saturn’s Polar Cap Boundary during Cassini’s 2013 High-Latitude Orbits
S. L. Jinks
University of Leicester (1: Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK)
E.J. Bunce (1), G. Provan (1), T.K. Yeoman (1), S.W.H. Cowley (1), G. J. Hunt (1) W.S. Kurth (University of Iowa, Iowa City, Iowa 52242, USA), D.G. Mitchell (Johns Hopkins University, Maryland), and M.K. Dougherty (Imperial College London, SW7 2AZ, UK).
Since 2004, the Cassini spacecraft’s orbits of Saturn have provided extensive observations of the giant planet’s magnetosphere. Here we present a Cassini multi-instrument assessment of the location of the polar cap boundary between “open” and “closed” magnetic field lines for the 2013 high-latitude orbits (including the Saturn auroral observing campaign in April-May 2013). We discuss the extent to which the different instruments can locate a common boundary and identify the average co-latitude of the boundary region in each hemisphere. The average co-latitude of the upward field-aligned current region is identified equatorward of the polar cap boundary in each hemisphere. We discuss the dependence of the position and morphology of these currents, and that of the polar cap boundary, in the southern hemisphere on the southern planetary period oscillations (PPOs). We attempt to also investigate the northern polar cap boundary’s dependence on the northern PPOs.
We examine how the structure and organisation of the polar cap boundary and field-aligned currents respond to enhanced solar wind dynamics. Thus, we present how the polar cap region morphology typically varies due to co-rotating interaction region (CIR) compressions.