Swept Forward Magnetic Field Variability in High‐Latitude Regions of Saturn's Magnetosphere

Abstract

Swept forward field is the term given to configurations of magnetic field wherein the field lines deviate from the meridional planes of a planet in the direction of its rotation. Evidence is presented for swept‐forward field configurations on Cassini orbits around Saturn from the first half of 2008. These orbits were selected on the basis of high inclination, spatial proximity, and temporal proximity, allowing for the observation of swept‐forward field and resolution of dynamic effects using data from the Cassini magnetometer. Nine orbits are surveyed; all show evidence of swept‐forward field, with typical sweep angle found to be 23°. Evidence is found for transient events that lead to temporary dramatic increases in sweep‐forward angle. The Michigan Solar Wind Model is employed to investigate temporal correlation between the arrivals of solar wind shocks at Saturn with these transient events, with two shown to include instances corresponding with solar wind shock arrivals. Measurements of equatorial electron number density from anode 5 of the Cassini Plasma Spectrometer instrument are investigated for evidence of magnetospheric compression, corresponding with predicted shock arrivals. Potential mechanisms for the transfer of momentum from the solar wind to the magnetosphere are discussed.

Current Density in Saturn's Equatorial Current Sheet: Cassini Magnetometer Observations

“…Kivelson et al (2002) state that the distance from the equator is a variable that can affect the direction of the azimuthal magnetic field, as higher latitudes may be influenced by an additional current system that closes the magnetospheric current. Following, Davies et al (2017) showed that swept-forward fields in the high latitudes are swept forward due to solar wind compressions and show modulation from planetary period oscillations, and hence, we may assume that swept-forward field seen at the equator may also be solar wind driven. As the aperiodic waves used to calculate the current density in the sheet are a direct sampling of the current sheet by Cassini, we can assume that this latitudinal effect is not affecting the data.…”