Abstract
AbstractThe recent survey by Andrews et al. (2012) of the separate northern and southern ~10.7 h periodic magnetic signals in Saturn's magnetosphere limits very much their governing current systems. The existence of signals with pure or close to pure northern or southern periods in respective polar caps taken with the relatively narrow bandwidth of the signals indicates that the actual periodicities are imposed independently from northern and southern polar regions, i.e., the open field line regions. Field‐aligned currents must flow on the boundaries of these regions to exclude signals from the other hemisphere. Equatorward of the polar cap, on closed magnetic shells, there are distinct north and south “cam” source currents, the distinction being made clear by a difference in polarization. We outline the consequences for the governing current systems and the implications for sustaining the energy and power dissipation in the system.
Highlights
Almost everywhere in Saturn’s magnetosphere there are magnetic oscillations seen with periods close to 10.7 h
The existence of signals with pure or close to pure northern or southern periods in respective polar caps taken with the relatively narrow bandwidth of the signals indicates that the actual periodicities are imposed independently from northern and southern polar regions, i.e., the open field line regions
If the plasma on the closed field lines were rotating at the same rate as the polar caps, as was assumed in the works of Goldreich and Farmer [2007] and Gurnett et al [2007], this energy source would contribute in maintaining the current system we are discussing here
Summary
Almost everywhere in Saturn’s magnetosphere there are magnetic oscillations seen with periods close to 10.7 h. The currents flow near the outer edge of the dipolar field lines and have an m = 1 axial symmetry about Saturn’s rotation/magnetic axis. The currents flow along the field through the equatorial region They cannot be due to ionospheric-magnetospheric coupling but must almost certainly represent coupling between northern and southern ionospheres as well. We further look at the implications of the different polarization and localization of the northern and southern signals in regard to the transfer of stress between hemispheres
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