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Saturn's auroral/polar H3 infrared emission: II. A comparison with plasma flow models |
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| Authors: | Tom Stallard Chris Smith Henrik Melin Alan Aylward Michele Dougherty |
| Institution: | a Radio and Space Plasma Physics Group, Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK b Atmospheric Physics Laboratory, Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK c Space Environment Technologies, Planetary and Space Science Division, 320 N. Halstead St, Suite 170, Pasadena, CA 91107, USA d Space and Atmospheric Physics Group, Department of Physics, Imperial College of Science, Technology and Medicine, South Kensington Campus, London SW7 2AZ, UK |
| Abstract: | We present a detailed analysis of the H+3 intensity and velocity profiles crossing Saturn's auroral/polar region, as described by Stallard et al. Stallard, T., Miller, S., Melin, H., Lystrup, M., Dougherty, M., Achilleos, N., 2007. Icarus 189, 1-13], with a view to understanding the magnetospheric processes with which they are connected. The data are not consistent with the theory that Saturn's main auroral oval is associated with corotation enforcement currents in the middle magnetosphere. This implies that the main auroral oval can be associated with the open-closed field line boundary Cowley, S.W.H., Bunce, E.J., O'Rourke, J.M., 2004. J. Geophys. Res. 109. A05212]; a third model, by Sittler et al. Sittler, E.C., Blanc, M.F., Richardson, J.D., 2006. J. Geophys. Res. 111. A06208] associates the main oval with centrifugal instabilities in the outer magnetosphere, but does not make predictions about ionospheric plasma flows with which we can compare our data. We do, however, tentatively identify emission at latitudes lower than the main auroral oval which may be associated with the corotation enforcement currents in the middle magnetosphere. We also find that at latitudes higher than the main auroral oval there is often a region of the ionosphere that is in rigid corotation with the planet. We suggest that this region corresponds to field lines embedded in the centre of the magnetotail which are shielded from the solar wind such that their rotation is controlled only by the neutral atmosphere. |
| Keywords: | Aurorae Ionospheres Infrared observations Saturn magnetosphere Saturn atmosphere |
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