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C.S. Arridge (The Blackett Laboratory, Imperial College London, UK), C.T. Russell, K.K. Khurana (Institute of Geophysics and Planetary Physics, UCLA, USA), M.K. Dougherty (The Blackett Laboratory, Imperial College London, UK), J.S. Leisner (Institute of Geophysics and Planetary Physics, UCLA, USA)
Quasi-periodic short-duration current sheet crossings have been found in Cassini magnetometer data, in the dawn and pre-noon sector of Saturn's magnetosphere. These current sheet crossings are used to directly estimate the jxB force from the magnetic field data in the vicinity of the current sheet [Russell et al. 1999]. We show that the radial profile of magnetic stress indicates the presence of a magnetodisc region in Saturn's magnetosphere, as observed in the jovian magnetosphere. We compare this profile with that expected for a vacuum dipole field to highlight it’s presence and radial extent.
This observational result is compared with the stress balance implicit in several empirical field models [Connerney et al. 1983; Arridge et al. 2005; Khurana et al. 2005]. Thus, by examining the curl and curl-free parts of the jxB force, as evaluated from the models, we can infer the relative roles of pressure gradient/centrifugal and pressure anisotropic stress in determining the force balance. Our results are compared and contrasted with stress balance investigations in the terrestrial magnetosphere [e.g. Zaharia and Cheng 2003] and at the outer planets [e.g. McNutt 1983; Paranicas et al. 1991; Russell et al. 1999].
The balance of mechanical stress in the magnetosphere has a core role in understanding the operation of Saturn's Magnetospheric Engine involving the energisation and transport of plasma and magnetic flux. We comment on the implications of these stress balance results on the magnetospheric engine, and on the shape and pressure-dependent behaviour of the kronian magnetopause.
The author(s) of this abstract have provided an email address for comments about the abstract: christopher.arridge@ic.ac.uk
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.