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E. J. Smith, G. Giampieri (Jet Propulsion Laboratory), M. K. Dougherty (Imperial College), C. T. Russell (UCLA)
Magnetic field measurements on Cassini orbiter are raising significant scientific questions, part of an ambitious program made possible by the large number of successive orbits that map the field over a wide range of distance, latitude, longitude and local time. Measurements of unprecedented accuracy are obtained using vector and scalar magnetometers, a powerful combination previously restricted to studies of the geomagnetic field. Scalar or vector data alone or in combination are inverted to obtain spherical harmonic moments of the planetary field. Improved knowledge of these moments, especially those beyond dipole, quadrupole and octupole, provide essential information on Saturn's interior and dynamo region. Although the Cassini observations have confirmed the unique axisymmetry of the field around Saturn's rotation axis, a persistent periodicity is never-the-less present with a period essentially the same as seen in the Saturn Kilometric Radiation with an amplitude that is virtually constant. The cause of this periodicity and its relation to the planetary rotation rate are under investigation. The periodicity may be an aspect of the Stevenson hypothesis that the shielding of non-axisymmetric dynamo fields by an over-lying differentially rotating conducting shell are less effective for fields originating at high latitude. It may be the effect of the hot particle injections seen regularly in Cassini plasma and energetic particle observations that co-rotate with the magnetic field. We also report exciting new results involving the magnetospheric field, for example, variations that appear to be related to Saturn's rings and/or its large satellites and changes in the magnetospheric current disk.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.