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G Giampieri, M.K. Dougherty (Imperial College London), C.T. Russell (UCLA), E.J. Smith (NASA/JPL)
E We present new magnetic field data measured by the Cassini spacecraft during Saturn Orbit Insertion (SOI). The observed data are analyzed using standard inversion techniques, and a preliminary model of the internal field is presented. The zonal coefficients are found to be in good agreement with previous models derived from the Pioneer 11, Voyager 1 and Voyager 2 flybys.
One striking feature of past models is the lack of non axisymmetric terms. We have reanalyzed past flyby data, and concluded that no certain conclusion on the axial symmetry of the field can be obtained from flyby observations alone, due to the uncertainty in our knowledge of the planetary rotation rate. We then propose a method for obtaining the first direct measurement of the rotation rate of the magnetic field, which is found to be 10h39m23.0s, in close agreement with the IAU value.
A full picture of the internal magnetic field of Saturn, including its rotation state and the degree of its axial symmetry, will be revealed by Cassini, which will map the field at various longitudes and latitudes during the orbital tour.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.