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Ann. Geophys., 24, 1649-1663, 2006
www.ann-geophys.net/24/1649/2006/
© European Geosciences Union 2006
Saturn's aurora in the January 2004 events
E. S. Belenkaya1, S. W. H. Cowley2, and I. I. Alexeev1
1Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow 119992, Russia
2Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
Abstract. Differences in the solar wind interaction with the magnetosphere of
Saturn relative to the Earth result from the decrease in the solar wind plasma
density and magnetic field strength with distance from the Sun, and from the
change in the average angle of the IMF at Saturn's orbit.
Other reasons are related to Saturn's rapid rotation and internal
magnetospheric plasma sources. Moreover, the IMF structure observed
by Cassini in 2003–2004 during the approach to Saturn is consistent with corotating
interaction regions (CIRs) existing during the declining phase of the
solar cycle. Two cases on 16 and 26 January 2004 are
considered when disturbances in the solar wind passed Cassini and then Saturn. After
the solar wind shock encountered the kronian magnetosphere, the
auroral oval became brighter (especially at dawn) with a reduced
radius. In these cases the auroral power was anti-correlated with the
radius of the oval. Possible mechanisms responsible for such
unexpected behavior are presented and discussed in detail.
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