Within the limits of non-continuous observations, in the images
on 28 and 30 January 2004 the auroral oval appeared to fade and
expand in radius on a timescale of several days. The long timescale
contrasts sharply with substorm processes at the Earth, possibly
reflecting the much larger scale size of Saturn’s magnetosphere.
Comparison with measurements of the approaching solar wind
from Cassini5 indicates that the auroral brightness and power
correlate best with the solar wind dynamic pressure, rather than
with any specific orientation of the IMF. Although solar wind
driving is reminiscent of substorms on the Earth, the brightening
of the dawn sector, the continued contraction of the oval, and the
primary correlation with solar wind dynamic pressure rather than
IMF direction are all characteristics that appear to be unique to
Saturn. The latitudinal motions of the main oval, large response to
solar wind changes, and filling in of the dawn side polar region are
all in contrast with Jupiter. In addition, the polar flares observed on
Jupiter have not been observed at Saturn. We conclude that among
the three magnetospheres in the Solar System sufficiently well
studied to be compared, the properties of auroral emissions at
Saturn are unique to that planet.
Within the limits of non-continuous observations, in the imageson 28 and 30 January 2004 the auroral oval appeared to fade andexpand in radius on a timescale of several days. The long timescalecontrasts sharply with substorm processes at the Earth, possiblyreflecting the much larger scale size of Saturn’s magnetosphere.Comparison with measurements of the approaching solar windfrom Cassini5 indicates that the auroral brightness and powercorrelate best with the solar wind dynamic pressure, rather thanwith any specific orientation of the IMF. Although solar winddriving is reminiscent of substorms on the Earth, the brighteningof the dawn sector, the continued contraction of the oval, and theprimary correlation with solar wind dynamic pressure rather thanIMF direction are all characteristics that appear to be unique toSaturn. The latitudinal motions of the main oval, large response tosolar wind changes, and filling in of the dawn side polar region areall in contrast with Jupiter. In addition, the polar flares observed onJupiter have not been observed at Saturn. We conclude that amongthe three magnetospheres in the Solar System sufficiently wellstudied to be compared, the properties of auroral emissions atSaturn are unique to that planet.
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