Dependence of the open-closed field line boundary in Saturn’s ionosphere on both the IMF and solar wind dynamic pressure: comparison with the UV auroral oval observed by the HSTстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:We model the open magnetic field region in Saturn’s
southern polar ionosphere during two compression regions
observed by the Cassini spacecraft upstream of Saturn
in January 2004, and compare these with the auroral ovals
observed simultaneously in ultraviolet images obtained by
the Hubble Space Telescope. The modelling employs the
paraboloid model of Saturn’s magnetospheric magnetic field,
whose parameters are varied according to the observed values
of both the solar wind dynamic pressure and the interplanetary
magnetic field (IMF) vector. It is shown that the
open field area responds strongly to the IMF vector for both
expanded and compressed magnetic models, corresponding
to low and high dynamic pressure, respectively. It is also
shown that the computed open field region agrees with the
poleward boundary of the auroras as well as or better than
those derived previously from a model in which only the variation
of the IMF vector was taken into account. The results
again support the hypothesis that the auroral oval at Saturn
is associated with the open-closed field line boundary and
hence with the solar wind interaction.