Magnetic interconnection of Saturn’s polar regions: compariDsioscnussioonfs modelling results with Hubble Space Telescope (HST) UV auroral imagesстатья
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Аннотация:We consider the magnetic interconnection of Saturn’s
northern and southern polar regions controlled by the
interplanetary magnetic field (IMF), studying in particular
the more complex and interesting case of southward IMF,
when the Kronian magnetospheric magnetic field structure
is the most twisted. The simpler case of northward IMF is
also discussed. Knowledge of the magnetospheric magnetic
field structure is very significant, for example, for investigation
of the electric fields and field-aligned currents in Saturn’s
environment, particularly those which cause the auroral
emissions. Here we modify the paraboloid magnetospheric
magnetic field model employed in previous related
studies by including higher multipole terms in Saturn’s internal
magnetic field, required for more detailed considerations
of inter-hemispheric conjugacy, together with inclusion
of a spheroidal boundary at the ionospheric level. The model
is employed to map Southern Hemisphere auroral regions
observed by Hubble Space Telescope (HST) in 2008 under
known IMF conditions to both the equatorial plane and the
northern ionosphere. It is shown that the brightest auroral
features map typically to the equatorial region between the
central ring current and the outer magnetosphere, and that auroral
features should be largely symmetric between the two
hemispheres, except for a small poleward displacement and
latitudinal narrowing in the Northern Hemisphere compared
with the Southern Hemisphere due to the quadrupole field
asymmetry. The latter features are in agreement with the conjugate
auroras observed under near-equinoctial conditions in
early 2009, when IMF data are not available.