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Ann. Geophys., 23, 2465-2477, 2005
www.ann-geophys.net/23/2465/2005/
© European Geosciences Union 2005
Polar heating in Saturn's thermosphere
C. G. A. Smith1, A. D. Aylward1, S. Miller1, and I. C. F. Müller-Wodarg2
1Atmospheric Physics Laboratory, Department of Physics and Astronomy, University College, London, UK
2Space and Atmospheric Physics Group, Imperial College London, London, UK
Abstract. A 3-D numerical global circulation model of the Kronian
thermosphere has been used to investigate the influence of polar heating. The
distributions of temperature and winds resulting from a general heat source
in the polar regions are described. We show that both the total energy input
and its vertical distribution are important to the resulting thermal
structure. We find that the form of the topside heating profile is
particularly important in determining exospheric temperatures. We compare our
results to exospheric temperatures from Voyager occultation measurements (Smith et al., 1983; Festou and Atreya, 1982) and auroral H3+ temperatures from ground-based
spectroscopic observations (e.g. Miller et al., 2000). We find that a polar
heat source is consistent with both the Smith et al. determination
of T∞~400 K at ~30° N and auroral temperatures.
The required heat source is also consistent with recent estimates of the
Joule heating rate at Saturn (Cowley et al., 2004). However, our results
show that a polar heat source can probably not explain the Festou and Atreya determination of T∞~800 K at
~4° N and the auroral temperatures simultaneously.
Keywords. Ionosphere (Planetary ionosphere) – Magnetospherica
physics (Planetary magnetospheres) – Meterology
and atmospheric dynamics (Thermospheric dynamics)
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