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| Titel |
Coupled rotational dynamics of Jupiter's thermosphere and magnetosphere |
| VerfasserIn |
C. G. A. Smith, A. D. Aylward |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 27, no. 1 ; Nr. 27, no. 1 (2009-01-13), S.199-230 |
| Datensatznummer |
250016366
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| Publikation (Nr.) |
 copernicus.org/angeo-27-199-2009.pdf |
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| Zusammenfassung |
| We describe an axisymmetric model of the coupled rotational dynamics of the
thermosphere and magnetosphere of Jupiter that incorporates self-consistent
physical descriptions of angular momentum transfer in both systems. The
thermospheric component of the model is a numerical general circulation
model. The middle magnetosphere is described by a simple physical model of
angular momentum transfer that incorporates self-consistently the effects of
variations in the ionospheric conductivity. The outer magnetosphere is
described by a model that assumes the existence of a Dungey cycle type
interaction with the solar wind, producing at the planet a largely stagnant
plasma flow poleward of the main auroral oval. We neglect any decoupling
between the plasma flows in the magnetosphere and ionosphere due to the
formation of parallel electric fields in the magnetosphere. The model shows
that the principle mechanism by which angular momentum is supplied to the
polar thermosphere is meridional advection and that mean-field Joule heating
and ion drag at high latitudes are not responsible for the high thermospheric
temperatures at low latitudes on Jupiter. The rotational dynamics of the
magnetosphere at radial distances beyond ~30 RJ in the equatorial
plane are qualitatively unaffected by including the detailed dynamics of the
thermosphere, but within this radial distance the rotation of the
magnetosphere is very sensitive to the rotation velocity of the thermosphere
and the value of the Pedersen conductivity. In particular, the thermosphere
connected to the inner magnetosphere is found to super-corotate, such that
true Pedersen conductivities smaller than previously predicted are required
to enforce the observed rotation of the magnetosphere within ~30 RJ. We
find that increasing the Joule heating at high latitudes by adding a
component due to rapidly fluctuating electric fields is unable to explain the
high equatorial temperatures. Adding a component of Joule heating due to
fluctuations at low latitudes is able to explain the high equatorial
temperatures, but the thermospheric wind systems generated by this heating
cause super-corotation of the inner magnetosphere in contradiction to the
observations. We conclude that the coupled model is a particularly useful
tool for study of the thermosphere as it allows us to constrain the
plausibility of predicted thermospheric structures using existing
observations of the magnetosphere. |
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