Journal Article

A Saturnian cam current system driven by asymmetric thermospheric heating

C. G. A. Smith

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 410, issue 4, pages 2315-2328
Published in print February 2011 | ISSN: 0035-8711
Published online January 2011 | e-ISSN: 1365-2966 | DOI:
A Saturnian cam current system driven by asymmetric thermospheric heating

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We show that asymmetric heating of Saturn's thermosphere can drive a current system consistent with the magnetospheric ‘cam’ proposed by Espinosa, Southwood & Dougherty. A geometrically simple heating distribution is imposed on the Northern hemisphere of a simplified three-dimensional global circulation model of Saturn's thermosphere. Currents driven by the resulting winds are calculated using a globally averaged ionosphere model. Using a simple assumption about how divergences in these currents close by flowing along dipolar field lines between the Northern and Southern hemispheres, we estimate the magnetic field perturbations in the equatorial plane and show that they are broadly consistent with the proposed cam fields, showing a roughly uniform field implying radial and azimuthal components in quadrature. We also identify a small longitudinal phase drift in the cam current with radial distance as a characteristic of a thermosphere-driven current system. However, at present our model does not produce magnetic field perturbations of the required magnitude, falling short by a factor of ∼100, a discrepancy that may be a consequence of an incomplete model of the ionospheric conductance.

Keywords: magnetic fields; methods: numerical; planets and satellites: atmospheres; planets and satellites: individual: Saturn; planets and satellites: magnetic fields

Journal Article.  9625 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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