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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 28, issue 8
Ann. Geophys., 28, 1559–1570, 2010
https://doi.org/10.5194/angeo-28-1559-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 28, 1559–1570, 2010
https://doi.org/10.5194/angeo-28-1559-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  19 Aug 2010

19 Aug 2010

IMF dependence of Saturn's auroras: modelling study of HST and Cassini data from 12–15 February 2008

E. S. Belenkaya1, I. I. Alexeev1, M. S. Blokhina1, E. J. Bunce2, S. W. H. Cowley2, J. D. Nichols2, V. V. Kalegaev1, V. G. Petrov3, and G. Provan2 E. S. Belenkaya et al.
  • 1Institute of Nuclear Physics, Moscow State University, Vorob'evy Gory, 119992 Moscow, Russia
  • 2Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK
  • 3Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Troitsk, Moscow Region, 142190, Russia

Abstract. To gain better understanding of auroral processes in Saturn's magnetosphere, we compare ultraviolet (UV) auroral images obtained by the Hubble Space Telescope (HST) with the position of the open-closed field line boundary in the ionosphere calculated using a magnetic field model that employs Cassini measurements of the interplanetary magnetic field (IMF) as input. Following earlier related studies of pre-orbit insertion data from January 2004 when Cassini was located ~ 1300 Saturn radii away from the planet, here we investigate the interval 12–15 February 2008, when UV images of Saturn's southern dayside aurora were obtained by the HST while the Cassini spacecraft measured the IMF in the solar wind just upstream of the dayside bow shock. This configuration thus provides an opportunity, unique to date, to determine the IMF impinging on Saturn's magnetosphere during imaging observations, without the need to take account of extended and uncertain interplanetary propagation delays. The paraboloid model of Saturn's magnetosphere is then employed to calculate the magnetospheric magnetic field structure and ionospheric open-closed field line boundary for averaged IMF vectors that correspond, with appropriate response delays, to four HST images. We show that the IMF-dependent open field region calculated from the model agrees reasonably well with the area lying poleward of the UV emissions, thus supporting the view that the poleward boundary of Saturn's auroral oval in the dayside ionosphere lies adjacent to the open-closed field line boundary.

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