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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 27, issue 7
Ann. Geophys., 27, 2913–2924, 2009
https://doi.org/10.5194/angeo-27-2913-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 27, 2913–2924, 2009
https://doi.org/10.5194/angeo-27-2913-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  23 Jul 2009

23 Jul 2009

Influences on the radius of the auroral oval

S. E. Milan1, J. Hutchinson1, P. D. Boakes1,2, and B. Hubert3 S. E. Milan et al.
  • 1Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
  • 2British Antarctic Survey, Natural Environment Research Council, High Cross, Cambridge, UK
  • 3Laboratory of Planetary and Atmospheric Physics, University of Liége, Liége, 4000 Belgium

Abstract. We examine the variation in the radius of the auroral oval, as measured from auroral images gathered by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft, in response to solar wind inputs measured by the Advanced Composition Explorer (ACE) spacecraft for the two year interval June 2000 to May 2002. Our main finding is that the oval radius increases when the ring current, as measured by the Sym-H index, is intensified during geomagnetic storms. We discuss our findings within the context of the expanding/contracting polar cap paradigm, in terms of a modification of substorm onset conditions by the magnetic perturbation associated with the ring current.

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