Milan, S. E.[Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK]
Hutchinson, J.[Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK]
Boakes, P. D.[Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK; British Antarctic Survey, Natural Environment Research Council, High Cross, Cambridge, UK]
Hubert, Benoît[Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP) >]
[en] 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.
[Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK]
