[en] We perform two superposed epoch analyses of the auroral evolution during substorms using the FUV instrument on the Imager for Magnetopause-to-Aurora Global Explorer (IMAGE) spacecraft. The larger of the two studies includes nearly 2000 substorms. We subdivide the substorms by onset latitude, a measure of the open magnetic flux in the magnetosphere, and determine average auroral images before and after substorm onset, for both electron and proton aurora. Our results indicate that substorms are more intense in terms of auroral brightness when the open flux content of the magnetosphere is larger, and that magnetic flux closure is more significant. The increase in auroral brightness at onset is larger for electrons than protons. We also show that there is a dawn-dusk offset in the location of the electron and proton aurora that mirrors the relative locations of the region 1 and region 2 current systems. Superposed epoch analyses of the solar wind, interplanetary magnetic field, and geomagnetic indices for the substorms under study indicate that dayside reconnection is expected to occur at a faster rate prior to low latitude onsets, but also that the ring current is enhanced for these events.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Milan, S. E.; Department of Physics and Astronomy, University of Leicester, Leicester, UK
Grocott, A.; Department of Physics and Astronomy, University of Leicester, Leicester, UK
Forsyth, C.; Department of Physics and Astronomy, University of Leicester, Leicester, UK ; Mullard Space Sciences Laboratory, University College London, Surrey, UK
Imber, S. M.; Department of Physics and Astronomy, University of Leicester, Leicester, UK ; Heliophysics Division, NASA GSFC, Greenbelt, MD, USA
Boakes, P. D.; Department of Physics and Astronomy, University of Leicester, Leicester, UK ; British Antarctic Survey, Natural Environment Research Council, High Cross, Cambridge, UK
Hubert, Benoît ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Labo de physique atmosphérique et planétaire (LPAP)
Language :
English
Title :
A superposed epoch analysis of auroral evolution during substorm growth, onset and recovery: open magnetic flux control of substorm intensity
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