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A superposed epoch analysis of auroral evolution during substorms: Local time of onset region

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journal contribution
posted on 24.10.2012, 09:06 by S. E. Milan, A. Grocott, B. Hubert
[1] Previous workers have shown that the magnetic local time (MLT) of substorm onset depends on the prevailing east-west component of the interplanetary magnetic field (IMF). To investigate the influence of the onset MLT on the subsequent auroral response we perform a superposed epoch analysis of the auroral evolution during approximately 2000 substorms using observations from the FUV instrument on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. We subdivide the substorms by onset latitude and onset local time before determining average auroral images before and after substorm onset, for both electron and proton aurorae. We find that during the growth phase there is preexisting auroral emission in the MLT sector of the subsequent onset. After onset the auroral bulge expands eastward and westward, but remains centered on the onset sector. Approximately 30 min after onset, during the substorm recovery phase, the peaks in electron and proton auroral emission move into the postnoon and prenoon sectors, respectively, reflecting the “average” auroral precipitation patterns determined by previous studies. Superposed epoch analysis of the interplanetary magnetic field for the substorms under study suggests that the BY component of the IMF must be biased toward positive or negative values for up to a day prior to onset for the onset MLT to be influenced.

History

Citation

Journal of Geophysical Research-SPACE PHYSICS, 2010, 115

Version

VoR (Version of Record)

Published in

Journal of Geophysical Research-SPACE PHYSICS

Publisher

American Geophysical Union (AGU); Wiley

issn

0148-0227

Copyright date

2010

Available date

24/10/2012

Publisher version

http://onlinelibrary.wiley.com/doi/10.1029/2010JA015663/abstract

Language

English