Combined THEMIS and ground-based observations of a pair of s

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TitleCombined THEMIS and ground-based observations of a pair of substorm-associated electron precipitation eventsAbstractUsing ground-based subionospheric radio wave propagation data from two very low frequency (VLF) receiver sites, riometer absorption data, and THEMIS satellite observations, we examine in detail energetic electron precipitation (EEP) characteristics associated with two substorm precipitation events that occurred on 28 May 2010. In an advance on the analysis undertaken by Clilverd et al. (2008), we use phase observations of VLF radio wave signals to describe substorm-driven EEP characteristics more accurately than before. Using a >30 keV electron precipitation flux of 5.6 Ã— 107 el. cm -2 sr-1 s-1 and a spectral gradient consistent with that observed by THEMIS, it was possible to accurately reproduce the peak observed riometer absorption at Macquarie Island (L = 5.4) and the associated NWC radio wave phase change observed at Casey, Antarctica, during the second, larger substorm. The flux levels were near to 80% of the peak fluxes observed in a similar substorm as studied by Clilverd et al. (2008). During the initial stages of the second substorm, a latitude region of 5 < L < 9 was affected by electron precipitation. Both substorms showed expansion of the precipitation region to 4 < L < 12 more than 30min after the injection. While both substorms occurred at similar local times, with electron precipitation injections into approximately the same geographical region, the second expanded in an eastward longitude more slowly, suggesting the involvement of lower-energy electron precipitation. Each substorm region expanded westward at a rate slower than that exhibited eastward. This study shows that it is possible to successfully combine these multi-instrument observations to investigate the characteristics of substorms. Copyright 2012 by the American Geophysical Union.AcknowledgementsThe authors would like to acknowledge the support of the Australian Antarctic Division project ASAC 1324 for the Casey data and, in particular, the assistance of Ian Phillips. We would also like to acknowledge the use of the AAD data system for the provision of the Macquarie Island Riometer data (http://www.ips.gov.au/World_Data_Centre/1/8). The Scott Base experiment is supported by Antarctica New Zealand, event K060. We acknowledge NASA contract NAS5--02099 and V. Angelopoulos for the use of data from the THEMIS mission. Specifically, we thank D. Larson and R. P. Lin for use of the SST data. I.J.R. is funded by the Canadian Space Agency. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007--2013) under grant agreement 263218.

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1st AuthorClilverd, M.AuthorClilverd, M.Rodger, C.Rae, I.Brundell, J.Thomson, N.Cobbett, N.Verronen, P.Menk, F.Year2012JournalJournal of Geophysical Research: Space PhysicsVolume117Number2DOI10.1029/2011JA016933URLhttps://www.scopus.com/inward/recor.....a1191ba32bf7df81ba0fe3bbeKeywordsrank5

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TypeArticleCitationClilverd, M., Rodger, C., Rae, I., Brundell, J., Thomson, N., Cobbett, N., Verronen, P. and Menk, F. (2012). Combined THEMIS and ground-based observations of a pair of substorm-associated electron precipitation events. Journal of Geophysical Research: Space Physics, 117(2) IdentifierClilverd2012Relevancerank5