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Increases in plasma sheet temperature with solar wind driving during substorm growth phases

Forsyth, C.; Watt, C.E.J.; Rae, I.J.; Fazakerley, A.N.; Kalmoni, N.M.E.; Freeman, M.P.; Boakes, P.D.; Nakamura, R.; Dandouras, I.; Kistler, L.M.; Jackman, C.M.; Coxon, J.C.; Carr, C.. 2014 Increases in plasma sheet temperature with solar wind driving during substorm growth phases. Geophysical Research Letters, 41 (24). 8713-8721. 10.1002/2014GL062400

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Abstract/Summary

During substorm growth phases, magnetic reconnection at the magnetopause extracts ~1015 J from the solar wind which is then stored in the magnetotail lobes. Plasma sheet pressure increases to balance magnetic flux density increases in the lobes. Here, we examine plasma sheet pressure, density and temperature during substorm growth phases using nine years of Cluster data (>316,000 data points). We show that plasma sheet pressure and temperature are higher during growth phases with higher solar wind driving whereas the density is approximately constant. We also show a weak correlation between plasma sheet temperature before onset and the minimum SuperMAG SML auroral index in the subsequent substorm. We discuss how energization of the plasma sheet before onset may result from thermodynamically adiabatic processes; how hotter plasma sheets may result in magnetotail instabilities and how this relates to the onset and size of the subsequent substorm expansion phase.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1002/2014GL062400
Programmes: BAS Programmes > Polar Science for Planet Earth (2009 - ) > Climate
ISSN: 00948276
Additional Keywords: substorm, growth phase, plasma sheet, temperature
Date made live: 08 Dec 2014 09:18 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/509005

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