title: Increases in plasma sheet temperature with solar wind driving during substorm growth phases.
abstract: During substorm growth phases, magnetic reconnection at the magnetopause extracts ∼1015J 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 9 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 AL (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.
authors.affiliation: UCL Mullard Space Science Laboratory Dorking, UK.
authors.forename: C
authors.initials: C
authors.lastname: Forsyth
authors.affiliation: Department of Meteorology, University of Reading Reading, UK.
authors.forename: C E J
authors.initials: CE
authors.lastname: Watt
authors.affiliation: UCL Mullard Space Science Laboratory Dorking, UK.
authors.forename: I J
authors.initials: IJ
authors.lastname: Rae
authors.affiliation: UCL Mullard Space Science Laboratory Dorking, UK.
authors.forename: A N
authors.initials: AN
authors.lastname: Fazakerley
authors.affiliation: UCL Mullard Space Science Laboratory Dorking, UK.
authors.forename: N M E
authors.initials: NM
authors.lastname: Kalmoni
authors.affiliation: British Antarctic Survey Cambridge, UK.
authors.forename: M P
authors.initials: MP
authors.lastname: Freeman
authors.affiliation: Space Research Institute, Austrian Academy of Sciences Graz, Austria.
authors.forename: P D
authors.initials: PD
authors.lastname: Boakes
authors.affiliation: Space Research Institute, Austrian Academy of Sciences Graz, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Nakamura
authors.affiliation: Institut de Recherche en Astrophysique et Planétologie, University of Toulouse Toulouse, France ; CNRS, IRAP Toulouse, France.
authors.forename: I
authors.initials: I
authors.lastname: Dandouras
authors.affiliation: Space Science Centre, Morse Hall, University of New Hampshire Durham, New Hampshire, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Kistler
authors.affiliation: School of Physics & Astronomy, University of Southampton Southampton, UK.
authors.forename: C M
authors.initials: CM
authors.lastname: Jackman
authors.affiliation: Department Physics and Astronomy, University of Leicester Leicester, UK.
authors.forename: J C
authors.initials: JC
authors.lastname: Coxon
authors.affiliation: Department of Physics, Imperial College London London, UK.
authors.forename: C M
authors.initials: CM
authors.lastname: Carr
keywords: growth phase; plasma sheet; substorm; temperature