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Plasma electrons in Saturn's magnetotail: structure, distribution and energisation

Plasma electrons in Saturn's magnetotail: structure, distribution and energisation
Plasma electrons in Saturn's magnetotail: structure, distribution and energisation

In this paper Saturn's nightside and pre-dawn electron (0.5 eV-28 keV) plasma sheet is studied using Cassini plasma electron and magnetic field data from 2006. Case studies are presented which exemplify the typical and atypical states of the plasma sheet, and are complemented by a statistical study of the plasma sheet. It will be shown that Saturn's nightside and pre-dawn electron plasma sheet exists in two states: a quiescent state with a steady electron temperature of ∼ 100 eV and where the electron distribution functions are best characterised by Kappa distributions, and a disturbed state where the electrons are hot (∼ 1 keV) and often seen in alternating layers between warm and hot populations. Evidence is also presented for bimodal cold/warm (both quiet and disturbed states) and warm/hot distributions (disturbed states). The disturbed states are qualitatively similar to electron distributions from Earth's magnetotail during intervals of reconnection and we argue that these disturbed states also result from periods of tail reconnection. We present statistics of electron number density, temperature, partial electron beta, and pressure, and show that large values of partial beta are necessary but not sufficient to uniquely identify the central plasma sheet. Finally the thermodynamic properties of the electron plasma sheet are studied and we show that the electrons behave isothermally. These results are important for modelling and theoretical analyses, and for use in studies which examine dynamics in Saturn's magnetosphere.

Cassini, Electrons, Magnetotail, Plasma sheet
0032-0633
2032-2047
Arridge, C.S.
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McAndrews, H.J.
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Jackman, C.M.
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Forsyth, C.
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Walsh, A.P.
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Sittler, E.C.
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Gilbert, L.K.
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Lewis, G.R.
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Russell, C.T.
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Coates, A.J.
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Dougherty, M.K.
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Collinson, G.A.
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Wellbrock, A.
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Young, D.T.
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Arridge, C.S.
2efb7acf-be5b-41b4-bade-8b4ff0d78236
McAndrews, H.J.
0e419a05-f21c-413e-9913-462fc341171b
Jackman, C.M.
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Forsyth, C.
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Walsh, A.P.
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Sittler, E.C.
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Gilbert, L.K.
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Lewis, G.R.
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Russell, C.T.
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Coates, A.J.
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Dougherty, M.K.
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Collinson, G.A.
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Wellbrock, A.
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Young, D.T.
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Arridge, C.S., McAndrews, H.J., Jackman, C.M., Forsyth, C., Walsh, A.P., Sittler, E.C., Gilbert, L.K., Lewis, G.R., Russell, C.T., Coates, A.J., Dougherty, M.K., Collinson, G.A., Wellbrock, A. and Young, D.T. (2009) Plasma electrons in Saturn's magnetotail: structure, distribution and energisation. Planetary and Space Science, 57 (14-15), 2032-2047. (doi:10.1016/j.pss.2009.09.007).

Record type: Article

Abstract

In this paper Saturn's nightside and pre-dawn electron (0.5 eV-28 keV) plasma sheet is studied using Cassini plasma electron and magnetic field data from 2006. Case studies are presented which exemplify the typical and atypical states of the plasma sheet, and are complemented by a statistical study of the plasma sheet. It will be shown that Saturn's nightside and pre-dawn electron plasma sheet exists in two states: a quiescent state with a steady electron temperature of ∼ 100 eV and where the electron distribution functions are best characterised by Kappa distributions, and a disturbed state where the electrons are hot (∼ 1 keV) and often seen in alternating layers between warm and hot populations. Evidence is also presented for bimodal cold/warm (both quiet and disturbed states) and warm/hot distributions (disturbed states). The disturbed states are qualitatively similar to electron distributions from Earth's magnetotail during intervals of reconnection and we argue that these disturbed states also result from periods of tail reconnection. We present statistics of electron number density, temperature, partial electron beta, and pressure, and show that large values of partial beta are necessary but not sufficient to uniquely identify the central plasma sheet. Finally the thermodynamic properties of the electron plasma sheet are studied and we show that the electrons behave isothermally. These results are important for modelling and theoretical analyses, and for use in studies which examine dynamics in Saturn's magnetosphere.

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More information

Published date: 1 December 2009
Keywords: Cassini, Electrons, Magnetotail, Plasma sheet

Identifiers

Local EPrints ID: 437318
URI: http://eprints.soton.ac.uk/id/eprint/437318
ISSN: 0032-0633
PURE UUID: d8f915a6-ec66-4b93-97b7-d88c55294360
ORCID for C.M. Jackman: ORCID iD orcid.org/0000-0003-0635-7361

Catalogue record

Date deposited: 24 Jan 2020 17:31
Last modified: 10 Nov 2021 03:35

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Contributors

Author: C.S. Arridge
Author: H.J. McAndrews
Author: C.M. Jackman ORCID iD
Author: C. Forsyth
Author: A.P. Walsh
Author: E.C. Sittler
Author: L.K. Gilbert
Author: G.R. Lewis
Author: C.T. Russell
Author: A.J. Coates
Author: M.K. Dougherty
Author: G.A. Collinson
Author: A. Wellbrock
Author: D.T. Young

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