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Sources of local time asymmetries in magnetodiscs

Sources of local time asymmetries in magnetodiscs
Sources of local time asymmetries in magnetodiscs

The rapidly rotating magnetospheres at Jupiter and Saturn contain a near-equatorial thin current sheet over most local times known as the magnetodisc, resembling a wrapped-up magnetotail. The Pioneer, Voyager, Ulysses, Galileo, Cassini and New Horizons spacecraft at Jupiter and Saturn have provided extensive datasets from which to observationally identify local time asymmetries in these magnetodiscs. Imaging in the infrared and ultraviolet from ground- and space-based instruments have also revealed the presence of local time asymmetries in the aurora which therefore must map to local time asymmetries in the magnetosphere. Asymmetries are found in (i) the configuration of the magnetic field and magnetospheric currents, where a thicker disc is found in the noon and dusk sectors; (ii) plasma flows where the plasma flow has local time-dependent radial components; (iii) a thicker plasma sheet in the dusk sector. Many of these features are also reproduced in global MHD simulations. Several models have been developed to interpret these various observations and typically fall into two groups: ones which invoke coupling with the solar wind (via reconnection or viscous processes) and ones which invoke internal rotational processes operating inside an asymmetrical external boundary. In this paper we review these observational in situ findings, review the models which seek to explain them, and highlight open questions and directions for future work.

Current sheet, Jupiter, Kelvin–Helmholtz, Local time asymmetry, Magnetodisc, Plasma flows, Reconnection, Saturn, Solar wind interaction
0038-6308
301-333
Arridge, C. S.
cddea13c-2c2a-44c8-9607-309820a0fb0f
Kane, M.
74635e48-2e4f-49e0-995a-2a9aa7fce296
Sergis, N.
3b07fcbf-eb7f-496c-9b8d-c4f21fc9f87b
Khurana, K. K.
13e3a0d9-2a06-4bff-8a6a-7de9a4e304e2
Jackman, C. M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Arridge, C. S.
cddea13c-2c2a-44c8-9607-309820a0fb0f
Kane, M.
74635e48-2e4f-49e0-995a-2a9aa7fce296
Sergis, N.
3b07fcbf-eb7f-496c-9b8d-c4f21fc9f87b
Khurana, K. K.
13e3a0d9-2a06-4bff-8a6a-7de9a4e304e2
Jackman, C. M.
9bc3456c-b254-48f1-ade0-912c5b8b4529

Arridge, C. S., Kane, M., Sergis, N., Khurana, K. K. and Jackman, C. M. (2015) Sources of local time asymmetries in magnetodiscs. Space Science Reviews, 187 (1-4), 301-333. (doi:10.1007/s11214-015-0145-z).

Record type: Review

Abstract

The rapidly rotating magnetospheres at Jupiter and Saturn contain a near-equatorial thin current sheet over most local times known as the magnetodisc, resembling a wrapped-up magnetotail. The Pioneer, Voyager, Ulysses, Galileo, Cassini and New Horizons spacecraft at Jupiter and Saturn have provided extensive datasets from which to observationally identify local time asymmetries in these magnetodiscs. Imaging in the infrared and ultraviolet from ground- and space-based instruments have also revealed the presence of local time asymmetries in the aurora which therefore must map to local time asymmetries in the magnetosphere. Asymmetries are found in (i) the configuration of the magnetic field and magnetospheric currents, where a thicker disc is found in the noon and dusk sectors; (ii) plasma flows where the plasma flow has local time-dependent radial components; (iii) a thicker plasma sheet in the dusk sector. Many of these features are also reproduced in global MHD simulations. Several models have been developed to interpret these various observations and typically fall into two groups: ones which invoke coupling with the solar wind (via reconnection or viscous processes) and ones which invoke internal rotational processes operating inside an asymmetrical external boundary. In this paper we review these observational in situ findings, review the models which seek to explain them, and highlight open questions and directions for future work.

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More information

e-pub ahead of print date: 8 April 2015
Keywords: Current sheet, Jupiter, Kelvin–Helmholtz, Local time asymmetry, Magnetodisc, Plasma flows, Reconnection, Saturn, Solar wind interaction

Identifiers

Local EPrints ID: 436462
URI: http://eprints.soton.ac.uk/id/eprint/436462
ISSN: 0038-6308
PURE UUID: b980baac-0848-4943-b1ef-799d7f19331d
ORCID for C. M. Jackman: ORCID iD orcid.org/0000-0003-0635-7361

Catalogue record

Date deposited: 11 Dec 2019 17:30
Last modified: 07 Oct 2020 02:04

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Contributors

Author: C. S. Arridge
Author: M. Kane
Author: N. Sergis
Author: K. K. Khurana
Author: C. M. Jackman ORCID iD

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