TY - JOUR

T1 - Sources of local time asymmetries in magnetodiscs

AU - Arridge, C. S.

AU - Kane, M.

AU - Sergis, N.

AU - Khurana, K. K.

AU - Jackman, C. M.

N1 - Date of Acceptance: 11/03/2015

PY - 2015/4

Y1 - 2015/4

N2 - The rapidly rotating magnetospheres at Jupiter and Saturn contain a nearequatorial 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.

AB - The rapidly rotating magnetospheres at Jupiter and Saturn contain a nearequatorial 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.

KW - Saturn

KW - Jupiter

KW - Magnetodisc

KW - Local time asymmetry

KW - Plasma flows

KW - Current sheet

KW - Solar wind interaction

KW - Reconnection

KW - Kelvin-Helmholtz

KW - SATURNS INNER MAGNETOSPHERE

KW - JOVIAN MAGNETOSPHERE

KW - JUPITERS MAGNETOSPHERE

KW - MAGNETIC-FIELD

KW - ELECTRIC-FIELD

KW - SOLAR-WIND

KW - EQUATORIAL CURRENT

KW - CURRENT SHEET

KW - RING CURRENT

KW - FLOWS

U2 - 10.1007/s11214-015-0145-z

DO - 10.1007/s11214-015-0145-z

M3 - Literature review

VL - 187

SP - 301

EP - 333

JO - Space Science Reviews

JF - Space Science Reviews

SN - 0038-6308

IS - 1-4

ER -