The University of Southampton
University of Southampton Institutional Repository

Saturn's dynamic magnetotail: a comprehensive magnetic field and plasma survey of plasmoids and travelling compression regions, and their role in global magnetospheric dynamics

Saturn's dynamic magnetotail: a comprehensive magnetic field and plasma survey of plasmoids and travelling compression regions, and their role in global magnetospheric dynamics
Saturn's dynamic magnetotail: a comprehensive magnetic field and plasma survey of plasmoids and travelling compression regions, and their role in global magnetospheric dynamics
We present a comprehensive study of the magnetic field and plasma signatures of reconnection events observed with the Cassini spacecraft during the tail orbits of 2006. We examine their “local” properties in terms of magnetic field reconfiguration and changing plasma flows. We also describe the “global” impact of reconnection in terms of the contribution to mass loss, flux closure, and large-scale tail structure. The signatures of 69 plasmoids, 17 traveling compression regions (TCRs), and 13 planetward moving structures have been found. The direction of motion is inferred from the sign of the change in the B? component of the magnetic field in the first instance and confirmed through plasma flow data where available. The plasmoids are interpreted as detached structures, observed by the spacecraft tailward of the reconnection site, and the TCRs are interpreted as the effects of the draping and compression of lobe magnetic field lines around passing plasmoids. We focus on the analysis and interpretation of the tailward moving (south-to-north field change) plasmoids and TCRs in this work, considering the planetward moving signatures only from the point of view of understanding the reconnection x-line position and recurrence rates. We discuss the location spread of the observations, showing that where spacecraft coverage is symmetric about midnight, reconnection signatures are observed more frequently on the dawn flank than on the dusk flank. We show an example of a chain of two plasmoids and two TCRs over 3 hours and suggest that such a scenario is associated with a single-reconnection event, ejecting multiple successive plasmoids. Plasma data reveal that one of these plasmoids contains H+ at lower energy and W+ at higher energy, consistent with an inner magnetospheric source, and the total flow speed inside the plasmoid is estimated with an upper limit of 170?km/s. We probe the interior structure of plasmoids and find that the vast majority of examples at Saturn show a localized decrease in field magnitude as the spacecraft passes through the structure. We take the trajectory of Cassini into account, as, during 2006, the spacecraft's largely equatorial position beneath the hinged current sheet meant that it rarely traversed the center of plasmoids. We present an innovative method of optimizing the window size for minimum variance analysis (MVA) and apply this MVA across several plasmoids to explore their interior morphology in more detail, finding that Saturn's tail contains both loop-like and flux rope-like plasmoids. We estimate the mass lost downtail through reconnection and suggest that the apparent imbalance between mass input and observed plasmoid ejection may mean that alternative mass loss methods contribute to balancing Saturn's mass budget. We also estimate the rate of magnetic flux closure in the tail and find that when open field line closure is active, it plays a very significant role in flux cycling at Saturn.
2169-9380
5465-5494
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Slavin, J.A
cb44e43e-19fa-434a-b64f-22ed1acf0f46
Kivelson, M.G
4ae163e2-1ab4-4ae8-88ab-4744c65f9986
Southwood, J.
c60f3642-f65b-41d3-b6d2-8c31f9a1980b
Achilleos, N.
2d7c619e-cbb3-4956-9769-cc99d2021296
Thomsen, M.F.
81992bfc-27a7-42f3-9e36-571ce61228a6
DiBraccio, G.A.
0cff200a-51c0-48b6-bdfc-1ae5c6816e1d
Eastwood, J.P.
2ad075de-b753-4335-9e05-c8c73b4d1800
Freeman, M.P.
ca34cfc2-086e-4b43-9cb1-921ccbdadb10
Dougherty, M.K.
dfb81a1a-1b8d-4326-8416-5f66eb79e00a
Vogt, M.F.
2ac9a9d1-f7d2-4590-a3bd-533dddd3b568
Jackman, C.M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Slavin, J.A
cb44e43e-19fa-434a-b64f-22ed1acf0f46
Kivelson, M.G
4ae163e2-1ab4-4ae8-88ab-4744c65f9986
Southwood, J.
c60f3642-f65b-41d3-b6d2-8c31f9a1980b
Achilleos, N.
2d7c619e-cbb3-4956-9769-cc99d2021296
Thomsen, M.F.
81992bfc-27a7-42f3-9e36-571ce61228a6
DiBraccio, G.A.
0cff200a-51c0-48b6-bdfc-1ae5c6816e1d
Eastwood, J.P.
2ad075de-b753-4335-9e05-c8c73b4d1800
Freeman, M.P.
ca34cfc2-086e-4b43-9cb1-921ccbdadb10
Dougherty, M.K.
dfb81a1a-1b8d-4326-8416-5f66eb79e00a
Vogt, M.F.
2ac9a9d1-f7d2-4590-a3bd-533dddd3b568

Jackman, C.M., Slavin, J.A, Kivelson, M.G, Southwood, J., Achilleos, N., Thomsen, M.F., DiBraccio, G.A., Eastwood, J.P., Freeman, M.P., Dougherty, M.K. and Vogt, M.F. (2014) Saturn's dynamic magnetotail: a comprehensive magnetic field and plasma survey of plasmoids and travelling compression regions, and their role in global magnetospheric dynamics Journal of Geophysical Research: Space Physics, 119, (7), pp. 5465-5494.

Record type: Article

Abstract

We present a comprehensive study of the magnetic field and plasma signatures of reconnection events observed with the Cassini spacecraft during the tail orbits of 2006. We examine their “local” properties in terms of magnetic field reconfiguration and changing plasma flows. We also describe the “global” impact of reconnection in terms of the contribution to mass loss, flux closure, and large-scale tail structure. The signatures of 69 plasmoids, 17 traveling compression regions (TCRs), and 13 planetward moving structures have been found. The direction of motion is inferred from the sign of the change in the B? component of the magnetic field in the first instance and confirmed through plasma flow data where available. The plasmoids are interpreted as detached structures, observed by the spacecraft tailward of the reconnection site, and the TCRs are interpreted as the effects of the draping and compression of lobe magnetic field lines around passing plasmoids. We focus on the analysis and interpretation of the tailward moving (south-to-north field change) plasmoids and TCRs in this work, considering the planetward moving signatures only from the point of view of understanding the reconnection x-line position and recurrence rates. We discuss the location spread of the observations, showing that where spacecraft coverage is symmetric about midnight, reconnection signatures are observed more frequently on the dawn flank than on the dusk flank. We show an example of a chain of two plasmoids and two TCRs over 3 hours and suggest that such a scenario is associated with a single-reconnection event, ejecting multiple successive plasmoids. Plasma data reveal that one of these plasmoids contains H+ at lower energy and W+ at higher energy, consistent with an inner magnetospheric source, and the total flow speed inside the plasmoid is estimated with an upper limit of 170?km/s. We probe the interior structure of plasmoids and find that the vast majority of examples at Saturn show a localized decrease in field magnitude as the spacecraft passes through the structure. We take the trajectory of Cassini into account, as, during 2006, the spacecraft's largely equatorial position beneath the hinged current sheet meant that it rarely traversed the center of plasmoids. We present an innovative method of optimizing the window size for minimum variance analysis (MVA) and apply this MVA across several plasmoids to explore their interior morphology in more detail, finding that Saturn's tail contains both loop-like and flux rope-like plasmoids. We estimate the mass lost downtail through reconnection and suggest that the apparent imbalance between mass input and observed plasmoid ejection may mean that alternative mass loss methods contribute to balancing Saturn's mass budget. We also estimate the rate of magnetic flux closure in the tail and find that when open field line closure is active, it plays a very significant role in flux cycling at Saturn.

PDF __filestore.soton.ac.uk_users_jao1d15_mydocuments_ePrints_JACKMAN Saturn's dynamic magnetotail.pdf - Accepted Manuscript
Download (2MB)
PDF __filestore.soton.ac.uk_users_skr1c15_mydocuments_REF 2021_Outputs_Astro_Jackman_tail_2014_accepted.pdf - Accepted Manuscript
Download (2MB)

More information

Accepted/In Press date: 9 June 2014
Published date: 9 July 2014
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 401185
URI: http://eprints.soton.ac.uk/id/eprint/401185
ISSN: 2169-9380
PURE UUID: 28bebdf7-cdb1-4f61-984e-f9b339430c45

Catalogue record

Date deposited: 26 Oct 2016 15:56
Last modified: 20 Oct 2017 01:32

Export record

Contributors

Author: C.M. Jackman
Author: J.A Slavin
Author: M.G Kivelson
Author: J. Southwood
Author: N. Achilleos
Author: M.F. Thomsen
Author: G.A. DiBraccio
Author: J.P. Eastwood
Author: M.P. Freeman
Author: M.K. Dougherty
Author: M.F. Vogt

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×