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Auroral counterpart of magnetic field dipolarizations in Saturn's tail

Auroral counterpart of magnetic field dipolarizations in Saturn's tail
Auroral counterpart of magnetic field dipolarizations in Saturn's tail

Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations are initially identified in magnetometer data by looking for a southward turning of the magnetic field, indicating the transition from a radially stretched configuration to a more dipolar field topology. The highly stretched geometry of the kronian magnetotail lobes gives rise to a tail current which flows eastward (dusk to dawn) in the near equatorial plane across the centre of the tail. During reconnection and associated dipolarization of the field, the inner edge of this tail current can be diverted through the ionosphere, in a situation analogous to the substorm current wedge picture at Earth. We present a picture of the current circuit arising from this tail reconfiguration, and outline the equations which describe the field-current relationship. We show a new in situ example of a dipolarization identified in the Cassini magnetometer data and use this formalism to estimate the ionospheric current density that would arise based on in situ tail measurements of the magnetic field and the implications for corresponding auroral electron acceleration in regions of upward directed field-aligned current. We then present a separate example of data from the Cassini UVIS instrument where we observe small 'spots' of auroral emission lying near the main oval; features suggested to be associated with dipolarizations in the tail. In the example shown, such auroral features are the precursor to more intense activity associated with recurrent energisation via particle injections from the tail following reconnection.

Aurora, Dipolarization, Saturn
0032-0633
34-42
Jackman, Caitriona M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Achilleos, Nick
620cd146-20a4-4a84-8fd9-2a3e5d95aa2a
Cowley, Stanley W.H.
e8174910-ddcd-4a23-9d7c-0e1117def06c
Bunce, Emma J.
208e1177-a92f-47a6-878d-ef27ed03f811
Radioti, Aikaterini
b5b07317-c465-4a9b-9a81-630ae5287c1b
Grodent, Denis
9f63c3db-559c-49b9-b9ad-28b0168a8443
Badman, Sarah V.
d5bc36ea-0df0-49e9-b367-8db1f9a95e11
Dougherty, Michele K.
aa297043-7e86-4501-952b-a6363edaaba8
Pryor, Wayne
c4fb9038-5469-4233-8d55-5518cd16ffe3
Jackman, Caitriona M.
9bc3456c-b254-48f1-ade0-912c5b8b4529
Achilleos, Nick
620cd146-20a4-4a84-8fd9-2a3e5d95aa2a
Cowley, Stanley W.H.
e8174910-ddcd-4a23-9d7c-0e1117def06c
Bunce, Emma J.
208e1177-a92f-47a6-878d-ef27ed03f811
Radioti, Aikaterini
b5b07317-c465-4a9b-9a81-630ae5287c1b
Grodent, Denis
9f63c3db-559c-49b9-b9ad-28b0168a8443
Badman, Sarah V.
d5bc36ea-0df0-49e9-b367-8db1f9a95e11
Dougherty, Michele K.
aa297043-7e86-4501-952b-a6363edaaba8
Pryor, Wayne
c4fb9038-5469-4233-8d55-5518cd16ffe3

Jackman, Caitriona M., Achilleos, Nick, Cowley, Stanley W.H., Bunce, Emma J., Radioti, Aikaterini, Grodent, Denis, Badman, Sarah V., Dougherty, Michele K. and Pryor, Wayne (2013) Auroral counterpart of magnetic field dipolarizations in Saturn's tail. Planetary and Space Science, 82-83, 34-42. (doi:10.1016/j.pss.2013.03.010).

Record type: Article

Abstract

Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations are initially identified in magnetometer data by looking for a southward turning of the magnetic field, indicating the transition from a radially stretched configuration to a more dipolar field topology. The highly stretched geometry of the kronian magnetotail lobes gives rise to a tail current which flows eastward (dusk to dawn) in the near equatorial plane across the centre of the tail. During reconnection and associated dipolarization of the field, the inner edge of this tail current can be diverted through the ionosphere, in a situation analogous to the substorm current wedge picture at Earth. We present a picture of the current circuit arising from this tail reconfiguration, and outline the equations which describe the field-current relationship. We show a new in situ example of a dipolarization identified in the Cassini magnetometer data and use this formalism to estimate the ionospheric current density that would arise based on in situ tail measurements of the magnetic field and the implications for corresponding auroral electron acceleration in regions of upward directed field-aligned current. We then present a separate example of data from the Cassini UVIS instrument where we observe small 'spots' of auroral emission lying near the main oval; features suggested to be associated with dipolarizations in the tail. In the example shown, such auroral features are the precursor to more intense activity associated with recurrent energisation via particle injections from the tail following reconnection.

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More information

e-pub ahead of print date: 3 April 2013
Published date: July 2013
Keywords: Aurora, Dipolarization, Saturn

Identifiers

Local EPrints ID: 437306
URI: http://eprints.soton.ac.uk/id/eprint/437306
ISSN: 0032-0633
PURE UUID: 27dda409-ddf5-497b-b229-5e0275ffd661
ORCID for Caitriona M. Jackman: ORCID iD orcid.org/0000-0003-0635-7361

Catalogue record

Date deposited: 24 Jan 2020 17:30
Last modified: 10 Nov 2021 03:35

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Contributors

Author: Nick Achilleos
Author: Stanley W.H. Cowley
Author: Emma J. Bunce
Author: Aikaterini Radioti
Author: Denis Grodent
Author: Sarah V. Badman
Author: Michele K. Dougherty
Author: Wayne Pryor

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