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A superposed epoch analysis of the regions 1 and 2 Birkeland currents observed by AMPERE during substorms

A superposed epoch analysis of the regions 1 and 2 Birkeland currents observed by AMPERE during substorms
A superposed epoch analysis of the regions 1 and 2 Birkeland currents observed by AMPERE during substorms

We perform a superposed epoch analysis of the evolution of the Birkeland currents (field-aligned currents) observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during substorms. The study is composed of 2900 substorms provided by the SuperMAG experiment. We find that the current ovals expand and contract over the course of a substorm cycle and that currents increase in magnitude approaching substorm onset and are further enhanced in the expansion phase. Subsequently, we categorize the substorms by their onset latitude, a proxy for the amount of open magnetic flux in the magnetosphere, and find that Birkeland currents are significantly higher throughout the epoch for low-latitude substorms. Our results agree with previous studies which indicate that substorms are more intense and close more open magnetic flux when the amount of open flux is larger at onset. We place these findings in the context of previous work linking dayside and nightside reconnection rate to Birkeland current strengths and locations.

AMPERE, field-aligned currents, magnetic reconnection, open/closed field line boundary, substorm current wedge, substorms
2169-9380
9834-9846
Coxon, J. C.
566baea5-6a30-4855-bde3-a09c115efde4
Milan, S. E.
b6dd5367-b0c4-4f30-953a-f2d13078d656
Clausen, L. B.N.
7ab01029-f55b-431b-911e-8e0f599ef534
Anderson, B. J.
5300e507-80bf-4509-97e6-0d9cda5c93fb
Korth, H.
47ef62e1-890c-46c6-8d1f-b715ba2b1cca
Coxon, J. C.
566baea5-6a30-4855-bde3-a09c115efde4
Milan, S. E.
b6dd5367-b0c4-4f30-953a-f2d13078d656
Clausen, L. B.N.
7ab01029-f55b-431b-911e-8e0f599ef534
Anderson, B. J.
5300e507-80bf-4509-97e6-0d9cda5c93fb
Korth, H.
47ef62e1-890c-46c6-8d1f-b715ba2b1cca

Coxon, J. C., Milan, S. E., Clausen, L. B.N., Anderson, B. J. and Korth, H. (2014) A superposed epoch analysis of the regions 1 and 2 Birkeland currents observed by AMPERE during substorms. Journal of Geophysical Research: Space Physics, 119 (12), 9834-9846. (doi:10.1002/2014JA020500).

Record type: Article

Abstract

We perform a superposed epoch analysis of the evolution of the Birkeland currents (field-aligned currents) observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during substorms. The study is composed of 2900 substorms provided by the SuperMAG experiment. We find that the current ovals expand and contract over the course of a substorm cycle and that currents increase in magnitude approaching substorm onset and are further enhanced in the expansion phase. Subsequently, we categorize the substorms by their onset latitude, a proxy for the amount of open magnetic flux in the magnetosphere, and find that Birkeland currents are significantly higher throughout the epoch for low-latitude substorms. Our results agree with previous studies which indicate that substorms are more intense and close more open magnetic flux when the amount of open flux is larger at onset. We place these findings in the context of previous work linking dayside and nightside reconnection rate to Birkeland current strengths and locations.

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More information

Accepted/In Press date: 10 November 2014
e-pub ahead of print date: 17 November 2014
Published date: December 2014
Keywords: AMPERE, field-aligned currents, magnetic reconnection, open/closed field line boundary, substorm current wedge, substorms

Identifiers

Local EPrints ID: 430359
URI: https://eprints.soton.ac.uk/id/eprint/430359
ISSN: 2169-9380
PURE UUID: aed56fa6-5147-490c-a010-36351e0c0af5
ORCID for J. C. Coxon: ORCID iD orcid.org/0000-0002-0166-6854

Catalogue record

Date deposited: 26 Apr 2019 16:30
Last modified: 08 Nov 2019 01:31

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Contributors

Author: J. C. Coxon ORCID iD
Author: S. E. Milan
Author: L. B.N. Clausen
Author: B. J. Anderson
Author: H. Korth

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