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On the influence of open magnetic flux on substorm intensity: Ground- and space-based observations

On the influence of open magnetic flux on substorm intensity: Ground- and space-based observations
On the influence of open magnetic flux on substorm intensity: Ground- and space-based observations

Using the location of maximum region 1 current determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment as a proxy for the open/closed field line boundary, we monitor the evolution of the amount of open magnetic flux inside the magnetosphere during 772 substorms. We then divide all substorms into three classes, depending on the amount of open flux at expansion phase onset. Studying the temporal variations during the substorms of each class for a number of related geophysical parameters, we find that substorms occurring while the amount of open flux is large are generally more intense. By intense we mean that the auroral electrojet, region 1 current, auroral brightness, tail dipolarization and flow speed, ground magnetic signatures, Pi2 wave power, as well as the intensity and extent of the substorm current wedge (SCW) are all larger than during substorms that occur on a contracted polar cap. The SCW manifests itself as an intensification of the nightside R1 and R2 current system after onset. Our analysis shows that to dispose of large amounts of accumulated open magnetic flux, large substorms are triggered in the terrestrial magnetosphere. Key Points We monitor the amount of open magnetic flux during 772 substorms Depending on amount of open flux at onset we divide substorms into classes Substorms occurring while the amount of open flux is large are more intense

AMPERE, field-aligned currents, open/closed field line boundary, substorm current wedge, substorms
2169-9380
2958-2969
Clausen, L. B.N.
7ab01029-f55b-431b-911e-8e0f599ef534
Milan, S. E.
b6dd5367-b0c4-4f30-953a-f2d13078d656
Baker, J. B.H.
f658a185-799e-41d0-b192-b4eef55ff892
Ruohoniemi, J. M.
a6f2f18f-d6d5-4fa6-93a9-4114c212326d
Glassmeier, K. H.
0061e9bf-fd95-4535-81cd-479d7f3b8b4d
Coxon, J. C.
566baea5-6a30-4855-bde3-a09c115efde4
Anderson, B. J.
c30e4de5-7757-4c54-a05d-43369e879c0c
Clausen, L. B.N.
7ab01029-f55b-431b-911e-8e0f599ef534
Milan, S. E.
b6dd5367-b0c4-4f30-953a-f2d13078d656
Baker, J. B.H.
f658a185-799e-41d0-b192-b4eef55ff892
Ruohoniemi, J. M.
a6f2f18f-d6d5-4fa6-93a9-4114c212326d
Glassmeier, K. H.
0061e9bf-fd95-4535-81cd-479d7f3b8b4d
Coxon, J. C.
566baea5-6a30-4855-bde3-a09c115efde4
Anderson, B. J.
c30e4de5-7757-4c54-a05d-43369e879c0c

Clausen, L. B.N., Milan, S. E., Baker, J. B.H., Ruohoniemi, J. M., Glassmeier, K. H., Coxon, J. C. and Anderson, B. J. (2013) On the influence of open magnetic flux on substorm intensity: Ground- and space-based observations. Journal of Geophysical Research: Space Physics, 118 (6), 2958-2969. (doi:10.1002/jgra.50308).

Record type: Article

Abstract

Using the location of maximum region 1 current determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment as a proxy for the open/closed field line boundary, we monitor the evolution of the amount of open magnetic flux inside the magnetosphere during 772 substorms. We then divide all substorms into three classes, depending on the amount of open flux at expansion phase onset. Studying the temporal variations during the substorms of each class for a number of related geophysical parameters, we find that substorms occurring while the amount of open flux is large are generally more intense. By intense we mean that the auroral electrojet, region 1 current, auroral brightness, tail dipolarization and flow speed, ground magnetic signatures, Pi2 wave power, as well as the intensity and extent of the substorm current wedge (SCW) are all larger than during substorms that occur on a contracted polar cap. The SCW manifests itself as an intensification of the nightside R1 and R2 current system after onset. Our analysis shows that to dispose of large amounts of accumulated open magnetic flux, large substorms are triggered in the terrestrial magnetosphere. Key Points We monitor the amount of open magnetic flux during 772 substorms Depending on amount of open flux at onset we divide substorms into classes Substorms occurring while the amount of open flux is large are more intense

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More information

Accepted/In Press date: 29 April 2013
e-pub ahead of print date: 2 May 2013
Published date: June 2013
Keywords: AMPERE, field-aligned currents, open/closed field line boundary, substorm current wedge, substorms

Identifiers

Local EPrints ID: 430690
URI: http://eprints.soton.ac.uk/id/eprint/430690
ISSN: 2169-9380
PURE UUID: ccbbeefa-9ee2-4ac7-9c89-ed6724bd8598
ORCID for J. C. Coxon: ORCID iD orcid.org/0000-0002-0166-6854

Catalogue record

Date deposited: 08 May 2019 16:30
Last modified: 18 Feb 2021 17:24

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Contributors

Author: L. B.N. Clausen
Author: S. E. Milan
Author: J. B.H. Baker
Author: J. M. Ruohoniemi
Author: K. H. Glassmeier
Author: J. C. Coxon ORCID iD
Author: B. J. Anderson

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