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Timescales of dayside and nightside field-aligned current response to changes in solar wind-magnetosphere coupling

Timescales of dayside and nightside field-aligned current response to changes in solar wind-magnetosphere coupling
Timescales of dayside and nightside field-aligned current response to changes in solar wind-magnetosphere coupling

Principal component analysis is performed on Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, to determine the response of dayside and nightside FACs to reversals in the orientation of the interplanetary magnetic field (IMF) and the occurrence of substorms. Dayside FACs respond promptly to changes in IMF BY, but the nightside response is delayed by up to an hour and can take up to 4 hr to develop fully, especially during northward IMF. Nightside FAC asymmetries grow during substorm growth phase when the IMF has a significant BY component, and also promptly at substorm onset. Our findings suggest that magnetotail twisting and/or BY penetration into the magnetotail, due to subsolar reconnection with east-west orientated IMF, are the main cause of these nightside FAC asymmetries and that asymmetries also arise due to magnetotail reconnection of these twisted field lines.

currents, ionosphere, magnetosphere
2169-9380
Milan, Stephen E.
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Carter, Jennifer Alyson
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Sangha, Harneet
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Laundal, Karl M.
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Østgaard, Nikolai
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Tenfjord, Paul
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Reistad, Jone Peter
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Snekvik, Kristian
4feb166a-a899-4f19-b526-709c8301d1c9
Coxon, John C.
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Korth, Haje
47ef62e1-890c-46c6-8d1f-b715ba2b1cca
Anderson, Brian J.
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Milan, Stephen E.
b6dd5367-b0c4-4f30-953a-f2d13078d656
Carter, Jennifer Alyson
6af43c55-98c6-426f-840a-d2d90424bb75
Sangha, Harneet
52f78b89-54b7-4884-881d-f0823f8d1386
Laundal, Karl M.
66d28198-be7d-4c71-a9a9-a8324eef0fb1
Østgaard, Nikolai
2ebca733-ccc0-4ced-8d0a-b1b2c026cf6a
Tenfjord, Paul
22f4480d-a8ad-4e90-9511-372b0284d92e
Reistad, Jone Peter
d94d8c8f-0372-467b-a939-158394bf264b
Snekvik, Kristian
4feb166a-a899-4f19-b526-709c8301d1c9
Coxon, John C.
566baea5-6a30-4855-bde3-a09c115efde4
Korth, Haje
47ef62e1-890c-46c6-8d1f-b715ba2b1cca
Anderson, Brian J.
83afb235-d7a7-4c17-8151-f32fee334291

Milan, Stephen E., Carter, Jennifer Alyson, Sangha, Harneet, Laundal, Karl M., Østgaard, Nikolai, Tenfjord, Paul, Reistad, Jone Peter, Snekvik, Kristian, Coxon, John C., Korth, Haje and Anderson, Brian J. (2018) Timescales of dayside and nightside field-aligned current response to changes in solar wind-magnetosphere coupling. Journal of Geophysical Research: Space Physics. (doi:10.1029/2018JA025645).

Record type: Article

Abstract

Principal component analysis is performed on Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, to determine the response of dayside and nightside FACs to reversals in the orientation of the interplanetary magnetic field (IMF) and the occurrence of substorms. Dayside FACs respond promptly to changes in IMF BY, but the nightside response is delayed by up to an hour and can take up to 4 hr to develop fully, especially during northward IMF. Nightside FAC asymmetries grow during substorm growth phase when the IMF has a significant BY component, and also promptly at substorm onset. Our findings suggest that magnetotail twisting and/or BY penetration into the magnetotail, due to subsolar reconnection with east-west orientated IMF, are the main cause of these nightside FAC asymmetries and that asymmetries also arise due to magnetotail reconnection of these twisted field lines.

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Milan_et_al-2018-Journal_of_Geophysical_Research%3A_Space_Physics - Version of Record
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Accepted/In Press date: 14 July 2018
e-pub ahead of print date: 23 July 2018
Keywords: currents, ionosphere, magnetosphere

Identifiers

Local EPrints ID: 423283
URI: https://eprints.soton.ac.uk/id/eprint/423283
ISSN: 2169-9380
PURE UUID: b50fe72c-57a4-4d02-972f-534c304fdcba
ORCID for John C. Coxon: ORCID iD orcid.org/0000-0002-0166-6854

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Date deposited: 20 Sep 2018 16:30
Last modified: 10 Dec 2019 01:33

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Contributors

Author: Stephen E. Milan
Author: Jennifer Alyson Carter
Author: Harneet Sangha
Author: Karl M. Laundal
Author: Nikolai Østgaard
Author: Paul Tenfjord
Author: Jone Peter Reistad
Author: Kristian Snekvik
Author: John C. Coxon ORCID iD
Author: Haje Korth
Author: Brian J. Anderson

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