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Subsidence of ionospheric flows triggered by magnetotail magnetic reconnection during transpolar arc brightening

Subsidence of ionospheric flows triggered by magnetotail magnetic reconnection during transpolar arc brightening
Subsidence of ionospheric flows triggered by magnetotail magnetic reconnection during transpolar arc brightening

A transpolar arc (TPA), which extended from postmidnight to prenoon, was seen on 16 September 2001 in the Northern Hemisphere under northward interplanetary magnetic field (IMF)-Bz and weakly dawnward IMF-By conditions. Super Dual Auroral Radar Network detected significant westward plasma flows just equatorward of the poleward edge of the midnight sector auroral oval. These plasma flows were confined to closed field lines and are identified as the ionospheric plasma flow signature of tail reconnection during IMF northward nonsubstorm intervals (TRINNIs). These TRINNI flows persisted for 53 min from prior to the TPA appearance to the cessation of TPA growth. They are usually observed before (and during) intervals when TPAs are present, but in this case, subsided after the TPA was completely connected to the dayside. Additional slower flows across the open/closed polar cap boundary were seen at the TPA onset time in the same magnetic local time sector as the nightside end of the TPA. These ionospheric flows suggest that magnetotail reconnection significantly contributed to the TPA formation, as proposed by Milan et al. (, https://doi.org/10.1029/2004JA010835). We propose a possible scenario for an absence of the TRINNI flows during the TPA brightening by considering the relation between the extent of the magnetotail reconnection line mapped onto nightside auroral oval and the TPA width; TRINNI flows would subside when the extent of X-line is comparable to the TPA width. Therefore, our results suggest that the fate (absence or presence) of TRINNI flows on closed field lines during the TPA formation would be closely related with magnetotail reconnection extent.

Ionospheric plasma flows, Lobe and magnetotail magnetic reconnections, Transpolar arc and its formation, TRINNIs
2169-9380
Nowada, Motoharu
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Fear, Robert C.
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Grocott, Adrian
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Shi, Quan Qi
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Yang, Jun
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Zong, Qiu Gang
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Wei, Yong
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Fu, Sui Yan
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Pu, Zu Yin
25b161dd-b3eb-4473-a842-6191f8c053fb
Mailyan, Bagrat
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Zhang, Hui
1e37a974-1ead-4938-ae86-40ef96de017a
Nowada, Motoharu
5ba75635-ad9f-4284-839e-fbf87b9297d3
Fear, Robert C.
8755b9ed-c7dc-4cbb-ac9b-56235a0431ab
Grocott, Adrian
98713ad4-7780-4a81-9131-3c64c2723101
Shi, Quan Qi
cdbcdf30-df5a-49c3-a2bd-758ec558943a
Yang, Jun
5828a5b9-7410-424f-b546-02d8588393e9
Zong, Qiu Gang
577b373c-6a5d-4d4a-81f9-1b06a2650087
Wei, Yong
a5268e79-6f7f-414b-a99c-168a80780aec
Fu, Sui Yan
39482b10-92e8-4052-8f2b-65afd14a9fd9
Pu, Zu Yin
25b161dd-b3eb-4473-a842-6191f8c053fb
Mailyan, Bagrat
322e04f8-115a-4cf1-8e69-5184831cfb29
Zhang, Hui
1e37a974-1ead-4938-ae86-40ef96de017a

Nowada, Motoharu, Fear, Robert C., Grocott, Adrian, Shi, Quan Qi, Yang, Jun, Zong, Qiu Gang, Wei, Yong, Fu, Sui Yan, Pu, Zu Yin, Mailyan, Bagrat and Zhang, Hui (2018) Subsidence of ionospheric flows triggered by magnetotail magnetic reconnection during transpolar arc brightening. Journal of Geophysical Research: Space Physics. (doi:10.1029/2017JA024701).

Record type: Article

Abstract

A transpolar arc (TPA), which extended from postmidnight to prenoon, was seen on 16 September 2001 in the Northern Hemisphere under northward interplanetary magnetic field (IMF)-Bz and weakly dawnward IMF-By conditions. Super Dual Auroral Radar Network detected significant westward plasma flows just equatorward of the poleward edge of the midnight sector auroral oval. These plasma flows were confined to closed field lines and are identified as the ionospheric plasma flow signature of tail reconnection during IMF northward nonsubstorm intervals (TRINNIs). These TRINNI flows persisted for 53 min from prior to the TPA appearance to the cessation of TPA growth. They are usually observed before (and during) intervals when TPAs are present, but in this case, subsided after the TPA was completely connected to the dayside. Additional slower flows across the open/closed polar cap boundary were seen at the TPA onset time in the same magnetic local time sector as the nightside end of the TPA. These ionospheric flows suggest that magnetotail reconnection significantly contributed to the TPA formation, as proposed by Milan et al. (, https://doi.org/10.1029/2004JA010835). We propose a possible scenario for an absence of the TRINNI flows during the TPA brightening by considering the relation between the extent of the magnetotail reconnection line mapped onto nightside auroral oval and the TPA width; TRINNI flows would subside when the extent of X-line is comparable to the TPA width. Therefore, our results suggest that the fate (absence or presence) of TRINNI flows on closed field lines during the TPA formation would be closely related with magnetotail reconnection extent.

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Nowada_et_al-2017-Journal_of_Geophysical_Research__Space_Physics - Version of Record
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Accepted/In Press date: 6 April 2018
e-pub ahead of print date: 19 April 2018
Keywords: Ionospheric plasma flows, Lobe and magnetotail magnetic reconnections, Transpolar arc and its formation, TRINNIs

Identifiers

Local EPrints ID: 420722
URI: https://eprints.soton.ac.uk/id/eprint/420722
ISSN: 2169-9380
PURE UUID: bd4fad4b-dfc1-4a0a-b624-7f3b9d588e52
ORCID for Robert C. Fear: ORCID iD orcid.org/0000-0003-0589-7147

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Date deposited: 14 May 2018 16:30
Last modified: 20 Jul 2019 00:37

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