2024-03-28T10:58:14Z
https://nagoya.repo.nii.ac.jp/oai
oai:nagoya.repo.nii.ac.jp:00022995
2023-01-16T04:45:34Z
879:880:881
Stepwise tailward retreat ofmagnetic reconnection: THEMIS observations of an auroral substorm
Ieda, A.
Nishimura, Y.
Miyashita, Y.
Angelopoulos, V.
Runov, A.
Nagai, T.
Frey, H. U.
Fairfield, D. H.
Slavin, A.
Vanhamäki, H.
Uchino, H.
open access
© 2016 American Geophysical Union
Auroral stepwise poleward expansions were clarified by investigating a multiple-onset substorm that occurred on 27 February 2009. Five successive auroral brightenings were identified in all-sky images, occurring at approximately 10 min intervals. The first brightening was a faint precursor. The second brightening had a wide longitude; thus, it represented the Akasofu substorm onset. Other brightenings expanded poleward; thus, they were interpreted to be auroral breakups. These breakups occurred stepwise; that is, later breakups were initiated at higher latitudes. Corresponding reconnection signatures were studied using Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellite observations between 8 and 24 RE down the magnetotail. The Akasofu substorm onset was not accompanied by a clear reconnection signature in the tail. In contrast, the three subsequent auroral breakups occurred simultaneously (within a few minutes) with three successive fast flows at 24 RE; thus, these were interpreted to be associated with impulsive reconnection episodes. These three fast flows consisted of a tailward flow and two subsequent earthward flows. The flow reversal at the second breakup indicated that a tailward retreat of the near-Earth reconnection site occurred during the substorm expansion phase. In addition, the earthward flow at the third breakup was consistent with the classic tailward retreat near the end of the expansion phase; therefore, the tailward retreat is likely to have occurred in a stepwise manner. We interpreted the stepwise characteristics of the tailward retreat and poleward expansion to be potentially associated by a stepwise magnetic flux pileup.
Wiley
2016-05-28
eng
journal article
VoR
http://hdl.handle.net/2237/25179
https://nagoya.repo.nii.ac.jp/records/22995
https://doi.org/10.1002/2015JA022244
2169-9402
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
121
5
4548
4568
https://nagoya.repo.nii.ac.jp/record/22995/files/Ieda_et_al-2016-Journal_of_Geophysical_Research_Space_Physics.pdf
application/pdf
7.6 MB
2018-02-22