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Swarm Satellite and EISCAT Radar Observations of a Plasma Flow Channel in the Auroral Oval Near Magnetic Midnight
Univ Oulu, Ionospher Phys Unit, Oulu, Finland.
Kyushu Univ, Int Ctr Space Weather Sci & Educ, Fukuoka, Japan;Univ Oulu, Ionospher Phys Unit, Oulu, Finland.
Univ Oulu, Ionospher Phys Unit, Oulu, Finland.
Univ Oulu, Ionospher Phys Unit, Oulu, Finland.
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2018 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 6, p. 5140-5158Article in journal (Refereed) Published
Abstract [en]

We present Swarm satellite and EISCAT radar observations of electrodynamical parameters in the midnight sector at high latitudes. The most striking feature is a plasma flow channel located equatorward of the polar cap boundary within the dawn convection cell. The flow channel is 1.5 degrees wide in latitude and contains southward electric field of 150 mV/m, corresponding to eastward plasma velocities of 3,300 m/s in the F-region ionosphere. The theoretically computed ion temperature enhancement produced by the observed ion velocity is in accordance with the measured one by the EISCAT radar. The total width of the auroral oval is about 10 degrees in latitude. While the poleward part is electric field dominant with low conductivity and the flow channel, the equatorward part is conductivity dominant with at least five auroral arcs. The main part of the westward electrojet flows in the conductivity dominant part, but it extends to the electric field dominant part. According to Kamide and Kokubun (1996), the whole midnight sector westward electrojet is expected to be conductivity dominant, so the studied event challenges the traditional view. The flow channel is observed after substorm onset. We suggest that the observed flow channel, which is associated with a 13-kV horizontal potential difference, accommodates increased nightside plasma flows during the substorm expansion phase as a result of reconnection in the near-Earth magnetotail.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION , 2018. Vol. 123, no 6, p. 5140-5158
National Category
Fusion, Plasma and Space Physics
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URN: urn:nbn:se:uu:diva-362178DOI: 10.1029/2018JA025409ISI: 000439803100044OAI: oai:DiVA.org:uu-362178DiVA, id: diva2:1253346
Available from: 2018-10-04 Created: 2018-10-04 Last updated: 2018-10-04Bibliographically approved

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Buchert, Stephan

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