University of Oulu

Aikio, A. T., Vanhamäki, H., Workayehu, A. B., Virtanen, I. I., Kauristie, K., Juusola, L., et al. (2018). Swarm satellite and EISCAT radar observations of a plasma flow channel in the auroral oval near magnetic midnight. Journal of Geophysical Research: Space Physics, 123, 5140–5158.

Swarm satellite and EISCAT radar observations of a plasma flow channel in the auroral oval near magnetic midnight

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Author: Aikio, A. T.1; Vanhamäki, H.1,2; Workayehu, A. B.1;
Organizations: 1Ionospheric Physics Unit, University of Oulu, Oulu, Finland
2International Center for Space Weather Science and Education, Kyushu University, Fukuoka, Japan
3Finnish Meteorological Institute, Helsinki, Finland
4Swedish Institute of Space Physics, Uppsala, Sweden
5Department of Physics and Astronomy, University of Calgary, Calgary, Alberta, Canada
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.3 MB)
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Language: English
Published: American Geophysical Union, 2018
Publish Date: 2019-02-21


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° 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° 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.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 123
Issue: 6
Pages: 5140 - 5158
DOI: 10.1029/2018JA025409
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
114 Physical sciences
Funding: This work was supported by the Academy of Finland project 285474.
Academy of Finland Grant Number: 285474
Detailed Information: 285474 (Academy of Finland Funding decision)
Copyright information: © 2018. American Geophysical Union. All Rights Reserved.