University of Oulu

Takahashi, T., Virtanen, I. I., Hosokawa, K., Ogawa, Y., Aikio, A., Miyaoka, H., & Kero, A. ( 2019). Polarization electric field inside auroral patches: Simultaneous experiment of EISCAT radars and KAIRA. Journal of Geophysical Research: Space Physics, 124, 3543– 3557.

Polarization electric field inside auroral patches : simultaneous experiment of EISCAT radars and KAIRA

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Author: Takahashi, Toru1; Virtanen, Ilkka I.2; Hosokawa, Keisuke3;
Organizations: 1National Institute of Polar Research, Tachikawa, Japan
2Ionospheric Physics Research Unit, University of Oulu, Oulu, Finland
3Department of Communication Engineering and Informatics, University of Electro-Communications, Chofu, Japan
4Department of Polar Science, SOKENDAI (The Graduate University for Advanced Studies), Tachikawa, Japan
5Sodankylä Geophysical Observatory, University of Oulu, Sodankylä, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.2 MB)
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Language: English
Published: American Geophysical Union, 2019
Publish Date: 2019-10-01


The primary focus of this study was the motion of auroral patches and the polarization electric field generated therein observed on 9 November 2015 in an experiment using the European incoherent scatter (EISCAT) radars, Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA), and an all‐sky imager simultaneously. Based on the all‐sky imager data, the drift speed of the auroral patches corresponded to a southward electric field of 14.1( ± 3.7)–17.2( ± 4.5) mV/m. The convective electric field derived from the EISCAT radars and KAIRA observation was approximately 14.6 mV/m in the southward direction. This suggest that the spatial distribution of the auroral patches reflects the distribution of the cold plasma in the magnetosphere. The electron density and the height‐integrated Hall conductance between 80 and 120 km were enhanced by a factor of 2–4 inside the auroral patches. In this situation, a polarization electric field was generated therein. Enhanced ion velocities due to the polarization electric field was observed at up to 200‐km altitude; however, the absolute values of the ion velocities were approximately 40% of what was expected from the polarization electric field. A field‐aligned current (FAC) from 5 to 10 μA/m−2 in the edges of the auroral patches could explain the weakening of the polarization electric field. Since a FAC of that order of magnitude corresponded with that observed by the Swarm satellite, it was suggested that the polarization electric field was weakened by the FAC. Furthermore, the polarization electric field propagated upward from the dynamo region to at least 200 km.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 124
Issue: 5
Pages: 3543 - 3557
DOI: 10.1029/2018JA026254
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: I. Virtanen is funded by the Academy of Finland, application 285474.
Academy of Finland Grant Number: 285474
Detailed Information: 285474 (Academy of Finland Funding decision)
Copyright information: © 2019. American Geophysical Union. All Rights Reserved.