University of Oulu

Oyama, S., Shinbori, A., Ogawa, Y., Kellinsalmi, M., Raita, T., Aikio, A., et al. (2020). An ephemeral red arc appeared at 68° MLat at a pseudo breakup during geomagnetically quiet conditions. Journal of Geophysical Research: Space Physics, 125, e2020JA028468.

An ephemeral red arc appeared at 68° MLat at a pseudo breakup during geomagnetically quiet conditions

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Author: Oyama, S.1,2,3; Shinbori, A.1; Ogawa, Y.3;
Organizations: 1Institute for Space‐Earth Environmental Research, Nagoya University, Nagoya, Japan
2Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland
3National Institute of Polar Research, Tachikawa, Japan
4Finnish Meteorological Institute, Helsinki, Finland
5Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
6Space and Plasma Physics, School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, Stockholm, Sweden
7Department of Computer and Network Engineering, The University of Electro‐Communications, Chofu, Japan
8Polar Geophysical Institute, Apatity, Russia
9Graduate School of Science, Tohoku University, Sendai, Japan
10Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
11Kyoto University, Kyoto, Japan
12Department of Space Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Japan
13Department of Physics and Astronomy, University of Leicester, Leicester, UK
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 8.1 MB)
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Language: English
Published: American Geophysical Union, 2020
Publish Date: 2021-04-03


Various subauroral optical features have been studied by analyzing data collected during periods of geomagnetic disturbances. Most events have been typically found at geomagnetic latitudes of 45–60°. In this study, however, we present a red arc event found at geomagnetic 68° north (L ≈ 7.1) in the Scandinavian sector during a period of geomagnetically quiet conditions within a short intermission between two high‐speed solar wind events. The red arc appeared to coincide with a pseudo breakup at geomagnetic 71–72°N and a rapid equatorward expansion of the polar cap. However, the red arc disappeared in approximately 7 min. Simultaneous measurements with the Swarm A/C satellites indicated the appearance of the red arc at the ionospheric trough minimum and a conspicuous enhancement of the electron temperature, suggesting the generation of the arc by heat flux. Since there are meaningful differences in the red arc features from already‐known subauroral optical features such as the stable auroral red (SAR) arc, we considered that the red arc is a new phenomenon. We suggest that the ephemeral red arc may represent the moment of SAR arc birth associated with substorm particle injection, which is generally masked by bright dynamic aurorae.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 125
Issue: 10
Article number: e2020JA028468
DOI: 10.1029/2020JA028468
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: Academy of Finland (Suomen Akatemia). Grant Number: 314664; MEXT | Japan Society for the Promotion of Science (JSPS). Grant Numbers: 16H06286, JPJSBP120194814, 15H05747; RCUK | Science and Technology Facilities Council (STFC). Grant Number: ST/S000429/1; Russian Foundation for Basic Research (RFBR). Grant Number: 19‐52‐50025; STFC. Grant Number: ST/S000429/1; RFBR. Grant Number: 19‐52‐50025; JSPS KAKENHI JP. Grant Numbers: AF314664, JPJSBP120194814, 16H02230, 15H05747, 16H06286; Canadian Space Agency; European Space Agency.
Academy of Finland Grant Number: 314664
Detailed Information: 314664 (Academy of Finland Funding decision)
Dataset Reference: Data Availability Statement: All‐sky camera images at Abisko, Kilpisjärvi, Longyearbyen, and Lovozero were obtained from individual PIs (Sodankylä Geophysical Observatory, Finland; Finnish Meteorological Institute, Finland; National Institute of Polar Research, Japan; and Polar Geophysical Institute, Russia) after checking the quick looks at their websites (,, SuperDARN map potential data were obtained from its website (‐index.php?page=ASCIIData). The DMSP SSUSI, Swarm, and ACE data were obtained through their websites (‐aur_cs, swarm‐, The MMS quick looks were obtained through their websites ( Access and processing data of the solar wind and geomagnetic indices were obtained using SPEDAS V3.0 through Science data of the ERG (Arase) satellite were obtained from the ERG Science Center operated by ISAS/JAXA and ISEE/Nagoya University (‐, Miyoshi, Hori, et al., 2018). The present study analyzed PWE‐HFA L2 v01_01, MGF‐L2 v03_03 data, and OBT L3 v02 data.
Copyright information: © 2020. American Geophysical Union.