University of Oulu

Hosokawa, K., Miyoshi, Y., Oyama, S.-I., Ogawa, Y., Kurita, S., Kasahara, Y., et al. (2021). Over-darkening of pulsating aurora. Journal of Geophysical Research: Space Physics, 126, e2020JA028838.

Over-darkening of pulsating aurora

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Author: Hosokawa, K.1; Miyoshi, Y.2; Oyama, S.-I.2,3,4;
Organizations: 1Graduate School of Communication Engineering and Informatics, University of Electro- Communications, Chofu, Tokyo, Japan
2Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Aichi, Japan
3National Institute of Polar Research, Tachikawa, Tokyo, Japan
4University of Oulu, Oulu, Finland
5Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto, Japan
6Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa, Japan
7Department of Geophysics, Graduate School of Science, Tohoku University, Sendai, Miyagi, Japan
8Institute of Space and Astronautical Science, Sagamihara, Kanagawa, Japan
9Research Organization of Information and Systems, Minato-ku, Tokyo, Japan
Format: article
Version: published version
Access: embargoed
Persistent link:
Language: English
Published: American Geophysical Union, 2021
Publish Date: 2021-09-28


Recent analyses of high-time resolution ground-based optical observations of pulsating aurora (PsA) have reported that the brightness of PsA sometimes decreases below the diffuse background level immediately after the ON phase of the main pulsation finishes. To date, however, the generation mechanism of such an “over-darkening PsA” is still unclarified. In this study, we investigated the characteristics of the over-darkening PsA by using simultaneous observations of PsA with an electron multiplying charge coupled device all-sky camera in Sodankylä, Finland and the Arase satellite. During one of the conjunction events in Scandinavia on March 29, 2017, almost all the PsA pulses showed clear over-darkening characteristics. By analyzing the 2D all-sky images at the times of over-darkening we discovered that over-darkening areas appeared in the trailing edge of PsA patches and moved in tandem with the poleward propagating patches. It was also found that similar over-decreasing characteristics were not seen in the chorus data from the wave instruments onboard Arase located at the magnetospheric counterpart of PsA. These results indicate that the over-darkening PsA is not caused by a temporal variation of chorus at a fixed point, but is produced by a propagation of over-darkening area with PsA patches. That is, the over-darkening PsA is a result of compounding effects of spatial structure and recurrent propagation of PsA. The mechanism creating the dark area is still unknown, but the existence of over-darkening PsA suggests that the temporal variation of PsA is not always a perfect copy of the modulation of lower-band chorus waves in the magnetosphere.

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Series: Journal of geophysical research. Space physics
ISSN: 2169-9380
ISSN-E: 2169-9402
ISSN-L: 2169-9380
Volume: 126
Issue: 4
Article number: e2020JA028838
DOI: 10.1029/2020JA028838
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: K. Hosokawa, Y. Miyoshi, S.-I. Oyama, Y. Ogawa, and R. Fujii are supported by JSPS Kakenhi (15H05747). Y. Miyoshi, S.-I. Oyama, S. Kurita and M. Ozaki are supported by JSPS Kakenhi (16H06286). K. Hosokawa, Y. Miyoshi, and S. Kurita are supported by the International Space Science Institutes Beijing (ISSI-BJ) International Team program. Y. Miyoshi, Y. Kasaba, S. Kurita, K.S., and Y. Kasahara are supported by JSPS Bilateral Open Partnership Joint Research Projects. Y. Kasahara is supported by JSPS Kakenhi (16H04056 and 16H01172). The operation of the EMCCD camera at Sodankylä has been supported by the Sodankylä Geophysical Observatory (SGO).
Copyright information: © 2021. American Geophysical Union.