2026-05-21 北海道大学,沖縄科学技術大学院大学
2024年8月4日にオーロラの観測が行われた地点（a）と、北海道の複数の地点で撮影された低緯度オーロラの写真（b）～（d）。
撮影：（b）田村幸基氏、（c）嘉藤哲志氏、（d）植松 薫氏
＜関連情報＞
- https://www.hokudai.ac.jp/news/2026/05/content-32.html
- https://www.swsc-journal.org/articles/swsc/full_html/2026/01/swsc250047/swsc250047.html
日本で見られたかすかな赤いオーロラは強い磁気圏圧縮と関連している Faint red auroras as seen from Japan associated with intense magnetospheric compression
Tomohiro M. Nakayama and Ryuho Kataoka
Journal of Space Weather and Space Climate Published:19 May 2026
DOI:https://doi.org/10.1051/swsc/2026004
Abstract
We report four low-latitude auroral events in 2024 as observed from Hokkaido, Japan (June 28, August 4, September 12, and November 9). These auroral events occurred during moderately intense magnetic storms, with the peak Dst index of approximately −110 nT, accompanied by significant magnetospheric compression. We estimate the altitudes of these red auroras to be > ~500 km, via widespread citizen science efforts. During the red aurora appearances in Japan, the ASYM-H index increased significantly to around 150 nT, which was approximately 1.3–2.0 times larger than the SYM-H peak amplitude for all events, suggesting that the actual storm intensities were underestimated. We further propose that the very dense solar wind of >~30 /cc is a key for causing the majority of extended red auroras during moderately intense magnetic storms, possibly via the stronger-than-usual enhancement of the atmospheric Joule heat in the subauroral latitude.
