3:30 PM - 3:45 PM
[MZZ43-06] Characteristics of low-latitude auroras observed in Japan by Nagoya University
Keywords:low-latitude aurora, geomagnetic storm, solar activity, substorm
The Institute for Space-Earth Environmental Research, Nagoya University has observed 37 low-latitude auroras since 1989 using optical instruments. These observations were made at the Moshiri Observatory (44.37N, 142.27E, MLAT=35.6) and the Rikubetsu Observatory (43.46N, 143.77E, MLAT=34.7), in Hokkaido, Japan. Since 1998, another routine measurement has been carried out at the Shigaraki MU Observatory, Kyoto University (34.85N, 136.11E, MLAT=25.4), Japan. Particularly the glowing solar activity in cycle 25 has been causing 11 low latitude auroras in Japan in 2023-2025. This number is much larger than that in the previous cycle 24 (only two times in 2009-2020). These low-latitude auroras were characterized by red emission at a wavelength of 630.0 nm. Some auroral events are also accompanied by green (557.7 nm) and faint blue (427.8 nm) emissions. Their appearance has long time scales of more than a few hours, while hourly-scale brightening and motion were also observed associated with the occurrence of magnetospheric substorm. In the presentation, we will summarize the characteristics of these low-latitude auroras measured by optical instruments and compare them with historical records of red emissions “Sekki” or “Kouki” in Japanese historical literatures.