According to Kyoto University, the research group compared the aurora borealis left in historical literature such as Meigetsuki and the Chinese history book "Song History" with the carbon isotope ratios of tree rings, and giant magnetic storms from the 7th to 13th centuries. The occurrence pattern was clarified.

　On February 1204st and 2rd, 21, redness was seen in Kyoto, and it was written that "it looks like a fire over the mountains and is scary."When the research group investigated that there was a solar flare (* 23), an observation record of a huge sunspot showing active solar activity was found in the record of the same day in Song history.

　Furthermore, as a result of investigating past changes in geomagnetism, it was found that it was almost impossible to see the aurora in present-day Kyoto, but it was in a condition where the aurora could be observed at the beginning of the 13th century.

　Comparing the aurora observation records of Song history with the periodic changes in solar activity remaining in annual rings such as Yakusugi, the aurora was observed during the maximum period of solar activity, but in the first half of the 11th century when the solar activity weakened. Was never mentioned.

　When a solar flare occurs, high-energy particles reach the earth and cause a magnetic storm, and aurora is observed in high latitude areas.There are concerns about artificial satellite failures and large-scale power outages due to the effects of huge magnetic storms.Research results are likely to help predict long-term changes in solar activity and giant geomagnetic storms.

* 1 Solar flare Large-scale explosion on the surface of the sun

Paper information:[Space Weather] Historical space weather monitoring of prolonged aurora activities in Japan and in China