Solar activity fluctuates not only in the well-known 11-year cycle, but also in long cycles such as 1000 and 2000, and the Earth's climate also fluctuates in good agreement with such long-period fluctuations in solar activity. I know I've done it.However, the effects of solar activity at meteorological levels are only fragmented.

　The shortest cycle of solar activity is the 27-day cycle due to rotation.Due to the effect of rotation, the amount of light reaching the earth and the amount of cosmic radiation change every 27 days.Focusing on this, this research group investigated the relationship between meteorology, especially lightning, and solar activity in Japan.

　Two documents from the Edo period, "Hirozen Clan Office Diary" and "Ishikawa Diary", were used for the survey.The records of lightning were extracted from these, and the dates of lightning occurrence in Hirosaki, Hachioji, and Edo for about 17 years from the latter half of the 19th century to the middle of the 200th century were investigated.As a result, it was confirmed that the 27-day cycle tends to appear more strongly in the occurrence of lightning in the years when the solar activity was active.This strongly suggests that the rotation of the sun also has an important effect on the meteorological scale.

　Although many correlations between solar activity and climate change have been found, this study shows that solar activity does have an effect on meteorological levels as well.In the future, it is expected that elucidating the mechanism by which solar activity affects the occurrence of lightning will improve the accuracy of climate prediction and provide clues for long-term weather prediction.

Paper information:[Annales Geophysicae] Solar rotational cycle in lightning activity in Japan during the 18–19th centuries