[P-EM08_1PM2] Space Weather and Space Climate

[PEM08-06] 日本産樹木中14C濃度測定による過去5000年間の大SPE探索計画

*三宅 芙沙¹、増田 公明¹、箱崎 真隆²、中村 俊夫²、木村 勝彦³ (1.名古屋大学太陽地球環境研究所、2.名古屋大学年代測定総合研究センター、3.福島大学共生システム理工学研究科)

キーワード：radiocarbon, tree-rings, cosmic-ray, SPE

Radiocarbon (¹⁴C) is produced by incoming cosmic rays to the Earth. Produced ¹⁴C becomes ¹⁴CO₂ and is absorbed by trees by photosynthesis. Then,tree-rings record the past cosmic ray intensity. Rapid yearly increases in the ¹⁴C content have been detected for the period from AD 774 to AD 775 and from AD 993 to AD 994. Althogh some candidates for the cause of these cosmic-ray invents have been considered, it has been considered that the solar activity (large SPE) is the most plausible cause.There is the possibility that a lot of ¹⁴C increase events like the AD 775 one are hidden in the periods when the ¹⁴C content has not been measured with a 1-year resolution. If we detect such events, we are able to discuss a detailed occurrence rate of large SPE which is very important factor to prepare for future large SPEs.We are planning to search for ¹⁴C increase events by the measurements of ¹⁴C content in Japanese trees for this 5000 years. In this thesis, we are going to explain the plan and problems.