Occurrence rate of extreme SPEs for the last 5000 years

2020 Fiscal Year Final Research Report

• Project/Area Number: 16H06005
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Nagoya University
• Principal Investigator: Miyake Fusa 名古屋大学, 宇宙地球環境研究所, 准教授 (90738569)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 樹木年輪 / 放射性炭素 / 宇宙線生成核種 / Solar Proton Event

Outline of Final Research Achievements

Large-scale Solar Proton Events (SPEs), originate from solar flares and coronal mass ejections, can cause enormous damage such as a breakdown of artificial satellites. Although the large-scale SPEs have been observed directly for the past ~70 years, the longer-term characteristics of SPE (e.g., their occurrence rate and upper limit) are not well understood. The purpose of this study is to investigate the signatures of large-scale SPEs occurred in the past by measuring the 14C concentration of tree rings, which is a proxy for large-scale SPE, with a one-year resolution and capturing a rapid increases in 14C concentrations. We aim to clarify the occurrence rate of large-scale SPEs and the relationship between the occurrence of large-scale SPEs and solar activity.

Free Research Field

宇宙線生成核種

Academic Significance and Societal Importance of the Research Achievements

本研究の長期にわたる樹木年輪の14C分析により、西暦775年、西暦994年、紀元前660年頃の3つの大規模Solar Proton Event（SPE）の存在が示された。また、これら3イベントについて、詳細な樹木年輪の14C分析や南極ドームふじ氷床コアの10Be分析から発生特性について明らかにした。本研究により得られた1年分解能の14Cデータは、年代測定の基盤として非常に重要である。本研究により得られた結果を含む、大規模SPEに関する最新の知見をまとめた書籍を出版した。