2022 Fiscal Year Final Research Report

Physics of photonuclear reactions triggered by lightning discharges studied by simultaneous mapping observations of gamma rays and radio

Research Project

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Project/Area Number	19H00683
Research Category	Grant-in-Aid for Scientific Research (A)
Allocation Type	Single-year Grants
Section	一般
Review Section	Medium-sized Section 15:Particle-, nuclear-, astro-physics, and related fields
Research Institution	Institute of Physical and Chemical Research (2020-2022) Kyoto University (2019)
Principal Investigator	Enoto Teruaki 国立研究開発法人理化学研究所, 開拓研究本部, 理研白眉研究チームリーダー (20748123)
Co-Investigator(Kenkyū-buntansha)	鴨川仁静岡県立大学, その他部局等, 特任准教授 (00329111) 森本健志近畿大学, 理工学部, 教授 (60403169) 小野英理京都大学, 学術情報メディアセンター, 助教 (80827460)
Project Period (FY)	2019-04-01 – 2023-03-31
Keywords	photonuclear reaction / gamma-ray glow / atmospheric physics / radiation measurement / lightning discharge / neutron / citizen science
Outline of Final Research Achievements	This research aims to elucidate high-energy atmospheric physics by observing the radiation associated with thunderclouds and lightning discharges, which have become increasingly found in recent years. In particular, we study the evolution of lightning discharges and electron acceleration, photonuclear reactions associated with lightning, and the triggering mechanism of lightning discharges. During the three-year research period, we established a new observation system of more than 70 small radiation monitors around Kanazawa, famous for its winter lightning, using the Citizen Science framework. As a result, we found an association between the gamma-ray glow from a thundercloud (electron acceleration area) and the initiation of lightning discharges by the gamma-ray and radio measurements. This is one of the attractive evidence of our efforts to solve the mystery of the lightning trigger, and we proposed the subsequent Fundamental Research A.
Free Research Field	High-energy atmospheric physics
Academic Significance and Societal Importance of the Research Achievements	放電は強い電場で発生するが、雷雲内で放電を開始するだけの強電場が観測できないことから、雷がどのように始まるかは大気科学における長年の未解決問題である。本研究は宇宙線空気シャワーと雷雲の相互作用が雷放電のトリガーに関わるのではないかという作業仮説を観測的に研究する学術的な意義がある。また、その実施においては金沢の市民サポーターと連携したシチズンサイエンスという手法を持ち込んでおり、科学をその成果創出だけではなく、科学そのものを市民とともに楽しむという社会的意義がある。実際、2022年度には市民サポーターを巻き込んだワークショップを金沢で実施し、科学と文化の融合を狙っている。