日本地球惑星科学連合2022年大会

講演情報

[E] ポスター発表

セッション記号 S (固体地球科学) » S-GC 固体地球化学

[S-GC35] Volatiles in the Earth - from Surface to Deep Mantle

2022年5月29日(日) 16:00 〜 18:00 オンラインポスターZoom会場 (18) (Ch.18)

コンビーナ:角野 浩史(東京大学大学院総合文化研究科広域科学専攻広域システム科学系)、コンビーナ:Yama Tomonaga(University of Bern)、佐野 有司(高知大学海洋コア総合研究センター)、コンビーナ:羽生 毅(海洋研究開発機構 海域地震火山部門)、座長:Tomonaga Yama(University of Bern)、羽生 毅(海洋研究開発機構 海域地震火山部門)、佐野 有司(高知大学海洋コア総合研究センター)、角野 浩史(東京大学大学院総合文化研究科広域科学専攻広域システム科学系)

16:00 〜 18:00

[SGC35-P05] Solar flare activity as a new, unknown source of 3He in the atmosphere

*佐野 有司1、エスコバル テレサ2高畑 直人2、張 茂亮3後藤 大輔4、ピンチ ダニエレ5マーティー ベルナード6 (1.高知大学海洋コア総合研究センター、2.東京大学大気海洋研究所、3.天津大学、4.国立極地研究所、5.ケベック大学モントリオール校、6.ロレーヌ大学)

キーワード:ヘリウム同位体、大気、太陽フレア

Measurements of helium in the atmosphere suggest a supply of crustal 4He from fossil fuel emissions since the onset of industrial activity [1,2]. However, corresponding 3He/4He ratio of air appears near-constant [3,4], which calls for an unknown source of 3He to compensate contribution of anthropogenic 4He. Here we report 3He/4He variations measured in atmospheric air during a solar flare event. Samples were collected in Ny-Ålesund, Svalbard islands near the North Pole. On September 6th, 2017, a massive solar explosion, or solar flare, occurred. The solar wind was expected to reach the Earth on September 8th [5]. Therefore, the dates of air sample collection were set for eight days about one week apart, from August 30th to October 18th, 2017. The 3He/4He ratios were measured in the samples and calibrated against the standard atmosphere collected in Kashiwa City, Chiba Prefecture, Japan [6]. The 3He/4He ratios varied from -6.1‰ to +7.9‰ compared the air standard. The 3He/4He ratios of 12 samples agreed with the atmospheric values of Kashiwa within uncertainties. A total of five samples showed an excess of 3He compared the atmospheric ratio. These samples were collected on September 13th, 20th, and 27th, immediately after the solar flare event of September 6th. If the solar wind, enhanced by solar flares, was fed into the atmosphere by the auroral precipitation mechanism [7], it would increase the polar atmospheric helium isotope ratio. The helium would then be diluted by diffusion and the excess 3He would rapidly disappear. We therefore propose that the unknown source of 3He capable to compensate for anthropogenic addition of 4He is the injection of solar wind-derived 3He into the atmosphere.

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