2022 Fiscal Year Final Research Report
Understanding Thermal Evolution through Experimental Constraints on Conduction Properties in the Earth's Outer and Inner Core
| Project/Area Number |
19H00716
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Medium-sized Section 17:Earth and planetary science and related fields
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
Kenji Ohta 東京工業大学, 理学院, 准教授 (20727218)
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| Co-Investigator(Kenkyū-buntansha) |
伊藤 正一 京都大学, 理学研究科, 准教授 (60397023)
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| Project Period (FY) |
2019-04-01 – 2023-03-31
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| Keywords | 地球中心核 / 電気抵抗率 / 熱伝導率 / 粘性率 / 鉄合金 / ダイヤモンドアンビルセル / 二次イオン質量分析法 / 自己拡散係数 |
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| Outline of Final Research Achievements |
The purpose of this study is to clarify the transport properties of the Earth's core from high-pressure experiments and to promote the understanding of the thermal evolution process of the Earth. 4 years of research have established several methods to determine the electrical and thermal conductivity and self-diffusion coefficient of the iron alloy that makes up the core under high-pressure conditions. As a result, we succeeded in determining the electrical resistivity of liquid iron and the thermal conductivity of solid iron under actual Earth's core conditions, achieving a major breakthrough. The determination of the diffusion coefficient of Ni in iron-light element alloys has also provided new constraints on the viscosity of the Earth's inner core. It can be said that a consensus among researchers has been reached on the magnitude of the conductivity of the Earth's core, which was disputed at the beginning of this study.
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| Free Research Field |
高圧地球惑星科学
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| Academic Significance and Societal Importance of the Research Achievements |
地球中心核を構成する物質の輸送特性は内核の年齢など地球の構造進化史を解明する上で重要な物性値である。しかし、地球中心核に相当する条件での物質の輸送特性（電気・熱伝導率、粘性率）は実験による制約が難しい物性であった。本研究の結果から結論付けられる重要な知見は、地球中心核の伝導度がこれまでの予想の上限値に近く、内核は10億歳以下の年齢で、熱対流を起こさないということである。このことを実証するような地球物理学的観測と古地磁気観測結果が今後更に展開されていくだろう。本研究の成果から新たに湧き上がる疑問は今後の別の課題として提案されていく。
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