Solidification of liquid core from thermal expansivity measurements on the Fe-Ni-S liquids

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K03805
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17040:Solid earth sciences-related
• Research Institution: Okayama University
• Principal Investigator: urakawa Satoru 岡山大学, 自然科学研究科, 教授 (30201958)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 惑星磁場 / 流体核 / 組成対流 / 断熱温度勾配 / 熱膨張率 / Fe-Ni-S系

Outline of Final Research Achievements

Some bodies in the solar system have a magnetic field like the earth, and another bodies once had. The magnetic field of an Earth-like rock body originates from a dynamo driven by thermo-compositional convection of the liquid core. The lifetime of the magnetic field depends on how the compositional convection of the liquid Fe-alloy caused by the cooling of the core works. We have clarified how the compositional convection pattern of the Fe-FeS core changes depending on the chemical composition and pressure. It was found that relatively small bodies such as the Earth’s moon solidify mainly from the top of the liquid core, resulting in compositional convection.

Free Research Field

地球惑星科学

Academic Significance and Societal Importance of the Research Achievements

太陽系の天体の熱的・化学的進化の詳細を理解することは，45億年前の太陽系の誕生から今日までの歴史の解明という地球惑星科学の壮大な目標の重要な部分を占める。天体の磁場はその熱的・化学的現象の結果であり，衛星によって観測される磁場は天体の熱的・化学的進化の記録を残している。天体の磁場の起源である流体コアの組成対流を理解することは，観測された天体の磁場からその熱的・化学的進化を読み解く鍵を与える。