New mechanism for geomagnetic polarity reversals induced by flow reversals

2015 Fiscal Year Final Research Report

• Project/Area Number: 24244073
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: YANAGISAWA Takatoshi 国立研究開発法人海洋研究開発機構, 地球深部ダイナミクス研究分野, 主任研究員 (20359186)
• Co-Investigator(Kenkyū-buntansha): TASAKA Yuji 北海道大学, 工学研究院, 准教授 (00419946) ; KAGEYAMA Akira 神戸大学, システム情報学研究科, 教授 (20260052) ; SAKURABA Ataru 東京大学, 理学系研究科, 助教 (50345261) ; MIYAGOSHI Takehiro 国立研究開発法人海洋研究開発機構, 地球深部ダイナミクス研究分野, 主任研究員 (60435807) ; SUMITA Ikuro 金沢大学, 自然システム学系, 准教授 (90334747)
• Co-Investigator(Renkei-kenkyūsha): HAMANO Yozo 国立研究開発法人海洋研究開発機構, 地球深部ダイナミクス研究分野, 特任上席研究員 (90011709)
• Project Period (FY): 2012-04-01 – 2016-03-31
• Keywords: 地磁気の逆転 / 液体金属の対流 / 流れ場の反転 / 室内実験 / 数値シミュレーション

Outline of Final Research Achievements

We explored magnetoconvection and rotating convection by means of laboratory experiments and numerical simulations, to elucidate the mechanism that induces geomagnetic polarity reversals. We established a regime diagram of convection in a liquid metal under the influence of imposed horizontal magnetic field. The searched space is summarized by the relation between buoyancy and magnetic force, in which a regime exists that reversals of flow direction repeat intermittently. We found that the key mechanism for flow reversals is an occurrence of large-scale circulation in a horizontal plane. We also performed numerical simulations of dynamos in a rotating spherical shell, and clarified the relation between polarity reversals and transitions of convection flow.

Free Research Field

固体地球惑星科学