Early evolution of the geomagnetic field induced by a basal magma ocean dynamo

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K03725
• 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: Kyushu University
• Principal Investigator: Takahashi Futoshi 九州大学, 理学研究院, 准教授 (20467012)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 地球磁場 / ダイナモ / コア / 底部マグマオーシャン / 初期地球

Outline of Final Research Achievements

The generation process of the ancient geomagnetic field was investigated using three-dimensional numerical dynamo simulation. In this study, we investigate the conditions for the generation of solutions with dipole-like symmetry and quadrupole-like symmetry in the dynamo region, and the generation and maintenance process by solving two types of problems: kinematic dynamo problems and MHD dynamo problems. It is found that non-linear interactions play an important role in determining the shape of the magnetic field and feeding back to the velocity field. This study suggests that the early geomagnetic field may have had a non-dipolar configuration.

Free Research Field

地球内部電磁気学

Academic Significance and Societal Importance of the Research Achievements

本研究の主な成果は次の３点になる。（１）地球磁場の形態を決定する要素として速度場と磁場の対称性および，非線型相互作用が重要な役割を果たしている可能性があることが明らかとなったこと。（２）相互作用の度合いが対流の駆動様式に依存して変動すること。（３）過去の地球磁場の形態が現在とは大きく異なるものであった可能性が示唆されたこと。