Work

Rapidly rotating early-Earth dynamos in a full-sphere geometry

Year: 2025

Type: article

Abstract: SUMMARY While the Earth’s magnetic field has existed for 4 Gyr or more, most recent estimates for the age of the inner core nucleation date no further back than 1.5 Gyr. As a consequence, the relevant geometry for the Earth’s dynamo has been a full sphere for much of its life, fundamentally different from the present-day dynamo operating in a spherical shell. We therefore systematically study magnetic field generation in a rapidly rotating full sphere where convection is driven by heat sources uniformly distributed throughout the fluid. We observe a rich diversity of behaviour in our solutions, including dipolar and multipolar dominated fields, together with vacillating and chaotically reversing magnetic fields. At Prandtl number of unity, we construct regime diagrams as a function of three control parameters, namely the Rayleigh, Ekman and magnetic Prandtl number, which show some similarities with the corresponding diagrams for spherical shell dynamos. This study comprehensively demonstrates the feasibility of early-Earth dynamos that operate based on secular cooling of the core.

Source: Geophysical Journal International

DOI: 10.1093/gji/ggaf063

Authors: F Burmann, J Luo, P Marti, A Jackson

Institutions: ETH Zurich, Institute of Geophysics

Language: English

Topic: Geomagnetism and Paleomagnetism Studies

Subfield: Molecular Biology

Field: Biochemistry, Genetics and Molecular Biology

Domain: Life Sciences

Open Access status: gold

Estimated APC paid: $3,416

Funders: Eidgenössische Technische Hochschule Zürich, H2020 European Research Council