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Lookup NU author(s): Professor Chris Jones, Dr Yue-Kin TsangORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2025. Convection driven geodynamo models in rotating spherical geometry have regimes in which reversals occur. However, reversing dynamo models are usually found in regimes where the kinetic and magnetic energy is comparable, so that inertia is playing a significant role in the core dynamics. In the Earth's core, the Rossby number is very small, and the magnetic energy is much larger than the kinetic energy. Here we investigate dynamo models in the strong-field regime, where magnetic forces have a significant effect on convection. In the core, the strong field is achieved by having the magnetic Prandtl number Pm small, but the Ekman number E extremely small. In simulations, very small E is not possible, but the strong-field regime can be reached by increasing Pm. However, if Pm is raised while the fluid Prandtl number Pr is fixed at unity, the most common choice, the Péclet number becomes small, so that the linear terms in the heat (or composition) equation dominate, which is also far from Earth-like behaviour. Here we increase Pr and Pm together, so that nonlinearity is important in the heat equation and the dynamo is strong-field. We find that Earth-like reversals are possible at numerically achievable parameter values, and the simulations have Earth-like magnetic fields away from the times at which it reverses. The magnetic energy is much greater than the kinetic energy except close to the reversal times.
Author(s): Jones CA, Tsang Y-K
Publication type: Article
Publication status: Published
Journal: Physics of the Earth and Planetary Interiors
Year: 2025
Volume: 360
Print publication date: 01/03/2025
Online publication date: 07/01/2025
Acceptance date: 30/12/2024
Date deposited: 27/01/2025
ISSN (print): 0031-9201
ISSN (electronic): 1872-7395
Publisher: Elsevier BV
URL: https://doi.org/10.1016/j.pepi.2024.107303
DOI: 10.1016/j.pepi.2024.107303
Data Access Statement: The numerical code used for the geodynamo simulations reported in this paper is at https://github.com/Leeds-Spherical-Dynamo. For access to the Github repository, please contact the authors. The MAGIC code is available at https://github.com/magic-sph/magic and is open access, with code documentation available at the github.com site.
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