Article Dans Une Revue Physics of the Earth and Planetary Interiors Année : 2025

Core-surface kinematic control of polarity reversals in advanced geodynamo simulations

Résumé

The geomagnetic field has undergone hundreds of polarity reversals over Earth's history, at a variable pace. In numerical models of Earth's core dynamics, reversals occur with increasing frequency when the convective forcing is increased past a critical level. This transition has previously been related to the influence of inertia in the force balance. Because this force is subdominant in Earth's core, concerns have been raised regarding the geophysical applicability of this paradigm. Reproducing the reversal rate of the past million years also requires forcing conditions that do not guarantee that the rest of the geomagnetic variation spectrum is reproduced. These issues motivate the search for alternative reversal mechanisms. Using a suite of numerical models where buoyancy is provided at the bottom of the core by inner-core freezing, we show that the magnetic dipole amplitude is controlled by the relative strength of subsurface upwellings and horizontal circulation at the core surface. A relative weakening of upwellings brings the system from a stable to a reversing dipole state. This mechanism is purely kinematic because it operates irrespectively of the interior force balance. It is therefore expected to apply at the physical conditions of Earth's core. Subsurface upwellings may be impeded by stable stratification in the outermost core. We show that with weak stratification levels corresponding to a nearly adiabatic core surface heat flow, a single model reproduces the observed geomagnetic variations ranging from decades to millions of years. In contrast with the existing paradigm, reversals caused by this stable top core mechanism become more frequent when the level of stratification increases i.e. when the core heat flow decreases. This suggests that the link between mantle dynamics and magnetic reversal frequency needs to be reexamined.

Fichier principal
Vignette du fichier
reversals.pdf (3.1 Mo) Télécharger le fichier
Origine Fichiers produits par l'(les) auteur(s)
Licence
DOI

Cite 10.1016/j.pepi.2025.107365 Autre Aubert, J., Landeau, M., Fournier, A., & Gastine, T. (2025). Core-surface kinematic control of polarity reversals in advanced geodynamo simulations. Physics of the Earth and Planetary Interiors, 364, 107365. https://doi.org/10.1016/j.pepi.2025.107365

DOI

Cite 10.18715/IPGP.2024.m0gw7hg5 Jeu de données Aubert, J., Landeau, M., Fournier, A., & Gastine, T. (2025). Replication data for ‘Core-surface kinematic control of polarity reversals in advanced geodynamo simulations’ [Data set]. IPGP Research Collection. https://doi.org/10.18715/IPGP.2024.M0GW7HG5

Données analysées dans l'article

Dates et versions

hal-05060600 , version 1 (08-05-2025)

Licence

Identifiants

Citer

Julien Aubert, Maylis Landeau, Alexandre Fournier, Thomas Gastine. Core-surface kinematic control of polarity reversals in advanced geodynamo simulations. Physics of the Earth and Planetary Interiors, 2025, 364, pp.107365. ⟨10.1016/j.pepi.2025.107365⟩. ⟨hal-05060600⟩
124 Consultations
182 Téléchargements

Altmetric

Partager

  • More