CIG Webinar Thursday April 25: Geodynamo and Mantle Convection - I. Thomas Frasson & II. Daniel Thallner

I. Effect of mantle convection on the geodynamo behaviour in numerical models.
Thomas Frasson, Université Grenoble Alpes

Paleomagnetic evidence shows that the behaviour of the geodynamo has changed during geological times. These behaviour changes are visible through variations in the strength and stability of the magnetic dipole. Variations in the heat flux at the core-mantle boundary (CMB) due to mantle convection have been suggested as one possible mechanism capable of driving such a change of behaviour.

Coupling mantle convection models and geodynamo models is crucial to understanding how the geodynamo can react to variations in mantle convection. This coupling can be studied by …

II. The Influence of Mantle Convection on Earth’s Geomagnetic Field Observables. Daniel Thallner, University of Florida

Studying the geomagnetic field and its variations over geological timescales provides insights into the geodynamo and deep Earth processes. Notably, a significant weak-field anomaly in the paleomagnetic record during the Precambrian-Cambrian transition suggests a shift from a thermally driven to a compositionally driven geodynamo upon inner core nucleation. However, a similar field behavior is indicated by weak geomagnetic field strengths observed during the Devonian period, that could be related to flow pattern changes in the outer core between small and large inner core regimes. These periods of weak field strength align with cyclic fluctuations observed in the long-term paleointensity record, which mirrors the time scale of convective overturn in Earth’s mantle. While the mantle’s cooling history dominates the core’s heat transport, its full impact on the geodynamo is still not well understood.

To quantify the impact of mantle convection on the long-term geomagnetic field, we compared…

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