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Early Earth Dynamos (Invited speaker)

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DY2W01 - Dynamos in planets and stars - similarities and differences

The Earth’s magnetic field has existed for at least 4 Gyr. Before the onset of crystallisation of the solid innercore, and for possibly as much as 90% of Earth history, the relevant geometry was that of a full sphere. Numericalstudies of the geodynamo in a full sphere are thus critical for understanding the paleomagnetic field.However, direct numerical simulation of the dynamo problem in a whole sphere have been rare,partially due to the difficulty of proper treatment of the singularity at the sphere centre. Using a fullyspectral method with basis functions which are smooth everywhere, we run a series of numericalsimulations to investigate dynamos in a whole sphere. For various Ekman numbers E, measuring theeffect of viscosity compared to the Coriolis force, the dynamo regime dependence on the Rayleighnumber Ra (measuring thermal forcing) and the magnetic Prandtl number Pm (controlling electricalconductivity) was determined, and we find it to be different from that of dynamos operating in aspherical shell.  With Jiawen Luo and Philippe Marti

This talk is part of the Isaac Newton Institute Seminar Series series.

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