Regime diagrams for planetary dynamos

February-July 2020

Most planets generate a magnetic field by dynamo action. The dynamical regime in which this dynamo operates depends on the size and rotation rate of the planet and on the physical properties of the fluid where dynamo action takes place. We have proposed a tool for determining the dynamo regimes of planets (Nataf & Schaeffer, in Treatise on Geophysics, 2015). So-called ‘tau-ell’ regime diagrams position relevant physical phenomena such as wave propagation in a time scale-length scale representation, from which turbulent paths can be proposed.

We propose to extend this approach with new ingredients, and apply it to predict the behaviour of dynamos in the solar system. Typical outcome would be predictions on the range of flow velocities in these objects, on the types of waves they can harbour and on the main dissipation mechanisms. The candidate will gather available information on planetary interiors, grasp the physical concepts involved, and write simple programs to build relevanttau-ell diagrams.

references :

• Turbulence in the core->doc6414, Nataf H-C. and N. Schaeffer, in Treatise on Geophysics, second Edition, Vol. 8 Core Dynamics, P. Olson and G. Schubert Eds, Elsevier B.V., p. 161-181, 2015.
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