Modèles expérimentaux et numériques de la convection dans le noyau de la Terre.

Abstract : It is believed that thermo-solutal convection in the Earth liquid core is the driving source of the geodynamo, which maintains the magnetic field of the planet. Theoretical constraints imply that flow is probably in a developed turbulent state, highly constrained though by the dominent influence of Coriolis force. Despite remarkable recent advances in numerical and experimental fields, no turbulent convective dynamo model has ever been produced. This work is a first step towards this goal, and aims at modelling the non-magnetic convective flow of a spherical shell of liquid metal (gallium), in the regime of high departures from criticality (heating up to 100 times the critical value), and rapid rotation rates (Ekman number down to 10-7). A systematic and quantitative experimental study has been performed first, using an ultrasonic Doppler velocimetry technique. We have then built a numerical quasigeostrophic model for a better understanding of flow structures. This model has been quantitatively compared with the experiments. This work opens the way to experimental magnetoconvection, as weil' as hybrid numerical dynamo models able to separate scales between a fine scale turbulent velocity field and a magnetic field sustained at large scales.
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Julien Aubert. Modèles expérimentaux et numériques de la convection dans le noyau de la Terre.. Géophysique [physics.geo-ph]. Université Joseph-Fourier - Grenoble I, 2001. Français. ⟨tel-00683861v2⟩

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