11/04/16 Dario Alfe (UCL)
(au centre Blaise Pascal)
de 14:00 à 15:00
|S'adresser à||Razvan Caracas|
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A title could be “Heath transport and thermal structure of the Earth’s core"
The Earth is a dynamic planet, reshaping its surface and its interior on geological time scales. Most of the energy responsible for these activities was deposited in the original accretion process 4.5 billion years ago, and is continuously produced in the decay of radioactive material. On much shorter time scales (thousands of years), the Earth's liquid outer core recycles and mixes throughout. These convective motions are responsible for the generation of the Earth magnetic field, and for transporting heat from the bottom of the core to the base of the mantle, where it is used to drive mantle convection. Transport of heat mechanisms in the core are determined by the thermal conductivity of core material. Ohmic dissipation of the magnetic field generating currents depends on the electrical conductivity. Knowledge of these two parameters is therefore essential to build a thermal model of the Earth and its magnetic field.I will discuss recent direct calculations and measurements of these two parameters, which are significantly higher than conventional estimates based on extrapolation from ambient conditions, and have important consequences for our understanding of the Earth's thermal structure, and in particular for the sustainability of convection in the outer core. I will also try to mention very recent results on mantle/core chemical equilibrium, which may indicate a flux of oxygen from the mantle to the core, and how this can affect the overall stability of the liquid core.
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