Scientific topics

In the Geodynamo team we study the physical mechanisms at the origin of the Earth’s magnetic field. The Earth’s core is made up of a solid inner core immersed in an ocean of liquid metal. By slowly crystallizing the inner core drives the motion of the liquid metal. The latter is turbulent and strongly affected by the rotation of the Earth. Other sources of motion like precession are also possible. We call dynamo effect the generation of the magnetic field by the motion of the liquid metal contained in the core.

The characteristic times involved are long (from one thousand years for the dynamo to one million years for inner core crystallization). However the magnetic field also changes over much shorter time scales (of the order of ten years or so).
In order to improve our models of the Earth’s dynamo we rely on magnetic field observations, laboratory experiments and numerical simulations of the hydrodynamic equations coupled to the electromagnetism equations (magnetohydrodynamics) and the heat equation.

We use the magnetic field measurements obtained either from satellites orbiting around the Earth, or from magnetic observatories spread over the surface of the Globe, or the measurements resulting from the fossilized field present in some rocks. We have constructed several laboratory experiments using water or liquid metal in order to study the mechanisms and force balances relevant for the Earth’s core dynamics. Our inner core models are constrained by seismological measurements and high pressure laboratory experiments.

Our models enable us to better understand physical phenomena acting in the Earth dynamo such as magnetohydrodynamic turbulence, propagation of fluid waves, natural convection influenced by rotation, or crystalline anisotropy. Dynamo effect is also present in many natural objects like planets, stars or galaxies.