Experiment on Core Dynamics
Résumé
This chapter surveys laboratory fluid experiments pertinent to the dynamics of the Earth's core. Laboratory fluid experiments play a special role in this subject because they incorporate in a fully self-consistent way the multi-scale processes that affect core dynamics. The fluid dynamics experiments described here include the effects of rotation (steady and variable), buoyancy (thermal and compositional), magnetic and electric fields, turbulence and instabilities, in both Cartesian and spherical geometries with a variety of boundary forcing types. Laboratory fluid experiments entail their own set of restrictions, which derive from their relatively small size and other practical considerations. We begin with a discussion of the fundamental experiment relevant to core dynamics, the formation of Taylor column structures in a rotating fluid. After describing the role of this phenomenon in the core, we review Ekman boundary layers and internal shear layers, geostrophic and precessing flows, rotational instabilities and quasi-geostrophic turbulence. We then consider convective flows driven by buoyancy forces and how these are affected by planetary rotation and magnetic fields. Finally, we summarize the successful dynamo experiments and ongoing efforts to bring these experiments closer to Earth conditions.