Séminaire de Mécanique d'Orsay

Le Jeudi 14 juin 2018 à 14h00 - Salle de conférences du LIMSI

Flows and dynamos in precessing spherical shells, application to the Moon.

Raphael Laguerre
Royal Observatory of Belgium

When considering a planetary liquid layer, precession is generally present, driving flows, hydrodynamic instabilities and perhaps dynamos. However, there is no systematic study of these flows in the spherical shell geometry relevant for planets, which makes difficult any extrapolation to planetary regimes. In this talk, we will consider a large number of magneto-hydrodynamic simulations of precessing spherical shells, where all the parameters have been systematically varied. We use this large simulations database to study the forced basic flows, the associated instabilities, and the dynamo capability of these flows. For instance, we derive and validate an explicit analytical estimate of the viscous dissipation obtained in our simulations. We also propose theoretical onsets for instabilities in precessing spherical shells, showing that the parametric instabilities due to the outer boundary conical layer are controlling the stability in most cases. Finally, we apply our results to the Moon, showing that turbulence can be expected in its liquid core during its whole history.

Accès Salle de conférences du LIMSI