Séminaire : Turbulent transport in stellar interiors

Stellar models are essential in many astrophysical domains, from cosmology and chemical evolution of galaxies to exoplanetary systems. It is thus crucial to be able to produce reliable and realistic evolution models. This is currently hindered by the lack of a self-consistent description of macroscopic transport processes, in particular those driven by hydrodynamical instabilities.

I will show three examples in which direct numerical simulations can enable us to constrain such turbulent processes: shear instability, thermohaline convection and convective boundary mixing.

Shear instability occurs in stellar radiative zones when differential rotation generates a velocity shear which is strong enough to balance stable stratification.
Thermohaline (or fingering) convection occurs in regions which are thermally stable, but chemically unstable.
Convective boundary mixing (or overshooting) is the fact that at the boundary between a convective zone and a radiative zone, matter from the convective zone can penetrate into the radiative zone before being braked and mixed.