Stellar interior convection: From 1D to 3D and back again

Robert Andrassy (University of Victoria)

April 18, 2016

–

Abstract: Convection and convective boundary mixing (CBM) are inherently three-dimensional hydrodynamic processes. Because of the long time scales involved, stellar evolution is usually modelled in one spatial dimension using simple parametric models of convection and CBM. The parameters and approximations in these models are known to influence stellar evolution and nucleosynthesis. Three-dimensional hydrodynamic simulations provide us with a very detailed picture of stellar convection on the dynamical time scale. I will report on our team”s progress in using such simulations to investigate fundamental properties of convective shells in conditions similar to those in the O-shell burning phase of massive stars. We focus on characterizing the convective boundary and the mixing of material across this boundary. Results from 768^3 and 1536^3 grids are encouragingly similar (typically within 20%). Several global quantities, including the rate of mass entrainment at the convective boundary and the driving luminosity, are related by scaling laws. I will show how the detailed information provided by the three-dimensional simulations can be used to improve the one-dimensional mixing models currently used in stellar evolution.