Hydrodynamic and magnetohydrodynamic instabilities in differentially-rotating stars

Observational advances in helio- and astero-seismology have highlighted our poor understanding of the mechanisms of chemical mixing and angular momentum transport in the stably-stratified radiation zones of the Sun and other stars. This project will study various hydrodynamic or magnetohydrodynamic instabilities in stellar and planetary interiors that could contribute to mixing and angular momentum transport. These processes can modify the internal rotations, structures and evolutionary ages of stars, but they are commonly either neglected or modelled in an ad-hoc manner in current stellar models. This project will involve a combination of linear analysis and numerical simulations to understand the properties of one or more of these instabilities, and to determine their nonlinear behaviour. One of the ultimate goals of this project is to understand the nonlinear outcome of these instabilities and another is to provide simple parameterisations of their mixing and angular momentum transport properties that can be incorporated in stellar models.