Good Vibrations Seminar #10: Felix Ahlborn (MPA, Garching, Germany)

May 19, 2021 | 10:00 am 11:00 am

Turbulent convection theories for stellar evolution models

Felix Ahlborn (Max Planck Institute for Astrophysics, Garching)

Convective overshoot mixing has been shown to be an important ingredient of stellar structure models. It determines to a large degree how much fuel convective cores can consume, which strongly impacts on stellar luminosities and lifetimes. The convective flows encountered in stellar interiors are highly turbulent. This poses a number of numerical challenges for the modeling of convection in stars.
In this talk I will discuss the theory and the results of an effective turbulence model which we implemented into a 1D stellar evolution code. The turbulent convection model in use relies on the solution of second order moment equations (e.g. for turbulent kinetic energy and turbulent convective flux). The dissipation due to buoyancy waves in the overshooting zone is taken into account in an approximate fashion. Applying this turbulent convection model we compute stellar evolution models of intermediate mass main-sequence stars between 2 and 8 solar masses. Phenomena like overshoot mixing and modified temperature gradients emerge naturally as a solution of the turbulent convection model equations.
The overshooting extent determined from the turbulent convection model is comparable to other overshooting descriptions. The size of the mixed core decreases with decreasing stellar mass without external limitation. We find that the dissipation by buoyancy waves is a relevant ingredient in the turbulent convection model in use. High precision asteroseismic modeling will potentially allow testing some of the predictions made by this turbulent convection model.

Leave a Reply

Your email address will not be published. Required fields are marked *