Chemical Mixing Induced by Internal Gravity Waves in Intermediate-mass Stars

Internal gravity waves can cause mixing in the radiative interiors of stars. We study this mixing by introducing tracer particles into 2D hydrodynamic simulations. Following the work of Rogers & McElwaine, we extend our study to different masses (3, 7, and 20 M (circle dot)) and ages (ZAMS, midMS, and TAMS). The diffusion profiles of these models are influenced by various parameters such as the Brunt-Vaisala frequency, density, thermal damping, the geometric effect, and the frequencies of waves contributing to these mixing profiles. We find that the mixing profile changes dramatically across age. In younger stars, we noted that the diffusion coefficient increases toward the surface, whereas in older stars the initial increase in the diffusion profile is followed by a decreasing trend. We also find that mixing is stronger in more massive stars. Hence, future stellar evolution models should include this variation. In order to aid the inclusion of this mixing in 1D stellar evolution models, we determine the dominant waves contributing to these mixing profiles and present a prescription that can be included in 1D models.

Automated summary

Internal gravity waves have a significant impact on the mixing within the radiative interiors of stars. By studying the diffusion profiles of different mass and age models, we find that the mixing profile changes dramatically across age, with younger stars showing an increase in diffusion coefficient towards the surface and older stars experiencing a decreasing trend. Additionally, mixing is stronger in more massive stars. We propose a prescription to include this mixing in 1D stellar evolution models by identifying the dominant waves contributing to the mixing profiles.