Description
In 1D stellar evolution models, the process of convection is often described using the mixing length theory (MLT). However, MLT does not account for all relevant aspects of turbulence. For example, it does not account for non-locality, what makes ad hoc extensions necessary. The Kuhfuss theory is one of the theories that attempts to derive a more complete picture of turbulent convection. In this theory, non-locality is not implemented artificially, but is inherent in the theory. Both versions of the Kuhfuss theory, the 1-equation model and the 3-equation model, are implemented in the stellar evolution code GARSTEC. Ahlborn et al. (2022) tested both versions on convective cores on the main sequence and found promising results. Building on these results, we tested the Kuhfuss theory for convective envelopes. We applied the 1-equation model of the Kuhfuss convection theory to a stellar model calibrated to the Sun. Using helioseismic measurements of quantities of the convective envelope and interior structure, we tested the Kuhfuss theory and quantified the differences between the Kuhfuss theory compared to MLT. We found that the 1-equation model does not model the temperature stratification in the convective boundary mixing region well. We therefore conclude that the more complex 3-equation model is needed to appropriately model the temperature stratification in the convective boundary mixing region.
