EAS Publications Series

Stellar Evolution and Seismic Tools for Asteroseismology - Diffusive Processes in Stars and Seismic Analysis
C.W. Straka, Y. Lebreton and M.J.P.F.G. Monteiro (eds)
EAS Publications Series, 26 (2007) 145-152
DOI: 10.1051/eas:2007133

Turbulence in the Convection-Radiation Transition Layer of Solar-Type Stars: Effects on Oscillation Frequencies

C.W. Straka

Centro de Astrofísica da Universidade do Porto (CAUP), Rua das Estrelas, 4150-762 Porto, Portugal

(Published online: 20 June 2007)

Abstract
Three-dimensional Large Eddy Simulations (LES) of the convection-radiation transition layer of solar-type stars predict a different temperature stratification compared to models that use standard mixing-length theory. When these structural changes are taken into account theoretical oscillation frequencies are modified. Here, we compare the changes to the seismic spectra as predicted by the LES with those arising from diffusion and settling of helium and heavier elements. It is shown that turbulence effects in the modelling of the star $\alpha$ Centauri A change the large frequency separations twice as much as compared to those arising from gravitational settling, giving rise to a frequency shift opposite to what would have been expected from gravitational settling alone.