Convective contributions to the frequencies of solar oscillations

Differences between observed and theoretical ei,eigen-frequencies of the Su n have characteristics which identify them as arising predominantly from pr operties of the oscillations in the vicinity of the solar surface: in the s uper-adiabatic, convective boundary layer and above. These frequency differ ences may therefore provide useful information about the structure of these regions, precisely where the theory of solar structure is most uncertain. In the present work we use numerical simulations of the outer part of the S un to quantify the influence of turbulent convection on solar oscillation f requencies. Separating the influence into effects on the mean model and eff ects on the physics of the modes, we find that the main model effects are d ue to the turbulent pressure that provides additional support against gravi ty, and thermal differences between average 3-D models and 1-D models. Surf aces of constant pressure in the visible photosphere are elevated by about 150 km, relative to a standard envelope model. As a result, the turning points of high-frequency modes are raised, while t hose of the low-frequency modes remain essentially unaffected. The correspo nding gradual lowering of the mode frequencies accounts for most of the fre quency difference between observations and standard solar models. Additiona l effects apr expected to come primarily from changes in the physics of the modes, in particular from the modulation of the turbulent pressure by the oscillations.