Solar structure as constrained by observed solar oscillation frequencies

The thousands of well determined solar oscillation frequencies can be interpreted in terms of the composition and structure of the Sun. Recent theoretical modeling at Los Alamos has considered many solar structure and evolution problems. These include the solar center structure, bearing on the solar neutrino diffusion; and the depth and bottom structure of the convection zone, defining limits on the influence of turbulent mixing in the solar interior. In addition solar oscillation frequencies have helped refine knowledge of high temperature and density material properties, such as a sophisticated equation of state and recently improved radiative opacities. The procedure used to probe the solar structure is to identify those few frequencies that have large weight in the layers being studied. Then simple changes of single parameters of the model and its predicted frequencies can be made to improve agreement with observed frequencies in addition to matching the accurately known solar mass, radius and luminosity. Recent results for the convection zone structure and its composition will be given. A particularly interesting result is that oscillation frequencies require a rather steep composition gradient at the bottom of the convection zone, very similar to that given by diffusion without any mixing due to turbulence from convection overshooting or other sources. Thus the depletion of the solar surface lithium does not seem to be caused by significant post-main-sequence overshooting of the convection zone matter, and it must be explained by other mechanisms. The possibility of a small amount of mass loss during the solar life allows convection zone material now to have come from earlier deeper regions where the temperature then was high enough to explain the present observed lithium depletion