Solar models and helioseismology

Helioseismic results put very important constraints on structure of the solar models, which can not be reachable by another way. These constraints lead toward what we should do to obtain a solar model in good agreement with the Sun. In this connection, diffusion of chemical elements took its indispensable part in the standard solar models. In this study, we obtained models without diffusion, with diffusion of H only and with diffusion of H and heavy elements. Influence of so-called tau -effect in equation of state is also discussed. Since heavy element abundance is not known very accurately, models with various initial heavy element abundance (Z) are also obtained to deduce which Z is appropriate. Relative sound speed difference between the Sun and model with diffusion of H and heavy elements and with Z = 0.02 is not larger than 0.2 %.