STANDARD SOLAR MODEL - INTERPLAY BETWEEN THE EQUATION OF STATE, THE OPACITY AND THE DETERMINATION OF THE INITIAL HELIUM CONTENT

Solar models computed with the Geneva evolutionary code are presented. We examine the sensitivity of the structure of the solar model to the microphysics. The influence of the equation of state, of the opacity and of the mixture of heavy elements on the determination of the-initi al solar helium content is discussed. Our reference model calculated w ith the best available input physics, i.e. with the Mihalas-Hummer-Dap pen equation of state and the new radiative opacities from Iglesias et al. (1992) and Kurucz (1991), has an initial helium abundance Y = 0.2 779 in mass fraction. The radius at the base of the convective zone re ported to the solar radius is equal to 0.718, in excellent agreement w ith helioseismic observations. The central temperature has a value of 15.56 10(6)K. The predicted total neutrino capture rates for the chlor ine and gallium experiments are respectively equal to 7.49 and 127.5 S NUs and that confirms that the so-called ''neutrino problem'' persists in spite of the recent improvements of the physics.