  We have computed accurate 1-D solar models including both a macroscopic
mixing process in the solar tachocline as well as up-to-date microscopic
physical ingredients. Using sound speed and density profiles inferred through
primary inversion of the solar oscillation frequencies coupled with the
equation of thermal equilibrium, we have extracted the temperature and hydrogen
abundance profiles. These inferred quantities place strong constraints on our
theoretical models in terms of the extent and strength of our macroscopic
mixing, on the photospheric heavy elements abundance, on the nuclear reaction
rates such as $S_{11}$ and $S_{34}$ and on the efficiency of the microscopic
diffusion. We find a good overall agreement between the seismic Sun and our
models if we introduce a macroscopic mixing in the tachocline and allow for
variation within their uncertainties of the main physical ingredients. From our
study we deduce that the solar hydrogen abundance at the solar age is $X_{\rm
inv}=0.732\pm 0.001$ and that based on the $^9$Be photospheric depletion, the
maximum extent of mixing in the tachocline is 5% of the solar radius. The
nuclear reaction rate for the fundamental $pp$ reaction is found to be
$S_{11}(0)=4.06\pm 0.07$ $10^{-25}$ MeV barns, i.e., 1.5% higher than the
present theoretical determination. The predicted solar neutrino fluxes are
discussed in the light of the new SNO/SuperKamiokande results.
