  The sound speeds of solar models that include element diffusion agree with
helioseismological measurements to a rms discrepancy of better than 0.2%
throughout almost the entire sun. Models that do not include diffusion, or in
which the interior of the sun is assumed to be significantly mixed, are
effectively ruled out by helioseismology. Standard solar models predict the
measured properties of the sun more accurately than is required for
applications involving solar neutrinos.
