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Recent solar photospheric abundance analyses (Asplund et al. 2004, 2005;Lodders 2003) have revised downward the C, N, O, Ne, and Ar abundances by 0.15to 0.2 dex compared to previous determinations of Grevesse & Sauval (1998).With these revisions, the photospheric Z/X decreases to 0.0165 (0.0177Lodders), and Z to ~0.0122 (0.0133 Lodders). A number of papers report thatsolar models evolved with standard opacities and diffusion treatment usingthese new abundances give poor agreement with helioseismic inferences. Here weexplore evolved solar models with varying diffusion treatments to reduce thephotospheric abundances while keeping the interior abundances about the same asearlier standard models. While enhanced diffusion improves agreement with somehelioseismic constraints compared to a solar model evolved with the newabundances using nominal input physics, the required increases in thermaldiffusion rates are unphysically large, and none of the variations triedrestores the good agreement attained using the earlier abundances. Acombination of modest opacity increases, diffusion enhancements, and abundanceincreases near the level of the uncertainties, while somewhat contrived,remains the most physically plausible means to restore agreement withhelioseismology. The case for enhanced diffusion would be improved if theinferred convection-zone helium abundance could be reduced; we recommendreconsidering this derivation in light of new equations of state with modifiedabundances and other improvements. We also recommend considering, as a lastresort, diluting the convection zone, which contains only 2.5% of the sun'smass, by accretion of material depleted in these more volatile elements C, N,O, Ne, & Ar after the sun arrived on the main sequence.Comment: Version 2: 24 pages, 3 figures; Accepted to ApJ with omission of  g-mode predictions and discussion that are included in this preprin

Can Enhanced Diffusion Improve Helioseismic Agreement for Solar Models with Revised Abundances?