The effects of helium diffusion on solar p-mode frequencies

Precise solar models are computed with and without including helium diffusion. We show that the inclusion of helium diffusion according to the Bahcall-Loeb prescription causes systematic shifts of order 1-5 μHz in the predicted p-mode oscillation frequencies. Calculations with the diffusion coefficients multiplied and divided by two show that the inferred effects are linearly proportional to the magnitude of the diffusion. Relative to a model that does not include helium diffusion, the models with diffusion increase the frequencies of low-l modes and decrease the frequencies of high-l modes. The effect on the frequencies of intermediate-l modes depends on whether or not the modes penetrate significantly below the convection zone