This graphic from A.G. Kosovichev shows the radial and latitudinal variations of the sound speed in the Sun, relative to a standard solar model. Red color corresponds to the positive variations (`hotter' regions), and blue color corresponds to negative variations (`cooler' regions).
You can also download a postscript version of the above figure.
The relative differences between the squared sound speed in the Sun and in a standard solar model, are inferred from two months of MDI data in the next plot. The horizontal bars show the spatial resolution, and the vertical bars are the error estimates. The reference solar model was model "S" of Christensen-Dalsgaard et. (1996). This model was a standard evolutionary model computed using the most recent information on nuclear reaction rates (Bahcall and Pinsonneault, 1995) and radiative opacity and the equation of state (Rogers and Iglesias, 1996). The gravitational settling and diffusion of helium and heavier elements were taken into account folliwing the theory by Michaud and Proffitt (1993).
You can also download a postscript version of the above figure.
This sound speed was inferred using an inversion process, starting with MDI reduced oscillation frequency data and the above described solar physics models and parameters.
You can find more about this result from the preprint, (1.4Mb,postscript) titled: Internal Structure and Rotation of the Sun: First Results from the MDI Data, by A.G. Kosovichev, J. Schou, P.H. Scherrer, R.S. Bogart, R.I. Bush, J.T. Hoeksema, J. Aloise, L. Bacon, A. Burnette, C. DeForest, P.M. Giles, L. Leibrand, R. Nigam, M.Rubin, K. Scott, S.D. Williams, S.Basu, J. Christensen-Dalsgaard, W. Dappen, E.J. Rhodes,Jr., T.L. Duvall, Jr., R. Howe, J.J. Thompson, D.O. Gough, T. Seikii, J. Toomre, T.D. Tarbell, A.M. Title, D. Mathur, M. Morrison, J.L.R. Saba, C.J. Wolfson, I. Zayer, and P.N. Milford.
SOHO SOI/MDI Results.
The SOI Main Page.