Here are some additional materials for the sinewave-fitting plot:

• High resolution TIFF file.
• High resolution GIF file.

Sine wave fitting was used to quantify the periodicities in the data. We fitted asin(t)+bcos(t) to the rotation-rate residuals over a range of frequencies. The frequency giving the fit with the lowest chi-squared was then selected as the 'best fit' frequency for the location, with power (in squared nHz per frequency bin) being calculated as (a**2+b**2).

Notice the weaker peak of power at the 0.77/y frequency at 0.63R at the equator, corresponding to the anticorrelated variations seen here. Consideration of the resolution of the inversions leads us to believe that this is a real phenomenon, which may have interesting implications for solar models.

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