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Above left we plot the variations in rotation rate for radii 0.72 R, (left)
and 0.63 R (right), and various latitudes, showing results from RLS (filled) and OLA (open)
inversions of GONG (black) and MDI (red) data. Note the prominent periodic variations at 0.72 R at the equator, with a period of 1.3 years, and the anticorrelated variation at 0.63 R. There are also more erratic variations, with
a different period, at 60° latitude.
The relationship of these variations to the magnetic cycle is still unclear,
but it is interesting that they occur in a region that is believed to be the seat of the solar dynamo.
The plots at above right show (A) the best-fit sine wave (frequency 0.76±0.1 y-1) superimposed on the GONG RLS data, (B) the power spectrum at 0.72 R, 0º, (C) power at 0.76 y-1 as a function of latitude at 0.72R, (D) power at 0.76 y-1 at 0º as a function of radius.
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