The Rotational Structure of the Region below the Solar Convection Zone

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Abstract
Frequency splittings derived from the first 4 month string of GONG data in the form of the Clebsch-Gordon coefficients are analyzed with particular emphasis on the region near the base of and just below the convection zone. It is found that the greatest changes in angular velocity occur across the region 0.60 < r = R/R☉ < 0.72. At equatorial latitudes, the angular velocity increases (outward) from 416 nHz at r = 0.645 to 455 nHz at r = 0.71, with a maximum angular velocity gradient dω(λ)/dr of order 2.2 × 10-3 (in units of nHz km-1) at r = 0.68 ± 0.01. At latitude 30°, there are some fluctuations in the angular velocity between r = 0.70 and r = 0.75, but below r = 0.70 the angular velocity is relatively uniform. At latitude 45°, the angular velocity decreases from 449 nHz at r = 0.645 to 415 nHz at r = 0.71, with a maximum (negative) gradient of magnitude 1.9 × 10-3 again at r = 0.68 ± 0.01; while at latitude 60° the angular velocity decreases from 440 nHz at r = 0.67 to 383 nHz at r = 0.775, with a maximum negative gradient of order 2.4 × 10-3 at r = 0.70 ± 0.01. Models exhibiting a discontinuous shear between the convection zone and a uniformly rotating radiative region are not strongly supported by these data. A model with a uniformly rotating core below r = 0.58 and with some latitudinal structure in the range 0.58 < r < 0.70 is found to be consistent with the data.