Estimates of the Solar Internal Angular Velocity Obtained with the MT. Wilson 60-Foot Solar Tower

Abstract

We have obtained estimates of the solar internal angular velocity from measurements of the freguency splittings of p-mode oscillations. Specifically, we have analyzed a 16-day time series of full-disk Dopplergrams obtained during July and August 1984 at the 60-Foot Tower Telescope of the Mt. Wilson Observatory. From this time series we computed power spectra for all of the zonal, tesseral, and sectoral p-modes from ℓ = 0 to 89 and for all the sectoral p-modes from ℓ = 90 to 200. We next calculated a mean power spectrum for each degree up to 89 and then computed the frequency differences of all of the different non-zonal modes from these mean power spectra. The resulting freguency-difference curves for ℓ = 1 to 89 were then expanded as a series of Legendre polynomials. For the odd-order terms in these expressions our results agreed reasonably well with the earlier results of Duvall, Harvey, and Pomerantz¹. Next we combined the odd-order expansion coefficients into estimates of the solar internal equatorial rotational freguency splitting. We checked these estimates by similarly combining the published coefficients of Duvall, Harvey, and Pomerantz. We also compared our estimates with the earlier results of Hill and his colleagues at SCLERA. Our comparisons showed reasonably close agreement with the Duvall, Harvey, and Pomerantz results but sharp disagreement with SCLERA results.