Applications of Fourier analysis to broadening of stellar line profiles. III - Solar microturbulence and macroturbulence from iron lines

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Kitt Peak solar profiles of iron lines obtained at ..mu.. = 0.63 were utilized to study the solar velocity field. The high quality of these data and the lack of influence of rotation make possible a modeling of the macroturbulent velocity distribution as well as a determination of the microturbulence. The analysis was performed by matching computed and observed criteria in both the wavelength and the Fourier transform domains. The principal ambiguities in evaluating microturbulence are caused by the uncertainty in the functional form of macroturbulence and in the value of the atomic damping constants. The form of the first sidelobe in the data transforms indicates the existence of a low (/sup 1///sub 4/ +- /sup 1///sub 4/ km s/sup -1/) microturbulence at intermediate photospheric regions which increases toward larger depths. Attempts were made to fit profiles with macroturbulences of a wide variety of functional forms. In the wavelength representation the Voigt distribution gives the best overall fit, whereas in the transform domain an exponential function matches the observed sidelobe best. A comparison of all the results shows only a small disparity in best-fit parameters around a mean of 2.0 km s/sup -1/. A triangular macrovelocity distribution which is similarmore » to that predicted by a radial-tangential model is recovered explicitly by deconvolution. However, for practical reasons a good one-parameter fit to it is provided by the exponential function. Because this function is very dissimilar to the rotation function, it should be possible to evaluate macroturbulence and rotation separately in sharp-lined late-type stars.« less