Fraunhofer lines in the transition from the center to the limb of the solar disk

1Osipov, SN, 1Vasilieva, IE
1Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2019, 35(2):50-64
Start Page: Solar Physics
Language: Russian

The two-dimensional spectrа of the Sun (from the center to the limb of the disk) in sections = 532.0...532.8 and 539.1...539.9 nm were recorded at the ATsU-5 telescope of the National Academy of Sciences of Ukraine by replacing the regular main mirror with a short-focus one (with a focal length of 1 m). The advantage of the applied method is the simultaneity of spectrum recording for different heliocentric positions of the solar disk. The reductions of observational data for the influence of scattered light in the spectrograph, atmospheric stray light, instrumental contour of the spectrograph, and some aberrations were carried out. The center/limb spectral relations are compared with the available literature data. Data on variations of spectral line profiles in the transition from the center to the limb of the solar disk are obtained for 11 spectral lines. The revealed non-monotony of such changes is explained by inhomogeneities of physical conditions on the surface of the Sun. In general, the depths of the studied Fe I lines demonstrate a tendency to decrease the strength of the lines when going to the limb. The line full widths at half maximum of most lines increase to the limb of the disk. Equivalent widths show differently directed variation. Changes of the parameters of the Mn I 539.4 nm line stand out from the general row: all three parameters studied grow to the edge of the disk, although at the extreme limb the depth and equivalent width also begin to decrease. Measured limb-effect of lines de­monstrates the highest value when comparing the positions of the core of weak lines. Strong lines show the maximum limb effect when comparing the middle part of the bisectors.

Keywords: бисектор, лимб-эффект, потемнение к краю, Солнце, спектральные линии, фотосфера

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