HEIGHTS OF FORMATION OF FE-I PHOTOSPHERIC LINES

The determination of the location of spectral line-forming layers by m eans of line-depression contribution functions is checked by observati onal tests. The method is based on the assumption that the Doppler vel ocities derived from line bisectors at a given position in the profile of a spectral line are related to the actual bulk velocity at a parti cular height in the atmosphere. For a set of six magnetically sensitiv e and nonsensitive Fe I lines (543.45, 557.61, 630.15, 630.25, 649.50, 649.45 nm) the fluctuations of Doppler velocities along the slit of t he spectrograph were determined at various Delta lambda from the line centers i.e. at various heights in the photosphere. Correlations of fl uctuations allow us to find those parts in line profiles which are for med at identical heights in the photosphere. These experimental result s are compared with theoretical estimates based on fine depression con tribution functions. The agreement is good and best results are found for nonmagnetic strong, but still unsaturated lines. The results suppo rt the hypothesis that it is possible to ascribe a single height point in the solar atmosphere to a given position in a spectral line profil e.