Flare-related changes in the profiles of six photospheric spectral lines

Abstract

The profiles of six photospheric absorption spectral lines (Fe i 5250 A, Fe i 5324 A, Fe i 5576 A, Ca i 5590 A, Ca i 6103 A and Fe i 6165 A), measured in the kernel of a 2N solar flare and in a quiet-Sun area, were compared. The observations were carried out with an echelle spectrograph of the Crimean Astrophysical Observatory. It was shown that, compared to the quiet-Sun profiles, the flare profiles are shallower in the line core and are less steep in the wings. Therefore, measurements of the longitudinal magnetic field made with a magnetograph system which uses the Ca i 6103 A spectral line, can be underestimated by 18–25% in areas of bright Hα ribbons of a moderate solar flare. Modeling of the solar photosphere performed by using a synthesis method showed that, in a solar flare, the enhanced core emission seems to be related to heating of the photosphere by the flare, whereas the decrease of the slope of the wings was presumably caused by the inhomogeneity of the photospheric magnetic field.