Spectral analysis of sunspot flares

摘要

We have qualitatively analyzed, in the H and K lines spectral region, 31 flares covering part of umbrae or penumbrae of sunspots. A strong narrowing of the emission lines has been observed over the umbrae, and the lines are, in general, much weaker than in common flares suggesting that the optical thickness is quite low in these parts. We have calculated the Stark broadening of the Hɛline from the general theory, and it has been applied to obtain the electron density in 9 flare spectra. In all cases it has been found thatne>1013cm−3. Goldberg's method has been applied to find the kinetic temperature from the H and K lines of Caii, and from the ratio between the central intensities of the lines we have calculated the optical thickness in the K line. Much evidence supports the assumption that the flare emission is highly dilutedThe term ‘dilution’ has been used with the same meaning as in Švestka's (1972) paper, i.e., the case when the integrated flare area is not completely covered by the flare elements.in the cases considered, and we propose a two-component model for the calcium emissio