Analysis of the emission line spectra of a solar flare observed from Skylab

Skylab observations in the EUV spectra made with the NRL split spectrograph during the Sept. 5, 1973 flare have revealed that chromospheric and transition zone lines were enhanced, especially the allowed lines. Greatest enhancement was noted in the Ni II and P II lines (by a factor of 800). The chromospheric lines maintain their sharp and Gaussian profiles and are not appreciably broadened. The transition zone lines, however, show a red shifted component during the initial phase of the flare. Turbulent downward mass motions are observed, probably due to the imbalance between hot flare plasma (13 x 10 to the 6th K) and cooler plasma (10 to the 5th K). High density is recorded in the transition zone, whose thickness, therefore, is deduced to be small.