EUV spectra from skylab (1175-1940 A)

The profiles of spectral lines in the 1100-2000 A range emitted by transition zone ions (approximately 105 K) in regions of solar activity are discussed. The data were recorded by the NRL spectrograph on Skylab. At the spatial resolution of the Skylab spectrograph (2'' x 60''), it is shown that the line profiles result from the superposed emission of a number of physically distinct regions at different electron densities and with different mass motions. Although high densities (>1012 cm-3) are found for some surge-like phenomena at transition zone temperatures, the densities can also be comparable to normal active region densities (approximately 1011 cm-3). Line profiles, as well as spectral line intensities, must be considered if meaningful theoretical models of dynamic activity in the transition zone are to be constructed. (orig.)