HELIUM-LIKE ARGON LINE EMISSION IN SOLAR-FLARES

Theoretical X-ray spectra of Ar XVII lines and Ar XVI satellites at ap proximately 4 angstrom, derived from R-matrix code and other calculati ons, are compared with solar-flare observations obtained with the SMM Flat Crystal Spectrometer. There is good agreement between the observe d line features and those in the theoretical spectra, and the comparis on leads to best-fit values of electron temperature for the observed s olar flares. We present wavelengths for the Ar XVII and some Ar XVI li nes, measured from the observed spectra, which have better precision t han previous values. In addition, the coronal Ar/S abundance is determ ined from the relative intensities of Ar XVII lines to those of nearby S XV transitions, and the value of this ratio is discussed in the lig ht of previous work.