EMISSION-LINE RATIOS FOR SI-XI APPLICABLE TO CDS SUMER OBSERVATIONS FROM SOHO/

Calculations of electron temperature (T-e) and density (N-e) sensitive line ratios in Si XI involving transitions in the similar to 358-604 Angstrom wavelength range are presented. These are shown in the form o f ratio-ratio diagrams, which should in principle allow both N-e and T -e to be deduced for the Si XI line-emitting region of a plasma. Howev er a comparison of these with observational data for two solar flares, obtained with the Naval Research Laboratory's S082A spectrograph on b oard Skylab, reveals that the experimental ratios are much larger than expected from theory, which is probably due to the Si XI lines in the S082A spectra being blended with transitions from species including N e V, Fe XI, and Fe XII. Possible future applications of the Si XI resu lts to spectral data from the Coronal Diagnostic Spectrometer on the S olar and Heliospheric Observatory are briefly discussed.