EMISSION-LINE RATIOS FOR FE XXI APPLICABLE TO THE XUV SPECTRA OF SOLAR-FLARES

Electron impact excitation rates for Fe XXI, calculated with the R-mat rix code, are used to determine theoretical electron density sensitive emission line ratios involving transitions in the 121-146 angstrom wa velength range. The observed ratios for a solar flare, obtained with a grazing spectrometer on board the OSO-5 satellite, imply electron den sities which are consistent, with discrepancies that do not exceed 0.3 dex. In addition, the derived values of N(e) are similar to those est imated for the high temperature regions of other solar flares. This pr ovides experimental support for the accuracy of the atomic data adopte d in the line ratio calculations.