AR(XIII) LINE RATIOS IN SOLAR-FLARES

Theoretical Ar XIII electron-density-sensitive emission line ratios, d erived using electron impact excitation rates interpolated from accura te R-matrix calculations, are presented for R1 = I(242.22 angstrom)/I( 236.27 angstrom), R2 = I(210.46 angstrom)/I(236.27 angstrom), and R3 = I(248.68 angstrom)/I(236.27 angstrom). Electron densities deduced fro m the observed values of R1, R2, and R3 for solar flares obtained with the NRL S082A slitless spectrograph on board Skylab are in excellent agreement, and furthermore compare favorably with those determined fro m line ratios in Ca XV, which is formed at a similar electron temperat ure to that of Ar XIII. These results provide experimental support for the accuracy of the atomic data adopted in the analysis, as weil as f or the techniques used to calculate the line ratios.