CA X Line Ratios in Solar Flares

Theoretical Ca X electron temperature sensitive emission line ratios, derived using electron excitation rates interpolated from accurateR-matrix calculations, are presented forR ₁ =I(419.74 Å)/I(574.02 Å,),R ₂ =I(411.65 Å)/I(574.02 Å),R ₃ =I(419.74 Å)/I(557.75 Å), andR ₄ =I(411.65 Å)/I(557.75 Å). A comparison of these with observational data for three solar flares, obtained by the Naval Research Laboratory's S082A slitless spectrograph on boardSkylab, reveals good agreement between theory and observation forR ₁ andR ₃ in one event, which provides limited support for the accuracy of the atomic data adopted in the analysis. However, in the other flares the observed values ofR ₁ R ₄ are much larger than the theoretical high-temperature limits, which is probably due to blending of the 419.74 Å line with C iv 419.71 Å, and 411.65 Å with possibly C iii 411.70 Å.