Abstract
The electron collision excitation rates recently calculated for transitions in Si xiii by Keenan et al. (1987) are used to derive the electron temperature sensitive ratio G(=(f + i)/r and the density sensitive ratio R(=f/i), where i, f, and r are the intercombination (1s 2 1 S − 1s2p 3 P 1, 2) forbidden (1s 2 1 S − 1s2s 3 S), and resonance (1s 2 1 S − 1s2p 1 P), transitions respectively. Also estimated are the values of R in the low-density limit (R 0) as a function of electron temperature. The theoretical G ratio at the temperature of maximum emissivity for Si xiii, G(T m) = 0.70, is in much better agreement with the observed G for the 1985, May 5 flare determined by McKenzie et al. (G = 0.60 ± 0.07) than is the earlier calculation of Pradhan, who derived G(T m) = 0.85. The error in the observed R 0 ratio is so large that both our result and Pradhan's fall within the acceptable limits of uncertainty and hence one cannot estimate which of the two is the more accurate.
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McCann, S.M., Keenan, F.P. Theoretical emission line ratios for Si XIII compared to solar observations. Sol Phys 112, 83–88 (1987). https://doi.org/10.1007/BF00148489
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DOI: https://doi.org/10.1007/BF00148489