Theoretical emission line ratios for O vii in low-density plasmas
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- Keenan, F.P., Tayal, S.S. & Kingston, A.E. Sol Phys (1984) 92: 75. doi:10.1007/BF00157236
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New electron excitation rates for O vii calculated by Tayal and Kingston using the R-matrix method are used to determine theoretical emission line strengths. Values of the electron density sensitive ratio R (forbidden line to intercombination line) are found to be very similar to those deduced by other authors. However the temperature sensitive ratios G (intercombination plus forbidden lines to resonance line) are approximately 20% lower than the best previous estimates. The observed value of G for solar active regions (G = 1.0 ± 0.1) predicts an electron temperature in the range 1.1 × 106 K < Te < 1.8 × 106 K, which overlaps that of maximum O vii emissivity, TM = 1.8 × 106 K. In addition, the theoretical G versus Te curve is in excellent agreement with that observed for a Tokamak plasma.