The interpretation of C V and O VII emission line ratios in the sun

Using new atomic data for electron impact collision rates, the observed C V and O VII emission line ratios in the solar corona/transition region have been reinterpreted. For C V, the ratio R=I(23S1 → 11S0)/I(23P1 → 11S0) indicates an electron density of 4.5 109 cm-3, while the ratio G=(I(23P1 → 11S0) + I(23S1 → 11S0))/I(21P1 → 11S0) gives an electron temperature of 3.0 105 K, in good agreement with that expected if the region was in steady-state ionization equilibrium. Using the observed ratio R in O VII, one obtains 2.0 109 cm-3 as an upper limit to the electron density, and from G, an electron temperature of 8.0 105K. The temperature derived for O VII, is again in agreement with that expected if the region was in steady-state ionization equilibrium. (orig.)