Theoretical emission line intensity ratios for NE ^44^Sc VI compared to EUV solar observations.

Recent calculations of electron and proton impact excitation rates in Ne ^44^Sc VI are used to derive the intensity ratios of lines in the ~402-1006A wavelength range as a function of electron temperature (T_e_) and density (N_e_). These results are presented in the form of ratio-ratio diagrams, which should in principle allow both N_e_ and T_e_ to be deduced for the Ne ^44^Sc VI line emitting region of a plasma. Electron temperatures and densities derived from ratio-ratio diagrams involving the 562.7, 997.4, 999.6 and 1006.1A lines, in conjunction with observational data for a sunspot obtained with the Harvard S-055 spectrometer on board Skylab, are found to be compatible, and in good agreement with plasma parameters determined using other methods. This provides some support for the diagnostic calculations presented in this paper, and hence the atomic data used in their derivation. However agreement between theory and observation is very poor for other Ne ^44^Sc VI lines in the sunspot spectrum, and for most transitions observed in S-055 active region and flare data, which is probably due to blending with lines from N ^44^Sc III, Mg ^44^Sc VI and Mg ^44^Sc VII.