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V.J. Foster, M. Mathioudakis, F.P. Keenan, J.J. Drake, and K.G. Widing
Theoretical electron density sensitive emission line ratios involving Fe X 3s^2 3p^5 - 3s^2 3p^4 3d transitions in the 170-190 A wavelength range are compared with observational data for solar active regions and flares, obtained during the Skylab mission, and alpha Cen and Procyon observations from the Extreme Ultraviolet Explorer (EUVE) satellite. Electron densities derived from the majority of the ratios are consistent for the events, but in poor agreement with the values of Ne estimated from diagnostic lines in other species observed in the spectra, casting doubt on the accuracy of the theoretical line ratio calculations and hence the atomic data of Mohan et al. used in their derivation. At low Ne, the present ratios are significantly different from those of Young et al., while the latter imply densities that are in somewhat better agreement with densities derived from other diagnostics. This would appear to indicate that the electron impact excitation rates of Bhatia & Doschek adopted by Young et al. are to be preferred over the Mohan et al. results.
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