V. J. Foster

Fe x Emission Lines in Solar and Stellar Spectra

Theoretical electron density sensitive emission line ratios involving Fe x 3s23p5 − 3s23p43d transitions in the 170-190 A wavelength range are compared with observational data for a solar active region and flares, obtained during the Skylab mission, and α 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 are 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.

Extreme ultraviolet line ratios for Ca XV applicable to solar flare spectra

New R-matrix calculations of electron impact excitation rates in Ca XV are used to derive theoretical electron density diagnostic emission-line ratios involving 2s 2 2p 2 -2s2p 3 transitions in the wavelength range ∼180-215 A. A comparison of these with observational data for solar flares obtained with the Naval Research Laboratorys S082A spectrograph on board Skylab reveals excellent agreement between theory and observation, as does a comparison with line ratio measurements from the TEXT tokamak plasma, for which the electron temperature and density have been independently determined

Identification of the Fe xv 3s3p 1P-3p2 1S line in solar flare spectra and its use as an electron density diagnostic

We have examined EUV spectra of solar flares obtained with the Naval Research Laboratorys S082A slitless spectrograph on board Skylab, and measured the intensities of the 324.97 A and 323.57 A emission lines relative to that of the Fe XV 3s3p 3 P 2 -3p 2 3 P 1 transition at 321.76A. A comparison of these line ratios with theoretical predictions indicates that the Fe XV 3s3p 1 P-3p 2 1 S transition is the line observed at 324.97 A, rather than the feature at 323.57 A as previously suggested. In addition, we show that the I(324.97 A)/I(321.76 A) intensity ratio is an excellent electron density diagnostic for the Fe XV emitting region of the solar atmosphere

Mg VIII DIAGNOSTIC LINE RATIOS IN SKYLAB SOLAR OBSERVATIONS

Recent calculations of Mgviii electron and proton impact excitations rates are used to derive theoretical electron temperature (Te)- and density (Ne)-sensitive emission line ratios involving transitions in the 315–782 Å wavelength range. Some of these ratios are presented in the form of ratio–ratio diagrams, which should in principle allow both Ne and Te to be deduced. These results are compared with solar observational data from Skylab, but agreement between theory and observation is very poor, probably due to blending.

S XI line ratios in the sun

Theoretical S XI electron density sensitive emission-line ratios are presented for R 1 =I(2s 2 2p 2 1 D-2s 2 p 3 1 D)/I(2s 2 2p 2 3 P 2 -2s 2 p 3 3 s)=I(215.97 A)/I(191.29 A) and R 2 =I(2s 2 2p 1 1 D-2s2p 3 1 P)/I(2s 2 2P 2 3 P 2 -2s2p 3 3 S)=I(150.37 A)/I(151.25 A)

Fe XXI emission line ratios as electron temperature diagnostics for the coronae of cool stars

AbstractTheoretical Fe xxi electron temperature and density sensitive emission line ratios are presented for

EMISSION LINES OF Ni XVIII IN THE SOLAR EUV SPECTRUM

R_1 = I\left( {2s^2 2p^2 {}^3P_1 - 2s2p^3 {}^5S} \right)/I\left( {2s^2 2p^2 {}^3P_0 - 2s^2 2p^2 {}^3P_1 } \right)

Skylab Observations of Temperature and Density Sensitive Emission Line Ratios in Ne VI

and