K. G. Widing

The Fe XIV spectrum: Predicted line intensities and solar identifications

Level populations and line intensities have been calculated in a 40-level model of Fe XIV which includes the configuations 3p(exp 3) and 3s3p3d. The results have been compared against intensities of weaker, unidentified, or tentatively classified lines in published solar line lists including a recent Goddard Space Flight Center/Solar Extreme Ultraviolet Telescope and Spectrograph (GSFC/SERTS) high-resolution list, and in presently measured archival Naval Research Laboratory (NRL)/S082A active region spectra. Seven new lines are identified as Fe XIV transitions; five other observed, unidentified lines are considered to be Fe XIV transitions on the basis of wavelength coincidence, but require further observations to obtain photometric intensities for verification; one line at 216.93 A is shown to be due to some other ion than Fe XIV. In addition, a unique forbidden infrared (approx. equal to 1.25 micrometer(s)) line originating in the high metastable level 3s3p3d(F(sub 9/2)-4) is found to have an unusual intensity dependence on electron density.

Coronal element comparison observed by SOHO SUMER in the quiet southeast and northwest limb regions at 1.04 R○. above the solar disk

The composition in an isothermal region at 1.04 R☉ above a diffuse, quiet coronal region on the northwest limb is studied and compared with a similar region above the southeast limb analyzed by Warren in 1999. Elemental abundances relative to H in the corona are measured and normalized to the abundance ratios in the photosphere. The enrichment factors of the low first ionization potential elements are comparable above both limbs, but are significantly smaller than the factor of 4 in SUMER spectra obtained 2 years earlier at solar minimum in a diffuse, quiet equatorial region.

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-IX LINE RATIOS IN THE SUN

Theoretical Mg IX electron density sensitive emission-line ratios, derived using electron impact excitation rates interpolated from accurate R-matrix calculations, are presented for R1 = I(443.97 angstrom)/(368.07 angstrom), R2 = I(439.17 angstrom)/I(368.07 angstrom), R3 = I(368.07 angstrom)/I(443.07 angstrom), and R4 = I(441.20 angstrom)/I(368.07 angstrom). 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 for R1 and R2, which confirms the usefulness of these ratios as N(e)-diagnostics for solar flares, as well as providing experimental support for the accuracy of the atomic data adopted in the line ratio calculations. However the observed values of both R3 and R4 generally imply unrealistically high electron densities, which is probably due to blending in the 443.40 and 441.20 angstrom lines, probably with Ar IV 443.44 angstrom and Mg VI/Mg VII 441.22 angstrom, respectively.

Improved line ratio calculations involving delta-n = 1 (2-3) transitions in O V and a reanalysis of SKYLAB observations of solar flares

New R-matrix calculations of electron impact excitation rates in O v are used to rederive theoretical electron density diagnostic emission-line ratios involving transitions between the n = 2 and 3 levels, which includes lines at 192.80, 192.90, 215.10, 215.25, 220.35, and 248.46 angstrom. A comparison of these diagnostics with observational data for two solar flares obtained with the Naval Research Laboratorys S-082A spectrograph on board Skylab reveals better agreement between theory and observation than was found previously. This provides experimental support for the improved accuracy of the atomic data employed in the present analysis.

Extreme-Ultraviolet Emission Lines of S X in Solar Flare and Active Region Spectra

R-matrix calculations of electron impact excitation rates in N-like S X are used to derive theoretical emission-line intensity ratios involving 2s22p3-2s2p4 transitions in the 189-265 A wavelength range. A comparison of these with observational data for solar flares and active regions, obtained with the Naval Research Laboratorys S082A spectrograph on board Skylab and the Solar EUV Rocket Telescope and Spectrograph, reveals that many of the S X lines in the spectra are badly blended with emission features from other species. However, the intensity ratios I(228.70 A)/I(264.24 A) and I(228.70 A)/I(259.49 A) are found to provide useful electron density diagnostics for flares, although the latter cannot be employed for active regions, because of blending of the 259.49 A line with an unidentified transition in these solar features.

C IV line ratios in the sun

Recent R-matrix calculations of electron impact excitation rates for transitions in C IV are used to derive the theoretical electron temperature-sensitive emission-line ratios R1 = I(312.43 angstrom)/I(419.74 angstrom), R2 = I(3 84.14 angstrom)/I(419.74 angstrom), R3 = I(312.43 angstrom)/I(419.49 angstrom), and R4 = I(384.14 angstrom)/I(419.49 angstrom). A comparison of these with solar observational data obtained with the Naval Research Laboratorys S082A slitless spectrograph on board Skylab reveals good agreement between theory and observation for R2 and R4, which provides experimental support for the accuracy of the atomic data adopted in the analysis. However, most of the observed values of R1 and R3 lie above the theoretical high-temperature limit, which is probably due to blending of the 312.43 angstrom line.

Calcium-to-Argon and Nickel-to-Argon Abundance Ratios as Tracers of the Source Region of Postflare Loop System Material

Intensities of abundance diagnostic lines of Ca XV, Ca XVI, Ni XVII, Ar XIII, and Ar XV have been derived for a classic flare loop system observed during the Skylab mission. These have been used to test for photospheric or coronal origin of the flare loop material. The resulting FIP-bias factors are between 1.7 and 4.6 with a majority of the values around 4.5 indicating a source with material modified by the FIP effect. The loop system bias factors are similar to those observed in a sample of Skylab prominences, suggesting that the disrupted mass of the preflare embedded filament provided the loop system material.

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)