A. E. Kingston

Observational evidence for non-maxwellian electron energy distributions in the solar transition region

On compare les calculs des forces des raies demissions Si III, qui incluent les distributions denergies des electrons non maxwelliens donnees par Shoub, avec les observations par Skylab de soleil calme et deruptions solaires. Le bon accord semble confirmer lexistence de telles distributions denergies electroniques dans la basse region de transition solaire

Solar Si III line ratios from the high-resolution telescope and spectrograph on board Spacelab 2: the effects of non-Maxwellian electron distribution functions

Les taux dexcitation par impact delectrons pour les transitions dans Si III, incorporant les effets de fonctions de distribution des vitesses electroniques non maxwelliennes, sont presentes pour une etendue des temperatures electroniques appropriees a la region de transition solaire. Une comparaison des rapports de raies theoriques avec les donnees dobservations pour une region calme, une tache solaire, et une region active obtenues avec le spectrometre HRTS a bord de Spacelab 2 indique de ces fonctions non maxwelliennes peuvent exister dans la region de transition

Fe XIV line ratios in the Sun

Recent R-matrix calculations of electron-impact excitation rates for Fe XIV are used to derive theoretical electron density-sensitive emission-line ratios involving transitions in the wavelength range 211-274 A. Electron densities deduced from the observed line ratios for solar flares and active regions, obtained with the Naval Research Laboratorys SO82A slitless spectrograph on board Skylab, are in excellent internal agreement and, furthermore, compare favorably with densities determined independently from line ratios in Fe XII and Fe XIII. These results provide experimental support for the accuracy of the atomic data adopted in the analysis, as well as for the techniques used to calculate the line ratios. 36 refs.

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

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.

S V line ratios in the sun

In the present prediction of level populations and emission line intensity ratios for electron densities and temperatures appropriate to the sun, on the basis of new atomic data for S V, the electron impact collision rates for spin-forbidden transitions and the intercombination transition spontaneous radiative rate are noted to be substantially larger than previously ascertained. The S V intensity ratio is shown to be a useful electron density diagnostic for log N(e) greater than 11.5 ratios deduced from observations obtained with a slit spectrograph aboard Skylab generally agree with the theoretical values presented. 29 references.

The 3s2 3p 2P-3s3p2 4P intercombination lines of Fe XIV in the sun

We have examined EUV spectra of solar flares obtained with the Naval Research Laboratorys S082A slitless spectrograph on board Skylab and provisionally identified the five components of the Fe XIV 3s 2 3p 2 P-3s3p 2 4 P intercombination multiplet. A comparison of the observed Fe XIV line intensities with theoretical predictions reveals good agreement between theory and experiment, which tends to confirm our identifications and those made previously by Trabert, Hutton, and Martinson. The potential usefulness of the lines as electron density diagnostics is briefly discussed

Interspecies emission-line ratios as electron density diagnostics for late-type stellar atmospheres

Electron-impact excitation rates for transitions in S IV, Al III, and N IV, determined with the R-matrix code, are used to calculate relative level populations for electron temperatures log Te = 4.4 - 5.4 and densities Ne between 10 to the 8th and 10 to the 12th/cu cm. These data are combined with similar results for C III and O III to derive emission-line ratios which should be useful as electron-density diagnostics when applied to the UV spectra of late-type stellar atmospheres. 37 refs.

Solar Si II line ratios from the high-resolution telescope and spectrograph

Theoretical emission-line ratios involving multiplets near 1262, 1306, and 1530 A are derived on the basis of new calculations of electron-impact excitation rates for allowed transition in Si II. A comparison of these line ratios with observational data from a quiet solar region, a sunspot, and an active region, obtained with the HIRTS on board a sounding rocket flight reveals that the 1530-A multiplet is optically thick, which is consistent with a calculation of the optical depth of these lines through a model atmosphere. The 1262- and 1306-A multiplets appear to be effectively optically thin. The average discrepancy between the theoretical and observed ratios is about 40 percent, which may not be significant, since the estimated uncertainties in both the calculated and experimental data are approximately 30 percent.

X-RAY EMISSION-LINE RATIOS IN MG-XI AS ELECTRON-TEMPERATURE DIAGNOSTICS FOR SOLAR-FLARES AND ACTIVE REGIONS

Electron impact excitation rates for transitions in helium-like Mg XI, calculated with the R-matrix code, are used to derive the electron temperature-sensitive emission-line ratios G = [I(1s2 1S-1s2s 3S) + I(1s2 1S-1s2p 3P1,2)]/I(1s2 1S-1s2p 1P) = [I(9.314 angstrom) + I(9.232 angstrom)]/I(9.169 angstrom), R1 = I(1s2 1S-1s3p 1P)/I(1s2 1S-1s2p 1P) = I(7.850 angstrom)/I(9.169 angstrom), and R2 = I(1s2 1S-1s4p 1P)/I(1s2 1S-1s2p 1P) = I(7.472 angstrom)/I(9.169 angstrom). These are found to be significantly different from the earlier diagnostic calculations of Keenan, Tayal, & Kingston, and Keenan, Kingston, & McKenzie, and will lead to electron temperature estimates up to a factor of approximately 1.6 larger. Values of T(e) deduced from R1 and R2 ratios measured from solar flare and active region spectra obtained with the Flat Crystal Spectrometer (FCS) on board the Solar Maximum Mission (SMM) satellite are consistent, and furthermore are in good agreement with temperatures estimated from the observed G ratios for these solar features. This provides support both for the validity of the theoretical R1 and R2 diagnostics, and for the FCS calibration curve in the wavelength region covering the Mg XI transitions, 7.472-9.314 angstrom.