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1.
Theoretical electron-density-sensitive C III emission line ratios are presented for R
1 = I(2 s2 p
3
P – 2 p
2
3
P)/ I(2 s2 p
1
P – 2 p
2
1
S) = I(1176 Å)/ I(1247 Å), R
2 = I(2 s2 p
3
P – 2 p
2
3
P)/ I(2 s
2
1
S – 2 s2 p
3
P
1) = I(1176 Å)/ I(1908 Å), and R
3 = I(2 s2 p
1
P – 2 p
2
1
S)/ I(2 s
2
1
S – 2 s2 p
3
P
1) = I(1247 Å)/ I(1908 Å). These are significantly different from those deduced previously, principally due to the adoption of improved electron impact excitation rates in the present analysis. Electron densities deduced from the present theoretical line ratios, in conjunction with observed values of R
1, R
2, and R
3 measured from solar spectra obtained by the Naval Research Laboratory's S082B instrument on board Skylab, are found to be generally compatible. In contrast, previous diagnostic calculations imply electron densities from R
1, R
2, and R
3 that differ by up to two orders of magnitude. These results provide observational support for the accuracy of the atomic physics adopted in the present calculations, and the methods employed in the derivation of the theoretical line ratios. 相似文献
2.
New R-matrix calculations of electron impact excitation rates in Caxv are used to derive theoretical electron density diagnostic emission line intensity ratios involving 2 s
22 p
2–2 s2 p
3 transitions, specifically R
1= I(208.70 Å)/ I(200.98 Å), R
2= I(181.91 Å)/ I(200.98 Å), and R
3= I(215.38 Å)/ I(200.98 Å), for a range of electron temperatures ( T
e=10 6.4–10 6.8 K) and densities ( N
e=10 9–10 13 cm –3) appropriate to solar coronal plasmas. Electron densities deduced from the observed values of R
1, R
2, and R
3 for several solar flares, measured from spectra obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab, are found to be consistent. In addition, the derived electron densities are in excellent agreement with those determined from line ratios in Caxvi, which is formed at a similar electron temperature to Caxv. These results provide some experimental verification for the accuracy of the line ratio calculations, and hence the atomic data on which they are based. A set of eight theoretical Caxv line ratios involving 2 s
22 p
2–2 s2 p
3 transitions in the wavelength range 140–216 Å are also found to be in good agreement with those measured from spectra of the TEXT tokamak plasma, for which the electron temperature and density have been independently determined. This provides additional support for the accuracy of the theoretical line ratios and atomic data. 相似文献
3.
Using electron excitation rates calculated with the R-matrix code, theoretical Nixviii electron-temperature-sensitive emission line ratios are presented for R
1 = I(220.41 Å)/ I(320.56 Å) , R
2 = I(233.79 Å)/I(320.56 Å) , and R
3 = I(220.41 Å)/ I(292.00 Å) . A comparison of these with observational data for two solar flares, obtained by the Naval Research Laboratory's S082A slitless spectrograph on board Skylab, reveals good agreement between theory and observation for R
1 and R
2 in two spectra, which provides limited support for the accuracy of the atomic data adopted in the analysis. However, several of the measured ratios are much larger than theory predicts, which is probably due mainly to saturation of the strong 292.00 and 320.56 Å lines on the photographic film used to record the S082A data. A comparison of our line ratio calculations with active region observations made by the Solar EUV Rocket Telescope and Spectrograph (SERTS) indicate that a feature at 236.335 Å, identified as the Nixviii 3 p
2
P
3/2 - 3 d
2
D
3/2 transition in the SERTS data, is actually the Arxiii 2 s
22 p
2
3
P
0 - 2 s2 p
3
3
D
1 line. The potential usefulness of the Nixviii line ratios as electron temperature diagnostics for the solar corona is briefy discussed. 相似文献
4.
Electron impact excitation rates for transitions in the S v ion, calculated with the R-matrix code, are used to derive the electron temperature sensitive emission line ratios R
1 = I(854.8 Å)/ I(786.9 Å), R
2 = I(852.2 Å)/ I(786.9 Å), R
3 = I(849.2 Å)/ I(786.9 Å), and R
4 = I(1199.1 Å)/ I(786.9 Å), which are found to be significantly different from previous estimates. A comparison of the present results with observational data for a sunspot obtained with the Harvard S-055 spectrometer on board Skylab reveals generally good agreement between theory and experiment, except in the case of R
1, which is probably due to blending in the 854.8 Å feature. The possible effects of Lyman continuum absorption on the observed line ratios is briefly discussed. 相似文献
5.
Relative level populations in Oiii, determined using R-matrix calculations of electron impact excitation rates, are used to derive the theoretical emission line ratios R
1 = I(525.80 Å)/ I(599.62 Å), R
2 = I(507.41 Å)/ I(599.62 Å), R
3 = I(507.71 Å)/ I(599.62 Å), and R
4 = I(508.18 Å)/ I(599.62 Å). Electron temperatures deduced from the observed values of these ratios for several solar features obtained with the NRL S082A slitless spectrograph on board Skylab are in good agreement, and also compare favourably with that of maximum Oiii fractional abundance in ionisation equilibrium, log T
max = 4.96. These results provide experimental support for the accuracy of the atomic data adopted in the line ratio calculations. 相似文献
6.
The recent twelve-state R-matrix calculations of electron excitation rates in C iii by Berrington are used to derive level populations applicable to the solar transition region. Line ratios R = I(2 p
2 3
P
e
- 2 s2 p
3
P
°)/ I(2 s2 p
1
P
° - 2 s
2 1
S
e
) and R
2= I(2 p
2 1
S
e
- 2 s2 p
1
P
°)/ I(2 p
2 3
P
e
- 2 s2 p
3
P
°) deduced from these data in conjunction with the relevent transition probabilities are found to be in much better agreement with the observed quiet Sun values than those determined from the level population calculations of Keenan et al. 相似文献
7.
Theoretical electron-temperature-sensitive Ne vii emission line ratios, calculated using accurate R-matrix electron impact excitation rates, are presented for R
1 = I(895.2 Å)/ I(465.2 Å), R
2 = I(561.7 Å)/ I(465.2 Å) and R
3 = I(564.5 Å)/ I(465.2 Å). A comparison of these with observational data for several solar features obtained with the Harvard S-055 spectrometer on board Skylab reveals good agreement between theory and experiment. This provides observational support for the accuracy of the atomic physics adopted in the calculations, and the methods employed in the derivation of the theoretical diagnostics. 相似文献
8.
Theoretical N iv emission line ratios, which incorporate several improvements over previous estimates, are presented for R
1 = I(923.2 Å)/ I(765.1 Å) and R
2 = I(1718.6 Å)/ I(1486.5 Å), which are electron density and temperature sensitive, respectively. A comparison of R
1 with observational data for several solar features obtained with the Harvard S-055 spectrometer on board Skylab reveals generally good agreement between theory and observation, except for the quiet Sun, which is probably due to the 923.2 Å line being blended with an Fe iii transition in this instance. The observed value of R
2, determined from a quiet-Sun spectrum obtained by the S082-B spectrograph on board Skylab, implies an electron temperature in excellent agreement with that of maximum N iv fractional abundance in ionisation equilibrium, which provides observational support for the accuracy of the diagnostic calculations. 相似文献
9.
The electron collision excitation rates recently calculated for transitions in Si xiii by Keenan et al. (1987) are used to derive the electron temperature sensitive ratio G(=(f + i)/r and the density sensitive ratio R(=f/i), where i, f, and r are the intercombination (1 s
2
1
S – 1 s2 p
3
P
1, 2) forbidden (1 s
2
1
S – 1 s2 s
3
S), and resonance (1 s
2
1
S – 1 s2 p
1
P), transitions respectively. Also estimated are the values of R in the low-density limit ( R
0) as a function of electron temperature. The theoretical G ratio at the temperature of maximum emissivity for Si xiii, G( T
m) = 0.70, is in much better agreement with the observed G for the 1985, May 5 flare determined by McKenzie et al. ( G = 0.60 ± 0.07) than is the earlier calculation of Pradhan, who derived G( T
m) = 0.85. The error in the observed R
0 ratio is so large that both our result and Pradhan's fall within the acceptable limits of uncertainty and hence one cannot estimate which of the two is the more accurate. 相似文献
10.
Results are presented for several theoretical line ratios in Nev involving transitions between multiplets in the 2 s
22 p
2 and 2 s2 p
3 configurations. A comparison of these with solar data from the S082A and S-055 instruments on board Skylab reveals generally good agreement between theory and experiment, especially in the case of the high-resolution (S082A) observations. However the 2 s
22 p
2
1
D – 2 s2 p
3
1
P (365.6 Å) and 2 s
22 p
2
3P – 2 s2 p
3
3
S (359 Å) lines appear to be blended, possibly with transitions in Fex and Fe xi/Fe xiii, respectively. We note that the intensity ratio I(365.6 Å) /I(416.2 Å) should be a valuable calibration check for a high-resolution extreme ultraviolet instrument in the spectral range 360–420 Å. 相似文献
11.
R-matrix calculations of electron impact excitation rates in 0 III are used to derive the electron-density-sensitive emission-line
ratio R = 1 (2 s
2 2 p
23
P
2-2 s
2
2P
23
P
1)/ I (2 s
22 p
23
P
1 - 2 s
22 p
23
P
0) = I (52μm)/ I (88μm) for a range of electron temperatures (Te = 5000-20000 K) and densities (N
e
= 10–10
5
cm −3) applicable to planetary nebulae. Electron densities deduced from the observed values of R in several planetary nebulae are in excellent agreement with those deduced from C1 I and Ar IV, which provides support for
the accuracy of the atomic data adopted in the calculations. 相似文献
12.
New theoretical electron temperature sensitive emission line ratios in Si iv involving the 3 d
2
D – 3 p
2
P and 4 s
2
S – 3 p
2
P multiplets at 1125 and 816 Å, respectively, are derived using recent R-matrix electron excitation rate calculations. A comparison of these with observational data for a solar active region at the limb obtained with the Harvard S-055 spectrometer on board Skylab reveals that there is good agreement between theory and observation for ratios that include the 2
D
3/2, 5/2 – 2
P
3/2 transition at 1128.3 Å. This is in contrast to the findings of Keenan, Dufton, and Kingston (1986) and provides support for the atomic data adopted in the calculations. However, the 2
D
3/2 – 2
P
1/2 line at 1122.5 Å appears to be severely blended, as suggested previously by Burton and Ridgeley (1970) and Feldman and Doschek (1977), as it leads to electron temperature estimates that differ significantly from that expected in ionisation equilibrium. The fact that the I(1122.5 Å)/ I(1128.3 Å) intensity ratios determined from several flare spectra are closer to theory than that for the active region indicates that the blending is probably due to species with relatively low ionization potentials, as noted by Flower and Nussbaumer (1975). Electron temperatures deduced for a sunspot are much lower than that predicted from ionisation balance calculations, in agreement with earlier results, and imply that a cooling flow may be present. 相似文献
13.
The recent level population calculations for Ne v by Aggarwal are used to determine the theoretical emission line ratios R
1 = I( 2s2p
3
1D o - 2s 22p 2
1D e)/I(2s2p 3
3D
2
0
- 2s 22p 2
3P
1
e
) and R
2 = I( 2s2p
3
1D o-2s 22p 2
1D e)/ I( 2s2p
3
3D
3
0
-2s 22p 2
3P
2
e
). A comparison of these with observational data for a solar flare and erupting prominence obtained with the NRL XUV spectrograph on board Skylab reveals that R
1 and R
2 are in their predicted high density limits. Although the ratios cannot be used as density diagnostics for values of n
e typical of the solar transition region, it is shown that they are temperature sensitive and hence may be employed to determine the electron temperatures of Ne v line emitting regions. 相似文献
14.
R-matrix calculations of electron impact excitation rates for transitions in Si iii are used to derive the electron-density-sensitive emission line ratios R
1 = I(1113.2 Å)/ I(1206.3 Å), R
2 = I(1298.9 Å)/ I(1206.3 Å), and R
3 = I(1296.7 Å)/ I(1206.3 Å). A comparison of these with observational data for several solar features obtained with the Harvard S-055 spectrometer on board Skylab reveals that theory and experiment are compatible if the electron temperature of the Si iii emitting region of the solar atmosphere is log T
e
= 4.5, but not if log T
e
= 4.7. The implication of the choice of a lower temperature on the electron energy distribution function is also briefly discussed. 相似文献
15.
Recent R-matrix calculations of electron excitation rates for Mg vii and Si ix are used to determine the theoretical density sensitive emission line ratios R
1= I( 2s2p
3
1
D
0 - 2s
2
2p
2
1
D
e
)/ I( 2s2p
3
3
S
0 - 2s
2
2p
2
3
P
2
e
) and R
2= I( 2s2p
3
1
P
0 - 2s
2
2p
2
1
D
e
)/ I( 2s2p
3
3
S
0 - 2s
2
2p
2
3
P
2
e
). These are found to be quite similar to the earlier results of Mason and Bhatia. Electron densities derived using observed R
1 and R
2
ratios from Skylab NRL XUV spectra of solar flares and active regions are in good agreement, and compare favourably with those deduced from ions formed at similar electron temperatures to Mg vii and Si ix. 相似文献
16.
New theoretical emission line ratios for the Be-sequence ions Mg ix and Si xi are presented. A comparison with observational data for two solar flares and an active region loop obtained with the Harvard EUV spectrometer and NRL XUV spectroheliograph aboard Skylab reveals that these plasmas are in ionization equilibrium at coronal temperatures. Unfortunately most of the density diagnostics are not particularly useful under solar plasma conditions, as they vary only slightly over the electron density range 10 8–10 13cm –3. However the Si xi ratio I( 3
P
e
2 - 3
P
o
2)/ I( 3
P
o
1 – 1
S
e
0) is density sensitive in the range 10 8 to 10 10cm –3, which is representative of electron densities found in solar active regions or small flares. 相似文献
17.
Recent R-matrix calculations of electron impact excitation rates in N-like Si VIII are used to derive theoretical emission line intensity ratios involving 2s
22p
3–2s2p
4 transitions in the 216–320 Å wavelength range. A comparison of these with an extensive dataset of solar active region, quiet-Sun, sub-flare and off-limb observations, obtained during rocket flights of the Solar EUV Research Telescope and Spectrograph (SERTS), indicates that the ratio R
1= I(216.94 Å)/I(319.84 Å) may provide a usable electron density diagnostic for coronal plasmas. The ratio involves two lines of comparable intensity, and varies by a factor of about 5 over the useful density range of 108–1011 cm?3. However R
2= I(276.85 Å)/I(319.84 Å) and R
3=I(277.05 Å)/I(319.84 Å) show very poor agreement between theory and observation, due to the severe blending of the 276.85 and 277.05 Å lines with Si VII and Mg VII transitions, respectively, making the ratios unsuitable as density diagnostics. The 314.35 Å feature of Si VIII also appears to be blended, with the other species contributing around 20% to the total line flux. 相似文献
18.
Theoretical electron density sensitive emission line ratios involving a total of eleven 2 s
22 p
2–2 s2 p
3 transitions in Sxi between 187 and 292 Å are presented. A comparison of these with solar active region observations obtained during rocket flights by the Solar EUV Rocket Telescope and Spectrograph (SERTS) reveals generally good agreement between theory and experiment. However, the 186.87 Å line is masked by fairly strong Fexii emission at the same wavelength, while 239.83 Å is blended with an unknown feature, and 285.58 Å is blended with possibly Niv 285.56 Å. In addition, the 191.23 Å line appears to be more seriously blended with an Fexiii feature than previously believed. The presence of several new Sxi lines is confirmed in the SERTS spectra, at wavelengths of 188.66, 247.14 and 291.59 Å, in excellent agreement with laboratory measurements. In particular, the detection of the 2 s
22 p
2
3
P
1 –2 s2 p
3
3
P
0,1 transitions at 242.91 Å is the first time (to our knowledge) that this feature has been identified in the solar spectrum. The potential usefulness of the Sxi line ratios as electron density diagnostics for the solar transition region and corona is briefly discussed. 相似文献
19.
Spectroheliograms in the L Mg xii line and in the Mg xi resonance ( R) 1 s
21
S
0-1 s2 p
1
P
1 line, intercombination ( I) 1 s
21
S
0-1 s2 p
3
P
1,2, line, and the forbidden ( F) 1 s
21
S
0-1 s2 s
3
S
1 line, have been obtained.Two Bragg crystal spectrometers were used mounted with mechanical collimators to obtain a spatial resolution of 1 × 3. The apparatus was launched on a sounding rocket on July 2nd, 1971. A particularly thorough study was made of the brightest active region (MC 11402).Variations in the F to I Mg xi line intensity ratio from one point to another in the active region did not reveal the presence of high electron densities.The observed intensities of the Mg xi
R line, Mg xii L line and Mg x 1 s
22 s
2
S
1/2-1 s2 p
1
P 2 s × × 2
P1 1/2, 3/2
S line are not well explained by an isothermal model. Good agreement between computed and observed intensities is obtained using the non-isothermal model proposed here. 相似文献
20.
Recent calculations of electron impact excitation rates in He-like Al xii are used to derive the theoretical electron temperature and density sensitive emission line ratios G ( = ( f + i)/ r and R ( = f/ i, where f, i, and r are the forbidden 1 s
2
1
S – 1 s2 s
3
S, intercombination 1 s
2
1
S – 1 s2 p
3
P and resonance 1 s
2
1
S – 1 s2 p
1
P transitions, respectively. These ratios are found to be significantly different from earlier calculations, and are in much better agreement with X-ray spectral data for two solar flares obtained with the SMM and P78-1 satellites. 相似文献
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