共查询到20条相似文献，搜索用时 46 毫秒
1.
H. Zirin 《Solar physics》1970,11(3):497-512
Climax coronagraph observations of the accessible Fe lines, as well as the Caxv 5694 line at the time of the 1962 total eclipse, are analyzed. The spectra show that the ionization equilibrium of iron is not substantially changed in an intense coronal condensation, at least for the stages x through xv. The only exception is Fexv 7059, for which density effects are important. The stability of the ionization distribution is explained by the dynamic nature of the Fe ionization, with ions entering on the high side (Fexvi and up) due to rapid heating and then cooling through the visible stages.Comparison of the ionization distributions inferred from radiative and collisional excitation of the iron lines shows that the excitation must be by collisions everywhere at the heights examined (less than 50 000 km).The iron abundance in the corona is found to be 10–4 that of hydrogen, but this figure would be reduced by the amount of cyclic excitation.The peak electron density in the condensation is 8 × 109, and the peak value of the 5694 line/ continuum ratio is 2.5, in good agreement with calculations by Chevalier and Lambert.The ratio of the infrared Fexiii lines is measured along the limb and found to vary with electron density as expected, the 10 747/10 798 ratio is 7 or less at densities much below 109 and saturates at a value of 2 for densities above that amount. 相似文献
2.
Fluxes have been computed for Fex (6374 Å) and Fe xiv (5303 Å) lines as a function of solar radii and at various coronal tempratures. The electron density derived from the white light corona during the total solar eclipse of 1980 were used in the computations. Fluxes in adjacent continua have also been computed. The computed ratios of line flux to the square of continuum flux at a coronal temperature of 1.6 × 106 K show a good fit with the observed values for Fex line. Further, radiative excitation seems to dominate over collisional excitation beyond 1.3 solar radius. 相似文献
3.
Airborne eclipse observations of the [Six] 1430.5 nm coronal emission line are reviewed, and new ground-based out-of-eclipse coronagraph observations obtained at NSO/Sacramento
Peak are reported. We find that the [Six] 1430.5 nm coronal emission line brightness is less than 8 × 10−6
B⊙ in small active region corona which showed [Fexiii] 1074.7 nm emission (corrected for sky background) of about 20 × 10−6
B⊙.
Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National
Science Foundation. 相似文献
4.
The excitation of the lowest (3s23p2) configuration of Fexiii is discussed for the range of density and temperatures experienced in the solar corona. The principal features are the introduction of proton collisions as an important mechanism for exciting the 3p2
3P levels, the use of improved electron collision strengths and a detailed discussion of the influence of the excited configurations. The predicted intensity ratios are shown to be consistent with available observations with the single exception of an eclipse measurement of the ratio of the intensities of the infrared lines. 相似文献
5.
During the total solar eclipse of 11 June, 1983, an imaging dual-channel Fabry-Pérot interferometer was used to obtain line profiles simultaneously in the green 5303 Å [Fe xiv] and the red 6374 Å [Fe x] coronal lines at various positions in the corona. Extensive microdensitometry followed by multi-Gaussian curve-fitting analysis has resulted in the determination of coronal temperatures and velocity separations between different pockets of coronal gas in the line of sight over a large extent of the corona. Fewer high temperature zones are to be found in the corona of 1983 compared with our similar green-line measurements of the solar maximum corona of 1980. The data are consistent with a temperature maximum occurring at 1.2 R
, as found at the 1980 eclipse, but our new data are insufficient to observe farther out than this radius and so determine the position of a maximum. The velocity field in the corona at the 1983 eclipse is less structured compared with that at the 1980 eclipse and is mainly confined to the zone 20–30km s–1. 相似文献
6.
Line profiles of He ii 4686 Å and He i 4713 Å from active regions in the chromosphere were observed during the total solar eclipse of February 16, 1980, with a grazing incidence objective grating spectrograph. The Doppler width of the He i triplet line of 4713 Å increases with height and the average width is compatible with width of metallic and hydrogen lines, suggesting that the kinetic temperature of He i triplet emitting region is T 8000 K. This can only be explained by recombination after photo-ionization due to coronal UV radiation. The Doppler width of the Paschen line of He ii 4686 is, without any correction for the separation of subcomponents of the line nor non-thermal velocity, 18.4 km s-1. This line width also shows a tendency to increase with height. After comparison with Doppler widths of He i 4713 and the EUV lines, and a necessary subtraction of non-thermal velocity, it is shown that this line is emitted in a 2 × 104 K temperature region, which again supports the view that this line is emitted through the recombination process after photoionization due to coronal XUV radiation below 228 Å. 相似文献
7.
Carole Jordan 《Solar physics》1971,21(2):381-391
Identifications are proposed for twenty of the twenty-eight coronal lines observed in the spectra obtained during a rocket flight into the path of the 7 March, 1970 solar eclipse. The methods by which the lines have been identified are discussed. Most of the lines identified are from forbidden transitions between levels in the ground 2p
n and 3p
n configurations in high ions of magnesium, silicon, sulphur, iron, and nickel. The temperature range represented is from 6.9 × 105 K to 2.5 × 106 K. The classification of three lines of Fexii and two of Nixiv has led to a revised identification for the near ultraviolet 2
D
3/2-2
P
1/2 transition in Fe xii. This transition can be identified with the line at 3072 Å rather than that at 3021 Å as previously suggested in the literature. 相似文献
8.
J. O. Stenflo 《Solar physics》1971,21(2):263-271
The magnetic field in the outer corona and in interplanetary space has been calculated from the photospheric magnetic fields measured around the time of the 7 March, 1970 eclipse. The field-line maps are compared with eclipse photographs showing coronal structures out to about 12 r
. The projected field lines as well as the observed streamers appear straight. This is caused by the rapid expansion of the outer corona and is not an indication of corotation. The calculations show that the angular velocity of the coronal plasma decreases rapidly with distance.The relation between magnetic fields and density enhancements is discussed. The field strength in the photosphere seems to determine the amount of mechanical heating of the lower corona. The density structure higher up in the corona will, however, depend decisively on the topology of the field, particularly on whether we are on open or closed field lines, and not simply on field strength.The calculations show a sector structure of the interplanetary field, which agrees well with spacecraft observations. Also the magnitudes of the observed and calculated interplanetary field agree after the Mt. Wilson magnetograph data have been corrected to account for the temperature and saturation effects in the spectral line Fei 5250 Å.On leave from the Astronomical Observatory, Lund, Sweden.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
9.
We present theoretical calculations of the observed coronal emission line profiles of Fexiv (5303 Å) and Fex (6374 Å) ions, which are observed at the time of total solar eclipse. Baumbach's relation (Allen, 1973) of electron density has been employed to compute the full width at half maximum FWHM. We have employed several other electron density distributions and found that the calculated differences in the FWHM are within 0.5% of one another. We have used the ion densities N
i/NE given by Jordan (1969). To explain the observed FWHM, we have assumed that the corona is expanding spherically symmetrically with a velocity of one or two mean thermal units and no turbulence is included. With these highly simplified assumptions, we have reproduced qualitatively the profiles and FWHM's of the above lines. However, to explain quantities of FWHM's, we should take into account the inhomogeneities in the structure of the corona. It is thus shown, that turbulence is not necessary to explain the observed FWHM. 相似文献
10.
R. Grant Athay 《Solar physics》1973,29(2):357-364
Mean density models of the solar corona show evidence for two distinctive density regimes characterized by different density gradients. High density gradients are identified with regions of predominantly open magnetic lines of force and low density gradients are identified with regions of predominantly closed magnetic lines of force. Spectroscopic data yielding equivalent widths of forbidden lines of Fe x and Fe xiv strongly suggest that the coronal temperature for r > 2.5 R
decreases considerably less rapidly in equatorial regions than r
–2/7, which is the decrease predicted by conduction models with open field lines.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
11.
The white-light corona from 3–9 R
s and the XUV (170–500 Å) corona, photographed from a rocket at 1930 UT on 7 March, 1970, are compared with the X-ray corona photographed from a rocket flown at 1900 UT by AS & E, the H Ly- corona obtained during totality by Speer et al., the Fexiv 5303 Å corona from Hawaii, and total eclipse photographs in white-light and infrared. 相似文献
12.
George L. Withbroe 《Solar physics》1969,9(1):19-30
The center-to-limb variation of equivalent widths of 198 Fei lines in the spectral region 5500 to 7000 Å was studied with five photospheric models. The gf-values of Corliss and Warner (1964) were used in the analysis. The photospheric iron abundance was found to vary with excitation potential. This can be explained by a systematic error in the gf-values of high excitation lines and an error of 250 to 500K in the temperature of the arcs used for measuring the gf-values. Departures from LTE in the solar Fei lines are also a possibility. The adopted photospheric abundance of iron, log(N
Fe/N
H) is - 5.2. 相似文献
13.
We identify the Balmer 9 and 11 lines of He ii at 959 Å and 942 Å in solar spectra. These lines are produced mainly by recombination following photoionization of He ii by coronal XUV radiation. From analysis of the line intensities, we confirm the theoretical model of Avrett et al. (1976), who found that an appreciable amount of He++ is present at temperatures of 1–2 × 104 K and that the anomalously strong He ii 304 line is produced primarily by collisional excitation. We also confirm the suggestion of Kohl (1977) that the photoionization-recombination process is more important in active regions than in the quiet Sun, and we find that the 304 line is produced largely by recombination in solar flares. 相似文献
14.
In order to study the electron density at the scale of the most encountered structures in coronal active regions a new multichannel coronagraph associated with a photoelectric spectrograph is now used at the Pic-du-Midi Observatory. In its quasi-routine mode this instrument, which is described in this paper, works with a 30 field aperture in a parallel manner with aK-polarimeter. On each observed region it obtains maps of intensities of the
3388, 10747, and 10798 Å emission lines due to Fexiii ion. Each measurement point is associated with a quasi-simultaneous image of the emission corona structures viewed in the light of the5303 Å line of Fexiv. Three examples of observations are given and the capabilities are discussed.Measuring electron density in coronal active regions. II A multichannel photoelectric coronagraph with a photo-electric spectrograph and a reflex monitor at5303 Å.LA du CNRS No. 040285. 相似文献
15.
16.
Simultaneous observations obtained with the HAO/SPO coronal emission-line polarimeter and the new SPO emission-line coronagraph are compared. The polarimeter data are measured in the Fexiii (10747 Å) line and the coronagraph observations are recorded in the Fexiv (5303 Å) line. The polarimeter field-of-view is relatively coarse compared with the resolution limit of the coronagraph. Therefore, the observed coronal polarization cannot be related directly to the detailed loop structures that characterize the localized coronal distribution, but it is found that large-scale emission features have corresponding polarization signatures. Since the measured linear polarization vectors describe the projected magnetic field direction, as shown theoretically, it follows that the form of the large-scale coronal distribution describes corresponding magnetic field structures. Measured polarization values are consistent with those predicted theoretically. Interpretation of these data to obtain corresponding magnetic field directions suggests that the value usually accepted for iron abundance in the corona might be too large.The National Center for Atmospheric Research is sponsored by the National Science Foundation.Operated by the Association of Universities for Research in Astronomy, Inc. under contract AST 78-17292 with the National Science Foundation. 相似文献
17.
Cemal Aydin 《Astrophysics and Space Science》1979,64(2):481-507
Twenty-five coudé spectrograms (22 with dispersion 12 Å mm–1 and three 7 Å mm–1) of 6 Cassiopeiae (A3 Ia) have been studied. The observations were made at the Haute Provence Observatory. The results of the analysis suggest a correlation between the variations of the equivalent widths, the microturbulence and the radial velocity. The radial velocity and turbulent velocity present a rapid variation with time, even in intervals as short as about an hour. The hydrogen lines are slightly asymmetric but the strongest Feii lines are clearly asymmetric. We found that the amount of asymmetry of the strongest Feii lines (I>6) correlates with the loggf value, with the estimated laboratory intensityI, and with the equivalent widthW
.The observations have been made at the Astronomical Observatory of Haute Provence (CNRS). This work has been supported by TUBITAK (Scientific and Technical Research Council of Turkey), and partially by CNR (Consiglio Nazionale delle Ricerche) of Italy. 相似文献
18.
M. Waldmeier 《Solar physics》1975,43(2):351-358
Coronal interferograms in the lines of Fe xiv 5303 Å, He i 5876 Å and Fe x 6374 Å were obtained during the total solar eclipse of 10 July, 1972 (see Figure 2). He i emission was found in the chromosphere only. The upper limit of the D3 equivalent width in terms of the coronal continuous background is 0.013 Å in the inner corona (r=1.15 R⊙). The λ6374 negative was taken with low contrast. The half width of 16374 is 1.0–1.08 Å for a limited area of the corona (P=88?104°, r=1.30?1.44 R⊙). A detailed photometry of the 5303 Å line was carried out and the behaviour of the half widths and equivalent widths were studied in different regions of the corona. The half width of λ5303 increases with distance from the Sun's center in almost all the studied regions (1.2 R⊙ ? r ? 1.7 R⊙). This increase corresponds to an increase of the non-thermal velocities with a gradient of 1–2 km s-1 per 0.1 R⊙. The equivalent widths, expressed in the coronal continuous background intensity remain constant on the average. 相似文献
19.
L. W. Acton R. C. Catura A. J. Meyerott C. J. Wolfson J. L. Culhane 《Solar physics》1972,26(1):183-201
We report some results of a rocket experiment flown on 29 April, 1971. A survey of the solar corona was carried out with a pair of collimated Bragg spectrometers to study the resonance, intersystem and forbidden line emission from the helium-like ions O vii (22 Å) and Ne ix (13 Å). In the direction of dispersion the collimator provided a field of view of 1.7. Also, the continuum radiation near 3 Å was monitored by a collimated proportional counter within a view angle of 4.2. The observed X-ray emission came from the general corona, seven plage regions, and one dynamic feature- the late stage of a small flare. From the intensity of the O vii and Ne ix resonance lines the electron temperature and emission measure of the individual emitting regions are derived on the basis of two models, one (a) in which the region is assumed to be isothermal and another (b) in which the emission measure decreases exponentially with increasing temperature. The latter model, which is the most adequate of the two, yields for the electron temperature of the time-varying feature 2–3 × 106 K, for the other active regions 1.5–2.5 × 106 K, and for the general corona 1.3–1.7 × 106 K. The Ne ix emitting regions are about 1.5 times as hot as the O vii regions. The emission measure ranges from 0.4–2.3 × 1048 cm–3 for all active regions and is about 2 × 1049 cm–3 for one hemisphere of the general corona above 106 K. From an analysis of the ratio, R, of the forbidden and intersystem lines of O vii we conclude that none of the regions producing these lines at the time of the rocket flight had electron densities exceeding about 3 × 109 cm–3. Our data demonstrate a dependence of R upon temperature in agreement with the theory of Blumenthal et al. (1971). The wavelengths for the intersystem, the 1s
22s
2
S
e–1s2p2s
2
P
0 satellite, and the forbidden transition show in the case of Ne ix improved agreement with predictions. The observed strength of the satellite lines for both O vii and Ne ix agrees with the predictions of Gabriel's (1972) theory, which attributes their formation to dielectronic recombination.We are saddened to report the death of A. J. Meyerott on 13 November, 1971. 相似文献
20.
High resolution spectroheliograms in the ultraviolet emission lines He i, He ii, O iv, O v, and Ne vii have been photographed during a sounding rocket flight. Simultaneously, broad band filtergrams of the far ultraviolet solar corona were obtained from the same flight. This paper describes qualitatively the spatial distribution of the UV emission. A comparison with an H filtergram is made. The most significant results can be summarized as follows: We find most of the ultraviolet emission concentrated around spicules, with different degree of concentration, decreasing with higher temperatures. 4 different areas of ultraviolet emission can be distinguished. (1) The normal network, bright in all UV emission lines from the chromosphere into the corona. (2) The coronal holes, bright in all UV emission lines up to 600 000 K but depressed in coronal lines from 1 million degrees upward. (3) The coronal depressions near active centers, absence of all ultraviolet emissions and (4) Active regions, where ultraviolet emission comes from plages, sunspots and coronal loops. High non-thermal Doppler velocities can be found in certain plage kernels around 105 to 2 × 105 K. Sunspots are bright in the ultraviolet, but do not exhibit He i or He ii emission. The corona above sunspots is weak. Sunspots do not show high non-thermal Doppler velocities. The He i and He ii emission does not follow either chromospheric, transition zone or coronal pattern; one can recognize some typical behavior of each. 相似文献