共查询到20条相似文献，搜索用时 31 毫秒
1.
Profiles of C iii
1909 and Si iii
1892 obtained on and near the limb during the 1976 flight of the University of Hawaii echelle rocket spectrograph were reduced and analyzed to determine electron densities and mass motions. The electron pressure derived (N
eTe 4 × 1015 cm–3) agrees well with that determined by Cook and Nicolas (1979) from ATM data. Nonthermal velocities in the region of formation of Si iii
1892 on the disk were found to be 10–12 km s–1, somewhat lower than the values obtained by Doschek et al. (1976), also from ATM spectra. However, velocities derived at and above the limb were in closer agreement, about 17 km s–1.Geosciences Systems Department, Computer Sciences Corporation, 8728 Colesville Road, Silver Spring, Md. 20910, U.S.A. 相似文献
2.
David H. Bruning 《Solar physics》1981,71(2):233-236
The center to limb variation of solar spectral line positions, or limb effect, has been measured for the two neutral iron lines at 5250.2 Å and 5576.1 Å. Both limb effect curves show a disk-center reversal of 40–60 ms–1 and the 5576 data also exhibit a possible second reversal at the limb. The limb effect curves are best described by polynomial expressions rather than by traditional power law expressions.Visiting Student, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
3.
Imad A. Ahmad 《Solar physics》1977,53(2):409-415
The intensity of the He+ 304 coronal line relative to the H0 1216 line, including the dominant contribution due to resonance scattering, is presented. All physical processes important in the corona are included. It is found that He+ 304 is a major contributor to the XUV corona, and that the sensitivity of the He+ 304/H0 1216 intensity ratio to coronal temperature is very weak, supporting the belief that this ratio is a good indicator of the coronal helium abundance. 相似文献
4.
Center-to-limb measurements of the Ca i 6573 intercombination line and the Ca ii 7324 forbidden line are compared with synthetic profiles based on a simple representation of the non-LTE Ca-Ca+ ionization equilibrium. The effects of photoionizations from low lying excited states of neutral calcium are found to reduce the sensitivity of the 6573 center-to-limb behavior as a thermal structure diagnostic. The synthetic center-to-limb behavior is also sensitive to uncertainties in the nonthermal broadening. Nevertheless, the measured center-to-limb behavior of 6573 favors a cool photospheric model similar to the Vernazza, Avrett, and Loeser model M over hotter models based on the Ca ii K wings. The non-LTE calcium abundance obtained from the disk center equivalent widths of 6573 and 7324 using the best fit model is A
Ca2.1±0.2 × 10-6 (by number relative to hydrogen). Applications of these lines as diagnostics of the Ca-Ca+ ionization equilibrium in other stars are briefly discussed.Visiting Astronomer, Kitt Peak National Observatory.Operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation. 相似文献
5.
An analysis has been carried out on the 32 years of 10 cm solar flux data, published by Covington, to test for evidence of the periodicities found by others using different techniques. Two features with periods of about 25 and 31 days appear to persist throughout the data, but there is no evidence for the 12.6 days periodicity claimed by Dicke and Goldenberg from solar ellipticity measurements, nor for the 12.07 day periodicity claimed by Knight et al. from an analysis of sunspot numbers. A 750 day periodicity is evident during 1970–75; this may correspond to the feature deduced by Sakurai from the sunspot numbers (and claimed to correlate with the neutrino flux); this feature can change in amplitude at other times. The other major feature has a period of about 1100 days, but disappears completely during 1970–75. The above periods are all synodic.On leave of absence at Sterrewacht, Leiden, The Netherlands during 1979/80. 相似文献
6.
Marc S. Allen 《Solar physics》1978,60(2):265-267
The chromospheric network is barely visible in the Mg i 2852 line. Unlike in plages, where it shows well-defined self-reversed emission structure in the core, the line is an unreversed absorption feature in the network boundaries, exhibiting only a small blue asymmetry. In the network cell interiors, the line is unreversed and symmetrical. 相似文献
7.
Center-to-limb observations of the Ki 7699 line made on 30 days over a five-year period using the McMath-Pierce Solar Telescope at Kitt Peak are presented. Both a relative and absolute limb effect have been derived from the data. Our determination of the limb effect in Ki 7699 shows a linear increase to the limb amounting to about 40 m s–1.Operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation. 相似文献
8.
We show that heterocyclic aromatic compounds could explain the interstellar absorption feature at 2200 Å, requiring 10% of the available interstellar C and N to be tied up in this form. 相似文献
9.
S. P. Tarafdar 《Astrophysics and Space Science》1976,39(2):419-427
A perusal of the observed column densities of different ions towards two stars, 2 Vel and Pup, has indicated the presence of an ionization mechanism, the rate of which depends exponentially on the ionization potential. An examination of two such mechanisms, collisional ionization and ionization by UV-photon with flux depending exponentially on frequency has shown that the collisional ionization is possibly the dominant one in the intercloud medium towards 2 Vel and Pup. 相似文献
10.
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
11.
The Heii 1640 Å emission feature on the IUE spectra of II Peg has been compared with the observed X-ray flux. The atmospheric activity level is determined by comparing the several diagnostic line intensities with the solar case. 相似文献
12.
Based on EUV observations of eleven sunspot regions obtained with the Coronal Diagnostic Spectrometer, CDS, on SOHO we have studied the spatial distribution, temporal variation and wavelength shift of the Hei 584 line. We find a relatively high spatial correlation between the coronal line Fexvi 360 and the Hei 584 line. This points to coronal back-radiation as an important contributor to the formation of the Hei line in active regions. However, contribution to the line formation from another source is suggested by the following two findings: First, the red-shifted line profiles of both Hei 584 and the transition region lines tend to be more intense than blue-shifted profiles. Second, the Hei 584 emission changes significantly faster than the coronal line emission. 相似文献
13.
In the 1974 eclipse of Zeta Aurigae the satellite line of the Cai intercombination line at 6572 Å appeared in all the phases observed, i.e., near the mid-eclipse and egress, although its equivalent width, 100–200 mÅ, and velocity deviation, –20 im s–1, from the principal line were considerably less than those for the satellite line found just after the fourth contact of the 1971–72 eclipse. 31 Cygni also showed a similar satellite line to Zeta Aurigae's in the 1974 eclipse, not only in the 1972 eclipse but also outside the eclipse. These satellite lines should be due to the circumstellar gas expanding from the binary systems. 相似文献
14.
S. Al-Mufti A. H. Olavesen F. Hoyle N. C. Wickramasinghe 《Astrophysics and Space Science》1982,84(1):259-261
Unidentified interstellar absorption bands at =3.2 m and 3.3 m might be due to amino-acids in bacterial grains. 相似文献
15.
Emission line spectra observed at the limb of the solar disc are presented for transitions of singly ionized silicon at 1816.93, 1817.45 and 1808.01. The profiles show self-reversals in the line cores. A non-LTE analysis for a simplified model of the silicon ion is presented and calculated line profiles are compared with the observations. The study indicates that some modification of the Vernazza et al. (1973) model of the solar chromosphere in the transition region is needed to reconcile the calculated and observed profiles. 相似文献
16.
A1 IX EUV line ratio 385.03/392.42 has been found to be density sensitive. Using this, an electron density of 3.7 × 108 cm–9 is found in the quiet, Sun off-limb from Skylab observation reported by Vernazza and Reeves (1978). 相似文献
17.
Eric G. Chipman 《Solar physics》1977,55(2):277-285
Satellite observations of velocity and intensity oscillations were made of the upper chromospheric line C ii 1336. The dominant period of oscillation is 300 s, with little evidence of the power peak in the range 150–200 s which has been observed in other chromospheric lines. Peak-to-peak amplitudes are 2 km s–1 and 8% in velocity and intensity, respectively. Tentative evidence for 900-s periodicity is presented. Relative phase measurements show that maximum intensity for the 300-s oscillation leads maximum blueshift by approximately 145 s. Comparison of line and background (scattered light) intensity variation shows upward wave propagation, with time delays between the 1800 continuum and C ii 1336 variation of 27 s and 70 s for different cases. 相似文献
18.
The length scale and life time of the transition region network cells were studied using Heii 304 filtergrams. The temporal structure function was calculated from spatially aligned Heii 304 images. The estimated life time of the network cell was about 27 hr. We compared this life time with the life time of photospheric magnetic network and of the extrapolated magnetic network. The spatial structure function was calculated from the Heii 304 filtergrams. The calculated spatial structure function saturates at 25000 km. The transition region network elements are bigger in size than the photospheric magnetic network element. The magnetic network element equals the size of the Heii 304 network element when the photospheric magnetic field is extrapolated to a height of 3000 km above the photosphere where the magnetic fluxes are deployed. The derived value of the diffusion speed of the network elements was 0.098 km s–1. 相似文献
19.
Michael J. Price 《Icarus》1978,35(1):93-98
Measurements of limb brightening on the Uranus disk within the λ7300 Å CH4 band are interpreted using an elementary inhomogeneous radiative transfer model to describe the atmosphere. A two layer model which consists of a finite, optically thin, region of conservatively scattering particles overlying a semi-infinite clear H2CH4 atmosphere satisfactorily explains the observations. The maximum optical thickness of the upper layer appears to lie in the range 0.1 to 0.2. The CH4/H2 mixing ratio in the lower layer is larger than the corresponding solar value by a factor on the order of three or greater. The results are discussed briefly in terms of current models of the Uranus atmosphere. 相似文献
20.
The λ2200 Å interstellar absorption band, generally attributed to graphite grains, could equally well arise from π → π*electronic transitions in conjugated double bonds of organic molecules. These molecules, which should comprise ～ 10% of the total interstellar dust mass, may be lodged within clumps of100 Å-sized refractory grains. 相似文献