共查询到20条相似文献，搜索用时 31 毫秒
1.
John H. Parkinson R. S. Wolff H. L. Kestenbaum W. H.-M. Ku J. R. Lemen K. S. Long R. Novick R. J. Suozzo M. C. Weisskopf 《Solar physics》1978,60(1):123-136
New observations of solar flare and active region X-ray spectra obtained with the Columbia University instrument on OSO-8 are presented and discussed. The high sensitivity of the graphite crystal panel has allowed both line and continuum spectra to be observed with moderate spectral resolution. Observations with higher spectral resolution have been made with a panel of pentaerythritol crystals. Twenty-nine lines between 1.5 and 7.0 Å have been resolved and identified, including several dielectronic recombination satellite lines to Si xiv and Si xiii lines which have been observed for the first time. It has been found that thermal continuum models specified by single values of temperature and emission measure have fitted the data adequately, there being good agreement with the values of these parameters derived from line intensity ratios. 相似文献
2.
Steady state level density of 20 levels of boron-like ions, Mg viii and Si x, have been computed as a function of electron density and temperature. We have accounted for collisional and spontaneous radiative processes. Photo-excitation between the two levels of the ground term has also been considered. Using the computed level density, line intensities have been obtained as a function of electron density and temperature. In case of Mg viii, line intensity ratio I(430.47)/I(436.62) is found to be electron density sensitive. Likewise other pairs of lines namely, I(75.03)/I(74.86), I(315.02)/I(430.47), and I(315.02)/I(335.23) are also found to be density sensitive. Similar density sensitive line intensity ratios have been found for Si x. Absolute line fluxes from these ions at earth distance have been computed and are found to be comparable with values obtained, using various satellite and rocket measurements.Paper presented at the 5th Astronomical Society of India Meeting, held at Uttar Pradesh State Observatory, Naini Tal, India, 5–9 November, 1979. 相似文献
3.
J. Lang D.H. Brooks M.G. O'Mullane C.D. Pike H.P. Summers W.T. Thompson 《Solar physics》2001,201(1):37-55
New measurements of line intensity ratios in the Be-like ion Si xi are presented for observations of the quiet Sun, active regions, coronal holes and above-limb regions obtained using the Coronal Diagnostic Spectrometer on the Solar and Heliospheric Observatory. A model ion, constructed using the best available atomic data, is used to predict the line intensity ratios for a wide range of electron temperatures and densities. Comparisons of the theoretical ratios with the new intensity ratios as well as with those from previous solar observations and laboratory measurements are given. The usefulness of the ratios for electron temperature and density diagnostics, as well as for spectrometer calibration, is discussed. 相似文献
4.
The opacities of the Si iii resonance line at 1206.5 Å and component lines of the UV 4 multiplet near 1300 Å are analyzed and re-examined in published spectra, taking account of improved expressions for photon escape probabilities and making use of an intensity/linewidth analysis recently developed. Level populations and line intensities are computed to extend knowledge of the optically thin spectrum to lower densities. Diagnostic diagrams of line ratios are included. Opacities are found to be higher than in previous treatments. 相似文献
5.
In an effort to detect torsional oscillations, we have studied the periodic half-width variations for several spectral lines in solar faculae. The duration of the series being analyzed was from 40 to 150 min. We have determined the dominant frequencies and amplitudes of the half-width oscillations and considered their phase relations to the intensity and line-of-sight velocity oscillations. Five-minute profile halfwidth oscillations with a peak-to-peak amplitude of ～10 m ?A are recorded with confidence in the upperphotospheric Si I 10 827 ?A line in faculae. The chromospheric He I 10 830 A? and Hα line profiles shows ～40–60 m ?A variations in two frequency bands, 2.5–4 and 1–1.9 mHz. No center-to-limb dependence that, according to the theory, must accompany the torsional oscillations has been revealed in the behavior of the oscillation amplitudes. According to present views, these variations cannot be caused by periodic temperature and magnetic field changes. Our observations do not allow us to explain these variations by the sausage mode action either, which should manifest itself at the double frequency. 相似文献
6.
Constance G. Andre Marie E. Hallam Jerry R. Weidner John A. Philpotts Melvin H. Podwysocki Isidore Adler 《Earth, Moon, and Planets》1976,15(1-2):133-142
The Tacquet Formation in southwestern Mare Serenitatis has unusually low visible albedos for the Al/Si intensity ratios measured by the Apollo 15 X-ray fluorescence experiment. This is a contradiction of the demonstrated good correlation between Al/Si and visible albedo data. To understand why this situation exists, a correlation study has been undertaken. This study is based on Al/Si intensity ratios and includes such other remote sensing data as visible and near IR spectral reflectance, color-difference and color-ratio photography, and broad spectrum visible albedo measurements. The Tacquet unit appears to have: (1) an average Al/Si intensity which is intermediate between mare and highland values (=0.21); (2) visible albedos equivalent to the two darkest mare units in the Tranquillitatis-Serenitatis area; (3) a low titanium content; and (4) a relatively high glass-to-crystal ratio. The evidence indicates that the discrepancy between visible albedos and Al/Si intensities in the vicinity of the Tacquet Formation might be due primarily to the addition of highland-type ejecta from the crater, Menelaus, onto a low albedo mare unit. The possibility that the formation consists of dark, high Al material such as spinel, perhaps extruded from the Menelaus Rilles, cannot be excluded, although no such material has been sampled by the lunar missions. 相似文献
7.
B. N. Dwivedi 《Solar physics》1991,131(1):49-52
The off-limb spectra, recorded by the NRL Skylab spectrograph, have been used to infer electron densities from theoretical curves of Si viii and S x density-sensitive line ratios. The derived densities are found to be in agreement with those reported by Feldman et al. (1978). Computed line intensities using the Kopp and Orrall (1976) model have also been used to estimate densities in the quite Sun and coronal holes from these curves. 相似文献
8.
Assuming steady state conditions, the occupation of 9 levels of oxygen-like ions: Ne iii, Mg v, Si vii, S ix, and Ar xi have been computed as a function of electron density and temperature. The following physical processes have been considered: collisional excitations and spontaneous radiative de-excitations for permitted and intercombination transitions; collisional excitations and de-excitations, photo-excitations and spontaneous radiative transitions among the five levels of the ground term. This study indicates that line intensity ratios for oxygen-like ions can be used as a diagnostic in the determination of these two parameters of the solar plasma.Paper presented at the 4th Astronomical Society of India Meeting, held at Radio Astronomy Centre, Ootacamund, India, 7–10 March 1978. 相似文献
9.
K. R. Nicolas G. E. Brueckner R. Tousey D. A. Tripp O. R. White R. G. Athay 《Solar physics》1977,55(2):305-319
Spectral line profiles of Si ii and Si iii are presented which were observed both at solar center and near the quiet solar limb with the Naval Research Laboratory EUV spectrograph of ATM/SKYLAB. Absolute intensities and line profiles are derived from the photographic data. A brief discussion is given of their center-to-limb variations and of the optical thickness of the chromosphere in these lines. Nonthermal broadening velocities are found for the optically thin lines from their full width at half maximum intensity (FWHM).Also at High Altitude Observatory for part of this work.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
10.
Observations of a sunspot in the Civ line at 1548 Å formed in the transition region have been analyzed to obtain the time variations and/or mean values of the velocity, intensity, longitudinal magnetic field, and line width. Oscillations with periods between approximately 110 and 200 s are observed only over the umbra where the transition region magnetic field is highest and the line width is smallest. When periodic intensity variations occur at the same frequency as the velocity oscillations, the peak intensities occur slightly before the maximum upward motions. No periodic variations in the transition region magnetic field have been detected. Scatter diagrams are presented which show possible relationships between the flow velocity, emission line intensity, line width, and transition region magnetic field. 相似文献
11.
Time-sequences of line profile data have been subjected to a unique analysis which produces an amplitude and phase of the velocity and intensity at several line depths for each time sample and spatial point on the Sun. The data have been filtered to pass only the frequencies and spatial wavenumbers of the 5-min band. Yet, a secondary oscillation emerges, the phase of which propagates downward. Empirical eigenfunctions for velocity and intensity are given, and the kinetic energy flux is computed.Operated by the Association of Universities for Research in Astronomy under contract with the National Science Foundation. 相似文献
12.
S. A. Lamzin 《Astronomy Letters》2000,26(9):589-599
The ultraviolet spectra of the stars RY Tau and HD 115043 from the Hubble Space Telescope are analyzed. RY Tau belongs to the classical T Tauri stars, while HD 115043 is a young (t~3×108 years), chromospherically active star. The most intense emission lines were identified, and their fluxes were measured. Low-resolution spectra of RY Tau and HD 115043 in the wavelength range 1160–1760 Å exhibit almost the same set of emission lines. However, first, the luminosity of RY Tau in these lines is approximately a factor of 300 higher than that of HD 115043, and, second, the relative line intensities differ greatly. The intensity ratio of the C IV λ1550, Si IV λ1400, and NV λ1240 doublet components is close to 1: 2 in the spectra of both stars. Judging by the continuum energy distribution, the spectral type of RY Tau is later than that of HD 115043. Synchronous flux variability in the C IV λ1550 and He II λ1640 lines in a time of ~20 min was detected in RY Tau. The flux rise in these lines was accompanied by a redshift of the intensity peak in the profiles by~50 km s?1. Intermediate-resolution spectra are used to study line profiles in the spectrum of RY Tau. In particular, the profiles of (optically thin) Si III]λ1892 and C III]λ1909 lines were found to be asymmetric and about 300 km s?1 in width. The (optically thick) C IV λ1550 doublet lines have similar profiles. The Mg II λ2800 doublet lines are also asymmetric, but their shape is different: they consist of a broad (?750 km s?1 at the base) emission component on which an interstellar absorption line shifted from the line symmetry center by about 20 km s?1 is superimposed. The intensity ratio of the Mg II λ2800 doublet components is?1.4. Whether there are molecular hydrogen lines in the spectrum of RY Tau is still an open question. It is shown that the emission lines in the ultraviolet spectrum of RY Tau cannot originate in a hydrostatically equilibrium chromosphere. It is argued that quasi-steady accretion of circumstellar matter is responsible for the emission. 相似文献
13.
Near infrared coronal line emission at 1.98 ± 0.02Μm due to [Si VI] detected in the spectrum of Nova Herculis 1991 about 17
days after optical maximum is reported. The early appearance of coronal emission is yet another unusual feature of this fast
nova in which early onset of dust formation processes and X-ray detection five days after outburst have already been reported.
The coronal line observations reported here are consistent with X-ray detection and support a hot shocked circumstellar envelope
at the periphery of the dust formation zone in the nova. 相似文献
14.
Semanur Engin 《Astrophysics and Space Science》1974,29(2):343-378
The spectrum of the metallic-line and magnetic star HD 153286 has been studied. The line intensity is constant within the
limit of the errors, while the radial velocity is slightly variable. A differential analysis by means of the curve-of-growth
method has been made, using 5 And, F5 V as standard star. Moreover, an atmospheric model has been computed; the results of
the fine analysis indicate a defect of Sc by a factor of 30 and a defect of Ca by a factor included between 4 and 25; Si,
Ti, V, Cr and Fe are normal, Mn, Co, Ni in slight excess by factors included between 2 and 5. Sr, Y, Zr, Ba and La are in
excess by factors lower than 10; Ce, Nd and Sm are almost normal; Eu and Gd are in excess by factors of 250 and 4, respectively.
These results are compared with the predictions of the diffusion theory. 相似文献
15.
Additional observations of He ii (304 Å) and Si xi (303 Å) were obtained from a high resolution rocket spectrograph flown on 30 August, 1973 and 20 January, 1975. The profile of the He ii (304 Å) line is everywhere clearly non-gaussian across the solar disk, except in bright active areas. Near the limb, the profile is distinctly reversed. The profile of the Si xi (303 Å) line is essentially gaussian for all regions across the solar disk. Measurements of the He ii/Si xi intensity ratio indicate that the average value of this ratio across the disk depends markedly on solar activity, being about 101 for a moderate level of activity and 301 for a quiet Sun. 相似文献
16.
J. Jakimiec V. V. Korneev V. V. Krutov I. A. Zhitnik S. Pŀocieniak B. Sylwester J. Sylwester 《Solar physics》1975,44(2):391-401
High resolution profiles of the Mg xii 8.42 Å line in the solar X-ray spectrum were recorded from the Intercosmos 7 satellite. The Mg xii line intensity provides a sensitive indicator of the hot plasma content (T ? 3 × 106 K) in coronal condensations and X-ray flare volumes. The ratio of the line intensity to the intensity of the adjacent continuum has been used to compute approximate thermal models of the emitting regions. For all the investigated coronal condensations the temperature distribution of plasma has been found to be a function monotonically decreasing with temperature. But for some X-ray bursts there occurred a distinct excess of the hot plasma of temperature between 6–10 × 106K. FWHM values of the Mg xii line profiles have been used to estimate ion temperature in the emitting regions. 相似文献
17.
For accurate electron density diagnostics in the solar transition region, the principle of electron density diagnostics are discussed by lines from Si VIII ion for kappa and Maxwellian distributions By observed line ratio of the Si VIII 1440.50 to 1445.75 Å lines in quiet sun and active region, the electron density is discussed for any observed line ratio, and results are consistent with reported values in literature. The relationships between line ratio and electron density for the kappa and Maxwellian distributions are also discussed, in the case of lower and higher electron density limits, and results indicate that different distributions have no effect on relationships between the line ratio and the electron density at lower or higher electron density limit. This discussion is significant for accurate electron density diagnostics in the solar transition region, which will be important for study on coronal heating and acceleration of solar wind. 相似文献
18.
The seasonal variation of the nocturnal average intensity, and the typical variation of the sodium airglow intensity during the night have been deduced, using a data set that has been accumulated over a period of 5 years. The maximum intensity, which occurs at the equinoxes, is about 2–3 times as large as the intensity during winter, when the intensity of the D2 line is about 30 R. The nocturnal variation is symmetrical about midnight, where the intensity is some 30% less than just after (before) dusk (dawn) values. 相似文献
19.
Tokio Tsubaki 《Solar physics》1977,51(1):121-130
By making line profile analyses of the Fe xiv 5303 coronal line, temporal variations of three fundamental quantities, the line intensity, the FWHM, and the Doppler velocity, have been investigated for an active region. The power spectrum shows that the line-of-sight Doppler velocity fluctuated periodically at two locations with a period of nearly 300 seconds, while no periodic oscillations were found in line intensity. As to the FWHM, some evidence of periodic fluctuations are recognized but in a less distinct manner.The Sacramento Peak Observatory is operated by the Associated Universities for Research in Astronomy Inc. by contact with the National Science Foundation. 相似文献
20.
Based on archival Hubble Space Telescope ACS/WFC images, we have performed stellar photometry for the young tidal dwarf galaxy Ho IX. We have determined that star formation in Ho IX began 110 Myr ago and ended 20 Myr ago. We have identified 20 young star clusters in the galaxy with ages from 25 to 100 Myr. For the main star-forming region of Ho IX along one direction, we have determined the change in the number density of stars with three ages: 30, 50, and 90 Myr. A relation has been found between the ages of stars and the spatial sizes of the subsystem formed by them. This relation can be explained by expansion of the stellar subsystems. Under this assumption, the expansion velocity is 9.8 km s?1 as the age changes from 50 to 90 Myr. Edge-on low-mass late-type galaxies have similar relations between the ages and sizes of their stellar subsystems. 相似文献