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1.
The weakening of EUV line emission due to continuum absorptions of neutral hydrogen and neutral helium is investigated to examine its wavelength-dependence. After convolving the intensities predicted from multilevel calculations over an instrumental profile, we found a systematic, linear weakening for lines shortward of 912 Å, which can be attributed to Lyman continuum absorption in the cool chromospheric cloud. The degree of the weakening at the quiet Sun seems to be constant in the temperature range of 4.3 < log T < 5.4. We also find that the lines shortward of 504 Å are somewhat weakened by He i continuum absorption. From the comparison of both weakenings the temperature of the absorber is estimated to be rather low (T e 7 × 103 K).  相似文献   

2.
IUE ultraviolet spectral recording for a low excitating planetary nebula NGC 6369 is obtained. The very strong doublet 2800 Mgii in emission as well as not less strong absorption line 2852 Mgi are discovered in the spectrum of this nebula. It is shown that the resonance line 2852 Mgi may originate only in a neutral envelope, around the nebula, consisting of neutral hydrogen, neutral magnesium, and dust particles (Hi+Mgi). The importance of this absorption line as a powerful indicator of the discovery of neutral envelopes around the planetary nebulae is outlined.The possibility of the existence of one more envelope—transition zone—immediately contacting with the bright that is ionized part of nebula (Hii+Mgii) is also shown. The transition zone consists of neutral hydrogen, ionized magnesium, and dust particles (Hi+Mgii), main parameters of this zone are also obtained (Table IV).The temperature of the central star of this nebula is obtained for the first time:T *=48000 K. Continuous background in the interval 2600–3000 Å is identified with Balmer continuum with electron temperatureT e =12500 K.  相似文献   

3.
Morozhenko  N. N. 《Solar physics》1974,34(2):313-322
Observations of the lines He i 3888 and H8 in 80 quiescent prominences by the author, and in other prominences by Kubota et al. (1972) and Morozhenko (1971), have been used to derive the dependences of I(3888)/I(H8) on I(H8), N 2 3 s on 0 (H), and N + n e on 0(H) (Figures 1, 2, 3 and 4). The equations of ionization equilibrium and triplet system steady state for a helium atom (27 levels and continuum were considered) were solved together with the radiation transfer equation in the helium Lyman continuum. As given n e () distribution with depth and T e =7500 K were assumed. The 23 S level population N2 3 s, helium emission measure N + n e and the intensity ratios of the He i 3888 and H8 lines were calculated and compared with observation (Figures 2, 3 and 4, solid lines). The figures show that in bright prominences the observed values of N 2 3 s and N + n e are systematically higher than the calculated ones. These deviations cannot be eliminated by decreasing n e . One can make the calculations and observations agree for bright prominences by increasing the UV radiation which penetrates into the prominence.  相似文献   

4.
Spectrographic observations of the flash spectrum were made by the Kwasan Observatory at the total solar eclipse on 7 March, 1970. The integrated intensities of Fexiv 5303, Fex 6374, and the continuum were measured on the spectrograms as a function of height above the Sun's limb. It was found that a large amount of emission in the coronal lines originates in the interspicular regions of the chromosphere. Analysis of the data yielded that the interspicular regions consist of coronal material of T e = 1.6 × 106–1.2 × 106 and log N e = 8.5–9.5, and that a decrease in T e and an increase in N e occur with decreasing height.  相似文献   

5.
The abundance of helium relative to hydrogen is spectroscopically determined in prominences and in the chromosphere by using 1952, 1958, 1962 and 1966 eclipse data. Care is taken in the intensity calibration of emission lines, the self-absorption, and the departure from local thermodynamic equilibrium. We find from the line profiles and intensities of prominences and the chromosphere that the neutral helium lines are emitted in the metal-hydrogen emitting region where the kinetic temperature is low enough, 6000 8000 K, so that only the ionization due to UV radiation from the corona can explain the intensity of neutral helium emission. Also we find that the intensity ratio of Hei 3888.65 to H8 3889.05 increases towards the upper boundaries of prominences and of the chromosphere and that it approaches to a universal limiting value, both in various prominences or in the chromosphere, where it is considered that the ionization of neutral helium and hydrogen is nearly complete. From these facts the helium to hydrogen number ratio is found to be 6.5 ± 1.5%.A new schematic model of the chromosphere is presented where spicules have no hot region of emitting neutral helium lines. Here it is suggested that the kinetic temperature of spicules, 6000 8000 K, would be primarily determined by the radiation temperature of the corona and the transition region beyond the Lyman continuum of hydrogen which happens to be around those temperatures.  相似文献   

6.
A direct method for determining electron densities from emission line intensities of ions in the beryllium isoelectronic sequence is described and then applied to the analysis of extreme ultraviolet Ciii and Ov spectra from both quiet and active areas in the solar transition region. The results are consistent with a value of N e T e = 6 × 1014 cm-3K for the quiet Sun at temperatures of 5 × 104 to 3 × 105K. Electron densities are approximately five times greater in active regions than in the quiet Sun.  相似文献   

7.
Chultem  Ts.  Yakovkin  N. A. 《Solar physics》1974,34(1):133-150
The statistical equilibrium equations for the continuum and first 10 levels of a hydrogen atom show that the radiation of a bright prominence (the brightness of the H line has attained 56 mÅ of the disc centre spectrum) is completely due to scattering of the Sun radiation. The basic unknowns are separated with certainty: electron concentration (n e = 3.0 × 1010 cm–3), effective thickness (l = 4.2 × 108 cm) and electron temperature (T e = 5000 K).Radiation of a very bright prominence (A (H) = 213 mÅ; T e = 7300 K; n e = 5.0 × 1011 cm–3; l = 1.3 × 107 cm) is on account of electron impacts (40%) and the Sun radiation scattering (60%).The parameters are shown to depend greatly on the prominence optical thickness in the lines of the first subordinate series of a hydrogen atom. In the course of determination all the parameters and 100 interconnected integral equations of the radiation diffusion have been thickness-averaged; the population of levels has been calculated by observations using the self-absorption factors.  相似文献   

8.
Continued spectroscopic observations of Nova Del 67 during 1971 and 1972 show a general decrease of the nebular and coronal emission with respect to the local continuum. The continuous spectrum exhibits a strong Balmer emission (figure 1). Equivalent widths of Hi, Hei, Heii, Oi, [Oi], Oii, [Oii], Oiii, [Oiii], Niii, [Sii], [Aiii], [Neiii], [Nev], [Fevi], [Fevii], [Fex], [Fexi], [Fexiv], [Nixvi], [Nixv] are listed in tables 1 and 2.Figures 5 to 10 show several line profiles, which can be interpreted in terms of a model proposed by Hutchings (1972). Kinematical properties of the nova envelope do not seem to have changed in the 1968–1972 time interval. However, a study of the [Oiii] (4959 Å) line indicates that the physical conditions in the polar blobs in 1972 (T e=10 660 K,N e=5,5×105 cm–3) are different from those prevailing in equatorial rings (T e=9×100 K,N e=7×105 cm–3).

Le matérial d'observation utilisé pour cette étude a été obtenu à l'aide de téléscopes de 120 cm, 152 cm et 193 cm de l'Observatoire de Haute-Provence (CNRS).  相似文献   

9.
From a high-resolution spectrum of a sunspot umbra (1.1 < < 2.3 m) we derive models of the temperature stratification in the deep layers of the umbra. The observed spectrum is corrected for straylight using the Hi Paschen line at gl = 1.282 m. A method is described for the iterative fitting of empirical temperature models to spectral information, and the method is applied to the present data. We find that the observed profiles of 3 high-excitation lines of Sii and the observed continuum contrast between umbra and photosphere cannot be reproduced with a single one-component model of the umbral atmosphere: the Si i lines require a model that is 460 K hotter at gt 0.5 = 3 than the continuum model. This indicates that hot and cool components coexist within the umbra. A temperature model derived from the relative intensity in the wings of 3 low-excitation lines of Mgi, Ali, and Sii is not significantly different from the continuum model.Based on observations obtained at Kitt Peak National Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), under contract with the National Science Foundation.  相似文献   

10.
D. F. Smith  S. H. Brecht 《Solar physics》1994,153(1-2):337-345
A critical examination of the components of the recent impulsive loop flare model of Takakura is made. It is found that his analysis of the stability of the electron distribution resulting from anomalous heat conduction is in error and electron plasma waves would not be excited. Rather, in the regions where the electron/proton temperature ratioT e/T i 10, electrostatic ion-cyclotron waves would be excited and in the regions whereT e 10, ion-acoustic waves would be excited. Ratios ofT e/T i 10 occur only in the late time development behind the conduction fronts. Since the anomalous resistivity due to electrostatic ion-cyclotron waves is fortuitously about 70% of the one used by Takakura, the general development will follow closely the one calculated by him. Because the anomalous resistivity due to ion-acoustic waves is about 95 times the one used by Takakura, the development in the parts of the loop whereT e/T i 10 for late times would be altered considerably.Also Guest Worker at NOAA Space Environment Laboratory, Boulder, Colorado, U.S.A.  相似文献   

11.
We describe a new model of the chromosphere based on Lyman-continuum observations by Harvard spectrometers aboard the satellites OSO 4 and OSO 6. The model assumes (a) that a random distribution of optically thick inhomogeneities overlies a plane-parallel homogeneous atmosphere, and (b) that the Lyman continuum in the chromosphere is optically thick and the only significant opacity source between 600 and 912 Å.The temperature, gas pressure, electron pressure, particle densities, and b 1 (the hydrogen ground-state departure coefficient) are calculated as a function of height in the chromosphere.The model reproduces the observed quiet-region intensities in the Lyman continuum. The inhomogeneous structures, which we believe to be spicules, are inferred to be optically thick in the Lyman continuum and to have a source function below that of the mean chromosphere. If they are also optically thick in the free-free (millimeter) continuum and cooler than about 5000K, they could produce the observed limb darkening at 1 and 3 mm. Such low temperatures are at odds with current spicule models, but could exist in the cores of spicules.The Lyman-continuum emission shortward of 750 Å shows an excess emission over that predicted by the above model. This is found to be consistent with the existence of a temperature plateau with T 22000K in the very high chromosphere.  相似文献   

12.
In this paper we discuss the ionization equilibrium of hydrogen and helium in a nebula with an arbitrary gas density distribution. If we consider the spectral characteristics of hot stars, a power law is found to provide a good approximation to the Lyman continuum spectrum for stars withT eff≤100 000 K. With this simplification the ionization equilibrium equation is analytically solved first for a pure hydrogen nebula, then for the general case of a nebula containing H, He, and heavy elements. A simple and quite general formula for the determination of the size and the emission of the He+ zone is obtained. Finally, the ionization equilibrium He++?He+ is considered. This problem can be decoupled from that of the ionization of H0 and He0 if the stellar spectrum is steeper thanv ?0.9 or, equivalently, if the star effective temperature is lower than 200 000 K. Within this limit, which surely includes all classicalHii regions and the low-medium excitation planetary nebulae, an analytical solution of the problem can be used.  相似文献   

13.
Using near-simultaneous full disk solar X-ray images and Hei 10830 spectroheliograms from three rocket flights, we compare dark points identified on the Hei maps with X-ray bright points identified on the X-ray images. We find that for the largest and most obvious features there is a strong correlation: most Hei dark points correspond to X-ray bright points. However, about two-thirds of the X-ray bright points were not identified on the basis of the helium data alone. Once an X-ray feature is identified it is almost always possible to find an underlying dark patch of enhanced Hei absorption which, however, would not a priori have been selected as a dark point. Therefore, the Hei dark points, using current selection criteria, cannot be used as a one-to-one proxy for the X-ray data. Hei dark points do, however, identify the locations of the stronger X-ray bright points.Visitor, National Solar Observatory. National Optical Astronomy Observatories operated by the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.  相似文献   

14.
Radio measurements of the electron temperature ofHii regions are obtained from the ratio of the brightness temperature of a hydrogen recombination line to that of the adjacent continuum, while optical measurements are obtained from the ratio of [Oiii] forbidden-line intensities. The radio and optical measurements made under the assumption of an isothermalHii region,T R andT opt respectively, are combined to derive a temperature distribution for an entire nebula. A sphericalHii region in local thermodynamic equilibrium with constant density which is optically thin in both the line and the continuum is used as a model. Assuming linear temperature gradients withT R=6000K andT opt=10000K, it is found thatT=12000K (1–0.74r/R), wherer is the distance from the center andR is the radius of the nebula.  相似文献   

15.
The recent evolution of the central star of the planetary nebula LMC-N66 is presented. Before 1987, it showed a weak continuum with aT eff120 000 K andL bol25 000L and in a few years it developed strong WR features (P Cygni line profiles in N v at 124.0 nm and C IV at 155.0 nm, wide Heii emission, etc.) typical of a WN 4.5. Additionally the stellar continuum increased by a large factor and the absolute visual magnitude of the star changed from + 1.24 in 1987 to–2.57 in January, 1995. The WR features and enhanced continuum, evidencing a powerful mass-loss event remained with small variations for more than 5 years. Recent ultraviolet and optical data shows that the mass-loss seems to have diminished abruptly in the last three months.  相似文献   

16.
The periodic variation of the equivalent width of Hei lines and of the magnetic field in six Bp stars is modeled by the oblique rotator model. The position of the magnetic poles and the structure of the helium distribution has been determined from the magnetic field observations and the line strength measurements of the Hei 4026 line. A comparison between the helium surface distribution and the structure of the magnetic field has been carried out.  相似文献   

17.
Direct images of the Sun were photographed in continuum emission centered at 6900 Å by the jumping film method near the second contact of the Mexico eclipse on 7 March 1970. The band width was 150 Å defined by a combination of a sharp cut filter and KODAK IV F film. The intensity distribution of the solar outer layers obtained shows a steep decrease by a factor of 0.9 in logarithmic units around 2500 km. This is interpreted as the boundary of the chromosphere and corona. Spicules observed at 3500 km are explained by log n e = 11.25 and T e 6000 K. Discussions are made in relation to the other observations and some chromosphere models.  相似文献   

18.
An electron temperature estimate based on the absoluteB H/B[Nii] ratio is established over this part of the IC 1318 b, c, complex for which the absorption of light by dust is demonstrably low. This estimate gives an electron temperature of 6900 K±1200 K. Contour maps showing the overall distribution of the electron temperatureT e for constantf(=N(N+)/N(N)) and the overall distribution off for constantT e are also produced. The limitations of the method and the validity of the results are also discussed.  相似文献   

19.
Linear polarization of radiation emitted by tidally distorted stars as a function of the binary system phase is computed, taking into account true absorption and the scattering of light on free and bound electrons within hot stellar atmospheres. Computations are made both for the linear distribution of true sources across the atmospheres and for radiative-stable model atmospheres presented by Kurcuzet al. (1974) and Kurucz (1979). Polarization variability was investigated as a function of wavelength . In a number of cases, polarization variability was found to be at an observable level. The most marked variability was expected in the ultraviolet range adjacent to the boundaries of the spectral series for H and He. Near the Lyman limit of approximately =912 Å for stars with an effective temperatureT eff35 000 K and near the ionization boundary for HeII 226 Å for stars withT eff>35 000 K, the amplitude of polarization variability is greater than in the case of pure electron atmospheres, sometimes reaching the level of 0.5–1%. For fairly long waves where the limb-darkening coefficient falls below a certain critical valueu cr0.5, the plane of polarization is found to be turned by 90° as compared to the case of a pure electron atmosphere. For limb-darkening coefficients far from the value ofu cr; the form of the polarization phase curves, as well as dependence on the parameters of a binary system, remain approximately the same as those in the case of pure electron scattering.  相似文献   

20.
Quiescent prominences It is found that Heii 4686 is emitted in the same cold region of 10000 K as hydrogen, metal and neutral helium emission lines. This conclusion is based on the finding that the observed width of 4686 is the same as the calculated width of 4686. The calculated width is derived from the observed widths of hydrogen and metallic lines. The large intensity of Heii 4686 in 10000 K can be explained by the ionization of Heii due to the UV radiation below 228 Å that comes from the corona and the transition region.Loop prominences The very broad width (30 to 50 km s–1) of 4686 for two post-flare loop prominences shows that the Heii line is emitted in hot regions different from regions of hydrogen and metal emission. From the widths of the Balmer lines and many metallic lines the kinetic temperature for one loop is found to be 16000 K in one part and 7600 K in another part. The electron densities are 1012.0 cm–3 and less than 1011.0 cm–3 respectively.Chromosphere The intensity of 4686 in the chromosphere can be interpreted in terms of a temperature of 10000 K with the ionization due to UV radiation. But, since observations of the width of 4686 are not available, a definitive conclusion for the chromosphere cannot be reached.  相似文献   

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