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1.
The absorption spectrum and thermal radiation fluxes are calculated for the lower atmosphere of Venus in the far-wing approximation based on the theory of the collisional broadening of spectral lines. The results are in good agreement with the available experimental data. An outgoing thermal radiation flux is about 2.6 W/m2 near the planetary surface. This indicates that free convection significantly contributes to the thermal balance of the lower troposphere. The fluxes obtained in this study were compared to those calculated on the basis of empirical models of the spectral line profile. It was shown that the far wings of the CO2 lines considerably affect the radiative transfer in the transparency windows. This effect becomes weaker when the contribution of the absorption of minor constituents, primarily water vapor, increases. The profiles of absorption lines of minor constituents do not influence the thermal radiation fluxes.__________Translated from Astronomicheskii Vestnik, Vol. 39, No. 3, 2005, pp. 214–226.Original Russian Text Copyright © 2005 by Afanasenko, Rodin.  相似文献   

2.
Multiple resonance scattering of radiation in a spectrum line with absorption in the continuum is examined. It is assumed that the scattering atmosphere is semi-infinite and that there is no magnetic field or continuum emission at the frequencies of the spectrum line. The polarization characteristics of the emerging radiation are determined for unpolarized primary radiation sources distributed uniformly within an atmosphere in the case of a Voigt absorption profile. The calculations employ an iterative solution of the Ambartsumyan-Chandrasekhar matrix integral equation.  相似文献   

3.
We have investigated the effects of Compton broadening due to electron scattering in an expanding stellar atmospheres. The line transfer equation is solved by including the second approximation of Edmonds (Astrophys. J. 119:58, 1954) which is due to Compton broadening and obtained the line profiles in (1) plane parallel (PP) (2) spherical (SS) atmospheres. The effect on spectral line formation is studied for different parameters like (a) optical depths (b) densities (c) frequencies (d) temperatures (e) thickness of the atmosphere and (f) expanding velocities. Various combination of the above parameters are used in computing the line profiles observed at infinity. Line profiles are compared for the above said parameters. It is noticed that the expansion of the gases in the atmosphere produces P-Cygni type profiles and at higher optical depths the line profiles change from emission to absorption with their line centers shifting to blue side in the expanding atmospheres.  相似文献   

4.
Spectral lines formed in a rotating and expanding atmosphere have been computed in the frame of the observer at infinity. Two kinds of velocity laws are employed: (i) a uniform radial velocity of the gas and (ii) velocity increasing with radius (i.e. velocity gradients). The atmosphere has been assumed to be rotating with constant velocity. We have considered maximum radial and rotational velocities to be 10 and 3 mean thermal units respectively in an atmosphere whose geometrical thickness is 10 times the stellar radius. The total radial optical depth at line centre is taken to be about 100. In all cases, Doppler profile and a source function which is varying as 1/r 2 have been used. Generally, the lines are broadened when rotation is introduced. However, when radial motion is also present, broadening becomes asymmetric and the red emission and blue absorption are enhanced.  相似文献   

5.
Results of an effort to provide to astrophysicists and physicists a set of Stark broadening parameters that is as complete as possible are presented. Such parameters are needed for stellar opacity calculations, stellar atmosphere modelling, abundance determinations, and diagnostics of various plasmas in astrophysics, physics, and plasma technology. The Stark broadening was treated using a semiclassical perturbation and modified semiempirical approaches.  相似文献   

6.
There are abundant emission and absorption lines superimposed on the continuum spectra of the different solar atmospheric layers. The chemical composition and physical state of the solar atmosphere can be probed by the inversion of the profiles of these spectral lines. Due to the low density and large temperature difference in the chromosphere and transition region of the Sun, it is hard to establish the thermal dynamic equilibrium. It is necessary to adopt the theory of Non-Local Thermodynamic Equilibrium (N-LTE) to construct the corresponding atmospheric model. In this paper, the departure from the Local Thermodynamic Equilibrium (LTE) in the middle and lower atmosphere of the sun is investigated with the well-defined relative departure factor and the relevant calculations. We first make an inversion of the spectral lines formed at the different heights in the chromosphere and transition region during a total solar eclipse, to obtain the parameters of the observed spectral lines, such as the continuum source function, line source function, Doppler width, and thus the equivalent kinetic temperature. According to these line parameters obtained by the inversion, we calculate the quantitative results about the departure from the LTE at each space sampling point in the 2D field of view. Secondly, we reconstruct the 2D distributions of the radiation intensity, equivalent kinetic temperature, and relative departure factor according to the alignment of the optical fiber array in the integrated field unit (IFU) used by the telescope. The results show that there is a stronger correlation in the distributions of the temperature and relative departure factor existed in local small regions, but without evident correlation with the distribution of radiation intensity. There is an obvious difference between the distributions of the equivalent temperature and relative departure factor derived from two spectral lines, which shows a strong structurization and complexity existed in some local small regions of the solar atmosphere, and provides a new perspective for us to further understand the physics of the middle and lower atmosphere of the Sun.  相似文献   

7.
The polarized radiative transfer equation is solved when angle-dependent partial redistribution and non-coherent electron scattering are included as line-scattering mechanisms. A static atmosphere with plane parallel symmetry is assumed. Test calculations are used to illustrate the effects of the electron-scattering coefficient, the thermalization parameter and the continuous absorption coefficient on the line polarization. Results of angle-averaged and angle-dependent redistribution functions are compared and it is shown that angle-dependent functions should be used to model the wing polarization of optically thin lines. The lower the continuous absorption compared with the electron scattering, the higher the wing polarization.  相似文献   

8.
As part of a study of satellite thermal control, data were obtained on earth-reflected solar radiation and on the stability of thermal-control coatings. The intensity distribution of incoming solar radiation to earth was found to be shifted toward the ultraviolet region upon reflection by the atmosphere. As a result of the shift, the intensity of reflected radiation reaches a maximum in the near ultraviolet. At shorter wavelengths in the ultraviolet region, the intensity drops sharply to zero as a result of absorption of incoming radiation by ozone in the upper atmosphere. Comparisons of calculated intensity distributions with measured distributions for two different atmospheric conditions gave good agreement, except at the shorter ultraviolet wavelengths where the calculations did not adequately include the effect of ozone absorption. Measurements of stability of thermal-control coatings showed a lower degradation rate of white paints than was obtained on other flight experiments flown outside of the protective influence of earth's magnetosphere. The differences in degradation rate were much larger than expected, indicating that further study is required in the development of white coatings for spacecraft thermal control.  相似文献   

9.
A theoretical study of the influence of propagating acoustic pulses in the solar chromosphere upon the line profiles of the Ca ii resonance and infrared triplet lines has been made. The major objective has been to explain the observed asymmetries seen in the cores of the H and K lines and to predict the temporal behavior of the infrared lines caused by passing acoustic or shock pulses. The velocities in the pulses, calculated from weak shock theory, have been included consistently in the non-LTE calculations. The results of the calculations show that these lines are very sensitive to perturbations in the background atmosphere caused by the pulses. Only minor changes in the line shapes result from including the velocities consistently in the line source function calculations. The qualitative changes in the line profiles vary markedly with the strength of the shock pulses. The observed differences in the K line profiles seen on the quiet Sun can be explained in terms of a spectrum of pulses with different wave-lengths and initial amplitudes in the photosphere.  相似文献   

10.
A general expression for the gravity darkening of the tidally and non-uniformly rotating Roche components of close binary systems is used to calculate the uniform rotational effects on line profiles in an expanding atmosphere. We consider a non-local thermodynamic equilibrium (non-LTE) two-level atom approximation in an extended atmosphere, and use Von Zeipel's theorem for the incident radiation at the maximum optical depth  (τ=τmax)  in the atmosphere. These calculations are performed with uniform rotational velocities of 1, 4 and 8 mtu (mean thermal units). It is found that rotation dilutes the radiation field which is similar to the expansion velocity.
We also study rotational aspects, which make the outer layers of the star distorted. The equation of line transfer is solved in the comoving frame of the expanding atmosphere of the primary using complete redistribution in the line. We use a linear law for the velocity of expansion such that the density varies as r −3, where r is the radius of the star, satisfying the law of conservation of mass. It is found that rotation broadens the line profile, and P-Cygni-type line profiles are obtained.  相似文献   

11.
The formation of spectral lines in a homogeneous magnetic field has been studied. A new method for solving the transfer equations for polarized light has been found. Using this method, the Stokes parameters may be derived without any special assumptions regarding the model atmosphere. With the line formed by pure absorption, the expressions for the Stokes parameters may easily be adapted to numerical calculations. In order to illustrate the method, the line profile for the Zeeman triplet 5250 has been calculated using a photospheric model atmosphere.  相似文献   

12.
The theory of Anstee &38; O'Mara is extended to the line broadening of transitions of singly ionized atoms by collisions with neutral hydrogen atoms. The theory is used to calculate broadening cross-sections for strong lines of singly ionized calcium, magnesium and barium. The broadening cross-sections calculated are compared with both theoretical and empirical results of other workers.  相似文献   

13.
Using Cummack's model (in which non-linear terms are ignored) detailed calculations are carried out on the diurnal variations of planetary thermospheres. The dependences on the speed of rotation of the atmosphere; on the specific heat, the thermal conductivity and the absorption coefficient of the air; and on the pressure at the lower boundary, are separated. The diurnal variation of the terrestrial thermosphere is discussed. It is not yet possible to reach a firm conclusion as to whether or not non-linear terms have a major effect on this variation.  相似文献   

14.
An observational program to study variations of the vertical distribution of CO in the Venus atmosphere is presented. Measurements of the J = 0 → 1 absorption line at 2.6 mm wavelength are reported for two phase angles in 1977, one near eastern elongation (Feb.) and the other near inferior conjunction (Apr.). The two spectra are significantly different, with the April absorption line being narrower and deeper. The results of numerical inversion calculations show that the CO mixing ratio increases a factor of ～ 100 between 78 and 100 km and that the CO abundance above ～ 100 km is greatest on the night-side hemisphere. These conclusions are in qualitative agreement with theoretical models. In addition to the CO observations, a search for other molecules was made to provide further information on the composition of the Venus middle atmosphere. The J = 0 → 1 transition of 13CO was detected and upper limits were derived for nine other molecules.  相似文献   

15.
Observations of the scattering of acoustic waves by sunspots show a substantial deficit in scattered power relative to incident power. A number of calculations have attempted to model this process in terms of absorption at the magnetohydrodynamic Alfvén resonance. The results presented here extend these calculations to the case of a highly structured axisymmetric translationally invariant flux-tube embedded in a uniform atmosphere. The fractional energy absorbed is calculated for models corresponding to flux-tubes of varying radius, mean flux-density and location below the photosphere. The effects of twist are also included.It is found that absorption can be very efficient even in models with low mean magnetic flux density, provided the flux is concentrated into intense slender annuli. Twist is found to increase the range of wave numbers over which absorption is efficient, but it does not remove the low absorption at low azimuthal orders which is a feature of resonance absorption calculations in axisymmetric geometry, and which is in conflict with observation.These results suggest that resonance absorption could be an efficient mechanism in plage fields and fibril sunspots as well as in monolithic sunspots. At present it is too early to make any definite deductions about sunspot structure from the observations, but the possible future use of sunspot seismology to resolve open questions in the theory of sunspots is briefly discussed.  相似文献   

16.
Loughhead  R. E. 《Solar physics》1974,34(1):77-90
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17.
Microorganisms sealed in KBr discs have an absorption spectrum over the 2.5–15 μm waveband that shows thermal stability as they are heated in an inert atmosphere to temperatures of about400 °C. Microfossils tightly sealed within cavities in rocks could be endowed with similar properties of thermal stability. The observed absorption of interstellar material along the line of sight from the solar system to the galactic centre is remarkably similar to the spectrum of dry micro-organisms over the 3.15–3.7 μm waveband. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

18.
The reliability of results obtained through infrared spectroscopy by means of the KBr pellet pressing technique is examined for silicates, using MIE calculations. The embedding medium causes a distortion of the profile of the 10-μm band. The absorption coefficient may be enlarged by as much as 10 to 20 per cent. The absorption peak is shifted by 0.2 μm in the direction to larger wavelengths. Mass absorption coefficients are derived from laboratory spectra for submicrometer-sized particles of chamosite, chlorite, montmorillonite, serpentine, and talc. Chamosite and talc show the absorption peak at the wavelength position required by the observations. Concerning chlorite and montmorillonite the agreement seems to be tolerable. For each substance the band is, however, much too narrow in order to fit the observed profile. On the basis of the measured absorption coefficients and assuming an ad hoc broadening mechanism curves of growth are calculated. With the values for chamosite column densities of 10-4 to 2.5 · 10-3 g cm-2 for silicate dust are found in the line of sight toward infrared sources.  相似文献   

19.
Some physical mechanisms which can affect the Zeeman line profiles of magnetic white dwarfs are studied. The pure absorption polarization transfer equation is solved including these mechanisms. The broadening of lines in magnetic white dwarfs is briefly discussed.  相似文献   

20.
Absorption of solar radiation of wavelengths between 175 to 205 nm plays a fundamental role in the photochemistry of the middle atmosphere. Nitric oxide photodissociates in the δ(0-0) and δ(1-0) bands near 191 and 183 nm, respectively, initiating the primary mechanisms for NOx removal in the middle atmosphere. The spectrally rich Schumann-Runge (S-R) bands of O2 are the main source of atmospheric opacity at these wavelengths. A re-evaluation of O2 absorption has been made based on recent advances in understanding of S-R line shapes, leading to differences with conventional approaches assuming Voigt line profiles in line-by-line calculations of the O2 cross section. The new results are used to examine the impact of O2 transmission on the photodissociation of NO in the δ(0,0) and δ(1,0) bands.  相似文献   

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