Effects of Spatial Discretization in Lyα Line Radiation Transfer Simulations

We present detailed line-by-line radiation transfer calculations, which were performed under different atmospheric conditions for the most important greenhouse gases water vapor, carbon dioxide, methane, and ozone. Particularly cloud effects, surface temperature variations, and humidity changes as well as molecular lineshape effects are investigated to examine their specific influence on some basic climatologic parameters like the radiative forcing, the long wave absorptivity, and back-radiation as a function of an increasing CO2 concentration in the atmosphere. These calculations are used to assess the CO2 global warming by means of an advanced two-layer climate model and to disclose some larger discrepancies in calculating the climate sensitivity. Including solar and cloud effects as well as all relevant feedback processes our simulations give an equilibrium climate sensitivity of CS = 0.7°C (temperature increase at doubled CO2) and a solar sensitivity of SS = 0.17°C (at 0.1% increase of the total solar irradiance). Then CO2 contributes 40% and the Sun 60% to global warming over the last century.

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Line radiation transfer in non-equilibrium laser plasma

Laser and Particle Beams ◽

10.1017/s0263034600005644 ◽

1988 ◽

Vol 6 (4) ◽

pp. 703-708

Author(s):

S. I. Kaśkova ◽

G. S. Romanov ◽

K. L. Stepanov

Keyword(s):

Spectral Line ◽

Source Function ◽

Radiation Transfer ◽

Resonance Scattering ◽

Plasma Radiation ◽

Line Profiles ◽

Radiation Characteristics ◽

Laser Target ◽

Line Radiation ◽

Frequency Redistribution

The self-radiation characteristics of plasma created under the effect of a powerful laser radiation on a target are considered. The radiation in the spectral range from 1 to 1300 Å is calculated in coherent assumption for given gas-dynamic fields corresponding to various phases of laser target explosion. The source function was determined in accordance with a plasma radiation-collision model with the assumption of its transparency. Calculations show that the contribution of line radiation to the total flux may be from 20 to 60%. Mainly, this paper considers radiation transfer. The effect of self-radiation on level populations and frequency redistribution at resonance scattering is taken into account. The resonance scattering is predominant in the coronal plasma. Exit of photons from deeper layers of the target in comparison with the coherent case increases. Macroscopic plasma motion leading to spectral line shift is taken into consideration in the calculations. Output radiation spectral intensity distribution in oxygen and silicon H-like ions resonance lines has been determined. Spectral line profiles calculated with account of basic broadening mechanisms were used.

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Some Problems of Solar Quiescent Prominences in the Light of Ambartsumian’s Ideas

Communications of the Byurakan Astrophysical Observatory ◽

10.52526/25792776-2018.2.2-279 ◽

2018 ◽

pp. 279-290

Author(s):

A. Nikoghossian

Keyword(s):

Radiation Transfer ◽

Temporal Variations ◽

Line Profiles ◽

Line Radiation ◽

Line Intensities ◽

Different Types ◽

Physical Features ◽

Transfer Problems ◽

Euv Spectrum

The report is a brief overview of our results in the theory of spectral line formation in atmospheres with complex fine structure. The research motivation was due to interpretation of the EUV spectrum of solar quiescent prominences observed with the SUMER spectrograph as a part of the SOHO space program. We describe the methods proposed for solving the line-radiation transfer problems in multicomponent atmospheres which use Ambartsumian's ideas proposed in the theory of radiation transfer and its applications. It is demonstrated that even the simplest static model radiating medium composed of physically different types of elements shows line profiles differing from those formed in the medium with preliminarily averaged properties. The more realistic and complicated case of a multicomponent atmosphere with randomly varying properties is considered with special attention paid to the effect of the velocity field. An important role of the relative mean square deviation of observed line intensities in the diagnostics of physical features of spatial and temporal variations of prominences is shown.

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36. Theory of Stellar Atmospheres (Theorie des Atmospheres Stellaires

Transactions of the International Astronomical Union ◽

10.1017/s0251107x00027887 ◽

1997 ◽

Vol 23 (1) ◽

pp. 303-309

Keyword(s):

Mass Loss ◽

Atomic Physics ◽

Radiation Transfer ◽

Hydrostatic Equilibrium ◽

Stellar Atmospheres ◽

Recent Past ◽

Line Radiation ◽

Transfer Line ◽

Made In ◽

Magnetic Phenomena

Consistently with a trend observed in recent past triennial reports, progress in the theory of stellar atmospheres continues to be made in two different directions: (i) the traditional areas of continuum and line radiation transfer, line blanketing, atomic physics and atmospheric structures controlled by the joint conditions of radiative and hydrostatic equilibrium, and (ii) in areas of emerging interest such as oscillations, winds and mass loss, chromospheres, coronae and magnetic phenomena.

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Commission 36: Theory of Stellar Atmospheres: (Theorie des Atmospheres Stellaires)

Transactions of the International Astronomical Union ◽

10.1017/s0251107x00002935 ◽

2000 ◽

Vol 24 (1) ◽

pp. 219-230

Author(s):

R. Pallavicini ◽

D. Dravins ◽

B. Barbuy ◽

L. Cram ◽

I. Hubeny ◽

...

Keyword(s):

Radiation Transfer ◽

Accurate Determination ◽

Stellar Atmospheres ◽

Recent Past ◽

Line Radiation ◽

Chemical Enrichment ◽

Elemental Abundances ◽

The Galaxy ◽

Made In

Consistently with a trend observed in recent past triennial reports, progress in the theory of stellar atmospheres continues to be made in two different directions: 1) the traditional areas of continuum and line radiation transfer, line blanketing, atomic physics and atmospheric structures controlled by the joint conditions of radiative and hydrostatic equilibrium, and 2) in areas of emerging interest such as oscillations, velocity fields, winds and mass loss, chromospheres, coronae and magnetic phenomena. Particular attention is devoted also to the accurate determination of stellar elemental abundances and their implications for stellar interior structure and evolution as well as for the chemical enrichment of the Galaxy.

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