scholarly journals Advanced Approach for Radiation Transport Description in 3D Collisional-radiative Models

2017 ◽  
Vol 4 (2) ◽  
pp. 112-115 ◽  
Author(s):  
D. Kalanov ◽  
Yu. B. Golubovskii ◽  
D. Uhrlandt ◽  
S. Gortschakow
Keyword(s):  
Radiation Transport ◽  
Finite Geometries ◽  
Balance Equations ◽  
Absorption Coefficients ◽  
Strict Solution ◽  
Wide Range ◽  
Radiation Transport Equation ◽  
Voxel Grid ◽  
Particle Balance ◽  
Traversal Algorithm

The description of radiation transport phenomena in the frames of collisional-radiative models requires the solution of Holstein-Biberman equation. An advanced solutuion method for 3D plasma obejcts is proposed. The method is applicable for various line contours in a wide range of absorption coefficients. Developed approach is based on discretization of the arbitrary plasma volume on a Cartesian voxel grid. Transport of photons between the cells is computed using the ray traversal algorithm by Amanatides [1]. Solution of the particle balance equations with computed in advance radiative transfer matrix is demonstrated for various typical arc shapes, like e.g. free-burning arc and cylindric arc. Results are compared with corresponding calculations using previously developed approaches. As the method is suited for finite geometries and allows for a strict solution of the radiation transport equation, applicability ranges of previous approximations can be specified.

scholarly journals Diurnal cycle of the dust instantaneous direct radiative forcing over the Arabian Peninsula

2015 ◽  
Vol 15 (16) ◽  
pp. 9537-9553 ◽  
Author(s):  
S. Osipov ◽  
G. Stenchikov ◽  
H. Brindley ◽  
J. Banks
Keyword(s):  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Surface Albedo ◽  
Arabian Peninsula ◽  
Extreme Values ◽  
Radiation Transport ◽  
Atmospheric Composition ◽  
Diurnal Variability ◽  
Wide Range ◽  
Direct Radiative Forcing

Abstract. In this study we attempted to better quantify radiative effects of dust over the Arabian Peninsula and their dependence on input parameters. For this purpose we have developed a stand-alone column radiation transport model coupled with the Mie, T-matrix and geometric optics calculations and driven by reanalysis meteorological fields and atmospheric composition. Numerical experiments were carried out for a wide range of aerosol optical depths, including extreme values developed during the dust storm on 18–20 March 2012. Comprehensive ground-based observations and satellite retrievals were used to estimate aerosol optical properties, validate calculations and carry out radiation closure. The broadband surface albedo, fluxes at the bottom and top of the atmosphere as well as instantaneous dust radiative forcing were estimated both from the model and observations. Diurnal cycle of the shortwave instantaneous dust direct radiative forcing was studied for a range of aerosol and surface characteristics representative of the Arabian Peninsula. Mechanisms and parameters responsible for diurnal variability of the radiative forcing were evaluated. We found that intrinsic variability of the surface albedo and its dependence on atmospheric conditions, along with anisotropic aerosol scattering, are mostly responsible for diurnal effects.

Comparison of perturbative and nonperturbative calculations for Urbach's law

1968 ◽  
Vol 46 (18) ◽  
pp. 2087-2089 ◽  
Author(s):  
Dennis Dunn ◽  
I. P. Batra
Keyword(s):  
Electron Energy ◽  
Weak Interaction ◽  
Electronic Absorption ◽  
Optical Phonon ◽  
Energy Gap ◽  
Phonon Energy ◽  
Optical Phonons ◽  
Absorption Coefficients ◽  
Wide Range ◽  
Nonperturbative Method

In many semiconductors and insulators electronic absorption occurs below the direct electron-energy gap, owing (we assume) to the interaction of electrons with optical phonons. In this paper we compare absorption coefficients, over a wide range of interaction strengths, calculated by two different prescriptions. The first method is a perturbative one, which takes into account only one-phonon processes, while the second is a nonperturbative method, which takes into account many-phonon processes.We find that for the (weak) interaction involved in InSb the two methods give essentially the same results for photon energies [Formula: see text] in the interval [Eg – kθ, Eg], where Eg is the energy gap and kθ is the optical phonon energy. For stronger interactions the perturbation results are nowhere applicable.

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