Non-LTE radiative transfer with lambda-acceleration - Convergence properties using exact full and diagonal lambda-operators

Details Non-LTE radiative transfer with lambda-acceleration - Convergence properties using exact full and diagonal lambda-operators Non-LTE radiative transfer with lambda-acceleration - Convergence properties using exact full and diagonal lambda-operators

Oct 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992a%26a...264..153m&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 264, no. 1, p. 153-158.

Statistics

Computation

4

Nonequilibrium Thermodynamics, Particle Acceleration, Radiative Transfer, Stellar Atmospheres, Computational Astrophysics, Convergence, Stellar Models

Scientific paper

We investigate the convergence properties of Lambda-acceleration methods for non-LTE radiative transfer problems in planar and spherical geometry. Matrix elements of the 'exact' A-operator are used to accelerate convergence to a solution in which both the radiative transfer and atomic rate equations are simultaneously satisfied. Convergence properties of two-level and multilevel atomic systems are investigated for methods using: (1) the complete Lambda-operator, and (2) the diagonal of the Lambda-operator. We find that the convergence properties for the method utilizing the complete Lambda-operator are significantly better than those of the diagonal Lambda-operator method, often reducing the number of iterations needed for convergence by a factor of between two and seven. However, the overall computational time required for large scale calculations - that is, those with many atomic levels and spatial zones - is typically a factor of a few larger for the complete Lambda-operator method, suggesting that the approach should be best applied to problems in which convergence is especially difficult.

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