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Non-LTE radiative transfer with lambda-acceleration - Convergence properties using exact full and diagonal lambda-operatorsWe 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.
Document ID
19930031951
Document Type
Reprint (Version printed in journal)
Authors
Macfarlane, J. J.
(Washburn Observatory Madison, WI, United States)
Date Acquired
August 15, 2013
Publication Date
October 1, 1992
Publication Information
Publication: Astronomy and Astrophysics
Volume: 264
Issue: 1
ISSN: 0004-6361
Subject Category
Astrophysics
Funding Number(s)
CONTRACT_GRANT: NAGW-2210
Distribution Limits
Public
Copyright
Other
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