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Comparison of Discrete Space and Differential Equation Methods in Non-LTE Line Transfer Problems

Published online by Cambridge University Press:  08 February 2017

I. P. Grant  and
G. E. Hunt
I. P. Grant
Affiliation:
Science Research Council, Atlas Computer Laboratory Chilton, Didcot, Berkshire, England
G. E. Hunt
Affiliation:
Science Research Council, Atlas Computer Laboratory Chilton, Didcot, Berkshire, England

Abstract

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Numerical methods are essential to the treatment of line formation in inhomogeneous non-LTE atmospheres. The new methods due to Hummer and Rybicki and to Feautrier now make it possible to make such calculations, although these are often quite timeconsuming.

We shall describe an alternative approach using discrete space techniques depending on concpets of invariance. The solution algorithm is closely related to the method of Hummer and Rybicki, whose equations are obtained as a limiting case. The stability and errors of our algorithm are susceptible to mathematical analysis, and make it possible to identify the critical parameters in the calculation with precision. The results for a two-level problem will be compared with those from an implementation of the Rybicki-Hummer equations and a comparison will be made of the performance of the two procedures in respect of speed of computation and storage requirements.

Keywords

line formatioinhomogeneous non-LTE atmospherenumerical methods
Type
Part B. Theoretical Methods for Handling Non-LTE Problems
Information
International Astronomical Union Colloquium , Volume 2: Spectrum Formation in Stars With Steady-State Extended Atmospheres , August 1970 , pp. 189 - 225
Copyright
Copyright © 1970

References

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