Multilevel NLTE radiative transfer in isolated atmospheric structures: implementation of the MALI-technique.
Abstract
We have developed and extensively tested a new multilevel NLTE transfer code for isolated solar atmospheric structures (loops, prominences, spicules etc.). The code is based on the MALI approach of Rybicki & Hummer (1991, 1992) to multilevel accelerated lambda iterations. It is demonstrated that this method is fully capable of treating a difficult problem of NLTE hydrogen excitation and ionization equilibrium, provided that we linearize the preconditioned statistical equilibrium equations with respect to atomic level populations and the electron density. With this generalization of the original MALI approach, the numerical code is robust and stable. As compared to the standard linearization method of Auer & Mihalas (1969), the new MALI code designed for 1D slabs is more than one order of magnitude faster and its accuracy is quite satisfactory. We discuss several details of our implementation of the MALI technique to isolated, externally irradiated, 1D structures and finally draw some future prospects.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1995
- Bibcode:
- 1995A&A...299..563H
- Keywords:
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- NLTE RADIATIVE TRANSFER;
- METHODS: NUMERICAL;
- SUN: PROMINENCES