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An Operator Perturbation Method for Polarized Line Transfer

IV. Applications to the Hanle effect with partial frequency redistribution
  • K. N. Nagendra
  • F. Paletou
  • H. Frisch
  • M. Faurobert-Scholl
Part of the Astrophysics and Space Science Library book series (ASSL, volume 243)

Abstract

In this paper we present an operator perturbation method to solve the Hanle effect problem in one-dimensional (1D) media with partial frequency redistribution (PRD) and assuming a two-level atom without ground-level polarization. This is a generalization of our PALI-H method (Nagendra et al., 1998) to the case of PRD. We make use of the Fourier azimuthal decomposition of the radiation field to treat the non axi-symmetry caused by the presence of an arbitrarily oriented magnetic field. We work with the approximation that frequency redistribution is decoupled from angular redistribution.

The numerical scheme employed for the solution of the line transfer problem is an extension of the scalar core-wing technique of Paletou and Auer (1995) to the Hanle effect case. This core-wing technique efficiently handles the frequency dependence of the PRD source vector.

We discuss the accuracy and speed of the method by comparing the results with those obtained from different methods on a few simple benchmarks. We also show that the PALI-H method can easily solve polarized line transfer problems in realistic 1D model atmospheres. The abbreviation PALI-H stands for Polarized Approximate Lambda Iteration method, in the presence of a magnetic field.

Key words

polarization magnetic fields radiative transfer scattering stars: atmospheres methods: numerical 

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Copyright information

© Springer Science+Business Media Dordrecht 1999

Authors and Affiliations

  • K. N. Nagendra
    • 1
    • 2
  • F. Paletou
    • 2
  • H. Frisch
    • 2
  • M. Faurobert-Scholl
    • 2
  1. 1.Indian Institute of AstrophysicsBangaloreIndia
  2. 2.Département G.D. Cassini, (CNRS/UMR 6529)Observatoire de la Côte d’AzurNice Cedex 4France

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