A generalized -law

The role of unphysical source terms in resonance line polarization transfer and its importance as an additional test of NLTE radiative transfer codes

¹ Astronomical Institute, Academy of Sciences of the Czech Republic, 251 65 Ondřejov, Czech Republic e-mail: stepan@asu.cas.cz
² LERMA, Observatoire de Paris–Meudon, CNRS UMR 8112, 5 place Jules Janssen, 92195 Meudon Cedex, France e-mail: [jiri.stepan;V.Bommier]@obspm.fr

Received: 4 October 2006
Accepted: 26 March 2007

Abstract

Context.A derivation of a generalized -law for nonthermal collisional rates of excitation by charged perturbers is presented.

Aims.Aim of this paper is to find a more general analytical expression for a surface value of the source function which can be used as an additional tool for verification of the non-LTE radiative transfer codes.

Methods.Under the impact approximation hypothesis, static, one-dimensional, plane-parallel atmosphere, constant magnetic field of arbitrary strength and direction, two-level atom model with unpolarized lower level and stimulated emission neglected, we introduce the unphysical terms into the equations of statistical equilibrium and solve the appropriate non-LTE integral equations.

Results.We derive a new analytical condition for the surface values of the source function components expressed on the basis of irreducible spherical tensors.