Resonance Line Polarization for Arbitrary Magnetic Fields in Optically Thick Media. II - Case of a Plane-Parallel Atmosphere and Absence of Zeeman Coherences
Résumé
The general problem of resonance scattering for a two-level atom in a magnetized plane-parallel atmosphere is formulated by using the irreducible tensor representation of the atomic density matrix. A more general formalism presented in a previous paper (Paper I), convenient for taking into account arbitrary magnetic field effects (Zeeman effect as well as Hanle effect), is particularized in the present paper to the case of a "strong" magnetic field (Zeeman splitting much larger than the natural width of the upper level), and to the case of a unidimensional medium. A system of coupled integral equations, relating the density matrix elements at different depths in the atmosphere, is derived, and the properties of the relative kernels are discussed. It is shown that, in the limiting case of weak magnetic fields (VL ≪ ΔνD), the presence of atomic polarization induces a breakdown in the usual formula V(ν) = -gνL(dI/dν), that is commonly used for measuring magnetic fields from magnetograph-type observations.
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