  The spectral line polarization encodes a wealth of information about the
thermal and magnetic properties of the solar atmosphere. Modeling the Stokes
profiles of strong resonance lines is, however, a complex problem both from the
theoretical and computational point of view, especially when partial frequency
redistribution (PRD) effects need to be taken into account. In this work, we
consider a two-level atom in the presence of magnetic fields of arbitrary
intensity (Hanle-Zeeman regime) and orientation, both deterministic and
micro-structured. Working within the framework of a rigorous PRD theoretical
approach, we have developed a numerical code which solves the full non-LTE
radiative transfer problem for polarized radiation, in one-dimensional models
of the solar atmosphere, accounting for the combined action of the Hanle and
Zeeman effects, as well as for PRD phenomena. After briefly discussing the
relevant equations, we describe the iterative method of solution of the problem
and the numerical tools that we have developed and implemented. We finally
present some illustrative applications to two resonance lines that form at
different heights in the solar atmosphere, and provide a detailed physical
interpretation of the calculated Stokes profiles. We find that in strong
resonance lines sensitive to PRD effects the magneto-optical terms of the
Stokes-vector transfer equation produce conspicuous U/I wing signals along with
a very interesting magnetic sensitivity in the wings of the linear polarization
profiles. We also show that the weak-field approximation has to be used with
caution when PRD effects are considered.
