The transfer of polarized radiation in resonance lines with partial frequency redistribution, J-state interference, and arbitrary magnetic fields. A radiative transfer code and useful approximations

Abstract

We present the theoretical framework and numerical methods we have implemented to solve the problem of the generation and transfer of polarized radiation in spectral lines out of local thermodynamical equilibrium, while accounting for scattering polarization, partial frequency redistribution, J-state interference, and hyperfine structure. The resulting radiative transfer code allows modeling the impact of magnetic fields of arbitrary strength and orientation through the Hanle, incomplete Paschen-Back, and magneto-optical effects. We also evaluate the suitability of a series of approximations for modeling the scattering polarization in the wings of strong resonance lines that would be particularly useful for the numerically intensive case of three-dimensional radiative transfer. We examine the suitability of the considered approximation using our radiative transfer code to model the Stokes profiles of the Mg II h & k lines and of the H I Lyman alpha line in magnetized one-dimensional models of the solar atmosphere. Neglecting Doppler redistribution in the scattering processes that are unperturbed by elastic collisions produces a negligible error in the scattering polarization wings of the Mg II resonance lines and a minor one in the Lyman alpha wings, although it is unsuitable to model the cores of these lines. For both lines, the scattering processes that are perturbed by elastic collisions give a significant contribution only to the intensity component of the emissivity. Neglecting collisional as well as Doppler redistribution represents a rough but suitable approximation for the wings of the Mg II resonance lines, but a very poor one for the Lyman alpha wings. The magnetic sensitivity in the scattering polarization wings of the considered lines can be modeled by accounting for the magnetic field only in the eta I and rho V coefficients of the Stokes-vector transfer equation.

Accepted for publication in the journal Astronomy & Astrophysics. Main text has 14 pages and 7 figures. The appendices (divided into Appendix A, B, and C) have 13 pages and 5 figures (contained in Appendix B)

References in corpus (14)

• Magnetic Diagnostics of the Solar Chromosphere with the Mg II h-k Lines
• Mapping Solar Magnetic Fields from the Photosphere to the Base of the Corona
• The magnetic sensitivity of the Mg ii k line to the joint action of Hanle, Zeeman and magneto-optical effects
• The magnetic sensitivity of the resonance and subordinate lines of Mg II in the solar chromosphere
• Frequency Redistribution Function for the Polarized Two-Term Atom
• The transfer of resonance line polarization with partial frequency redistribution in the general Hanle-Zeeman regime
• The transfer of resonance line polarization with partial frequency redistribution and J-state interference
• Formal Solutions for Polarized Radiative Transfer. I. The DELO Family
• Master equation theory applied to the redistribution of polarized radiation in the weak radiation field limit. V. The two-term atom
• Numerical solutions to linear transfer problems of polarized radiation II. Krylov methods and matrix-free implementation
• Solving the paradox of the solar sodium D1 line polarization
• Explicit Form of the Radiative and Collisional Branching Ratios in Polarized Radiation Transport with Coherent Scattering
• Depolarizing collisions with hydrogen: neutral and singly ionized alkaline earths
• A Note on the Radiative and Collisional Branching Ratios in Polarized Radiation Transport with Coherent Scattering

Cited by in corpus (8)

• The circular polarization of the Mn I resonance lines around 280 nm for exploring chromospheric magnetism
• Optimal spectral lines for measuring chromospheric magnetic fields
• Assessment of the CRD approximation for the observer's frame RIII redistribution matrix
• A numerical approach for modelling the polarisation signals of strong resonance lines with partial frequency redistribution. Numerical applications to two-term atoms and plane-parallel atmospheres
• Diagnostic potential of wavelength-integrated scattering polarisation signals of the solar He II Ly-alpha line
• Collisional effects in modeling solar polarized lines
• The magnetic sensitivity of the Ca II resonance and subordinate lines in the solar atmosphere
• The potential of the wavelength-integrated scattering polarization of the hydrogen Ly-alpha line for probing the solar chromosphere