Modeling the scattering polarization of the solar Ca i 4227 Å line with angle-dependent partial frequency redistribution

Abstract

Context. The correct modeling of the scattering polarization signals observed in several strong resonance lines requires taking partial frequency redistribution (PRD) phenomena into account. Aims. This work aims at assessing the impact and the range of validity of the angle-averaged AA approximation with respect to the general angle-dependent (AD) treatment of PRD effects in the modeling of scattering polarization in strong resonance lines, with focus on the solar Ca i 4227 Å line. Methods. Spectral line polarization is modeled by solving the radiative transfer problem for polarized radiation, under nonlocal thermodynamic equilibrium conditions, taking PRD effects into account, in static one-dimensional semi-empirical atmospheric models presenting arbitrary magnetic fields. The problem is solved through a two-step approach. In step 1, the problem is solved for intensity only, considering a multi-level atom. In step 2, the problem is solved including polarization, considering a two-level atom with an unpolarized and infinitely sharp lower level, and fixing the lower level population calculated at step 1. Results. The results for the Ca i 4227 Å line show a good agreement between the AA and AD calculations for the Q/I and U/I wings signals. However, AA calculations reveal an artificial trough in the line-core peak of the linear polarization profiles, whereas AD calculations show a sharper peak in agreement with observations. Conclusions. An AD treatment of PRD effects is essential to correctly model the line-core peak of the scattering polarization signal of the Ca i 4227 Å line. By contrast, in the considered static case, the AA approximation seems to be suitable to model the wing scattering polarization lobes and their magnetic sensitivity through magneto-optical effects.

References in corpus (29)

• The polarization of the solar MgII h and k lines
• Fast approximation of angle-dependent partial redistribution in moving atmospheres
• Mapping Solar Magnetic Fields from the Photosphere to the Base of the Corona
• Discovery of Scattering Polarization in the Hydrogen Lyman-$\alpha$ Line of the Solar Disk Radiation
• Partial redistribution in 3D non-LTE radiative transfer in solar atmosphere models
• 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
• The scattering polarization of the Ly-alpha lines of H I and He II taking into account PRD and J-state interference effects
• 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
• CLASP Constraints on the Magnetization and Geometrical Complexity of the Chromosphere-Corona Transition Region
• The transfer of resonance line polarization with partial frequency redistribution and J-state interference
• Formal Solutions for Polarized Radiative Transfer. I. The DELO Family
• The effects of three-dimensional radiative transfer on the resonance polarization of the Ca I 4227 $\mathring{\mathrm{A}}$ line
• Center to limb observations and modeling of the Ca I 4227 A line
• Magneto-optical effects in the scattering polarization wings of the Ca I resonance line at 4227 angstroms
• Observations of the forward scattering Hanle effect in the Ca i 4227 Å line
• Solving the paradox of the solar sodium D1 line polarization
• Formal solutions for polarized radiative transfer. III. Stiffness and instability
• Numerical solutions to linear transfer problems of polarized radiation II. Krylov methods and matrix-free implementation
• Explicit Form of the Radiative and Collisional Branching Ratios in Polarized Radiation Transport with Coherent Scattering
• Formal Solutions for Polarized Radiative Transfer. IV. Numerical Performances in Practical Problems
• Radiative transfer modeling of the enigmatic scattering polarization in the solar NaI D1 line
• Magnetic sensitivity in the wing scattering polarization signals of the hydrogen Lyman-alpha line of the solar disk radiation
• Spatio-temporal evolution of Hanle and Zeeman synthetic polarization in a chromospheric spectral line
• On the Sensitivity of Partial Redistribution Scattering Polarization Profiles to Various Atmospheric Parameters
• Numerical solutions to linear transfer problems of polarized radiation I. Algebraic formulation and stationary iterative methods
• An efficient decomposition technique to solve angle-dependent Hanle scattering problems
• Observational indications of magneto-optical effects in the scattering polarization wings of the Ca I 4227 Å line

Cited by in corpus (5)

• Numerical solutions to linear transfer problems of polarized radiation I. Algebraic formulation and stationary iterative methods
• 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
• The potential of the wavelength-integrated scattering polarization of the hydrogen Ly-alpha line for probing the solar chromosphere