Three-dimensional radiative transfer simulations of the scattering polarization of the hydrogen Ly$\alpha$ line in a MHD model of the chromosphere-corona transition region

Abstract

Probing the magnetism of the upper solar chromosphere requires measuring and modeling the scattering polarization produced by anisotropic radiation pumping in UV spectral lines. Here we apply PORTA (a novel radiative transfer code) to investigate the hydrogen Ly$\alpha$ line in a 3D model of the solar atmosphere resulting from a state of the art MHD simulation. At full spatial resolution the linear polarization signals are very significant all over the solar disk, with a large fraction of the field of view showing line-center amplitudes well above the 1% level. Via the Hanle effect the line-center polarization signals are sensitive to the magnetic field of the model's transition region, even when its mean field strength is only 15 G. The breaking of the axial symmetry of the radiation field produces significant forward-scattering polarization in Ly$\alpha$, without the need of an inclined magnetic field. Interestingly, the Hanle effect tends to decrease such forward-scattering polarization signals in most of the points of the field of view. When the spatial resolution is degraded, the line-center polarization of Ly$\alpha$ drops below the 1% level, reaching values similar to those previously found in 1D semi-empirical models (i.e., up to about 0.5%). The center to limb variation of the spatially-averaged polarization signals is qualitatively similar to that found in 1D models, with the largest line-center amplitudes at $\mu =\cos \theta \approx 0.4$ ($\theta$ being the heliocentric angle). These results are important, both for designing the needed space-based instrumentation and for a reliable interpretation of future observations of the Ly$\alpha$ polarization.

arXiv comment15 pages, 15 figures, accepted for publication in The Astrophysical Journal

References in corpus (15)

• The Interface Region Imaging Spectrograph (IRIS)
• The stellar atmosphere simulation code Bifrost
• The formation of the Halpha line in the solar chromosphere
• Non-equilibrium hydrogen ionization in 2D simulations of the solar atmosphere
• PORTA: A three-dimensional multilevel radiative transfer code for modeling the intensity and polarization of spectral lines with massively parallel computers
• The Structure and Dynamics of the Upper Chromosphere and Lower Transition Region as Revealed by the Subarcsecond VAULT Observations
• The Hanle Effect of the Hydrogen Ly-alpha Line for Probing the Magnetism of the Solar Transition Region
• The Ly-alpha profile and center-to-limb variation of the quiet Sun
• Scattering Polarization and Hanle Effect in Stellar Atmospheres with Horizontal Inhomogeneities
• The scattering polarization of the Ly-alpha lines of H I and He II taking into account PRD and J-state interference effects
• The Ly-alpha Lines of H I and He II: A Differential Hanle Effect for Exploring the Magnetism of the Solar Transition Region
• The Hanle effect of Ly$\alpha$ in an MHD model of the Solar Transition Region
• Temporal Evolution of the Scattering Polarization of the CaII IR Triplet in Hydrodynamical Models of the Solar Chromosphere
• Scattering Polarization of Hydrogen Lines in Weakly Magnetized Stellar Atmospheres I. Formulation and Application to Isothermal Models
• On the inversion of the scattering polarization and the Hanle effect signals in the hydrogen Lyman-$\alpha$ line

Cited by in corpus (30)

• A publicly available simulation of an enhanced network region of the Sun
• STiC -- A multi-atom non-LTE PRD inversion code for full-Stokes solar observations
• 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
• Three-dimensional modeling of chromospheric spectral lines in a simulated active region
• Magnetic field in atypical prominence structures: Bubble, tornado and eruption
• TIC: A Stokes inversion code for scattering polarization with partial frequency redistribution and arbitrary magnetic fields
• Casting the Coronal Magnetic Field Reconstruction Tools in 3D Using MHD Bifrost Model
• Temperature constraints from inversions of synthetic solar optical, UV and radio spectra
• Millimeter radiation from a 3D model of the solar atmosphere II. Chromospheric magnetic field
• CLASP Constraints on the Magnetization and Geometrical Complexity of the Chromosphere-Corona Transition Region
• Force-Free Field Reconstructions Enhanced by Chromospheric Magnetic Field Data
• Prospects of solar magnetometry - from ground and in space
• Study of the polarization produced by the Zeeman effect in the solar Mg I b lines
• Novel framework for the three-dimensional NLTE inverse problem
• The Formation of IRIS Diagnostics. IX. The Formation of the C I 135.58 Line in the Solar Atmosphere
• Numerical non-LTE 3D radiative transfer using a multigrid method
• Formal Solutions for Polarized Radiative Transfer. IV. Numerical Performances in Practical Problems
• New light on an old problem of the cores of solar resonance lines
• 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
• The dynamic chromosphere: pushing the boundaries of observations and models
• Inference of magnetic fields in inhomogeneous prominences
• Evidence for the Operation of the Hanle and Magneto-Optical Effects in the Scattering Polarization Signals Observed by CLASP2 Across the Mg II h and k Lines
• Solar Hα excess during Solar Cycle 24 from full-disk filtergrams of the Chromospheric Telescope
• Diagnostic potential of wavelength-integrated scattering polarisation signals of the solar He II Ly-alpha line
• Spectral Characteristics of the He I D3 Line in a Quiescent Prominence Observed by THEMIS
• A Statistical Inference Method for Interpreting the CLASP Observations
• The potential of the wavelength-integrated scattering polarization of the hydrogen Ly-alpha line for probing the solar chromosphere
• Magnetic Imaging of the Outer Solar Atmosphere (MImOSA): Unlocking the driver of the dynamics in the upper solar atmosphere