Influence of atomic polarization and horizontal illumination on the Stokes profiles of the He I 10830 multiplet

Abstract

The polarization observed in the spectral lines of the He I 10830 multiplet carries valuable information on the dynamical and magnetic properties of plasma structures in the solar chromosphere and corona, such as spicules, prominences, filaments, emerging magnetic flux regions, etc. Here we investigate the influence of atomic level polarization on the emergent Stokes profiles for a broad range of magnetic field strengths, in both 90 degree and forward scattering geometry. We show that, contrary to a widespread belief, the selective emission and absorption processes caused by the presence of atomic level polarization may have an important influence on the emergent linear polarization, even for magnetic field strengths as large as 1000 G. Consequently, the modeling of the Stokes Q and U profiles should not be done by taking only into account the contribution of the transverse Zeeman effect within the framework of the Paschen-Back effect theory, unless the magnetic field intensity of the observed plasma structure is sensibly larger than 1000 G. We point out also that in low-lying optically thick plasma structures, such as those of active region filaments, the (horizontal) radiation field generated by the structure itself may substantially reduce the positive contribution to the anisotropy factor caused by the (vertical) radiation field coming from the underlying solar photosphere, so that the amount of atomic level polarization may turn out to be negligible. Only under such circumstances may the emergent linear polarization of the He I 10830 multiplet in such regions of the solar atmosphere be dominated by the contribution caused by the transverse Zeeman effect.

Accepted for publication in The Astrophysical Journal (It is tentatively scheduled for the ApJ January 20, 2007 issue)

Cited by in corpus (16)

• Advanced Forward Modeling and Inversion of Stokes Profiles Resulting from the Joint Action of the Hanle and Zeeman Effects
• Radiative diagnostics in the solar photosphere and chromosphere
• The influence of coronal EUV irradiance on the emission in the He I 10830 A and D3 multiplets
• The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He I 10830 A triplet
• Spectropolarimetric analysis of an active region filament. I. Magnetic and dynamical properties from single component inversions
• Height variation of the vector magnetic field in solar spicules
• A Flare Observed in Coronal, Transition Region and Helium I 10830 Å Emissions
• Measuring the magnetic origins of solar flares, CMEs and Space Weather
• Spectropolarimetric analysis of an active region filament. II. Evidence of the limitations of a single component model
• Three-dimensional magnetic field structure of a flux emerging region in the solar atmosphere
• Time evolution of plasma parameters during the rise of a prominence instability
• Magnetized supersonic downflows in the chromosphere. A statistical study using the He I 10830 Å lines
• Spicule emission profiles observed in \ion{He}{i} 10830 Å
• Magnetic field diagnostics of prominences with the Mg II k line: 3D Stokes inversions versus traditional methods
• The He I 10830 A line: Radiative transfer and differential illumination effects
• Multi-wavelength spectropolarimetric observations of AR13724 performed by GRIS