Scattering Polarization in the Ca II Infrared Triplet with Velocity Gradients

Carlin, E. S.; Manso-Sainz, R.; Asensio-Ramos, A.; Trujillo-Bueno, J.
Bibliographical reference

The Astrophysical Journal, Volume 751, Issue 1, article id. 5 (2012).

Advertised on:
5
2012
Number of authors
4
IAC number of authors
4
Citations
34
Refereed citations
24
Description
Magnetic field topology, thermal structure, and plasma motions are the three main factors affecting the polarization signals used to understand our star. In this theoretical investigation, we focus on the effect that gradients in the macroscopic vertical velocity field have on the non-magnetic scattering polarization signals, establishing the basis for general cases. We demonstrate that the solar plasma velocity gradients may have a significant effect on the linear polarization produced by scattering in chromospheric spectral lines. In particular, we show the impact of velocity gradients on the anisotropy of the radiation field and on the ensuing fractional alignment of the Ca II levels, and how they can lead to an enhancement of the zero-field linear polarization signals. This investigation remarks on the importance of knowing the dynamical state of the solar atmosphere in order to correctly interpret spectropolarimetric measurements, which is important, among other things, for establishing a suitable zero-field reference case to infer magnetic fields via the Hanle effect.
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Magnetism, Polarization and Radiative Transfer in Astrophysics
Magnetic fields pervade all astrophysical plasmas and govern most of the variability in the Universe at intermediate time scales. They are present in stars across the whole Hertzsprung-Russell diagram, in galaxies, and even perhaps in the intergalactic medium. Polarized light provides the most reliable source of information at our disposal for the
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