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Publication type: Article in scientific journal
Type of review: Peer review (publication)
Title: Influence of magnetic fields on the coherence effects in the Na I D1 and D2 lines
Authors: Stenflo, J. O.
Gandorfer, A.
Wenzler, T.
Keller, C. U.
DOI: 10.21256/zhaw-4712
Published in: Astronomy & Astrophysics
Volume(Issue): 367
Issue: 3
Pages: 1033
Pages to: 1048
Issue Date: 2001
Publisher / Ed. Institution: EDP Sciences
ISSN: 0004-6361
Language: English
Subjects: Polarization; Sun; Scattering
Subject (DDC): 530: Physics
Abstract: To clarify the physical nature of the enigmatic scattering polarization in the Na I D1 and D2 line cores we have explored their behavior with full Stokes vector polarimetry in regions with varying degree of magnetic activity near the solar limb. These observations represent the first time that ZIMPOL II, the second generation of our CCD based imaging polarimeter systems, has been used for a scientific program. With ZIMPOL II the four Stokes images can be demodulated and recorded with a single CCD sensor such that the resulting images of the fractional polarization Q/I, U/I, and V/I are entirely free from spurious features due to seeing or flat-field effects. The polarization in the cores of the lines, in particular in D2, exhibits dramatic and unexpected spatial variations in both Q/I and U/I, including polarization self-reversals of the D2 Q/I core peak. As the fluctuations in the Q, U, and V parameters appear to be relatively uncorrelated, we have parametrized the profiles and made scatter plots of the extracted parameters. Comparison with synthetic scatter plots based on different theoretical models suggests that the polarization signals in the cores of the D2 and D1 lines have different physical origins: While the D1 core is likely to be governed by ground-state atomic polarization, the D2 core is dominated by the alignment of the excited state and by effects of partial frequency redistribution.
Further description: All A&A articles are in open access one year after their publication date (August 2013).
Fulltext version: Published version
License (according to publishing contract): Licence according to publishing contract
Departement: School of Engineering
Appears in collections:Publikationen School of Engineering

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