ACTIVE REGION FILAMENTS MIGHT HARBOR WEAK MAGNETIC FIELDS

• Published in: The Astrophysical journal Vol. 822; no. 1; p. 50
• Main Authors: Díaz Baso, C. J., Martínez González, M. J., Asensio Ramos, A.
• Format: Journal Article
• Language: English
• Published: United States The American Astronomical Society 01-05-2016
• Subjects: ABSORPTION; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; FILAMENTS; Line of sight; MAGNETIC FIELDS; ORIENTATION; POLARIMETRY; POLARIZATION; RADIANT HEAT TRANSFER; radiative transfer; SCATTERING; Signatures; SPACE DEPENDENCE; SPECTROSCOPY; SUN; Sun: chromosphere; Sun: filaments, prominences; Sun: magnetic fields; THICKNESS; Turbulence; ZEEMAN EFFECT
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/0004-637X/822/1/50

ABSTRACT Recent spectropolarimetric observations of active region filaments have revealed polarization profiles with signatures typical of the strong field Zeeman regime. The conspicuous absence in those observations of scattering polarization and Hanle effect signatures was then pointed out by some authors. This was interpreted as either a signature of mixed "turbulent" field components or as a result of optical thickness. In this article, we present a natural scenario to explain these Zeeman-only spectropolarimetric observations of active region (AR) filaments. We propose a two-component model, one on top of the other. Both components have horizontal fields, with the azimuth difference between them being close to 90°. The component that lies lower in the atmosphere is permeated by a strong field of the order of 600 G, while the upper component has much weaker fields, of the order of 10 G. The ensuing scattering polarization signatures of the individual components have opposite signs, so its combination along the line of sight reduces-and even can cancel out-the Hanle signatures, giving rise to an apparent Zeeman-only profile. This model is also applicable to other chromospheric structures seen in absorption above ARs.