Active region filaments might harbor weak magnetic fields

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 either as 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 spectro-polarimetric observations of active region filaments. We propose a two-component model, one on top of the other. Both components have horizontal fields, the azimuth difference between them being close to 90 degrees. 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 that its combination along the line of sight reduces --and even can cancel out-- the Hanle signatures, giving rise to an apparent only-Zeeman profile. This model is also applicable to other chromospheric structures seen in absorption above active regions.

arXiv comment6 pages, 1 figure. Accepted by ApJ

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Cited by in corpus (6)

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• Determining the dynamics and magnetic fields in He I 10830 Å during a solar filament eruption
• Spectropolarimetric analysis of an active region filament. II. Evidence of the limitations of a single component model
• Magnetic Field of Solar Dark Filaments Obtained from He I 10830 Angstrom Spectro-polarimetric Observation
• Velocities of an Erupting Filament
• Spectral resolution effects on the information content in solar spectra