Fitting peculiar spectral profiles in He I 10830 Å absorption features

Abstract

The new generation of solar instruments provides better spectral, spatial, and temporal resolution for a better understanding of the physical processes that take place on the Sun. Multiple-component profiles are more commonly observed with these instruments. Particularly, the He I 10830 Å triplet presents such peculiar spectral profiles, which give information on the velocity and magnetic fine structure of the upper chromosphere. The purpose of this investigation is to describe a technique to efficiently fit the two blended components of the He I 10830 Å triplet, which are commonly observed when two atmospheric components are located within the same resolution element. The observations used in this study were taken on 2015 April 17 with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-meter GREGOR solar telescope, located at the Observatorio del Teide, Tenerife, Spain. We apply a double-Lorentzian fitting technique using Levenberg-Marquardt least-squares minimization. This technique is very simple and much faster than inversion codes. Line-of-sight Doppler velocities can be inferred for a whole map of pixels within just a few minutes. Our results show sub- and supersonic downflow velocities of up to 32 km/s for the fast component in the vicinity of footpoints of filamentary structures. The slow component presents velocities close to rest.

arXiv comment7 pages, 5 color figures, accepted for publication in Astron. Nachr. as a part of special edition of the 12th Potsdam Thinkshop

References in corpus (5)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• Advanced Forward Modeling and Inversion of Stokes Profiles Resulting from the Joint Action of the Hanle and Zeeman Effects
• Center-to-Limb Variation of Solar Line Profiles as a Test of NLTE Line Formation Calculations
• Multicomponent He I 10830 Å profiles in an active filament
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Cited by in corpus (8)

• Temporal evolution of arch filaments as seen in He I 10830 Å
• Determining the dynamics and magnetic fields in He I 10830 Å during a solar filament eruption
• High-resolution imaging and near-infrared spectroscopy of penumbral decay
• Ca II 8542 Å brightenings induced by a solar microflare
• Magnetized supersonic downflows in the chromosphere. A statistical study using the He I 10830 Å lines
• Tracking downflows from the chromosphere to the photosphere in a solar arch filament system
• Spectral Characteristics of the He I D3 Line in a Quiescent Prominence Observed by THEMIS
• The dependence of the magnetism of a near-limb sunspot on height