Spectral variations within solar flare ribbons

Abstract

Solar flare ribbons are intense brightenings of principally chromospheric material that are responsible for a large fraction of the chromospheric emission in solar and stellar flares. We present an on-disc observation of flare ribbon substructures in an X9.3-class flare observed by the Swedish 1-m Solar Telescope. We identify categories of ribbon substructures seen in the Ca II 8542 Å, H$\alpha$, and Ca II K lines, focusing on their spatial locations and their (spectro-)polarimetric properties. Color Collapsed Plotting (COCOPLOT) software is used to assist in identifying areas of interest. We present five categories of spectral profiles within the general body of the flare ribbon: (1) Extremely broadened spectral line profiles, where the standard Fabry-Perot interferometer wavelength windows ($\approx 70$ km s${}^{-1}$) are insufficiently wide to allow for a complete analysis of the dynamics and atmospheric conditions. The mechanisms causing this degree of this broadening are not yet clearly understood. (2) Long-lived, dense kernels that manifest as more saturated chromospheric line profiles with lower signal in both Stokes parameters. They are interpreted as footpoints of bunched magnetic field loops, whose chromospheric lines form at greater heights than the nearby areas. (3) Doppler-shifted leading edges of the flare ribbon in regions that transiently display lower Stokes signals due to the emission dominating at greater heights in the atmosphere. (4) Condensed coronal rain overlapping the flare ribbons in the line of sight, producing exceptionally high Doppler shifts near the footpoints...

Published in A&A. 11 pages, 8 figures

References in corpus (43)

• The Interface Region Imaging Spectrograph (IRIS)
• An Observational Overview of Solar Flares
• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• Radiative Hydrodynamic Models of the Optical and Ultraviolet Emission from Solar Flares
• A Unified Computational Model for Solar and Stellar Flares
• CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter
• Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
• Non-equilibrium hydrogen ionization in 2D simulations of the solar atmosphere
• STiC -- A multi-atom non-LTE PRD inversion code for full-Stokes solar observations
• Flocculent flows in the chromospheric canopy of a sunspot
• MPI-AMRVAC 3.0: updates to an open-source simulation framework
• The height of a white-light flare and its hard X-ray sources
• The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares I: Modeling the Brightest NUV Footpoints in the X1 Solar Flare of 2014 March 29
• SSTRED: Data- and metadata-processing pipeline for CHROMIS and CRISP
• Hydrogen Balmer Line Broadening in Solar and Stellar Flares
• Si IV Resonance Line Emission During Solar Flares: Non-LTE, Non-equilibrium, Radiation Transfer Simulations
• Statistical Analysis of Stellar Flares from the First Three Years of TESS Observations
• Solar Chromospheric Temperature Diagnostics: a joint ALMA-H$\alpha$ analysis
• Formation of the thermal infrared continuum in solar flares
• A fully self-consistent model for solar flares
• Sun-as-a-star Analyses of Various Solar Active Events Using H$\alpha$ Spectral Images Taken by SMART/SDDI
• High-Cadence and High-Resolution Halpha Imaging Spectroscopy of a Circular Flare's Remote Ribbon with IBIS
• Modeling Mg II h, k and Triplet Lines at Solar Flare Ribbons
• The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope
• Stratification of physical parameters in a C-class solar flare using multi-line observations
• FIRTEZ-dz: A Forward and Inverse solver of the polarized Radiative Transfer Equation under Zeeman regime in geometrical scale
• GREGOR: Optics Redesign and Updates from 2018-2020
• He I 10830 Å Dimming During Solar Flares, I. The Crucial Role of Non-Thermal Collisional Ionisations
• Spectral Evidence for Heating at Large Column Mass in Umbral Solar Flare Kernels I: IRIS NUV Spectra of the X1 Solar Flare of 2014 Oct 25
• Solar Flare Arcade Modelling: Bridging the gap from 1D to 3D Simulations of Optically Thin Radiation
• A comparative study of two X2.2 and X9.3 solar flares observed with HARPS-N: Reconciling Sun-as-a-star spectroscopy and high-spatial resolution solar observations in the context of the solar-stellar connection
• Modelling Mg II During Solar Flares. I. Partial Frequency Redistribution, Opacity, and Coronal Irradiation
• Solar Flare Ribbon Fronts I: Constraining flare energy deposition with IRIS spectroscopy
• Measuring the Wilson depression of sunspots using the divergence-free condition of the magnetic field vector
• Non-LTE inversions of a confined X2.2 flare: I. Vector magnetic field in the photosphere and chromosphere
• Modeling Mg II during Solar Flares. II. Non-equilibrium Effects
• Flare Kernels May be Smaller than You Think: Modelling the Radiative Response of Chromospheric Plasma Adjacent to a Solar Flare
• A Study on Red Asymmetry of H-alpha Flare Ribbons Using Narrowband Filtergram in the 2001 April 10 Solar Flare
• Prospects of Detecting Non-thermal Protons in Solar Flares via Lyman Line Spectroscopy: Revisiting the Orrall-Zirker Effect
• Flare Induced Photospheric Velocity Diagnostics
• The Chromospheric Response to the Sunquake generated by the X9.3 Flare of NOAA 12673
• Spectral Characteristics and Formation Height of Off-Limb Flare Ribbons
• Physical properties of a fan-shaped jet backlit by an X9.3 flare

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