Modeling Mg II h, k and Triplet Lines at Solar Flare Ribbons

Abstract

Observations from the \textit{Interface Region Imaging Spectrograph} (\textsl{IRIS}) often reveal significantly broadened and non-reversed profiles of the Mg II h, k and triplet lines at flare ribbons. To understand the formation of these optically thick Mg II lines, we perform plane parallel radiative hydrodynamics modeling with the RADYN code, and then recalculate the Mg II line profiles from RADYN atmosphere snapshots using the radiative transfer code RH. We find that the current RH code significantly underestimates the Mg II h \& k Stark widths. By implementing semi-classical perturbation approximation results of quadratic Stark broadening from the STARK-B database in the RH code, the Stark broadenings are found to be one order of magnitude larger than those calculated from the current RH code. However, the improved Stark widths are still too small, and another factor of 30 has to be multiplied to reproduce the significantly broadened lines and adjacent continuum seen in observations. Non-thermal electrons, magnetic fields, three-dimensional effects or electron density effect may account for this factor. Without modifying the RADYN atmosphere, we have also reproduced non-reversed Mg II h \& k profiles, which appear when the electron beam energy flux is decreasing. These profiles are formed at an electron density of $\sim 8\times 10^{14}{\mathrm{cm}}^{-3}$ and a temperature of $\sim 1.4\times 10^4$ K, where the source function slightly deviates from the Planck function. Our investigation also demonstrates that at flare ribbons the triplet lines are formed in the upper chromosphere, close to the formation heights of the h \& k lines.

References in corpus (33)

• The Interface Region Imaging Spectrograph (IRIS)
• Impulsive phase flare energy transport by large-scale Alfven waves and the electron acceleration problem
• Radiative Hydrodynamic Models of the Optical and Ultraviolet Emission from Solar Flares
• A Unified Computational Model for Solar and Stellar Flares
• The formation of IRIS diagnostics II. The formation of the Mg II h&k lines in the solar atmosphere
• The formation of IRIS diagnostics I. A quintessential model atom of Mg II and general formation properties of the Mg II h&k lines
• Temporal evolution of multiple evaporating ribbon sources in a solar flare
• Temporal evolution of chromospheric evaporation: case studies of the M1.1 flare on 2014 September 6 and X1.6 flare on 2014 September 10
• RH 1.5D: a massively parallel code for multi-level radiative transfer with partial frequency redistribution and Zeeman polarisation
• The Formation of IRIS diagnostics. IV. The Mg II triplet lines as a new diagnostic for lower chromospheric heating
• Non-LTE inversions of the Mg II h&k and UV triplet lines
• Continuum Enhancements in the Ultraviolet, the Visible and the Infrared during the X1 flare on 2014 March 29
• 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
• New Insights into White-Light Flare Emission from Radiative-Hydrodynamic Modeling of a Chromospheric Condensation
• Simulations of the Mg II k and Ca II 8542 lines from an Alfvén Wave-heated flare chromosphere
• Data-driven Radiative Hydrodynamic Modeling of the 2014 March 29 X1.0 Solar Flare
• Identifying typical Mg II flare spectra using machine learning
• Hydrogen Balmer Line Broadening in Solar and Stellar Flares
• What do iris observations of Mg II k tell us about the solar plage chromosphere?
• Fast approximation of angle-dependent partial redistribution in moving atmospheres
• Chromospheric Evaporation in an X1.0 Flare on 2014 March 29 Observed with IRIS and EIS
• Si IV Resonance Line Emission During Solar Flares: Non-LTE, Non-equilibrium, Radiation Transfer Simulations
• IRIS Observations of the Mg II h & k Lines During a Solar Flare
• The magnetic sensitivity of the Mg ii k line to the joint action of Hanle, Zeeman and magneto-optical effects
• Blue wing enhancement of the chromospheric Mg II h and k lines in a solar flare
• Multi-episode chromospheric evaporation observed in a solar flare
• A parameter study for modeling MgII h and k emission during solar flares
• Near-Ultraviolet Spectra of Flares on YZ CMi
• Parameterizations of Chromospheric Condensations in dG and dMe Model Flare Atmospheres
• Combined Modeling of Acceleration, Transport, and Hydrodynamic Response in Solar Flares. II. Inclusion of Radiative Transfer with RADYN
• Mg II Lines Observed during the X-class Flare on 29 March 2014 by the Interface Region Imaging Spectrograph
• UV and EUV Emissions at the Flare Foot-points Observed by AIA
• White-Light Continuum in Stellar Flares

Cited by in corpus (18)

• Spectral signatures of chromospheric condensation in a major solar flare
• Detection of Flare-induced Plasma Flows in the Corona of EV Lac with X-ray Spectroscopy
• Possible detection of coronal mass ejections on late-type main-sequence stars in LAMOST medium-resolution spectra
• APO & SMARTS flare star campaign observations I. Blue wing asymmetries in chromospheric lines during mid M dwarf flares from simultaneous spectroscopic and photometric observation data
• Real-time flare prediction based on distinctions between flaring and non-flaring active region spectra
• 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
• He I 10830 Å Dimming During Solar Flares, I. The Crucial Role of Non-Thermal Collisional Ionisations
• Constraints on Stellar Flare Energy Ratios in the NUV and Optical From a Multiwavelength Study of GALEX and Kepler Flare Stars
• Solar Flare Arcade Modelling: Bridging the gap from 1D to 3D Simulations of Optically Thin Radiation
• 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
• Modeling Mg II during Solar Flares. II. Non-equilibrium Effects
• Spectral variations within solar flare ribbons
• Exploring mutual information between IRIS spectral lines. II. Calculating the most probable response in all spectral windows
• Using Multiple Instance Learning for Explainable Solar Flare Prediction
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Specialist Discussion Meeting: 3D structure of the flare chromosphere
• Revisiting the Spectral Features of Ellerman Bombs and UV Bursts. I. Radiative Hydrodynamic Simulations