Mg II Lines Observed during the X-class Flare on 29 March 2014 by the Interface Region Imaging Spectrograph

Abstract

Mg II lines represent one of the strongest emissions from the chromospheric plasma during solar flares. In this article, we studied the Mg II lines observed during the X1 flare on March 29 2014 (SOL2014-03-29T17:48) by IRIS. IRIS detected large intensity enhancements of the Mg II h and k lines, subordinate triplet lines, and several other metallic lines at the flare footpoints during this flare. We have used the advantage of the slit-scanning mode (rastering) of IRIS and performed, for the first time, a detailed analysis of spatial and temporal variations of the spectra. Moreover, we were also able to identify positions of strongest HXR emissions using RHESSI observations and to correlate them with the spatial and temporal evolution of Mg II spectra. The light curves of the Mg II lines increase and peak contemporarily with the HXR emissions but decay more gradually. There are large red asymmetries in the Mg II h and k lines after the flare peak. We see two spatially well separated groups of Mg II line profiles, non-reversed and reversed. In some cases, the Mg II footpoints with reversed profiles are correlated with HXR sources. We show the spatial and temporal behavior of several other line parameters (line metrics) and briefly discuss them. Finally, we have synthesized the Mg II k line using our non-LTE code with the MALI technique. Two kinds of models are considered, the flare model F2 of Machado et al. (1980) and the models of Ricchiazzi and Canfield (1983). Model F2 reproduces the peak intensity of the unreversed Mg II k profile at flare maximum but does not account for high wing intensities. On the other hand, the RC models show the sensitivity of Mg II line intensities to various electron-beam parameters. Our simulations also show that the microturbulence produces a broader line core, while the intense line wings are caused by an enhanced line source function.

25 pages, 18 figures, accepted for publication in Solar Physics

References in corpus (5)

• The 2014 March 29 X-flare: sub-arcsecond resolution observations of Fe XXI 1354.1
• Hydrogen Balmer Continuum in Solar Flares Detected by the Interface Region Imaging Spectrograph (IRIS)
• IRIS Observations of the Mg II h & k Lines During a Solar Flare
• The fast filament eruption leading to the X-flare on March 29, 2014
• A simple model of chromospheric evaporation and condensation driven conductively in a solar flare

Cited by in corpus (22)

• 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
• 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
• 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
• Modeling Mg II h, k and Triplet Lines at Solar Flare Ribbons
• Non-Gaussian Velocity Distributions in Solar Flares from Extreme Ultraviolet Lines: A Possible Diagnostic of Ion Acceleration
• Observations and Modelling of the Pre-Flare Period of the 29 March 2014 X1 Flare
• An explanation of remarkable emission line profiles in post-flare coronal rain
• 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
• Multi thermal atmosphere of a mini solar flare during magnetic reconnection observed with IRIS
• Modeling Mg II during Solar Flares. II. Non-equilibrium Effects
• IRIS Mg II Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole
• The Triggering of the 29-March-2014 Filament Eruption
• Exploring mutual information between IRIS spectral lines. II. Calculating the most probable response in all spectral windows
• Undercover EUV Solar Jets Observed by the Interface Region Imaging Spectrograph
• Flare heating of the chromosphere: Observations of flare continuum from GREGOR and IRIS
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• The diversity of spectral shapes of hydrogen Lyman lines and Mg II lines in a quiescent prominence