Continuum Enhancements, Line Profiles, and Magnetic Field Evolution during Consecutive Flares

Francesca Zuccarello,Mihalis Mathioudakis,Mariarita Murabito,Mariachiara Falco,Vincenzo Capparelli,Serena Criscuoli,Salvo L Guglielmino,Peter H Keys

doi:10.3847/1538-4357/ab621f

Abstract

Abstract During solar flares, magnetic energy can be converted into electromagnetic radiation from radio waves to γ-rays. Enhancements in the continuum at visible wavelengths, as well as continuum enhancements in the FUV and NUV passbands, give rise to white-light flares. In addition, the strong energy release in these events can lead to the rearrangement of the magnetic field at the photospheric level, causing morphological changes in large and stable magnetic structures like sunspots. In this context, we describe observations acquired by satellite instruments (Interface Region Imaging Spectrograph (IRIS), Solar Dynamics Observatory/Helioseismic and Magnetic Imager, Hinode/Solar Optical Telescope) and ground-based telescopes (Rapid Oscillations in the Solar Atmosphere (ROSA)/Dunn Solar Telescope) during two consecutive C7.0 and X1.6 flares that occurred in active region NOAA 12205 on 2014 November 7. The flare was accompanied by an eruption. The results of the analysis show the presence of continuum enhancements during the evolution of the events, observed both in ROSA images and in IRIS spectra. In the latter, a prominent blueshifted component is observed at the onset of the eruption. We investigate the role played by the evolution of the δ sunspots of the active region in the flare triggering, and finally we discuss the changes in the penumbrae surrounding these sunspots as a further consequence of these flares.

Highlights

Solar flares are complex eruptive phenomena occurring in the atmospheric layers of the Sun, releasing energy spanning typically from 1028 to 1032 erg
That at the same time, process of chromospheric evaporation and condensation are taking place. In this scenario, for selected time intervals and slit positions at the flare ribbon, the line profiles of C II 1335.75 Å, Si IV 1402.8 Å, and Mg II k&h may suggest the occurrence of a process of chromospheric evaporation followed by condensation taking place at different atmospheric heights, given different formation temperatures of the lines
We studied two consecutive C7.0 and X1.6 flares occurred in active regions (ARs) 12205 using data acquired by ground-based and satellite instruments

Summary

Introduction

Solar flares are complex eruptive phenomena occurring in the atmospheric layers of the Sun, releasing energy spanning typically from 1028 to 1032 erg. Solar flares are complex eruptive phenomena occurring in the atmospheric layers of the Sun, releasing energy spanning typically from 1028 to 1032 erg They are often triggered by the destabilization of a filament located above a polarity inversion line (PIL; see, e.g., Fletcher et al 2011 for a review and references therein). This energy, previously stored in a nonpotential magnetic field configuration, is converted, through magnetic reconnection, in kinetic energy, bulk plasma motions, and electromagnetic radiation emitted through the whole spectrum, from decameter radio waves to gamma-rays at 100 MeV (see, e.g., Benz 2017).

Objectives

Findings

Discussion

Conclusion