Continuum enhancements, line profiles and magnetic field evolution during consecutive flares

TL;DR

This study analyzes magnetic field changes, continuum enhancements, and line profile variations during two consecutive solar flares, revealing insights into flare triggering mechanisms and magnetic restructuring in active regions.

Contribution

It provides detailed multi-instrument observations of continuum and spectral changes during consecutive flares, highlighting the role of sunspot evolution and magnetic field reconfiguration.

Findings

Continuum enhancements observed in ROSA images and IRIS spectra.

Blue-shifted spectral component at eruption onset.

Magnetic and penumbral changes linked to flare activity.

Abstract

During solar flares, magnetic energy can be converted into electromagnetic radiation from radio waves to $\gamma$ rays. Enhancements in the continuum at visible wavelengths give rise to white-light flares, as well as continuum enhancements in the FUV and NUV passbands. 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 (IRIS, SDO/HMI, Hinode/SOT) and ground-based telescopes (ROSA/DST) during two consecutive C7.0 and X1.6 flares 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 \textit{IRIS} spectra. In the latter, a prominent blue-shifted component is observed at the onset of the eruption. We investigate the role played by the evolution of the $\delta$ 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.