Analysing the evolution of the thermal and magnetic properties of an X-class flare in the low solar atmosphere

Abstract

We analysed the evolution of the spatial distribution and stratification of the physical parameters of the atmosphere of an X-class flare in the photosphere and chromosphere. We analysed the full Stokes vector of the Fe I 617.3 nm and Ca II 854.2 nm transitions recorded by the Interferometric Bidimensional Spectropolarimeter instrument on the 22 October 2014. We used the DeSIRe code to infer the atmospheric parameters at photospheric and chromospheric layers over the observed field of view and the entire time series spanning more than one hour. Our findings reveal that at the beginning of the observing run right after the flare peak, the chromosphere is characterised by temperature enhancements and strong upflows in the flare ribbon area, indicating that the flaring event produces hot material moving outwards from the Sun. The temperature enhancements and strong upflows decrease in amplitude and area occupied for subsequent snapshots, signalling that the flare activity is slowly and continuously fading. Concerning the magnetic field vector, we observe the presence of large-scale mixed polarities in the regions where the flare ribbon was located which do not change abruptly with time, in contrast with the high-temperature areas. Thus, it seems that the time series covered here reveals that the post-flare activity diminishes with time with no re-appearance of heating sources or any other thermal or magnetic activity; that is, the presence and traces of flaring activity fade away without significant restructuring of the low atmosphere in this confined flare event.