Spectropolarimetric investigation of the photosphere during a solar microflare

Abstract

The results of the study of the thermodynamical parameters and the magnetic field in the solar photosphere during the solar microflare on 2009 July 4 in the active region NOAA 11024 are presented. The analysis is based on the observations with the French-Italian telescope THEMIS (Heliographic Telescope for the Study of the Magnetism and Instabilities on the Sun), operated on the island of Tenerife in the Spanish Observatorio del Teide of the Instituto de Astrofisica de Canarias in the multiline spectropolarimetric mode. The high-resolution Stokes I, Q, U and V profiles of 10 photospheric lines are used for the modelling. Semi-empirical models are derived from the inversion with Stokes Inversion based on Response functions code, developed by Ruiz Cobo and del Toro Iniesta. The models include two components: a thin magnetic flux tube and its non-magnetic surroundings. The temporal variations in all photospheric parameters are revealed during the microflare. The magnetic field strength increased from 800 to 1200 G during the onset phase of the microflare. The inferred flux tube models show the temperature enhancement in the photospheric layers relative to the quiet-Sun model atmosphere at the onset of the flare. The temperature inhomogeneities are found in the inferred atmosphere at the end of the microflare.