Post-impulsive millimeter emission of the 2022-05-04 solar flare

Abstract

The present work aims at analyzing the nature of millimeter (mm) emission observed during the post-impulsive phase of the solar flare SOL2022-05-04T08:45 (M5.7), detected by the RT-7.5 radio telescope of the Bauman Moscow State Technical University at 93 GHz. We investigate the relationship of mm and extreme ultraviolet (EUV) emission with variations in the temperature and coronal plasma emission measure obtained from SDO/AIA and GOES data. The results show that the enhanced mm emission at the post-impulsive phase of the flare coincides with the increase of EUV emission, indicating a connection with moderately hot (~1 MK) plasma. Based on the calculation of the differential emission measure, we determine the parameters of the post-impulsive flare plasma and conclude that the optically thin coronal plasma may contribute of about 20% to the mm emission.