Expansion and Compression of a Flare Loop System during the Flare on January 15, 2022 According to Ultraviolet and Microwave Data

Abstract In this paper, we study the dynamics of a single loop structure in a C1.3 flare on January 15, 2022. A new type of behavior of flare loop was discovered. Unlike the previously known cases of visible contraction and expansion of flare loops in the phases of rise and decay of the flare radiation flux, respectively, the flare on January 15, 2022 exhibited a directly opposite process: the loop increases in its height during the flare intensity rise phase and contracts during the decay phase. Characteristic changes in the height, duration, and rate of the expansion and contraction of the loop structure were established. An increase of the electric current in the loop during the rise phase and its decrease during the contraction phase are proposed as an explanation of this behavior.