Quick Event During the Decay Phase of the Microwave Emission of a Flare on May 22, 2021

• Published in: Geomagnetism and Aeronomy Vol. 63; no. 7; pp. 1062 - 1071
• Main Authors: Motyk, I. D., Kashapova, L. K., Setov, A. G., Shamsutdinova, Yu. N., Kupriyanova, E. G.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-12-2023; Springer Nature B.V
• Subjects: Decay; Domes; Earth and Environmental Science; Earth Sciences; Emission analysis; Emissions; Geophysics/Geodesy; Incoherent scatter radar; Magnetic fields; Microwave emission; Quasi-Periodic Oscillations; Radio bursts; Three dimensional analysis; Topology; radio bursts; flares; Sun; flare decay phase
• ISSN: 0016-7932; 1555-645X; 0016-7940
• DOI: 10.1134/S0016793223070174

This paper presents the results of a study of a short event that occurred during the decay phase of a C6.0 circular flare (GOES). The event was simultaneously observed by the Irkutsk Incoherent Scatter Radar at 161 MHz and by the Siberian Radioheliograph (SRH) at 5.6 GHz. The SRH data were obtained at a single frequency, but with a high time resolution (0.2 s). This made it possible to localize the microwave source and carry out its temporal profile using imaging photometry. The similarity of the time profiles at both frequencies and the close values of the periods of the quasi-periodic oscillations seen on both profiles indicate a close relationship between the emeission in the meter and microwave ranges. According to the images at 5.6 GHz, the burst source was located near the circular ribbon of the flare, but was not a part of it. The event was folowed by an eruption that manifested itself in the meter range as the Type II radio burst at frequencies above 200 MHz, while a burst at 161 MHz demonstrated the emission of the Type III radio burst. An analysis of the three-dimensional structure of the magnetic field, reconstructed on the basis of vector magnetograms, showed that the event source was located on relatively open field lines, which were above the dome structure of the circular flare. The active region topology near the microwave source of the event suggests the following scenario based on the expansion of the dome structure of the circular flare due to gas dynamic processes. This caused an impact on relatively open field lines, which resulted to eruption, acceleration of electrons, and their propagation along open field lines. It is shown that the event was triggered by a flare, despite the absence of a direct spatial connection between the burst and flare ribbons.