Preflare Fluctuations of Radio Emission from Active Regions of the Sun According to Observations at RSTN

For the first time, several flare events are analyzed based on multifrequency observations using the Radio Solar Telescope Network. The purpose of the analysis is to identify signs of flare preparation. In all considered cases, preflare quasi-periodic fluctuations (QPFs) of radio emission were detected. The duration of preflare wavetrains is 6–20 min. Wavetrains consist of 3–5 pulses. QPFs at lower frequencies (200–600 MHz) begin later than those at high frequencies by 2–6 min. QPFs at frequencies of 2695–8800 MHz occur almost synchronously. The highest amplitude of QPFs is observed at a frequency of 4995 MHz. The observed QPFs can be explained by the force-free magnetic rope model (Solov’ev and Kirichek, 2023).