aat Acta Astrophys. Tau. Acta Astrophysica Taurica 2712-925X Kiselev Nikolai Nikolaevich, Mosсow, settlement Moskovskii, Tat'yanin Park Str., 12, Moscow, Russia. RU 77 Magnetism and activity of the Sun and stars – 2021 Conference proceedings Precursors of solar flares in the microwave range Abramov-Maximov Vladimir Bakunina Irina Central (Pulkovo) Astronomical Observatory of RAS, Pulkovskoye sh. 65/1, St. Petersburg 196140, Russia HSE University, Bolshaya Pecherskaya 25/12, Nizhny Novgorod 603155, Russia 23 06 2024 5 2 13 16 16 06 2024 Copyright (c) 2024 Vladimir Abramov-Maximov, Irina Bakunina 2024 Vladimir Abramov-Maximov, Irina Bakunina The metadata for this submission is licensed under a Creative Commons Attribution 4.0 International License. Copyright and publishing rights for texts published in Acta Astrophysica Taurica is retained by the authors, with first publication rights granted to the journal.Texts are free to use with proper attribution and link to the licensing (Creative Commons Attribution 4.0 International).

We present a study of the spatial distribution of quasiperiodic oscillations of microwave emission in two active regions before M-class flares. We have studied two events: NOAA 11283 on September 6 and NOAA 11302 on September 25, 2011. We used the Nobeyama Radioheliograph (NoRH) daily observations at a frequency of 17 GHz. In both cases we found the preflare wave trains of brightness temperature oscillations of microwave emission in active regions. The duration of wave trains is about 3–4 oscillation cycles. We found that the source of oscillations was a compact zone in the active region, which coincides with the area of maximum brightness during a flare.

Sun flares radio emission quasiperiodic oscillations The work was carried out within the framework of the state assignment No. 1021032422589-5. Abramov-Maximov V.E., Gelfreikh G.B., Shibasaki K., 2011. Solar Phys., vol. 273, pp. 403–412. Abramov-Maximov V.E., Bakunina I.A., 2018. Phys. At. Nuclei, vol. 81, no. 3, pp. 379–383. Abramov-Maximov V.E., Bakunina I.A., 2019. Geomagn. Aeron., vol. 59, no. 7, pp. 822–826. Abramov-Maximov V.E., Bakunina I.A., 2020. Geomagn. Aeron., vol. 60, no. 7, pp. 846–852. Avdyushin S.I., Bogomolov A.F., Borisova E.A., et al., 1985. Akademiia Nauk SSSR, Doklady, vol. 283, no. 1, pp. 67–70. (In Russ.) Aver’yanikhina E., Paupere M., Ozolins G., Elias M., 1982. Issled. Solntsa i Krasnykh Zvezd., no. 16, pp. 61–74. (In Russ.) Aleshin V.I., Kobrin M.M., Korshunov A.I., 1973. Radiophys. Quantum Electron., vol. 16, no. 5, pp. 571–576. Arbuzov S.I., 1979. Radiophys. Quantum Electron., vol. 22, no. 10, pp. 803–811. Berulis I.I., Molchanov A.P., Olyanyuk V.P., et al., 1973. Radiophys. Quantum Electron., vol. 16, no. 9, pp. 1047–1049. Berulis I.I., Kozlovskii A.L., Losovskii B.Y., et al., 1983. Sov. Astron., vol. 27, no. 5, p. 563. Bystrov M.V., Kobrin M.M., Snegirev S.D., 1978. Sov. Astron. Lett., vol. 4, pp. 76–77. Bystrov M.V., Kobrin M.M., Snegirev S.D., 1979. Geomagn. Aeron., vol. 19, pp. 197–199. Durasova M.S., Kobrin M.M., Yudin O.I., 1971. Nature, vol. 229, pp. 82–84. Gelfreikh G.B., Grechnev V.V., Kosugi T., Shibasaki K., 1999. Solar Phys., vol. 185, pp. 177–191. Gelfreikh G.B., Nagovitsyn Yu.A., Nagovitsyna E.Yu., 2006. Publ. Astron. Soc. Japan, vol. 58, pp. 29–35. Kobrin M.M., Pakhomov V.V., Durasova M.S., et al., 1973a. Radiophys. Quantum Electron., vol. 16, pp. 1036–1039. Kobrin M.M., Korshunov A.I., Snegirev S.D., Timofeev B.V., 1973b. Bull. Solnechnye Dannye, no. 10, p. 79–85. (In Russ.) Kobrin M.M., Semenova S.V., Pahomov V.V., Pahomova O.A., Fridman V.M., 1981. Astron. Tsirk., no. 1201, p. 1. Korshunov A.I., Prokof’eva N.A., 1976. Bull. Solnechnye Dannye, no. 2, pp. 52–56. (In Russ.) Sych R., Nakariakov V.M., Karlicky M., Anfinogentov S., 2009. Astron. Astrophys., vol. 505, pp. 791–799. Tan B., Yu Z., Huang J., Tan C., Zhang Y., 2016. Astrophys. J., vol. 833, id. 206.