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Колебания в активных областях Солнца перед вспышками
Results: The first M-class flare occurred on September 4, 2017 at 05:36-06:05 UT. We found that 100-minute oscillations were observed on September 4 during a few hours before M1.2 flare. At the same time, there were no noticeable oscillations on September 3. The observed effect is similar to the previously detected effect for 3-minute and 10-minute oscillations, namely, before radio burst there was increase of the power of oscillations. The effect can be interpreted as a relationship between MHD waves propagating along the magnetic flux tube of sunspot and beginning of the flares.
Methods: We used the Nobeyama Radioheliograph (NoRH) daily observations. The radio maps of the whole solar disk were synthesized in non-standard mode with a cadence of ten seconds and ten seconds averaging. We computed the time series of maximum brightness temperature and total flux over selected field-of-view (FOV) and used spectral wavelet analysis of the time series.
Context: We continue research the oscillation parameters in solar active regions (ARs) in connection with their flare activity.
Aims: The aim of this paper is to study oscillations of microwave emission of AR NOAA 12673 before first M-class flare in September 2017.