Microwave fluctuations associated with the October 19, 1989 solar flare

Abstract

Solar microwave fluctuations on 15.0 GHz, 9.5 GHz and 6.7 GHz observed at Cuba station were studied from three days before to one day after the 4B/Xl3 solar flare of October 19, 1989. Periodograms show a displacement of the main period from 60 to 80 min and an increase in amplitude of the 20 min period as compared to the periodogram for October 4, 1989. Time evolution for each frecuency shows greater stability in the 6.7 GHz signal and on the days closer to the flare. Fluctuations are attributed to a downward flux of heated plasma which excites eigenmode oscillations of vertical magnetic tubes anchored to the photosphere in the active region where the flare occurred.