The quasi-periodic fine structures in a solar radio burst at 3.2 cm wavelength on 23 May 1990

Abstract This paper describes the quasi-periodic fine structures (FS) in a solar radio burst which was observed with time resolution of 10ms at 3.2cm wavelength on 23 May 1990. The radio burst was associated with a M8.7/1B flare occurred in the active region AR 6063. The average period of these fine structures is about 1.5s and the amplitude modulation range from 2% to 5%. A preliminary analysis shows that there is a linear relation between the mean flux S of the radio burst and the repetition rate R of the quasiperiodic fine structures at 3.2cm wavelength. This relation is similar to that obtained by Kaufmann et al. in millimeter wavelength region. We suggest that these quasi-periodic fine structures probably reflect the modulated gyro-synchrotron emission due to MHD waves oscillating along magnetic field lines.