The Rapidly Varying Components Superimposed on Type Ⅳμ Burst

The observational characteristics of the rapidly varying components superimposed on type Ⅳa microwave Burst on December 16, 1988 are summarized. A long period oscillation of 12.5 minutes and a short period oscillation of 1.2 miuntes both were observed. The two oscillations resulted from that the magnetic intensities in the magnetic flux bottle were modulated by the MHD. The Type Ⅳμ Burst were generated from the gyrosynchrotron emission of one part of high energy electrons trapped by the magnetic field. Others radiated to the magnetic loop structures with some angles, the loss cone distribution with the different pitch angles was formed. The spikes were generated by the instability of the ECM. Finally,the short period oscillations of 1.2 minutes at three frequencies are calculated by the slow wave mode. The result indicates that the oscillation period increases with the frequency, which is consistent with the observational result.