Magnetic Loop Oscillation Associated with a Large Type-Ⅳμ Burst and Millisecond Spike Emission

A rare large Ty pe-Ⅳμburst, appeared above active region NOAA/ USAF 5278 was observed at Yunnan Observatory with Phoenix Ⅱ Microwave Spectrometer at three frequencies (4.00, 2.84 and 1.42 GHz)on December 16, 1988.The burst consisted of 5 main peaks with a quasiperiod of 12.5 min, on which many complex millisecond spike emissions were superimposed. Within the first main peak there were 8 secondary peaks with a quasi-period of 98s (at 4.00 GHz), 72s (2.84 GHz)and 60s (1.42 GHz).A semi-quanti tative explanation is given for the variation of the quasi-period with frequency in terms of MHD modulated oscillations in the magnetic flux tube.