出现在Ⅳμ爆发上的快变分量

The Rapidly Varying Components Superimposed on Type Ⅳμ Burst

概述了１９８８年１２月１６日出现在微波Ⅳ型大爆发上的快变分量观测特征，以及由ＭＨＤ调制磁流管的磁场强度，而产生了１２．５ｍｉｎ和１．２ｍｉｎ的长短准周期振荡。一部分高能电子被磁场俘获，做同步加速回旋辐射，产生了微波Ⅳ型爆发。另一部分高能电子以一定入射角喷注在磁拱上，形成螺距角各为异性的空心束分布，其电子回旋不稳定性导致ｓｐｉｋｅ辐射。最后，用慢波模式计算了三个频率上的１．２ｍｉｎ的准周期振荡，结果表明振荡周期随频率的增加而增大，与观测结果相符。

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.