Observational Evidence for Solar Radio Microflares with Unusual Characteristics

A very rare type of solar radio microflares occurred during 0645～0720 UT on Jan. 5, 1994 is introduced in this paper. The radio and optical characteristics of the solar microflares of a short decimetric wave (1 42 GHz) are discussed. This event contains 53 radio fast fine structures (FFS), that is, 53 intermittently periodic impulse trains with similar morphologies superimposed on the continuum radiation background. The intensities of the pulses lie within 150～200 s. f. u. and the durations (half power width) are of the order of 10～50 milliseconds (ms). 18 out of 53 FFSs are doublepeak-separating structures. In this paper we try to discuss the generation mechanism qualitatively and find it is in consistence with the model of current loop explosive coalescence (Sakai and De Jager, 1989a, 1989b): the explosive coalescence of the multiple of cross magnetic flux loops causes the plasma disturbance and so rapidly transform the magnetic energy into the kinetic energy of electrons.