Characteristics of radio spikes as solar microflares at short decimetric wavelength

Abstract

A rare type of radio spike occurred on January 5, 1994 at short decimetric wavelength (1.42 GHz), and was observed with the Yunnan Observatory high time resolution (1 ms) radio telescope. The radio and optical characteristics of the spikes as radio microflares are presented. This event contains 53 radio millisecond spikes, and shows an intermittently periodic pulse train superimposed on the radio continuum background. Two newly emerging small sunspot groups with complex polarities were observed. The magnetic field strength of the source and the irradiated spike energies are estimated by using the radio observations. During a single spike, less than or equal to10(23) ergs may have been transferred to nonthermal electrons, and thus radio spikes may reflect microflare class activity. We discuss the generation mechanism of the radio microflares qualitatively. Our results favour the explosive coalescence model of the multiple magnetic flux loops, leading simultaneously to acceleration of electrons and heating.