Solar narrowband decimetric spike bursts and associated phenomena

Abstract

Based on the observational data of solar narrowband decimetric spike bursts on 1981 Nov 12–14 (Enome et al. 1985) and, associated phenomena, we propose a model of two acceleration regions during the impulsive phase of solar flare. One (region A) is formed in the current sheet by magnetic reconnection process, the other (region B), at the top of the flaring loop by turbulence acceleration. Region B is able to generate mildly relativistic electrons and to emit gyrosynchrotron radiation or decimeter waveband microwave bursts. Two accelerated electron streams escape from region A simultaneously. One travels through the outer corona and excites type III bursts, the other, injected into the emerging flaring-loop at a certain pitch angle, will stimulate electron-cyclotron maser with a “hollow beam” distribution and emit narrowband decimetric spike bursts. Utilizing the formulae of “hollon beam” electron cyclotron maser, we have evaluated the maximum growth rate of the 2nd harmonic wave of FX mode and reached the following conclusions. As the energy of the downward electron stream increases, the maximum growth rate, probability of spike emissions, relative bandwidth and brightlness temperature all increase, the linear size of the spike source decreases, and the peak flux remains fixed. In addition, we have clarified the close association between narrow band spike bursts and type III bursts, and hard X-ray bursts.