On a Possible Scenario of Solar Coherent Bursts

Abstract

The first burst of solar microwave coherent emission observed simultaneously with two multifrequency two-dimensional radio telescopes is reported, making it possible to unambiguously interpret the mechanism of the radiation and to propose a scenario that explains all the observed features of the burst. Recently, many studies have appeared that explain coherent bursts of radio emission from the Earth’s magnetosphere and solar corona by an electron cyclotron maser (ECM) driven by horseshoe distribution. The result of this study is that the observed coherent burst near the frequency 4.8 GHz is caused by a hollow beam distribution formed by the oblique injection of electrons into a magnetic loop. If the pitch-angle is large enough, then the absence of HXR and the relatively large (about 1 s) pulse duration can be explained. The measured size of the ECM source, \(\approx 2.2^{\prime \prime }\), corresponds to a brightness temperature of \(\approx 5.8\times 10^{10}\text{ K}\). The displacement of the spike sources with respect to the gyroresonance source is consistent to the second-harmonic ECM emission, whereas the gyroresonance source is consistent to the third gyrolayer.