A Model for Radio Emission from Solar Coronal Shocks

Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open problem. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiations from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock excites first Alfv\'en wave (AW) and then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by the ECM instability. Our results show that this model may have potential application to solar type II radio bursts.