Temporal Spectral Shift and Polarization of a Band-splitting Solar Type II Radio Burst

Abstract

In many type II solar radio bursts, the fundamental and/or the harmonic branches of the bursts can split into two almost parallel bands with similar spectral shapes and frequency drifts. However, the mechanisms accounting for this intriguing phenomenon remain elusive. In this study, we report a special band-splitting type II event in which spectral features appear systematically earlier on the upper band (with higher frequencies) than on the lower band (with lower frequencies) by several seconds. Furthermore, the emissions carried by the splitting band are moderately polarized with the left-hand polarized signals stronger than the right-hand ones. The polarization degree varies in a range of -0.3 to -0.6. These novel observational findings provide important constraints on the underlying physical mechanisms of band-splitting of type II radio bursts.