A Type II Radio Burst Driven by a Blowout Jet on the Sun

Abstract

Type II radio bursts are often associated with coronal shocks that are typically driven by coronal mass ejections (CMEs) from the Sun. Here we conduct a case study of a type II radio burst that is associated with a C4.5-class flare and a blowout jet, but without the presence of a CME. The blowout jet is observed near the solar disk center in the extreme-ultraviolet (EUV) passbands with different characteristic temperatures. Its evolution involves an initial phase and an ejection phase with a velocity of 560 ± 87 km s−1. Ahead of the jet front, an EUV wave propagates at a projected velocity of ∼403 ± 84 km s−1 in the initial stage. The velocity of the type II radio burst is estimated to be ∼641 km s−1, which corresponds to the shock velocity against the coronal density gradient. The EUV wave and the type II radio burst are closely related to the ejection of the blowout jet, suggesting that both are likely the manifestation of a coronal shock driven by the ejection of the blowout jet. The type II radio burst likely starts lower than those associated with CMEs. The combination of the velocities of the radio burst and the EUV wave yields a modified shock velocity at ∼757 km s−1. The Alfvén Mach number is in the range of 1.09–1.18, implying that the shock velocity is 10%–20% larger than the local Alfvén velocity.