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

TL;DR

This study presents a case where a type II radio burst is driven by a blowout jet on the Sun, showing shock formation without the presence of a coronal mass ejection, and providing insights into shock dynamics and jet-associated phenomena.

Contribution

It demonstrates that blowout jets can drive coronal shocks leading to type II radio bursts, expanding understanding beyond CME-driven shocks.

Findings

Type II radio burst associated with a blowout jet, not a CME.

Shock velocity estimated at 641 km/s, with a modified shock velocity of 757 km/s.

The shock Mach number indicates a super-Alfvénic shock with 10%-20% higher velocity than local Alfvén speed.

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 km/s. Ahead of the jet front, an EUV wave propagates at a projected velocity of 403 km/s in the initial stage. The moving velocity of the source region of the type II radio burst is estimated to be 641 km/s, 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. The Alfven Mach number is in the range of 1.09-1.18, implying that the shock velocity is 10%-20% larger than the local Alfven velocity.