Solar jet-induced perturbation propagating through coronal loops and in-loop electron beam transport indicated by type II and type N radio bursts

TL;DR

This study investigates a high-frequency type II radio burst linked to a small solar jet and flare, revealing that jet-induced perturbations can generate shock waves within coronal loops, leading to electron acceleration and radio emissions.

Contribution

It demonstrates that jet-induced disturbances, not CMEs, can produce shock waves in coronal loops, explaining certain high-frequency type II bursts associated with weak solar activities.

Findings

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

Shock wave propagates through coronal loops at ~880 km/s.

Jet perturbation can generate shocks within low Alfvénic loops.

Abstract

Solar type II radio bursts are commonly attributed to coronal shocks driven by coronal mass ejections (CMEs). However, some metric type II bursts have occasionally been reported to occur in the absence of a CME and to be associated with weak solar activities. This study aims to identify the driver of the coronal shock in this kind of type II event. We investigate a high-frequency metric type II burst with clear band splitting, observed simultaneously by the Chashan Broadband Solar radio spectrograph and the Nan\c{c}ay Radioheliograph. It is associated with a C3.1-class flare and a small-scale jet, but without a detectable CME in the coronagraphs. The type II burst is preceded by multiple type III bursts, one of which exhibits characteristics of a type N burst. The type II burst source is associated with the jet-induced perturbation front propagating through nearby closed loops at a speed of $\sim$880 km s$^{-1}$, rather than the much slower jet front. This suggests that the disturbance initiated by the jet can convert to a shock wave within low Alfv\'enic coronal loops, providing the necessary conditions for electron acceleration and subsequent radio emission. Our findings offer new insights into the formation mechanism of high-frequency type II bursts associated with weak flares and jets.