A formation mechanism for the type II radio emission in the solar corona unrelated to shock waves

TL;DR

This paper investigates the origin of certain type II radio bursts in the solar corona, proposing a mechanism unrelated to shock waves, specifically involving drift current instability in CME structures.

Contribution

It introduces a novel formation mechanism for type II radio emissions in the corona that does not rely on shock wave phenomena.

Findings

Type II radio bursts can occur without shock waves in the presence of CMEs.

Drift current instability in CME frontal structures may generate these radio bursts.

Analysis of observational data supports the proposed mechanism.

Abstract

Mark 4, COR1/STEREO and LASCO/SOHO data analysis shows that at least a portion of type II radio bursts observed in the corona occurs in the presence of a CME, but in the absence of a shock ahead of them. A drift current instability in the CME frontal structure is discussed as a possible cause of such bursts.