The 17 January 2005 Complex Solar Radio Event Associated with Interacting Fast Coronal Mass Ejections

TL;DR

This study analyzes a complex solar radio event involving interacting coronal mass ejections, associated radio bursts, and energetic electron observations, providing insights into CME interactions and particle acceleration mechanisms.

Contribution

It presents detailed radio and particle observations of CME interactions and discusses the roles of shock acceleration and magnetic reconnection in electron energization.

Findings

Type-III bursts linked to CME interaction at 25 R☉

Successive electron releases observed by ACE

Low-frequency burst associated with CME interaction

Abstract

On 17 January 2005 two fast coronal mass ejections were recorded in close succession during two distinct episodes of a 3B/X3.8 flare. Both were accompanied by metre-to-kilometre type-III groups tracing energetic electrons that escape into the interplanetary space and by decametre-to-hectometre type- II bursts attributed to CME-driven shock waves. A peculiar type-III burst group was observed below 600 kHz 1.5 hours after the second type III group. It occurred without any simultaneous activity at higher frequencies, around the time when the two CMEs were expected to interact. We associate this emission with the interaction of the CMEs at heliocentric distances of about 25 R\odot. Near-relativistic electrons observed by the EPAM experiment onboard ACE near 1 AU revealed successive particle releases that can be associated with the two flare/CME events and the low-frequency type-III burst at the time of CME interaction. We compare the pros and cons of shock acceleration and acceleration in the course of magnetic reconnection for the escaping electron beams revealed by the type III bursts and for the electrons measured in situ.