Fine Structure of Metric Type-IV Radio Bursts Observed with the ARTEMIS-IV Radio Spectrograph: Association with Flares and Coronal Mass Ejections

TL;DR

This study analyzes fine structures within type-IV solar radio bursts to understand their association with solar flares and CMEs, revealing strong temporal correlations and classifying various fine structures observed with high cadence radio spectrograph data.

Contribution

It provides a detailed classification of fine structures in type-IV bursts and establishes their temporal relationship with flare and CME energy release episodes.

Findings

Strong temporal association between fine structures and energy release events.

Featureless broadband continuum persists throughout flare--CME events.

Fibers and other fine structures follow the initial energy release with wider distribution.

Abstract

Fine structures embedded in type-IV burst continua may be used as diagnostics of the magnetic field restructuring and the corresponding energy release associated with the low corona development of flare/CME events. A catalog of 36 type-IV bursts observed with the SAO receiver of the ARTEMIS-IV solar radio-spectrograph in the 450--270 MHz range at high cadence (0.01 sec) was compiled; the fine structures were classified into five basic classes with two or more sub-classes each. The time of fine structure emission was compared with the injection of energetic electrons as evidenced by HXR and microwave emission, the SXR light-curves and the CME onset time. Our results indicate a very good temporal association between energy release episodes and pulsations, spikes, narrow-band bursts of the type-III family and zebra bursts. Of the remaining categories, the featureless broadband continuum starts near the time of the first energy release, between the CME onset and the SXR peak, but extends for several tens of minutes after that, covering almost the full extent of the flare--CME event. The intermediate drift bursts, fibers in their majority, mostly follow the first energy release but have a wider distribution, compared to other fine structures.