Radio bursts observed during solar eruptive flares and their schematic summary

TL;DR

This review summarizes over twenty years of solar eruptive flare radio observations, highlighting various radio burst types and their significance in understanding plasma processes, supported by models and multi-wavelength data.

Contribution

The paper provides a comprehensive synthesis of radio burst observations during solar flares, introducing a new scheme of bursts and emphasizing the importance of positional data.

Findings

Drifting pulsation structures as plasmoid signatures

Unusual zebra pattern in early flare stage

Radio bursts indicating plasmoid merging

Abstract

In this review we summarize results of our analysis of the observations of solar eruptive flares made by the Ond\v{r}ejov radiospectrograph for more than twenty years. We also present some Potsdam-Tremsdorf radio spectra from our common studies. Considering a 3-dimensional model of eruptive flares together with the results of our magnetohydrodynamic and particle-in-cell simulations we show an importance of decimetric radio bursts for understanding of plasma processes in eruptive flares. We present drifting pulsation structures as signatures of plasmoids, an unusual zebra pattern in the very early flare stage, narrowband dm-spikes as the bursts generated in the reconnection plasma outflows, radio bursts indicating a merging of plasmoids, pair of decimetric type III bursts indicating the electron beams propagating upwards and downwards in the solar atmosphere from the acceleration site, and a special decimetric type III burst formed probably around the plasmoid. We present unusual radio bursts connected with the rising magnetic rope at the very beginning of eruptive flares. Furthermore, based on the analysis of decimetric continua we estimated the level of the plasma turbulence in a vicinity of the flare termination shock. Interpretations of all these bursts are based on models and time coincidences with observations in X-ray, UV and optical ranges; in most cases an information about positions of these radio sources is missing. To show an importance of positional information, we present a rare example of observations, where the drifting pulsation structure was observed simultaneously with the observations made by the EOVSA radiointerferometer. All the presented bursts are then summarized in a new scheme of bursts and compared with the schema commonly used.