Decimetric emission 500$''$ away from a flaring Site: Possible scenarios from ${\textit{GMRT}}$ solar radio observations

TL;DR

This study uses high-resolution GMRT radio observations to analyze a decimetric radio source located 500 arcseconds from a solar flare site, exploring possible scenarios for its origin and propagation.

Contribution

It presents the first high time cadence GMRT imaging of decimetric radio sources associated with solar flares, revealing a distant source likely due to wave ducting and common electron acceleration sites.

Findings

A strong radio source was observed 500'' away from the flare site during the C1.4 flare.

The distant source is likely generated by coherent emission and wave ducting effects.

Radio sources near the flare site correlate with type III bursts and CME activity.

Abstract

We present a study of decimetric radio activity, using the first high time cadence (0.5 s) images from the ${\textit{Giant Meterwave Radio Telescope}}$ (${\textit{GMRT}}$) at 610 MHz, associated with ${\textit{GOES}}$ C1.4 and M1.0 class solar flares, and a coronal mass ejection (CME) onset that occurred on 20 June 2015. The high spatial resolution images from ${\textit{GMRT}}$ show a strong radio source during the C1.4 flare, located ~500$''$ away from the flaring site with no corresponding bright footpoints or coronal features nearby. In contrast, however, strong radio sources are found near the flaring site during the M1.0 flare and around the CME onset time. Weak radio sources, located near the flaring site, are also found during the maximum of the C1.4 flare activity, which show a temporal association with metric type III bursts identified by the Solar Broadband Radio Spectrometer at Yunnan Astronomical Observatory. Based on a multi-wavelength analysis and magnetic potential field source surface extrapolations, we suggest that the source electrons of ${\textit{GMRT}}$ radio sources and metric type III bursts were originated from a common electron acceleration site. We also show that the strong ${\textit{GMRT}}$ radio source is generated by a coherent emission process and its apparent location far from the flaring site is possibly due to the wave-ducting effect.