Characterizing the Spectral Structure of Weak Impulsive Narrowband Quiet Sun Emissions

TL;DR

This paper investigates the spectral properties of Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs), revealing their narrow bandwidths, compact morphologies, and potential link to nanoflares and coronal heating.

Contribution

It provides the first estimation of WINQSEs' bandwidths and compares their spectral nature to solar radio spikes, advancing understanding of their origins and characteristics.

Findings

WINQSEs have bandwidths less than 700 kHz.

They exhibit flux densities of 20-50 Jy.

Spectral similarities to solar radio spikes suggest a connection to nanoflares.

Abstract

Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs) are a newly discovered class of radio emission from the solar corona. These emissions are characterized by their extremely impulsive, narrowband and ubiquitous nature. We have systematically been working on their detailed characterization, including their strengths, morphologies, temporal characteristics, energies, etc. This work is the next step in this series and focuses on the spectral nature of WINQSEs. Given that their strength is only a few percent of the background solar emission, we have adopted an extremely conservative approach to reliably identify WINQSES. Only a handful of WINQSEs meet all of our stringent criteria. Their flux densities lie in the 20 $-$ 50 Jy range and they have compact morphologies. For the first time, we estimate their bandwidths and find them to be less than 700 kHz, consistent with expectations based on earlier observations. Interestingly, we also find similarities between the spectral nature of WINQSEs and the solar radio spikes. This is consistent with our hypothesis that the WINQSEs are the weaker cousins of the type-III radio bursts and are likely to be the low-frequency radio counterparts of the nanoflares, originally hypothesized as a possible explanation for coronal heating.