On the occurrence of type IV solar radio bursts in the solar cycle 24 and their association with coronal mass ejections

TL;DR

This study statistically analyzes 446 type IV solar radio bursts during solar cycle 24, revealing their strong association with CMEs and categorizing their spectral characteristics, providing new insights into their occurrence and relation to CME properties.

Contribution

First comprehensive statistical analysis of type IV radio bursts in solar cycle 24, detailing their association with CMEs and spectral classifications.

Findings

81% of type IV bursts are associated with CMEs

Only 2.2% of CMEs have associated type IV bursts

Moving type IV bursts are mostly linked to fast and wide CMEs

Abstract

Solar activity, in particular coronal mass ejections (CMEs), are often accompanied by bursts of radiation at metre wavelengths. Some of these bursts have a long duration and extend over a wide frequency band, namely, type IV radio bursts. However, the association of type IV bursts with coronal mass ejections is still not well understood. In this article, we perform the first statistical study of type IV solar radio bursts in the solar cycle 24. Our study includes a total of 446 type IV radio bursts that occurred during this cycle. Our results show that a clear majority, $\sim 81 \%$ of type IV bursts, were accompanied by CMEs, based on a temporal association with white-light CME observations. However, we found that only $\sim 2.2 \%$ of the CMEs are accompanied by type IV radio bursts. We categorised the type IV bursts as moving or stationary based on their spectral characteristics and found that only $\sim 18 \%$ of the total type IV bursts in this study were moving type IV bursts. Our study suggests that type IV bursts can occur with both `Fast' ($\geq 500$ km/s) and `Slow' ($< 500$ km/s), and also both `Wide' ($\geq 60^{\circ}$) and `Narrow' ($< 60^{\circ}$) CMEs. However, the moving type IV bursts in our study were mostly associated with `Fast' and `Wide' CMEs ($\sim 52 \%$), similar to type II radio bursts. Contrary to type II bursts, stationary type IV bursts have a more uniform association with all CME types.