On the occurrence of type IV solar radio bursts in the solar cycle 24 and their association with coronal mass ejections
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Solar activities, in particular coronal mass ejections (CMEs), are often accompanied by bursts of radiation at metre wavelengths, some of which are long duration and broadband in nature, such as type IV radio bursts. However, the association of type IV bursts with coronal mass ejections is still not well understood. 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, ∼81%of type IV bursts, were accompanied by CMEs, based on a temporal association with white-light CME observations. However, we found that only ∼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 ∼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’ (≥500km/s) and ‘Slow’ (<500km/s), and also both ‘Wide’ (≥60◦) and ‘Narrow’ (<60◦) CMEs. However, the moving type IV bursts in our study were mostly associated with ‘Fast’ and ‘Wide’ CMEs (∼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