Radio‐Quiet Fast and Wide Coronal Mass Ejections

We report on the properties of radio-quiet (RQ) and radio-loud (RL) coronal mass ejections (CMEs) that are fast and wide (FW). RQ CMEs lack type II radio bursts in the metric and decameter-hectometric (DH) wavelengths. RL CMEs are associated with metric or DH type II bursts. We found that ~40% of the FW CMEs from 1996 to 2005 were RQ. The RQ CMEs had an average speed of 1117 km s −1 compared to 1438 km s −1 for the RL, bracketing the average speed of all FW CMEs (1303 km s −1 ). The fraction of full halo CMEs (apparent width = 360°) was the largest for the RL CMEs (60%), smallest for the RQ CMEs (16%), and intermediate for all FW CMEs (42%). The median soft X-ray flare size for the RQ CMEs (C6.9) was also smaller than that for the RL CMEs (M3.9). About 55% of RQ CMEs were back sided, while the front-sided ones originated close to the limb. The RL CMEs originated generally on the disk with only ~25% being back sided. The RQ FW CMEs suggest that the Alfvén speed in the low-latitude outer corona can often exceed 1000 km s −1 and can vary over a factor of ≥3. None of the RQ CMEs was associated with large solar energetic particle events, which is useful information for space weather applications.