Radio‐Quiet Fast and Wide Coronal Mass Ejections

Abstract

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 lacktype II radio bursts in the metric and decameter-hectometric (DH)wavelengths. RL CMEs are associated with metric or DH type II bursts. Wefound that ~40% of the FW CMEs from 1996 to 2005 were RQ. The RQ CMEshad an average speed of 1117 km s-1 compared to 1438 kms-1 for the RL, bracketing the average speed of all FW CMEs(1303 km s-1). The fraction of full halo CMEs (apparentwidth=360deg) was the largest for the RL CMEs (60%), smallestfor the RQ CMEs (16%), and intermediate for all FW CMEs (42%). Themedian soft X-ray flare size for the RQ CMEs (C6.9) was also smallerthan 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 CMEsoriginated generally on the disk with only ~25% being back sided. The RQFW CMEs suggest that the Alfvén speed in the low-latitude outercorona can often exceed 1000 km s-1 and can vary over afactor of >=3. None of the RQ CMEs was associated with large solarenergetic particle events, which is useful information for space weatherapplications.