Regularities in the Formation of Coronal Mass Ejections Associated and not Associated with Type II Radio Bursts

Regularities in the formation of coronal mass ejections (CMEs) associated (Radio Loud, RL CME) and not associated (Radio Quiet, RQ CME) with type II radio bursts (RBIIs) in cycles 23 and 24 are reviewed. It is shown that the number of observed RQ and RL CME events and their parameters are quite different in cycles 23 and 24. The influence of the magnetic field and plasma parameters on the number of observed RQ and RL CME events and their parameters have been studied. The magnetic field in the region of RL CME detection was computed based on the observed, large-scale, photospheric magnetic field of the Sun, while we used direct observations of the plasma density in the Earth's orbit to calculate for the plasma density. This enabled us to obtain the Alfven speed and to examine the influence of cyclical variation of the magnetic field, plasma density, and Alfven speed on the number of events and RQ and RL CME parameters. The results show that magnetic field and plasma values may be among the key factors determining the conditions, which are favorable for the formation of RQ CMEs or RL CMEs.