Associations of decimetric type III bursts with coronal mass ejections and Hα flares

We present a statistical study of decimetric type III radio bursts, coronal mass ejections (CMEs), and Hα flares observed in the period from July 2000 to March 2005. In total, we investigated 395 decimetric type III radio burst events, 21% of which showed apparent correlation to CMEs that were associated with Hα flares. We noticed that the Hα flares which were strongly associated with CMEs were gradual events, and 82% of them took place before CMEs appeared in the field of view of LASCO C2; that most of the CME-associated radio bursts started in the frequency range around 750 MHz with a frequency drifting rate of several hundred MHz s⁻¹, of which both positive and negative ones were recognized; and that the correlation of type III radio bursts to CMEs without associated flares is fairly vague, less than 9%.