Fokker-Planck simulation study of Alfven eigenmode bursts

Recurrent bursts of toroidicity induced Alfven eigenmodes (TAEs) are reprod uced with a Fokker-Planck-MHD simulation where a fast ion source and slowin g down are incorporated self-consistently. The bursts take place at regular time intervals and the behaviours of all the TAEs are synchronized. The fa st ion transport due to TAE activity spatially broadens the classical fast ion distribution and significantly reduces its peak value. Only a small cha nge of the distribution takes place with each burst, leading to loss of a s mall fraction of the fast ions. The system stays close to the marginal stab ility state established through the interplay of the fast ion source, slowi ng down and TAE activity.