Suppression of MHD instabilities using RF waves in tokamaks.

Recent progresses in theories and experiments on the suppression of resistive MHD instabilities in tokamaks using RF waves are reviewed. Topics are focussed on (i) the m=2 tearing mode stabilization with lower hybrid current drive as well as electron cyclotron resonance heating for the prevension of major disruptions and (ii) the sawtooth mode stabilization using lower hybrid waves. New quasilinear theories on the magnetic island behavior under the presence of RF waves are also discussed.