Frequency chirping of core-localized toroidicity-induced Alfven eigenmodesand their coupling to global Alfven eigenmodes

The fast frequency change or chirping of core-localized toroidicity-induced Alfven eigenmodes (C-TAE), excited before giant sawteeth during ion cyclot ron resonance heating, has been investigated. The chirping can be accounted for by small changes of the central q profile. When the C-TAE crosses the frequency of a global TAE (G-TAE) a small frequency gap was found. These ga ps can be attributed to mode coupling between the C-TAE and a G-TAE which i s observed for the first time. The coupling and the frequency gaps are cons istent with linear TAE mode coupling.