The formation of a static 3D helically localized perturbation structure of the toroidal Alfvén eigenmode (TAE) is observed for the first time under static magnetic islands induced by resonant magnetic perturbations (RMPs) in tokamak plasmas. Before the application of RMP, a TAE around 200 kHz is excited by electron cyclotron resonance heating-induced energetic electrons. After the application of n = 1 RMP, the TAE mode is localized into a helical region on the flux surface, where n is the toroidal mode number. We find that the TAE mode is strengthened near the X points of the magnetic islands and weakened near the island O points, where m is the poloidal mode number. This novel observation reveals the potential of RMPs to modify the distribution of energetic particles (EPs) both in geometry and velocity space, and hence to actively change the structure and stability of EP-driven modes in fusion plasmas.
This paper reports the first observation of a static 3D helical structure of the toroidal Alfven eigenmode (TAE) induced by resonant magnetic perturbations (RMPs) in a tokamak. The TAE mode is strengthened near the X-points of the magnetic islands and weakened near the O-points, indicating the potential of RMPs to modify the distribution of energetic particles and actively control the stability of energetic particle-driven modes in fusion plasmas.