Global theory of beta-induced Alfvén eigenmode excited by energetic ions

The two-dimensional global stability and mode structures of high-n beta-induced Alfvén eigenmodes excited by energetic ions in tokamaks are examined both analytically and numerically, employing the WKB-ballooning mode representation along with the generalized fishbone like dispersion relation. Here, n 蠑 1 is the toroidal mode number. Our results indicate that (i) the lowest radial bound state corresponds to the most unstable eigenmode, and (ii) the anti-Hermitian contributions due to wave-energetic particle resonance give rise to the twisting radial mode structures. © 2015 AIP Publishing LLC.