Nonlinear evolution of q=1 triple tearing modes in a tokamak plasma.
In magnetic configurations with two or three q=1 (with q being the safety factor) resonant surfaces in a tokamak plasma, resistive magnetohydrodynamic modes with poloidal mode numbers m much larger than 1 are found to be linearly unstable. It is found that these high-m double or triple tearing modes significantly enhance through nonlinear interactions the growth of the m=1 mode. This may account for the sudden onset of the internal resistive kink, i.e., the fast sawtooth trigger. Based on the subsequent reconnection dynamics that can proceed without formation of the m=1 islands, it is proposed that high-m triple tearing modes are a possible mechanism for precursor-free partial collapses during sawtooth oscillations.
Bierwage
Andreas
A
Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan. bierwage@center.iae.kyoto-u.ac.jp
Hamaguchi
Satoshi
S
Wakatani
Masahiro
M
Benkadda
Sadruddin
S
Leoncini
Xavier
X