title: Nonlinear evolution of q=1 triple tearing modes in a tokamak plasma.
abstract: 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.
authors.affiliation: Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan. bierwage@center.iae.kyoto-u.ac.jp
authors.forename: Andreas
authors.initials: A
authors.lastname: Bierwage
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hamaguchi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Wakatani
authors.forename: Sadruddin
authors.initials: S
authors.lastname: Benkadda
authors.forename: Xavier
authors.initials: X
authors.lastname: Leoncini