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The nonlinear evolution of the m=1 internal kink mode is studied numericallyin a setting where the tokamak core plasma is surrounded by a turbulent regionwith low magnetic shear. As a starting point we choose configurations withthree nearby q=1 surfaces where triple tearing modes (TTMs) with high poloidalmode numbers m are unstable. While the amplitudes are still small, the fastgrowing high-m TTMs enhance the growth of the m=1 instability. This isinterpreted as a fast sawtooth trigger mechanism. The TTMs lead to a partialcollapse, leaving behind a turbulent belt with q ~= 1 around the unreconnectedcore plasma. Although, full reconnection can occur if the core displacementgrows large enough, it is shown that the turbulence may actively preventfurther reconnection. This is qualitatively similar to experimentally observedpartial sawtooth crashes with post-cursor oscillations due to a saturatedinternal kink.Comment: 14 pages, 13 figure

Nonlinear evolution of the m=1 internal kink mode in the presence of magnetohydrodynamic turbulence