A mechanism for magnetic field stochastization and energy release during an edge pedestal collapse

Abstract

On the basis of three-dimensional nonlinear magnetohydrodynamic simulations, we propose a new dynamical process leading to the stochastization of magnetic fields during an edge pedestal collapse. Primary tearing modes are shown to grow by extracting kinetic energy of unstable ballooning modes, eventually leading to the island overlap. Secondary tearing modes, which are generated through a coherent nonlinear interaction between adjacent ballooning modes, play a key role in this process, mediating the energy transfer between primary ballooning and tearing modes. Explicit calculations of the parallel energy loss through the stochastic field lines show that it can be a likely dominant energy loss mechanism during an edge pedestal collapse.