Nonlinear dynamics of magnetic islands in presence of interchange turbulence

In this work, we study the interaction between a tearing mode and a pressure gradient instability (resistive interchange) by solving reduced MHD equations numerically. The numerical study shows existence of regimes where thetearing instability is driven by the pressure gradient. An interplay between the pressure and the magnetic flux controls the dynamics of the saturated state. A secondary instability, triggered by interchange unstable modes, produces convective cells which modify the nature of the magnetic island. The system reaches a new state where small scales are produced and the diamagnetic effect is strongly enhanced as well as the poloidal rotation.