  Magnetic islands (MIs), resulting from a magnetic field reconnection, are
ubiquitous structures in magnetized plasmas. In tokamak plasmas, recent
researches suggested that the interaction between the MI and ambient turbulence
can be important for the nonlinear MI evolution, but a lack of detailed
experimental observations and analyses has prevented further understanding.
Here, we provide comprehensive two-dimensional observations that indicate
various effects of the ambient turbulence on the nonlinear MI evolution. It is
shown that the modified plasma turbulence around the MI can lead to either
destabilization or stabilization of the MI instability in tokamak plasmas. In
particular, significantly enhanced turbulence at the X-point of the MI results
in a violent disruption through the fast magnetic reconnection and magnetic
field stochastization.
