Generation of a magnetic island by edge turbulence in tokamak plasmas

International audienceWe investigate, through extensive 3D magneto-hydro-dynamics numerical ă simulations, the nonlinear excitation of a large scale magnetic island ă and its dynamical properties due to the presence of small-scale ă turbulence. Turbulence is induced by a steep pressure gradient in the ă edge region [B. D. Scott, Plasma Phys. Controlled Fusion 49, S25 ă (2007)], close to the separatrix in tokamaks where there is an X-point ă magnetic configuration. We find that quasi-resonant localized ă interchange modes at the plasma edge can beat together and produce ă extended modes that transfer energy to the lowest order resonant surface ă in an inner stable zone and induce a seed magnetic island. The island ă width displays high frequency fluctuations that are associated with the ă fluctuating nature of the energy transfer process from the turbulence, ă while its mean size is controlled by the magnetic energy content of the ă turbulence. (C) 2015 AIP Publishing LLC