Ultra long turbulent eddies, magnetic topology, and the triggering of internal transport barriers in tokamaks

Abstract Local nonlinear gyrokinetic simulations of tokamak plasmas demonstrate that turbulent eddies can extend along magnetic field lines for hundreds poloidal turns when the shear is very small. By accurately modeling different line topologies (e.g. low-order rational, almost or irrational value safety factor), we show self-interaction such ‘ultra long’ dramatically reduce heat transport. This extreme sensitivity transport to factor reveals novel strategies improve confinement, constitutes experimentally testable predictions, and illuminates past observations internal barriers.