SPECIAL SEMINAR: Recent advances in understanding nonlocal transport in fusion plasmas

Abstract:

There is an increasing amount of evidence indicating the importance of mesoscopic transport phenomena in fusion plasmas, which show limitations of conventional approach of local turbulence and quasilinear fluxes. This presentation will cover some highlights from a recent review article and of more recent findings afterwards. Both turbulence spreading and avalanching provide a natural understanding of the observed breakdown of the expected local (gyro-Bohm) transport scaling. The spreading is widely observed in global gyrokinetic simulations, and discussed in the context of Fisher-Kolmogoroff equation, which describes the spatio-temporal evolution of intensity fronts. Avalanching is a process in which correlated over-turns of neighboring eddies drive a burst of transport with a range of mesoscopic radial scales between the microscopic eddy size and macroscopic system size. Joint reflection symmetry of blob/void pairs expected from self-organized-critical system has been recently observed in recent KSTAR experiments and gyrofluid simulation. Other outstanding examples of nonlocal transport include the ExB staircase and turbulence-magnetic island interactions.