Trajectory trapping and the evolution of drift turbulence beyond the quasilinear stage

Abstract

Test modes on turbulent magnetized plasmas are studied taking into account the ion trapping that characterizes the E x B drift in the background turbulence. We show that trappyng provides the physical mechanism for the formation of large scale potential structures (inverse cascade) observed in drift turbulence. Trapping combined with the motion of the potential with the diamagnetic velocity determines ion flows in opposite directions, which reduce the growth rate and eventually damps the drift modes. It also determine transitory zonal flow modes in connection with compressibility effect due to the polarization drift in the background turbulence.