SELF-ORGANIZED CRITICALITY IN PARTICLE-TRANSPORT GOVERNED BY IONIZATION

The turbulent particle transport is analyzed as a self-organized syste m driven by ionization. The region characterized by a gradient compara ble to the critical gradient is found to extend over three times the n eutral penetration depth. As observed in experiments, the density fluc tuations peak inside the plasma while the relative density fluctuation s increase monotonously to the plasma boundary. The time average macro scopic transport exhibits two distinct diffusion regimes associated to inward pinch velocities. These regimes correspond to trapping or pass ing of avalanches of states with sub- or super-critical gradients. The se two regimes are localized in the regions with super-and sub-critica l average gradients respectively.