Self-organized criticality in particle transport governed by ionization

The turbulent particle transport is analyzed as a self-organized system driven by ionization. The region characterized by a gradient comparable to the critical gradient is found to extend over three times the neutral penetration depth. As observed in experiments, the density fluctuations peak inside the plasma while the relative density fluctuations increase monotonously to the plasma boundary. The time average macroscopic transport exhibits two distinct diffusion regimes associated to inward pinch velocities. These regimes correspond to trapping or passing of avalanches of states with sub- or super-critical gradients. These two regimes are localized in the regions with super-and sub-critical average gradients respectively.