Mixed SOC diffusive dynamics as a paradigm for transport in fusion devices

A recently proposed paradigm for understanding turbulent transport dynamics in magnetically confined plasmas, based on the concept of self-organized criticality (SOC), is extended to include the interplay among the many transport mechanisms existing in real plasmas. This extended model might shed some light on the experimentally observed violation at fluctuation scales of the scale invariance condition inherent to the standard SOC model. At the same time, it might provide new experimental tests that could help to validate the possible relevance of the SOC model for understanding turbulent plasma dynamics, since some computations based on a cellular automata realization of such an extended model reveal a dramatic change in the dynamics, with the edge coming to play a dominant role. This might give some hints towards understanding the experimental fact relating good plasma core confinement to a good conditioning of the edge within an SOC paradigm. (author)