Sandpile dynamics as a paradigm for turbulent transport
Sandpile dynamics as a paradigm for turbulent transport To shed some light on the apparent discrepancies between most theoretical models of turbulent transport and experimental observations of the transport in magnetically confined plasmas, a model for transport has been developed based on the concept of self-organized criticality (SOC). This model seeks to describe the dynamics of the transport without relying on the underlying local fluctuation mechanisms. Computations based on a cellular automata model have found that SOC systems maintain average profiles that are linearly stable (submarginal) and yet are able to sustain active transport dynamics in contrast to naive marginal stability arguments. It is also found that the dominant scales in the transport dynamics in the absence of sheared flow are system scales rather than the underlying local fluctuation scales. However, the addition of sheared flow into the dynamics leads to a large reduction of the system-scale transport events and a commensurate increase in the fluctuation-scale transport events needed to maintain the constant flux. The dynamics of these models and the potential ramifications for transport studies are discussed.
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