Non-diffusive transport: Difference between revisions

There may ''turbulent eddies'' in which particles become trapped for some time, and there certainly are ''transport barriers'', associated with rational magnetic surfaces, and ''stochastic regions'' of the magnetic field. This could cause the waiting time distribution to become non-exponential; therefore motion being non Markovian. Likewise, the phenomenon of ''streamers'', appearing in many models of plasma turbulence, could carry particles across long distances in the radial direction, and the distribution of particle steps could then also be deformed and develop ''long tails''. Consequently, the transport is said to be non local, as long range events probability is not negligible. Nobody knows exactly how important these phenomena are in the global transport picture.

Another approach is to test whether non-diffusive transport phenomena actually occur in simulations and experiment. To do so, ''tracer particles'' are injected into the plasma fluid, and their evolution is followed in time. Since the ''tracers'' are expected to catch the essential underlying physics, their trajectories provide information about the motion. These trajectories can be studied by means of several analysis techniques, calculating for instance the relevant probability distributions related to the transport, or detecting correlations in the velocity.  The application of this method has yielded clear indications that plasma turbulence induces non-diffusive transport in simulations.