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Anomalous transport: Difference between revisions
→Can anomalous transport be modelled?
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== Can anomalous transport be modelled? == | == Can anomalous transport be modelled? == | ||
There are several answers to this question. Since all equations describing the motion of charged particles in fields are known, | There are several answers to this question. Since all equations describing the motion of charged particles in fields are known, as well as the effects of collisions, detailed numerical (gyrokinetic) simulations are possible. | ||
<ref>[http://link.aps.org/doi/10.1103/PhysRevLett.77.71 A.M. Dimits et al, ''Scalings of Ion-Temperature-Gradient-Driven Anomalous Transport in Tokamaks'', Phys. Rev. Lett. '''77''' (1996) 71 - 74]</ref> | <ref>[http://link.aps.org/doi/10.1103/PhysRevLett.77.71 A.M. Dimits et al, ''Scalings of Ion-Temperature-Gradient-Driven Anomalous Transport in Tokamaks'', Phys. Rev. Lett. '''77''' (1996) 71 - 74]</ref> | ||
However, due to the enormous disparity between the minimum and maximum scales involved (gyration times vs. transport times, and the gyroradius vs. the machine size), this is a major challenge. | However, due to the enormous disparity between the minimum and maximum scales involved (gyration times vs. transport times, and the gyroradius vs. the machine size), this is a major challenge. | ||
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An alternative approach is to model the net effect of turbulence without simulating the fine detail. | An alternative approach is to model the net effect of turbulence without simulating the fine detail. | ||
In doing so, it is not sufficient to introduce a simple additional "turbulent diffusivity", as this cannot possibly reproduce the observed global transport scaling behaviour. | In doing so, it is not sufficient to introduce a simple additional "turbulent diffusivity", as this cannot possibly reproduce the observed global transport scaling behaviour. | ||
It is probably necessary to use a [[Non-diffusive transport|non-diffusive]] description | It is probably necessary to use a [[Non-diffusive transport|non-diffusive]] description, | ||
<ref>[http://dx.doi.org/10.1016/S0370-1573(02)00331-9 G. M. Zaslavsky, ''Chaos, fractional kinetics, and anomalous transport'', Physics Reports '''371''', Issue 6 (2002) 461-580]</ref> | <ref>[http://dx.doi.org/10.1016/S0370-1573(02)00331-9 G. M. Zaslavsky, ''Chaos, fractional kinetics, and anomalous transport'', Physics Reports '''371''', Issue 6 (2002) 461-580]</ref> | ||
and include non-linear phenomena such as [[Self-Organised Criticality|critical gradients]]. | |||
== Can anomalous transport be controlled? == | == Can anomalous transport be controlled? == | ||