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Anomalous transport: Difference between revisions
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=== Arguments in favour === | === Arguments in favour === | ||
An important argument suggesting that anomalous transport is important to the degree that it often dominates the total transport is the [[Scaling law|scaling]] of transport with heating power and machine size. The phenomenon of [[Scaling law|power degradation]], universally observed in all devices, is an indication that standard (linear, diffusive) transport theories are inadequate to explain all transport, since these would not predict power degradation. | |||
However, the matter is complicated by the fact that the transport coefficients themselves are functions of the (local) plasma parameters, so that the transport theory becomes non-linear. | However, the matter is complicated by the fact that the transport coefficients themselves are functions of the (local) plasma parameters, so that the (non-anomalous) transport theory becomes non-linear. | ||
[[Profile consistency]] indicates that [[Self-Organised Criticality|self-organisation]] plays an important role in transport, and this can only be the case when instabilities or turbulence are able to regulate the profiles, i.e., when they carry an important fraction of transport. | [[Profile consistency]] indicates that [[Self-Organised Criticality|self-organisation]] plays an important role in transport, and this can only be the case when instabilities or turbulence are able to regulate the profiles, i.e., when they carry an important fraction of transport. | ||
The suppression of turbulence is possible, either actively (by imposing an external radial electric field), or spontaneously ([[H-mode]]s, [[Internal Transport Barrier]]s). As a consequence, transport is reduced significantly (to Neoclassical levels). This is a clear indication that turbulence is responsible for the main fraction of anomalous transport. | The suppression of turbulence is possible, either actively (by imposing an external radial electric field), or spontaneously ([[H-mode]]s, [[Internal Transport Barrier]]s). As a consequence, transport is reduced significantly (to Neoclassical levels). This is a clear indication that turbulence is responsible for the main fraction of anomalous transport. | ||
=== Arguments against === | === Arguments against === | ||