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Self-Organised Criticality: Difference between revisions
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Power degradation shows up in global transport scaling laws, and implies a sub-linear scaling of the plasma energy content with the injected power. | Power degradation shows up in global transport scaling laws, and implies a sub-linear scaling of the plasma energy content with the injected power. | ||
The basic explanation for this phenomenon is self-regulation of the profiles by turbulence. The strong temperature and density gradients in fusion-grade plasmas provide free energy that may drive turbulence. The turbulence then enhances transport locally, leading to a local reduction of gradients and a consequential damping of the turbulence amplitude. This feedback could be responsible for keeping the gradients below a critical value. Considered locally, the former is a description of a simple marginal state. | The basic explanation for this phenomenon is self-regulation of the profiles by turbulence. | ||
<ref>[http://link.aip.org/link/?PHPAEN/3/1858/1 D.E. Newman et al., Phys. Plasmas '''3''', 1858 (1996)]</ref> | |||
The strong temperature and density gradients in fusion-grade plasmas provide free energy that may drive turbulence. The turbulence then enhances transport locally, leading to a local reduction of gradients and a consequential damping of the turbulence amplitude. This feedback could be responsible for keeping the gradients below a critical value. Considered locally, the former is a description of a simple marginal state. | |||
But the interaction of such feedback mechanisms at various radial locations would lead to ''avalanche'' behaviour and a true (scale-free) self-organised state. | But the interaction of such feedback mechanisms at various radial locations would lead to ''avalanche'' behaviour and a true (scale-free) self-organised state. | ||