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TJ-II:Turbulence: Difference between revisions
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The analysis of data from Langmuir probes taken at the plasma edge in a wide variety of fusion devices reveals the existence of self-similar behaviour or long-range correlations in all devices studied. The observed variation of the Hurst exponent in the plasma edge, 0.62 < H < 0.75, is small in spite of the variety of devices. | The analysis of data from Langmuir probes taken at the plasma edge in a wide variety of fusion devices reveals the existence of self-similar behaviour or long-range correlations in all devices studied. The observed variation of the Hurst exponent in the plasma edge, 0.62 < H < 0.75, is small in spite of the variety of devices. | ||
<ref>[http://link.aip.org/link/?PHPAEN/5/3632/1 B.A. Carreras et al, ''Self-similarity of the plasma edge fluctuations'', Phys. Plasmas '''5''', 10 (1998) 3632]</ref> | <ref>[http://link.aip.org/link/?PHPAEN/5/3632/1 B.A. Carreras et al, ''Self-similarity of the plasma edge fluctuations'', Phys. Plasmas '''5''', 10 (1998) 3632]</ref> | ||
On the other hand, the variation of H in the | On the other hand, the variation of H in the [[Scrape-Off Layer]] (SOL) is much larger. In Wendelstein VII-AS, a slight decrease in H at the sheared flow layer was observed, possibly corresponding to a local decorrelation effect. | ||
The repeated occurrence of values of H differing significantly from the value corresponding to random noise (H = 0.5) in all machines points to a universal aspect of the underlying turbulence. Further, the degree of self-similarity detected implies the existence of long-range correlations (with respect to the correlation time). | The repeated occurrence of values of H differing significantly from the value corresponding to random noise (H = 0.5) in all machines points to a universal aspect of the underlying turbulence. Further, the degree of self-similarity detected implies the existence of long-range correlations (with respect to the correlation time). | ||