Physics of zonal flows

Itoh, K.; Itoh, S.-I.; Diamond, P. H.; Hahm, T. S.; Fujisawa, A.; Tynan, G. R.; Yagi, M.; Nagashima, Y.

doi:doi:10.1063/1.2178779

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Neoclassical tearing modes and their control

A principal pressure limit in tokamaks is set by the onset of neoclassical tearing modes (NTMs), which are destabilized and maintained by helical perturbations to the pressure-gradient driven “bootstrap” current. The resulting magnetic islands break up the magnetic surfaces that confine the plasma. The NTM is linearly stable but nonlinearly unstable, and generally requires a “seed” to destabilize a metastable state. In the past decade, NTM physics has been studied and its effects identified as ...

Plasma accelerators race to 10 GeV and beyond

This paper reviews the concepts, recent history, and current challenges for realizing ultracompact particle accelerators based on surfing on plasma waves. Ideas that seemed fanciful when first proposed by John Dawson in the late 1970s have now come to fruition as a result of the development of ultrashort high-power laser and particle beam drivers, tunnel-ionized plasma sources, and one-to-one particle simulation capability. Breakthroughs in the past 2 years have dramatically advanced the field....

Zonal flows, which means azimuthally symmetric band-like shear flows, are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows are a key constituent in virtually all cases and regimes of drift wave turbulence, indeed, so much so that this classic problem is now frequently referred to as “drift wave-zonal flow turbulence.” In this review, new viewpoints and unifying concepts are presented, which facilitate understanding of zonal flow physics, via theory, computation and their confrontation with the results of laboratory experiment. Special emphasis is placed on identifying avenues for further progress.

Article Outline

INTRODUCTION
BASIC PHYSICS OF ZONAL FLOWS
1. Characteristic features of zonal flows
2. Excitation of zonal flows
3. Self-regulation of the DW-ZF system
IMPORTANCE OF ZONAL FLOWS FOR MAGNETIC CONFINEMENT FUSION RESEARCH
ZONAL FLOW PHYSICS—A CRITICAL ASSESSMENT
1. What we understand about zonal flows
2. What we think we understand about zonal flows, but need more research on
EXPERIMENTAL STUDIES
1. Identification of ZFs and spatiotemporal structure
  1. Low frequency ZFs
  2. GAMs
2. Generation of flow shear (torque) by turbulence
3. Nonlinear coupling coefficient between ZFs and microturbulence
  1. Bicoherence analysis
  2. Energy transfer between fluctuations
  3. Envelope modulation
4. Suppression of turbulent fluctuations by ZFs
FUTURE RESEARCH—WHAT WE DO NOT YET UNDERSTAND ABOUT ZONAL FLOW PHYSICS
CONCLUSION

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KEYWORDS and PACS

Keywords

plasma flow, shear flow, plasma drift waves, plasma turbulence, plasma transport processes, reviews

PACS

52.30.-q

Plasma dynamics and flow
52.35.Kt

Drift waves
52.35.Ra

Plasma turbulence
52.25.Fi

Transport properties
01.30.Rr

Surveys and tutorial papers; resource letters

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http://link.aip.org/link/doi/10.1063/1.2178779

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1070-664X (print)

1089-7674 (online)

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American Institute of Physics

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