Scale selection and feedback loops for patterns in drift wave-zonal flow turbulence
- Huazhong Univ. of Science and Technology, Wuhan (China)
- Univ. of California San Diego, La Jolla, CA (United States)
- Univ. of Leeds (United Kingdom)
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
The scale selection and feedback loops for the formation and sustainment of a mesoscopic staircase profile structure are investigated for drift wave-zonal flow turbulence. A mean field model derived from the Hasegawa-Wakatani system and including the evolution of mean density, mean vorticity and perturbed potential enstrophy (PE), is used. Here, it is found that a quasi-periodic zonal staircase forms from self-sharpening of modulation. The principle feedback loop is through the nonlinear dependence of mixing length on electron density gradient, which enters by way of the potential vorticity (PV) gradient. Counterintuitively, E×B shearing is not effective. Moreover, the number of steps in the staircase is sensitive to both the drive (production rate of PE and initial density gradient) and damping (flow viscosity and collisional diffusivity) factors. The minimal step scale is selected by competition between the initial density gradient and diffusive dissipation. Finite turbulence spreading is necessary to form the staircase, but moderate enhancement of turbulence spreading tends to wash out the pattern. The staircase retains a memory of its initial state. Both the mean E×B shear and zonal shear affect the staircase evolution. A strong mean shear quenches the pattern by suppressing the drift wave turbulence. Lastly, the implications of these findings are also discussed.
- Research Organization:
- Univ. of California, San Diego, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Grant/Contract Number:
- FG02-04ER54738
- OSTI ID:
- 1546784
- Journal Information:
- Plasma Physics and Controlled Fusion, Vol. 61, Issue 10; ISSN 0741-3335
- Publisher:
- IOP ScienceCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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