Secondary instability in drift wave turbulence as a mechanism for zonal flow and avalanche formation

Abstract

The article reports on recent developments in the theory of secondary instability in drift-ion temperature gradient turbulence. Specifically, the article explores secondary instability as a mechanism for zonal flow generation, transport barrier dynamics and avalanche formation. These in turn are related to the space-time statistics of the drift wave induced flux, the scaling of transport with collisionality and β, and the spatio-temporal evolution of transport barriers.

On Imaging of Plasma Turbulence

“…These observations demonstrate that the microscopic fluctuations and the meso-scale perturbation (GAMs) interact through modulational nonlinear coupling. This process has been theoretically pointed out as the driving mechanism of zonal flows in plasma turbulence [4,6,8,30,31]. Further studies have been done for the magnitude of nonlinear coupling, and experiments have given confirmation to the theoretical predictions (within the experimental error) if the convergence study is carefully performed [32].…”

“…For recent development of statistical theory in turbulent plasmas, readers are referred to Refs. [1,6,[36][37][38][39][40] The fluctuating force from background broadband turbulence can induce stochastic transition in global dynamics. This is one of the processes that determine the lifetime of structures.…”

“…4 (b)). The zonal flows in turn suppress the microscopic fluctuations, thus reducing the heat transport from the hot center to the cold periphery [4][5][6][7][8][10][11][12][13][14]. In addition to this coupling between micro fluctuations and zonal flows, there are many nonlinear mechanisms that induce structured flow of plasmas.…”

“…By employing the bipspectral method [3], magnitudes of interactions among excited modes are measured and comparisons with theoretical modeling are performed. Interactions between microscopic turbulence, meso scale fluctuations [4][5][6] and large-scale structures are also demonstrated [1,7,8], providing our understanding of 'how global structures are generated by turbulence'. This is a new step in establishing imaging of plasma turbulence.…”

Heavy Ion Beam Probe, Present Status and Future Development

“…Drake pointed out that slab plasmas have sharp structures, very narrow in poloidal diauthor's e-mail: hamada@nifs.ac.jp rections and wide in radial direction by the buildup of the potential difference along poloidal direction and called this flow as streamers [3]. Later streamers and zonal flows are found to be fundamental phenomena in the large-scale computer simulation of tokamak plasmas [4][5][6][7][8][9][10][11].…”