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1 Space Research Institute, Austrian Academy of Sciences, Graz, Austria 2 Institut für Geophysik und extraterrestrische Physik, Technische Universität Braunschweig, Braunschweig, Germany 3 Institut für Theoretische Physik, Technische Universität Braunschweig, Braunschweig, Germany 4 Institute for Space Sciences, Bucharest-Măgurele, Romania 5 Institut für Planetenforschung, Deutsches Zentrum für...

Sheared toroidal flows can cause bifurcations to zero-turbulent-transport states in tokamak plasmas. The maximum temperature gradients that can be reached are limited by subcritical turbulence driven by the parallel velocity gradient. Here it is shown that q/ϵ (magnetic field pitch/inverse aspect ratio) is a critical control parameter for sheared tokamak turbulence. By reducing q/ϵ, far higher ...

The probability distribution function of plasma density fluctuations at the edge of fusion devices is known to be skewed and strongly non-Gaussian. The causes of this peculiar behavior are, up to now, largely unexplored. On the other hand, understanding the origin and the properties of edge turbulence is a key issue in magnetic fusion research. In this paper we show that a stochastic fragmentat...

The statistical properties of the E ×B flux in different types of plasma turbulence simulations are investigated using probability density distribution functions (PDF). The physics included in the models ranges from two dimensional drift-wave turbulence to three dimensional MHD simulations. The PDFs of the flux surface averaged transport are in good agreement with an extreme value distribution ...

We examine and intcrcornpare the LF plasma wave turbulence at three comets: Cirjgg-Skjcllcrup, (CiS), Giacobini-Zinncr (GZ) and IIallcy (H). All three have power spectral peaks at the local ion cyclotron frequency (the pump wave) at 10-2 }Iz, and a power-law fall-off at higher frcqucncics that suggest the development of turbulent cascades (Acuna, 1986). The power law for the three comets are ap...

The impact of plasma shaping on tokamak scrape-off layer (SOL) turbulence is investigated. The drift-reduced Braginskii equations are written for arbitrary magnetic geometries, and an analytical equilibrium model is used to introduce the dependence of turbulence equations on tokamak inverse aspect ratio ( ), Shafranov’s shift (∆), elongation (κ), and triangularity (δ). A linear study of plasma ...

Evidence accumulated over the past several decades indicates that a large-scale applied (dc) magnetic field imposes a preferred direction on turbulence, and thus plays an important role in plasma diffusion [1], energetic particle scattering [2], and plasma heating [3–5]. Each of these in turn may significantly influence large-scale flows and structure [6–8]. The interplay between turbulence and...

Collective plasma phenomena induced in the ionospheric F-region by intense high-frequency radiation are examined on several time and length scales. The short wavelengh, high-frequency turbulence associated with the observed high-frequency enhanced electron density fluctuations at the electron plasma frequency is shown to result from parametric excitation of plasma and acoustic waves by the high...

The mutual interactions of ion temperature gradient (ITG) driven modes, zonal flows and geodesic acoustic modes (GAM) in tokamak plasmas are investigated using a global nonlinear gyrokinetic formulation with totally unconstrained evolution of temperature gradient and profile. A series of numerical simulations with the same initial temperature and density profile specifications is performed usin...