The linear stability analysis of the ITG modes in a plasma slab with an equilibrium ion flow has been carried out by solving the relevant eigenvalue equation for the complex electrostatic fluctuation amplitude φk , by retaining the electric, the diamagnetic and the gravitational-like drifts. For sufficiently broad T i profiles, a novel regime with two-branch distributions of unstable eigenvalues has been found, which seems to be characterized by a broad radial correlation length. The plasma density profile and a macroscopic ion flow aligned to the magnetic field govern the relative importance of the two unstable sets of eigenfunctions.
The experimental observation of the association of the internal heat transport barriers in tokamaks with rational q surfaces is an open problem. Often the mechanism invoked for the onset of an internal transport barrier relies on the reduction of turbulence by a local increase of the E × B velocity shear. In this paper, we present in some detail the theoretical analysis of the possible role of an externally applied electrodynamic torque, resonant on a rational surface with the support of selected Joint European Torus experimental results.
The linear dispersion of the ion temperature gradient (ITG) modes, in the presence of a non uniform background ion velocity U || = U || (x) e z , in the direction of the sheared equilibrium magnetic field B 0 = B 0 (x) e z , has been studied in the frame of the two-fluid guiding center approximation, in slab geometry. Generally speaking, the presence of an ion flow destabilizes the oscillations. The role of the excited K-H instability is discussed.
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