Hannover 2010 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 5: Theory/Modelling I

P 5.3: Vortrag

Dienstag, 9. März 2010, 14:55–15:10, B 302

Magnetic geometry effects on geodesic acoustic modes — •Robert Hager and Klaus Hallatschek — Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, D-85748 Garching, Germany

The approach to the calculation of the GAM group velocity from the radial free energy flux and the total free energy presented in Phys. Plasmas 16, 072503 (2009) is generalized to up-down asymmetric magnetic geometries. By removing the neoclassical cancellation effects, up-down asymmetry can trigger a non-vanishing group velocity at zero radial wavenumber. Adequate shaping of the plasma allows control of the direction and magnitude of the GAM group velocity, which can be of the order of the magnetic drift velocity or larger. Altering the direction and speed of the GAM propagation might be used to check for a potential influence on the confinement and even on the H-mode.

Taking up recent reports on GAM eigenmodes and the role of GAMs in turbulence saturation, the influence of the magnetic geometry on GAMs and their interaction with turbulence is investigated using numerical two-fluid studies. While preserving the properties of the turbulent modes, the magnetic configuration is varied to study how the GAM spectrum, the structure of GAM eigenmodes, and the ability of GAMs to modulate turbulent transport depend on geometry parameters such as the plasma elongation.