Bremen 2017 – scientific programme
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P: Fachverband Plasmaphysik
P 22: Theory and Modelling II
P 22.4: Poster
Wednesday, March 15, 2017, 16:30–18:30, HS Foyer
Numerical investigation of the dynamics of geodesic acoustic modes in tokamak plasmas. — •Ivan Novikau1, Alessandro Biancalani1, Alberto Bottino1, Garrard Conway1, Peter Manz1, Pierre Morel2, Özgür Gürcan2, and Emanuele Poli1 — 1Max Planck Institute of Plasma Physics — 2Laboratoire de Physique des Plasmas, Ecole Polytechnique
Tokamak micro-turbulence is often accompanied by meso-scale electric fields that take the form of radially sheared poloidal ExB flows, named zonal flows (ZFs). These flows are driven by nonlinear interactions with the turbulence and, in turn, they can regulate the plasma transport via flow shearing. The action of curvature in tokamak on ZFs gives rise to oscillations of radial electric field called the geodesic acoustic modes (GAMs) which are observed mainly in the external region of tokamak plasmas, with characteristic frequencies of the order of the sound frequency, and mainly m=0 n=0 potential perturbation and m=1 n=0 density perturbation (with m and n being respectively the poloidal and toroidal mode numbers). Nonlinear interaction between turbulence and these structures is crucial for turbulence saturation.
Different characteristics like GAM frequency and collisionless damping rate are investigated by means of numerical simulations with the global gyrokinetic particle-in-cell code ORB5 and different numerical diagnostics. The influence of the plasma shape, density and temperature gradients is studied with the aim of making predictions for realistic tokamak geometries. The effect of kinetic electrons is considered for realistic electron masses.