München 2019 – wissenschaftliches Programm
P 7.3: Vortrag
Montag, 18. März 2019, 17:25–17:50, HS 21
Linear and nonlinear dynamics of GAMs and EGAMs — •Ivan Novikau1, Alessandro Biancalani1, Alberto Bottino1, Peter Manz1, Garrard D. Conway1, Alessandro Di Siena1, Philipp Lauber1, Emanuele Poli1, Emmanuel Lanti2, Laurent Villard2, Noé Ohana2, and Asdex Upgrade Team1 — 1IPP, Garching, Germany — 2SPC-EPFL, Lausanne, Switzerland
Turbulence in tokamaks generates radially sheared zonal flows (ZFs), that can reduce the radial transport in the system. Their oscillatory counterparts, geodesic acoustic modes (GAMs), appear due to the action of the magnetic field curvature. The GAMs can be driven by energetic particles leading to the formation of EGAMs. In addition to ion Landau damping (LD), both the GAMs and EGAMs have been found to be subject to the electron LD. Due to that, the EGAMs can spread energy from the fast particles to the thermal plasma. To investigate the influence of the electron LD on the EGAMs, a Mode-Particle-Resonance diagnostic has been implemented in the global gyrokinetic (GK) PIC code ORB5. Based on the projection of the energy transfer terms on the velocity domain, the diagnostic gives an opportunity to estimate the contributions of different resonances to the mode's dynamics. It has been applied in electromagnetic GK simulations of the NLED AUG shot #31213 to show the influence of the drift-kinetic electrons on the EGAM dynamics. The second part of the talk is dedicated to the nonlinear interaction of zonal structures and turbulence in AUG shot #20787. GAM excitation by ITG instabilities will be shown with a good numerical prediction of the GAM frequency scaling.