Linear gyrokinetic investigation of the geodesic acoustic modes in realistic tokamak configurations

Abstract

Geodesic acoustic modes (GAMs) are studied by means of the gyrokinetic global particle-in-cell code ORB5. Linear electromagnetic simulations in the low electron beta limit have been performed, in order to separate acoustic and Alfvénic time scales and obtain more accurate measurements. The dependence of the frequency and damping rate on several parameters such as the safety factor, the GAM radial wavenumber and the plasma elongation is studied. All simulations have been performed with kinetic electrons with realistic electron/ion mass ratio. Interpolating formulae for the GAM frequency and damping rate, based on the results of the gyrokinetic simulations, have been derived. Using these expressions, the influence of the temperature gradient on the damping rate is also investigated. Finally, the results are applied to the study of a real discharge of the ASDEX Upgrade tokamak.

References in corpus (4)

• Zonal Flows and Electromagnetic Drift Wave Turbulence
• Second order Gyrokinetic theory for Particle-In-Cell codes
• Cross-code gyrokinetic verification and benchmark on the linear collisionless dynamics of the geodesic acoustic mode
• Decay of geodesic acoustic modes due to the combined action of phase mixing and Landau damping

Cited by in corpus (3)

• Nonlinear velocity redistribution caused by energetic-particle-driven geodesic acoustic modes, mapped with the beam-plasma system
• Effect of temperature anisotropy on the dynamics of geodesic acoustic modes
• Implementation of energy transfer technique in ORB5 to study collisionless wave-particle interactions in phase-space