Effect of elongation on energetic particle-induced geodesic acoustic mode

Abstract

The effect of the plasma elongation on the energetic-particle-induced geodesic acoustic mode (EGAM) dynamics is studied with numerical simulations performed with the gyrokinetic codes GENE and ORB5 and assessed with analytical models. The former code has been recently extended to support non-Maxwellian distribution functions and for the first time global results are shown here and benchmarked against the code ORB5. Taking advantage of these recent developments in GENE, which allow a joint investigation with ORB5, linear electrostatic simulations with adiabatic electrons have been performed. The impact of the elongation on the EGAM dynamics and excitation mechanism is investigated through the study of the energy exchange terms between the particle and the mode for different plasma geometry. Finally, the results are applied to the study of an ASDEX Upgrade discharge with strongly elongated plasma employing realistic density and temperature profiles.