Simulation studies of energetic particle-induced geodesic acoustic mode, using a full-f electrostatic gyrokinetics

Miki, Kazuhiro; Idomura, Yasuhiro   

Studies of modes driven by energetic particles are of critical importance in burning plasmas. Experimental studies showed that the energetic particle could excite a zonal flow with having a finite frequency, i.e. EGAM. The EGAM exhibits a different frequency from that in the standard geodesic acoustic mode (GAM). A recent electrostatic gyrokinetic simulation showed a possible reproduction of the EGAM interacting with turbulence. Now, using the full-f gyrokinetic simulation code (GT5D), we would promote a study of the EGAM interacting with turbulence. As a first step, we investigate linear properties of the EGAM. Applying an initial particle distribution consisting of the bulk and beam ones, we can reproduce the excitation of the EGAM. The observed EGAM have about a half frequency of that in the standard GAM. The EGAM is excited by an amount of beam density exceeding about 10% of the bulk one. The observed threshold is consistent with theory.