Gyrokinetic simulation study on energetic-particle-induced geodesic acoustic mode

Miki, Kazuhiro; Idomura, Yasuhiro   

Understanding of the energetic particles physics is of great interest in the future burning plasmas. We identify linear dynamics of energetic-particle-induced geodesic acoustic mode (EGAM). Representating bump-on-tail distributions as the energetic particles, we calculate real frequencies and linear growth rates, based on eigenmode analyses. Taking into account of finite-orbit-width (FOW) effects, we estimate the reduction of growth rates of the EGAM due to machine size. Results indicate that the reduction is small, within several percent, for experimentally relevant parameters. Next, applying more general distributions, i.e. slowing down, we examine linear evolution of the EGAM. Here the same q-profile is applied as the DIII-D experiments. Results on the gyrokinetic simulations are compared with the hybrid code ones. Obtained frequencies are similar to those obtained from the hybrid one. Linear growth rates are smaller than those obtained from the hybrid one.