1 Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou, P.R.C. 2 Associazione Euratom-ENEA sulla Fusione, C.P. 65 - I-00044 - Frascati, Italy 3 Dept. of Physics and Astronomy, Univ. of California, Irvine CA 92697-4575, U.S.A.
Funds: This work is supported by the Euratom Communities under the contract of Association between EURATOM/ENEA, USDoE GRANTS and the National Basic Research Program of China and ITER-CN under Grant No.2009GB105005. One of the authors (Z.Q.), undertook part of this work with the support of the “ICTP programme for Training and Research in Italian Laboratories, Trieste, Italy”.
Geodesic Acoustic Modes (GAMs) are oscillating zonal mode structures unique to toroidal plasmas and are capable of regulating microscopic turbulence and associated transports. In this paper, we investigate three important aspects of GAM dynamics: (1) GAM continuous spectrum and its mode conversion to kinetic GAM (KGAM); (2) linear excitation of energetic particle induced GAM (EGAM) and its coupling to the GAM continuum, and (3) nonlinear saturation of EGAM via wave particle trapping. The analogy between the GAM-EGAM dynamics and the well known beam-plasma instability is also discussed.
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