Kinetic theory of geodesic acoustic modes in toroidal plasmas: a brief review

Abstract

Geodesic acoustic modes (GAM) are oscillating zonal structures unique to toroidal plasmas, and have been extensively studied in the past decades due to their potential capabilities of regulating microscopic turbulences and associated anomalous transport. This article reviews linear and nonlinear theories of GAM; with emphases on kinetic treatment, system nonuniformity and realistic magnetic geometry, in order to reflect the realistic experimental conditions. Specifically, in the linear physics, the resonant wave-particle interactions are discussed, with the application to resonant excitation by energetic particles (EPs). The theory of EP-induced GAM (EGAM) is applied to realistic devices for the interpretation of experimental observations, and global effects due to coupling to GAM continuum are also discussed. Meanwhile, in the nonlinear physics, the spontaneous GAM excitation by microscale turbulences is reviewed, including the effects of various system nonuniformities. A unified theoretical framework of GAM/EGAM is then constructed based on our present understandings. The first-principle-based GAM/EGAM theories reviewed here, thus, provide the tools needed for the understanding and interpretation of experimental/numerical results.

arXiv commentSubmitted to Plasma Science and Technology. 27 pages, 19 figures

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Cited by in corpus (8)

• Nonlinear dynamics of energetic-particle driven geodesic acoustic modes in ASDEX Upgrade
• Nonlinear velocity redistribution caused by energetic-particle-driven geodesic acoustic modes, mapped with the beam-plasma system
• Soliton generation and drift wave turbulence spreading via geodesic acoustic mode excitation
• Predicting the Z-pinch Dimits shift through gyrokinetic tertiary instability analysis of the entropy mode
• Evidence of "Two Plasmon" decay of energetic particle induced geodesic acoustic mode
• Implementation of energy transfer technique in ORB5 to study collisionless wave-particle interactions in phase-space
• Analytical study on magnetic component of geodesic acoustic mode
• The enhanced soliton propagation and energy transfer in the coupled drift wave and energetic-particle-induced geodesic acoustic mode system