Evidence of "Two Plasmon" decay of energetic particle induced geodesic acoustic mode

Abstract

Secondary low frequency mode generation by energetic particle induced geodesic acoustic mode (EGAM) observed in LHD experiment is studied using nonlinear gyrokinetic theory. It is found that the EGAM frequency can be significantly higher than local geodesic acoustic mode (GAM) frequency in low collisionality plasmas, and it can decay into two GAMs as its frequency approaches twice GAM frequency, in a process analogous to the well-known two plasmon decay instability. The condition for this process to occur is also discussed.

arXiv comment14 pages, 2 figs

References in corpus (6)

• Nonlinear dynamics of phase space zonal structures and energetic particle physics in fusion plasmas
• Kinetic theory of geodesic acoustic modes in toroidal plasmas: a brief review
• Nonlinear excitation of geodesic acoustic mode by toroidal Alfvén eigenmodes and impact on plasma performance
• Saturation of energetic-particle-driven geodesic acoustic modes due to wave-particle nonlinearity
• Fast excitation of geodesic acoustic mode by energetic particle beams
• On Zero Frequency Zonal Flow and Second Harmonic Generation by Finite Amplitude Energetic Particle Induced Geodesic Acoustic Mode