Spontaneous nonlinear excitation of geodesic acoustic mode (GAM) by toroidal Alfvén eigenmodes (TAE) is studied within the framework of gyrokinetic theory. The dispersion relation for the parametric decays of a pump TAE mode into a TAE lower sideband and a GAM is derived. It is shown that, in the ideal MHD first stability region, the condition for spontaneous excitation of GAM by TAEs is ω2 0 > V2 A/(4q2R2 0), in which, ω0 is the pump TAE real frequency, V A is the Alfvén speed, q is the safety factor and R0 is the torus major radius. The corresponding threshold condition is also derived and suggests the decay process as an effective saturation mechanism for TAE. © Copyright EPLA, 2013.
|Titolo:||Spontaneous excitation of geodesic acoustic mode by toroidal Alfvén eigenmodes|
|Data di pubblicazione:||2013|
|Appare nelle tipologie:||1.1 Articolo in rivista|