Description
Recent experiments on JET [1] and DIII-D [2] suggest that toroidal Alfvén eigenmodes (TAEs) excited by energetic particles (EPs) can mitigate ion-scale turbulence, such as ITG (ion temperature gradient mode), by generating zonal flows that shear turbulence eddies. Using the electromagnetic version of the global gyrokinetic code GYSELA [3,4], we analyse the contribution of polarization, Reynolds stress, Maxwell stress, and geodesic curvature coupling to zonal-flow generation.
For the ITPA-TAE case, the zonal-flow drive is dominated by the thermal geodesic term, while Reynolds and Maxwell stresses grow in the nonlinear phase. In an AUG-like TAE case, the energetic-particle geodesic contribution dominates at saturation, with other terms becoming significant later. These results show that the dominant zonal-flow drive depends on energetic-particle content and nonlinear evolution, helping clarify the AE–zonal-flow coupling mechanism.
[1] S. Mazzi et al., Nature Physics 18, 776 (2022).
[2] X. D. Du et al., Phys. Rev. Lett. 135, 265101 (2025).
[3] V. Grandgirard et al., Computer Physics Communications 207, 35-38 (2016).
[4] Z. S. Qu, et al., Journal of Computational Physics 563, 115070(2025).