Fast Ion Interaction with Turbulence Mediated by Zonal Flows in Tokamak Plasmas: Overview of the Recent Insights

Abstract Recent findings on improved thermal plasma confinement in the presence of large-scale Alfvén Eigenmodes in tokamak plasmas have sparked a great interest in the complex physics at play, as it is relevant for next-generation fusion device optimization. These studies must be framed within the latest two decades of efforts in analyzing the various mechanisms through which the fast ions, i.e. ions with much larger energy than that of thermal ions, can interact with the background turbulence and, remarkably, reduce or even suppress the latter in magnetized plasmas. This contribution aims at reviewing the latest results about experimental and modeling observation of reduced outward ion heat flux triggered by the nonlinear and multi-scale interplay of fast-ion-driven modes and background turbulence, and framing it within the broad knowledge on the well-established fast-ion mechanisms reducing the tokamak plasma turbulence.