Kinetic damping of radially localized kinetic toroidal Alfvén eigenmodes in tokamak plasmas

Abstract

A global eigenvalue solver code is used to analyze the kinetic damping of radially localized kinetic toroidal Alfvén eigenmodes (KTAEs). By including the finite-Larmor-radius effects of ions, KTAEs are found in the Alfvén continuum well above the upper boundary of the TAE gap. The numerical calculations reveal that the real frequency and the kinetic damping of the KTAEs increase with increasing ion Larmor radius, with the ion-Larmor-radius effect intensifying for KTAEs with higher radial mode number. With increasing plasma β, the real frequency of the KTAEs increases whereas the damping rate remains almost constant. At an intermediate plasma β, the real frequencies, damping rates, and mode structures of each pair of KTAEs with radial mode numbers p and p + 1 merge into each other. The damping of KTAEs with lower radial mode number remains unchanged with the tokamak aspect ratio, whereas it increases for KTAEs with higher radial mode number. The KTAEs have lower kinetic damping and a broader mode structure near the core region of a tokamak having a flat core q equilibrium.