Inertia and ion Landau damping of low-frequency magnetohydrodynamical modes in tokamaks

The inertia and Landau damping of low-frequency magnetohydrodynamical modes are investigated using the drift-kinetic energy principle for the motion along the magnetic field. Toroidal trapping of the ions decreases the Landau damping and increases the inertia for frequencies below (r/R) ^1/2v _thi / qR. The theory is applied to toroidicity-induced Alfvén eigenmodes and to resistive wall modes in rotating plasmas. An explanation of the beta-induced Alfvén eigenmode is given in terms of the Pfirsch-Schlüter-like enhancement of inertia at low frequency. The toroidal inertia enhancement also increases the effects of plasma rotation on resistive wall modes.