title: Alfvén acoustic channel for ion energy in high-beta tokamak plasmas.
abstract: When the plasma beta (ratio of thermal to magnetic pressure) in the core of a tokamak is raised to values of several percent, as required for a thermonuclear fusion reactor, continuous spectra of long-wavelength slow magnetosonic waves enter the frequency band occupied by continuous spectra of shear Alfvén waves. It is found that these two branches can couple strongly, so that Alfvén modes that are resonantly driven by suprathermal ions transfer some of their energy to sound waves. Since sound waves are heavily damped by thermal ion Landau resonances, these results reveal a new energy channel that contributes to the damping of Alfvénic instabilities and the noncollisional heating of bulk ions, with potentially important consequences for confinement and fusion performance.
authors.affiliation: Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212, Japan.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bierwage
authors.affiliation: Japan Atomic Energy Agency, Rokkasho, Aomori 039-3212, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Aiba
authors.affiliation: Japan Atomic Energy Agency, Naka, Ibaraki 311-0193, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Shinohara