SPECTRUM OF FAST ALFVEN EIGENMODES IN A CYLINDRICAL CURRENT-CARRYING PLASMA

In this paper, the spectrum of fast Alfvén eigenmodes is examined for a cylindrical, current-carrying, inhomogeneous plasma, at frequencies above the ion cyclotron frequency. Although the spectrum for m = 0 and m = ±1 modes in a current-free plasma has been studied extensively, the influence of a steady plasma current and the properties of high m modes have not received as much attention. It is shown that there exists a wide spectrum of positive m modes that propagate in the ion cyclotron range of frequencies, regardless of the plasma density or device size. These modes propagate, as surface waves, in the plasma edge region. Mode splitting, caused by the finite plasma current, is sufficiently large in tokamak devices that high m modes propagate in only one direction parallel to the equilibrium Bz field. High m modes are guided along the steady magnetic field lines in the plasma edge and are therefore potentially very dangerous from an edge heating point of view. © 1990 American Institute of Physics.