Alfvén current drive in magnetic traps

A general approach to the Alfven current-drive problem is developed in this paper. The covariant-form expression for the longitudinal drag force, which can be applied to any magnetic traps (both closed and open), is obtained. For closed magnetic traps, the surface-averaged high-frequency driving force is derived. For axially symmetric tokamaks with an arbitrary transverse cross section, a simple expression for the force is found. It is shown that the magnetohydrodynamic approach can be used to get the oscillating currents on which the time-averaged force depends.