Nonlinear ponderomotive force by low frequency waves and nonresonant current drive

Abstract

The collisionless nonresonant force by low frequency waves has been thought to be capable of driving the nonresonant current. However, for a single particle, the ponderomotive force is in the direction of the gradient of the wave field energy. For cold plasmas, the Reynolds stress acting on the Lagrangian fluid element fully counteracts the nonresonant force offered by the quasilinear electromagnetic force. For hot plasmas, the collisionless nonresonant force is also cancelled by the nonlinear kinetic stress force. Therefore, in collisionless plasmas, none of the ponderomotive forces by low frequency waves can drive the nonresonant current.