Ponderomotive force in a moving warm two-fluid plasma

A microscopic method is used to obtain an expression for the ponderomotive force of high frequency electromagnetic waves in a warm two-fluid collisionless plasma with nonzero fluid velocity. The result contains new terms which explicitly depend on the fluid velocity and its gradients, in addition to the familiar expressions of earlier studies. It is shown that the new terms are of the same order as the Abraham force in the smallness parameter that measures the magnitude of the flow velocity of the plasma relative to the phase velocity of the wave. The stress tensor and the momentum density vector are also derived from the newly found ponderomotive force. (C) 2000 American Institute of Physics. [S1070-664X(00)00502-4].