Convective Instabilities Driven by Electromagnetic Waves

A description of destabilizing effects present in a plasma due to the radio frequency motion of the two species is obtained by expanding the fluid equations and the electromagnetic wave equations in an asymptotic series in 1/ω_rf. Equations for the high‐frequency and low‐frequency motion are separated, linearized, and solved for a plasma with a density gradient perpendicular to a magnetic field. An electromagnetic wave propagating in a direction parallel to the density gradient at a frequency near the lower hybrid is considered. A convenient method of description of the interaction between the electromagnetic wave and the unstable density perturbation involving the simultaneous introduction of more than one phase operator (i) is given. It is found that time average $\overline{{\mathbf{v}}_{\mathrm{rf}}\mathrm{·\nabla }{\mathbf{v}}_{\mathrm{rf}}}$ terms which contain the effects of radio frequency gradient forces lead to instability in qualitative agreement with experiments on electrodeless radio frequency discharges.