Low frequency limit of X-mode in non-uniform space and bounded laboratory plasmas

Abstract

It is pointed out that the high frequency extraordinary wave in a non-uniform density plasma contains a low frequency drift type mode which may couple with lower hybrid oscillations in the low-Z material plasmas. In the limit ω2≪ωpe2,Ωe2,c2k2 (where ωpe is the electron plasma frequency, Ωe is electron gyrofrequency, and c is the speed of light), the X-mode becomes a hybrid frequency wave Ωi < ω < Ωe (where Ωi is the ion gyrofrequency) in a pure electron plasma. This partially longitudinal/partially transverse wave is important in the plasmas of heavier atoms/molecules. In hydrogen plasmas, this wave couples with the lower hybrid frequency ωLH = (ΩeΩi)1/2. Several waves in the range of lower hybrid frequency are analyzed. Since heavier ion plasmas have been produced in cylindrical devices initially, therefore the dynamics of these modes in a cylindrically bounded plasma are also discussed.