Conversion of longitudinal waves into electromagnetic radiation in a slowly varying plasma under W.K.B. approximation

This paper investigates the conversion of a dispersive longitudinal oscillation into reflected and transmitted electromagnetic radiation fields in slowly varying unmagnetized warm fluid plasmas, using W.K.B. approximations. The expressions for the power of the transmitted and reflected electromagnetic radiations, generated by electron acoustic waves, have also been obtained. It is shown that this conversion process becomes most efficient under certain conditions.

Nomenclature

In § 2 H magnetic field - H ₁ - u electron fluid velocity - k _t wave number of the transverse wave - k ₁ wave number of the longitudinal wave in electron fluid - m electronic mass - N ₀ number density of electrons in the unperturbed state - N perturbation in the electron number density - p perturbation in the electron fluid pressure - v _e adiabatic sound velocity of the electron fluid - K _t ² c ^{2 2}–e² - K ₁ ² v _e ^{2 2}–e² - wave frequency - _e electron plasma frequency - 1– _e ² / ² - c velocity of light in vacuum In § 3 K ₀ wave number in the 0X direction - K ₁ ² K ₁ ² –K ₀ ² - K ₂ ² K _t ² –K ₀ ² - K ₃ K ₁–K ₂ - K ₄ K ₁+K ₂ - K ₅ (K ₁ K ₂)^1/2 See Appendix A - A ₁ pressure amplitude of the reflected part of the incident wave - B ₁ pressure amplitude of the transmitted part of the incident wave - L characteristic length of variation ofN ₀ - e _x unit vector along 0X - e _z unit vector along 0Z In § 4 S _t Poynting flux of the transverse electromagnetic radiation - S _tZ ^/t Average of the transmitted part of the poynting flux along 0Z over the time period 2/ - S _tZ ^/r Average of the reflected part of the poynting flux along 0Z over the time period 2/ In § 5 S ₁ Energy flux carried by the longitudinal pressure wave - S _1Z ^/t Average of the transmitted part ofS ₁ along 0Z over the time period 2/