Non-linear cross modulation of electromagnetic waves in a plasma due to time-dependent electron density

Abstract

Expressions are derived for the time-dependent components of the electron density in a plasma subjected to an amplitude-modulated electric vector by assuming the electron density to follow the time-dependent (at modulation frequency) instantaneous changes in the electron temperature. These expressions for the time-dependent components in the electron density have been used to investigate the various time-dependent components of the current density when another weak wave of frequency ω1 is also propagating in the plasma; this expression for the current density is substituted in the appropriate wave equation and the solutions have been used to study the change in modulation of the strong wave (ω) and the cross modulation of the weak wave (ω1) when they are reflected from a plasma-free-space interface, the wave being normally incident on it from the free space side. Some numerical calculations have been carried out for the dependence of change in modulation and cross modulation in the reflected wave on relevant parameters by assuming the electron density to be governed by Saha's equation corresponding to the electron temperature; these results are presented in the form of tables.