Stimulated Raman forward scattering (SRFS) of an intense X-mode laser pump in a preformed parabolic plasma density profile is investigated. The laser pump excites a plasma wave and one/two electromagnetic sideband waves. In Raman forward scattering, the growth rate of the parametric instability scales as two-third powers of the pump amplitude and increases linearly with cyclotron frequency.

The propagation of intense laser pulses in plasma [

Stimulated Raman scattering (SRS) is an important parametric instability in plasmas. In stimulated Raman forward scattering (SRFS), a high phase velocity Langmuir wave is produced that can accelerate electrons to high energy [

Liu et al. [

In this paper, we examine the SRFS of an X-mode laser pump in a magnetized plasma channel including nonlocal effects. In many experiments in high-power laser-plasma interaction, transverse magnetic fields are self-generated [

The ponderomotive force due to the front of laser pulse pushes the electrons radially outward on the time scale of a plasma period

In Section

Consider a two-dimensional plasma channel with a parabolic density profile immersed in a static magnetic field

Schematic of excitation of a Langmuir wave and two sidebands by an X-mode laser in a plasma channel.

The plasma permittivity at

The local dispersion relation of the mode is given by

Equation (

Define

Equation (

The eigenvalue for the fundamental mode is

The pump wave produces oscillatory electron velocity,

The sideband waves couple with the pump to exert a ponderomotive force on electrons at

For

The drift velocity of plasma electrons due to electrostatic wave of potential

The nonlinear velocity

Using the equation of continuity, the linear and nonlinear density perturbations at

Using these in Poisson’s equation,

The nonlinear current densities at the sidebands can be written as

Using equation (

Equations (

We solve equations (

Corresponding eigenvalues are

This nonlinear dispersion relation is a function of the DC magnetic field. The dispersion relation is modified if one changes the value of the DC magnetic field. In the absence of the DC magnetic field,

Taylor expanding

Equation (

We substitute the value of

Equation (

For

In Figure

Normalized growth rate as a function of normalized amplitude of the pump wave in Raman forward scattering for

Normalized growth rate as a function of normalized cyclotron frequency for

The plasma channel with a parabolic density profile localizes the electromagnetic eigenmodes involved in the SRFS process within a width of the order

In the earlier work by Liu et al. [

The data used to support the findings of this study are available upon request from the authors.

The authors declare that they have no conflicts of interest.