Local wavelength evolution and Landau damping of electrostatic plasma wave driven by an ultra-relativistic electron beam in dense inhomogeneous plasma

Evolution of an electrostatic plasma wave driven by a low-density ultra-relativistic electron beam in dense inhomogeneous plasma is considered. In particular, the wavelength variation as observed at fixed locations in the plasma is analyzed in terms of the wave characteristics. It is shown that for a negative density gradient, the observed local wavelength decreases monotonically with time, but for a positive density gradient, it first increases and then decreases with time, accompanied by reversal of the wave phase. However, in both cases the local wavelength eventually decreases with time since Landau damping becomes significant as the wavelength becomes of the order of the plasma Debye length. Results from particle-in-cell simulations agree well with theoretical analyses of the wavelength variation.

An exact solution to paraxial propagation of laser beams in longitudinal inhomogeneous plasmas

An exact, general solution for laser beams propagating in longitudinally inhomogeneous plasmas is obtained in the form of the diffraction integral. The Gaussian beam and the Hermite-Gaussian beam are taken for example. In the case of an increasing plasma density along the propagation distance, natural diffraction of the Gaussian beam is retarded. This retardance has a less effect on the central part of the Hermite-Gaussian beam while a considerable rise of the power in bucket （PIB） occurs in the surrounding part of the beam.

Wakefield generation by chirped super-Gaussian laser pulse in inhomogeneous plasma

We study the effect of nonlinearly chirped super-Gaussian （SG） laser pulse on wakefield generation in an inhomogeneous plasma. The different types of nonlinearly chirped pulse are employed, and different kinds of inhomogeneous plasma density are used. The maximum wakefield amplitude as the function of nonlinearly chirped laser pulse and inhomogeneous plasma density in parameter space are obtained. Moreover, the dependence of the maximum wakefield amplitude on the SG laser pulse index is discussed. This shows that a larger wakefield can be obtained when the chirped pulse and inhomogeneous density are in the critical regions. Wakefield generation can be controlled by adjusting the chirped SG pulse and inhomogeneous plasma density parameters. That is, we provide an efficient way for the controlled generation of the wakefield.

Analysis of Landau damping in radially inhomogeneous plasma column

The Landau damping behavior in a cylindrical inhomogeneous warm magnetized plasma waveguide has been studied.The radial inhomogeneity for different characteristic lengths（L0） with strong spatial dispersion has been taken into account.The analyses have been considered for two limits ωce 〈 ωpe and ωce 〉 ωpe. Due to the radial inhomogeneity of the plasma, all essential equations for studying the Landau damping are calculated in the Bessel–Furrier and differential Bessel–Furrier expansions. The dependence of Landau damping on the inhomogeneity, temperature and external magnetic field for electrostatic modes is scrutinized and described in detail through numerical calculations. The associated numerical results are presented and discussed.

The multi-peak point phenomenon of broadband microwave reflection caused by inhomogeneous plasma

During spacecraft re-entry,the challenge of measuring plasma sheath parameters directly contributes to difficulties in addressing communication blackout.In this work,we have discovered a phenomenon of multiple peaks in reflection data caused by the inhomogeneous plasma.Simulation results show that the multi-peak points fade away as the characteristic frequency is approached,resembling a series of gradually decreasing peaks.The positions and quantities of these points are positively correlated with electron density,yet they show no relation to collision frequency.This phenomenon is of significant reference value for future studies on the spatial distribution of plasmas,particularly for using microwave reflection signals in diagnosing the plasma sheath.

FDTD Analysis of Reflection of Electromagnetic Wave From a Conductive Plane Covered with Inhomogeneous Time-Varying Plasma

A finite-difference time-domain (FDTD) algorithm is applied to study the electromagnetic reflection of conduction plane covered with inhomogeneous time-varying plasma, homogeneous plasma and inhomogeneous plasma. The collision frequency of plasma is a function of electron density and plasma temperature. The number density profile follows a parabolic function. A discussion on the effect of various plasma parameters on the reflection coefficient is presented. Under the one-dimensional case, transient electromagnetic propagation through various plasmas has been obtained, and the reflection coefficients of EM wave through various plasmas are calculated under different conditions. The results illustrate that a plasma cloaking system can successfully absorb the incident EM wave.

FDTD Simulation of Bistatic Scattering by Conductive Cylinder Covered with Inhomogeneous Time-Varying Plasma

A finite-different time-domain （FDTD） algorithm is applied in this paper to study the bistatic electromagnetic（EM） scattering by a conductive cylinder covered with inhomogeneous, collision, cold, time-varying plasma. The collision frequency of plasma is a function of the electron density and the pressure of the background gas. The plasma density follows any prescribed distribution function of the rise time of plasma and the radius of the column. The bistatic radar cross section （RCS） of the conductive cylinder covered with inhomogeneous time-varying plasma and inhomogeneous steady-state plasma is calculated under different conditions. The results illustrate that a plasma cloaking system can successfully reduce the RCS of the conductive cylinder.

Absolute and Convective Instabilities of Two-Plasmon Decay in an Inhomogeneous Magnetized Plasma

Three-wave resonant parametric decay instability of extraordinary wave decay into two upper hybrid waves in an inhomogeneous plasma is studied theoretically. Analytical expressions of the local absolute growth rate, convective amplification factor and threshold intensity are obtained. The calculated results show that the effects of magnetic field and ky （ICy is the component of the wavenumber of upper hybrid wave perpendicular to pump wave k0） on the growth rate, amplification factor and threshold intensity are extremely dependent on their strength. The absolute growth rate and convective amplification factor increase with the plasma density while the threshold decreases. Moreover, the expression indicates that the inhomogeneity scale length of density and linear damping will reduce the convective amplification factor.

Dynamics of laser beams in inhomogeneous electron positron ion plasmas

Nonlinear interaction of laser and electron–positron–ion plasmas is investigated by invoking the variational principle and numerical simulation, in terms of a nonlinear Schrodinger equation with inhomogeneities effect. It is shown that the plasma inhomogeneity has great influence on the laser beam dynamics. The laser beam can be self-trapped, focused, or defocused depending on the inhomogeneity character. The linearly decreasing axial plasma density makes the laser beam defocus, while the linearly increasing axial plasma density results in self-trapping of the beam. The self-focusing of the trapped beam is found in a high-density region. For the Gaussian types of density distribution, the beam field submits nonlinearly oscillating regime. The results provide an efficient way to manipulate the dynamics of laser beam propagating in plasma.

Inhomogeneous Dielectric Target Properties for Increased Non-thermal Pressure in Laser Boron Fusion by CPA-Pulses

Based on the documentation of the invited paper and the subsequent discussion at a virtual conference,discoveries are indicated,which are summarized in the following paper for further evaluation on the topic of non-thermal forces using terms of extremely powerful components of Maxwell’s stress tensor at the interaction of CPA(chirped pulse amplification)laser pulses in the fusion plasmas of hydrogen with the isotope 11 of boron.This is caused by a recoil mechanism given by the Fresnel formulas of the suppression of the reflectivity of inhomogeneous plasma given by optical constants of the plasma properties.

Propagation of Nonlinear Solitary Waves in Nonuniform Dusty Plasmas with Two-Ion Temperature

The nonlinear properties of dust acoustic solitary waves in inhomogeneous dusty plasmas with two-ion temperature are investigated. By using the reductive perturbation theory, a modified variable coefficients Korteweg-de Vries （MKdV） equation is derived. The typical integral form of the Sagdeev potential is examined numerically. The numerical results show that the inhomogeneity, the two-ion temperature have strong influence on the nonlinear properties of dust acoustic solitary waves.