Large amplitude ion-acoustic solitons are investigated in a plasma consisting of warm adiabatic positive and negative-ions and hot superthermal electrons having kappa distributions. Using Pseudo-potential method an energy integral equation is derived for the system. The latter is analysed to examine the existence regions of the solitary waves. It is found that negative ion concentration (α), spectral index (k) and ionic temperature ratio (σ1 or σ2) significantly influence the characteristic of the solitons. Our numerical analysis shows that the system also supports rarefactive solitons for some selected set of plasma parameters. It is also found that large amplitude ion-acoustic compressive and rarefactive solitons exist simultaneously for the same values of plasma parameters. Further an increase in the superthermality (i.e. decreasing the value of spectral index k) leads to shrinking the existing domain of the large amplitude ion-acoustic solitons. The amplitude of the compressive/rarefactive solitons increases with the increase in negative ion concentration (α). Whereas, on increasing ionic temperature ratio (σ1 or σ2) the amplitude of the compressive/rarefactive soliton decreases. The effect of negative-ion concentration (α), temperature ratio of two ion species (σ1 and σ2), Mach number (M) and spectral index (k) on the characteristics of solitons are discussed in detail. The results of the present investigation may be helpful to understand the nonlinear ion-acoustic solitary waves in space plasma and laboratory plasmas, where two distinct groups of ions and non-Boltzmann distribution electrons are present.

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In this paper we have discussed the consequence of superthermal electrons and negative ion concentration on the arbitrary amplitude ion-acoustic double layers (IA-DLs) for plasma comprising the hot negative and positive ions with kappa distribution electrons. The energy equation is deduced for ion acoustic waves using Pseudo potential technique. We have investigated different parametric regimes for the existence of rarefactive and compressive ion acoustic DLs. The existence of double layers in term of minimum and maximum Mach number has calculated numerically. The effect of spectral index k on the amplitude of DLs and depth of Sagdeev potential has been discussed in detail. From numerical analysis, it is found that the compressive DLs exist at low values of α and rarefactive double layer exist at higher values of α. On the other hand, the effect of ionic temperature ratio (σ 1 and σ 2) plays significant role for the formation of double layer. Our analytical work also shows that the system supports coexistence of compressive and rarefactive DLs. It is also observed that the mass ratio μ affect the basic properties of DLs. We expect that the present results may be used to explain the ion-acoustic double layer in space plasma, where two ionic species and superthermal electrons are observed NO52.35g.

The third harmonic generation of a self organized nonlinear laser Eigen mode of a two-dimensional plasma channel with complete electron evacuation from the inner region is investigated. The nonlinearities arise through the ponderomotive force and relativistic mass variations, while the ions are taken to be immobile. The second harmonic ponderomotive force produces electron density oscillations that beat with the oscillatory velocity due to the laser Eigen mode to create a nonlinear current, driving the third harmonic. As a0 increases up to the threshold value amin, at which complete electron evacuation begins in the inner region, the third harmonic amplitude rises rapidly. Above the threshold, as a0 increases, the width of the inner region where there is no third harmonic current, increases and third harmonic amplitude rises less rapidly. The conversion efficiency is found to be in reasonable agreement with the experimental results.

A model of bubble regime electron acceleration by an intense laser pulse in non uniform plasma channel is developed. The plasma electrons at the front of the pulse and slightly off the laser axis in the plasma channel, experience axial and radial ponderomotive and space charge forces, creating an electron evacuated non uniform ion bubble. The expelled electrons travel along the surface of the bubble and reach the stagnation point, forming an electron sphere of radius re. The electrons of this sphere are pulled into the ion bubble and are accelerated to high energies. The Lorentz boosted frame enabled us to calculate energy gain of a test electron inside the bubble.