Study On Modulational Instability And Electron Beam Jets In Laser-plasma

With the rapid development of laser technology,the interaction of laser plasma has become one of the most popular research fields.When the laser is incident on the coronal region,it is absorbed,reflected and scattered by the plasma,and a variety of nonlinear effects will occur near the coronal region.These effects have an important impact on the propagation of the laser in the plasma.In this paper,the instability and collimated electron beam jet generated near the critical plane of the laser plasma will be studied.Fast,based on the full Zakharov equations,the dispersion relation of the wave-wave interaction by strong Langmuir waves in nonextensive plasma is obtained.Dispersion equations are analysed with numerical method and the results indicate that both the characteristic wavelength range and maximum growth rate of the modulational instability by strong Langmuir waves will enhance with the nonextensive parameter q increasing.Moreover,an analytic study of dispersion equations in two special and important cases,the modulation instability induced by transverse perturbations and longitudinal perturbations,is presented.The analytic shows that the growth rate induced by transverse perturbations and that done by longitudinal perturbations are equal when the nonextensive parameter q is the same.Comparison of the calculated modulational instability with the corresponding analytical solutions shows that they are in good agreement.This research provides a clearer physical picture of the modulational instability in nonextensive plasma.Then,originally this behavior of the self-generated magnetic fields can be described by a set of nonlinear equations.with respect to small disturbances with limited amplitude,the equilibrium states are not stable in Lyapunov sense,leading to enhancements of the electric field and the circular field in local region;the ponderomotive force from the enhanced electric field repulses a material and forms coronal area with a low density;at the same time,the contraction of the magnetic field,because of the freezing effect,make the material escape along the axial region and form collimated plasma beam jets.This theory is similar to the results observed in the laser-generated plasma experiment,and provides a theoretical basis for collimating high-energy particle beam sources and experimental astrophysics.