On Kinetic Cavitions By Relativistic Laser

With the increase of laser intensity, the development of laser inertial confusion technology and the progress of laser astrophysics experiment, there is increasing interest on relativistic laser plasma interaction. Theoretical investigation on relativistic laser plasmas and the interaction of laser pulse with electron-positron plasmas is conducive to the realization of laser inertial confusion and the development of laser astrophysics experiment.Firstly, from the governing equations for self-generated magnetic field in relativistic laser plasma interactions, which are obtained by Li Xiao-Qing et al., the dispersion equation for transverse perturbation is obtained by small perturbation method. The analytical solution for the maximum growth rate and the corresponding characteristic scale of spontaneous magnetic field is derived under given conditions within the framework of the dispersion equation. Concerning the complexity of the dispersion equation, the numerical calculations are performed. The numerical results are consistent with those obtained from experiment and numerical simulation. In addition, the analytical results are pretty good approximation for numerical ones, thus, one can use them to estimate the scale of spontaneous magnetic field.Secondly, concerning the governing equations for self-generated magnetic field can self-consistently describe the nonlinear evolution of high frequency transverse plasmons, ion acoustic motion and spontaneous magnetic field, the temporal evolution of the envolope of electric field, spontaneous magnetic field and density caviton is given by numerical calculation under static limit. It shows the maximum amplitude for magnetic field is of the order of the laser oscillating magnetic field, and the density depletion would come to 72%. The self-exited magnetic field depends on the intensity and inhomogeneity of the envelope of electric field. The reason why magnetic field is confined in density caviton is due to density caviton captured extremely strong and inhomogeneous transverse plasmons. Such a caviton structure is important for the production of collimated energetic particles.Consequently, the nonlinear governing equations for the interaction of relativistic laser pulse with ultra-relativistic isothermal electron-positron plasmas are obtained on the basis of the kinetic theory for transverse plasmons established by Li Xiao Qing et al. From the governing equation, one can find there will be stable solitary structure when one dimensional linear polarized laser pulse interacts with the ultrarelativistic isothermal electron-positron plasmas. Considering the difference between one dimensional structure and three dimensional one, the modulation instability for three dimensional case is investigated, the maximum growth rate and the corresponding characteristic scale for the envelope electric field are derived. Although there is stable structure in one dimensional case, yet from scale law and virial theorem one can see three dimensional electric field envelope will collapse for modulation instability. During the collapse process, the increase of wave field strength leads to the formation of density caviton with strong localized field. The possibility of creating the structure in the laser electron-positron plasma interactions, and the correlation to the pulsar micro-pulse radiation are discussed.Finally, from the kinetic theory for transverse plasmons established by Li Xiao Qing et al., the nonlinear governing equation for self-generated magnetic field by the interaction of relativistic laser pulse with ultra-relativistic nonisothermal electron-positron plasmas is obtained. Based on the nonlinear equations, the growth rate and characteristic scale for spontaneous magnetic field are obtained from linear analysis. And the possible application of the mechanism to explain the generation of small scale magnetic field in astrophysical environments is proposed.