Magnetic instability by the relativistic laser pulses in overdense plasmas

The magnetic instability driven by the relativistic electron stream generat ed by ultra-intense laser is investigated with the help of a two-dimensiona l particle-in-cell simulation, which includes the relativistic binary colli sion. The linear growth rate of the instability is also studied using the t wo-stream fluid model, which consists of a fast electron current and a retu rn current. The growth rate is evaluated numerically from the linearized eq uations of the electron fluids with the Maxwell equations. The kinetic effe cts of electrons on the magnetic instability are found to reduce the growth rate. The growth rate is maximum at the wavelength near the plasma skin le ngth because of the plasma kinetic effect. When the initial plasma temperat ure is high, the growth rates of shorter wavelengths are significantly redu ced. In the collisional plasma, the growth rates of modes whose wavelength is shorter than the plasma skin length are suppressed and the spectral peak of the growth rate shifts to long wavelength modes. It is found that the r esults of the linear analysis agree well with two-dimensional particle simu lation results in the early stage. (C) 2000 American Institute of Physics. [S1070-664X(00)05002-3].