MAGNETIC-FIELD GENERATION DURING THE COLLISION OF ELECTRON-ION PLASMACLOUDS

We present the results of analytical studies and computer simulations of electron-ion plasma cloud collisions using 2D3V particle-in-cell an d 2D two-fluid collisionless relativistic codes. We address the proble m covering the generation of a quasistatic magnetic field. Using relat ivistic two-fluid equations for the two counterstreaming electron popu lations: we show with the help of linear theory that the generation of a magnetic field can be associated with the ''electromagnetic counter streaming instability''. Two-dimensional (2D) particle-in-cell provide good agreement with the results of linear theory. We show that the qu asistatic magnetic field undergoes a collisionless change of structure , leading to large-scale, long-lived structures. These processes may b e important for the understanding of magnetic field generation in lase r plasmas and in space plasmas in the regions where two stellar winds collide.