Repeated Bifurcation of Relativistic Magnetic Pulse and Cosmic Gamma-Ray Bursts

The diverse and complex light curves of gamma-ray bursts (GRBs) remain an outstanding astrophysical mystery. Here we report the results of 2-1/2-dimensional particle-in-cell (PIC) simulations of the relativistic expansion of magnetized electron-positron plasmas. When the simulation is carried to >150 light-crossing time of the initial plasma, the plasma pulse reproduces many of the GRB features. Remarkably, the plasma pulse bifurcates repeatedly, leading to a complex, multi-peak structure at late times, resembling GRB profiles.