Bifurcation and Lorentz-factor scaling of relativistic magnetized plasma expansion.

We report the long-term results of 2 1/2-dimensional particle-in-cell simulations of the relativistic expansion of strongly magnetized electron-positron plasmas. When the simulation is carried to >150 light-crossing time of the initial plasma, the plasma pulse exhibits a number of remarkable properties. These include the repeated bifurcation of the pulse profile, development of a power-law momentum distribution with low-energy cutoff, and a simple scaling law for the peak Lorentz factor.