Formation, evolution, and structure of fronts produced by unsteady injection of highly magnetized, relativistic flows

We study the formation, evolution, and structure of dissipative fronts produced by overtaking collisions of relativistic streams, with emphasis on strongly magnetized flows. The evolution of the system is followed using an analytical approach in the simple-wave regime and numerical simulations in the nonsimple-wave regime, until a steady state is reached. The steady state structure of the front is then examined by solving the appropriate jump conditions. The conversion of magnetic energy into kinetic energy is parameterized in terms of the Alfven 4-velocity inside the front. The implications for gamma-ray jets are briefly discussed.