Particle Acceleration by Electromagnetic-Dominated Outflows.pdf

1 Particle Acceleration by Electromagnetic-Dominated Outflows Edison Liang and Koichi Noguchi, Rice University, Houston TX 77005-1892 ABSTRACT We review recent developments in particle acceleration by Poynting flux using plasma kinetic simulations, and discuss their potential applications to gamma-ray burst phenomenology. 1. INTRODUCTION An outstanding problem in modern astrophysics is the acceleration of high-energy particles The challenge is to find natural, robust mechanisms which efficiently convert electromagnetic, rotation, hydrodynamic, thermal or gravitational energy, into the relativistic kinetic energy of a small number of nonthermal particles. The potential applications of particle acceleration include cosmic rays, high-energy radiation from pulsars, blazars, gamma-ray bursters (GRBs), magnetars/SGRs and black holes (BHs). It has long been speculated that many high-energy astrophysical phenomena (e.g. pulsar winds, GRBs) may be the result of particle acceleration and radiation by electromagnetic (EM)- dominated outflows (“Poynting flux” (Lyutikov and Blandford 2003, Lyutikov and Blackman 2003, Smolsky and Usov 2000)). However, until recently there had been few concrete models of such acceleration as they require large-scale Particle-in-Cell (PIC, (Birdsall and Langdon 1991)) simulations of relativistic collisionless plasmas. Three years ago we embarked on a pioneering study of Poynting flux acceleration (PFA) using 2.5D (2D-space,3-momenta) PIC codes originally developed at LANL (Nishimura et al 2002) and LLNL (Langdon and Lasinski 1976). This led to the discovery of a novel phenomenon called diamagnetic relativistic pulse accelerator (DRPA, (Liang et al 2003), which represents the first explicit demonstration of efficient, robust PFA from first principles plasma kinetics. Since then we have made rapid advances along this path, including the discovery of a fundamental scaling law for the Lorentz factor, long term evolution o