Relativistic Magnetic Reconnection in High-Energy Astrophysics: Particle Acceleration and Radiation

Mon, April 04, 2016

Many of the most spectacular astrophysical phenomena, in systems like relativistic black-hole jets, gamma-ray bursts, and pulsar wind nebulae, involve intense and rapid flares of high-energy radiation, often exhibiting nonthermal spectra.  Magnetic reconnection — a basic plasma process of rapid magnetic-field rearrangement and associated violent release of magnetic energy — is one of the favored physical mechanisms powering these very energetic events. As I will review in this talk, in the past few years we have seen great progress in both our theoretical understanding of the fundamental physical nature of this process and in our ability to characterize quantitatively the resulting nonthermal particle acceleration and radiation, with important observational implications. These exciting new developments were mostly achieved with first-principles kinetic (e.g., particle-in-cell) simulations of relativistic magnetic reconnection in both pair and electron-ion collisionless plasmas, some of which self-consistently include the synchrotron radiation reaction force and compute the observable radiation signatures. In particular, we now have a firm numerical evidence that reconnection can indeed be an efficient relativistic particle accelerator, but we are also beginning to understand the limitations on the high-energy extent of the resulting power-law particle and photon spectra, including those due to radiation reaction. I will also discuss some intriguing astrophysical implications of these findings.