Radiative Relativistic Reconnection

Relativistic jets of blazars and magnetized coronae of highly accreting black holes routinely display non-thermal emission signatures, including fast and bright flares of high-energy emission. Yet, the “engine” responsible for accelerating the emitting particles to ultra-relativistic energies is still unknown. With fully-kinetic particle-in-cell (PIC) simulations, we study the physics of relativistic magnetic reconnection — where the magnetic energy of annihilating field lines is even larger than the particle rest mass energy — in the radiative regime where the particle cooling time is shorter than the lifetime of the system. We show that radiative relativistic reconnection offers an intriguing explanation for (1) high-energy flares in blazar jets, and associated rotations in the optical polarization vector; and (2) the hard-state spectra of black hole X-ray binaries and Active Galactic Nuclei.