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 will argue that relativistic magnetic reconnection — where the magnetic energy of annihilating field lines is even larger than the particle rest mass energy — 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.

BIO
Lorenzo Sironi is an associate professor in the Department of Astronomy at Columbia University, where he works on a variety of plasma processes relevant to both space physics and astronomy. He became passionate about plasmas and astronomy in Pisa, before moving to the Department of Astrophysical Sciences at Princeton for his PhD, awarded in 2011. Since then, he has been a NASA Einstein Fellow at Harvard, and he moved to Columbia in 2016, where he has nurtured a lively research group in high-energy plasma astrophysics. He was awarded the 2019 Sloan Fellowship in Physics and the 2020 Cottrell Scholar Award. His research group investigates the plasma physics of shocks, magnetic reconnection and turbulence in order to explain from first principles the observations of a wide variety of astrophysical sources, especially those whose extreme conditions cannot be currently probed in the laboratory.