A variety of astrophysical phenomena can only be explained as being powered by black holes. In particular, accreting supermassive black holes are responsible for launching relativistic plasma jets and for accelerating ultra energetic particles. The mechanism that channels energy from the black hole to the particles remains a mystery.

Observations have come to help lately. The Event Horizon Telescope collaboration has been able to image the shadow of the supermassive black hole M87*, probing the magnetic structure almost down to the event horizon. The GRAVITY collaboration detected a hot spot in infrared orbiting Sgr A*, indicating the presence of a large scale poloidal magnetic field. These observations give new clues to constrain theoretical models that are able to explain jets and particle acceleration.

This problem involves complex interactions between collisionless plasma dynamics in high gravitational field, and pair creation due to the interaction of energetic particles with surrounding photons from the accretion flow. Only kinetic simulations can capture all these effects.

In this seminar, I will present General Relativistic Radiative Particle-in-Cell simulations of an axisymmetric black-hole magnetosphere, which include self-consistent plasma supply and radiative processes. I will put the emphasis on extracting synthetic observables from these simulations, such as gamma-ray lightcurves and millimeter images, which can directly be compared to actual observations. This allows us to model very accurately the non-thermal radiation emitted from the innermost regions of black-hole magnetospheres.