Multi-scale numerical modelling of black hole accretion and jets

Despite their compact structure, astrophysical black holes play a central role in galaxy dynamics through accreting turbulent gas and launching outflows. Relativistic outflows, called jets, originate near the black hole event horizon and often extend to extra-galactic distances, a length-scale separation exceeding ten orders of magnitude. Properly addressing the nature of black hole systems requires a simulation that includes general relativistic effects on the gas flow in the near-black hole region, and resolves both the small-scale disk turbulence and larger-scale jet-environment interactions. By far, general relativistic magneto-hydrodynamics (GRMHD) simulations are the most popular numerical tool that incorporates all of the effects above. For this thesis, I co-developed the first GPU-accelerated GRMHD code H-AMR that provides the necessary computational speed-up and resolution to create some of the most detailed multi-scale simulations of black hole jets. This thesis focuses on the disk and jet morphology of two of the best-studied supermassive black holes, M87 and Sagittarius A*. With the advent of the Event Horizon Telescope, it is now possible to resolve the horizon-scale structure around supermassive black holes, contributing essential information connected to radio jets, particularly in the case of M87. I explore the multi-wavelength flux and image variability introduced by the general relativistic warping of jets in the context of M87 and particle acceleration in Sagittarius A*. Guided by observational constraints, the GRMHD simulations put forth in this thesis provide an attractive first-principles approach towards deciphering the complex physics surrounding black hole accretion and jet launching.