First-principles simulations of collisionless accretion onto black holes: dynamics and flares

Accretion flows onto primary targets of the Event Horizon Telescope, M87* and SgrA*, consist of collisionless plasmas. It is yet unknown how microphysical instabilities in these plasmas affect the dynamics of the flow, and how non-thermal particles are produced during observed spectacular multi-wavelength flares. In this talk I will show results of first-principles two-dimensional general-relativistic particle-in-cell simulations which address these fundamental questions. Large separation of microscopic (ion gyroradius) and macroscopic (black hole event horizon) scales in the simulation allows to probe the importance of mirror and firehose instabilities during the quiescent accretion, as well as the dynamics of magnetic reconnection and creation of electron-positron pair plasma in the flaring state.