Collisionless Accretion of Finite-Angular-Momentum Plasma onto a Spinning Black Hole

In low-luminosity active galactic nuclei like M87* and Sgr A*, the accretion disk around the central supermassive black hole is tenuous and collisionless. As a result, the usual ideal magnetohydrodynamics approximation may not be applicable. In this Letter, we report on the first fully kinetic simulations of the accretion process where the plasma initially has finite angular momentum, focusing on the case of axisymmetry. The simulated accretion flow behaves remarkably similarly to the magnetically arrested disk regime of ideal magnetohydrodynamics, reproducing episodes of magnetic flux saturation and eruption typical of magnetically arrested disks. The resemblance to fluid models owes largely to kinetic instabilities, which regulate pressure anisotropy in the disk, allowing fluid terms to dominate the angular momentum transfer. In addition, by handling vacuum regions effectively, our kinetic approach probes the matter supply to the jet funnel. We observe no efficient penetration of the accreting material into this region, suggesting that a pair discharge may be required to sustain the Blandford-Znajek process. These initial findings represent important groundwork to be checked and built upon by future kinetic accretion simulations, especially in 3D.