Interplay between accelerated protons, x rays and neutrinos in the corona of NGC 1068: Constraints from kinetic plasma simulations

We examine properties of accelerated protons potentially responsible for the neutrino excess observed in the direction of NGC 1068, using constraints from kinetic particle-in-cell simulations. We find that (i) coronal x rays and optical/ultraviolet light in the inner disk lead to efficient absorption of hadronic γ rays within 100 Schwarzschild radii from the black hole; (ii) protons accelerated from the coronal thermal pool cannot account for the observed neutrinos; and (iii) explaining the observed signal requires an injection of protons with a hard spectrum, peaking at γp∼103-104, into the turbulent magnetically dominated corona, where they are confined and reaccelerated. The resulting neutrino signal can be consistent with IceCube observations. In our most favorable scenario, the injected protons are preaccelerated in intermittent current sheets in the vicinity of the black hole, occurring either at the boundary between the disk and the outflow or during magnetic flux eruption events.