Abstract

Contributed Talk - Splinter NonThermalAccel   (MW-1250)

The dynamics of energetic particles in black hole accretion disks

Daniele Villa, Frank Rieger, James M. Stone, Frank Jenko
Max Planck Institute For Plasma Physics, Princeton University

The Cosmic Ray (CR) spectrum spans over 5 decades in energy, reaching upwards of 1020 eV (orders of magnitude beyond the energies probed at CERN), with several features (e.g. the “knee” or the “ankle”) that are indicative of particles originating from different processes and sources. Understanding such processes would, at once, explain the composition of the CR spectrum, and offer insight into environments and processes we would have otherwise no way of probing. Indeed, the environment surrounding BHs is a prime candidate as a source of high-energy particles, given the extreme physics at play near such objects. In order to provide insight into the matter, a suite of simulations with tracer particles injected into General Relativistic MagnetoHydroDynamic (GRMHD) simulations of accretion disks surrounding BHs has been run. The evolution of the particles includes both general relativistic and electromagnetic effects, with an energy conserving iterative pusher. Varying the accretion regimes and parameters of the system (including BH spin), as well as the injection method and parameters for the particles, we were able to assess how par- ticles interact with the plasma in such extreme environments, with the goal of providing insight into phenomena of relevance for CR acceleration. These global, fully-GR simulations, represent a first-of-a-kind study, and reveal unexpected and impactful phenomena that will be discussed. We demonstrate how particles interact most intensely with the fluid at the funnel-sheath, the region where the plasma transitions from being matter-dominated to magnetically-dominated, and how new processes, that couldn’t be observed without full-GR dynamics, arise, such as particles being reflected multiple times while traveling along the jet in high-spin cases.