Collisionless Accretion onto Black Holes: Dynamics and Flares.

Phys Rev Lett

Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, New Jersey 08544, USA.

Published: March 2023

AI Article Synopsis

  • The study investigates how collisionless plasma accumulates around a rotating black hole using advanced simulations, comparing results from particle-in-cell and magnetohydrodynamic methods.
  • Key differences were found, including more efficient magnetic reconnection and the rapid acceleration of nonthermal particles in the particle-in-cell simulations, as well as significant deviations from thermal equilibrium in the plasma.
  • The findings have important implications for understanding and modeling observations of black holes like Sgr A* and M87, particularly regarding the behaviors analyzed by the GRAVITY and Event Horizon Telescope collaborations.

Article Abstract

We study the accretion of collisionless plasma onto a rotating black hole from first principles using axisymmetric general-relativistic particle-in-cell simulations. We carry out a side-by-side comparison of these results to analogous general-relativistic magnetohydrodynamic simulations. Although there are many similarities in the overall flow dynamics, three key differences between the kinetic and fluid simulations are identified. Magnetic reconnection is more efficient, and rapidly accelerates a nonthermal particle population, in our kinetic approach. In addition, the plasma in the kinetic simulations develops significant departures from thermal equilibrium, including pressure anisotropy that excites kinetic-scale instabilities, and a large field-aligned heat flux near the horizon that approaches the free-streaming value. We discuss the implications of our results for modeling event-horizon scale observations of Sgr A* and M87 by GRAVITY and the Event Horizon Telescope.

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Source
http://dx.doi.org/10.1103/PhysRevLett.130.115201DOI Listing

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