Collisionless Accretion onto Black Holes: Dynamics and Flares

Alisa Galishnikova, Alexander Philippov, Eliot Quataert, Fabio Bacchini, Kyle Parfrey, Bart Ripperda

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


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.

Original languageEnglish (US)
Article number115201
JournalPhysical review letters
Issue number11
StatePublished - Mar 17 2023

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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