Disc tearing and Bardeen-Petterson alignment in GRMHD simulations of highly tilted thin accretion discs

M. Liska, C. Hesp, A. Tchekhovskoy*, A. Ingram, M. Van Der Klis, S. B. Markoff, M. Van Moer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Luminous active galactic nuclei and X-ray binaries often contain geometrically thin, radiatively cooled accretion discs. According to theory, these are - in many cases - initially highly misaligned with the black hole equator. In this work, we present the first general relativistic magnetohydrodynamic simulations of very thin (h/r ∼ 0.015-0.05) accretion discs around rapidly spinning (a ∼ 0.9) black holes and tilted by 45°-65°. We show that the inner regions of the discs with h/r ≤ 0.03 align with the black hole equator, though out to smaller radii than predicted by analytic work. The inner aligned and outer misaligned disc regions are separated by a sharp break in tilt angle accompanied by a sharp drop in density. We find that frame dragging by the spinning black hole overpowers the disc viscosity, which is self-consistently produced by magnetized turbulence, tearing the disc apart and forming a rapidly precessing inner sub-disc surrounded by a slowly precessing outer sub-disc. We find that the system produces a pair of relativistic jets for all initial tilt values. At small distances, the black hole launched jets precess rapidly together with the inner sub-disc, whereas at large distances they partially align with the outer sub-disc and precess more slowly. If the tearing radius can be modeled accurately in future work, emission model independent measurements of black hole spin based on precession-driven quasi-periodic oscillations may become possible.

Original languageEnglish (US)
Pages (from-to)983-990
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - Oct 1 2021


  • MHD
  • accretion, accretion discs
  • black hole physics
  • galaxies: jets
  • methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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