2008/02/29 by Mami Machida, Ryōji Matsumoto, Ryoji Matsumoto · 36 citations
Engineering · Physics and Astronomy · #Accretion (finance) #Angular momentum #Astrophysical Phenomena and Observations #Astrophysics #Black hole (networking) #Classical mechanics #Geometry #Heat Transfer Mechanisms #Magnetic field #Physics #Pulsars and Gravitational Waves Research #Quantum mechanics #Rotating black hole #Schwarzschild radius #Torus #astro-ph
paper · pdf · doi:10.1093/pasj/60.3.613
published in Publications of the Astronomical Society of Japan 60(3), 613-626 (Oxford University Press) · 22 pages, 17 figures, accepted for publication in PASJ (PASJ,60,pp.613-626). Replaced to high resolution version
openalex publication_date 2008/06/25 · arxiv created 2009/05/18 · arxiv updated 2015/05/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Abstract We present the results of global three-dimensional magneto-hydrodynamic simulations of black-hole accretion flows. We focus on the dependence of the numerical results on the gas temperature supplied from the outer region. General-relativistic effects were taken into account using the pseudo-Newtonian potential. We ignored radiative cooling of the accreting gas. The initial state was a torus threaded by a weak azimuthal magnetic field. We found that the mass-accretion rate and the mass-outflow rate strongly depend on the temperature of the initial torus. The ratio of the average Maxwell stress generated by the magneto-rotational instability (MRI) to the gas pressure, α ≡ ⟨ B\varpi Bφ/4 π ⟩ / ⟨ P ⟩ , is α ∼0.05 in a hot torus and α ∼0.01 in a cool torus. In the cool model, a constant angular momentum inner torus is formed around 4-8rs, where rs is the Schwarzschild radius. This inner torus deforms itself from a circle to a crescent quasi-periodically. During this deformation, the mass-accretion rate, the magnetic energy and the Maxwell stress increase. As the magnetic energy is released, the inner torus returns to a circular shape and starts the next cycle. The power spectral density (PSD) of the time variation of the mass-accretion rate in the cool model has a low-frequency peak around 10Hz when we assumed a 10M\odot black hole. The mass outflow rate in the low temperature model also shows quasi-periodic oscillation.