2000/11/08 by Takuhito Kuwabara, T. Kuwabara, Kazunari Shibata +4 · 1 citation
Physics and Astronomy · #Accretion (finance) #Angular momentum #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Classical mechanics #Galaxies: Formation, Evolution, Phenomena #Geometry #Jet (fluid) #Magnetic diffusivity #Magnetic field #Magnetohydrodynamic drive #Magnetohydrodynamics #Mechanics #Physics #Quantum mechanics #RADIUS #Torus #astro-ph
paper · pdf · doi:10.1093/pasj/52.6.1109
24 pages, LaTex, 15 jpg figures include, accepted for PASJ
arxiv created 2000/11/08 · openalex publication_date 2000/12/01 · arxiv updated 2015/06/24 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Abstract We carried out 2.5-dimensional resistive magnetohydrodynamic simulations to study the effects of magnetic diffusivity on magnetically driven mass accretion and jet formation. The initial state is a constant angular-momentum torus threaded by large-scale vertical magnetic fields. Since the angular momentum of the torus is extracted due to magnetic braking, the torus medium falls toward the central region. The infalling matter twists the large-scale magnetic fields and drives bipolar jets. We found that (1) when the normalized magnetic diffusivity, η ≡ η/(r0 V_\textrm Ko), where VK0 is the Keplerian rotation speed at a reference radius r=r0, is small ( η ≤ 10-3), mass accretion and jet formation take place intermittently; (2) when 10-3≤ η ≤ 10-2, the system evolves toward a quasi-steady state; and (3) when η ≥ 10-2 the accretion/mass outflow rate decreases with bar η and approaches 0. The results of these simulations indicate that in the center of a galaxy which has a super-massive ( ∼ 109M⊙ ) black hole, a massive ( ∼ 108M⊙ ) gas torus and magnetic braking provide a mass accretion rate which is sufficient to explain the activity of AGNs when η ≤ 5 ×10-2