Formation of spiral discontinuities in black hole accretion flows
Abstract
X-ray binaries and active galactic nuclei (AGN) show various energetic activities such as flares and jets. The energy source of the activities is the gravitational energy released when matter infalls through an accretion disk. In order for the rotating gas to fall to the central black hole, angular momentum should be transported. Based on numerical simulations, the origin of the angular momentum transport is thought to be magnetic turbulence caused by the magneto-rotational instability (MRI) growing in the differential rotating system. However, numerical simulations have revealed that the saturation level of the magnetic energy is anti-correlated with the numerical resolution. We report the results of global 3D magneto-hydrodynamic simulations of accretion disks by applying the state of the art MHD code CANS+, which adopts a scheme fifth-order accurate in space. We assume an initial torus threaded by the weak toroidal magnetic fields. After the initial weak magnetic fields are amplified by magneto-rotational instability, magnetic turbulence is developed in the accretion disk and the disk approaches to a quasi-steady state. In addition to the magnetic turbulence, spiral-shaped non-axisymmetric current sheets are formed due to accretion. Such spiral current sheets produce density discontinuities and provide Maxwell stress which drives accretion.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E.982M