Abstract
In extremely low accretion rate systems, the ion mean-free path can be much larger than the gyroradius. Therefore, gas pressure is anisotropic with respect to magnetic field lines. The effects of pressure anisotropy can be modeled by an anisotropic viscosity with respect to magnetic field lines. Angular momentum can be transferred by anisotropic viscosity. In this paper, we investigate hot accretion flow with anisotropic viscosity. We consider the case that anisotropic viscous stress is much larger than Maxwell stress. We find that the flow is convectively unstable. We also find that the mass inflow rate decreases towards a black hole. Wind is very weak; its mass flux is 10−15% of the mass inflow rate. The inward decrease of inflow rate is mainly due to convective motions. This result may be useful to understand the accretion flow in the Galactic Center Sgr A* and M 87 galaxy.
Highlights
Key words. accretion, accretion disks – black hole physics – hydrodynamics – ISM: jets and outflows – conduction. Hot accretion flows, such as advection-dominated accretion flows (ADAFs; Narayan & Yi 1994, 1995; Abramowicz et al 1995) are of great interest because they are likely operating in low-luminosity active galactic nuclei (AGN), that is, the majority of galaxies at least in the nearby Universe, hard and quiescent states of black hole X-ray binaries
We analyze the properties of hot accretion flow at the quasisteady state, that is, the net accretion rate is independent of radius
Dilute plasmas, the mean-free path of ions can be large compared to the typical scalelength of accretion flow
Summary
Hot accretion flows, such as advection-dominated accretion flows (ADAFs; Narayan & Yi 1994, 1995; Abramowicz et al 1995) are of great interest because they are likely operating in low-luminosity active galactic nuclei (AGN), that is, the majority of galaxies at least in the nearby Universe, hard and quiescent states of black hole X-ray binaries (see Yuan & Narayan 2014, for the latest review). One of the most important findings by numerical simulations in this field is the discovery of strong wind launched from the accretion flow (Yuan et al 2012b; Narayan et al 2012; Li et al 2013; Sadowski et al 2016) This result was soon confirmed by the 3 million seconds of Chandra observation of the accretion flow around the super massive black hole in the Galactic Center, combined with modeling of the detected iron emission lines (Wang et al 2013). Particle-in-cell simulations of shear flows have shown that the effective collision rate of particles can be increased by wave-particle interactions (Kunz et al 2014; Hellinger & Trávnícek 2015; Riquelme et al 2015; Sironi & Narayan 2015) This conclusion is supported by measurements in the solar wind, which show that the gas is not totally collisionless
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