The effects of magnetic field strength on the properties of wind generated from hot accretion flow

Abstract

Context. Observations indicate that wind can be generated in hot accretion flow. By performing numerical simulations, Yuan et al. studied the detailed properties of wind generated from weakly magnetized accretion flow. However, properties of wind generated from strongly magnetized hot accretion flow have not been studied. Aims. In this paper, we study the properties of wind generated from both weakly and strongly magnetized accretion flow. We focus on how the magnetic field strength affects the wind properties. Methods. We solve time-steady two-dimensional magnetohydrodynamic (MHD) equations of black hole accretion in the presence of large-scale magnetic field. We assume self-similarity in radial direction. The magnetic field is assumed to be evenly symmetric with the equatorial plane. Results. We find that wind exists in both weakly and strongly magnetized accretion flow. When magnetic field is weak (magnetic pressure is more than 2 orders of magnitude smaller than gas pressure), wind is driven by gas pressure gradient and centrifugal forces. When magnetic field is strong (magnetic pressure is slightly smaller than gas pressure), wind is driven by gas pressure gradient and magnetic pressure gradient forces. The power of wind in strongly magnetized case is just slightly larger than that in weakly magnetized case. The power of wind lies in a range P W ∼ 10 −4 − 10 −3Ṁ in c 2 , withṀ in and c being mass inflow rate and speed of light, respectively. The possible role of wind in active galactic nuclei feedback is briefly discussed.

Faraday Rotation in the Jet of M87 inside the Bondi Radius: Indication of Winds from Hot Accretion Flows Confining the Relativistic Jet

“…We used simple onedimensional self-similar solutions for the density and magnetic field strength in the hot accretion flows model, while it is unclear whether this is valid or not. Studies of two dimensional solutions of hot accretion flows showed a breakdown of spherical symmetry (e.g., Mosallanezhad et al 2016;Bu & Mosallanezhad 2018), though the behavior of physical parameters measured close to the jet axis is poorly constrained yet. We assumed ≈ 130 rad/m 2 for the contribution of the diffuse gas in M87 outside the Bondi radius based on the results of RM studies of the large scale jet but this could be uncertain.…”

The wind production from black hole hot accretion flow

“…There are also some analytical works that study the wind from accretion disks (e.g. Li & Cao 2009;Xie et al 2008;Bu et al 2009;Bu & Mosallanezhad 2018;Abbassi et al 2010;Chen et al 2012;Li & Begelman 2014;Gu 2015;Cao 2016). The topic of the wind is interesting because it is now widely believed that AGN feedback plays an important role in the evolution of their host galaxies (e.g., Ciotti & Ostriker 2001, 2007Gan et al 2014;Yuan et al 2018).…”

Hot Accretion Flow in Two-Dimensional Spherical Coordinates: Considering Pressure Anisotropy and Magnetic Field

“…In Equation 2, ∇•T represents angular momentum transfer by the turbulent magnetic field. We assume T only has azimuthal component, see [10,58,88].…”

“…As with previous works (e.g., [58,88,[92][93][94]), we seek the radially self-similar solutions in the following forms:…”

“…The observations of LLAGNs (e.g., [41][42][43][44][45][46]) and the hard state of black hole X-ray binaries ( [47]) show that outflow can be launched from hot accretion flow. The launching mechanisms and properties of outflow have been studied by numerical simulations(e.g., [24,26,27,[48][49][50][51]) and analytical works ( [52][53][54][55][56][57][58]). Outflow can push away gas which surrounds the black hole at sub-parsec and parsec scales, and can finally affect the black hole accretion rate and the star formation rate of galaxies (e.g., [59][60][61][62][63][64][65][66]).…”