Effects of Magnetic Field Loops on the Dynamics of Advective Accretion Flows and Jets around a Schwarzschild Black Hole

Abstract

Magnetic fields advected along with low angular momentum accretion flows predominantly become toroidal due to the strong azimuthal velocity close to a black hole. We study self-consistently the movements of these flux tubes inside an advective disc and how they dynamically influence the flow. We find that the centrifugal barrier slows down the radial motion of the flux tubes. In this case, the large magnetic flux tubes with a significant drag force escape along the vertical axis due to buoyancy. Magnetic pressure rises close to the black hole and together with the centrifugal force, it combats gravity. The tug-of-war among these forces causes the centrifugal pressure supported shock to oscillate radially. We study the effects of successive injection of flux tubes and find how the flux tube could be trapped inside the disc in regions of highest entropy. Most interestingly, the shock wave remains at its average location and is not destroyed. We show that the toroidal field loops contribute significantly to collimate and accelerate the outflows from the centrifugal barrier and suggest this mechanism to be a way to collimate and accelerate jets.

Jets and spectral states with three-components of accretion flow around a black hole

“…Now, the possible roles of the ADAF disk can i) produce weak intrinsic radiations (Bremsstrahlung and Synchrotron emission), and soft-excess (Compton thick/slim scattering) when R t < ∼ 100r g , ii) make barrier (centrifugal and pressure supported surface) for in-falling gas of the hot component flow, which can help in the jet generation or storage of the gas around the inner region of the disk or when preceding flow is compressed enough then the flow can make strong shock in the disk. Although, the shocks can be generated without the additional ADAF barrier as shown in many theoretical and numerical studies (Kumar & Gu 2018;Lee et al 2016;Garain et al 2020;Singh et al 2021), and the post-shock region is much hotter than other flows, which can produce very high energy radiations, like, hard X−ray, and soft γ−ray. This shock can be standing or quasi-steady or moving inward in accretion flow, and these kind of geometries is represented for the LHS and HISs.…”

“…Interestingly, It has been found in the MHD simulation that the magnetic field (both toroidal and poloidal) is rapidly evolved in the post-shock region of the hot component than other part of the disk, which will be helpful to make outflows faster and collimated (Garain et al 2020). Moreover, if the ADAF can thread with the magnetic field lines then the field lines can be hold relatively against the gas of hot component, since the ADAF is always slow moving inward due to high AM.…”

GRMHD Simulations and Modeling for Jet Formation and Acceleration Region in AGNs

“…If this accreting matter involves poloidal magnetic fields, jet-like outflows develop from the resulting disk-like structure via ordinary MHD processes (e.g., [157,158]). Garain et al [159] performed GRMHD simulations of poloidal magnetic fields advected within low angular momentum accretion flows, yielding outflows from the centrifugal barrier near the horizon. Even GRMHD simulations of spherical accretion flows with magnetic fields have been investigated [160].…”

Review the possible advective disk structures around a black hole with two-type gas inflows

“…As we know that the higher R means the matter is more compressed so the post shock flow can be more hotter and denser than the pre-shock flow. The higher R in the post-shock flow can be more suitable for the inverse-Comptonization process (Chakrabarti & Titarchuk 1995;Mandal & Chakrabarti 2010; and this region can also produce the outflows (Giri & Chakrabarti 2013;Lee et al 2016;Kumar & Chattopadhyay 2017;Garain et al 2020) due to the generated abrupt thermal gradient force in the post-shock region. In panels (c) and (d) of Figure 7 are represented the variations of the r ob with B ob for the ADAFs, and the λ variations with r, for three values of the B ob , respectively.…”

“…The sub-Keplerian flow can give many types of the advective solutions depend on the variation of the AM distributions in the flow. Two types of the advective solutions for the hot accretion flow are very popular in the literature, one, the shocked accretion flow (Fukue 1987;Chakrabarti 1989;Molteni et al 1996;Lanzafame et al 1998;Mukhopadhyay 2003;Becker et al 2008;Das & Czerny 2012;Giri & Chakrabarti 2013;Das et al 2014;Lee et al 2016;Kumar & Chattopadhyay 2017;Dihingia et al 2019;Lee & Becker 2020;Garain et al 2020) and the other, a special kind of the smooth solution known as the Advection-Dominated Accretion Flow (ADAF) solution (Ichimaru 1977;Narayan & Yi 1994;Honma 1996; Narayan et al 1997;Lu et al 1999;Kato et al 2008;Narayan et al 2012;Yuan & Narayan 2014;Kumar & Gu 2018. Interestingly, both the advective disk solutions/models can be generated from the same set of the fluid differential equations and assumptions, but both (shock and ADAF) solutions have basic difference of AM distribution.…”