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A 2.5-dimensional viscous, resistive, advective magnetized accretion-outflow coupling in black hole systems: a higher order polynomial approximation

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Research in Astronomy and Astrophysics 2017年第10期17卷 41-66页

作者： Shubhrangshu Ghosh Center for Astroparticle Physics and Space Science Department of Physics Bose Institute Block EN Sector V Salt Lake

The correlated and coupled dynamics of accretion and outflow around black holes （BHs） are essentially governed by the fundamental laws of conservation as outflow extracts matter, momentum and energy from the accretion region. Here we analyze a robust form of 2.5-dimensional viscous, resistive, advective magnetized accretion-outflow coupling in BH systems. We solve the complete set of coupled MHD conservation equations self-consistently, through invoking a generalized polynomial expansion in two dimensions. We perform a critical analysis of the accretion-outflow region and provide a complete quasi-analytical family of solutions for advective flows. We obtain the physically plausible outflow solu- tions at high turbulent viscosity parameter a（〉0.3）, and at a reduced scale-height, as magnetic stresses compress or squeeze the flow region. We found that the value of the large-scale poloidal magnetic field Bp is enhanced with the increase of the geometrical thickness of the accretion flow. On the other hand, differential magnetic torque （-r2BBz） increases with the increase in M. Bp, -r2BBz as well as the plasma beta/3p get strongly augmented with the increase in the value of a, enhancing the transport of vertical flux outwards. Our solutions indicate that magnetocentrifugal acceleration plausibly plays a dominant role in effusing out plasma from the radial accretion flow in a moderately advective paradigm which is more centrifugally dominated. However in a strongly advective paradigm it is likely that the thermal pressure gradient would play a more contributory role in the vertical transport of plasma.

关键词： accretion accretion disks -- black hole physics -- magnetohydrodynamics -- galaxies：active -- galaxies： jets -- X-rays： binaries

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On the torque exerted by a warped, magnetically threaded accretion disk

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Research in Astronomy and Astrophysics 2021年第3期21卷 15-20页

作者： Chang Liu Xiang-Dong Li School of Astronomy and Space Science Nanjing UniversityNanjing 210023China Key laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210023

Most astrophysical accretion disks are likely to be warped.In X-ray binaries,the spin evolution of an accreting neutron star is critically dependent on the interaction between the neutron star magnetic field and the accretion disk.There have been extensive investigations on the accretion torque exerted by a coplanar disk that is magnetically threaded by the magnetic field lines from the neutron stars,but relevant works on warped/tilted accretion disks are still lacking.In this paper we develop a simplified twocomponent model,in which the disk is comprised of an inner coplanar part and an outer,tilted part.Based on standard assumption on the formation and evolution of the toroidal magnetic field component,we derive the dimensionless torque and show that a warped/titled disk is more likely to spin up the neutron star compared with a coplanar disk.We also discuss the possible influence of various initial parameters on the torque.

关键词： accretion accretion disks magnetic field X-ray binaries

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Structures of magnetized thin accretion disks

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Science China Mathematics 2002年第11期45卷 1487-1496页

作者：李晓卿季海生 Physics Department Nanjing Normal University Nanjing China Purple Mountain Observatory Chinese Academy of Sciences Nanjing China

We investigate the magnetohydrodynamic (MHD) process in thin accretion disks. Therelevant momentum as well as magnetic reduction equations in the thin disk approximation areincluded. On the basis of these equations, we examine numerically the stationary structures, includingdistributions of the surface mass density, temperature and flow velocities of a disk around a youngstellar object (YSO). The numerical results are as follows: (i) There should be an upper limit to themagnitude of magnetic field, such an upper limit corresponds to the equipartition field. For relevantmagnitude of magnetic field of the disk's interior the disk remains approximately Keplerian. (ii) Thedistribution of effective temperature T(r) is a smoothly decreasing function of radius with power 1 corresponding to the observed radiation flux density, provided that the magnetic fieldindex γ= -1/2,is suitably chosen.

关键词： accretion disks, young stellar objects, magnetohydrodynamics.

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Effects of the energy equation in studies of limit-cycle behaviors of black hole accretion disks

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Science China(Physics,Mechanics & Astronomy) 2009年第6期52卷 954-959页

作者： XUE Li LU JuFu Department of Physics and Institute of Theoretical Physics and Astrophysics Xiamen UniversityXiamen 361005China

The inconsistency of the energy equation used in the literature is pointed out and a new consistent energy equation is given. With this new energy equation, calculations are made for the limit-cycle behaviors of thermally unstable accretion disks around black holes. From the comparison of our numerical results with those obtained using the inconsistent energy equation, it is found that the inconsistent energy equation undervalues the temperature and overvalues the effective optical depth when the accreted gas becomes effectively optically thin. Thus, it is dangerous if the inconsistent energy equation is used in the studies of very hot and optically thin accretion flows such as advection-dominated accretion flows (ADAFs), and our new energy equation is likely to be a better alternative.

关键词： accretion: accretion disks black hole physics hydrodynamics instabilities

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Geodynamics of oceanic plateau and plume head accretion and their role in Phanerozoic orogenic systems of China

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Geoscience Frontiers 2015年第1期6卷 49-59页

作者： Peter G.Betts Louis Moresi Meghan S.Miller David Willis School of Earth Atmosphere and EnvironmentMonash UniversityClayton Campus School of Mathematical Sciences Monash UniversityClayton Campus Department of Earth Sciences University of Melbourne Department of Earth Sciences University of Southern California

We present three 3D numerical models of deep subduction where buoyant material from an oceanic plateau and a plume interact with the overriding plate to assess the influence on subduction dynamics, trench geometry, and mechanisms for plateau accretion and continental growth. Transient instabilities of the convergent margin are produced, resulting in： contorted trench geometry; trench migration parallel with the plate margin; folding of the subducting slab and orocline development at the convergent margin; and transfer of the plateau to the overriding plate. The presence of plume material beneath the oceanic plateau causes fiat subduction above the plume, resulting in a ＂bowed＂ shaped subducting slab. In plateau-only models, plateau accretion at the edge of the overriding plate results in trench migration around the edge of the plateau before subduction is re-established directly behind the trailing edge of the plateau. The plateau shortens and some plateau material subducts. The presence of buoyant plume material beneath the oceanic plateau has a profound influence on the behaviour of the convergent margin. In the plateau ~ plume model, plateau accretion causes rapid trench advance. Plate convergence is accommodated by shearing at the base of the plateau and shortening in the overriding plate. The trench migrates around the edge of the plateau and subduction is re-established well behind the trailing edge of the plateau, effectively embedding the plateau into the overriding plate. A slab window forms beneath the accreted plateau and plume material is transferred from the subducting plate to the over- riding plate through the window. In all of the models, the subduction zone maintains a relatively stable configuration away from the buoyancy anomalies within the downgoing plate. The models provide a dynamic context for plateau and plume accretion in Phanerozoic accretionary orogenic systems such as the East China Orogen and the Central Asian Orogen （Altiads）, which are characterised by accreted ophiolite complexes

关键词： Subduction accretion Plateau Plume Central Asian Orogen Geodynamics

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Matter accretion onto Einstein-aether black holes via well-known fluids

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Chinese Physics C 2020年第6期44卷 182-196页

作者： M.Umair Shahzad Rafaqat Ali Abdul Jawad Shamaila Rani Department of Mathematics University of OkaraOkaraPakistan Department of Mathematics COMSATS University IslamabadLahore-CampusPakistan

We study matter accretion onto Einstein-aether black holes by adopting the Hamiltonian approach.The general solution of accretion is discussed using the isothermal equation of state.Different types of fluids are considered,including ultra-relativistic,ultra-stiff,sub-relativistic,and radiation fluids,and the accretion process onto Einstein-aether black holes is analyzed.The behavior of the fluid flow and the existence of critical points is investigated for Einstein-aether black holes.We further discuss the general expression and behavior of polytropic fluid onto Einstein-aether black holes.The most important feature of this work is the investigation of the mass accretion rate of the above-mentioned fluids and the comparison of our findings with the Schwarzschild black hole,which generates particular signatures.Moreover,the maximum mass accretion rate occurs near the Killing and universal horizons,and the minimum accretion rate lies between them.

关键词： black hole accretion homo-clinic orbits

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Nucleosynthesis in the accretion disks of Type Ⅱ collapsars

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Research in Astronomy and Astrophysics 2013年第9期13卷 1063-1074页

作者： Indrani Banerjee Banibrata Mukhopadhyay Department of Physics Indian Institute of Science

We investigate nucleosynthesis inside the gamma-ray burst （GRB） accre- tion disks formed by the Type II collapsars. In these collapsars, the core collapse of massive stars first leads to the formation of a proto-neutron star. After that, an out- ward moving shock triggers a successful supernova. However, the supernova ejecta lacks momentum and within a few seconds the newly formed neutron star gets trans- formed to a stellar mass black hole via massive fallback. The hydrodynamics of such an accretion disk formed from the fallback material of the supernova ejecta has been studied extensively in the past. We use these well-established hydrodynamic models for our accretion disk in order to understand nucleosynthesis, which is mainly ad- vection dominated in the outer regions. Neutrino cooling becomes important in the inner disk where the temperature and density are higher. The higher the accretion rate （M） is, the higher the density and temperature are in the disks. We deal with accre- tion disks with relatively low accretion rates： 0.001 Mo s-1 ~ 3）/~ 0.01 Mo S--1 and hence these disks are predominantly advection dominated. We use He-rich and Si- rich abundances as the initial condition of nucleosynthesis at the outer disk, and being equipped with the disk hydrodynamics and the nuclear network code, we study the abundance evolution as matter inflows and falls into the central object. We investigate the variation in the nucleosynthesis products in the disk with the change in the initial abundance at the outer disk and also with the change in the mass accretion rate. We report the synthesis of several unusual nuclei like 31p, 39K, 43Sc＇ 35C1 and various isotopes of titanium, vanadium, chromium, manganese and copper. We also confirm that isotopes of iron, cobalt, nickel, argon, calcium, sulphur and silicon get synthe- sized in the disk, as shown by previous authors. Much of these heavy elements thus synthesized are ejected from the disk via outflows and hence they should leave their signature in observed data.

关键词： accretion accretion disks -- gamma rays： bursts -- black hole physics-- nuclear reactions nucleosynthesis abundances

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Dark Energy accretion onto Van der Waal's Black Hole

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Communications in Theoretical Physics 2019年第2期71卷 209-219页

作者： Sandip Dutta Ritabrata Biswas Department of Mathematics The University of Burdwan

We consider the most general static spherically symmetric black hole metric. The accretion of the fluid flow around the Van der Waal's black hole is investigated and we calculate the fluid's four-velocity, the critical point and the speed of sound during the accretion process. We also analyze the nature of the universe's density and the mass of the black hole during accretion of the fluid flow. The density of the fluid flow is also taken into account. We observe that the mass is related to redshift. We compare the accreting power of the Van der Waal's black hole with Schwarzschild black hole for different accreting fluid.

关键词： black hole physics thermodynamics accretion disc extended Chaplygin gas

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Temperature Profile of Black Hole accretion Disc with Magnetic Coupling

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Communications in Theoretical Physics 2002年第8期38卷 247-252页

作者： LEI Wei-Hua WANG Ding-Xiong XIAO Kan Department of Physics Huazhong University of Science and Technology Wuhan 430074 China Department of Physics Huazhong University of Science and Technology Wuhan 430074 China Department of Physics Huazhong University of Science and Technology Wuhan 430074 China

Two new mapping relations between the angular coordinate on the black hole (BH) horizon and radialcoordinate on the disc are given according to the requirement of general relativity and Maxwell's equations, and theeffects of magnetic coupling (MC) on temperature of accretion disc are investigated by comparing with pure accretion.It is shown that the MC effects on the temperature profile are related intimately to the BH spin, and the influenceon the peak value of disc temperature based on the modified mapping relations is not as great as that based on thelinear mapping.The peak value and the corresponding radius of peak value ring of disc temperature do not increasemonotonically as the increasing spin of BH, each containing a maximum for the fast-spinning BH. The value ranges ofthe bolometric luminosity and color temperature of the disc are both extended by the MC effects.

关键词： black hole, accretion disc, magnetic coupling

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Black holes in asymptotic safety with higher derivatives:accretion and stability analysis

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Chinese Physics C 2021年第7期45卷 293-304页

作者： Fabian H.Zuluaga Luis A.Sanchez Escuela de Fisica Universidad Nacional de ColombiaA.A.3840MedellinColombia

We review steady spherically symmetric accretion onto a renormalization group improved Schwarzschild space-time,which is a solution to an asymptotically safe theory(AS)containing high-derivative terms.We use a Hamiltonian dynamical system approach for the analysis of the accretion of four types of isothermal test fluids:ultra-stiff fluid,ultra-relativistic fluid,radiation fluid,and sub-relativistic fluid.An important outcome of our study is that,contrary to the claim in a recent work,there are physical solutions for the accretion of an ultra-relativistic fluid in AS,which include subsonic,supersonic,and transonic regimes.Furthermore,we study quantum corrections to the known stability of the accretion in general relativity(GR).To this end,we use a perturbative procedure based on the continuity equation with the mass accretion rate being the perturbed quantity.Two classes of perturbations are studied:standing and traveling waves.We find that quantum gravity effects either enhance or diminish the stability of the accretion depending on the type of test fluid and the radial distance to the central object.

关键词： asymptotic safety black holes accretion stability

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