Magnetically Driven Accretion Flows in the Kerr Metric. II. Structure of the Magnetic Field

By Shigenobu Hirose, Julian Krolik, Jean-Pierre De Villiers, J. Hawley. 2003

154 citations recorded by the source corpus.

We present a detailed analysis of the magnetic field structure found in a set of four general relativistic three-dimensional MHD simulations of accreting tori in the Kerr metric with different black hole spins. Among the properties analyzed are the field strength as a function of position and black hole spin, the shapes of field lines, the degree to which they connect different regions, and their degree of tangling. Strong magnetic field is found toward small radii, and field strength increases with black hole spin. In the main disk body, inner torus, and corona the field is primarily toroidal. Most field lines passing through a given radius in these regions wander through a narrow radial range, suggesting an overall tightly wound spiral structure. In the main disk body and inner torus sharp field-line bends on small spatial scales are superposed on the spirals, but the field lines are much smoother in the corona. The magnetic field in the plunging region is also comparatively smooth, being stretched out radially by the infalling gas. The magnetic field in the axial funnel resembles a split monopole, but with evidence of frame dragging of the field lines near the poles of the black hole. We investigate prior speculations about the structure of the magnetic fields and discuss how frequently certain configurations are seen in the simulations. For example, coronal loops are very rare, and field lines connecting high latitudes on the event horizon to the disk are not found at all. Almost the entire system is matter-dominated; the only force-free regions are in the axial funnel. We also analyze the distribution of current density, with a view toward identifying possible locations of magnetic energy dissipation. Regions of high current density are concentrated toward the inner torus and plunging region. Dissipation inside the marginally stable orbit may provide a new source of energy for radiation, supplementing the dissipation associated with torques in the stably orbiting disk body.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/e849ad6ad659736fec325033a8ffca8c1e9e7de6

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In Astronomy and Astrophysics

1. Ramesh Narayan
2. J. McKinney
3. A. Tchekhovskoy
4. F. Yuan
5. A. Sa̧dowski
6. Julian Krolik
7. J. Hawley
8. E. Nakar

Citations in the corpus

• Total and Jet Blandford-Znajek Power in the Presence of an Accretion Disk (2005, unknown): “DOMINANCE OF THE BLANDFORD-ZNAJEK EFFECT Figure 2 shows the possible types of field geometries in the disk (see also, e.g., Blandford 2002; Hirose et al. 2004).”
• Vertical Structure of Gas Pressure-dominated Accretion Disks with Local Dissipation of Turbulence and Radiative Transport (2005, background): “In addition, as demonstrated in Hirose et al. (2004), there can be extremely high current-density regions at radii comparable to or smaller than the marginally stable orbit and well away from the equatorial plane.”
• Accretion disc viscosity: how big is alpha? (2007, background): “5 of Hirose et al. (2004), we see that large-scale magnetic linkages can occur in the radial direction.”
• Hot Accretion Flows Around Black Holes (2014, methodology): “Representative results from 3D GRMHD simulations can be found in the series of early papers by De Villiers and collaborators (De Villiers et al. 2003, 2005; Hirose et al. 2004; Krolik et al. 2005) and Gammie and collaborators (Gammie et al. 2004, McKinney & Gammie 2004, McKinney 2006).”
• Short-hard gamma-ray bursts (2007, methodology): “…Mineshige & Shibata, 2004) to GR simulations using a Kerr metric in two dimensions (McKinney & Gammie, 2004; McKinney, 2005, 2006) and in three dimensions (De Villiers, Hawley & Krolik, 2003; De Villiers et al. , 2005; Hirose et al. , 2004; Krolik, Hawley & Hirose, 2005; Hawley & Krolik, 2006).”
• Radiative efficiency of hot accretion flows (2012, background): “Numerical simulations have shown that a large-scale toroidal magnetic field is likely to exist in the inner region of the accretion flow, imposed on the stochastic component (e.g. Hirose et al. 2004).”
• NONSTEADY ACCRETION IN PROTOSTARS (2008, background): “Global disk simulations (Hirose et al. 2004; McKinney & Narayan 2007; Beckwith et al. 2008), local disk simulations in which the mean field is allowed to evolve because of the boundary conditions (Brandenburg et al. 1995), and observations of the galactic disk (Vallee 2004) all exhibit a “mean”…”
• The Influence of Magnetic Field Geometry on the Evolution of Black Hole Accretion Flows: Similar Disks, Drastically Different Jets (2007, methodology): “In doing so we continue a program of black hole accretion disk simulations begun in De Villiers et al. (2003), Hirose et al. (2004), De Villiers et al. (2005), Krolik et al. (2005) and Hawley & Krolik (2006).”
• Magnetically Driven Accretion in the Kerr Metric. III. Unbound Outflows (2004, background): “The second paper of the series (Hirose et al. 2004; hereafter Paper II) discussed the overall magnetic field configurations in the accretion flow.”
• BLACK HOLE SPIN AND THE RADIO LOUD/QUIET DICHOTOMY OF ACTIVE GALACTIC NUCLEI (2009, background): “Another possibility is that a stronger dependence on spin could occur if some field lines attach between the disk and the BH (Ye & Wang 2005), although such configurations are not seen in GR MHD simulations of accretion disks (Hirose et al. 2004; McKinney 2005b).”
• General relativistic magnetohydrodynamic simulations of the jet formation and large-scale propagation from black hole accretion systems (2006, background): “They have also shown that the magnetic field corresponding to the Blandford-Znajek effect dominates all other magnetic field geometries (Hirose et al. 2004; McKinney 2005a).”
• Equation of state in relativistic magnetohydrodynamics: variable versus constant adiabatic index (2007, background): “Finally, the type of field geometries observed in simulations that thread the disk and corona (Hirose et al. 2004; McKinney 2005) might depend on the EoS through the effect of the stiffness (larger Γ leads to harder EoSs) of the EoS on the turbulent diffusion of magnetic fields.”
• Energy, momentum and mass outflows and feedback from thick accretion discs around rotating black holes (2013, methodology): “…predictions of the Blandford– Znajek (BZ) jet model are supported by general relativistic magnetohydrodynamic (GRMHD) simulations (Komissarov 2001; Hirose et al. 2004; De Villiers et al. 2005; McKinney 2005; Hawley & Krolik 2006; Beckwith, Hawley & Krolik 2008; Tchekhovskoy, Narayan & McKinney…”
• Magnetically Driven Accretion Flows in the Kerr Metric. IV. Dynamical Properties of the Inner Disk (2004, background): “Hirose et al. (2004) showed that the relative magnitude of the magnetic field in the inner disk grows steadily with increasing black hole spin.”
• Spacetime approach to force-free magnetospheres (2014, background): “Qualitative discussions of different field line types in black hole magnetospheres can be found in (Thorne, Price & MacDonald 1986; Blandford 2002; Hirose et al. 2004; McKinney 2005). intersection is necessary for establishing that conductors determine the rotation frequency of their field lines…”