Instability in strongly magnetized accretion discs: A global perspective

Abstract

We examine the properties of strongly magnetized accretion discs in a global framework, with particular focus on the evolution of magnetohydrodynamic instabilities such as the magnetorotational instability (MRI). Work by Pessah and Psaltis showed that MRI is stabilized beyond a critical toroidal field in compressible, differentially rotating flows and, also, reported the appearance of two new instabilities beyond this field. Their results stemmed from considering geometric curvature effects due to the suprathermal background toroidal field, which had been previously ignored in weak-field studies. However, their calculations were performed under the local approximation, which poses the danger of introducing spurious behavior due to the introduction of global geometric terms in an otherwise local framework. In order to avoid this, we perform a global eigenvalue analysis of the linearized MHD equations in cylindrical geometry. We confirm that MRI indeed tends to be highly suppressed when the background toroidal field attains the Pessah-Psaltis limit. We also observe the appearance of two new instabilities that emerge in the presence of highly suprathermal toroidal fields. These results were additionally verified using numerical simulations in PLUTO. There are, however, certain differences between the the local and global results, especially in the vertical wavenumber occupancies of the various instabilities, which we discuss in detail. We also study the global eigenfunctions of the most unstable modes in the suprathermal regime, which are inaccessible in the local analysis. Overall, our findings emphasize the necessity of a global treatment for accurately modeling strongly magnetized accretion discs.

23 pages, 7 Figures and 1 Table. Accepted for publication in MNRAS

References in corpus (26)

• PLUTO: a Numerical Code for Computational Astrophysics
• The Formation and Structure of a Strongly Magnetized Corona above Weakly Magnetized Accretion Disks
• Instability of toroidal magnetic field in jets and plerions
• The magnetic nature of disk accretion onto black holes
• Local Study of Accretion Disks with a Strong Vertical Magnetic Field: Magnetorotational Instability and Disk Outflow
• Accretion Discs with Strong Toroidal Magnetic Fields
• Local outflows from turbulent accretion disks
• Accretion disc dynamo activity in local simulations spanning weak-to-strong net vertical magnetic flux regimes
• Global Simulations of Differentially Rotating Magnetized Disks : Formation of Low-Beta Filaments and Structured Corona
• The magnetorotational instability as a jet launching mechanism
• The Stability of Magnetized Rotating Plasmas with Superthermal Fields
• Thin accretion disks are stabilized by a strong magnetic field
• Magnetohydrodynamic Instabilities in Shearing, Rotating, Stratified Winds and Disks
• Local Dynamical Instabilities in Magnetized, Radiation Pressure Supported Accretion Disks
• The Accretion Disk Wind in the Black Hole GRS 1915+105
• Extending the Shakura-Sunyaev approach to a strongly magnetized accretion disc model
• Accretion disk dynamo as the trigger for X-ray binary state transitions
• Magnetically-levitating disks around supermassive black holes
• Thermal Equilibria of Magnetically Supported, Black Hole Accretion Disks
• Self-organisation in protoplanetary disks: global, non-stratified Hall-MHD simulations
• Strongly magnetized accretion discs require poloidal flux
• On the Decay of Strong Magnetization in Global Disc Simulations with Toroidal Fields
• On the Global Stability of Magnetized Accretion Disks. II. Vertical and Azimuthal Magnetic Fields
• Shearing box simulations of accretion disk winds
• Local and global aspects of the linear MRI in accretion disks
• Magnetorotationally driven wind cycles in local disc models

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• Global Radiation Magneto-hydrodynamic Simulations of Sub-Eddington Accretion Disks around Supermassive Black Holes
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• The large-scale magnetic field of a thin accretion disk with outflows
• Global Three-Dimensional Radiation Magnetohydrodynamic Simulations of Accretion onto a Stellar Mass Black Hole at Sub- and Near-critical Accretion Rates
• Saturation of the magnetorotational instability and the origin of magnetically elevated accretion discs
• Internal instabilities in magnetized jets
• Relating Kerr SMBHs in Active Galactic Nuclei to RAD configurations
• Influence of toroidal magnetic field in multi-accreting tori
• Dynamical structure of highly eccentric discs with applications to tidal disruption events
• Importance of magnetic fields in highly eccentric discs with applications to tidal disruption events
• Limiting effects in clusters of misaligned toroids orbiting static SMBHs
• Parametric Survey of Nonaxisymmetric Accretion Disk Instabilities: Magnetorotational Instability to Super-Alfvénic Rotational Instability
• Origin of hydrodynamic instability from noise: from laboratory flow to accretion disk
• Hydrodynamical instability with noise in the Keplerian accretion discs: Modified Landau equation
• Forced linear shear flows with rotation: rotating Couette-Poiseuille flow, its stability and astrophysical implications
• An effective model for magnetic field amplification by the magnetorotational and parasitic instabilities
• The competition between the hydrodynamic instability from noise and magnetorotational instability in the Keplerian disks
• Gravitoturbulent dynamo in global simulations of gaseous disks