A non-local magneto-curvature instability in a differentially rotating disk

Abstract

A global mode is shown to be unstable to non-axisymmetric perturbations in a differentially rotating Keplerian disk containing either vertical or azimuthal magnetic fields. In an unstratified cylindrical disk model, using both global eigenvalue stability analysis and linear global initial-value simulations, it is demonstrated that this instability dominates at strong magnetic field where local standard MRI becomes stable. Unlike the standard MRI mode, which is concentrated in the high flow shear region, these distinct global modes (with low azimuthal mode numbers) are extended in the global domain and are Alfvén continuum driven unstable modes. As its mode structure and relative dominance over MRI is inherently determined by the global spatial curvature as well as the flow shear in the presence of magnetic field, we call it the magneto-curvature (magneto-spatial-curvature) instability. Consistent with the linear analysis, as the field strength is increased in the nonlinear simulations, a transition from a MRI-driven turbulence to a state dominated by global non-axisymmetric modes is obtained. This global instability could therefore be a source of nonlinear transport in accretion disks at higher magnetic field than predicted by local models.

Accepted for publication in the Astrophysical Journal

References in corpus (12)

• The Influence of Magnetic Field Geometry on the Evolution of Black Hole Accretion Flows: Similar Disks, Drastically Different Jets
• MHD simulations of the magnetorotational instability in a shearing box with zero net flux. II. The effect of transport coefficients
• Impact of dimensionless numbers on the efficiency of MRI-induced turbulent transport
• Experimental evidence for magnetorotational instability in a helical magnetic field
• Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence
• A self-sustaining nonlinear dynamo process in Keplerian shear flows
• On Self-Sustained Dynamo Cycles in Accretion Discs
• Aspect ratio dependence in magnetorotational instability shearing box simulations
• Numerical simulations of the Princeton magneto-rotational instability experiment with conducting axial boundaries
• Identification of a non-axisymmetric mode in laboratory experiments searching for standard magnetorotational instability
• The Super-Alfvénic Rotational Instability in accretion disks about black holes
• Onset of Plasmoid Reconnection during Magnetorotational Instability

Cited by in corpus (5)

• Identification of a non-axisymmetric mode in laboratory experiments searching for standard magnetorotational instability
• A generalized effective potential for differentially rotating plasmas
• Parametric Survey of Nonaxisymmetric Accretion Disk Instabilities: Magnetorotational Instability to Super-Alfvénic Rotational Instability
• Non-ideal stability analysis of differentially rotating plasmas with global curvature effects
• Global Non-Axisymmetric Hall Instabilities in a Rotating Plasma