Magnetorotational instability in eccentric disks

Abstract

Eccentric disks arise in such astrophysical contexts as tidal disruption events, but it is unknown whether the magnetorotational instability (MRI), which powers accretion in circular disks, operates in eccentric disks as well. We examine the linear evolution of unstratified, incompressible MRI in an eccentric disk orbiting a point mass. We consider vertical modes of wavenumber $k$ on a background flow with uniform eccentricity $e$ and vertical Alfvén speed $v_{\mathrm{A}}$ along an orbit with mean motion $n$. We find two mode families, one with dominant magnetic components, the other with dominant velocity components; the former is unstable at $(1-e{)}^3{f}^2\lesssim 3$, where $f\equiv k{v}_{\mathrm{A}}/n$, the latter at $e\gtrsim 0.8$. For $f^2\lesssim 3$, MRI behaves much like in circular disks, but the growth per orbit declines slowly with increasing $e$; for $f^2\gtrsim 3$, modes grow by parametric amplification, which is resonant for $0<e\ll 1$. MRI growth and the attendant angular momentum and energy transport happen chiefly near pericenter, where orbital shear dominates magnetic tension.

13 pages, 6 figures, 2 appendices, accepted by ApJ

References in corpus (4)

• General Relativistic Hydrodynamic Simulation of Accretion Flow from a Stellar Tidal Disruption
• Long-term stream evolution in tidal disruption events
• Local and global dynamics of eccentric astrophysical discs
• Hydrodynamic instability in eccentric astrophysical discs

Cited by in corpus (22)

• Self-intersection of the Fallback Stream in Tidal Disruption Events
• Stellar Tidal Disruption Events in General Relativity
• A Survey of Disc Thickness and Viscosity in Circumbinary Accretion: Binary Evolution, Variability, and Disc Morphology
• The Physics of Accretion Discs, Winds And Jets in Tidal Disruption Events
• Tidal Disruption of a Main-Sequence Star by an Intermediate-Mass Black Hole: A Bright Decade
• Eccentric Tidal Disruption Event Disks around Supermassive Black Holes: Dynamics and Thermal Emission
• Tidal Disruptions of Main Sequence Stars -- V. The Varieties of Disruptions
• Measuring black hole masses from tidal disruption events and testing the $M_{\mathrm{BH}}-{\sigma }_{\ast }$ relation
• Light Curves of Partial Tidal Disruption Events
• The nozzle shock in tidal disruption events
• Elliptical accretion disk as a model for tidal disruption events
• Tidal Disruption Event Disks around Supermassive Black Holes: Disk Warp and Inclination Evolution
• HFQPOs and discoseismic mode excitation in eccentric, relativistic discs. II. Magnetohydrodynamic simulations
• Eccentric Modes in Disks With Pressure and Self-Gravity
• Dynamical structure of highly eccentric discs with applications to tidal disruption events
• HFQPOs and discoseismic mode excitation in eccentric, relativistic discs. I. Hydrodynamic simulations
• Nonlinear evolution of the magnetorotational instability in eccentric disks
• Three-dimensional simulations of the magnetorotational instability in eccentric disks
• Future Simulations of Tidal Disruption Events
• Photometric and Kinematic Misalignments and Their Evolution Among Fast and Slow Rotators in the Illustris Simulation
• An Analytic, Fully Relativistic Framework for Tidal Disruption Event Streams in Schwarzschild Geometry
• Linear and nonlinear eccentric mode evolution in unstratified MHD discs