Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flow

Abstract

The magnetorotational (MRI) dynamo has long been considered one of the possible drivers of turbulent angular momentum transport in astrophysical accretion disks. However, various numerical results suggest that this dynamo may be difficult to excite in the astrophysically relevant regime of magnetic Prandtl number (Pm) significantly smaller than unity, for reasons currently not well understood. The aim of this article is to present the first results of an ongoing numerical investigation of the role of both linear and nonlinear dissipative effects in this problem. Combining a parametric exploration and an energy analysis of incompressible nonlinear MRI dynamo cycles representative of the transitional dynamics in large aspect ratio shearing boxes, we find that turbulent magnetic diffusion makes the excitation and sustainment of this dynamo at moderate magnetic Reynolds number (Rm) increasingly difficult for decreasing Pm. This results in an increase in the critical Rm of the dynamo for increasing kinematic Reynolds number (Re), in agreement with earlier numerical results. Given its very generic nature, we argue that turbulent magnetic diffusion could be an important determinant of MRI dynamo excitation in disks, and may also limit the efficiency of angular momentum transport by MRI turbulence in low Pm regimes.

arXiv comment7 pages, 6 figures

References in corpus (18)

• Sustained Magnetorotational Turbulence in Local Simulations of Stratified Disks with Zero Net Magnetic Flux
• 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
• Direct magnetic field detection in the innermost regions of an accretion disc
• The Nuclear Stellar Disk in Andromeda: A Fossil from the Era of Black Hole Growth
• Resistivity-driven State Changes in Vertically Stratified Accretion Disks
• On the Magnetic Prandtl Number Behavior of Accretion Disks
• A self-sustaining nonlinear dynamo process in Keplerian shear flows
• On Self-Sustained Dynamo Cycles in Accretion Discs
• Global bifurcations to subcritical magnetorotational dynamo action in Keplerian shear flow
• Magnetorotational instability driven dynamos at low magnetic Prandtl numbers
• Periodic magnetorotational dynamo action as a prototype of nonlinear magnetic field generation in shear flows
• Magnetorotational turbulence transports angular momentum in stratified disks with low magnetic Prandtl number but magnetic Reynolds number above a critical value
• Symmetries, scaling laws and convergence in shearing-box simulations of MRI driven turbulence
• Direct Measurement of Effective Magnetic Diffusivity in Turbulent Flow of Liquid Sodium
• Subcritical dynamos in shear flows
• Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flow
• Accretion Disks and Dynamos: Toward a Unified Mean Field Theory

Cited by in corpus (24)

• Magneto-thermal Disk Wind from Protoplanetary Disks
• Dynamo theories
• Saturation of the magnetorotational instability in the unstratified shearing box with zero net flux: convergence in taller boxes
• Characterizing the mean-field dynamo in turbulent accretion disks
• On the self-sustained nature of large-scale motions in turbulent Couette flow
• Angular momentum transport and large eddy simulations in magnetorotational turbulence: the small Pm limit
• On the Nature of Magnetic Turbulence in Rotating, Shearing Flows
• Magnetorotational instability and dynamo action in gravitoturbulent astrophysical discs
• The influence of accretion disk thickness on the large-scale magnetic dynamo
• Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flow
• Magnetorotational dynamo chimeras. The missing link to turbulent accretion disk dynamo models?
• Large scale dynamo action precedes turbulence in shearing box simulations of the magnetorotational instability
• MRI turbulence in accretion discs at large magnetic Prandtl numbers
• Zero net flux MRI-turbulence in disks $-$ sustenance scheme and magnetic Prandtl number dependence
• Small-scale dynamos on the solar surface: dependence on magnetic Prandtl number
• Nonlinear transverse cascade and sustenance of MRI-turbulence in Keplerian disks with an azimuthal magnetic field
• The stress-pressure relationship in simulations of MRI-induced turbulence
• Magnetorotational Dynamo Action in the Shearing Box
• Magnetohydrodynamics of protoplanetary discs
• Sustained Turbulence in Differentially Rotating Magnetized Fluids at Low Magnetic Prandtl Number
• Magnetorotationally driven wind cycles in local disc models
• MRI turbulence in vertically stratified accretion discs at large magnetic Prandtl numbers
• A 2.5-dimensional viscous, resistive, advective magnetized accretion-outflow coupling in black hole systems: A higher order polynomial approximation. I
• MRI-driven $\alpha \Omega$ dynamo at high Pm numbers