MRI-driven dynamo at very high magnetic Prandtl numbers

Abstract

The dynamo driven by the magnetorotational instability (MRI) is believed to play an important role in the dynamics of accretion discs and may also explain the origin of the extreme magnetic fields present in magnetars. Its saturation level is an important open question known to be particularly sensitive to the diffusive processes through the magnetic Prandtl number Pm (the ratio of viscosity to resistivity). Despite its relevance to proto-neutron stars and neutron star merger remnants, the numerically challenging regime of high Pm is still largely unknown. Using zero-net flux shearing box simulations in the incompressible approximation, we studied MRI-driven dynamos at unprecedentedly high values of Pm reaching 256. The simulations show that the stress and turbulent energies are proportional to Pm up to moderately high values ($\mathrm{Pm}\sim 50$). At higher Pm, they transition to a new regime consistent with a plateau independent of Pm for $\mathrm{Pm}\gtrsim 100$. This trend is independent of the Reynolds number, which may suggest an asymptotic regime where the energy injection and dissipation are independent of the diffusive processes. Interestingly, large values of Pm not only lead to intense small-scale magnetic fields but also to a more efficient dynamo at the largest scales of the box.

arXiv comment8 pages, 5 figures, accepted for publication in MNRAS

References in corpus (41)

• The Proto-Magnetar Model for Gamma-Ray Bursts
• Bright Supernovae from Magnetar Birth
• Simulations of small-scale turbulent dynamo
• The Magnetorotational Instability in Core Collapse Supernova Explosions
• A large scale dynamo and magnetoturbulence in rapidly rotating core-collapse supernovae
• How mergers magnetise massive stars
• 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
• Semi-global simulations of the magneto-rotational instability in core collapse supernovae
• Modelling of isolated radio pulsars and magnetars on the fossil field hypothesis
• Special Relativistic Simulations of Magnetically-dominated Jets in Collapsing Massive Stars
• On the relevance of subcritical hydrodynamic turbulence to accretion disk transport
• A magnetar engine for short GRBs and kilonovae
• Magnetorotational Explosion of A Massive Star Supported by Neutrino Heating in General Relativistic Three Dimensional Simulations
• Magnetar formation through a convective dynamo in protoneutron stars
• On the Magnetic Prandtl Number Behavior of Accretion Disks
• Saturation of the magnetorotational instability in the unstratified shearing box with zero net flux: convergence in taller boxes
• The signature of the magnetorotational instability in the Reynolds and Maxwell stress tensors in accretion discs
• Viscous and Resistive Effects on the MRI with a Net Toroidal Field
• MRI-driven turbulent transport: the role of dissipation, channel modes and their parasites
• The impact of non-dipolar magnetic fields in core-collapse supernovae
• A global model of the magnetorotational instability in protoneutron stars
• Neutrino viscosity and drag: impact on the magnetorotational instability in protoneutron stars
• Numerical simulations of the magnetorotational instability in protoneutron stars: I. Influence of buoyancy
• Three-dimensional core-collapse supernovae with complex magnetic structures: I. Explosion dynamics
• Local Simulations of the Magneto-rotational Instability in Core-Collapse Supernovae
• Nonlinear energy transfers in accretion discs MRI turbulence. I-Net vertical field case
• The Effect of Neutrino Radiation on Magnetorotational Instability in Proto-Neutron Stars
• Angular momentum transport and large eddy simulations in magnetorotational turbulence: the small Pm limit
• MRI-driven $\alpha -\Omega$ dynamos in protoneutron stars
• Magnetorotational instability in neutron star mergers: impact of neutrinos
• Gravitational wave signature of proto-neutron star convection: I. MHD numerical simulations
• Magnetorotational dynamo chimeras. The missing link to turbulent accretion disk dynamo models?
• Keldysh effective action theory for universal physics in spin-1/2 Kondo dots
• An accretion disc instability induced by a temperature sensitive $\alpha$ parameter
• Zero net flux MRI-turbulence in disks $-$ sustenance scheme and magnetic Prandtl number dependence
• Microphysical dissipation, turbulence and magnetic fields in hyper-accreting discs
• Magnetorotational Dynamo Action in the Shearing Box
• Generating neutron-star magnetic fields: three dynamo phases
• Demonstration of a magnetic Prandtl number disc instability from first principles
• Neutrino-Dominated Accretion Flows with Magnetic Prandtl Number-Dependent MRI-driven Turbulence

Cited by in corpus (21)

• End-to-end kilonova models of neutron-star mergers with delayed black-hole formation
• Resistive relativistic MHD simulations of astrophysical jets
• Three-dimensional core-collapse supernovae with complex magnetic structures: II. Rotational instabilities and multi-messenger signatures
• A new scenario for magnetar formation: Tayler-Spruit dynamo in a proto-neutron star spun up by fallback
• Numerical simulations of the Tayler-Spruit dynamo in proto-magnetars
• MRI turbulence in accretion discs at large magnetic Prandtl numbers
• Effect of stellar rotation on the development of post-shock instabilities during core-collapse supernovae
• Tayler-Spruit dynamo in stably stratified rotating fluids: Application to proto-magnetars
• Magnetar central engines in gamma-ray busts follow the universal relation of accreting magnetic stars
• MRI turbulence in vertically stratified accretion discs at large magnetic Prandtl numbers
• Lorentz force mediation of turbulent dynamo transitions
• Confronting the neutron star population with inverse cascades
• Turbulent magnetic decay controlled by two conserved quantities
• MHD in a cylindrical shearing box II: Intermittent Bursts and Substructures in MRI Turbulence
• Helical and nonhelical large-scale dynamos in thin accretion discs
• Local magneto-shear instability in Newtonian gravity
• Evolution of proto-neutron stars to pulsars, magnetars and central compact objects
• MRI-driven $\alpha \Omega$ dynamo at high Pm numbers
• Probing millisecond magnetar formation in binary neutron star mergers through X-ray follow-up of gravitational wave alerts
• Large $\mathrm{Pm}$ small-scale kinematic dynamo in protoneutron stars
• Fast giant flares in discs around supermassive black holes