Energy partition between Alfvénic and compressive fluctuations in magnetorotational turbulence with near-azimuthal mean magnetic field

Abstract

The theory of magnetohydrodynamic (MHD) turbulence predicts that Alfvénic and slow-mode-like compressive fluctuations are energetically decoupled at small scales in the inertial range. The partition of energy between these fluctuations determines the nature of dissipation, which, in many astrophysical systems, happens on scales where plasma is collisionless. However, when the magnetorotational instability (MRI) drives the turbulence, it is difficult to resolve numerically the scale at which both types of fluctuations start to be decoupled because the MRI energy injection occurs in a broad range of wavenumbers, and both types of fluctuations are usually expected to be coupled even at relatively small scales. In this study, we focus on collisional MRI turbulence threaded by a near-azimuthal mean magnetic field, which is naturally produced by the differential rotation of a disc. We show that, in such a case, the decoupling scales are reachable using a reduced MHD model that includes differential-rotation effects. In our reduced MHD model, the Alfvénic and compressive fluctuations are coupled only through the linear terms that are proportional to the angular velocity of the accretion disc. We numerically solve for the turbulence in this model and show that the Alfvénic and compressive fluctuations are decoupled at the small scales of our simulations as the nonlinear energy transfer dominates the linear coupling below the MRI-injection scale. In the decoupling scales, the energy flux of compressive fluctuations contained in the small scales is almost double that of Alfvénic fluctuations. Finally, we discuss the application of this result to prescriptions of ion-to-electron heating ratio in hot accretion flows.

arXiv commentAccepted for publication in Journal of Plasma Physics

References in corpus (47)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• Advection-Dominated Accretion: Underfed Black Holes and Neutron Stars
• Astrophysical gyrokinetics: kinetic and fluid turbulent cascades in magnetized weakly collisional plasmas
• Compressible Magnetohydrodynamic Turbulence: mode coupling, scaling relations, anisotropy, new regime and astrophysical implications
• MHD Turbulence Revisited
• Compressible Sub-Alfvenic MHD turbulence in Low-beta Plasmas
• Perpendicular Ion Heating by Low-Frequency Alfven-Wave Turbulence in the Solar Wind
• Disk Winds Driven by Magnetorotational Instability and Dispersal of Proto-Planetary Disks
• Gyrokinetic Simulations of Solar Wind Turbulence from Ion to Electron Scales
• Shell to shell energy transfer in MHD, Part I: steady state turbulence
• Electron Heating in Hot Accretion Flows
• Shearing Box Simulations of the MRI in a Collisionless Plasma
• The excitation of spiral density waves through turbulent fluctuations in accretion discs II: Numerical Simulations with MRI driven turbulence
• A prescription for the turbulent heating of astrophysical plasmas
• Two-temperature, Magnetically Arrested Disc simulations of the jet from the supermassive black hole in M87
• The role of electron heating physics in images and variability of the Galactic Centre black hole Sagittarius A*
• Thermal disequilibration of ions and electrons by collisionless plasma turbulence
• MHD Simulations of Global Accretion Disks with Vertical Magnetic Fields
• The Magnetorotational Instability in a Collisionless Plasma
• Critical balance in magnetohydrodynamic, rotating and stratified turbulence: towards a universal scaling conjecture
• Electron and ion energization in relativistic plasma turbulence
• Multiscale nature of the dissipation range in gyrokinetic simulations of Alfvénic turbulence
• Magnetorotational Turbulence and Dynamo in a Collisionless Plasma
• Magnetohydrodynamic Instabilities in Shearing, Rotating, Stratified Winds and Disks
• Hybrid-Kinetic Simulations of Ion Heating in Alfvénic Turbulence
• Energy transfer in compressible magnetohydrodynamic turbulence
• An Extended Magnetohydrodynamics Model for Relativistic Weakly Collisional Plasmas
• Evolution of Accretion Discs around a Kerr Black Hole using Extended Magnetohydrodynamics
• How important is non-ideal physics in simulations of sub-Eddington accretion onto spinning black holes?
• Astrophysical gyrokinetics: Turbulence in pressure-anisotropic plasmas at ion scales and beyond
• Nonlinear energy transfers in accretion discs MRI turbulence. I-Net vertical field case
• Constraints on ion vs. electron heating by plasma turbulence at low beta
• Stochastic Particle Acceleration in Turbulence Generated by the Magnetorotational Instability
• Fluctuation dynamo in a weakly collisional plasma
• On the Nature of Magnetic Turbulence in Rotating, Shearing Flows
• Revisiting linear dynamics of non-axisymmetric perturbations in weakly magnetized accretion discs
• Nonmodal growth of the magnetorotational instability
• Particle energization in relativistic plasma turbulence: solenoidal versus compressive driving
• Energy Partition between Ion and Electron of Collisionless Magnetic Reconnection
• Magnetorotational instability: nonmodal growth and the relationship of global modes to the shearing box
• grim: A Flexible, Conservative Scheme for Relativistic Fluid Theories
• Shearing-box simulations of MRI-driven turbulence in weakly collisional accretion discs
• Particle Diffusion and Acceleration in Magnetorotational Instability Turbulence
• Pressure-anisotropy-induced nonlinearities in the kinetic magnetorotational instability
• Stability of compressible reduced magnetohydrodynamic equilibria - analogy with magnetorotational instability
• Universal small-scale structure in turbulence driven by magnetorotational instability
• Calliope: Pseudospectral shearing magnetohydrodynamics code with a pencil decomposition

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• MHD in a cylindrical shearing box II: Intermittent Bursts and Substructures in MRI Turbulence
• First-principles measurement of ion and electron energization in collisionless accretion flow
• Fully kinetic shearing-box simulations of magnetorotational turbulence in 2D and 3D. I. Pair plasmas