On characterizing nonlocality and anisotropy for the magnetorotational instability

Abstract

The extent to which angular momentum transport in accretion discs is primarily local or non-local and what determines this is an important avenue of study for understanding accretion engines. Taking a step along this path, we analyze simulations of the magnetorotational instability (MRI) by calculating energy and stress power spectra in stratified isothermal shearing box simulations in several new ways. We divide our boxes in two regions, disc and corona where the disc is the MRI unstable region and corona is the magnetically dominated region. We calculate the fractional power in different quantities, including magnetic energy and Maxwell stresses and find that they are dominated by contributions from the lowest wave numbers. This is even more dramatic for the corona than the disc, suggesting that transport in the corona region is dominated by larger structures than the disc. By calculating averaged power spectra in one direction of $k$ space at a time, we also show that the MRI turbulence is strongly anisotropic on large scales when analyzed by this method, but isotropic on small scales. Although the shearing box itself is meant to represent a local section of an accretion disc, the fact that the stress and energy are dominated by the largest scales highlights that the locality is not captured within the box. This helps to quantify the intuitive importance of global simulations for addressing the question of locality of transport, for which similar analyses can be performed.

arXiv comment7 pages, 4 figures, 1 table, version accepted by MNRAS

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Cited by in corpus (14)

• Resolution Dependence of Magnetorotational Turbulence in the Isothermal Stratified Shearing Box
• Conservative GRMHD Simulations of Moderately Thin, Tilted Accretion Disks
• Large scale dynamo action precedes turbulence in shearing box simulations of the magnetorotational instability
• On the Anisotropic Nature of MRI-Driven Turbulence in Astrophysical Disks
• Impact of magneto-rotational instability on grain growth in protoplanetary disks: I. Relevant turbulence properties
• Motivation and challenge to capture both large scale and local transport in next generation accretion theory
• Nonlinear transverse cascade and sustenance of MRI-turbulence in Keplerian disks with an azimuthal magnetic field
• Active modes and dynamical balances in MRI-turbulence of Keplerian disks with a net vertical magnetic field
• Radially Dependent Large Scale Dynamos in Global Cylindrical Shear Flows and the Local Cartesian Limit
• Sensitivity of the Magnetorotational Instability to the shear parameter in stratified simulations
• Universal small-scale structure in turbulence driven by magnetorotational instability
• A heuristic model for MRI turbulent stresses in Hall MHD
• MRI turbulence in vertically stratified accretion discs at large magnetic Prandtl numbers
• Exploring helical dynamos with machine learning