Skip to main content
OSTI.GOVU.S. Department of Energy Office of Scientific and Technical Information
U.S. Department of Energy
Office of Scientific and Technical Information
 

Large-scale dynamo action precedes turbulence in shearing box simulations of the magnetorotational instability

Journal Article · · Monthly Notices of the Royal Astronomical Society
 [1];  [1];  [2]
  1. Princeton Univ., Princeton, NJ (United States)
  2. Univ. of Rochester, Rochester, NY (United States)
+ Show Author Affiliations
Here, we study the dynamo generation (exponential growth) of large-scale (planar averaged) fields in unstratified shearing box simulations of the magnetorotational instability (MRI). In contrast to previous studies restricted to horizontal (x–y) averaging, we also demonstrate the presence of large-scale fields when vertical (y–z) averaging is employed instead. By computing space–time planar averaged fields and power spectra, we find large-scale dynamo action in the early MRI growth phase – a previously unidentified feature. Non-axisymmetric linear MRI modes with low horizontal wavenumbers and vertical wavenumbers near that of expected maximal growth, amplify the large-scale fields exponentially before turbulence and high wavenumber fluctuations arise. Thus the large-scale dynamo requires only linear fluctuations but not non-linear turbulence (as defined by mode–mode coupling). Vertical averaging also allows for monitoring the evolution of the large-scale vertical field and we find that a feedback from horizontal low wavenumber MRI modes provides a clue as to why the large-scale vertical field sustains against turbulent diffusion in the non-linear saturation regime. We compute the terms in the mean field equations to identify the individual contributions to large-scale field growth for both types of averaging. The large-scale fields obtained from vertical averaging are found to compare well with global simulations and quasi-linear analytical analysis from a previous study by Ebrahimi & Blackman. We discuss the potential implications of these new results for understanding the large-scale MRI dynamo saturation and turbulence.
Research Organization:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
SC0012467
OSTI ID:
1332518
Journal Information:
Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 1 Vol. 462; ISSN 0035-8711
Publisher:
Royal Astronomical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

References (34)

A Local Model for Angular Momentum Transport in Accretion Disks Driven by the Magnetorotational Instability text January 2006
Astrophysical magnetic fields and nonlinear dynamo theory journal October 2005
Motivation and challenge to capture both large-scale and local transport in next generation accretion theory journal August 2015
Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flow journal February 2015
Magnetorotational instability in electrically driven flow of liquid metal: Spectral analysis of global modes journal December 2006
The Stability of Non-Dissipative Couette flow in Hydromagnetics journal February 1960
Local simulations of planetary rings journal March 1988
A powerful local shear instability in weakly magnetized disks. I - Linear analysis. II - Nonlinear evolution journal July 1991
The spectrum of random magnetic fields in the mean field dynamo theory of the Galactic magnetic field journal September 1992
A Powerful Local Shear Instability in Weakly Magnetized Disks. IV. Nonaxisymmetric Perturbations journal November 1992
Parasitic instabilities in magnetized, differentially rotating disks journal September 1994
Dynamo-generated Turbulence and Large-Scale Magnetic Fields in a Keplerian Shear Flow journal June 1995
Three-dimensional Magnetohydrodynamical Simulations of Vertically Stratified Accretion Disks journal May 1996
The Saturation Limit of the Magnetorotational Instability journal April 2009
Saturation of Magnetorotational Instability Through Magnetic Field Generation journal May 2009
Sustained Magnetorotational Turbulence in Local Simulations of Stratified Disks with zero net Magnetic flux journal March 2010
Radially Extended, Stratified, Local Models of Isothermal Disks journal January 2011
Resistivity-Driven State Changes in Vertically Stratified Accretion Disks journal March 2011
Global Simulations of Accretion Disks. i. Convergence and Comparisons with Local Models journal April 2012
Characterizing the Mean-Field Dynamo in Turbulent Accretion Disks journal August 2015
Fluctuation dynamos and their Faraday rotation signatures journal January 2013
On characterizing non-locality and anisotropy for the magnetorotational instability journal May 2014
Saturation of the magnetorotational instability in the unstratified shearing box with zero net flux: convergence in taller boxes journal December 2015
A unified large/small-scale dynamo in helical turbulence journal May 2016
Radially dependent large-scale dynamos in global cylindrical shear flows and the local cartesian limit journal March 2016
Simulations of nonhelical hydromagnetic turbulence journal July 2004
Periodic magnetorotational dynamo action as a prototype of nonlinear magnetic-field generation in shear flows journal September 2011
Electromotive force due to magnetohydrodynamic fluctuations in sheared rotating turbulence journal November 2015
Helicity-Flux-Driven α Effect in Laboratory and Astrophysical Plasmas journal March 2014
Self-Sustaining Nonlinear Dynamo Process in Keplerian Shear Flows journal June 2007
The signature of the magnetorotational instability in the Reynolds and Maxwell stress tensors in accretion discs journal October 2006
Localized magnetorotational instability and its role in the accretion disc dynamo journal December 2008
A mean-field approach to the propagation of field patterns in stratified magnetorotational turbulence journal March 2010
Magnetorotational instability driven dynamos at low magnetic Prandtl numbers: MRI-driven dynamos at low Pm journal February 2011

Cited By (6)

Derivation and precision of mean field electrodynamics with mesoscale fluctuations journal May 2018
Advances in mean-field dynamo theory and applications to astrophysical turbulence journal August 2018
Dynamo theories journal August 2019
Experimental confirmation of the standard magnetorotational instability mechanism with a spring-mass analogue journal January 2019
The magnetorotational instability prefers three dimensions
  • Oishi, Jeffrey S.; Vasil, Geoffrey M.; Baxter, Morgan
  • Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 476, Issue 2233 https://doi.org/10.1098/rspa.2019.0622
journal January 2020
Advances in mean-field dynamo theory and applications to astrophysical turbulence text January 2018

Similar Records

Evolution of the magnetorotational instability on initially tangled magnetic fields
Journal Article · Wed Aug 02 20:00:00 EDT 2017 · Monthly Notices of the Royal Astronomical Society · OSTI ID:1540613
THE SATURATION LIMIT OF THE MAGNETOROTATIONAL INSTABILITY
Journal Article · Fri May 01 00:00:00 EDT 2009 · Astrophysical Journal · OSTI ID:21300715
EFFECT OF AMBIPOLAR DIFFUSION ON THE NONLINEAR EVOLUTION OF MAGNETOROTATIONAL INSTABILITY IN WEAKLY IONIZED DISKS
Journal Article · Mon Aug 01 00:00:00 EDT 2011 · Astrophysical Journal · OSTI ID:21578213

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
MHD
accretion
accretion discs
dynamo
magnetic fields
turbulence