Sustained magnetorotational turbulence in local simulations of stratified disks with zero net magnetic flux

Shane W. Davis, James M. Stone, Martin E. Pessah

Research output: Contribution to journalArticle

179 Scopus citations

Abstract

We examine the effects of density stratification on magnetohydrodynamic turbulence driven by the magnetorotational instability in local simulations that adopt the shearing box approximation. Our primary result is that, even in the absence of explicit dissipation, the addition of vertical gravity leads to convergence in the turbulent energy densities and stresses as the resolution increases, contrary to results for zero net flux, unstratified boxes. The ratio of total stress to midplane pressure has a mean of 0.01, although there can be significant fluctuations on long (≳50orbits) timescales. We find that the time-averaged stresses are largely insensitive to both the radial and the vertical aspect ratios of our simulation domain. For simulations with explicit dissipation, we find that stratification extends the range of Reynolds and magnetic Prandtl numbers for which turbulence is sustained, but the behavior of such simulations on long timescales is highly variable. Confirming the results of previous studies, we find oscillations in the large-scale toroidal field with periods of ∼ 10 orbits and describe the dynamo process that underlies these cycles. We discuss possible origins for the different convergence properties of the stratified and unstratified domains and identify open questions that remain to be answered.

Original languageEnglish (US)
Pages (from-to)52-65
Number of pages14
JournalAstrophysical Journal
Volume713
Issue number1
DOIs
StatePublished - Jan 1 2010

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Accretion, accretion disks
  • Hydrodynamics
  • Methods: numerical

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