SUSTAINED MAGNETOROTATIONAL TURBULENCE IN LOCAL SIMULATIONS OF STRATIFIED DISKS WITH ZERO NET MAGNETIC FLUX

By S. Davis, James M. Stone, M. Pessah. 2009

218 citations recorded by the source corpus.

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 (≳50 orbits) 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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f6b7c97d4e1f00d8bc23d250a955baa4995829b0

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In Astronomy and Astrophysics

1. Ramesh Narayan
2. Xue-Ning Bai
3. A. Tchekhovskoy
4. B. Metzger
5. J. McKinney
6. F. Yuan
7. D. Wilner
8. James M. Stone

Citations in the corpus

• LOCAL STUDY OF ACCRETION DISKS WITH A STRONG VERTICAL MAGNETIC FIELD: MAGNETOROTATIONAL INSTABILITY AND DISK OUTFLOW (2012, background): “…= 104 to 〈α〉 ≈ 1.0 for β0 = 100, The ratio of 〈αMax〉 to 〈αRey〉 increases from about 4 for β0 = 10 4, which is similar to that in zero net vertical flux simulations (e.g., Davis et al. 2010), to about 7 for β0 = 10 2, which is mainly due to an increasing contribution from the mean (rather than…”
• EFFECT OF AMBIPOLAR DIFFUSION ON THE NONLINEAR EVOLUTION OF MAGNETOROTATIONAL INSTABILITY IN WEAKLY IONIZED DISKS (2011, methodology): “Non-ideal MHD terms including Ohmic resistivity (Davis et al. 2010), the Hall term (in progress) and AD (this paper) have been developed for Athena.”
• ASSESSING QUANTITATIVE RESULTS IN ACCRETION SIMULATIONS: FROM LOCAL TO GLOBAL (2011, methodology): “Table 1 presents some time-averaged data collected from Simon et al. (2011), Shi et al. (2010), Davis et al. (2010), and Guan & Gammie (2011) along with two unpublished 8 and 16 zones/H simulations (Simon, private communication).”
• Signatures of hypermassive neutron star lifetimes on r-process nucleosynthesis in the disc ejecta from neutron star mergers (2017, result): “These choices are motivated to be broadly compatible with results from dynamical merger simulations (e.g., Ruffert et al. 1997; Oechslin & Janka 2006; Foucart et al. 2016a) and from studies of angular momentum transport in fully-ionized accretion disks (e.g., Davis et al. 2010).”
• IMPLEMENTATION OF THE SHEARING BOX APPROXIMATION IN ATHENA (2010, methodology): “TheC version is also being used for new studies of the MRI (Davis et al. 2010).”
• Hot Accretion Flows Around Black Holes (2014, background): “Interestingly, the uncertainty in the value of α is eliminated if shearing box simulations include vertical stratification to mimic the effect of vertical disk gravity (Davis et al. 2010, Bai & Stone 2013).”
• Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks (2020, background): “Additionally, when the net magnetic flux in the accretion disk is relatively small, turbulence resulting from the MRI can produce magnetic fields with alternating polarities prone to reconnection (Davis et al. 2010; Zhu & Stone 2018).”
• EMPIRICAL CONSTRAINTS ON TURBULENCE IN PROTOPLANETARY ACCRETION DISKS (2010, methodology): “Using reported values of the relevant simulation parameters from Davis et al. (2010), α ∼ 3(vturb/cs)2 for a face-on disk, and α ∼ 1.5(vturb/cs)2 for an edge-on disk.”
• A Reconnection Switch to Trigger gamma-Ray Burst Jet Dissipation (2010, background): “For example, an accretion disc could have m = 0.1 (Davis et al. 2010).”
• Forming Planetesimals in Solar and Extrasolar Nebulae (2009, background): “∂(ln ρ)/∂z ∼ −1/hp and |∂vφ/∂z| ∼ ηvK/hp, criterion (30) implies that the KHI prevents the sublayer from having a thickness less than”
• WIND-DRIVEN ACCRETION IN PROTOPLANETARY DISKS. I. SUPPRESSION OF THE MAGNETOROTATIONAL INSTABILITY AND LAUNCHING OF THE MAGNETOCENTRIFUGAL WIND (2013, methodology): “…most vertically stratified shearing-box simulations to date adopt a zero net vertical magnetic flux field geometry (e.g., Stone et al. 1996; Shi et al. 2010; Davis et al. 2010) and we will show that such field geometry would make the strength of the MRI turbulence diminishingly small due to AD.”
• General relativistic magnetohydrodynamic simulations of magnetically choked accretion flows around black holes (2012, background): “Disk mode oscillations may cause either HF or LF QPOs (Reynolds & Miller 2009; O’Neill et al. 2009, 2011), disk precession causes LFQPOs in GRMHD simulations of tilted disks (Dexter & Fragile 2011), and dynamo field oscillations in local MHD simulations show LFQPOs (Davis et al. 2010; Guan & Gammie ”
• A GLOBAL THREE-DIMENSIONAL RADIATION MAGNETO-HYDRODYNAMIC SIMULATION OF SUPER-EDDINGTON ACCRETION DISKS (2014, unknown): “This so called butterfly diagram has been observed widely in local shearing box (Stone et al. 1996; Miller & Stone 2000; Shi et al. 2010; Davis et al. 2010; Jiang et al. 2014b) and global simulations (O’Neill et al. 2011).”
• Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations (2014, background): “However, stratified simulations need to include the dynamo effect, which can generate a temporal small net flux that could sustain the turbulence (Davis et al. 2010; Gressel 2010; Flock et al. 2012a).”