ZONAL FLOWS AND LONG-LIVED AXISYMMETRIC PRESSURE BUMPS IN MAGNETOROTATIONAL TURBULENCE

By Anders Johansen, A. Youdin, H. F. L. Observatory, Leiden University, Cita, Mpia. 2008

254 citations recorded by the source corpus.

We study the behavior of magnetorotational turbulence in shearing box simulations with a radial and azimuthal extent up to 10 scale heights. Maxwell and Reynolds stresses are found to increase by more than a factor of 2 when increasing the box size beyond two scale heights in the radial direction. Further increase of the box size has little or no effect on the statistical properties of the turbulence. An inverse cascade excites magnetic field structures at the largest scales of the box. The corresponding 10% variation in the Maxwell stress launches a zonal flow of alternating sub- and super-Keplerian velocity. This, in turn, generates a banded density structure in geostrophic balance between pressure and Coriolis forces. We present a simplified model for the appearance of zonal flows, in which stochastic forcing by the magnetic tension on short timescales creates zonal flow structures with lifetimes of several tens of orbits. We experiment with various improved shearing box algorithms to reduce the numerical diffusivity introduced by the supersonic shear flow. While a standard finite difference advection scheme shows signs of a suppression of turbulent activity near the edges of the box, this problem is eliminated by a new method where the Keplerian shear advection is advanced in time by interpolation in Fourier space.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/20cade463b78a36cbad847f1ffe10837b6333ca8

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Citations in the corpus

Gravitational Instabilities in Circumstellar Disks (2016, background): “Spiral arms in a self-gravitating disk are an excellent candidate for producing pressure maxima that can enhance particle growth, much like MRI turbulence for the Streaming Instability (Johansen et al. 2009).”
Ring shaped dust accumulation in transition disks (2012, background): “One possible solution to prevent the rapid inward drift and trap dust particles, is to consider pressure bumps (Klahr & Henning 1997; Fromang & Nelson 2005; Brauer et al. 2008; Johansen et al. 2009; Pinilla et al. 2012).”
THE RUNTS OF THE LITTER: WHY PLANETS FORMED THROUGH GRAVITATIONAL INSTABILITY CAN ONLY BE FAILED BINARY STARS (2009, background): “More restrictively this requires that other local transport mechanisms such as the MRI be weaker than currently predicted by simulations—they produce α ∼ 10−2 at least in disks with a net magnetic flux (Fleming et al. 2000; Fromang et al. 2007; Johansen et al. 2009).”
Trapping dust particles in the outer regions of protoplanetary disks (2011, methodology): “However, these can be a good approximation of long-lived, azimuthally extended pressure bumps, that can be e.g. the result of MHD effects (see Johansen et al. 2009; Dzyurkevich et al. 2010).”
RINGED SUBSTRUCTURE AND A GAP AT 1 au IN THE NEAREST PROTOPLANETARY DISK (2016, background): “Magnetized disks may exhibit radial pressure variations known as zonal flows (Johansen et al. 2009), natural outcomes of the turbulence driven by the magnetorotational instability (Balbus & Hawley 1991).”
SUSTAINED MAGNETOROTATIONAL TURBULENCE IN LOCAL SIMULATIONS OF STRATIFIED DISKS WITH ZERO NET MAGNETIC FLUX (2009, background): “This is similar to other “butterfly diagrams” seen in previous shearing box calculations of stratified domains (Brandenburg et al. 1995; Stone et al. 1996; Turner 2004; Johansen et al. 2009; Suzuki & Inutsuka 2009).”
THE MASS AND SIZE DISTRIBUTION OF PLANETESIMALS FORMED BY THE STREAMING INSTABILITY. I. THE ROLE OF SELF-GRAVITY (2015, methodology): “Three-dimensional calculations that include the mutual gravitational forces between particles have been used to study how planetesimals form (Johansen et al. 2007, 2009b, 2011, 2012, 2015).”
Concentrating small particles in protoplanetary disks through the streaming instability (2016, methodology): “The former includes long-lived local pressure maxima (Whipple 1972; Johansen et al. 2009a; Bai & Stone 2014) or vortices (Barge & Sommeria 1995; Bracco et al. 1999; Klahr & Hubbard 2014; Lyra 2014), in which solids passively follow the underlying flow of gas by friction.”
The Disk Substructures at High Angular Resolution Project (DSHARP). I. Motivation, Sample, Calibration, and Overview (2018, background): “…(disk-averaged) pressure scale height, hP (where hP /r ≈ 0.1; Kenyon & Hartmann 1987), a benchmark size that is directly related to the P deviations generated by turbulent zonal flows (e.g., Johansen et al. 2009), vortices (e.g., Barge & Sommeria 1995), or planetary gaps (e.g., Bryden et al. 1999).”
IMPLEMENTATION OF THE SHEARING BOX APPROXIMATION IN ATHENA (2010, methodology): “Most ofthe simulations of the MRI presented to date have used operatorsplit methods like ZEUS (e.g. HGB; Stone et al. 1996), or simple finite-difference methods like the PENCIL code (e.g. Johansen et al. 2009).”
Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region (2018, background): “Other magnetohydrodynamic effects, including zonal flows (e.g., Johansen et al. 2009), could also play a role in gas evolution and gas pressure distribution.”
Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations (2014, background): “4 (left), shows very similar characteristics as the classical zonal flow found in local-box simulations (Johansen et al. 2009; Dittrich et al. 2013) and global simulations (Dzyurkevich et al. 2010; Uribe et al. 2011).”
LOCAL STUDY OF ACCRETION DISKS WITH A STRONG VERTICAL MAGNETIC FIELD: MAGNETOROTATIONAL INSTABILITY AND DISK OUTFLOW (2012, background): “The relatively large horizontal box size is necessary to properly capture the mesoscale structures of the MRI turbulence such as the zonal flow (Johansen et al. 2009; Simon et al. 2012).”
Dust Evolution and the Formation of Planetesimals (2016, background): “The high mass loading in the gas could be an additional factor needed to reach very high densities, as the turbulent diffusion of the gas is drastically reduced in such particle dominated flows (Johansen et al. 2009).”
Rapid growth of gas-giant cores by pebble accretion (2012, background): “On the other hand, one can circumvent this so-called meter barrier with turbulence induced by the magnetorotational instability (MRI, Balbus & Hawley 1991), which excites local pressure bumps, ideal regions for dust particle trapping and growth (Whipple 1972; Johansen et al. 2009a).”
Ice Condensation as a Planet Formation Mechanism (2013, background): “Particles also concentrate in long-lived vortices (Barge & Sommeria, 1995; Klahr & Bodenheimer, 2003) and pressure bumps (Johansen et al., 2009) excited in the turbulent flow.”
Dust size distributions in coagulation/fragmentation equilibrium: numerical solutions and analytical fits (2010, background): “Possible solutions to reduce the drift rate include bumps in the radial pressure profile (see Kretke & Lin 2007; Brauer et al. 2008b; Cossins et al. 2009) or zonal flows (see Johansen et al. 2009).”