Impact of magneto-rotational instability on grain growth in protoplanetary disks: I. Relevant turbulence properties

Abstract

Turbulence in the protoplanetary disks induces collisions between dust grains, and thus facilitates grain growth. We investigate the two fundamental assumptions of the turbulence in obtaining grain collisional velocities -- the kinetic energy spectrum and the turbulence autocorrelation time -- in the context of the turbulence generated by the magneto-rotational instability (MRI). We carry out numerical simulations of the MRI as well as driven turbulence, for a range of physical and numerical parameters. We find that the convergence of the turbulence $\alpha$-parameter does not necessarily imply the convergence of the energy spectrum. The MRI turbulence is largely solenoidal, for which we observe a persistent kinetic energy spectrum of $k^{-4/3}$. The same is obtained for solenoidal driven turbulence with and without magnetic field, over more than 1 dex near the dissipation scale. This power-law slope appears to be converged in terms of numerical resolution, and to be due to the bottleneck effect. The kinetic energy in the MRI turbulence peaks at the fastest growing mode of the MRI. In contrast, the magnetic energy peaks at the dissipation scale. The magnetic energy spectrum in the MRI turbulence does not show a clear power-law range, and is almost constant over approximately 1 dex near the dissipation scale. The turbulence autocorrelation time is nearly constant at large scales, limited by the shearing timescale, and shows a power-law drop close to $k^{-1}$ at small scales, with a slope steeper than that of the eddy crossing time. The deviation from the standard picture of the Kolmogorov turbulence with the injection scale at the disk scale height can potentially have a significant impact on the grain collisional velocities.

Accepted by ApJ

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Cited by in corpus (13)

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• Turbulence in outer protoplanetary disks: MRI or VSI?
• Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics
• As a matter of tension -- kinetic energy spectra in MHD turbulence
• Impact of magneto-rotational instability on grain growth in protoplanetary disks: II. Increased grain collisional velocities
• Dust grains cannot grow to millimeter sizes in protostellar envelopes
• Simulating the magnetorotational instability on a moving mesh with the shearing box approximation
• Large-scale turbulent driving regulates star formation in high-redshift gas-rich galaxies II: Influence of the magnetic field and the turbulent compressive fraction
• Coagulation-Fragmentation Equilibrium for Charged Dust: Abundance of Submicron Grains Increases Dramatically in Protoplanetary Disks
• On the 3D time evolution of the dust size distribution in protostellar envelopes
• First-principles measurement of ion and electron energization in collisionless accretion flow
• Thermal damping of Weak Magnetosonic Turbulence in the Interstellar Medium