Impact of magneto-rotational instability on grain growth in protoplanetary disks: II. Increased grain collisional velocities

Abstract

Turbulence is the dominant source of collisional velocities for grains with a wide range of sizes in protoplanetary disks. So far, only Kolmogorov turbulence has been considered for calculating grain collisional velocities, despite the evidence that turbulence in protoplanetary disks may be non-Kolmogorov. In this work, we present calculations of grain collisional velocities for arbitrary turbulence models characterized by power-law spectra and determined by three dimensionless parameters: the slope of the kinetic energy spectrum, the slope of the auto-correlation time, and the Reynolds number. The implications of our results are illustrated by numerical simulations of the grain size evolution for different turbulence models. We find that for the modeled cases of the Iroshnikov-Kraichnan turbulence and the turbulence induced by the magneto-rotational instabilities, collisional velocities of small grains are much larger than those for the standard Kolmogorov turbulence. This leads to faster grain coagulation in the outer regions of protoplanetary disks, resulting in rapid increase of dust opacity in mm-wavelength and possibly promoting planet formation in very young disks.

Accepted by ApJ

References in corpus (9)

• Coagulation, fragmentation and radial motion of solid particles in protoplanetary disks
• Particle Stirring in Turbulent Gas Disks: Including Orbital Oscillations
• Closed-form expressions for particle relative velocities induced by turbulence
• The stickiness of micrometer-sized water-ice particles
• Dust size distributions in coagulation/fragmentation equilibrium: Numerical solutions and analytical fits
• The time evolution of dusty protoplanetary disc radii: observed and physical radii differ
• Particle dynamics in discs with turbulence generated by the vertical shear instability
• High Resolution Parameter Study of the Vertical Shear Instability
• Inhibited Coagulation of Micron-size Dust Due to the Electrostatic Barrier

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• Dust evolution during the protostellar collapse: influence on the coupling between the neutral gas and the magnetic field
• Massive Protostellar Disks as a Hot Laboratory of Silicate Grain Evolution
• Inefficient star formation in high Mach number environments II. Numerical simulations and comparison with analytical models
• Gas Phase Ions in Protoplanetary Disks from Collisions of Solids
• On the 3D time evolution of the dust size distribution in protostellar envelopes