Dust Concentration at the Boundary Between Steady Super/Sub-Keplerian Flow Created by Inhomogeneous Growth of MRI

Abstract

How to create planetesimals from tiny dust particles in a proto-planetary disk before the dust particles spiral to the central star is one of the most challenging problems in the theory of planetary system formation. In our previous paper Kato et al. (2009), we have shown that a steady angular velocity profile that consists of both super and sub-Keplerian regions is created in the disk through non-uniform excitation of Magneto-Rotational Instability (MRI). Such non-uniform MRI excitation is reasonably expected in a part of disks with relatively low ionization degree. In this paper, we show through three-dimensional resistive MHD simulations with test particles that this radial structure of the angular velocity indeed leads to prevention of spiral-in of dust particles and furthermore to their accumulation at the boundary of super-Keplerian and sub-Keplerian regions. Treating dust particles as test particles, their motions under the influence of the non-uniform MRI through gas drag are simulated. In the most favorable cases (meter-size dust particles in the disk region with a relatively large fraction of MRI-stable region), we found that the dust concentration is peaked around the super/sub-Keplerian flow boundary and the peak dust density is 10,000 times as high as the initial value. The peak density is high enough for the subsequent gravitational instability to set in, suggesting a possible route to planetesimal formation via non-uniformly excited MRI in weakly ionized regions of a disk.

40 pages, 15 figures, accepted for publication in ApJ

References in corpus (7)

• Dust settling in local simulations of turbulent protoplanetary disks
• Dust sedimentation and self-sustained Kelvin-Helmholtz turbulence in protoplanetary disk mid-planes. I. Radially symmetric simulations
• Embryos grown in the dead zone: Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids
• Turbulent Torques on Protoplanets in a Dead Zone
• Turbulent transport and its effect on the dead zone in protoplanetary discs
• Orbital Advection by Interpolation: A Fast and Accurate Numerical Scheme for Super-Fast MHD Flows
• N-Body Simulation of Planetesimal Formation through Gravitational Instability of a Dust Layer in Laminar Gas Disk

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• Planetesimal Formation at the Boundary Between Steady Super/Sub-Keplerian Flow Created by Inhomogeneous Growth of Magnetorotational Instability
• Shear-driven instabilities in Hall-MHD plasmas
• United Theory of Planet Formation (I): Tandem Regime
• Meridional Circulation driven by Planetary Spiral Wakes in Radiative and Magnetized Protoplanetary Discs
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