PLANETESIMAL FORMATION IN MAGNETOROTATIONALLY DEAD ZONES: CRITICAL DEPENDENCE ON THE NET VERTICAL MAGNETIC FLUX

Journal Article · Sun Jul 01 04:00:00 EDT 2012 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/753/1/L8· OSTI ID:22047718

Okuzumi, Satoshi ^[1]; Hirose, Shigenobu ^[2]

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1. Department of Physics, Nagoya University, Nagoya, Aichi 464-8602 (Japan)
2. Institute for Research on Earth Evolution, JAMSTEC, Yokohama, Kanagawa 236-0001 (Japan)

Turbulence driven by magnetorotational instability (MRI) affects planetesimal formation by inducing diffusion and collisional fragmentation of dust particles. We examine conditions preferred for planetesimal formation in MRI-inactive 'dead zones' using an analytic dead-zone model based on our recent resistive MHD simulations. We argue that successful planetesimal formation requires not only a sufficiently large dead zone (which can be produced by tiny dust grains) but also a sufficiently small net vertical magnetic flux (NVF). Although often ignored, the latter condition is indeed important since the NVF strength determines the saturation level of turbulence in MRI-active layers. We show that direct collisional formation of icy planetesimal across the fragmentation barrier is possible when the NVF strength is lower than 10 mG (for the minimum-mass solar nebula model). Formation of rocky planetesimals via the secular gravitational instability is also possible within a similar range of the NVF strength. Our results indicate that the fate of planet formation largely depends on how the NVF is radially transported in the initial disk formation and subsequent disk accretion processes.

• OSTI ID: 22047718
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 753; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
ASTROPHYSICS
COSMIC DUST
DIFFUSION
FRAGMENTATION
GRAVITATIONAL INSTABILITY
LAYERS
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETOHYDRODYNAMICS
NMR IMAGING
PLANETS
PROTOPLANETS
SOLAR NEBULA
TURBULENCE