Please use this identifier to cite or link to this item: http://hdl.handle.net/10995/111505
Title: Accretion Bursts in Magnetized Gas-Dust Protoplanetary Disks
Authors: Vorobyov, E. I.
Khaibrakhmanov, S.
Basu, S.
Audard, M.
Issue Date: 2020
Publisher: EDP Sciences
EDP Sciences
Citation: Accretion Bursts in Magnetized Gas-Dust Protoplanetary Disks / E. I. Vorobyov, S. Khaibrakhmanov, S. Basu et al. — DOI 10.1103/PhysRevB.75.165115 // Astronomy and Astrophysics. — 2020. — Vol. 644. — A74.
Abstract: Aims. Accretion bursts triggered by the magnetorotational instability (MRI) in the innermost disk regions were studied for protoplanetary gas-dust disks that formed from prestellar cores of a various mass Mcore and mass-to-magnetic flux ratio λ. Methods. Numerical magnetohydrodynamics simulations in the thin-disk limit were employed to study the long-term (∼1.0 Myr) evolution of protoplanetary disks with an adaptive turbulent α-parameter, which explicitly depends on the strength of the magnetic field and ionization fraction in the disk. The numerical models also feature the co-evolution of gas and dust, including the back-reaction of dust on gas and dust growth. Results. A dead zone with a low ionization fraction of x ≲ 10-13 and temperature on the order of several hundred Kelvin forms in the inner disk soon after its formation, extending from several to several tens of astronomical units depending on the model. The dead zone features pronounced dust rings that are formed due to the concentration of grown dust particles in the local pressure maxima. Thermal ionization of alkaline metals in the dead zone trigger the MRI and associated accretion burst, which is characterized by a sharp rise, small-scale variability in the active phase, and fast decline once the inner MRI-active region is depleted of matter. The burst occurrence frequency is highest in the initial stages of disk formation and is driven by gravitational instability (GI), but it declines with diminishing disk mass-loading from the infalling envelope. There is a causal link between the initial burst activity and the strength of GI in the disk fueled by mass infall from the envelope. We find that the MRI-driven burst phenomenon occurs for λ = 2-10, but diminishes in models with Mcore ≲ M⊙, suggesting a lower limit on the stellar mass for which the MRI-triggered burst can occur. Conclusions. The MRI-triggered bursts occur for a wide range of mass-to-magnetic flux ratios and initial cloud core masses. The burst occurrence frequency is highest in the initial disk formation stage and reduces as the disk evolves from a gravitationally unstable to a viscous-dominated state. The MRI-triggered bursts are intrinsically connected with the dust rings in the inner disk regions, and both can be a manifestation of the same phenomenon, that is to say the formation of a dead zone. © 2020 ESO.
Keywords: ACCRETION
ACCRETION DISKS
INSTABILITIES
PROTOPLANETARY DISKS
STARS: PROTOSTARS
DUST
IONIZATION OF GASES
MAGNETIC FLUX
MAGNETOHYDRODYNAMICS
ASTRONOMICAL UNITS
GRAVITATIONAL INSTABILITY
IONIZATION FRACTIONS
MAGNETO-HYDRODYNAMICS SIMULATIONS
MAGNETOROTATIONAL INSTABILITY
PROTOPLANETARY DISKS
SMALL SCALE VARIABILITY
THERMAL IONIZATION
GRAVITATION
URI: http://hdl.handle.net/10995/111505
Access: info:eu-repo/semantics/openAccess
SCOPUS ID: 85097340850
PURE ID: 20220505
ISSN: 0004-6361
DOI: 10.1103/PhysRevB.75.165115
metadata.dc.description.sponsorship: Acknowledgements. We thank the anonymous referee for useful comments that helped to improve the manuscript. This paper is supported by the Austrian Science Fund (FWF) under research grant I2549-N27 and Swiss National Science Foundation (SNSF) (project number 200021L_163172). The work of Sergey Khaibrakhmanov in Sects. 2.3 and 2.4 is supported by the Large Scientific Project of the Russian Ministry of Science and Higher Education “Theoretical and experimental studies of the formation and evolution of extrasolar planetary systems and characteristics of exoplanets” (project No. 075-15-2020-780, contract 780-10). SB was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada. The simulations were performed on the Vienna Scientific Cluster (VSC-3 and VSC-4) and on the Shared Hierarchical Academic Research Computing Network (SHARCNET).
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