Episodic accretion in magnetically layered protoplanetary discs

By Philip Armitage, M. Livio, J. E. Pringle. 2001

270 citations recorded by the source corpus.

We study protoplanetary disc evolution assuming that angular momentum transport is driven by gravitational instability at large radii, and magnetohydrodynamic (MHD) turbulence in the hot inner regions. At radii of the order of 1 AU such discs develop a magnetically layered structure, with accretion occurring in an ionized surface layer overlying quiescent gas that is too cool to sustain MHD turbulence. We show that layered discs are subject to a limit cycle instability, in which accretion onto the protostar occurs in ∼ 10 4 yr bursts with u M ∼ 10 −5 M⊙yr −1 , separated by quiescent intervals lasting ∼ 10 5 yr where u M ≈ 10 −8 M⊙yr −1 . Such bursts could lead to repeated episodes of strong mass outflow in Young Stellar Objects. The transition to this episodic mode of accretion occurs at an early epoch (t ≪ 1 Myr), and the model therefore predicts that many young pre-main-sequence stars should have low rates of accretion through the inner disc. At ages of a few Myr, the discs are up to an order of magnitude more massive than the minimum mass solar nebula, with most of the mass locked up in the quiescent layer of the disc at r ∼ 1 AU. The predicted rate of low mass planetary migration is reduced at the outer edge of the layered disc, which could lead to an enhanced probability of giant planet formation at radii of 1 – 3 AU.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/edbd23ff744ac4b35913a1a184250834647da132

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Citations in the corpus

Dead Zone Accretion Flows in Protostellar Disks (2008, background): “The further buildup of material could lead to selfgravitational instability and an episode of rapid accretion on the star (Gammie 1996; Armitage et al. 2001) similar to those associated with intervals of strong mass outflow from young stellar objects (Reipurth 1989).”
Gravitational Instabilities in Circumstellar Disks (2016, background): “Indeed there is no guarantee that a disk will typically be in steady-state with Ṁ(r) = const (Armitage et al. 2001; Martin & Lubow 2011).”
The importance of experiments: Constraints on chondrule formation models (2010, background): “Examples of nebular lightning models include those of Gibbard et al. (1997) and Pilipp et al. (1998), which rely on separation of charge across the scale height of the nebula, and that of Desch and Cuzzi (2000), which relies on separation of charge by turbulent eddies.”
Pseudo-viscous modelling of self-gravitating discs and the formation of low mass ratio binaries (2009, background): “We denote regions of parameter space for which this is the case by the ??? in Figures 1-6 and note that in practice this will cause time-dependent behaviour, as envisaged by Gammie 1999, Armitage et al 2001.”
The ionization fraction in α models of protoplanetary discs (2001, unknown): “Armitage et al. (2001) have considered a disc embedded in a collapsing envelope, so that mass is continuously added to the disc at a rate larger than the accretion through the disc itself.”
NONSTEADY ACCRETION IN PROTOSTARS (2008, methodology): “The feature of mass accumulation at low external α followed by a change to a high inner viscosity is similar to thermal instability models (and also Armitage et al. 2001).”
THE BURST MODE OF ACCRETION AND DISK FRAGMENTATION IN THE EARLY EMBEDDED STAGES OF STAR FORMATION (2010, background): “Bell & Lin 1994; Armitage et al. 2001; Lodato & Clarke 2004; Vorobyov & Basu 2005, 2006; Pfalzner et al. 2008; Zhu et al. 2009, 2010; Forgan & Rice 2010; Bate 2010).”
CHALLENGES IN FORMING PLANETS BY GRAVITATIONAL INSTABILITY: DISK IRRADIATION AND CLUMP MIGRATION, ACCRETION, AND TIDAL DESTRUCTION (2011, background): “…produced by GI-induced fragmentation (Boley et al. 2010) or the episodic nature of the GI accretion (Boley & Durisen 2008) can serve as a mechanism to transport mass to AU scales (compared with the steady accretion by GI as suggested by Armitage et al. 2001 and Zhu et al. 2009) to trigger the MRI.”
Planet formation bursts at the borders of the dead zone in 2D numerical simulations of circumstellar disks (2009, background): “However, the accumulation of matter cannot proceed indefinitely since, as matter piles up, the conditions for gravitational instability would eventually be met (Armitage et al. 2001).”
RESOLVING THE LUMINOSITY PROBLEM IN LOW-MASS STAR FORMATION (2011, background): “…in the outer disk triggers rapid accretion into the inner disk; the subsequent heating of the inner disk by this accretion activates magnetorotational instabilities (MRI) that then drive material onto the protostar in short accretion bursts (Armitage et al. 2001; Zhu et al. 2009a, 2009b, 2010).”
VARIABLE PROTOSTELLAR ACCRETION WITH EPISODIC BURSTS (2015, background): “A combination of the magneto-rotational and thermal instabilities in the inner several AU and gravitational instability further out in the disk (or layered accretion) was shown to produce accretion bursts typical for FU-Orionis-type eruptions (Armitage et al. 2001; Zhu et al. 2009).”
Accretion onto Pre-Main-Sequence Stars (2016, background): “However, the GI might produce sufficient heating in the inner disk that the MRI could be thermally activated, potentially leading to outbursts (Armitage et al. 2001, Zhu et al. 2009b; see also Section 4.2).”