Magnetorotational instability and dynamo action in gravito-turbulent astrophysical discs

Riols, A.; Latter, Henrik N.

doi:10.1093/mnras/stx2455

Cited by 30 publications

(56 citation statements)

References 72 publications

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“…Our unit of time is Ω −1 = 1, our unit of length is H = 1, while the surface density is fixed equal to Σ = 1.88. For details of how we calculate the 3D self-gravitating potential see Riols et al (2017) and Riols & Latter (2018a). The method was tested on the computations of 1D stratified disc equilibria, as well as their linear stability, to ensure that the implementation is correct (see appendices in Riols et al (2017)).…”

Section: Methodsmentioning

confidence: 99%

“…In this paper we focus on the case τc = 20 Ω −1 . The reader may refer to Riols et al (2017) and Riols & Latter (2018a) (Section 3.1) to obtain a detailed analysis of related simulations and more information about the turbulent properties. For τc = 20 Ω −1 , the turbulence is supersonic, highly compressible and characterized by large-scale spiral density waves, particularly strong in this cooling time regime.…”

Section: Hydrodynamical Gravitoturbulencementioning

confidence: 99%

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Dust dynamics and vertical settling in gravitoturbulent protoplanetary discs

Riols

Roux

Latter

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Gravitational instability (GI) controls the dynamics of young massive protoplanetary discs. Apart from facilitating gas accretion on to the central protostar, it must also impact on the process of planet formation: directly through fragmentation, and indirectly through the turbulent concentration of small solids. To understand the latter process, it is essential to determine the dust dynamics in such a turbulent flow. For that purpose, we conduct a series of 3D shearing box simulations of coupled gas and dust, including the gas's self-gravity and scanning a range of Stokes numbers, from 10 −3 to ∼ 0.2. First, we show that the vertical settling of dust in the midplane is significantly impeded by gravitoturbulence, with the dust scale-height roughly 0.6 times the gas scale height for centimetre grains. This is a result of the strong vertical diffusion issuing from (a) small-scale inertial-wave turbulence feeding off the GI spiral waves and (b) the larger-scale vertical circulations that naturally accompany the spirals. Second, we show that at R = 50 AU concentration events involving sub-metre particles and yielding order 1 dust to gas ratios are rare and last for less than an orbit. Moreover, dust concentration is less efficient in 3D than in 2D simulations. We conclude that GI is not especially prone to the turbulent accumulation of dust grains. Finally, the large dust scale-height measured in simulations could be, in the future, compared with that of edge-on discs seen by ALMA, thus aiding detection and characterisation of GI in real systems.

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Section: Methodsmentioning

confidence: 99%

Section: Hydrodynamical Gravitoturbulencementioning

confidence: 99%

Dust dynamics and vertical settling in gravitoturbulent protoplanetary discs

Riols

Roux

Latter

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…In the lower panels, the higher resolution stratified shearing box (3M elements) captures even finer structures. disks, especially the strong dynamo action reported by Riols & Latter (2018). This spiral wave dynamo is vigorous even with large magnetic resistivity and may be responsible for the primordial magnetic field amplification in galaxy formation (Rieder & Teyssier 2016, a field where adaptive resolution (either with Lagrangian or AMR-type codes) is essentially required.…”

Section: Computational Cost and Possible Applicationsmentioning

confidence: 99%

Local Simulations of MRI turbulence with Meshless Methods

Deng¹,

Mayer²,

Latter

et al. 2019

ApJS

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The magneto-rotational instability (MRI) is one of the most important processes in sufficiently ionized astrophysical disks. Grid-based simulations, especially those using the local shearing box approximation, provide a powerful tool to study the nonlinear turbulence the MRI produces. On the other hand, meshless methods have been widely used in cosmology, galactic dynamics, and planet formation, but have not been fully deployed on the MRI problem. We present local unstratified and vertically stratified MRI simulations with two meshless MHD schemes: a recent implementation of SPH MHD (Price 2012), and a MFM MHD scheme with constrained gradient divergence cleaning, as implemented in the GIZMO code (Hopkins 2017). Concerning variants of the SPH hydro force formulation, we consider both the "vanilla" SPH and the PSPH variant included in GIZMO. We find, as expected, that the numerical noise inherent in these schemes affects turbulence significantly. Also a high-order kernel, free of the pairing instability, is necessary. Both schemes adequately simulate MRI turbulence in unstratified shearing boxes with net vertical flux. The turbulence, however, dies out in zero-net-flux unstratified boxes, probably due to excessive numerical dissipation. In zero-netflux vertically stratified simulations, MFM can reproduce the MRI dynamo and its characteristic butterfly diagram for several tens of orbits before ultimately decaying. In contrast, extremely strong toroidal fields, as opposed to sustained turbulence, develop in equivalent simulations using SPH MHD. The latter unphysical state is likely caused by a combination of excessive artificial viscosity, numerical resistivity, and the relatively large residual errors in the divergence of the magnetic field.

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“…For a more quantitative estimate of the effect of box cooling we also calculated the wind cooling time (cf. Equation 17) and found this to be τw ∼ 112 Ω −1 (time-averaged between orbit 125 and orbit 195) compared to the value of τw ∼ 150 Ω −1 measured in the box-cooled simulation MRI-S1 of Riols & Latter (2018).…”

Section: A3 Time Evolution Of Averaged Quantitiesmentioning

confidence: 78%

“…The integrated flux of total energy across the vertical boundaries (normalized by the volume-averaged thermal energy density) can be used to estimate the rate at which energy is lost through the vertical boundaries, the inverse of which is known as the wind cooling time τw (see Riols & Latter 2018), and this is defined by…”

Section: Energeticsmentioning

confidence: 99%

Magnetohydrodynamic convection in accretion discs

Held,

Latter

2021

Preprint

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Convection has been discussed in the field of accretion discs for several decades, both as a means of angular momentum transport and also because of its role in controlling discs' vertical structure via heat transport. If the gas is sufficiently ionized and threaded by a weak magnetic field, convection might interact in non-trivial ways with the magnetorotational instability (MRI). Recently, vertically stratified local simulations of the MRI have reported considerable variation in the angular momentum transport, as measured by the stress to thermal pressure ratio α, when convection is thought to be present. Although MRI turbulence can act as a heat source for convection, it is not clear how the instabilities will interact dynamically. Here we aim to investigate the interplay between the two instabilities in controlled numerical experiments, and thus isolate the generic features of their interaction. We perform vertically stratified, 3D MHD shearing box simulations with a perfect gas equation of state with the conservative, finite-volume code PLUTO. We find two characteristic outcomes of the interaction between the two instabilities: straight MRI and MRI/convective cycles, with the latter exhibiting alternating phases of convection-dominated flow (during which the turbulent transport is weak) and MRI-dominated flow. During the latter phase we find that α is enhanced by nearly an order of magnitude, reaching peak values of ∼ 0.08. In addition, we find that convection in the non-linear phase takes the form of large-scale and oscillatory convective cells. Convection can also help the MRI persist to lower Rm than it would otherwise do. Finally we discuss how our results help interpret simulations of Dwarf Novae.

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Magnetorotational instability and dynamo action in gravito-turbulent astrophysical discs

Cited by 30 publications

References 72 publications

Dust dynamics and vertical settling in gravitoturbulent protoplanetary discs

Dust dynamics and vertical settling in gravitoturbulent protoplanetary discs

Local Simulations of MRI turbulence with Meshless Methods

Magnetohydrodynamic convection in accretion discs

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