Dependence of the Saturation Level of Magnetorotational Instability on Gas Pressure and Magnetic Prandtl Number

Minoshima, Takashi; Hirose, Shigenobu; Sano, Takayoshi

doi:10.1088/0004-637x/808/1/54

Cited by 21 publications

(25 citation statements)

References 50 publications

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“…The total magnetic energy is about twice more in run Up compared to run Down, scaling as the ratio of stresses in accordance with previous studies of MRI-induced turbulence in local ideal MHD simulations (see e.g. Minoshima et al 2015 We do observe the formation of structures such as gaps close to the inner and outer boundaries, but we attribute them to the damping buffer zones for the density accumulates precisely at the edge between the the inner buffer and the active domain. This is the kind of density structures we want to avoid when implementing our own buffers, as described in Sect.…”

Section: Comparison With Previous Worksupporting

confidence: 90%

Self-organisation in protoplanetary discs

Béthune

Lesur

Ferreira

2016

A&A

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Context. Recent observations have revealed organised structures in protoplanetary discs, such as axisymmetric rings or horseshoe concentrations, evocative of large-scale vortices. These structures are often interpreted as the result of planet-disc interactions. However, these discs are also known to be unstable to the magneto-rotational instability (MRI) which is believed to be one of the dominant angular momentum transport mechanism in these objects. It is therefore natural to ask whether the MRI itself could produce these structures without invoking planets. Aims. The nonlinear evolution of the MRI is strongly affected by the low ionisation fraction in protoplanetary discs. The Hall effect in particular, which is dominant in dense and weakly ionised parts of these objects, has been shown to spontaneously drive self-organising flows in local, shearing box simulations. Here, we investigate the behaviour of global MRI-unstable disc models dominated by the Hall effect and characterise their dynamics. Methods. We validated our implementation of the Hall effect into the PLUTO code with predictions from a spectral method in cylindrical geometry. We then performed 3D unstratified Hall-MHD simulations of Keplerian discs for a broad range of Hall, Ohmic, and ambipolar Elsasser numbers. Results. We confirm the transition from a turbulent to an organised state as the intensity of the Hall effect is increased. We observe the formation of zonal flows, their number depending on the available magnetic flux and on the intensity of the Hall effect. For intermediate Hall intensity, the flow self-organises into long-lived magnetised vortices. Neither the addition of a toroidal field nor Ohmic or ambipolar diffusion change this picture drastically in the range of parameters we have explored. Conclusions. Self-organisation by the Hall effect is a robust phenomenon in global non-stratified simulations. It is able to quench turbulent transport and spontaneously produce axisymmetric rings or sustained vortices. The ability of these structures to trap dust particles in this configuration is demonstrated. We conclude that Hall-MRI driven organisation is a plausible scenario that could explain some of the structures found in recent observations.

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Section: Comparison With Previous Worksupporting

confidence: 90%

Self-organisation in protoplanetary discs

Béthune

Lesur

Ferreira

2016

A&A

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“…The stress tensor can be assumed to be dominated by Maxwell stresses (e.g., Hawley et al 1995;Sano et al 2004;Minoshima et al 2015), from which we can write τ rφ = k 0 P mag , with k 0 being a constant of order unity (Hawley et al 1995). To build a self-consistent solution to the accretion problem, we need to relate the stress tensor (via the magnetic pressure) with local quantities that standard analytic models are familiar with.…”

Section: The Disk-corona Modelmentioning

confidence: 99%

Testing the disk-corona interplay in radiatively-efficient broad-line AGN

Arcodia

Merloni

Nandra

et al. 2019

A&A

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The correlation observed between monochromatic X-ray and UV luminosities in radiatively-efficient active galactic nuclei (AGN) lacks a clear theoretical explanation despite being used for many applications. Such a correlation, with its small intrinsic scatter and its slope that is smaller than unity in log space, represents the compelling evidence that a mechanism regulating the energetic interaction between the accretion disk and the X-ray corona must be in place. This ensures that going from fainter to brighter sources the coronal emission increases less than the disk emission. We discuss here a self-consistently coupled disk-corona model that can identify this regulating mechanism in terms of modified viscosity prescriptions in the accretion disk. The model predicts a lower fraction of accretion power dissipated in the corona for higher accretion states. We then present a quantitative observational test of the model using a reference sample of broad-line AGN and modeling the disk-corona emission for each source in the L X − L UV plane. We used the slope, normalization, and scatter of the observed relation to constrain the parameters of the theoretical model. For non-spinning black holes and static coronae, we find that the accretion prescriptions that match the observed slope of the L X − L UV relation produce X-rays that are too weak with respect to the normalization of the observed relation. Instead, considering moderatelyoutflowing Comptonizing coronae and/or a more realistic high-spinning black hole population significantly relax the tension between the strength of the observed and modeled X-ray emission, while also predicting very low intrinsic scatter in the L X − L UV relation. In particular, this latter scenario traces a known selection effect of flux-limited samples that preferentially select high-spinning, hence brighter, sources.

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“…The loop structure is seriously distorted in the HLLD-GLM and the HLL-CUCT schemes owing to the overestimation of the amount of numerical diffusion. The time scale of the numerical diffusion is proportional to the transit time of the fast mode wave in the HLL-CUCT scheme (Minoshima et al 2015). Therefore, the magnetic loop quickly diffuses outward and inward in the course of the flow, and the inward diffusion leads to the cancellation of the anti-parallel field at the center of the loop.…”

Section: Field Loop Advectionmentioning

confidence: 99%

A High-order Weighted Finite Difference Scheme with a Multistate Approximate Riemann Solver for Divergence-free Magnetohydrodynamic Simulations

Minoshima

Miyoshi

Matsumoto

2019

ApJS

Self Cite

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We design a conservative finite difference scheme for ideal magnetohydrodynamic simulations that attains high-order accuracy, shock-capturing, and divergence-free condition of the magnetic field. The scheme interpolates pointwise physical variables from computational nodes to midpoints through a high-order nonlinear weighted average. The numerical flux is evaluated at the midpoint by a multi-state approximate Riemann solver for correct upwinding, and its spatial derivative is approximated by a high-order linear central difference to update the variables with designed order of accuracy and conservation. The magnetic and electric fields are defined at staggered grid points employed in the Constrained Transport (CT) method by Evans & Hawley (1988). We propose a new CT variant, in which the staggered electric field is evaluated so as to be consistent with the base one-dimensional Riemann solver and the staggered magnetic field is updated to be divergence-free as designed high-order finite difference representation. We demonstrate various benchmark tests to measure the performance of the present scheme. We discuss the effect of the choice of interpolation methods, Riemann solvers, and the treatment for the divergence-free condition on the quality of numerical solutions in detail.

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Dependence of the Saturation Level of Magnetorotational Instability on Gas Pressure and Magnetic Prandtl Number

Cited by 21 publications

References 50 publications

Self-organisation in protoplanetary discs

Self-organisation in protoplanetary discs

Testing the disk-corona interplay in radiatively-efficient broad-line AGN

A High-order Weighted Finite Difference Scheme with a Multistate Approximate Riemann Solver for Divergence-free Magnetohydrodynamic Simulations

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