Non-Ideal MHD Effects and Magnetic Braking Catastrophe in Protostellar Disk Formation

Li, Zhi-Yun; Krasnopolsky, Ruben; Shang, Hsien

doi:10.1088/0004-637x/738/2/180

Cited by 211 publications

(351 citation statements)

References 69 publications

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“…In previous works which argue that the disc formation is strongly suppressed by the magnetic braking (e.g., Mellon & Li 2008;Li, Krasnopolsky & Shang 2011), the inner boundary was set from the beginning of the simulations. With this treatment, the previous works cannot follow the first core phase properly that should be supported by gas pressure.…”

Section: Summary and Discussionmentioning

confidence: 99%

Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs

Tsukamoto

Iwasaki

Okuzumi

et al. 2015

Mon. Not. R. Astron. Soc.

125

116

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We investigate the formation and evolution of a first core, protostar, and circumstellar disc with a three-dimensional non-ideal (including both Ohmic and ambipolar diffusion) radiation magnetohydrodynamics simulation. We found that the magnetic flux is largely removed by magnetic diffusion in the first core phase and that the plasma β of the centre of the first core becomes large, β > 10 4 . Thus, proper treatment of first core phase is crucial in investigating the formation of protostar and disc. On the other hand, in an ideal simulation, β ∼ 10 at the centre of the first core. The simulations with magnetic diffusion show that the circumstellar disc forms at almost the same time of protostar formation even with a relatively strong initial magnetic field (the value for the initial mass-to-flux ratio of the cloud core relative to the critical value is µ = 4). The disc has a radius of r ∼ 1 AU at the protostar formation epoch. We confirm that the disc is rotationally supported. We also show that the disc is massive (Q ∼ 1) and that gravitational instability may play an important role in the subsequent disc evolution.

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Section: Summary and Discussionmentioning

confidence: 99%

Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs

Tsukamoto

Iwasaki

Okuzumi

et al. 2015

Mon. Not. R. Astron. Soc.

125

116

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“…Krasnopolsky et al 2010;Li et al 2011;Dapp et al 2012). In the context of this work, we would like to point out that Machida et al (2014) find an extremely high resolution (< 1 AU) to be required to form a Keplerian disc.…”

Section: Open Questions and Uncertaintiesmentioning

confidence: 99%

Accretion and magnetic field morphology around Class 0 stage protostellar discs

Seifried

Banerjee

Pudritz

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We analyse simulations of turbulent, magnetised molecular cloud cores focussing on the formation of Class 0 stage protostellar discs and the physical conditions in their surroundings. We show that for a wide range of initial conditions Keplerian discs are formed in the Class 0 stage already. In particular, we show that even subsonic turbulent motions reduce the magnetic braking efficiency sufficiently in order to allow rotationally supported discs to form. We therefore suggest that already during the Class 0 stage the fraction of Keplerian discs is significantly higher than 50%, consistent with recent observational trends but significantly higher than predictions based on simulations with misaligned magnetic fields, demonstrating the importance of turbulent motions for the formation of Keplerian discs. We show that the accretion of mass and angular momentum in the surroundings of protostellar discs occurs in a highly anisotropic manner, by means of a few narrow accretion channels. The magnetic field structure in the vicinity of the discs is highly disordered, revealing field reversals up to distances of 1000 AU. These findings demonstrate that as soon as even mild turbulent motions are included, the classical disc formation scenario of a coherently rotating environment and a well-ordered magnetic field breaks down. Hence, it is highly questionable to assess the magnetic braking efficiency based on non-turbulent collapse simulation. We strongly suggest that, in addition to the global magnetic field properties, the small-scale accretion flow and detailed magnetic field structure have to be considered in order to assess the likelihood of Keplerian discs to be present.

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“…According to Li et al (2011), Hall effect is dynamically significant but not capable of forming the rotationally-supported disk. The results of Tsukamoto et al (2015b) show the contrary, a possibility to form large disks under specific conditions.…”

Section: Introductionmentioning

confidence: 99%

Magnetic diffusivities in 3D radiative chemo-hydrodynamic simulations of protostellar collapse

Dzyurkevich

Commerçon

Lesaffre

et al. 2017

A&A

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Context. Both theory and observations of star-forming clouds require the simulations which combine the co-evolving chemistry, magneto-hydrodynamics and radiative transfer in protostellar collapse simulation. A detailed knowledge of self-consistent chemical evolution for the main charge carriers (both gas species and dust grains) allows to correctly estimate the rate and nature of magnetic dissipation in the collapsing core. Last is of crucial importance for answering the grand question of star and planet formation: the magnitude and spatial distribution of magnetic flux as the initial condition to protoplanetary disk evolution. Aims. We use a chemo-dynamical version of RAMSES, described in a companion publication, to follow the chemo-dynamical evolution of collapsing dense cores with the various dust properties and interpret the occuring differences in the magnetic diffusivity terms. Later are of crucial importance for the circumstellar disk formation. Methods. We perform 3D chemo-dynamical simulations of 1 M⊙ isolated dense core collapse for a range in the dust size assumptions. The number density of dust and it's mean size are affecting the efficiency of charge capturing and the formation of ices. The radiative hydrodynamics and dynamical evolution of chemical abundances are used to reconstruct the magnetic diffusivity terms for clouds with various magnetisation. Results. The simulations are performed for a mean dust size ranging from 0.017µm to 1µm, and we adopt both a fixed dust size and a dust size distribution. The chemical abundances for this range of dust sizes are produced by RAMSES and serve as an input to calculations of Ohmic, ambipolar and Hall diffusivity terms. Ohmic resistivity only play a role at the late stage of the collapse, in the innermost region of the cloud where gas density exceeds few times 10 13 cm −3 . Ambipolar diffusion is a dominant magnetic diffusivity term in cases where mean dust size is a typical ISM value or larger. We demonstrate that the assumption of a fixed 'dominant ion' mass can lead to one order of magnitude mismatch in the ambipolar diffusion magnitude. 'Negative' Hall effect is dominant during the collapse in case of small dust, i.e. for the mean dust size of 0.02 µm and smaller, the effect which we connect to the dominance of negatively charged grains. We find that the Hall effect reverses its sign for mean dust size of 0.1µm and smaller. The phenomenon of the sign reversal is strongly depending on the number of negatively charged dust relative to the ions, and quality of coupling of the last to the magnetic fields. We have adopted different strength of magnetic fields, β = Pgas/Pmag = 2, 5, 25. We observe that the variation on the field strength only shifts the Hall effect reversal along the radius of the collapsing cloud, but do not prevent it. Conclusions. The dust grain mean size appears to be the parameter with the strongest impact on the magnitude of the magnetic diffusivity, dividing the collapsing clouds in Hall-dominated and ambipolar-dominated cloud...

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Non-Ideal MHD Effects and Magnetic Braking Catastrophe in Protostellar Disk Formation

Cited by 211 publications

References 69 publications

Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs

Effects of Ohmic and ambipolar diffusion on formation and evolution of first cores, protostars, and circumstellar discs

Accretion and magnetic field morphology around Class 0 stage protostellar discs

Magnetic diffusivities in 3D radiative chemo-hydrodynamic simulations of protostellar collapse

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