Hall effect in protostellar disc formation and evolution

Zhao, Bo; Caselli, P.; Li, Zhi-Yun; Krasnopolsky, Ruben; Shang, Hsien; Lam, Ka Ho

doi:10.1093/mnras/staa041

Cited by 32 publications

(44 citation statements)

References 77 publications

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“…Further work is needed, as for instance the inclusion of the two other resistive effects, the Ohmic diffusion and the Hall effect, which are found to influence disc formation in the low-mass regime (e.g. Tsukamoto et al 2015;Vaytet et al 2018;Marchand et al 2019;Zhao et al 2020).…”

Section: Comparison With Previous Workmentioning

confidence: 99%

Discs and outflows in the early phases of massive star formation: Influence of magnetic fields and ambipolar diffusion

Commerçon

González

Mignon-Risse

et al. 2022

A&A

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Context. Massive star formation remains one of the most challenging problems in astrophysics, as illustrated by the fundamental issues of the radiative pressure barrier and the initial fragmentation. The wide variety of physical processes involved, in particular the protostellar radiative feedback, increase the complexity of massive star formation in comparison with its low-mass counterpart. Aims. We aim to study the details of mass accretion and ejection in the vicinity of massive star forming cores using high-resolution (5 au) three-dimensional numerical simulations. We investigated the mechanisms at the origin of outflows (radiative force versus magnetic acceleration). We characterised the properties of the disc forming around massive protostars depending on the physics included: hydrodynamics, magnetic fields, and ambipolar diffusion. Methods. We used state-of-the-art three-dimensional adaptive-mesh-refinement models of massive dense core collapse, which integrate the equations of (resistive) grey radiation magnetohydrodynamics, and include sink particle evolution. For the first time, we include both protostellar radiative feedback via pre-main-sequence evolutionary tracks and magnetic ambipolar diffusion. To determine the role of magnetic fields and ambipolar diffusion play in the formation of outflows and discs, we studied three different cases: a purely hydrodynamical run, a magnetised simulation under the ideal approximation (perfect coupling), and a calculation with ambipolar diffusion (resistive case). In the most micro-physically complex model (resistive MHD), we also investigated the effect the initial amplitude of both magnetic field and solid body rotation have on the final properties of the massive protostellar system. We used simple criteria to identify the outflow and disc material and follow their evolution as the central star accretes mass up to 20 M⊙ in most of our models. The radiative, magnetic, and hydrodynamical properties of the outflows and discs are quantitatively measured and cross-compared between models. Results. Massive stars form in all our models, together with outflows and discs. The outflow is completely different when magnetic fields are introduced, so magneto-centrifugal processes are the main driver of the outflow up to stellar masses of 20 M⊙. Then, the disc properties heavily depend on the physics included. In particular, the disc formed in the ideal and resistive runs show opposite properties in terms of plasma beta; that is, the ratio of thermal-to-magnetic pressures and of magnetic field topology. While the disc in the ideal case is dominated by the magnetic pressure and the toroidal magnetic fields, the one formed in the resistive runs is dominated by the thermal pressure and essentially has a vertical magnetic field in the inner regions (R < 100−200 au). Conclusions. We find that magnetic processes dominate the early evolution of massive protostellar systems (M⋆ < 20 M⊙) and shapes the accretion and ejection as well as the disc formation. Ambipolar diffusion is mainly at work at disc scales and regulates its properties. We predict magnetic field’s topology within the disc and outflows, as well as disc masses and radii to be compared with observations. Lastly, our finding for the outflow and disc properties are reminiscent of the low-mass star formation framework, suggesting that accretion and ejection in young massive and low-mass protostars are regulated by the same physical processes in the early stages.

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Section: Comparison With Previous Workmentioning

confidence: 99%

Discs and outflows in the early phases of massive star formation: Influence of magnetic fields and ambipolar diffusion

Commerçon

González

Mignon-Risse

et al. 2022

A&A

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“…How much the field strength is decreased compared to ideal MHD will depend on the microphysics of the non-ideal model (e.g. Zhao et al 2020Zhao et al , 2021Wurster et al 2018a;Wurster 2021). Nonetheless, non-ideal MHD prevents the unobserved > 100 kG fields obtained by ideal MHD simulations (e.g.…”

Section: Magnetic Field Strengthmentioning

confidence: 99%

On the origin of magnetic fields in stars – II. The effect of numerical resolution

Wurster

Bate

Price

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Are the kG-strength magnetic fields observed in young stars a fossil field left over from their formation or are they generated by a dynamo? Our previous numerical study concluded that magnetic fields must originate by a dynamo process. Here, we continue that investigation by performing even higher numerical resolution calculations of the gravitational collapse of a 1 M⊙ rotating, magnetised molecular cloud core through the first and second collapse phases until stellar densities are reached. Each model includes Ohmic resistivity, ambipolar diffusion, and the Hall effect. We test six numerical resolutions, using between 105 and 3 × 107 particles to model the cloud. At all but the lowest resolutions, magnetic walls form in the outer parts of the first hydrostatic core, with the maximum magnetic field strength located within the wall rather than at the centre of the core. At high resolution, this magnetic wall is disrupted by the Hall effect, producing a magnetic field with a spiral-shaped distribution of intensity. As the second collapse occurs, this field is dragged inward and grows in strength, with the maximum field strength increasing with resolution. As the second core forms, the maximum field strength exceeds 1 kG in our highest resolution simulations, and the stellar core field strength exceeds this threshold at the highest resolution. Our resolution study suggests that kG-strength magnetic fields may be implanted in low-mass stars during their formation, and may persist over long timescales given that the diffusion timescale for the magnetic field exceeds the age of the Universe.

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“…This behavior is described in Zhao et al (2020a), where the rotation is accelerated in the opposite direction of the Hall drift in response to the distorted magnetic field lines. B z and B r are lost through the same mechanism, either by the magnetic pressure gradient due to accumulated B z or by the magnetic tensor that straightens the field lines bent in r-direction, depending on the relative strength of the two terms at each location (see Appendix B for detailed discussion of the radial transport).…”

Section: The Collapsing Envelopementioning

confidence: 99%

“…This corresponds roughly to a rotating region where the field lines are significantly pinched and B φ has grown to a level such that u H,r becomes important. Zhao et al (2020a) refers to this as the rotationally-supported Hall current sheet (RSHCS).…”

Section: The Collapsing Envelopementioning

confidence: 99%

“…Unlike the diffusion terms, the Hall effect depends on the sign of the dominant charged species, and thus the relative orientation between the rotation and the magnetic field can have an impact on the dynamics. Zhao et al (2020a) further suggested that the ortho-disk is shortlived, and the para-disk has two components: an inner disk and an outer partition that is more extended and flattened, both in close-to-Keplerian rotation. Recent observations also suggest that the class 0/I disks, which are embedded in the collapsing envelope, are likely small and magnetized ( 50 AU Andrews et al 2018;Andrews 2020;Maury et al 2018Maury et al , 2019.…”

Section: Introductionmentioning

confidence: 99%

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Universal protoplanetary disk size under complete non-ideal magnetohydrodynamics: The interplay between ion-neutral friction, Hall effect, and the Ohmic dissipation

Lee,

Marchand,

Liu

et al. 2021

Preprint

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The role of non-ideal magnetohydrodynamics has been proven critical during the formation of the protoplanetary disk, particularly in regulating its size. We provide a simple model to predict the disk size under the interplay among the ambipolar diffusion, the Hall effect, and the Ohmic dissipation. The model predicts a small disk size of around 20 AU, that depends only sub-linearly on disk parameters, for a wide range of initial conditions of sub-Solar mass and moderate magnetization. It is able to explain phenomena manifested in existing numerical simulations, including the bimodal disk behavior under parallel and anti-parallel alignment between the rotation and magnetic field. In the parallel configuration, the disk size decreases and eventually disappears. In the anti-parallel configuration, and the disk has an outer partition (or pseudo-disk) that is flat, shrinking , and short-lived, as well as a inner partition that grows slowly with mass and is long-lived. Even with significant initial magnetization, the vertical field in the disk can only dominate at the early stage when the mass is low, and the toroidal field eventually dominates in all disks.

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Hall effect in protostellar disc formation and evolution

Cited by 32 publications

References 77 publications

Discs and outflows in the early phases of massive star formation: Influence of magnetic fields and ambipolar diffusion

Discs and outflows in the early phases of massive star formation: Influence of magnetic fields and ambipolar diffusion

On the origin of magnetic fields in stars – II. The effect of numerical resolution

Universal protoplanetary disk size under complete non-ideal magnetohydrodynamics: The interplay between ion-neutral friction, Hall effect, and the Ohmic dissipation

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