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

Tsukamoto, Yusuke; Iwasaki, Kazunari; Okuzumi, Satoshi; Machida, Masahiro N.; Inutsuka, Shu‐ichiro

doi:10.1093/mnras/stv1290

Cited by 125 publications

(126 citation statements)

References 47 publications

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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. Its effect depends on the orientation between the rotation axis and the magnetic field (parallel or anti-parallel), which results in a bi-modality in the disk properties (Tsukamoto et al 2015a).…”

Section: Introductionmentioning

confidence: 74%

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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Section: Introductionmentioning

confidence: 74%

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

Dzyurkevich

Commerçon

Lesaffre

et al. 2017

A&A

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“…The studies presented in previous works, such as Li et al (2011), Tomida et al (2015 and Tsukamoto et al (2015b), are complementary to this study. Caution must be used, however, when comparing the studies to one another and to ours since there are differences in initial conditions, physical and numerical processes.…”

Section: Comparison To Other Workmentioning

confidence: 80%

“…They predict their disc will continue to grow, although it is already massive enough to form non-axisymmetric structures and possibly fragment. Tsukamoto et al (2015b) form an r ≈ 1 AU disc just after the formation of the protostellar core in both of their models that include non-ideal MHD terms.…”

Section: Comparison To Other Workmentioning

confidence: 99%

“…Correspondingly, numerical simulations with Ohmic diffusion show only small, AU-scale discs (Dapp & Basu 2010;Machida et al 2011;Tomida et al 2013). Similarly, a number of authors have concluded that ambipolar diffusion alone is unable to sufficiently weaken the magnetic braking to allow large, rotationally supported discs to form under realistic conditions (Duffin & Pudritz 2009;Mellon & Li 2009;Li et al 2011;Dapp et al 2012;Tomida et al 2015;Tsukamoto et al 2015b). …”

Section: Introductionmentioning

confidence: 98%

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Can non-ideal magnetohydrodynamics solve the magnetic braking catastrophe?

Wurster

Price

Bate

2016

Mon. Not. R. Astron. Soc.

149

235

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We investigate whether or not the low ionisation fractions in molecular cloud cores can solve the 'magnetic braking catastrophe', where magnetic fields prevent the formation of circumstellar discs around young stars. We perform three-dimensional smoothed particle non-ideal magnetohydrodynamics (MHD) simulations of the gravitational collapse of one solar mass molecular cloud cores, incorporating the effects of ambipolar diffusion, Ohmic resistivity and the Hall effect alongside a self-consistent calculation of the ionisation chemistry assuming 0.1µm grains. When including only ambipolar diffusion or Ohmic resistivity, discs do not form in the presence of strong magnetic fields, similar to the cases using ideal MHD. With the Hall effect included, disc formation depends on the direction of the magnetic field with respect to the rotation vector of the gas cloud. When the vectors are aligned, strong magnetic braking occurs and no disc is formed. When the vectors are anti-aligned, a disc with radius of 13 AU can form even in strong magnetic when all three non-ideal terms are present, and a disc of 38 AU can form when only the Hall effect is present; in both cases, a counter-rotating envelope forms around the first hydrostatic core. For weaker, anti-aligned fields, the Hall effect produces massive discs comparable to those produced in the absence of magnetic fields, suggesting that planet formation via gravitational instability may depend on the sign of the magnetic field in the precursor molecular cloud core.

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“…Thus, both the angular momentum and the magnetic flux should be removed from the clouds before star formation occurs. In the present-day (or nearby) star formation process, these problems are being investigated using three dimensional nonideal magnetohydrodynamic (MHD) simulations, in which the angular momentum is transferred by magnetic braking and magnetically driven wind, and the magnetic field dissipates or is removed by both Ohmic dissipation and ambipolar diffusion (e.g., Tomisaka 2000; Banerjee & Pudritz 2006;Machida et al 2007;Seifried et al 2011;Tomida et al 2015;Tsukamoto et al 2015;Wurster et al 2016). Thus, the mag-netic field and its dissipation process are considered to be the keys to understanding present-day star formation.…”

Section: Introductionmentioning

confidence: 99%

Evolution of magnetic fields in collapsing star-forming clouds under different environments

Higuchi

Machida

Susa

2018

Monthly Notices of the Royal Astronomical Society

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In nearby star-forming clouds, amplification and dissipation of the magnetic field are known to play crucial roles in the star-formation process. The star-forming environment varies from place to place and era to era in galaxies. In the present study, amplification and dissipation of magnetic fields in star-forming clouds are investigated under different environments using magnetohydrodynamics (MHD) simulations. We consider various star-forming environments in combination with the metallicity and the ionization strength, and prepare prestellar clouds having two different mass-to-flux ratios. We calculate the cloud collapse until protostar formation using ideal and nonideal (inclusion and exclusion of Ohmic dissipation and ambipolar diffusion) MHD calculations to investigate the evolution of the magnetic field. We perform 288 runs in total and show the diversity of the density range within which the magnetic field effectively dissipates, depending on the environment. In addition, the dominant dissipation process (Ohmic dissipation or ambipolar diffusion) is shown to strongly depend on the star-forming environment. Especially, for the primordial case, magnetic field rarely dissipates without ionization source, while it efficiently dissipates when very weak ionization sources exist in the surrounding environment. The results of the present study help to clarify star formation in various environments.

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

Cited by 125 publications

References 47 publications

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

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

Can non-ideal magnetohydrodynamics solve the magnetic braking catastrophe?

Evolution of magnetic fields in collapsing star-forming clouds under different environments

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