The angular momentum problem and magnetic braking during star formation: Exact solutions for an aligned and a perpendicular rotator

Mouschovias, Telemachos Ch.; Paleologou, E. V.

doi:10.1007/bf00896865

Cited by 29 publications

(13 citation statements)

References 18 publications

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“…The decrease and oscillation (i.e. clockwise and anti-clockwise rotation) of the angular velocity has been clearly presented in the analytic models of Mouschovias & Paleologou (1979) and Mouschovias & Paleologou (1980). We demonstrated the counter-rotating disk in the model with µ 0 = 0.5 in Paper I (see figure 3c in that paper).…”

Section: Cloud Evolution For a Hundred Years After Protostar Formationsupporting

confidence: 52%

Different modes of star formation – II. Gas accretion phase of initially subcritical star-forming clouds

Machida

Basu

2020

Monthly Notices of the Royal Astronomical Society

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The accretion phase of star formation is investigated in magnetically-dominated clouds that have an initial subcritical mass-to-flux ratio. We employ nonideal magnetohydrodynamic simulations that include ambipolar diffusion and ohmic dissipation. During the early prestellar phase the mass-to-flux ratio rises toward the critical value for collapse, and during this time the angular momentum of the cloud core is reduced significantly by magnetic braking.Once a protostar is formed in the core, the accretion phase is characterized by the presence of a small amount of angular momentum but a large amount of magnetic flux in the near-protostellar environment. The low angular momentum leads to a very small (or even nonexistent) disk and weak outflow, while the large magnetic flux can lead to an interchange instability that rapidly removes flux from the central region. The effective magnetic braking in the early collapse phase can even lead to a counter-rotating disk and outflow, in which the rotation direction of the disk and outflow is opposite to that of the infalling envelope. The solutions with a counter-rotating disk, tiny disk, or nonexistent disk (direct collapse) are unique outcomes that are realized in collapse from magnetically-dominated clouds with an initial subcritical mass-to-flux ratio.

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Section: Cloud Evolution For a Hundred Years After Protostar Formationsupporting

confidence: 52%

Different modes of star formation – II. Gas accretion phase of initially subcritical star-forming clouds

Machida

Basu

2020

Monthly Notices of the Royal Astronomical Society

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“…In this study, we adopted a strong magnetic field, as described in §2. Thus, the angular momentum perpendicular to the magnetic field should be preferentially transferred (Mouschovias & Paleologou 1979, 1980a. Interestingly however, the initial rotation axis seems to be roughly preserved (Fig.…”

Section: Disc Directionmentioning

confidence: 95%

Misalignment of Magnetic Fields, Outflows and Discs in Star-forming Clouds

Machida

Hirano

Kitta

2019

Monthly Notices of the Royal Astronomical Society

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Using resistive magnetohydrodynamics simulations, the propagation of protostellar jets, the formation of circumstellar discs and the configuration of magnetic fields are investigated from the prestellar cloud phase until ∼500 yr after protostar formation. As the initial state, we prepare magnetized rotating clouds, in which the rotation axis is misaligned with the global magnetic field by an angle θ 0 . We calculate the cloud evolution for nine models with different θ 0 (= 0, 5, 10, 30, 45, 60, 80, 85, 90 • ). Our simulations show that there is no significant difference in the physical quantities of the protostellar jet, such as the mass and momentum, among the models except for the model with θ 0 = 90 • . On the other hand, the directions of the jet, disc normal and magnetic field are never aligned with each other during the early phase of star formation except for the model with θ 0 = 0 • . Even when the rotation axis of the prestellar cloud is slightly inclined to the global magnetic field, the directions of the jet, disc normal and local magnetic field differ considerably, and they randomly change over time. Our results indicate that it is very difficult to extract any information from the observations of the directions of the outflow, disc and magnetic field at the scale of ∼ < 1000 au. Thus, we cannot use such observations to derive any restrictions on the star formation process.

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“…The outer layers of the dense cylinder has lost part of its initial angular momentum in form of Alvén waves radiating away. This braking of the magnetic rotor is a possible model for the angular momentum loss of collapsing gas clouds in star formation [45,46].…”

Section: The Rotor Problemmentioning

confidence: 99%

Fish: A Three-Dimensional Parallel Magnetohydrodynamics Code for Astrophysical Applications

Käppeli¹,

Whitehouse²,

Scheidegger³

et al. 2011

ApJS

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fish is a fast and simple ideal magneto-hydrodynamics code that scales to ∼ 10 000 processes for a Cartesian computational domain of ∼ 1000 3 cells. The simplicity offish has been achieved by the rigorous application of the operator splitting technique, while second order accuracy is maintained by the symmetric ordering of the operators. Between directional sweeps, the three-dimensional data is rotated in memory so that the sweep is always performed in a cache-efficient way along the direction of contiguous memory. Hence, the code only requires a one-dimensional description of the conservation equations to be solved. This approach also enable an elegant novel parallelisation of the code that is based on persistent communications with MPI for cubic domain decomposition on machines with distributed memory. This scheme is then combined with an additional OpenMP parallelisation of different sweeps that can take advantage of clusters of shared memory. We document the detailed implementation of a second order TVD advection scheme based on flux reconstruction. The magnetic fields are evolved by a constrained transport scheme. We show that the subtraction of a simple estimate of the hydrostatic gradient from the total gradients can significantly reduce the dissipation of the advection scheme in simulations of gravitationally bound hydrostatic objects. Through its simplicity and efficiency, fish is as well-suited for hydrodynamics classes as for large-scale astrophysical simulations on high-performance computer clusters. In preparation for the release of a public version, we demonstrate the performance of fish in a suite of astrophysically orientated test cases.

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The angular momentum problem and magnetic braking during star formation: Exact solutions for an aligned and a perpendicular rotator

Cited by 29 publications

References 18 publications

Different modes of star formation – II. Gas accretion phase of initially subcritical star-forming clouds

Different modes of star formation – II. Gas accretion phase of initially subcritical star-forming clouds

Misalignment of Magnetic Fields, Outflows and Discs in Star-forming Clouds

Fish: A Three-Dimensional Parallel Magnetohydrodynamics Code for Astrophysical Applications

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