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On the role of magnetic fields in star formation

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posted on 2019-02-01, 10:12 authored by CJ Nixon, JE Pringle
Magnetic fields are observed in star forming regions. However simulations of the late stages of star formation that do not include magnetic fields provide a good fit to the properties of young stars including the initial mass function (IMF) and the multiplicity. We argue here that the simulations that do include magnetic fields are unable to capture the correct physics, in particular the high value of the magnetic Prandtl number, and the low value of the magnetic diffusivity. The artificially high (numerical and uncontrolled) magnetic diffusivity leads to a large magnetic flux pervading the star forming region. We argue further that in reality the dynamics of high magnetic Prandtl number turbulence may lead to local regions of magnetic energy dissipation through reconnection, meaning that the regions of molecular clouds which are forming stars might be essentially free of magnetic fields. Thus the simulations that ignore magnetic fields on the scales on which the properties of stellar masses, stellar multiplicities and planet-forming discs are determined, may be closer to reality than those which include magnetic fields, but can only do so in an unrealistic parameter regime.

Funding

CJN is supported by the Science and Technology Facilities Council (grant number ST/M005917/1).

History

Citation

New Astronomy, 2019, 67, pp. 89-96

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

  • AM (Accepted Manuscript)

Published in

New Astronomy

Publisher

Elsevier

issn

1384-1076

Acceptance date

2018-09-14

Copyright date

2018

Available date

2019-09-20

Publisher version

https://www.sciencedirect.com/science/article/pii/S1384107618302513?via=ihub

Notes

The file associated with this record is under embargo until 12 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.

Language

en

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