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Impact of Magnetic Fields on Fragmentation

Published online by Cambridge University Press:  13 May 2016

Alan P. Boss
Alan P. Boss*
Affiliation:
Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road, N. W., Washington, D. C. 20015–1305, U.S.A.

Abstract

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Fragmentation is the leading explanation for the formation of binary and multiple stars. However, nearly all three dimensional calculations of the collapse and fragmentation of dense molecular cloud cores have ignored the effects of magnetic fields, whereas magnetic fields are generally regarded to be a dominant force in molecular clouds. Three dimensional models of the collapse of clouds with frozen-in magnetic fields have shown that such clouds cannot fragment for a range of initial conditions. However, calculations that allow for magnetic field loss by am-bipolar diffusion have shown that fragmentation is possible for initially prolate or oblate, rotating, magnetically-supported cloud cores. The latter calculations rely on approximations that should be verified by more detailed, traditional magnetohydrodynamical codes. The most obvious effect of magnetic fields is to delay the onset of the collapse phase, but once collapse begins in earnest, fragmentation proceeds in much the same manner as in nonmagnetic clouds, with initially prolate clouds tending to form binary protostars, and with initially oblate clouds tending to form multiple protostars.

Type
IX. Theoretical Context - Detailed Calculations
Information
Symposium - International Astronomical Union , Volume 200: The Formation of Binary Stars , 2001 , pp. 371 - 380
Copyright
Copyright © Astronomical Society of the Pacific 2001 

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