2003ApJ...599..351A -
Astrophys. J., 599, 351-362 (2003/December-2)
Collapse of magnetized singular isothermal toroids. I. The nonrotating case.
ALLEN A., SHU F.H. and LI Z.-Y.
Abstract (from CDS):
We study numerically the collapse of nonrotating self-gravitating magnetized singular isothermal toroids characterized by sound speed, a, and level of magnetic to thermal support, H0. In qualitative agreement with treatments by Galli & Shu and other workers, we find that the infalling material is deflected by the field lines toward the equatorial plane, creating a high-density flattened structure, a pseudodisk. The pseudodisk contracts dynamically in the radial direction, dragging the field lines and threading them into a highly pinched configuration that resembles a split monopole. The oppositely directed field lines across the midplane and the large implied stresses may play a role in how magnetic flux is lost in the actual situation in the presence of finite resistivity or ambipolar diffusion. The infall rate into the central regions is given to 5% uncertainty by the formula M{dot}=(1+H0)a3/G, where G is the universal gravitational constant, anticipated by semianalytical studies of the self-similar gravitational collapses of the singular isothermal sphere and isopedically magnetized disks. The introduction of finite initial rotation results in a complex interplay between pseudodisk and true (Keplerian) disk formation that is examined in a companion paper.
Abstract Copyright:
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Journal keyword(s):
Accretion, Accretion Disks - ISM: Clouds - Magnetohydrodynamics: MHD - Stars: Formation
Simbad objects:
2
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