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    National Tsing Hua University Institutional Repository > 歷任校長 > 徐遐生 (2002-2006) > 期刊論文 >  Ambipolar diffusion in molecular cloud cores and the gravomagneto catastrophe


    Please use this identifier to cite or link to this item: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/80918


    Title: Ambipolar diffusion in molecular cloud cores and the gravomagneto catastrophe
    Authors: Adams, FC;Shu, FH
    教師: 徐遐生
    Date: 2007
    Publisher: American Astronomical Society
    Relation: ASTROPHYSICAL JOURNAL, American Astronomical Society, Volume 671, Issue 1, DEC 10 2007, Pages 497-517
    Keywords: methods: analytical
    MHD
    stars: formation
    Abstract: This paper reexamines the problem of ambipolar diffusion as a mechanism for the production and runaway evolution of centrally condensed molecular cloud cores, a process that has been termed the gravomagneto catastrophe. Our calculation applies in the geometric limit of a highly flattened core and allows for a semianalytic treatment of the full problem, although physical fixes are required to resolve a poor representation of the central region. A noteworthy feature of the overall formulation is that the solutions for the ambipolar diffusion portion of the evolution for negative times (t < 0) match smoothly onto the collapse solutions for positive times (t > 0). The treatment shows that the resulting cores display nonzero, but submagnetosonic, inward velocities at the end of the diffusion epoch, in agreement with current observations. Another important result is the derivation of an analytic relationship between the dimensionless mass-to-flux ratio lambda(0) equivalent to f(0)(-1) of the central regions produced by runaway core condensation and the dimensionless measure of the rate of ambipolar diffusion is an element of. In conjunction with previous work showing that ambipolar diffusion takes place more quickly in the presence of turbulent fluctuations, i.e., that the effective value of is an element of can be enhanced by turbulence, the resultant theory provides a viable working hypothesis for the formation of isolated molecular cloud cores and their subsequent collapse to form stars and planetary systems.
    Relation Link: http://aas.org/
    URI: http://nthur.lib.nthu.edu.tw/dspace/handle/987654321/80918
    Appears in Collections:[ 徐遐生 (2002-2006)] 期刊論文
    [物理系] 期刊論文

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