Friday, November 4, 2011

1111.0694 (A. Lazarian)

Fast Reconnection and Reconnection Diffusion: Implications for Star Formation    [PDF]

A. Lazarian
Fast reconnection of magnetic field in turbulent fluids allows magnetic fields change their topology and connections. As a result the traditional concept of magnetic field being frozen into plasma is no more applicable. Plasma which is at one instance can be associated with a given magnetic field lines at the next instant is distributed along a different set of magnetic field lines. This diffusion is enabled by reconnection and therefore is termed "reconnection diffusion". The astrophysical implications of this concept include many astrophysical phenomena, e.g. heat transfer in plasmas, advection of metals in plasmas etc. However, the most dramatic implications of the concept are related to star formation process. The reason for that is that the existing theory of star formation was developed assuming that the decoupling of mass and magnetic field is due to neutrals drifting in respect to magnetic field with entrained ions, i.e. through the process of ambipolar diffusion. This implies that if the ionization of media gets low, the coupling of mass and magnetic field gets better. This is not true in the presence of reconnection diffusion. As a result, the magnetic mediated star formation proceeds very differently. The new picture of star formation can explain existing puzzles that face the traditional theory which appeals to the ambipolar diffusion process. I also would like to stress that the process of reconnection diffusion is very different from a process of accumulation of matter along magnetic field lines that the pandits of numerical star formation frequently appeal to. I discuss how the application of the new concept changes our understanding of star formation and its numerical modeling.
View original: http://arxiv.org/abs/1111.0694

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