Reconnection Diffusion: Fast Removal of Magnetic Field during Star Formation
University of Wisconsin-Madison, Madison, USA
|Recent years have been marked by a notable change in the star formation paradigm. Instead of quasi-static molecular clouds slowly evolving under the influence of gravity and ambipolar diffusion a new picture with more action and dynamics emerged. Within new understanding of interstellar processes, the molecular clouds are associated with turbulent density fluctuations and the structure of the interstellar medium evolves fast on the sound crossing times. I appeal to the advances in understanding of magnetic reconnection in turbulent medium and demonstrate that fast reconnection can cause of the efficient magnetic field diffusion that does not depend on the degree of media ionization. I shall show that a process that I term "reconnection diffusion" can be responsible for efficient removing magnetic flux during star formation. For the giant molecular clouds (GMCs) and for many cloud cores the resulting rates of magnetic field removal dominate the ambipolar diffusion rates in partially ionized gas. I shall show that numerical simulations validate the concept of "reconnection diffusion" and that this process can successfully explain the existing observational data on magnetic field -- density correlations in diffuse media, removal of magnetic fields from clouds and accretion disks on the time scale less than the ambiploar diffusion as well as the recent results on the magnetization of cores and envelops. I shall discuss the implications of the reconnection diffusion process for the theory of star formation.