Collapse of weakly ionized rotating turbulent Cloud Cores

In view of the Turbulent Cooling Flows scenario we carry out several 3D axi symmetric calculations to follow the evolution of magnetically subcritical weakly ionized and rotating turbulent cloud cores. Turbulent Cooling Flows appear to pronounce the effects of ambipolar diffusion considerably, induci ng thereby a runaway collapse of the core already on a diluted free-fall ti me scale. Ambipolar diffusion significantly weakens the efficiency of magne tic braking. This implies that most of the rotational energy is trapped int o the dynamically collapsing core and that initiation of outflows is preven ted at least in the early isothermal phases. The trapped rotational energy is found to enhance the formation of rings that may afterwards fragment. It is shown that the central region of a strongly ionized magnetically subcri tical core is principally overdense, with central density up to one order o f magnitude larger than the surroundings. These results confirm that large scale magnetic fields threading a cloud core relax the supersonic random mo tions on an Alfven wave crossing time. Moreover, ambipolar diffusion enhanc es dissipation of supersonic turbulence even more. (C) 2000 Elsevier Scienc e B.V. All rights reserved.