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R. Indebetouw, E.G. Zweibel (JILA, U. Colorado)
I present a numerical simulation of gravitational instability in a thin, cold, magnetized molecular cloud with ambipolar diffusion. The nonlinear evolution of density perturbations shows many of the characteristics evident in the linear analytic theory. The presence of ambipolar diffusion decreases the stability of clouds, and density enhancements grow on a time-scale intermediate to the dynamical collapse and diffusive time-scales. This instability can cause the collapse of dense cores with significant loss of magnetic flux. The magnetic and velocity fields in the simulation become quite complex, and this mechanism is a possible source of magnetized turbulence in clouds. Thermal pressure in the cloud stabilizes the smallest spatial scales, and the instability produces cloud cores or fragments on the order of ~1M\sun.
The author(s) of this abstract have provided an email address for comments about the abstract: indebeto@casa.colorado.edu