Ambipolar diffusion, cloud cores, and star formation: Two-dimensional, cylindrically symmetric contraction. II - Results and a length scale for protostellar cores. III - A further parameter study and magnetically controlled accretion rate

Abstract

Ambipolar diffusion initiates the formation and collapse of cores in self-gravitating, thermally supercritical model clouds which would be in exact equilibrium states if the magnetic field were frozen in the matter. The contraction is followed to an increase of the central density by a factor of 10 6 (e.g., from 3 × 10 3 to 3 × 10 9 cm -3 ). The results are interpreted in terms of thermal, magnetic, and Alfven length scales.