Observational determination of the turbulent ambipolar diffusion scale and magnetic field strength in molecular clouds

Abstract

We study the correlation of the velocity dispersion of the coexisting molecules H13CN and H13CO+ and the turbulent energy dissipation scale in the DR21(OH) star-forming region. The downshift of the H13CO+ spectrum relative to H13CN is consistent with the presence of ambipolar diffusion at dissipation length scales that helps the process of turbulent energy dissipation, but at a different cutoff for ions compared with the neutrals. We use our observational data to calculate a turbulent ambipolar diffusion length scale L′≈ 17 mpc and a strength of Bpos ≈ 1.7 mG for the plane of the sky component of the magnetic field in DR21(OH). © 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A.