2010MNRAS.402L..64C

Crutcher et al. used OH Zeeman observations of four nearby molecular dark clouds to show that the ratio of mass to magnetic flux was smaller in the ∼0.1 pc cores than in the ∼1 pc envelopes, in contradiction to the prediction of ambipolar diffusion driven core formation. A crucial assumption was that the magnetic field direction is nearly the same in the envelope and core regions of each cloud. Mouschovias & Tassis have argued that the data are not consistent with this assumption, and presented a new analysis that changes the conclusions of the study. Here, we show that the data are in fact consistent with the nearly uniform field direction assumption; hence, the original study is internally self-consistent and the conclusions are valid under the assumptions that were made. We also show that the Mouschovias & Tassis model of magnetic fields in cloud envelopes is inconsistent with their own analysis of the data. However, the data do not rule out a more complex field configuration that future observations may discern.