A New Model for Filamentary Molecular Clouds

We develop a theory for filamentary molecular clouds including the effects of ordered magnetic fields, and external pressure. We first derive a form of the virial equation appropriate for filamentary clouds. By comparing with observational results collected from the literature, we find that the fields are likely helical. Secondly, we construct numerical, MHD models of filamentary clouds that agree with the observational constraints. We find that our models produce much more realistic density profiles $r\sim r^{-1.8 to -2}$ than previous models, where the density falls off as $r^{-4}$.