  We present plane-parallel equilibrium models of molecular clumps that are
supported by Alfven waves damped by the linear process of ion-neutral friction.
We used a WKB approximation to treat the inward propagation of waves and
adopted a realistic ionization structure influenced by dissociation and
ionization due to photons of external origin. The model clumps are larger and
less centrally condensed than those obtained for an assumed ionization
structure, used in some previous studies, that is more appropriate for dark
regions.
