ALFVEN-WAVE SUPPORT OF A DWARF MOLECULAR CLOUD .1. AN ISOTHERMAL MODEL

Dwarf (or dark) molecular clouds and molecular clumps have a lifetime which is greater than their dynamical time and must therefore be, in a n average sense, in mechanical equilibrium. Equilibrium perpendicular to a global magnetic field is by magnetic forces and it is proposed th at along the field the gas is supported by an Alfven wave pressure for ce. A self-consistent analytical model, utilising a WKB approximation, is developed for such support. It is found that Alfven waves are inde ed a good candidate for this support, generating model cloud thickness es consistent with observations. The effect of damping by the linear p rocess of ion-neutral friction is considered. It is found that the dam ping of the waves is not a necessary condition for the support of the cloud although weak damping is an advantage. The possible sources of t hese waves are discussed.