Abstract
Dwarf (or dark) molecular clouds and molecular clumps have a lifetime which is greater than their dynamical time and must therefore be, in an average sense, in mechanical equilibrium. Equilibrium perpendicular to a global magnetic field is by magnetic forces and it is proposed that along the field the gas is supported by an Alfven wave pressure force. A self-consistent analytical model, utilising a WKB approximation, is developed for such support. It is found that Alfven waves are indeed a good candidate for this support, generating model cloud thicknesses consistent with observations. The effect of damping by the linear process of ion-neutral friction is considered. It is found that the damping of the waves is not a necessary condition for the support of the cloud although weak damping is an advantage. The possible sources of these waves are discussed.
Original language | English |
---|---|
Pages (from-to) | 1176-1186 |
Number of pages | 11 |
Journal | Astronomy & Astrophysics |
Volume | 326 |
Publication status | Published - Oct 1997 |
Keywords
- ISM: clouds
- ISM: magnetic fields
- ISM: structure
- MHD
- waves
- STAR-FORMATION
- HYDROMAGNETIC-WAVES
- MAGNETIC-FIELD
- DARK CLOUD
- JEANS COLLAPSE
- DIFFUSION
- CHEMISTRY
- RATES
- GAS