1994A&A...289..237J

We present a magnetohydrodynamical model of molecular clouds accounting for the interaction of dense clumps with the ambient medium on larger scales. The physical model is based on the creation of MHD-waves due to the statistical motion of magnetized clumps. The velocity fluctuations are derived in quasilinear approximation and agree well with observations. The velocity dispersion depends on few parameters only and is thus very robust against variations of the model. This result of a discrete 2-scale theory is then used to develop a hierarchical model of molecular clouds. Integrating over the excitation of fluctuations on all scales yields the power spectrum of the total velocity fluctuations as a function of scale. Comparison of the observed scaling laws with the new derived one show a good agreement. A stability analysis of molecular clouds including the effect of the turbulent pressure shows that the clouds can be stabilized on all scales by the hydromagnetical wave field.