LATTICE DYNAMICAL SYSTEM MODELING OF MOLECULAR CLOUDS

Because a comprehensive microscopic treatment of interstellar molecula r clouds is out of reach, an alternative approach is proposed in which most of the crucial ingredients of the problem an considered, but at some 'minimal' level of modelling. This leads to the elaboration of a lattice dynamical system, i.e. a time-dependent, spatially extended, d eterministic system of macroscopic cells coupled through radiative tra nsfer. Each cell is characterized by a small set of variables and supp orts a caricatural chemistry possessing the essential dynamical featur es of more realistic reaction schemes. This approach naturally preclud es quantitative results, but allows heretofore unavailable insights in to some of the basic mechanisms at play. We focus on the response of t he transfer process and the chemistry to a frozen 'turbulent' velocity field. It is shown that the system settles generically into a state w hen the effective coupling between cells is neither local nor global, and for which no single length-scale exists. The spectral lines recons tructed from the spatiotemporal evolution of our model may, depending on the velocity field, exhibit profiles ranging from Gaussian to bimod al with strong realization effects. In the bimodal case, the model int rinsically displays an energy cascade transport mechanism to the cells that cool most efficiently: the feedback of chemistry on radiative tr ansfer cannot be neglected. Finally, extensions of this work are discu ssed and future developments are outlined.