Magnetohydrodynamic shocks

Although steady state in the chemistry is rapidly achieved (timescale 10 yr), the dynamical situation varies continually throughout the cycle. On any line of sight, observations will include all phases described here. Although much detailed work has been performed on static clouds (cf. van Dishoeck 1988, this volume) and on hydrodynamic and magnetohydrodynamic shocks (Flower 1988, this volume) in diffuse clouds, a comprehensive model of the total line of sight, involving both compression and rarefaction in the gas, and both accretion of carbon and removal of mantles in shocks, has yet to be carried out. 

Draine, B. T, and Katz, N. (1986). Magnetohydrodynamic shocks in diffuse clouds I. Chemical processes, Astrophys. J. 306,655. 

We note that later too—even in recent years—Ya.B. has turned his attention to this sphere of problems we have here a paper by Ya.B. devoted to diffusion in a one-dimensional fluid flow (6), papers on hydrodynamics and thermal processes in shock waves which are reviewed in the next section, and on the hydrodynamics of the Universe in the next volume in the section devoted to astrophysics and cosmology. Here we consider only Ya.B. s papers on magnetohydrodynamics or, more precisely, on the problem of magnetic... 

More recently, shock waves and other details associated with flows at speeds greater than that of sound in the fluid (supersonic flows) have been introduced. Still more recently, the interaction of magnetic fields with the flow of charged particles has been extensively studied and formulated into a body of theory known as magnetohydrodynamics. In connection with the space effort and the performance of vacuum systems, it became necessary to study the flow of fluids at such low pressures that the mean free path of molecular motion plays an important role. At the other extreme, the flow of fluids must be studied under such high pressures that densification sufficient to cause solid-like behavior results. This latter area is still to be explored. 

Hydrodynamic and magnetohydrodynamic (MHD) shocks are important in the time-dependent chemistry of the diffuse interstellar medium. The time scales are very... 

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