SWITCH SHOCKS IN MOLECULAR CLOUDS .2. IMPLICATIONS

A method for analyzing shocks in molecular clouds with oblique magnetic fields has been developed (Paper 1). Here I derive some of the basic observable properties of these C-type waves. In particular, switch shocks, in which the initial motion is parallel to the field lines, is explored and compared to the transverse case. The process of switching on the tangential component, to enable field-cushioning, leads to higher temperatures over a narrower shocked layer. Nevertheless ambipolar diffusion and acceleration of molecular material via shocks remains effective even along field lines. Switch shocks are present for a wide range of cloud parameters, with typical breakdown speeds of 30 and 50 km s-1 for molecular hydrogen densities of 10(6) and 10(4) cm-3, respectively. These are comparable to the standard transverse values of 45 and 50 km s-1 under the same conditions. Implications for molecular emission lines are explored. Switches and transverse shocks have similar properties. Switches produce less H-2 emission and significantly higher excitation levels are possible. However, a strong low-temperature coolant (such as H2O) iS necessary to avoid the appearance of a C* or J-type subshock. Ramifications for star formation and circumstellar disks are discussed. Torsional switches and poloidal switches extract angular momentum and magnetic flux from molecular cloud cores at super-Alfvenic speeds.