Turbulent shock processing, relevant to shock-cloud interactions*

The evolution of interstellar clouds following the passage of a supernova shock is an important astrophysical phenomenon; the shock passage may trigger star formation and the post-shock flow surrounding the clouds will strip them of material, effectively limiting cloud life times. Experiments conducted at the Omega laser attempt to (a) quantify the mass-stripping of a single cloud, and (b) simulate the effects of nearby clouds interacting with each other. A strong shock is driven (using 5 kJ of the 30 kJ Omega laser) into a cylinder filled with low-density foam with embedded 120 $\mu $m Al spheres simulating interstellar clouds. The density ratio between Al and foam is $\sim $9. Material is continuously being stripped from a cloud at a rate which is inconsistent with laminar models for mass-stripping; the cloud is fully stripped by 80 ns-100 ns, ten times faster than the laminar model. A new model for turbulent mass-stripping is developed [1,2] that agrees with the observed rate and which should scale to astrophysical conditions. Two interacting spherical clouds are observed to turn their upstream sections to face each other, a result that is completely opposite of earlier work [3] on two interacting cylinders. The difference between these two cases is explained by the relative strength of shocks reflected from the clouds. [1] J.F. Hansen et al, ``Experiment on the Mass-Stripping of an Interstellar Cloud Following Shock Passage,'' \textit{Astrophys. J. }\textbf{662,} 379-388 (2007). [2] J.F. Hansen et al, ``Experiment on the mass-stripping of an interstellar cloud in a high Mach number post-shock flow,'' \textit{Phys. Plasmas }\textbf{14,} 056505 (2007). [3] C. Tomkins et al, ``A quantitative study of the interaction of two Richtmyer-Meshkov-unstable gas cylinders,'' \textit{Phys. Fluids.} \textbf{15,} 986 (2003).