Interaction of supernova remnants with interstellar clouds: From the nova laser to the galaxy

The interaction of strong shock waves, such as those generated by the explo sion of supernovae with interstellar clouds, is a problem of fundamental im portance in understanding the evolution and the dynamics of the interstella r medium (ISM) as it is disrupted by shock waves. The physics of this essen tial interaction sheds light on several key questions: (1) What is the rate and total amount of gas stripped from the cloud, and what are the mechanis ms responsible? (2) What is the rate of momentum transfer to the cloud? (3) What is the appearance of the shocked cloud, its morphology and velocity d ispersion? (4) What is the role of vortex dynamics on the evolution of the cloud? (5) Can the interaction result in the formation of a new generation of stars? To address these questions, one of us has embarked on a comprehen sive multidimensional numerical study of the shock cloud problem using high -resolution adaptive mesh refinement (AMR) hydrodynamics. Here we present t he results of a series of Nova laser experiments investigating the evolutio n of a high-density sphere embedded in a low-density medium after the passa ge of a strong shock, wave, thereby emulating the supernova shock-cloud int eraction. The Nova laser was utilized to generate a strong (similar to Mach 10) shock wave which traveled along a miniature beryllium shock tube, 750 mu m in diameter, filled with a low-density plastic emulating the ISM. Embe dded in the plastic was a copper microsphere (100 mu m in diameter) emulati ng the interstellar cloud. Its morphology and evolution as well as the shoc k wave trajectory were diagnosed via side-on radiography. We describe here experimental results of this interaction for the first time out to several cloud crushing times and compare them to detailed two- and three-dimensiona l radiation hydrodynamic simulations using both arbitrary Lagrangian and Eu lerian hydrodynamics (ALE) as well as high-resolution AMR hydrodynamics. We briefly discuss the key hydrodynamic instabilities instrumental in destroy ing the cloud and show the importance of inherently three-dimensional insta bilities and their role in cloud evolution. We describe the relationship of these new experiments and calculations to recent ROSAT X-ray observations in the Cygnus Loop.