The interaction of strong shock waves, such as those generated by the explosion of supernovae, with interstellar clouds is a problem of fundamental importance in understanding the evolution and the dynamics of the interstellar medium (ISM) as it is disrupted by shockwaves. The physics of this essential 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 mechanisms reponsible?
(2) What is the rate of momentum transfer to the cloud?
(3) What is the appearance of the shocked cloud, it's morphology and velocity dispersion?
(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 we have embarked on a comprehensive multi-dimensional numerical study of the shock-cloud problem (Klein et al. 1990,1992,1994,1995) using high resolution adaptive mesh refinement (AMR) hydrodynamics. We present results of a series of Nova laser experiments investigating the evolution of a high density sphere after the interaction of a strong shock wave, thereby emulating the supernova shock-cloud interaction. The Nova laser is utilized to generate a strong Mach 10 shock wave which travels along a miniature beryllium shock tube, 750 microns in diameter, filled with a low density plastic emulating the ISM. Embedded in the plastic is a copper microsphere (118 microns in diameter) emulating the interstellar cloud. The evolution of the sphere as well as the shock wave trajectory are diagnosed via side-on radiography. We present new experimental results of this interaction out to several cloud crushing times and compare the experimental results to detailed two and three dimensional radiation hydrodynamic simulations using both arbitrary Lagangian-Eulerian hydrodynamics (ALE) as well as high resolution AMR hydrodynamics. We discuss the key hydrodynamic instabilities instrumental in destroying the cloud and show the importance of inherently 3D instabilites and their role in cloud evolution. We discuss the relationship of these new experiments and calculations to recent Rosat X-ray observations in the Cygnus Loop.Back to Fluid Mechanics Seminar Page