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Grain destruction in radiative shock waves is an important step in the life cycle of interstellar dust. Dust grains entering a shock front are efficiently accelerated to high velocities in the compressive section of the radiative shock through the betatron process. Binary collisions between fast moving grains are then effective in vaporizing and fragmenting a significant fraction of the grain population. Physical processes involved in these collisions and the resultant change in the grain size distribution are poorly understood at present. In particular, the grain fragmentation in grain-grain collisions has not even been considered although this process appears to be important.
We have developed a mathematical formalism to study the evolution of the grain size distribution in radiative shock waves. The integro-differential equations governing this evolution have been solved numerically, with the grain fragmentation and vaporization included in our calculations. Our treatment of grain fragmentation and vaporization is based on our analysis of physical processes involved in grain-grain collisions. The propagation of a shock wave induced by a high-velocity impact plays a prominent role in this analysis. We discuss how fragmentation process affects the grain size distribution and the total grain mass returned to the gas phase in radiative shocks.
This research is funded by NASA RTOP \#188-44-53-05.
