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N. Featherstone, J. Blondin, K. Borkowski (NCSU )
We examine the effects of ejecta inhomogeneities on the evolution of supernova remnants, via the use of time dependent hydrodynamic simulations, in order to explain the presence of ejecta knots at radii beyond that of the nominal blastwave, such as those present in the Cassiopeia A supernova remnant. For this investigation, the ejecta's inhomogeneity is due to the presence of clumps much denser than the surrounding ejecta. We have assumed that the ejecta are freely expanding with an initial power-law density profile, with clump sizes of roughly 4% the initial forward shock radius and density contrasts for the clumps ranging from about 20 to 2000. Finally we mention the observational implications of the results for the Cassiopeia A supernova remnant and examine the conditions under which the ejecta are able to remain intact long enough to cross the region between the reverse and foward shocks and produce bulges in the forward shock.