A 3D Numerical Study of Anisotropies in Supernova Remnants

Supernova remnants (SNRs) develop fluid instabilities as they expand against the circumstellar medium (CSM). These instabilities are expected to contribute to anisotropies often observed in SNRs. We study this phenomenon by developing a suite of 3D hydrodynamical models using a novel numerical scheme that will be explained briefly. Construction of angular power spectra for these models reveals that our SNR models exhibit a dominant angular mode, which happens to be a diagnostic of their ejecta density profile. This talk will present results that suggest a Kolmogorov-like turbulent cascade is absent in SNRs. Instead, the fluid instability may be governed by independent growth rates for every angular mode. The talk will then go on to show that perturbations (or clumps) in the density field (whether imposed on the supernova ejecta or the CSM) do not influence the anisotropy of the remnant significantly unless they have a very large amplitude and form large-scale coherent structures.  On the other hand, small scale structures are found to be independent of clumps and are solely governed by the growth and saturation of Rayleigh-Taylor instability.