Like many young supernova remnants, SN 1006 exhibits what appear to be clumps of ejecta close to or protruding beyond the main blast wave. In this paper we examine 3 such protrusions along the east rim. They are semi-aligned with ejecta fingers behin
d the shock-front, and exhibit emission lines from O VII and O VIII. We first interpret them in the context of an upstream medium modified by the saturated nonresonant Bell instability which enhances the growth of Rayleigh-Taylor instabilities when advected postshock. We discuss their apparent periodicity if the spacing is determined by properties of the remnant or by a preferred size scale in the cosmic ray precursor. We also briefly discuss the alternative that these structures have an origin in the ejecta structure of the explosion itself. In this case the young evolutionary age of SN 1006 would imply density structure within the outermost layers of the explosion with potentially important implications for deflagration and detonation in thermonuclear supernova explosion models.
