Passive Scalar Structures in Supersonic Turbulence
  We conduct a systematic numerical study of passive scalar structures in
supersonic turbulent flows. We find that the degree of intermittency in the
scalar structures increases only slightly as the flow changes from transonic to
highly supersonic, while the velocity structures become significantly more
intermittent. This difference is due to the absence of shock-like
discontinuities in the scalar field. The structure functions of the scalar
field are well described by the intermittency model of She and L\'{e}v\^{e}que
[Phys. Rev. Lett. 72, 336 (1994)], and the most intense scalar structures are
found to be sheet-like at all Mach numbers.
