  The interaction between vortex density waves and high-frequency second sound
in counterflow superfluid turbulence is examined, incorporating diffusive and
elastic contributions of the vortex tangle. The analysis is based on a set of
evolution equations for the energy density, the heat flux, the vortex line
density, and the vortex flux, the latter being considered here as an
independent variable, in contrast to previous works. The latter feature is
crucial in the transition from diffusive to propagative behavior of vortex
density perturbations, which is necessary to interpret the details of
high-frequency second sound.
