  Convective perturbations arising from nuclear shell burning can play an
important role in propelling neutrino-driven core-collapse supernova
explosions. In this work, we analyze the impact of vorticity waves on the shock
dynamics and the post-shock flow using the solution of the linear hydrodynamics
equations. We show that the entropy perturbations generated by the interaction
of the shock with vorticity waves may play a dominant role in generating
buoyancy-driven turbulence in the gain region. We estimate that the resulting
reduction in the critical luminosity is 17-24%, which approximately agrees with
the results of three-dimensional neutrino-hydrodynamics simulations.
