High-frequency asymptotics of solutions of the Helmholtz equation in a region of caustic shadow. II

Results of the first part of this work for the analytic index of refraction $n(x,z)$ where the complex eikonal in the shadow region behind a caustic is found by the method of characteristics in the two-dimensional complex space $\mathbb{C}^2$, are applied for $n(x,z)$ of finite smoothness. The use of the quadratic approximation for$n(x,z)$ allows one to obtain the zeroth approximation of the asymptotic limit of the wave field behind a caustic in the boundary layer of width $O(\omega^{-2/3})$.