Strong Bow Shocks: Turbulence and an Exact Self-similar Asymptotic

Abstract

We show that strong bow shocks are turbulent and nonuniversal near the head but asymptote to a universal, steady, self-similar, and analytically solvable flow in the downstream. The turbulence is essentially 3D and has been confirmed by a 3D simulation. The asymptotic behavior is confirmed with high-resolution 2D and 3D simulations of a cold uniform wind encountering both a solid spherical obstacle and stellar wind. This solution is relevant in the context of (i) probing the kinematic properties of observed high-velocity compact bodies—e.g., runaway stars and/or supernova ejecta blobs—flying through the interstellar medium; and (ii) constraining stellar bow shock luminosities invoked by some quasiperiodic eruption models.