The transverse acceleration instability for bow shocks in the nonlinear regime

We continue our study of the stability of thin isothermal bow shocks. We follow the transverse acceleration instability (TAI) found in the linear analysis to the nonlinear regime. We use numerical simulations to solve the nonlinear Euler equations. Indeed, we find that thin isothermal bow shocks are also unstable in the nonlinear regime. The growth rates for the instability are higher for larger values of v*/v(w), where v*, v(w), are the stellar and wind velocities, respectively, as expected from the linear analysis. We apply our results to observations of bow shocks and find that the size of the clumps in alpha Cam is compatible with the TAI if its viscosity is due to turbulence in the mixing layer between the shocked ambient medium fluid and the shocked wind fluid.