### Below you can find a movie related to the following paper:

### Development of the wiggle instability

This movie shows the development of the wiggle instability in one particular case. The most unstable mode in the video corresponds to k_y=pi in the third row of Fig. 3, more or less at the position of the highest peak in the right panel. The linear analysis predicts the wavelength correctly. The shock oscillates and Re(omega) and Im(omega) from the linear analysis also predict well the timescales. Note that only modes that have k_y = N*pi where N is an integer are possible in this simulation due to the finite size of the box in the y direction. The same simulation with inflow-outflow on the left-right boundaries is stable, i.e. changing the boundary conditions makes the instability disappears and is the periodicity that makes it unstable.