Plots show the effect varying the flow speed, v_z has on the evolution of v_θ. Each plot is shifted by a value of 2.175, which is the maximum amplitude of v_θ seen in any of the simulations. The increase in v_z shows that the duration for the amplification to occur and “push” the gas-dynamic shock beyond the low-chromosphere reduces and the maximum amplitudes of the wave increases. An initial flow speed of v_z1 = 2.25 c_S1 is the lower limit for the instability to occur with the chosen Alfvén and sound speeds.