Temporal evolution of the Fourier amplitude A_m of the bending modes (top panels) and phase ϕ_m (bottom panels) of the m = 1 (left panels) and m = 2 (right panels) modes. The phase of mode m = 2 ranges between −90° and 90° because of the duplicity of the structures. The white horizontal dashed lines mark the division of the disk at radii of 10 and 20 kpc. The bending m = 1 dominates over m = 2 and shows higher amplitudes at outer radii (R > 7 kpc) excited mainly at the beginning of the studied time span and at later times from 2 Gyr onward. The inner parts show faster retrograde bending waves with the highest amplitude happening around 4 Gyr of lookback time.