Radial profiles of the m = 2, 4, 6 Fourier coefficients (normalised by the m = 0 component), for the thin disc (left panels), thick-disc stars (middle panels), and total (thin+thick) disc stars (right panels) as a function of time (shown in the colour bar) for the model rthickE0.5. At later times, the peaks of the radial profiles of the m = 2, 4, 6 Fourier coefficients shift towards the outer regions.