Integrated intensity along the line-of-sight (normalised with respect to the equilibrium value) for the 0° angle case for the base model − 171 (left panels) and the base model − 193 (right panels) for two specific rays: ray 1 crossing a node (top most panels) and ray 2 crossing an anti-node (bottom panels), shown with crosses in Figs. 3 and 4. Different colours denote different pixel sizes: 0R,1R,2R, and 3R in red, purple, blue, and green, respectively, where R = 1 Mm ≈ ℓ denotes the radius of the cylinder and 0R denotes the spatial resolution in the high resolution model: 2.5 km. The black curve denotes the density profile at the centre of the cylinder and the same location along the axis of the cylinder as rays 1 and 2. The intensity range of the top panels is set significantly narrower than that of the bottom panels in order to show the low intensity modulation at the nodes.