Normalised synthetic total intensity at 1579 s in Fe IX (row 1), Fe XII (row 2), and Fe XVI (row 3) for the ideal (Col. 1), resistive (Col. 2), and viscous (Col. 3) regimes using the (a) τ_DC and (b) τ_AC boundary drivers. Every panel is normalised by the spatio-temporal maximum of all simulations in each emission line. The bottom left and right panels in (b) are neglected as very little is detected in the Fe XVI line.