Spatial relation between coronal emissivity and opacity in He i 1083 nm. Top row: frequency integrated and cross-section weighted photon losses L_csw, integrated along the y-axis a); the x-axis b) and the z-axis c); on an inverted brightness scale. Panel d): the resulting angle-averaged radiation field at the largest height in each column where T = 15 kK, showing the spatial variation of the ionising radiation impinging on the chromosphere. Panel e): total depth-integrated column density of the lower level of the He i 1083 nm. Panel f): vertically emergent intensity at the nominal line core of the He i 1083 nm. This figure has an accompanying movie available online. The movie shows 2D cross-cuts through the simulation domain, with Λ_csw in red and the He i 1083 nm lower level population in blue.