XZ-profile of the 3D MHD snapshot along the cut at Y = 0.9 Mm, marked by a horizontal line in Fig. 2. a) Electron temperature on a logarithmic scale clipped at 10⁵ K to enhance the contrast at lower heights. b) Electron number density on a logarithmic scale. c) Magnetic field strength on a logarithmic scale. Overplotted dot-dashed, dashed, solid, and dotted lines in panels a)–c) depict the effective formation heights for the radiation at 0.4 mm, 1.0 mm, 3.6 mm, and 10 mm, respectively. d) Brightness temperature at the wavelengths 0.4 mm (dot-dashed), 1.0 mm (dashed), 3.6 mm (solid), and 10 mm (dotted). In panels a)–c) the y-axis scale is expanded. In all panels vertical dashed lines mark the locations of the different structures presented in Figs. 7–11.