Illustration of the model atmosphere. Panel a: vertically emergent intensity in the 5000 Å continuum. Panel b: vertical magnetic field strength where the optical depth at 5000 Å is unity. Panel c: lowest height of the first occurrence of a temperature of 0.5 MK. The zero point of the height scale is defined as the average height of where the optical depth at 5000 Å is unity over a weakly magnetized patch. The red areas in panel c show where the CME arm is located in the original model atmosphere.