Radiation MHD simulation results of network magnetic field region with Bifrost code. Panels a and b show the vertical component of the magnetic field (B_z) and synthetic CO 3–2 R14 line center intensity map. Panels c and d show the strength of B_z and temperature on the slice indicated by the dashed cyan lines in panels a and b. The red and blue contours indicate the positive and negative magnetic fields with 150 G and −50 G, respectively. The magenta arrow in panel b indicates a typical cold bubble from the CO 3–2 R14 line center intensity map, which is located near the edge of the magnetic network. Correspondingly, the temperature of the bubble regions at the height of 500 km is lower than the other regions (magenta arrow in panel d). The green line in panel b indicates the slit showing the relationship of CO 3–2 R14 line center intensity and B_z strength arranged in Fig. 8b.