Properties of the atmosphere along the cut indicated in Fig. 1. a) Mass density. b) The solid black curve indicates the internal energy per mass unit, with the zero point at neutral atoms in the ground state. Red: ionization energy of hydrogen; black dotted: excitation energy of atomic hydrogen; blue: kinetic contribution of all atoms, molecules and electrons; green: contribution of the rotational, vibrational and dissociation energy of H₂ molecules. c) Vertical gas velocity, positive means upward. d) Gas temperature. e) Gas pressure. f) Compression rate  − ∇·u.