Middle atmosphere heating by exothermic chemical reactions involving odd‐hydrogen species

We calculate the rate of heating that occurs in the middle atmosphere (50 – 105 km) due to four exothermic reactions involving members of the odd‐hydrogen family. These reactions are O + OH → O 2 + H, H + O 2 + M → HO 2 + M, H + O 3 → OH + O 2 , and O + HO 2 → OH + O 2 . The energy lost from vibrationally excited OH (produced in the third reaction) by spontaneous emission is explicitly accounted for by using detailed kinetic models, so that only a portion of the exothermicity of this reaction is converted into heat. The heating rates due to these four reactions are found to rival the oxygen‐related heating rates conventionally considered in models of the middle atmosphere, e.g., those due to O + O + M → O 2 + M, O + O 2 + M → O 3 + M, O 2 + hv → O + O, and O 3 + hv → O + O 2 The conversion of chemical potential energy into molecular translational energy (heat) by these odd‐hydrogen reactions is a significant source of energy in the middle atmosphere which has not been previously considered.