Cooling contribution (in %) of the three most important cooling processes or species at each atmospheric layer as a function of pressure obtained from the Cloudy NLTE (top) and LTE (bottom) runs. The label “FF” indicates free-free cooling from H and He. The cooling fraction of any given species is artificially set equal to zero in the atmospheric regions where the species producing the cooling is not one of the three most important. Magnesium is the species most contributingto the cooling of the upper atmosphere.