NONLOCAL THERMODYNAMIC-EQUILIBRIUM PROCESSES IN OZONE - IMPLICATIONS FOR THE ENERGY BUDGET OF THE MESOSPHERE AND LOWER THERMOSPHERE

The conversion of chemical potential energy and infrared radiative energy to kinetic energy by nonlocal thermodynamic equilibrium (non-LTE) processes involving ozone is a potentially significant source of heat in the terrestrial upper mesosphere and lower thermosphere. Heating rates in excess of 6 K d-1 could occur near the mesopause if all potential energy is converted to heat. Calculation of the heating rate requires knowledge of the processes which convert chemical potential energy to internal energy of ozone during the exothermic recombination reaction that forms ozone. In addition, the rates at which ozone exchanges internal energy with its surroundings through collisional and radiative processes must be known. The lack of a detailed data base of kinetic and spectroscopic information limits the ability to accurately model the heating by ozone. Therefore heating rates are calculated and compared using two different statistical equilibrium models previously applied in the analysis of measurements of limb emission from ozone. The calculated heating depends strongly on the assumed distribution and relaxation of energy in the quasi-nascent ozone molecule. Finally, in the absence of a detailed data base of rate coefficients it may be possible to estimate the heating rate due to non-LTE processes in ozone from appropriate satellite measurements of the ozone concentration and of the infrared emission from ozone in the 9-12-mu-m spectral interval.