Auroral dissociation of molecular oxygen in the polar mesosphere

As has been shown by Kellogg, one of the most effective mechanisms for heating of the polar mesosphere during polar night is the exothermic association of atomic oxygen intensified by the large-scale subsidence of the upper polar atmosphere in winter. Since photodissociation is no longer predominant in the polar regions in winter, the contribution of auroral particles to the dissociation of molecular oxygen is estimated, assuming the atmospheric composition given by Johnson. It is shown that the maximum rate coefficient is of the order of 10−8 (cm3 sec)−1 for protons and electrons of energy spectrum E−n dE, where n≥3, and that the height of maximum dissociation is around 90 km. Consequently, the rate of corpuscular dissociation of oxygen molecules in the upper mesosphere during strong auroral activities is comparable with that of photodissociations, which is mostly due to the Schumann-Runge continuum of solar ultraviolet radiations.