An auroral enhancement of O 2λ1.27- μm emission

The ground-level zenith radiance of the atmospheric emission at λ1.27 μm was radiometrically observed to increase by a factor of approximately two with the onset of an IBC III ⁺ auroral breakup above Chatanika, Alaska, on 10 March 1975. Time-resolved optical spectra clearly show that the slow component of the enhancement is associated with the (0,0) band of the infrared atmospheric system of O ₂. Photometric and incoherent scatter radar data are used to define the energy-deposition profile and the absolute energy flux for the event. The magnitude of the O ₂λ1.27- μm enhancement compares favourably with the predictions of an auroral excitation model which includes only secondary-electron excitation of molecular oxygen in the O ₂( a¹∆_g) source term.