HIRIS rocketborne spectra of infrared fluorescence in the O₃(ν₃) band near 100 km

High‐resolution O 3 (ν 3 ) spectral emission data, obtained between 80 and 125 km during an aurora by the rocketborne HIRIS cryogenic interferometer spectrometer, have been analyzed by a spectral simulation/least squares technique. Data obtained below 110 km exhibit behavior independent of local auroral strength and thus appear to represent quiescent nightglow. The derived vibrational state population distributions for levels υ 3 ′ ≥ 1 can be expressed as vibrational “temperatures” of 400–600 K. This result is interpreted in terms of formation of O 3 (υ 3 ′) by three‐body recombination of O with O 2 as well as other radiative and collisional processes. Additional data, obtained near 120 km and sampling intense auroral arcs, indicate a hitherto unexpected auroral enhancement of O 3 (ν 3 ) fluorescence intensity and vibrational state distribution.