Twilight airglow, 3. [O I] 6300-Angstrom radiation

Abstract

A coordinated rocket experiment measuring the red line of atomic oxygen at 6300 Å, the photoelectron flux, and the ionospheric densities of O2+ and ne was flown into the twilight mid-latitude airglow over White Sands, New Mexico. Analysis of the 6300-Å emission rate profile shows that photoelectron impact excitation of atomic oxygen is the main source of O(¹D) atoms above 240 km; the rate of this source at 265 km is 9.8 × 10−8 s−1. Photodissociation of O2 in the Schumann-Runge continuum is the main source of O(¹D) atoms below 200 km. A value of O2 dissociation rate for the unattenuated solar flux of 2.2 × 10−6 s−1 best fits the observations. Dissociative recombination of O2+ ions is important above 200 km, and the dissociative recombination rate coefficient derived from the measurement is (2.4 ± 1.2) × 10−8 cm³ s−1. With the model N2 densities used in the calculation the quenching rate coefficient was found to be lower than values previously used in similar calculations.