Twilight airglow: 1. Photoelectrons and [O I] 5577-Angstrom radiation

Abstract

A payload consisting of a number of experiments to study the earth's atmosphere was launched from White Sands on February 8, 1971, at dawn. The differential photoelectron flux spectrum was measured as a function of altitude. The energy distribution revealed the N2 vibrational structure appearing at 2.8 volts, rising to a maximum at 4 ev, decreasing to an 8-volt-wide plateau at 20 volts, and then further decreasing. The ion and electron density distributions were measured simultaneously. An optical measurement of [O I] 5577-A radiation was made. Both electron impact on atomic oxygen and dissociative recombination of O2+ were found to produce this emission above 150 km. The recombination rate for the O(¹S) found from a nightglow profile reported here is 2.5 ± 1.5 × 10−9 cm³ sec−1, and there is a possible temperature dependence of between Te−0.5 and Te−0.7. Between 140 and 120 km, photodissociation is a source of 5577 radiation. Chapman three-body recombination is dominant below 120 km.