Dayglow [O I] λλ6300 and 5577 A lines in the early morning ionosphere

Abstract

Data on a developing morning ionosphere have been obtained by rocket measurement of the atomic oxygen red- and green-line airglow emissions and of the composition of the neutral and ionized constituents of the upper atmosphere. The solar zenith angle was 86°. The use of tilting-filter photometers for the optical measurements resulted in reliable and accurate height profiles of the airglow intensity from below 100 to 245 km. The roles of the excitation of both O(¹D) and O(¹S) atoms by the dissociative recombination of O2+ and electron impact were studied by using the λλ6300 and 5577 A data in conjunction with the ion composition measurements. The component of photodissociative excitation of O(¹D) by solar radiation in the Schumann-Runge continuum of O2 absorption was assessed as being approximately twice that determined for a previous rocket experiment. The ion chemistry analysis provided good agreement between the calculated height profile of O(¹S) excitation and the λ5577 A data above 170 km. but, below this height, significant production of O(¹S) through the photodissociation of O2 by solar radiation at wavelengths shorter than 1334 A was apparent.