The 630 nm dayglow

The daytime thermospheric emission at 630 nm from the (³ P ‐¹ D ) transition of atomic oxygen is examined using data from the Atmosphere Explorer C and E spacecraft. Observed altitude distributions of the emission rate measured using the Visible Airglow Experiment are compared with those calculated from in situ measurements of ion and neutral densities and temperatures, and from a model of the photon and photoelectron flux. Good agreement is obtained for most orbits with photoelectron impact on O, photodissociation of O 2 , and dissociative recombination of O 2 + providing most of the production. Implications for some of the controversial points of O(¹ D ) chemistry, such as the solar EUV and Schumann‐Runge continuum flux, the yield of O(¹ D ) from the reaction of N(² D ) with O 2 , the value of spontaneous transition coefficients, and the rate of quenching by O(³ P ) are discussed.