Conjugate photoelectron excitation of O I 4368 airglow emission.

Conjugate photoelectron fluxes are shown to be mainly responsible for the excitation of O I 4368 radiation observed with a grille spectrometer located at Langmuir Laboratory, New Mexico (L equals 1.7). On the basis of observations of O I 7774 and 4368 tropical emissions at Agulhas, Negras, Brazil (L equals 1.1), the contribution of radiative recombination to the New Mexico intensity is shown to be small. Conjugate photoelectron excitation at the Brazilian site has not been observed.