A phenomenological model of the enhanced airglow produced by the Department of Commerce ionospheric modification facility is presented. This model is based primarily on airglow data taken from two sites for triangulation. These data show that it is not necessary for the region in which RF power is deposited (interaction region) to be coincident with the region in which the modified airglow is emitted (excitation region). The two are coincident at altitudes below 280 ± 15 km; but, as the interaction region rises, the two may separate with the excitation region remaining at altitudes around 280 km. It is also shown that a non‐Maxwellian energy distribution for electrons is generated by the transmitter. Further, using this model, we present estimates of the efficiency for converting the radio wave energy into energetic electrons. This can typically be 1%, although observations indicating efficiencies 10 to 15 times higher have been made. A variety of experimental data which are not clearly understood are also presented.

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An experiment designed to modify the ionosphere by depositing large amounts of energy into the ionospheric electrons is described elsewhere in this journal [Utlaut, 1970]. As part of the diagnostic procedure a number of optical experiments were performed. This note presents preliminary results from one of the experiments. The experiment to be described here was speculative in nature. On the basis of current knowledge of processes by which O2(1Δg) (which yields radiation at 1.27 μ) can be excited, it was not expected that observable amounts of radiation would be produced. However, observations of 127‐μ radiation under auroral conditions [Noxon, 1970; Megill et al., 1970] also present an anomaly; the observed intensities are considerably larger than can be easily explained. On the basis of the auroral observations and on the premise that the excitation during auroras is due to ‘heated’ ambient electrons, observations of 1.27‐μ, radiation were performed during the operation of the transmitter.

The effective electron loss rates from 64 to 100 km have been measured for daytime and nighttime conditions during polar cap absorption events by using rocket‐borne proton spectrometers and Faraday rotation experiments. The daytime results agree within a factor of 2 with the Adams and Masley (1965) profiles in the 64‐ to 80‐km region where they overlap. The nighttime loss rates coincide with the daytime loss rates down to ∼75 km and then increase rapidly below that altitude. The loss rates above 90 km imply a dissociative recombination coefficient of 4.1 (±1.3)×10−7 cm3/sec. The coincidence of the day and night profiles down to 75 km suggests that no photodetachment processes are of significance during the daytime.

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