Analysis of particle and photometer data from ESRO 1A (Aurorae) shows (in agreement with several other studies) that the ratio of integrated auroral intensity at λ 4278 Å and particle precipitation is constant (within ± 50%) and more or less independent of the particle energy spectrum. However, in several cases it is found that the electron flux below approximately 2–3 keV at satellite altitude (400–700 km) is not important in the production of auroral N 2 + emission as observed from the satellite. These facts can be explained either by marked change in composition and/or density in the auroral E-region during disturbed conditions, or by backscattering/reflection of low energy electrons above 150 km due to significant potential differences parallel to the earth magnetic field at auroral latitudes. It is argued that the latter explanation is most likely.