Latitudinal distribution of auroral and airglow emissions: The ‘soft’ auroral zone

Abstract

A photometric latitude survey in the northern hemisphere was made from a jet aircraft to study atmospheric emissions. No diffuse, particle-excited emissions were detected above 80° invariant latitude at night during January through March 1968, and an upper limit on the energetic-particle energy influx during this period is therefore calculated to have been ∼2 × 10−3 erg cm−2 sec−1 (for both protons and electrons). Soft electrons with energies ∼0.6 kev precipitate in a zone that is located poleward of the normal auroral zone, resulting in a zone of enhanced λ6300 O I emission. Averaged latitudinal distributions for Hβ, λ4278 N2+, λ5577 O I, λ6300 O I, and λ5890–96 Na between 13°N and 87°N geom. are presented, and their significance relevant to direct satellite measurements of particle fluxes is discussed.