The Global Pattern of 6300 Å Atomic Oxygen Emission as Seen from the Isis-2 Spacecraft

Abstract

The 6300 Å line of O is a useful detector of low energy ionospheric processes. The 100 eV magnetosheath-type electrons incident in the dayside cleft produce red auroras, and red-enhanced auroras appear as polar cap arcs and at high latitudes on the nightside. During storms, thermal excitation inside the plasmapause generates SAR Arcs. Outside the plasmapause conjugate photoelectrons produce significant increases of 6300 Å emission by electron impact. Dissociative recombination of O₂ ⁺ produces 6300 Å emission, dramatically evident at the equator. All of these mechanisms are identifiable in the ‘instantaneous’ global maps produced by the Red Line Photometer (Shepherd et al., 1973a) on the ISIS-2 spacecraft. The Auroral Scanning Photometer (Anger et al., 1973) also yields data at 5577 Å and 3914 Å. Parameters measured in the circular orbit at 1400 km include (Shepherd et al., 1973b) electron density and temperature, ion composition and temperature, and energy spectra of electrons and protons; while the electron density profile down to the ionosphere is traced by the topside sounder.