An auroral source of hot oxygen in the geocorona

Abstract

The high‐energy proton‐hydrogen (H+/H) beam associated with proton auroral precipitation transfers momentum in elastic and inelastic collisions with ambient thermal atomic oxygen in the high latitude thermosphere. This process provides a localized novel source of hot oxygen atoms in addition to exothermic photochemistry, charge exchange and momentum transfer from O+ ion precipitation and charge exchange with accelerated ionospheric O+ ions. We suggest that this source contributes to the population of the hot oxygen geocorona and to the flux of escaping oxygen atoms. For an incident proton energy flux of 1 mW m−2 and a mean energy Emean ≈ 5 keV, we calculate a density of hot oxygen atoms with energy above 1 eV of 2.0 × 103 cm−3 and a mean kinetic energy of about 3.5 eV at 700 km. The total upward flux of hot oxygen atoms with energies higher 1 eV is estimated as 3.5 × 108 cm−2 s−1.