An auroral source of hot oxygen in the geocorona

V. I. Shematovich, D. V. Bisikalo, J.-C. Gˇrard


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 E mean ~ 5 keV, we calculate a density of hot oxygen atoms with
energy above 1 eV of 2.0 X 10^3 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 X 10^8 cm-2 s-1.

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Geophysical Research Letters, 32, L02105, doi:10.1029/2004GL021912, 2005