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Ann. Geophys., 23, 781-797, 2005
www.ann-geophys.net/23/781/2005/
© European Geosciences Union 2005
Prediction and modelling of doubly-charged ions in the Earth's upper atmosphere
C. Simon1, J. Lilensten1, O. Dutuit2, R. Thissen2, O. Witasse3, C. Alcaraz4, and H. Soldi-Lose2
1Laboratoire de Planétologie de Grenoble, Grenoble, France
2Laboratoire de Chimie-Physique, Centre Universitaire, Orsay, France
3Research and Scientific Support Department of ESA, ESTEC, Noordwijk, The Netherlands
4Laboratoire LURE, Centre Universitaire Paris-Sud, Orsay, France
Abstract.
We discuss the existence of the doubly-charged ions N2++, O2++ and O++ in the Earth's ionosphere through the theoretical computation
of density profiles over the altitude range 100-500km calculated with the
TRANSCAR model. Photoproductions and electron impact productions
are described in detail. The photochemical equilibrium assumption verified
in this context yields density profiles, validated by comparison to the
measurements of the satellite Atmosphere Explorer. Those three dications are
lost essentially by dissociative recombination and collisions with the
neutrals N2, O2 and O. The metastable lifetime of N2++ is
3s and is estimated at 4s for O2++. A survey of the sensitivity to
geophysical parameters (solar activity, latitude and solar zenith angle) is
also shown. Emphasis is cast on the need for rate constants for chemical
reactions involving doubly-charged ions. The fit of the model yields an
estimated value of
1.06±0.40x10-10cm3s-1 for
the rate constant of the O+++O reaction.
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