Double photoionization and doubly charged ions in the thermosphere

Abstract

We show that a plausible cross section for double photoionization of atomic oxygen, urn:x-wiley:00948276:media:grl1063:grl1063-math-0001 yields the dominant source mechanism for O ++ in the thermosphere. With this large source, harmony is obtained between the measured O ++ concentrations and the large (k ∼ 10 −9 cm³ s −1 ) measured sink (by charge exchange with molecular species) at altitudes above about 250 km.