On atmospheric loss of oxygen ions from earth through magnetospheric processes

In Earth's environment, the observed polar outflow rate for O+ ions, the ma in source of oxygen above gravitational escape energy, corresponds to the L oss of similar to 18% of the present-day atmospheric oxygen over 3 billion years. However, part of this apparent Loss can actually be returned to the atmosphere. Examining loss rates of four escape routes with high-altitude s pacecraft observations, we show that the total oxygen Loss rate inferred fr om current knowledge is about one order of magnitude smaller than the polar O+ outflow rate. This disagreement suggests that there may be a substantia l return flux from the magnetosphere to the low-latitude ionosphere. Then t he net oxygen Loss over 3 billion years drops to similar to2% of the curren t atmospheric oxygen content.