Abstract
Abstract. An auroral electron excitation model, combined with simple equilibrium neutral and ion chemistry models, is used to investigate the optical emission processes and height profiles of I(5577 Å) and I(7620 Å) in the 90 to 100 km altitude region. It is shown that the apparent discrepancies between ground-based and rocket-borne auroral observations of the I(7620 Å)/I(5577 Å) ratio are due to the extreme height variation of this intensity ratio in the 90 to 100 km region.Key words. Atmospheric composition and structure (airglow and aurora)
Highlights
Ground-based observations of medium to bright intensity aurora by Gattinger and Vallance Jones (1974) indicate I(7620 AÊ )/I(5577 AÊ ) @ 10, whereas rocketborne observations by Feldman (1978) report that the ratio is about two
As the removal of the airglow component from these rocket observations is straightforward, since the airglow is at a signi®cantly lower altitude than the auroral form as monitored by on-board N2 1NG photometers, it is not believed that the reported intensity ratios are contaminated by a large airglow signal
From the results of our model calculations, there is no contradiction in the reported I(7620 AÊ )/I(5577 AÊ ) auroral intensity ratios for ground-based and in-situ rocket observations
Summary
Ground-based observations of medium to bright intensity aurora by Gattinger and Vallance Jones (1974) indicate I(7620 AÊ )/I(5577 AÊ ) @ 10, whereas rocketborne observations by Feldman (1978) report that the ratio is about two. Other rocket-borne observations have suggested the ratio is less than unity (Deans et al, 1976; McDade et al, 1985). As the removal of the airglow component from these rocket observations is straightforward, since the airglow is at a signi®cantly lower altitude than the auroral form as monitored by on-board N2 1NG photometers, it is not believed that the reported intensity ratios are contaminated by a large airglow signal. In earlier model work for normal aurora, lower border near 110 km, Gattinger et al (1996) obtained intensity ratios for Correspondence to: E.
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