Space-based observations of O 2 A (0,0) band emission near the solar terminator and their interpretation

Abstract

The LSO (Lightning and Sprite Observations) experiment under sunset/sunrise conditions from International Space Station (ISS) has provided new information about the emission of the visible and near infrared portions of the optical spectrum. Two CCD cameras have been used in the LSO experiment. One of them had a filter for the Atmospheric O 2 (0–0) band registration (762 ± 5 nm). Observations have been performed at limb- and nadir-viewing geometry. Images obtained by both cameras under sunset/sunrise conditions demonstrate the sharp emission layer at an altitude about 90 km. The images have been obtained when tropospheric, stratospheric and lower mesospheric domains were in the Earth’s shadow, and the upper atmosphere regions were illuminated by the rising or setting Sun. The O 2 A (0,0) band emission layer at 90 km was simulated with known chemistry. The major production process of the airglow is O( 1D) production by ozone photolysis followed by energy transfer from O( 1D) to O 2, generating the metastable excited state, O 2 ( b 1 Σ g + ) . It has been shown that under sunset/sunrise conditions the “secondary ozone maximum” provides the main contribution to the observed O 2 A (0,0) band emission. The images taken with these cameras clearly show a vertical distribution of airglow and demonstrate its appreciable variations with horizontal distance across the cameras field of view. The latter feature may be used as a tool for global monitoring of gravity wave activity at the upper mesosphere/lower thermosphere region.