The emission of oxygen green line and density of O atom determined by using ISUAL and SABER measurements

Abstract

Emissions of the 557.7 nm green line airglow observed by the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) instrument on board the FORMOSAT-2 satellite in May and November 2008 are studied here to derive the density distributions of the atomic oxygen by using atmospheric parameters from MSISE-00 model and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics)/SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) measurements. The May observations were made in 10 days from a fixed orbit of longitude (100° E) with the results showing emission rate and O atom density both peaked at heights of about 90 km over 10° to 20° latitudes in the Northern Hemisphere (NH). In the Southern Hemisphere (SH), the emission rate and density of O atom are both low compared with those in NH. In November, the observations were made as the satellite traveled over all 14 orbits around the earth, covering all longitudes and latitudes of 25° S–45° N. Strong peaks of emission rates and O atoms are found at heights of about 95 km in the mid-latitudes in both hemispheres. In the equator, the airglow layer has a weaker emission rate but with higher altitude compared with those of mid-latitudes. In the lower and upper mesosphere at heights below 85 km and above 105 km, there are more O atoms in the equatorial regions than in the mid-latitudes. And there is a good correlation between the O atom and the temperature structure. A comparison with O atom distribution derived from OH airglow observed by TIMED/SABER at about the same time shows similar results.