Far Ultraviolet Remote Sensing of the Nighttime Ionosphere Using the OI 130.4‐nm Emission

Abstract

AbstractRoutine monitoring and forecasting of the ionosphere is becoming imperative for our society due to the rapid increase of our reliance on space‐based technologies. In the last two decades, satellite remote sensing of the OI 135.6‐nm airglow emission has been used as a primary means for inferring the nighttime ionosphere on a global scale. By contrast, the OI 130.4‐nm emission, another prominent airglow feature, has long been suggested to be possibly useful for ionospheric remote sensing but has rarely been studied in the literature, partially due to the complexity of the radiative transfer effects involved in the interpretation of this emission. In this study, we explore the use of OI 130.4‐nm emission for nighttime ionospheric remote sensing by analyzing the data observed by the Global Ultraviolet Imager (GUVI) aboard NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission using a newly developed radiative transfer model. We demonstrate through data analysis and theoretical investigations that limb observations of the OI 130.4‐nm emission can be used to complement the OI 135.6‐nm emission for a better characterization of the spatial variation of nighttime ionosphere and that nadir observations of the OI 130.4‐nm emission can be used to estimate the total electron content (TEC) and the peak density (NmF2) in smoothly varying ionospheric regions more accurately than the OI 135.6‐nm emission. We further propose techniques for estimating the ionospheric peak height (hmF2) using nadir observations of the two emissions. Our results can provide useful information for future ionospheric remote sensing missions.