Neutral Exospheric Temperatures From the GOLD Mission

Abstract

AbstractObservations of far‐ultraviolet (FUV) dayglow by the Global‐scale Observations of Limb and Disk (GOLD) mission provide a new opportunity for determining how geomagnetic storms alter the temperature of the thermosphere and enable us to quantify the global‐scale response of the thermosphere to solar extreme‐ultraviolet (EUV) variability. Relative temperature changes can be measured by monitoring changes in the scale height of molecular nitrogen as observed in Lyman‐Birge‐Hopfield (LBH) band emissions. Mean scale heights are derived from GOLD FUV observations using Chapman function fits to altitude profiles of LBH band emissions. We provide an overview of the theoretical basis for the GOLD Level 2 exospheric temperature algorithm, including a generalization of a standard Chapman function fitting technique to allow for gravity and temperature gradients. Effects on derived exospheric temperatures from instrument artifacts and stars in the GOLD field of view are reviewed. We also discuss GOLD Level 1C LIM and Level 2 TLIMB data products and present representative examples of each. We show that exospheric temperatures vary with local time and correlate weakly with solar activity but more strongly with geomagnetic activity. Finally, we present results from a preliminary data product validation that show good qualitative agreement with predictions from a global reference atmospheric model.