Statistical Structure of Nighttime O2 Aurora From SABER and Its Dependence on Geomagnetic and Solar Activities in Winter

Abstract

AbstractO2 aurora is one kind of important molecular aurorae that is not fully understood yet. It is hard to be investigated due to the contamination by nightglow. In this work, we studied O2 aurora based on the observations of O2 emission at 1.27 μm from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument during the nighttime over 18 years. The horizontal structure of O2 auroral zone is given for the first time, and the vertical profile of O2 auroral volume emission rate is obtained after removing O2 nightglow contamination. The O2 auroral intensity and the peak height and peak volume emission rate of the vertical profile averaged over the O2 auroral zone are studied in detail. For Kp Levels 1–5, the O2 auroral peak height varies between 104 and 112 km and is negatively correlated with the auroral intensity and peak volume emission rate. The O2 auroral intensity varies between 0.14 and 5.97 kR, and the peak volume emission rate varies between 0.97 × 102 and 41.01 × 102 photons cm−3 s−1. Furthermore, the dependences of the O2 aurora on geomagnetic and solar activities are analyzed. The O2 auroral intensity and peak volume emission rate exponentially increases with increasing Kp index, whereas the peak height decreases with increasing Kp index. The O2 auroral intensity and peak volume emission rate under solar minimum condition are larger than those under solar maximum condition. The peak height under solar minimum condition is lower than that under solar maximum condition.