Diurnal Response of CO2 Radiative Cooling to September 7-9, 2017 Storm

Abstract

The solar and magnetospheric energy deposition into Earth’s high latitude region modulates the magnetosphere-ionospherethermosphere system during geomagnetic storm periods. One of the impacts of geomagnetic storm is the significant thermosphere temperature increment. This temperature increase is regulated by radiative cooling emissions via CO2 at 15 µm and NO 5.3 µm. We utilized CO2 15 µm radiative emissions observations by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument onboard NASA’s TIMED (Thermosphere Ionosphere Mesosphere Energetics Dynamics) satellite, to investigate the diurnal response during September 7-9, 2017 storm. The volume emission rate of CO2 emission, in the altitude of 100-140 km, is integrated vertically to estimate cooling flux. The geomagnetic storm induced a significant enhancement in CO2 emission across all latitudes and altitudes considered. While the storm typically has stronger impacts on high latitudes, the response in CO2 emission was notably stronger in mid and low latitude regions both during day and night. The nighttime value is generally lower, with a faster response time, as compared to the day time counterpart. Further a strong hemispheric asymmetry is observed both during day and night. This study highlights a complex interplay of solar and magnetospheric influences on the diurnal variation of Earth's upper atmosphere.