The impact of energetic electron precipitation on nighttime atmospheric ozone during geomagnetic storms

Energetic electron precipitation (EEP) during geomagnetic storms plays a significant role in accelerating ozone depletion in the stratosphere at high latitudes. While previous studies predominantly focused on atmospheric responses to individual EEP events, this research aims to establish the statistical patterns of EEP-induced ozone variations during geomagnetic storms. Using data from the Aura Microwave Limb Sounder (MLS) collected between August 2004 and December 2015, we have analyzed the ozone change at latitudes of 55° to 80° under nighttime conditions during 31 geomagnetic storms. The results reveal an average ozone loss rate of approximately 10% at altitudes of 70–80 km during storm periods. Additionally, storm-time ozone depletion exhibits significant seasonal variability, with the most prominent losses occurring during winter-time storms. This study also highlights the complexity of ozone variations during two consecutive geomagnetic storms that occurred in December 2015. The ozone depletion initially appeared above 60 km during the first storm, while the second storm further intensified and extended the depletion down to 40 km. Simulations using the Whole Atmosphere Community Climate Model with the D-region ion chemistry (WACCM-D) indicate that during these consecutive storms, atmospheric concentrations of HOX and NOX undergo two significant enhancements and the cumulative effects become more pronounced than the simple sum of these two storms. Part of these excessive HOX and NOX species accumulate in situ, while the rest is transported downward to react with the ozone, leading to large-scale ozone depletion at low altitudes.