Observed Loss of Polar Mesospheric Ozone Following Substorm-Driven Electron Precipitation

Abstract

Several drivers cause precipitation of energetic electrons into the atmosphere. While some of these drivers are accounted for in proxies of energetic electron precipitation (EEP) used in atmosphere and climate models, it is unclear to what extent the proxies capture substorm-induced EEP. The energies of these electrons allow them to reach altitudes between 55 and 95 km. EEP-driven enhanced ionization is known to result in production of HOx and NOx, which catalytically destroy ozone. Substorm-driven ozone loss has previously been simulated, but has not been observed before. We use mesospheric ozone observations from the Microwave Limb Sounder and Global Ozone Monitoring by Occultation of Stars instruments, to investigate the loss of ozone during substorms. Following substorm onset, we find reductions of polar mesospheric (∼76 km) ozone by up to 21% on average. This is the first observational evidence demonstrating the importance of substorms on the ozone balance within the polar atmosphere.