An Analysis of Ozone and NO2 Variations during the 2014 Solar Proton Event

Abstract

Background The stratosphere and lower mesosphere serve as critical interfaces linking solar activity, ionospheric disturbances, and variations in ozone concentrations, nitrogen compounds, and, ultimately, surface weather patterns. Fluctuations in stratospheric ozone, along with alterations in other upper atmospheric constituents, directly influence the stratospheric energy balance. These changes may impact stratospheric circulation dynamics, which can subsequently propagate to affect tropospheric climate and weather. Objective The aim of this study is to analyze in situ measurements of total ozone and NO2 in the upper stratosphere and lower mesosphere of the Southern Hemisphere, conducted within the framework of the Belarusian Antarctic Expedition, during the development of the 2014 solar proton event. Additionally, this work seeks to determine the response of total ozone deviations and changes in ozone vertical profiles during intense planetary ionospheric storms. Methods The study utilized spectroscopic measurements of trace gases in the 320–390 nm wavelength range via the zenith-DOAS method. Ground-based zenith-DOAS measurements were conducted using the MARS-B and PION-UV instruments. To evaluate the polar ozone response to ionospheric disturbances, the epoch superposition method was applied, utilizing the ionospheric planetary index Wp alongside average total ozone values over the Southern Hemisphere polar cap (63°S to 90°S), derived from MERRA-2 NOAA reanalysis data. Results The photochemical decay of NO2 during nighttime was experimentally observed, as evidenced by consistently lower NO2 levels in the morning compared to evening values. Synchronous and independent measurements of the slant columns of NO2 and O3 demonstrated a correlation between the temporal variation in their concentrations and the dynamics of the solar proton event. Conclusion Instrumental measurements of ozone and NO2 at upper stratosphere and lower mesosphere altitudes over Antarctica, conducted using MARS-B and PION-UV, indicate that the photochemical decay of nitrogen dioxide occurs during the night following the solar proton event. Given the absence of ground-level sources of ozone and nitrogen dioxide in Antarctica, these findings pertain specifically to stratospheric NO2 and O3 and support a potential role of electrical processes in stratospheric ozone formation. The study concludes that total ozone levels in the Southern Hemisphere polar cap decrease at the onset of ionospheric storms, followed by an increase once the storm subsides. A possible mechanism is proposed for the transfer of solar energy within the middle atmosphere, highlighting the critical role of ozone in this process.