The Northern and Southern Hemispheric Asymmetries of Mesospheric Ozone at High Latitudes During the January 2012 Solar Proton Events

Abstract

AbstractObservations by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and simulations by the Whole Atmosphere Community Climate Model‐eXtended (WACCM‐X) are used to analyze the impacts of the January 2012 solar proton events (SPEs) on mesospheric ozone at high latitudes. The mesospheric ozone at high latitudes decreased evidently with the increasing proton flux and ionization rates during SPEs. The results of SABER and WACCM‐X both showed that maximum mesospheric ozone depletion reached 100% in the North Hemispheric (NH) high latitudes during SPEs while only 40% in the South Hemispheric (SH) high latitudes. The SPEs‐caused ozone changes simply occurred below 85 km and the ozone changes observed by SABER above 85 km may be associated with day‐to‐day variations. WACCM‐X simulations showed NOx (N, NO, and NO2) increased over 600% in both the northern and southern high latitudes during SPEs, while HOx (H, OH, and HO2) increased over 300% in the NH high latitudes and only over 30% in the SH high latitudes. HOx is the main ozone‐depleting substance because the reactions of NOx are less capable of depleting ozone than the reactions of HOx. Due to the difference in sunlight between the northern and southern hemispheres, ozone, HOx, and NOx exhibited significant northern and southern hemispheric asymmetries. Meanwhile, an increase in ozone after the SPEs was reported but not explained by previous studies. Here it is shown that the decreases in the HOx caused the increases in ozone after the SPEs.