A Comparative Study on the Factors Controlling the Cusp Auroral Intensity Between the Northern and Southern Hemispheres

Abstract

AbstractThe previous study has indicated that the interplanetary magnetic field (IMF) By and solar wind flow speed (Vsw) have crucial effects on the cusp auroral intensity in the Northern Hemisphere. However, it is not clear how these factors influence the cusp aurora in the Southern Hemisphere. Using DMSP/SUSSI observations from 2004 to 2017 during non‐storm periods, we compared the factors affecting the intensity of cusp aurora between the Northern and Southern Hemispheres by dividing the observations into weak‐ and intense‐emission events. We found that the auroral intensity in the southern cusp: (a) has a positive correlation with solar wind power input, (b) is statistically weak under southward IMF conditions, and (c) is critically controlled by the IMF By and Vsw. These results are essentially consistent with those obtained in the Northern Hemisphere. However, the IMF By effect shows apparent interhemispheric asymmetry, that is, the IMF By effect reaches the maximum at 2 nT in the Northern Hemisphere, but at −2 nT in the Southern Hemisphere. Further analysis shows that the 2‐nT deviations disappear after dividing all events by season and the IMF By distributions of intense‐emission events show clear seasonal difference. Based on these results, we suggest that the dependence of the cusp auroral intensity on the IMF By is not only controlled by −Vsw × By field, but also affected by season.