Statistical Properties of Ion Upflow Associated With Subauroral Ion Drift (SAID) in the Northern and Southern Hemispheres

Abstract

The ion upflow has great significance for the transport and exchange of particles during magnetosphere-ionosphere coupling process. Previous studies focus on the ion upflow in the polar region, and find that ion upflow has hemispheric asymmetries. In subauroral region, the ion upflow is closely related with subauroral ion drift (SAID). However, the characteristics of ion upflow associated with SAID in both northern and southern hemispheres are still unknown. Based on the observation of DMSP satellites F16-F18 from 2010 to 2020, we investigate the north-south hemisphere distributions of ion upflow associated with SAID during quiet and disturbed time. The ion upflow rate presents localized features in both hemispheres. The ion upflow rate in the southern hemisphere is slightly higher/lower than that in the northern hemisphere before/after 1900 MLT. The ion upflow velocity in the southern hemisphere shows a clear dependence on magnetic local time (MLT). Furthermore, We find that the hemispheric asymmetry of ion upflow is closely related to the asymmetric configuration of the ionospheric parameters such as plasma density, conductance and solar elevation angle during magnetosphere-ionosphere coupling process. The result also indicates that SAID and sunlight condition play important roles in the ion upflow in subauroral region.