Comparative Study of Ion and Electron Average Pressure Variation in the Inner Magnetosphere During CIR- and ICME-Driven Storms Observed by the Arase Satellite

Abstract

Using Arase satellite observations, this study provides a comprehensive statistical analysis of ions (H⁺, He⁺, O⁺) and electron contributions to the total ring current pressure during storms with two different drivers. The results demonstrate the effect of different solar wind drivers on the composition, energy distribution, and spatial characteristics of the ring current. Using 32 CIR- and 30 Interplanetary Coronal Mass Ejection (ICME)-driven storms, we characterize the ring current pressure evolution during the prestorm, main, early-recovery, and late-recovery storm phases as a function of magnetic local time and L-shell. In CIR-driven storms, H⁺ ions are the dominant (∼70%) contributor to the total ring current pressure during main/early recovery phases and increasing to ∼80% during late recovery. In contrast, the O⁺ pressure (E = 20–50 keV) response is significantly stronger in ICME-driven storms contributing ∼40% to the overall pressure during the main/early recovery phases and even dominate (∼53%) in certain MLT sectors. Additionally, ICME-driven storms tend to have peak pressure at lower L-shells (L ≈ 3–4), while CIR-driven storms show pressure peaks at slightly higher L-shells (L ≈ 4–5). Interestingly, electron pressure also plays a notable role in specific MLT sectors, contributing ∼18% (03–09 MLT) during the main phase of CIR-driven storms and ∼11% (21–03 MLT) during ICME-driven storms. The results highlight that the storm time electron pressure plays a crucial role in the ring current buildup. Another noteworthy feature of this study is that Arase's fine-energy resolution and broad coverage enable a detailed investigation of energy-dependent ring current dynamics.