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Abstract A comprehensive statistical study is conducted on O⁺and H⁺outflows obtained from the TEAMS/FAST data during the 23rd solar cycle (1996–2007). The study investigates interhemispheric asymmetry in ionospheric outflows during local summer, winter, and equinox seasons. Data are classified into two distinct periods: the pre‐storm and geomagnetic storm phases. Numerous statistical asymmetries are identified. The findings indicate that the dayside cusp consistently demonstrates more outflow rates of O⁺and H⁺in the northern hemisphere than southern hemisphere during geomagnetic storms in all seasons as well as during the pre‐storm period in the summer season with the exception of H⁺during summer storms. Conversely, the nightside O⁺and H⁺outflow rates are higher in the southern hemisphere during pre‐storm and storm periods in the summer season. Additionally, the dawnside and duskside outflow rates of O⁺and H⁺are predominantly stronger in the southern hemisphere. 

Abstract Previous simulations have suggested that O⁺outflow plays a role in driving the sawtooth oscillations. This study investigates the role of O⁺by identifying the differences in ionospheric outflow between sawtooth and non‐sawtooth storms using 11 years of FAST/Time of flight Energy Angle Mass Spectrograph (TEAMS) ion composition data from 1996 through 2007 during storms driven by coronal mass ejections. We find that the storm's initial phase shows larger O⁺outflow during non‐sawtooth storms, and the main and recovery phases revealed differences in the location of ionospheric outflow. On the pre‐midnight sector, a larger O⁺outflow was observed during the main phase of sawtooth storms, while non‐sawtooth storms exhibited stronger O⁺outflow during the recovery phase. On the dayside, the peak outflow shifts significantly toward dawn during sawtooth storms. This strong dawnside sector outflow during sawtooth storms warrants consideration. 

Abstract This study presents observations of magnetopause reconnection and erosion at geosynchronous orbit, utilizing in situ satellite measurements and remote sensing ground‐based instruments. During the main phase of a geomagnetic storm, Geostationary Operational Environmental Satellites (GOES) 15 was on the dawnside of the dayside magnetopause (10.6 MLT) and observed significant magnetopause erosion, while GOES 13, observing duskside (14.6 MLT), remained within the magnetosphere. Combined observations from the THEMIS satellites and Super Dual Auroral Radar Network radars verified that magnetopause erosion was primarily caused by reconnection. While various factors may contribute to asymmetric erosion, the observations suggest that the weak reconnection rate on the duskside can play a role in the formation of asymmetric magnetopause shape. This discrepancy in reconnection rate is associated with the presence of cold dense plasma on the duskside of the magnetosphere, which limits the reconnection rate by mass loading, resulting in more efficient magnetopause erosion on the dawnside. 

Abstract Reconnection at Earth's magnetopause drives magnetospheric convection and provides mass and energy input into the magnetosphere/ionosphere system thereby driving the coupling between solar wind and terrestrial magnetosphere. Despite its importance, the factors governing the location of dayside magnetopause reconnection are not well understood. Though a few models can predict X‐line locations reasonably well, the underlying physics is still unresolved. In this study we present results from a comparative analysis of 274 magnetic reconnection events as observed by the Magnetospheric Multiscale (MMS) mission to determine what quantities affect the accuracy of such models and are most strongly associated with the occurrence of dayside magnetopause reconnection. We also attempt to determine under what upstream solar wind conditions each global X‐line model becomes least reliable.