The solar wind drives multiscale, cross-region, and cross-energy interactions within Earth’s magnetosphere–ionosphere system, shaping the dynamics of geospace. This session focuses on understanding these interactions through observations and modeling approaches. At the global scale, we aim to explore how geomagnetic storms and substorms respond to solar wind drivers. At regional and mesoscale levels, we welcome studies on plasma convection, magnetosphere–ionosphere current systems, magnetic reconnection, boundary layer instabilities (e.g., Kelvin–Helmholtz), flux transfer events, ULF waves, ionospheric convection, auroral arcs, and related phenomena. Emphasis is placed on linking these processes to specific solar wind conditions and elucidating their roles in system-level responses. We invite contributions that integrate data from space missions (e.g., THEMIS, Cluster, MMS, RBSP), ground-based observatories (e.g., SuperDARN, magnetometers, optical networks), and numerical or machine learning models. This session supports the upcoming SMILE mission by promoting studies aligned with its science goals on solar wind–magnetosphere–ionosphere coupling.