The magnetosheath is a fundamental component of solar wind - magnetosphere coupling as it is the natural interface between interplanetary space, and the inner magnetosphere. Its global and local plasma conditions regulate processes (e.g. Kelvin Helmholtz, magnetic reconnection, kinetic Alfven waves and flux transfer events) that transport mass and momentum across the magnetopause; thus driving magnetospheric dynamics, which eventually impact the ionosphere. In addition to this, the polar cusps are populated by magnetosheath plasma, which are also fundamental to understanding (and modelling) the state of solar wind - magnetosphere coupling. In both regions, many open questions remain, even despite the abundance of in-situ measurements, theoretical modelling efforts, and the increasing sophistication of numerical simulations. In this session, we invite contributions focusing on the dynamics of planetary magnetosheaths/cusps and their boundary layers. We particularly welcome studies focusing on the role of magnetosheath and cusp processes in solar wind - magnetosphere coupling. Contributions related to the newly selected ESA-China SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) mission are encouraged.