Earth's inner magnetosphere contains diverse charged-particle populations, including the Van Allen radiation belts, ring current, and plasmasphere, spanning energies from eV to several MeV. These populations are dynamically coupled through various processes that produce feedback across different plasma regimes. Ring current particles can generate waves, including EMIC and chorus waves, which in turn influence radiation belt dynamics through wave-particle interactions. Ring current electrons can be accelerated to relativistic energies and contribute to the radiation belts, while the plasmaspheric environment can regulate wave generation, propagation, and particle scattering. Coupling also extends beyond the inner magnetosphere. Precipitation of ring current and radiation belt particles modifies the ionosphere and upper atmosphere, while ionospheric outflows can influence magnetospheric plasma populations and dynamics. Understanding such interactions is essential both for advancing fundamental knowledge of magnetospheric dynamics and for improving space weather specification and forecasting. Beyond Earth, the magnetospheres of the outer planets are driven by different combinations of internal and external processes, yet they exhibit many analogous forms of plasma transport, acceleration, loss, and coupling. Comparative studies therefore provide valuable opportunities to identify common physical mechanisms as well as processes unique to individual planetary environments.
We invite theoretical, modelling, and observational studies addressing the dynamics and coupling of Earth's and other planetary inner magnetospheres. Relevant topics include interactions among radiation belt, ring current, and plasmaspheric populations; wave particle interactions; magnetosphere-ionosphere coupling; particle precipitation and ionospheric outflow; responses to solar wind disturbances; and comparative magnetospheric physics. Contributions using numerical simulations, satellite and ground-based observations, data assimilation approaches, and new mission concepts are welcome. We particularly encourage studies using observations from missions and facilities such as MMS, THEMIS, Van Allen Probes, Arase (ERG), Cluster, CubeSats, Juno, SuperDARN, magnetometers, optical imagers, incoherent-scatter radars, and ground-based VLF measurements.