Planetary magnetospheres across the Solar System offer an exceptional opportunity to study universal plasma processes operating under fundamentally different magnetic, atmospheric, rotational and solar-wind conditions. Comparative investigations allow us to distinguish physical mechanisms that are common across planetary environments from those that are unique to individual systems, thereby advancing both fundamental plasma physics and planetary space weather.

Recent and ongoing missions, including BepiColombo, JUICE, Juno, Cassini, Arase, Cluster, MMS, THEMIS, Van Allen Probes, SMILE and complementary ground-based observations, together with advances in first-principles modelling, global simulations, data assimilation, machine learning and artificial intelligence are enabling a new era of comparative magnetospheric science.

We welcome observational, theoretical and modelling studies of planetary magnetospheres, including but not limited to:
• Particle acceleration, transport and loss
• Wave–particle interactions and plasma waves
• Radiation belts and energetic particle populations
• Magnetic reconnection and global plasma circulation
• Magnetosphere–ionosphere–atmosphere coupling
• Auroral processes and energetic particle precipitation
• Solar-wind-driven and internally driven magnetospheric dynamics
• Comparative studies of Mercury, Earth, Jupiter, Saturn, Uranus, Neptune, Mars, Venus and exoplanetary environments
• Numerical modelling, data assimilation, digital twins and machine learning
• Multi-mission analyses and future planetary exploration missions
We especially encourage contributions that bridge planetary science and solar-terrestrial physics, compare multiple planetary environments, or combine observations, theory and advanced data-driven methods. The session aims to strengthen interactions between the PS and ST communities, identify universal plasma processes across planetary magnetospheres, and stimulate new international collaborations and future mission concepts.