The space environments of planets are full of energetic charged particles that are found in the radiation belts and the auroral region connecting to the magnetosphere. No single planet can be considered as a prototype for all others. Energetic charged particles are affected by electromagnetic fields, waves, plasma, and neutral material from atmospheres, rings, and moons. Each planet weighs these processes differently, a fact that can be leveraged by comparative studies to develop a universal understanding of space physics. Planetary comparisons are timely because recent spacecraft missions provide a wealth of measurements at Earth, Jupiter, and Saturn, and the exploration of Uranus and Neptune is under way. This session invites presentations on fundamental energetic charged particle processes in the radiation belts and as part of magnetosphere-ionosphere coupling. Results from any magnetized planet within our solar system or extrasolar systems may be based on theory, simulations, spacecraft or Earth-based observations.