The Radiation Belts of Jupiter and Saturn

The era of outer planet orbiters (Galileo, Juno and Cassini) is advancing our understanding how the radiation belts Jupiter Saturn are structured, form evolve well beyond what had been possible during age flyby missions ground-based observations. nearly two decades-long datasets these missions, in context detailed long-term observations Earth's belts, highlight which processes that accelerate particles to relativistic kinetic energies limit their flux intensity can be considered more universal, thus key for most extraterrestrial magnetospheres, reflect unique aspects each its magnetospheric system. In this chapter we focus on in-situ belt theory, simulations relevant measurements by Earth-based observatories. We describe both average state time variations Jupiter's Saturn's associate them with specific physical processes.