The Magnetodisk Regions of Jupiter and Saturn

The rapidly rotating magnetospheres of the gas giant planets, Jupiter and Saturn, are natural laboratories for learning about magnetized plasmas. Several spacecraft missions have provided a wealth of observations that confirm the central role of the “magnetodisk” structure in these systems. This region consists of a magnetic field generated by an extended current sheet, and the associated plasma disk. Magnetodisks continually change in response to various mechanisms – including the rotating, tilted dipole of the parent planet; the magnetopause currents; and, for Saturn in particular, rotating systems of current that communicate energy between the planet's atmosphere and the disk. In this review, we provide a summary of some of the mechanisms that determine magnetodisk structure and dynamics at both Jupiter and Saturn, and their observational signatures. We then discuss approaches to modeling the magnetic fields and currents in the middle magnetosphere regions. We discuss the influence of the magnetodisk on magnetospheric compressibility, and investigate the roles of planetary rotation and energetic particles in determining plasmadisk structure