Magnetic fields are windows into planetary interiors. The existence and properties of the planetary magnetic fields reflect the interior structure, dynamics, and evolution of the host planets. The solar system offered a very diverse group of planetary magnetic fields: Earth’s magnetic field is dipole-dominant with significant deviations near the equator and at high latitudes when viewed at the core-mantle boundary, Mercury’s surface magnetic field strength is only ~1% of the Earth’s and is strongly north-south asymmetric, Mars’ crustal magnetic field is strongly north-south asymmetric, Jupiter’s dipole-dominant magnetic field features a strong equatorial magnetic spot and a tilted magnetic flux band in the northern hemisphere, Saturn’s magnetic field is extremely axisymmetric, while the magnetic fields of Uranus and Neptune are strongly non-dipolar and non-axisymmetric. The diversity in planetary magnetic fields likely originate from structural and dynamical differences in the host planets, such as the existence of deep stable stratification and different characteristics of deep flows. In this lecture, after an overview of planetary magnetism and dynamo theory, I will discuss two topics in more detail: 1) Jupiter and Saturn in the Era of Juno and Cassini; 2) are Mercury and Ganymede magnetic twins? In closing, I will highlight the magnetic aspects of a few upcoming planetary missions and how they will help answer questions ranging from the thermal evolution history of asteroids to the properties of Ganymede’s subsurface ocean.
