Planetary magnetic fields are a window to a planet’s interior and provide shielding of the planet’s atmosphere and surface for life. The Earth, Mercury, Ganymede, and the giant planets of the solar system all contain internal dynamo currents that generate planetary-scale magnetic fields. In turn, these internal dynamo currents arise from differential rotation, convection, compositional dynamics, or a combination of these in a planet's interior. Extrapolated to extrasolar planets, knowledge of a planet’s magnetic field places constraints on the thermal state, composition, and dynamics of its interior—all of which will be difficult to determine by other means. The magnetic field also provides crucial information about the extent to which the surface of a terrestrial planet is shielded from cosmic rays and its potential to be habitable.
The focus of this second workshop will be to assess the current status of developing ground-based instruments, determine what proposals can or have been written for existing telescopes, and synthesize the results of study teams since the first workshop. From the results of the study teams, we will determine the structure of the set of review papers to be produced from the study, determine what is the proper scope for future missions (magnetic fields of gas giants vs. ice giants vs. terrestrial planets), and identify technology development that is likely to be needed for any such future missions and not already being conducted.