Comparative Auroral Physics: Earth and Other Planets

Here we review selected similarities and differences between the structures and processes associated with the generation of the aurora of strongly magnetized planets within the solar system. Our ultimate objective is to use a comparative approach to determine which aspects of auroral phenomena represent universal features and which aspects are particular to the special conditions that prevail at any one planet. We begin by providing a high-level review of selected fundamental auroral processes operating at Earth as a precursor to discussing selected similar processes and regions at other planets. We then discuss the broad characteristics of the space environments of different planets (Earth, Jupiter, Saturn, Uranus, and Neptune) with an eye toward determining the factors that dictate similarities and differences between the respective auroral systems. With a focus on discrete auroral processes, we finally discuss comparisons between the different systems on the basis of (1) magnetospheric current systems, (2) mechanisms of current closure within the distant regions of the magnetospheres, (3) particle acceleration, (4) ionospheric feedback, and (5) satellite systems.