Outer planet ionospheres: A review of recent research and a look toward the future

A major focus of recent research on the ionospheres of the outer planets has been on the interpretation of jovian auroral emissions at infrared, ultraviolet, and X-ray wavelengths. Analysis of these emissions has provided valuable clues to the still poorly understood nature of the magnetosphere-ionosphere interaction at Jupiter and has furnished evidence for the occurrence of heavy ion precipitation into Jupiter's equatorial region. A model of Jupiter's low-latitude ionosphere incorporating ion precipitation effects and a neutral thermal structure derived from the in-situ measurements of the Galileo probe has been developed and reproduces reasonably well the ionospheric structure determined from Voyager 1 radio science data. Other recently developed outer planet ionosphere models include a model of hydrocarbon ions in the jovian ionosphere, a one-dimensional time-dependent model of Saturn's ionosphere, and a photochemical model of Neptune's upper atmosphere.