Titans ionosphere : a review

This paper presents a concise review of our present understanding of the ionosphere of Titan and its interaction with the surrounding magnetosphere⧹ magnetosheath of Saturn, based on observational constraints and theoretical model calculations. A variety of different models, as well as the Voyager 1 radio occultation re-analysis, indicate a peak electron density of about 2.5–3.0×103 cm−3, at an altitude just below 1200 km, for a solar zenith angle of near 90°. Calculations predict that the ions near the electron density peak consist mainly of HCNH+ and other more complex hydrocarbon ions. The lack of observational constraints on the electron and ion temperatures leads to a wide range of possible values from the models, ranging from less than 1000 to nearly 10,000°K. The Voyager 1 plasma measurements in Titans wake, combined with model calculations, have been used to estimate that the outward fluxes from the tail are on the order of 2–7×106 cm−2 s−1, corresponding to a total ion loss rate on the order of 1025 s−1.