Electrons in the ionosphere of Titan

A theoretical model of the spatial and energy distribution of electrons in the ionosphere of Titan has been constructed using the two‐stream electron transport method and the electron energy equation. The calculated electron spectra show abrupt decreases that can contribute to the “bite‐out” signature observed by the Voyager 1 plasma science instrument. Energy deposition rates in the exosphere of Titan by photoelectrons and magnetospheric electrons are calculated. Calculated N 2 EUV airglow emission rates lead to the conclusion that airglow emission due to photoelectron impact is much more important than airglow emission due to magnetospheric electron interactions. Thermal electron temperatures at Titan are calculated for the first time. The electron gas remains well thermalized with the neutral atmosphere for radial distances from the center of Titan less than 3500 km. For radial distances beyond about 4000 km, energy transport dominates the energetics, and the electrons are almost isothermal along magnetic field lines.