Nitrogen Emissions from Titan due to Energetic Electron Bombardment

Emissions from Titan’s dayside atmosphere at ultraviolet wavelengths were observed by Voyager. The major source was shown to be photoelectron interactions with the neutral N2 present in the atmosphere whether or not Titan was inside or outside Saturn’s magnetosphere. Since discrepancies exist between observations and models, and photoelectrons do not contribute significantly to emissions from the night side, we use a Monte Carlo model to calculate the emission brightness due to the precipitation of energetic magnetospheric electrons. Titan is assumed to be inside the magnetosphere of Saturn, so that direct coupling of the magnetosphere with the atmosphere is possible. Using extrapolated electron fluxes based on Voyager measurements, the source rates are much smaller than the photoelectron source rates. Since the plasma flow onto Titan’s exobase is highly variable and spatially non-uniform, we give night side emission intensities in a form that can be scaled to the expected Cassini electron flux measurements close to Titan.