Impact of the precipitation of magnetospheric electrons on the composition of Triton's atmosphere

The magnetic environment of Triton is highly variable due to the combination of its inclined orbit and of the complex geometry of Neptune’s magnetic field. Thus, the electron precipitation in Triton’s atmosphere varies strongly. As this precipitation is supposed to have an important effect on the atmosphere, a better understanding of the interaction between magnetospheric electrons and the atmosphere is necessary.

In this work, we coupled a 1D photochemical model of Triton’s atmosphere with the electron transport code TRANSPlanets. The latter code is used to compute the rates of the electron-impact ionization and dissociation reactions depending on the electron precipitation, the orbital scaling factor and the magnetic field strength. These rates are then used in the photochemical model to compute the atmospheric composition. We did these computations for various initial conditions to find the ones allowing to better match Voyager 2 observations. We found that, contrary to previous models, the main ionization source in the atmosphere is photoionization instead of electron-impact ionization.