The nitrogen tori of Titan and Triton

As a result of electron impact dissociation and electron dissociative recombination, nitrogen atoms could be ejected from the exosphere of Titan representing an efficient way of non-thermal atmospheric escape. In this study, the corresponding formation of a nitrogen torus in the magnetospheric system of Saturn is simulated. The number density of the nitrogen atoms in a narrow gas ring near the orbit of Titan is estimated to be on the order of 3-20 atoms cm^-3 while a much more diffuse nitrogen cloud covers the whole Saturnian system. Because of the small kinetic energy of the atomic nitrogen fragments at production, only a very small density can be maintained in most parts of the magnetosphere. The ionization of the nitrogen atoms in this extended gas torus could nevertheless introduce an appreciable amount of N⁺ ions into the Saturnian magnetosphere. A similar extended structure of an atomic nitrogen cloud is produced in the Neptunian system as a result of the nonthermal escape of nitrogen atoms from Triton. The peak density near Triton's orbit is estimated to be 10-20 atoms cm^-3.