Energetic Nitrogen Ions within the Inner Magnetosphere of Saturn

Titan's interaction with Saturn's magnetosphere will result in the energetic ejection of atomic nitrogen atoms into Saturn's magnetosphere due to dissociation of N₂ by electrons, ions, and UV photons (Strobel and Shemansky, 1982). The ejection of N atoms into Saturn's magnetosphere will form a nitrogen torus around Saturn with mean density of 6 atoms/cm³ with source strength of 6*E²⁶ atoms/sec (Barbosa, 1987). These nitrogen atoms can then be ionized by photoionization, electron impact and charge exchange reactions producing an N⁺ torus of 1-2 keV suprathermal ions centered on Titan's orbital position. It has been reported that the Voyager plasma instrument has detected the presence of a suprathermal ion component within Saturn's outer magnetosphere (Lazarus and McNutt, 1983; Richardson, 1986). The Voyager LECP data also reported the presence of inward diffusing energetic ions from the outer magnetosphere of Saturn which could have an N⁺ contribution. If so, when one conserves the first adiabatic invariant the N⁺ ions will have energies in excess of 100 keV at Dione's L shell and greater than 400 keV at Enceladus' L shell. With energetic N⁺ ions bombarding the icy satellite surfaces chemical reactions can occur at the end of the ions track and produce nitrogen oxides or other nitrogen containing molecules (Delitsky and Lane 2002). These can accumulate over the lifetime of the Saturn system. We will present results of an analysis of the Voyager PLS and LECP data sets to explore this possibility and make a prediction for the Cassini Mission for the possible detection of suprathermal N⁺ ions within Saturn's inner magnetosphere and ionized nitrogen molecules sputtered from satellite surfaces.