The Triton torus revisited

Prior to the Voyager encounter with Neptune, Delitsky et al. [1989] predicted that a torus of ions emanating from Triton would be discovered. We revisit those predictions in light of the Voyager results. Sputtering of Triton's atmosphere can produce the heavy ion densities inferred at Triton's orbit by the Voyager plasma experiment if the ion residence time is about 30 days. The torus is found to be longitudinally asymmetric near Triton, with peak densities at longitudes of 170° and 350°. The total nitrogen flux due to sputtering is about 2×10²¹ s⁻¹. The consequences of larger escape fluxes of both N₂ and H₂ (suggested by Broadfoot et al. [1989]) are investigated; it is difficult to reconcile large escape fluxes with the plasma and ultraviolet spectrometer observations.