Mass loss of N2 molecules from Triton by magnetospheric plasma interaction

Previous investigations of sputtering of molecular nitrogen from Tritonʹs atmosphere lead to estimates of escape rates of about 1021 N2 molecules s−1. Here, the erosion of Tritonʹs nitrogen atmosphere resulting from sputtering due to different plasma populations and particles from Neptuneʹs magnetosphere is investigated. This investigation shows that sputtering from Tritonʹs nitrogen atmosphere could lead to N2 escape rates during the plasma sheet crossing on the order of 5 × 1024 s−1. This calculation shows that sputtering of Tritonʹs nitrogen atmosphere by magnetospheric particles is an efficient nonthermal escape mechanism, similar to Saturnʹs large satellite Titan, and is an additional important process for the power input of the Neptune aurora. The N2 escape rates should be in a good agreement with the measured H+/N+ ion ratio in Neptuneʹs magnetosphere. The excess energy of the sputtered particles leads primarily to escape and supply to the Neptune system rather than to ballistic orbits. Sputtering will yield, however, a small N2 corona on Triton.