Mass loss of N 2 molecules from Triton by magnetospheric plasma interaction

Abstract

Previous investigations of sputtering of molecular nitrogen from Triton's atmosphere lead to estimates of escape rates of about 10 21 N 2 molecules s −1. Here, the erosion of Triton's nitrogen atmosphere resulting from sputtering due to different plasma populations and particles from Neptune's magnetosphere is investigated. This investigation shows that sputtering from Triton's nitrogen atmosphere could lead to N 2 escape rates during the plasma sheet crossing on the order of 5 × 10 24 s −1. This calculation shows that sputtering of Triton's nitrogen atmosphere by magnetospheric particles is an efficient nonthermal escape mechanism, similar to Saturn's large satellite Titan, and is an additional important process for the power input of the Neptune aurora. The N 2 escape rates should be in a good agreement with the measured H +/N + ion ratio in Neptune's 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 N 2 corona on Triton.