MASS-LOSS OF N-2 MOLECULES FROM TRITON BY MAGNETOSPHERIC PLASMA INTERACTION

Previous investigations of sputtering of molecular nitrogen from Trito n's atmosphere lead to estimates of escape rates of about 10(21) N-2 m olecules s(-1). Here, the erosion of Triton's nitrogen atmosphere resu lting from sputtering due to different plasma populations and particle s from Neptune's magnetosphere is investigated. This investigation sho ws that sputtering from Triton's nitrogen atmosphere could lead to N-2 escape rates during the plasma sheet crossing on the order of 5 x 10( 24) s(-1). This calculation shows that sputtering of Triton's nitrogen atmosphere by magnetospheric particles is an efficient nonthermal esc ape mechanism, similar to Saturn's large satellite Titan, and is an ad ditional 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 sp uttered 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.