The Voyager 2 encounter with Neptune and Triton in August 1989 showed
a large ionosphere at Triton. Subsequent studies have tried to explain
the production of such high levels of ionization but have ignored the
possible plasma dynamics originating from the interaction between Nep
tune's magnetosphere and Triton. This study applies knowledge gained f
rom studying the solar wind-Venus interaction to this case. We find th
at observations made by Voyager 2 can be explained bg downward convect
ion of magnetospheric plasma into Triton's atmosphere, with the flow m
omentum transferred to the neutral atmosphere near an altitude of 650
km. We show that momentum transfer is accomplished as both the convect
ive velocity and the magnetic field go to zero. The mechanism by which
the ionosphere is produced was identified previously as impact ioniza
tion from hot electrons originating in Neptune's magnetosphere. These
precipitating hot electrons are shown in this study to be unaffected b
y a magnetic field below roughly 650 km. This is a result not previous
ly anticipated, and one which implies that the plasma interaction betw
een Neptune's magnetosphere and Triton cannot be ignored.