The first five vibrationally excited states of molecular nitrogen have
been included in the Sheffield University plasmasphere ionosphere mod
el. Vibrationally excited molecular nitrogen reacts much more strongly
with atomic oxygen ions than ground-state nitrogen, this means that m
ore O+ ions are converted to NO+ ions, which in turn combine with the
electrons to give reduced electron densities. Model calculations have
been carried out to investigate the effect of including vibrationally
excited molecular nitrogen on the low-latitude ionosphere. In contrast
to mid-latitudes, a reduction in electron density is seen in all seas
ons during solar maximum. the greatest effect being at the location of
the equatorial trough.