Jm. Grebowsky et al., HIGH-LATITUDE FIELD-ALIGNED LIGHT-ION FLOWS IN THE TOPSIDE IONOSPHEREDEDUCED FROM ION COMPOSITION AND PLASMA TEMPERATURES, Journal of atmospheric and terrestrial physics, 55(11-12), 1993, pp. 1605-1617
Under the assumption of steady state conditions, the continuity and mo
mentum equations can be solved locally for magnetic field aligned ion
flow velocities given the local ion concentrations, electron and ion t
emperatures and their vertical gradients, as well as the neutral compo
sition derived from the MSIS model. Using a comprehensive ionospheric
data set comprised of all available ion composition and plasma tempera
ture measurements from satellites, the vertical distributions of ion c
omposition and plasma temperatures are defined from middle latitudes u
p into the polar cap for summer conditions for altitudes below approxi
mately 1200 km. These data are sufficient to allow a numerical estimat
ion of the latitudinal variation of the light ion outflows from within
the plasmasphere to the polar wind regions. The altitude at which sig
nificant light ion outflow begins is found to be lower during solar mi
nimum conditions than during solar maximum. The H+ outward speeds are
of the order of 1 km/s near 1100 km (the limit of the observations) du
ring solar maximum but attain several km/s speeds for solar minimum. H
e+ shows a similar altitude development of flow but attains polar cap
speeds much less than 1 km/s at altitudes below 1100 km, particularly
under solar maximum conditions. Outward flows are also found in the to
pside F-region for noontime magnetic flux tubes within the plasmaspher
e.