An investigation of the coupling between the ionosphere and the thermo
sphere is made using coordinated measurements obtained simultaneously
with the Chatanika incoherent-scatter radar and two Fabry-Perot spectr
ometers at College, Alaska, during a 2 hr period in February 1982. One
of the Fabry-Perot spectrometers measured the line shape of the oxyge
n 630.0-nm emission, and the other measured the line shape of the oxyg
en 557.7 nm emission. The measurements were used to obtain the neutral
and ion velocities, the neutral, ion, and electron temperatures; and
the electron densities in the E and F regions. Interpreting these meas
urements using the ion energy equation for the F region yields the hei
ght(s) at which heat exchange between the ions and neutrals balances t
he sum of frictional heating due to differences in the ion and neutral
velocities and heat exchange between the electrons and ions. This hei
ght can be interpreted as the location of the oxygen 630.0-nm emission
profile centroid, thus providing an estimate of the height of the neu
tral temperature measurement. Furthermore, the centroid location and e
xtent in altitude depend on the processes producing O(1D) in aurorae.
A unique balance height was not typically found, but balance often occ
urred over a wide range of altitudes, depending on the assumption of a
pure O+ or a pure NO+ ionosphere, which is consistent with model calc
ulations of the 630.0-nm emission rate profile. Though the coordinated
optical-radar measurements available are limited, the initial results
demonstrate that important questions relating to ion and neutral comp
osition, chemistry, and dynamics can be examined by the methodology em
ployed in this study.