Data taken over midatitudes by Dynamic Explorer 2 during a geomagnetic storm are used to demonstrate that a direct correlation exists between depletion in the ratio [0>/[N2> and in the topside electron density (Ne). That correlation is most conspicuous along 45¿ invariant latitude where a decrease in [0>/[N2> by a factor of 5 is associated with a depletion in Ne by a factor of 8. Data comparisons were made by using densities of molecular nitrogen and atomic oxygen measured by the neutral atmosphere composition spectrometer, gas temperatures measured by the wind and temperature spectrometer, and temperatures and densities of thermal electrons measured by the Langmuir probe. The measurements were taken in the sunlit northern hemisphere during September 21--23, 1982, in the altitude range 300--500 km. During the storm gas temperatures were elevated, while the ratio [0>/[N2> and Ne were reduced. At 60¿ and 45¿ invariant latitudes, the most significant disturbances in the ratio [0>/[N22> and Ne were depletions; but at 20¿ invariant latitude depletions in the ratio [0>/[N2> and Ne indicate that, for this storm, ion chemistry controls the observed variations of topside Ne at the higher latitudes. However, the development at 20¿ invariant latitude of elevated gas temperatures and an enhancement in Ne indicates that a storm induced equatorward wind component transported plasma toward lower latitudes at a rate that initially exceeded the rate of ionization losses there.