In situ measurements of plasma drift velocity and enhanced NO + in the auroral electrojet by the Bennett Spectrometer on AE‐C

Simultaneous measurements of ion composition and plasma drift velocity by the Bennett mass spectrometer on the Atmosphere Explorer‐C satellite reveal a direct correlation between enhancements in NO + concentration and ion drift velocity in the southern auroral oval. Low altitude (137 to 250km) data obtained between 1700 and 2400 hr magnetic local time on October 22, 1974 reveal a region of westward plasma flow at velocities up to 1.3km/s between 62° and 68° invariant latitude, with corresponding NO + enhancements of up to a factor of 20. A narrow region of reverse flow at ∼0.9km/s was also measured. These drift observations are consistent with convective flow patterns derived from electric field measurements, and their correlation with NO + appears to support the suggestion that NO + enhancements would be expected in regions of drift owing to the dependence on ion energy of the reaction O + + N 2 → NO + + N.