Simultaneous measurement of ion and neutral motions by radar and optical techniques

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Abstract
The results of simultaneous thermospheric neutral wind and ionization drift measurements from near College, Alaska (L = 5.6, Λ = 65°) are presented. The neutral wind data were obtained by observing the Doppler shift of the 6300 Å atomic oxygen line with the 15‐cm Fabry‐Perot interferometer of the Michigan Airglow Observatory which is located temporarily at Ester Dome, Alaska. Ionization drifts were measured by the Chatanika incoherent scatter radar facility. These simultaneous measurements indicate that in the premidnight sector both the neutral wind and the ionization drift are generally westward. This westward ionization drift is consistent with the general magnetospheric convection pattern but the measured neutral wind is in a direction opposite to the diurnal pressure gradients and thus must be driven by ion drag. In the postmidnight sector the ionization drift turns eastward while the neutral wind direction turns south. Again, the ion drift is consistent with previously published results; the reasons for the absence of significant zonal neutral winds and the significant southward meridional wind in the postmidnight sector are not well understood at this time, but are probably a combination of a decrease in the ion drag force following magnetic midnight, Coriolis force, and pressure gradients due to both the diurnal and auroral heat sources.

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