| In the terrestrial atmosphere, above the ion density peak, the high mobility of the plasma along the magnetic field allows field-aligned gravitational forces, collisional forces, and pressure gradients to easily create field-aligned ion drifts. Thus, variations in the field-aligned ion drifts can be used to explore the influence of thermospheric, electrodynamic, and chemical processes on the topside ionosphere. Equatorial variations in the field-aligned ion drifts are presented using observations from the Coupled Ion Neutral Dynamics Investigation (CINDI) onboard the Communications/Navigation Outage Forecast System (C/NOFS) satellite. These observations were obtained during the period of extremely low solar activity present between the 23 rd and 24th solar cycles. This allowed the seasonal, local time, longitudinal, and latitudinal variations in the field-aligned drift to be used alongside complimentary datasets to reveal the relative importance of the transport processes responsible for topside field-aligned plasma drifts during solar minimum.;Comparing the field-aligned ion drift observations with the complimentary datasets, made it possible to describe the influence of the low altitude winds and tides, net ionization or loss processes, and the meridional Ex B drift. It was found that the low altitude winds and tides contributed at all seasons, local times, and locations, causing recognizable signatures in the field-aligned drift such as summer-to-winter transport during solstices and a 4-peaked longitude structure near the magnetic equator. Net ionization or loss were found to contribute to the fastest field-aligned ion drifts near the solar terminators, and were considered a secondary contributor at other local times. Finally, it was found that when a meridional Ex B drift was present, it played the largest role in shaping the latitude profile of the field-aligned drift and a smaller role in modifying the magnitude of any interhemispheric field-aligned drifts already present. |
