Highly correlated ion upflow and electron temperature variations in the high latitude topside ionosphere

We investigate the nature of ambipolar electric field driven ion upflow in the northern high-latitude \textit{F} region ionosphere. Measurements from the Langmuir probes and thermal ion imagers on two Swarm satellites covering the year 2016 reveal highly correlated relative electron temperature variations, Δ T_e, and relative ion vertical velocity variations, Δ V_i. Statistical analysis of separately identified electron temperature and ion upflow variations at spatial scales spanning { ∼}4 {km} to { ∼}152 {km} reveal Pearson R correlations as high as 0.99. Correlations are lower but still significant for the subset of events within the approximate cusp/cleft region. Roughly 60% of all temperature enhancements have an associated upflow. At an altitude of 460 km, the upflows are within { ∼}15 to { ∼}30 {km} of the temperature enhancements along the satellite track. At 510 km, the separation is { ∼}8 to { ∼}15 {km}. For temperature enhancements less than { ∼}2000 {K}, the upflows have the form Δ V_i=aΔ T_e+b with a=0.10 - 0.31 {m}{s}^{-1} {K}{-1} with correlation values of ρ =0.60 - 0.99. Relative upflows begin to saturate at larger temperature enhancements. Under suitable assumptions, the coefficient a may be related to the ion-neutral momentum transfer collision frequency, opening a new window on thermosphere-ionosphere coupling physics in the topside ionosphere.