It has previously been shown that in the high‐latitude thermosphere, sudden changes in plasma velocity (such as those due to changes in interplanetary magnetic field) are not immediately propagated into the neutral gas via the ion‐drag force. This is due to the neutral particles (O, O2, and N2) constituting the bulk mass of the thermospheric altitude range and thus holding on to residual inertia from a previous level of geomagnetic forcing. This means that consistent forcing (or dragging) from the ionospheric plasma is required, over a period of time, long enough for the neutrals to reach an equilibrium with regard to ion drag. Furthermore, mesoscale variations in the plasma convection morphology, solar pressure gradients, and other forces indicate that the thermosphere‐ionosphere coupling mechanism will also vary in strength across small spatial scales. Using data from the Super Dual Auroral Radar Network and a Scanning Doppler Imager, a geomagnetically active event was identified, which showed plasma flows clearly imparting momentum to the neutrals. A cross‐correlation analysis determined that the average time for the neutral winds to accelerate fully into the direction of ion drag was 75 min, but crucially, this time varied by up to 30 min (between 67 and 97 min) within a 1,000‐km field of view at an altitude of around 250 km. It is clear from this that the mesoscale structure of both the plasma and neutrals has a significant effect on ion‐neutral coupling strength and thus energy transfer in the thermosphere.

Statistical models have been developed for predicting the behavior of the coupled high‐latitude ionosphere‐thermosphere system. The modeled parameters were the F‐layer peak electron density, plasma structuring, ion temperature, neutral temperature, and the difference between these temperatures, which is a key term in the Joule heating equation. Ionospheric measurements from the European Incoherent Scatter Svalbard Radar and neutral atmosphere measurements from the colocated University College London Fabry‐Perot Interferometers have been made across a solar cycle. These data were all acquired during nighttime conditions as the observations with the Fabry‐Perot Interferometers are restricted to such times. Various geophysical proxies were tested to represent the processes that influence the modeled parameters. The dominant geophysical proxy for each modeled parameter was then determined. Multivariate models were also developed showing the combinations of parameters that best explained the observed variability. A comparison with climatology showed that the models give an improvement in every case with skill scores based on the mean square error of up to 0.88.