A Statistical Dependence of Ion-Neutral Coupling Rates on Geomagnetic Activity in the Nightside Auroral Oval

High latitude ionospheric plasma convection is driven by electromagnetic coupling between the magnetic field and the solar wind, allowing it to respond quickly to changes in IMF. F-region thermospheric winds, however, have a number of drivers, with the main contributors being ion drag and thermal pressure gradients. The efficiency of each of the thermospheric drivers is not well characterized, which results in a wide reported range of neutral wind response times, from tens of minutes to hours. In the current study we investigate ion-neutral coupling efficiency as a function of geomagnetic activity levels by using PFISR and collocated Scanning Doppler Imager data for ion velocity and neutral winds, respectively. Compared with Fabry-Perot Interferometers, SDIs measure winds from tens of looking directions simultaneously and can track wind evolution at a cadence of 1-5 minutes, making it reliable to study fast neutral wind response. Using various methods, including a new weighted windowed time-lagged correlation analysis, ion-neutral coupling rates are calculated and then compared to various geomagnetic indices, which gives a measure of the ion-neutral coupling efficiency as a function of geomagnetic activity. We also discuss the efficiency of the individual drivers of the thermosphere.