Modeling the Solar Cycle Dependence of Quiet-time Ion Upwelling at High Geomagnetic Latitudes

In this letter, we summarize initial results showing how solar cycle variations of the thermosphere modify the composition and intensity of ion upflows at high geomagnetic latitudes. Using an improved version of the one-dimensional hydrodynamic polar wind model developed by Gombosi et al. (1985), we obtain H + and O + vertical flow profiles using different thermospheric states corresponding to solar cycle minimum and maximum. In comparing the quasi-equilibrium flux profiles for both cases, we find that H + upwelling shows almost no variations in intensity with solar cycle while O + exhibits a 10-fold increase from solar minimum to solar maximum. These changes result in an O+-dominated upflow at solar maximum while H + flows dominate at solar minimum. We relate these different behaviors to long-term thermospheric hanges resulting from solar cycle EUV/UV differences and compare our results with observations.