The amount of open flux in the polar cap is an important parameter characterizing the state of the magnetosphere. This is a one-year project with the main objective to develop and validate techniques based on measurements from the Super Dual Auroral Network (SuperDARN) to provide estimates hereof routinely and with high time resolution. Such measurements would be a great new asset for a variety of studies of magnetospheric dynamics. The proposed techniques will be implemented and tested in a number of in-depth case studies. The case studies are designed to investigate the relation between the amount of open flux and the state of ionospheric convection. These results will provide basic tests of the expanding-contracting polar cap paradigm, which is one of the central paradigms in our current understanding of magnetospheric dynamics.