PolarDARN Radar Observations of Plasma Flows Associated with Morning Polar Cap Forms Detaching from the Auroral Oval

OMTI all-sky camera at Resolute Bay (Canada) often detects optical forms detaching from the poleward edge of the dawnside auroral oval and moving toward dusk. Such forms typically consist of rayed arc-like fragments stretched toward the Sun. The two newly installed PolarDARN-SuperDARN HF radars at Rankin Inlet and Inuvik sometimes detect signatures of such forms. In this study, several events of joint radar-optical observations are presented to investigate features in the plasma flow patterns. We show that the forms typically occur within a band of anti-sunward flow. Strong sunward flow channels are sometimes seen between the form and auroral oval so that strong flow shears are formed. The data can be interpreted in terms of a mesoscale vortex embedded into a large-scale morning side convection cell. Other features are discussed.