Response of ionospheric convection to sharp southward IMF turnings inferred from magnetometer and radar data

Reconfiguration of the convection pattern associated with a sudden transition in the north/south component of the IMF from stable positive to stable negative values is investigated for two events using both magnetometer and SuperDARN data. The IMF transition impinges upon the magnetosphere near the 10 MLT sector; perturbations are clearly seen on the dayside at the time of onset and on the nightside with a ∼10 min delay from onset. This implies a dayside‐to‐nightside progression of the ionospheric response observed in the magnetic perturbations and SuperDARN velocities, contrary to the globally simultaneous response reported in the literature for a number of other events. The foci of the dawnside convection cells are shown to shift from near midnight toward the dayside, reaching a final location between 06 MLT and 08 MLT within 14–18 min of onset. The location of the duskside convection cell remains in the early afternoon sector both prior to and after the transition for both events. Once the convection foci reach a final location, the overall convection pattern enhances.