Evolution of Mesoscale Dayside Cusp Convection

The cusp in the ionosphere is a region with enhanced flows and precipitation due to solar wind-magnetosphere interaction. The enhanced flows indicate enhanced magnetopause reconnection and are important for plasma transport from the subauroral ionosphere to the polar cap. However, it is often difficult to determine the 2-D cusp flow structure due to limited data coverage. To address this issue, we use the Super Dual Auroral Radar Network (SuperDARN) radar network when the echoes cover much of the dayside high-latitude ionosphere. The Spherical Elementary Current Systems (SECS) technique is applied to reconstruct the convection pattern at both large and meso scales. We found that the cusp poleward flows are enhanced in a localized region and then expand zonally and meridionally when the IMF turns southward. Even when the IMF Bz is steadily negative, the cusp flows are suddenly enhanced and move poleward analogous to poleward moving auroral form (PMAF). They may be related to small variations in the IMF By. The poleward flows are not always a single flow channel but can have multiple channels, indicating multiple magnetopause reconnections. Our work shows the dynamic variability of cusp flows and the capability to show their 2-D structure.