Interchange Reconnection at Small IMF Clock Angles, as Identified by PolarDARN/SuperDARN

When the interplanetary magnetic field (IMF) clock angle θ c = atan2(BY, BZ) lies in the range of 0° < |θ c| < 30°, there only persist IMF-lobe and lobe-closed reconnection (both of which we call interchange-type), with Dungey-type reconnection (IMF-closed and lobe-lobe) being absent. In the ionosphere, the coupling of IMF-lobe and lobe-closed reconnection (which we call the interchange cycle) produces a lobe cell, an interchange-type merging cell, and a reciprocal cell. The reciprocal cell circulates exclusively in the closed field line region and can be used uniquely as an identifier of the interchange cycle. The recent deployment of the PolarDARN radar pair as part of SuperDARN has made it possible to measure all three types of cells in the two-dimensional convection pattern at high latitudes with detail not available previously. In this paper we demonstrate two examples of reciprocal cell observation by PolarDARN (one for IMF BY > 0 and the other for BY < 0). Concurrent precipitating particle data from polar-orbiting satellites are also used to locate the open-closed field line boundary.