Multi-scale observations of magnetotail flux transport during IMF-northward non-substorm intervals

Abstract. Simultaneous observations by the Cluster spacecraft and SuperDARN radars are presented of magnetotail flux transport during northward, but B_Y-dominated IMF. Two events are discussed, which occurred on 14 August 2004 and 17 September 2005, during intervals of negative and positive IMF B_Y, respectively. During both intervals the Cluster spacecraft observed isolated bursts of Earthward plasma convection in the central plasma sheet. During the first event, the flows observed by Cluster also had a significant V_⊥Y component in the duskward direction, consistent with westward azimuthal flows observed in the midnight sector by the Northern Hemisphere SuperDARN radars. During the second event, Cluster 4 observed a significant dawnward V_⊥Y component, again consistent with the Northern Hemisphere SuperDARN observations which revealed eastward azimuthal flow. In this instance, however, Cluster 3 observed a duskward V_⊥Y component which was more consistent with the duskward sense of the convection observed by the Southern Hemisphere SuperDARN radars. This implies that Cluster 3 and Cluster 4 were located on different field lines which experienced opposite net azimuthal forces and hence observed oppositely directed convection. These observations are consistent with previous SuperDARN studies of nightside flows under northward IMF and, more importantly, provide the first simultaneous in-situ evidence for a mode of tail reconnection occurring during non-substorm intervals in an asymmetric tail.