The excitation of convection in the cusp region as observed by the SuperDARN radars

Abstract

Abstract SuperDARN observations from the interval 1330 UT to 1500 UT, 17 April 1996, are presented. During this interval, five radars covered 12 hours of magnetic local time on the dayside, including the cusp region, in the Northern hemisphere, and one observed the cusp region in the Southern hemisphere. In response to a southward turning of the interplanetary magnetic field, backscatter appears in all radar fields-of-view, first in the cusp region and then in the dawn and dusk sectors after a delay consistent with an anti-sunward propagation speed of 1.5 km s−1. In the Northern hemisphere cusp region, antisunward plasma drift and poleward-moving forms are observed with a 10 min periodicity, which is typically the radar signature of flux transfer events. Such signatures of transient reconnection are not seen in the Southern hemisphere cusp region, where predominantly azimuthal plasma drift is observed. In the dawn and dusk sectors, the radars observe sunward plasma drift in the convection return flow region, and transient, sunward-moving backscatter features which have a periodicity of approximately 10 mins.