www.ann-geophys.net/27/2721/2009/ © Author(s) 2009. This work is distributed under the Creative Commons Attribution 3.0 License.

Abstract. In recent years, a large number of papers have re-ported the response of the cusp to solar wind variations under conditions of northward or southward Interplanetary Mag-netic Field (IMF) Z-component (BZ). These studies have shown the importance of both temporal and spatial factors in determining the extent and morphology of the cusp and the changes in its location, connected to variations in the re-connection geometry. Here we present a comparative study of the cusp, focusing on an interval characterised by a series of rapid reversals in the BZ-dominated IMF, based on obser-vations from space-borne and ground-based instrumentation. During this interval, from 08:00 to 12:00 UT on 12 Febru-ary 2003, the IMF BZ component underwent four reversals, remaining for around 30 min in each orientation. The Clus-ter spacecraft were, at the time, on an outbound trajector