Cluster C3 and C1 satellite trajectories
A schematic view of the Cluster C3 and C1 satellite trajectories between 16:55 and 17:15 UT on 5 June 2009. During this period, both satellites collected data from the auroral acceleration region (AAR) of Earth's dusk-side aurora. C3 flew through the AAR at an altitude of about 6400 km (one Earth radius or RE), while C1 was flying at approximately 9000 km (1.4 RE) and lagging about 5 minutes behind. The blue ovals indicate the poleward half of the auroral oval, which is characterised by upward currents flowing along in the dusk-side magnetic field.