This sketch is the result of a computer simulation that shows the geometry of a portion of Earth's magnetic field on 8 May 2004. The simulation confirmed the presence of the magnetic reconnection region observed by the Cluster and Double Star TC-1 satellites on that date.
The five spacecraft found that the reconnection site was located on the daylight west side of the Earth's magnetic shield and was around 25000 kilometres across. Magnetic reconnection is the mechanism responsible for the occurrence of 'flux transfer events' - magnetic channels created by the merging of the Sun and the Earth's magnetic fields through which solar particles can break through the Earth's magnetic shield and penetrate the Earth's environment.