Co-ordinated efforts by China/ESA's Double Star and ESA's Cluster spacecraft have allowed scientists to zero in on an area where energetic particles from the Sun are blasting their way through the Earth's magnetic shield. Solar material penetrating the Earth's magnetic shield can represent a hazard to both astronauts and satellites.
On 8 May 2004, one of the two Double Star satellites (TC-1) and all four Cluster spacecraft found themselves in the firing line. For about 6 hours, the Cluster spacecraft were buffeted every 8 minutes by intense flows of electrically charged particles released by the Sun. The Double Star TC-1 spacecraft had it even rougher, being blasted every four minutes for eight hours. During such events, magnetic channels created by the merging of the Sun and the Earth's magnetic fields allow solar particles to break through the Earth's magnetic shield and penetrate the Earth's environment. Physicists call the occurrence of these magnetic channels Flux Transfer Events. Each magnetic channel appears like a curve shaped tube that can be anything from 5000 to 25000 kilometres in diameter. One end of the magnetic flux tube is connected to Earth while the other end is connected to the solar wind.
The basic physical mechanism responsible for the occurrence of flux transfer events is called magnetic reconnection. In the 1950s, space physicists believed that magnetic reconnection let solar particles break through at a steady rate. That view changed in the late 1970s, when several studies showed that the magnetic reconnection could also be intermittent and take place in pulses, lasting a few minutes. Each pulse produces a magnetic flux tube (a Flux Transfer Event).
On 8 May 2004, these magnetic flux tubes swept over Cluster and Double Star again and again. As the Cluster and Double Star data clearly showed, the same location underwent magnetic reconnection several times, creating new successive magnetic flux tubes to ch
Contact: Philippe Escoubet
European Space Agency