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First 3D Picture of Magnetic "Dance" Above Earth

Magnetic reconnection events filmed in 3D by ESA's Cluster satellites

Jun 29, 2007 13:52 GMT  ·  By
The four Cluster satellites, at the boundary between the magnetosphere (blue) and the solar wind (yellow)
   The four Cluster satellites, at the boundary between the magnetosphere (blue) and the solar wind (yellow)

For the first time, scientists from the European Space Agency obtained tri-dimensional pictures of a spectacular magnetic "dance" above the Earth, caused by a phenomenon known as "magnetic reconnection."

The Cluster mission is a European Space Agency (ESA) unmanned space mission to study the Earth's magnetosphere using four identical spacecraft flying in a tetrahedral formation. Using a pioneering technique, they were able to get a new picture of these events that would hopefully help scientists understand better the complex processes that lead to this reconnection in near-Earth space.

The Earth's magnetic field is our first line of defense against the incessant flow of solar particles, and most of this material is being deflected around the Earth's magnetosphere. As particles coming from the Sun collide with the magnetic field, they're rapidly slowed, causing a barrier of electrified gas, called the bow shock, to build up, much like water is pushed to the sides by the nose of a boat.

Magnetic field lines from various domains collide and reconnect, mixing plasma that was previously separated, which then converts the energy of the magnetic field itself into particle energy that generates jets of superhot plasma.

Observing reconnection at small-scale boundaries in space requires some precise simultaneous measurements that can only be done by at least four spacecraft flying in close formation. With an inter-spacecraft distance of only 100 kilometers, the four Cluster satellites were able to observe reconnection within a very thin current "sheet" embedded in the turbulent plasma with a typical size of about 100 kilometers.

Using the new 3D technique, made possible by the arrangement of the four satellites, scientists determined that there are actually two interlinked events that occur simultaneously during the reconnection.

The new results finally prove what had been only theorized, the production of two magnetically linked reconnection sites, a pair of magnetic nulls and magnetically linked reconnection geometry.