ESA's mission Cluster consists of four identical spacecraft flying in formation between 19 000 and 119 000 km above the Earth. They study the interaction between the solar wind and Earth’s magnetosphere, or the Sun-Earth connection in 3D.


 
Magnetic reconnection plays a key role in various astrophysical phenomena. It is related to star formation, solar explosions and the entry of solar wind energy into the near-Earth environment.

During the process, magnetic field lines from different magnetic domains collide and reconnect, mixing previously separated plasma. Plasma is a gas composed of ions and electrons but is electrically neutral, spread over large distances in space and guided by the action of magnetic and electric fields.

Magnetic reconnection converts the energy of the magnetic field into particle energy, generating jets and heating the plasma.

This affects us here on Earth because it can possibly affect telecom satellites and prevent the efficient production of electricity in controlled fusion reactors. On Earth, we can also see the effect in intense displays of the Northern lights.


 
During reconnection inside a plasma, the geometry of the magnetic field forms an X-shape, also called a ‘magnetic null’. Magnetic field lines of different polarities break and then reconnect, forming the X-line magnetic topology.


 
A diagram illustrating the null-null line observed by Cluster’s four spacecraft in the Earth’s magnetotail on 1 October 2001.



Release date: 29 June 2007