‘Magnetic reconnection’ can take place when magnetic fields collide. The field lines connect differently, changing the shape of the magnetic ‘landscape’ and allowing previously separated plasmas to mix. It efficiently accelerates particles and heats the plasma.
However, certain fundamental properties of this phenomenon remain unknown. One key issue is what happens at the centre of the process – the magnetic ‘null’ point. Cluster data have led to the first 3D picture of a null, the magnetic heart of reconnection. Vital new insights include showing that the magnetic field can be twisted into 500 km-wide tubes.
Understanding magnetic reconnection is a major quest in physics. It is responsible for tremendous solar explosions – solar flares – that can be a billion times more powerful than an atomic bomb. In the magnetotail, magnetic reconnection can funnel particles towards Earth, leading to increased auroral activity. In Earth’s laboratories, unwanted reconnection frustrates efforts to produce electricity in fusion reactors.