The scales of magnetic reconnection

This sketch illustrate the different scales relevant to the ‘magnetic reconnection’ process.

The Earth’s magnetic field creates a buffer zone, the magnetosphere, between our planet’s atmosphere and the particles released during these eruptions. The Sun also releases a steadier flow of charged particles called the solar wind. On the large-scale, any heading this way buffet the magnetosphere, and are deflected by it. Plasma physicists describe this behaviour with a theory called ‘magneto-hydrodynamics’ (MHD).

On smaller scales, however, the picture becomes rather more complicated. The particles can actually flow across the magnetic field lines. First to misbehave are the ions (positively charged particles). These break away from simple MHD on scales of less than a few hundred kilometres. On even smaller scales, less than 10 kilometres, the electrons (negatively charged particles) begin playing by other rules, too.