The solar wind paints earth's skies with auroras and pushes solar sails through space. But just how the streams of electrically charged particles flow out of the sun has been a mystery until now.

Pockets of hot gases on the sun's surface, which pool around bright knots of magnetic activity, spurt out into space when the sun's snarling, snaking magnetic fields collide.

"[The phenomenon] has been debated for many years," says Professor Louise Harra, a University College London researcher who this week unveiled the sun's secret at a Royal Astronomical Society meeting in Belfast.

Harra planned to show images from the orbiting Hinode spacecraft showing magnetic fields linking two bright spots on the sun.

The spots are nearly 500 million kilometres apart, a distance equivalent to 40 earths placed side by side.

When the magnetic fields smashed into each other, charged gases flew out in all directions, forming the solar wind.