The games the Sun plays.

The story of the northern lights begins not on Earth but 150 million kilometres away — in the Sun's fits of rage.

Charged particles streaming from the Sun do not travel in a straight line through the void; the Sun's magnetic field bends them onto a curved path. Because the Earth has a magnetic field of its own, these particles are captured at the poles and all but imprisoned there. Our atmosphere acts as an immense shield, protecting life even through the fiercest solar flares.

How light is born.

Hydrogen, oxygen and nitrogen in the upper atmosphere are ionised by the radiation the wind carries and interact with free electrons. As those electrons drop in energy, light is emitted at various wavelengths — mostly green, sometimes red and blue, very rarely pink.

The Sun's fury: the CME.

The strongest auroras are made by mass eruptions from the Sun's surface — coronal mass ejections. These outbursts trigger geomagnetic storms; the aurora can then be seen not only from the poles but from latitudes far closer to the Equator.

Spots and knots.

Sunspots are regions roughly 2000 degrees cooler than their surroundings; that difference in temperature makes them stand out as distinct dark patches. They form where the magnetic field is contorted. Because the Sun's equator spins faster than its poles, magnetic knots holding immense plasma are born; these bubbles eventually burst, hurling charged gases into space and strengthening the wind.

The Sun, under the lens.

Thanks to satellites watching the Sun around the clock, a three-day space-weather forecast is now possible. Flares, their intensities, the instantaneous wind speed and the amount of particles carried can all be measured — so we can predict where and at what strength the aurora will form. When the Sun is quiet the wind is calm and the polar latitudes see average activity; the moment a flare or mass eruption occurs, the forecasts change at once.