In short
The aurora appears when energy from the Sun is channelled by Earth's magnetic field into the upper atmosphere, where it makes gases glow. The light you see shines roughly 100–300 km above the ground, far above clouds and aircraft.
From the Sun to Earth
The Sun constantly blows out a stream of charged particles, the solar wind, which carries the Sun's magnetic field with it. Now and then it also launches a much larger cloud of plasma, a coronal mass ejection (CME). When a CME or a fast solar-wind stream hits Earth, our magnetic field is shaken: a geomagnetic storm.
Earth's field deflects most of that energy. But when the magnetic field carried by the solar wind points southward (what hunters call "negative Bz"), the two fields connect and energy leaks into the magnetosphere. Electrons are then accelerated down along magnetic field lines into the atmosphere near the poles. They hit oxygen and nitrogen, excite them, and the atoms release light as they relax, much like a fluorescent tube on a planetary scale.
That is why the aurora forms in a ring around each magnetic pole, the auroral oval. The stronger the storm, the wider the oval grows and the further it reaches towards the equator.
Where the colours come from
- Green (557.7 nm): the most common colour, from atomic oxygen at roughly 100–150 km.
- Red (630.0 nm): also oxygen, but higher up, above roughly 200 km. When mid-latitude observers see aurora during big storms, it is often these red tops peeking over the horizon.
- Purple and blue: from nitrogen, usually along the lower edge of curtains or in sunlit upper layers.
- Pink lower fringe: during very intense moments, nitrogen can add a pinkish band below the curtains.
Your eyes struggle to see colour in the dark, so a faint aurora can look like a greyish-white cloud while a phone camera records clear green and red. See our photography guide.
North and south
Aurora happens at both poles at the same time: aurora borealis in the north and aurora australis in the south. Norway, Sweden, Finland, Iceland, Canada and Alaska are the classic northern destinations; Tasmania, southern New Zealand and Antarctica in the south, where much of the oval lies over ocean.
Is it harmful? No.
The aurora forms hundreds of kilometres overhead and its light carries no radiation to the ground. Standing under it, photographing it or watching it with children is completely safe. Strong geomagnetic storms can affect technology such as satellites, GPS accuracy, HF radio and power grids, which operators monitor. A person standing outside faces no risk.
Not an earthquake warning
When the 2024 storms made the aurora visible from Turkey, some outlets spread the claim that "lights in the sky" foretell earthquakes. There is no scientific basis for this. The aurora is light produced about 100 km up by solar energy; earthquakes come from stress building up on faults kilometres below the surface. A study by US Geological Survey researchers comparing long records of solar activity and global earthquakes found no meaningful link (Love & Thomas, 2013). The Turkish Space Agency also stated in October 2024 that the sightings were the natural result of a G4 geomagnetic storm.
Seeing the aurora from Turkey is rare and beautiful, not a warning.