The aurora borealis, or northern lights, is the glow produced when charged particles from the Sun are funnelled down Earth's magnetic field lines into the upper atmosphere, where they collide with oxygen and nitrogen and force those atoms to shed the energy as light. It is not visible from a ring of latitude. It appears in an oval centred on the geomagnetic north pole, which currently sits off the northwest coast of Greenland rather than at the geographic pole — an offset of more than 1,000 km. That single fact explains most of the confusion in aurora travel planning: Fairbanks, Alaska, at 64.8°N, sits almost directly beneath the oval, while Yakutsk in eastern Siberia, only a little further south at 62°N, sits well inside it and sees a small fraction as much. On a magnetically quiet night the oval lies over interior Alaska, the Northwest Territories, southern Greenland, Iceland and northern Scandinavia. During a severe geomagnetic storm it expands far enough south to reach Britain, Germany and the northern United States.
The Auroral Oval, Not the Arctic Circle
Earth's magnetic field behaves, to a first approximation, like a bar magnet buried at the centre of the planet and tilted about 11° away from the rotation axis. The point where the northern end of that tilted axis emerges is the geomagnetic north pole, and in the 2020s it lies near 80.7°N, 72.7°W — over the sea between Ellesmere Island and northwest Greenland. Auroras organise themselves around that point, not around the geographic pole, because it is the magnetic field, not the spin axis, that steers the incoming particles.
The practical consequence is that geographic latitude is a poor predictor and magnetic latitude is a good one. Fairbanks sits at 64.8°N geographic and roughly 65° magnetic, which places it under the oval on a typical night. Reykjavík, at 64.1°N geographic, has a magnetic latitude of about 64° and performs similarly. Tromsø, at 69.6°N, sits at roughly 67° magnetic and is arguably the single best-served city on Earth. Yakutsk, by contrast, sits at 62°N geographic but only about 51° magnetic, because the Siberian sector is on the far side of the offset. Travellers who pick a destination by looking at how far north it is on a map routinely get this backwards.
The same offset works in North America's favour at the other end. Edmonton and Calgary, at 53°N and 51°N, are at the latitude of central England, but their magnetic latitude is high enough that they catch auroras several times a year without any exceptional storm. London, at 51.5°N, needs a genuinely severe event. If you want to understand the underlying machinery that produces the oval, the site's explainer on what the magnetosphere is covers the field structure this article assumes.
What Actually Makes the Light
The Sun continuously sheds a stream of charged particles called the solar wind, typically moving at 300–800 km per second. That wind cannot easily cross Earth's magnetic field, so it drapes around it, compressing the field on the dayside and drawing it out into a long magnetotail on the night side. Energy accumulates in that tail. When it is released — through a process called magnetic reconnection, in which stretched field lines snap into a lower-energy configuration — particles are flung back toward Earth along the field, accelerated to energies of a few thousand electronvolts, and dumped into the atmosphere at high latitude.
That release is a substorm, and it is what aurora watchers are really waiting for. A substorm typically begins with a quiet arc lying east–west across the northern sky, which brightens abruptly, breaks into folds and rays, and surges poleward over perhaps ten to thirty minutes before fading into a patchy, pulsating glow. Two or three substorms in a night is common on an active evening. The geomagnetic activity level is summarised by the Kp index, a 0–9 scale: Kp 2–3 is enough for Tromsø or Fairbanks, Kp 5 marks a geomagnetic storm and brings the oval down over Scotland and the northern Great Plains, and Kp 8–9 is the sort of event that reaches the Mediterranean. The short companion piece on what causes the northern lights covers this chain in brief.
Altitude Is the Palette
Aurora colours are not decorative variation. Each one is a specific atom emitting at a specific height, and the height is set by how deeply the incoming particles penetrate and by how thin the air has to be for a given emission to survive.
- Green, 557.7 nm, roughly 100–150 km: atomic oxygen. This is the dominant colour of nearly every aurora, partly because oxygen is abundant at that height and partly because human night vision is most sensitive close to that wavelength.
- Red, 630.0 nm, roughly 200–400 km: also atomic oxygen, but from a longer-lived excited state. That state takes around 110 seconds to decay, so it only produces light where the air is thin enough that the atom is not knocked out of it by a collision first. Below about 200 km it is quenched, which is why red sits above green rather than mixing with it.
- Blue and violet, 427.8 nm, below 100 km: ionised molecular nitrogen, produced only when particles are energetic enough to punch deep. This is a storm colour.
- Pink and magenta fringes: nitrogen emission along the lower edge of a bright green curtain, usually visible only during strong substorms.
This layering is also why photographs and eyes disagree. The red emission is genuinely faint, and human colour vision largely shuts down at low light levels, so a display the eye reads as pale grey-green can render on a camera sensor as vivid green with a crimson crown. Neither is wrong; the camera is simply integrating for several seconds.
Solar Cycle 25 and the Window That Is Closing
Auroral activity follows the roughly eleven-year sunspot cycle. Solar Cycle 25 substantially exceeded the official forecast, with sunspot numbers peaking through 2024 and 2025. That produced the storm of 10–11 May 2024 — classified G5, the first at that level since October 2003 — during which auroras were reported from Florida, Mexico and the Caribbean in the north and from South Africa in the south. The largest event on record remains the Carrington Event of September 1859, which lit the sky over Cuba and set telegraph equipment sparking.
The declining phase of a solar cycle is not a bad time to travel, and this is widely misunderstood. Sunspot maximum brings the coronal mass ejections that produce the spectacular one-off storms, but the years after maximum bring a different and more reliable driver: coronal holes, which emit fast solar wind streams that recur with the Sun's 27-day rotation. Those streams favour the equinoxes, because Earth's magnetic field is then oriented to couple most efficiently with the incoming wind. It is the reason September–October and February–March consistently outperform December, despite December offering the longest nights. The practical window through 2026 to 2028 remains good.
Following the Oval West to East
Ordered the way the oval crosses inhabited land, starting in Alaska:
- Fairbanks and Chena Hot Springs, Alaska: almost directly under the oval, with a dry continental interior climate that keeps winter skies clear. Roughly 200 aurora-visible nights a year given clear weather.
- Yellowknife, Northwest Territories: the strongest statistical bet in North America. Subarctic continental air, very low winter cloud, and a position squarely beneath the oval.
- Churchill, Manitoba: lower latitude but high magnetic latitude, and a long-established viewing infrastructure built around the same season as the polar bear traffic.
- Iqaluit and Baffin Island, Nunavut: under the oval, though coastal cloud is more of a factor than in the continental interior.
- Kangerlussuaq, Greenland: inland at the head of a long fjord, sheltered from coastal weather, and one of the clearest sites in the Arctic.
- Þingvellir and the Icelandic interior: excellent magnetic position undermined by a maritime climate; cloud, not activity, is the limiting factor here.
- Tromsø and Alta, Norway: the most accessible high-magnetic-latitude cities anywhere, with flights, roads and the option to drive inland when the coast clouds over.
- Abisko, Sweden: sits in the rain shadow of the Scandinavian mountains beside Lake Torneträsk, receiving only about 300 mm of precipitation a year — the driest corner of Sweden, and locally known for a persistent gap in the cloud.
- Utsjoki and Finnish Lapland: inland, dry, dark, and far enough north to catch quiet-night displays.
- Murmansk and the Kola Peninsula, Russia: good magnetic latitude, with the same coastal cloud problem as northern Norway.
What Goes Wrong on an Aurora Trip
Almost every disappointed aurora traveller was defeated by cloud rather than by the Sun. The oval is overhead far more often than the sky is clear, which argues for continental interiors — Yellowknife, Fairbanks, Abisko, inland Greenland — over maritime destinations, and for a trip of at least three and preferably five nights. A single-night booking is close to a coin flip even in the best locations.
Two other assumptions cause trouble. The first is that a full moon ruins the display; it does not, and moonlight usefully illuminates foreground landscape, though it will wash out the faintest arcs. The second is the expectation set by photographs. Long-exposure images represent something real but they compress twenty seconds of light into one frame, and a first-time viewer expecting that intensity in real time often fails to recognise a genuine quiet arc overhead. Learn to spot the faint grey-green band first; the folds and the colour arrive when a substorm breaks.
Finally, the aurora is not the only thing worth looking up for on an Arctic night — the same latitudes deliver noctilucent clouds in high summer and, on rare evenings, the mauve ribbon of STEVE, which turns out not to be an aurora at all.
