How to see the aurora: forecasts, dark skies and where to go

TUREFF• •0

Few natural sights compare with the aurora: curtains of green, red and violet light moving across the night sky. Seeing it takes a mix of preparation and luck, but knowing how forecasts work and where to stand improves your chances enormously, whether you are travelling to the far north or hoping for a display closer to home.

What causes the aurora

The sun constantly sends out a stream of charged particles called the solar wind, and occasionally releases larger eruptions. When these reach Earth, they interact with our planet's magnetic field and energise particles that collide with gases high in the atmosphere, which then glow. Oxygen produces the common green and rarer red colours; nitrogen can add blue and purple. The effect is usually concentrated in oval-shaped zones around the magnetic poles: the aurora borealis in the north and the aurora australis in the south.

The solar cycle

The sun's activity rises and falls over a cycle of roughly 11 years. Space weather scientists believe the current cycle reached its maximum in recent years and is now in its declining phase. That does not mean the shows are over: strong eruptions and geomagnetic storms can still happen as the cycle winds down, and some of the most powerful storms historically have come during this phase. Displays far from the poles become less frequent, but remain possible.

Reading the forecasts

Short-term forecasts are the most useful. Space weather agencies such as the US National Oceanic and Atmospheric Administration publish a model forecast of where the aurora is likely to be visible over roughly the next half hour to hour and a half, based on solar wind measured by spacecraft between Earth and the sun.
The Kp index is a scale from 0 to 9 describing global geomagnetic activity. Higher numbers mean the aurora may reach lower latitudes. It is a rough guide, not a guarantee, and some alert services prefer local magnetic measurements.
Local alert services help. In the UK, AuroraWatch UK, run by Lancaster University, issues alerts based on magnetometer readings, and the Met Office publishes space weather forecasts.
Longer-range forecasts of a few days ahead are uncertain. Treat them as a reason to watch the sky, not a promise.

Clear skies matter as much as space weather, so check the cloud forecast too.

Where to go

High latitudes give the best odds. Northern Norway, Sweden and Finland, Iceland, northern Canada and Alaska sit under or near the auroral oval. In the south, Tasmania, the south of New Zealand and Antarctica are the main options.
In the UK, northern Scotland, including the Highlands, Orkney and Shetland, has the most frequent displays, but during strong storms the aurora has been seen across much of the country.
Dark sky places make a big difference. Designated dark sky parks and reserves, open coastlines and hills with a clear northern horizon (or southern, in the Southern Hemisphere) are ideal.
Darkness is required. At very high latitudes, summer nights are too light, so the main viewing season runs from autumn to spring.

On the night

Get away from lights and let your eyes adapt for at least 20 minutes. Use a red torch.
Look towards the pole. Faint displays often start as a pale arch or glow low on the horizon.
Use your phone camera. Camera sensors pick up colour the eye cannot, so a grey glow may appear green or pink in a photo. Night mode on a steady surface or a small tripod works well.
Be patient. Activity often comes in bursts, with quiet spells in between.
Dress for the cold with layers, a hat and gloves, and bring a hot drink.

Staying safe

Check road and weather conditions, tell someone where you are going, and do not stop on roads or park in passing places to look up. On coasts and cliffs, check tides and stay well back from edges in the dark. Have you seen the aurora, and where? Share your sightings and tips in the comments.