The Northern Lights

The Northern Lights are glowing curtains, spirals, and streaks of colour that appear in the night sky near the North Pole. (The South Pole has its own version — called Aurora Australis.)

The Sun constantly throws off a solar wind — a stream of tiny charged particles. When they reach Earth, our planet's magnetic field guides them toward the poles. There, they slam into oxygen and nitrogen atoms high in the atmosphere. Those collisions make the atoms glow — exactly like a neon sign.

The solar wind carries the Sun's own magnetic field to Earth. Scientists measure its north–south direction and call it Bz. It works like a dial that controls how strongly solar particles can pour into Earth's upper atmosphere.

Auroras can happen with Bz pointing in either direction — but the direction makes a huge difference to how bright and active they are.

The Kp-index is a number from 0 to 9 that measures how much Earth's magnetic field is being disturbed. Think of it as a storm intensity meter for auroras — the higher the number, the further south you can see them.

The colour depends on which gas is hit and how high up the collision happens.

You need three things at the same time: the right space weather, the right location, and the right local sky.

Of these, clear sky is the one you can't work around. The most powerful solar storm in years is useless if you're looking up through a cloud.

The aurora doesn't disappear in summer — the Sun is just as active. But you can't see something that glows in the dark if the sky is still lit. At high Arctic latitudes, the summer sun barely sets at all. You need a truly dark sky.

There are three types of night to know about:

Aurora season runs September to March — but not all months are equal. Around the spring and autumn equinoxes (mid-March and mid-September), aurora activity is statistically about 50% higher than in December or January, even with similar solar activity.

The reason is geometry: twice a year, Earth's magnetic field is tilted in exactly the right way relative to the solar wind to let far more particles in. Scientists call this the Russell–McPherron effect. It's reliable enough to plan around.

The Sun isn't constant — it pulses through an 11-year cycle of activity, swinging between a quiet minimum and a stormy maximum. At solar maximum, sunspot counts surge, solar flares are more frequent, and geomagnetic storms — the kind that light up the sky — happen far more often.

Solar Cycle 25 peaked around 2024–2025 — one of the strongest cycles in decades. The extraordinary aurora storms of May 2024, visible across Europe, the southern US, and even parts of Mexico, happened because of this peak. We're now just past maximum, meaning activity is still high and exceptional events remain far more likely than they will be in 3–4 years.

This surprises almost every first-time aurora watcher: your phone or camera can capture aurora that is completely invisible to your naked eye. The human eye struggles in very low light and is poor at detecting colour at night. Camera sensors don't have this limitation.

Not all solar activity is the same. There are three types of events that affect aurora, and they work very differently — which is why a "5-day aurora forecast" is nearly useless, but a "1-hour forecast" is highly reliable.

Even on a perfect aurora night, the display rarely stays on continuously. It comes in bursts called substorms — sudden intensifications that last 20 to 60 minutes, often followed by quiet periods of 30 minutes to an hour before the next one fires.

A substorm happens when energy that has been building up in Earth's magnetic tail suddenly snaps and releases — like a stretched elastic band. The result is a rapid brightening, often starting as a quiet arc low on the horizon that suddenly erupts into dancing curtains overhead.

Here's what a real aurora forecast looks like — and what each number means for your evening.

Every night goes through the same logic — in this exact order.