Aurora Science

The Science of the Northern Lights

From solar eruptions to dancing green curtains — here's what actually happens

The Aurora Process

Four steps from solar surface to Icelandic sky

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Step 01

Solar Wind

The sun constantly emits a stream of charged particles — mostly electrons and protons — called the solar wind. This plasma travels at 400–800 km/s and reaches Earth in 1–3 days.

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Step 02

Earth's Magnetosphere

Earth's magnetic field acts as a shield, deflecting most solar wind around the planet. But at the poles, magnetic field lines converge and funnel particles inward toward the atmosphere.

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Step 03

Atmospheric Collision

Funneled particles collide with oxygen and nitrogen molecules at 100–300 km altitude. The collisions excite the gas molecules, boosting electrons to higher energy states that release light as they return to normal.

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Step 04

Aurora Display

The energy released creates the aurora — shimmering curtains, arcs, and rays of light that dance across the night sky. The shapes shift with changes in the solar wind and Earth's magnetic field.

The KP Index Explained

The Planetary K-index (Kp) measures global geomagnetic activity on a scale from 0 (very quiet) to 9 (extreme storm). It is derived from magnetometers at 13 stations worldwide and updated every 3 hours.

Aurora Glossary

GreenMost Common

Oxygen at 100–150 km altitude. The most common aurora color, produced when oxygen atoms are excited by colliding particles and emit green photons as they de-excite.

RedRare

Oxygen at 200+ km altitude. Rarer and typically only seen during strong geomagnetic storms when particles penetrate to very high altitudes.

Blue / PurpleLower Edge

Nitrogen molecules at lower altitudes below 100 km. Often visible as a distinct blue-purple fringe at the bottom edge of green aurora curtains.

White / YellowBlended

A mixture of green and red oxygen emissions at overlapping altitudes. Appears white or yellow when multiple emission layers blend together.

Why is aurora only visible at night?

Sunlight is far brighter than the faint glow of aurora. You need full astronomical darkness — typically 90+ minutes after sunset — for your eyes to dark-adapt and the aurora to become visible against the sky.

Can aurora happen in summer?

Not visibly in Iceland due to the midnight sun (May–August). Solar particles still arrive and collisions still happen, but Iceland's sky never gets dark enough for aurora to be seen. Season runs September to April.

Why does aurora 'dance'?

Variations in the solar wind — changes in speed, density, and magnetic field direction — cause Earth's magnetic field lines to shift and vibrate. Aurora attached to those field lines moves, ripples, and dances in response.