🌌 Aurora Colours & the Auroral Oval

About this simulation

The aurora is not painted across the whole sky at random — it forms a near-permanent glowing ring called the auroral oval, centred on the magnetic (not geographic) pole. Its colour comes from solar-wind electrons and protons striking oxygen and nitrogen atoms high in the atmosphere, exciting them to glow at wavelengths that depend on which gas and how deep the particles penetrate.

How it works

• Green (~100–150km) — the classic colour, from oxygen atoms excited by moderate-energy electrons; the most common emission because this altitude band is struck most often.
• Red (~200–300km+) — oxygen glows red at higher altitudes, but this transition is slower and needs low particle density, so it dominates only at the oval's upper edge or during quiet, diffuse aurora.
• Blue / pink (<100km) — nitrogen molecules produce blue and magenta fringes, but only very energetic electrons punch down this far — a sign of an intense substorm.
• Kp index — a 0–9 scale of global geomagnetic disturbance. As Kp rises, the oval both widens and expands equatorward, bringing the aurora down to lower latitudes like Scotland or even southern England.

Controls

• Kp index — sets geomagnetic storm strength; higher values push the oval toward the equator and brighten it.
• Particle energy — shifts the colour balance from a soft, red-topped glow (low energy) to an intense green curtain with a blue/pink lower fringe (high energy).
• Space / UK ground view — jump between an orbital view of the whole oval and a view from the ground in the UK looking north.
• Substorm toggle — simulates the pulsing brightening of an active substorm.

Did you know?

Because the magnetic pole sits over northern Canada, not the geographic pole, the UK's magnetic latitude is higher than its map latitude — which is why Scotland sees aurora far more often than its geographic latitude alone would suggest, and why a Kp of about 5 or more is typically needed for a decent show over the UK.