Home▸Physics & Mechanics▸Aurora Colours And The Oval

🌌 Why the Aurora Is Green (and Sometimes Red, Blue or Pink)

What determines the colour of the aurora, why it forms an oval around the magnetic poles, and how the Kp index maps that oval down to latitudes like the UK.

Physics & Mechanics3DAdvanced60 FPS

A 3D model of the auroral oval — the glowing ring of light circling the magnetic pole — showing how particle energy sets its colour and how the Kp index drags it down toward latitudes like the UK.

🔬 What It Demonstrates

Green comes from oxygen at 100–150km struck by moderate-energy electrons; red from oxygen higher up; blue and pink fringes from nitrogen when only the most energetic particles punch down below 100km. Raising Kp both brightens and widens the oval, pushing its edge equatorward until it reaches the UK's magnetic latitude.

🎮 How to Use

Drag the Kp index up to simulate a stronger geomagnetic storm and watch the oval expand and brighten. Slide particle energy to shift the colour balance, then switch to UK ground view to see what the horizon would look like from Scotland during that storm.

💡 Did You Know?

The magnetic north pole sits over northern Canada, not the geographic pole — which is why the UK's magnetic latitude is higher than its map latitude, and why a Kp of roughly 5 or more is usually the threshold for a visible display from the UK.

⚙ Under the hood

What determines the colour of the aurora, why it forms an oval around the magnetic poles, and how the Kp index maps that oval down to latitudes like the UK.

Aurora BorealisMagnetic FieldsAtmosphereLight PhenomenaGreen ColorKp IndexThree.js

3D · Three.js / WebGL renderer · 60 FPS target · runs fully client-side, no install