What Causes the Northern Lights? The Science, Simply

The aurora can feel like magic, but it's a predictable bit of space weather. Here's what's actually happening when the sky lights up over Alaska.

It starts at the sun

The sun constantly throws off charged particles — the solar wind. When a burst of them reaches Earth, our planet's magnetic field funnels them toward the poles.

The colors

As those particles hit gases high in the atmosphere, the gases glow. Oxygen produces the common green (and rarer red); nitrogen adds blues and purples. Altitude and gas determine the color.

Why Alaska

The action concentrates in a ring around each magnetic pole — the auroral oval. Fairbanks sits right under it, which is why it sees the lights so often.

Reading the forecast

Activity is measured on the Kp index (0–9). Higher Kp means the oval expands and the aurora gets brighter and reaches farther south. The UAF Geophysical Institute publishes a nightly forecast.

Ready to see it? Our Aurora Season guide, the best spots near Fairbanks, and how to photograph it.