The Science of the Northern Lights

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.

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.

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.

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.

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.

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

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

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