Aurora — Curtains in the Sky

Aurora is probably the most visually overwhelming phenomenon in nature.

Solar Wind

The sun constantly emits charged particles (protons, electrons) into space. That's solar wind. It blows all the time, but gets much stronger during solar flares.

Earth's Magnetic Field

Earth is a giant magnet. The magnetic field blocks most solar wind, but near the poles (north/south), magnetic field lines converge into the atmosphere. Charged particles from solar wind follow these field lines into the polar atmosphere.

Light Generation

When charged particles entering the atmosphere collide with nitrogen (N₂) or oxygen (O₂) molecules, atmospheric molecules' electrons jump to excited states then drop back down, emitting light. Same principle as fluorescence.

Green: Oxygen molecules, most common at 100-300km altitude

Red: Oxygen molecules, occurs above 300km (slow energy transition)

Purple/pink: From collisions with nitrogen molecules

Where to See Aurora

Magnetic latitude 65-72° is the auroral zone. Norway, Iceland, northern Canada, Alaska. It also appears in Antarctica (aurora australis), but there's almost no land to observe from.

During strong solar activity, the auroral zone expands, making aurora visible at lower latitudes.