How the aurora forms
Charged particles from the solar wind follow Earth's magnetic field. The ones aimed along a field line spiral down into the atmosphere and make it glow.
Reaching the atmosphere0 /s
Trapped in radiation belts0
Spiral radius (r = mv/qB)1.00×
- Particles moving almost along the field (inside the loss cone) reach the atmosphere.
- Particles with steeper pitch angles mirror and bounce between the hemispheres, trapped in the Van Allen belts.
- Green: oxygen at ~100–250 km (557.7 nm) Red: oxygen above ~250 km (630 nm) Purple: nitrogen at the lower edge
- Not to scale: the aurora is only ~100–400 km high, and its height is exaggerated here so it shows up.