The aurora borealis is caused by energetic particles from the Sun interacting with Earth’s atmosphere and magnetic field, producing shimmering lights near the polar regions. Key points
- Source of energy: The Sun emits a stream of charged particles (the solar wind). When solar activity intensifies, such as solar flares or coronal mass ejections, the wind becomes faster and more intense, increasing geomagnetic activity on Earth.
- How it reaches Earth: The solar wind interacts with Earth’s magnetosphere. During disturbed conditions, enhanced electric fields and wave-particle interactions accelerate charged particles along magnetic field lines toward the polar regions.
- Where the light comes from: As these particles collide with atoms and molecules in the upper atmosphere (primarily oxygen and nitrogen), they excite those atoms. When the excited atoms return to their ground state, they emit light.
- Colors and altitudes: Different gases and altitudes produce different colors.
- Oxygen at about 60–150 miles (roughly 100–240 km) typically yields green and occasionally red at higher altitudes.
- Nitrogen can produce purples, blues, pinks, and reds, especially in lower or more energetic events.
- Shape and movement: The light often appears as curtains, bands, or rays that swirl and ripple due to the Earth’s magnetic field lines and atmospheric winds.
- Timing and visibility: Auroras are most often seen around the magnetic poles, but strong solar storms can push activity to lower latitudes and extend visibility to wider areas, including parts of mid-latitude skies.
If you’d like, I can tailor this explanation to a specific aspect (e.g., the physics of particle acceleration, why colors vary, or how observers can predict aurora activity).
