Auroras are spectacular natural light displays seen in high-latitude regions near the polar areas, caused by interactions between solar particles and Earth’s atmosphere.
What causes auroras?
- The Sun emits charged particles (electrons and protons) through the solar wind.
- Earth’s magnetic field funnels these particles toward the polar regions.
- Particles collide with gases in the upper atmosphere, mainly in the thermosphere/ionosphere (≈100–400 km).
- These collisions excite atmospheric gases; when they return to normal energy states, they emit light—this is the aurora.
Where do auroras occur?
- Concentrated in oval-shaped zones around the magnetic poles called auroral ovals.
- Northern Hemisphere: Aurora Borealis
- Southern Hemisphere: Aurora Australis
Why different colours?
- Green (most common): Oxygen (~100–150 km)
- Red: Oxygen (>200 km)
- Blue/Purple: Nitrogen (lower altitudes)
- Colour depends on gas type, altitude, and energy of particles.
Which atmospheric layer?
- Primarily the thermosphere, overlapping with the ionosphere.
- Linked to ionisation processes that also affect radio communication.
When are auroras strongest?
- During solar storms, coronal mass ejections (CMEs), and periods of high solar activity.
- Can expand to lower latitudes during intense geomagnetic storms.
Why are auroras important (beyond beauty)?
- Indicators of space weather conditions.
- Strong events can disrupt:
- Satellites
- GPS
- Radio communications
- Power grids
