UPSC Mains 2024 GS1 Q15: model answer

Auroras are natural light displays in the night sky near the poles. In the northern hemisphere they are called aurora borealis (northern lights); in the southern, aurora australis (southern lights). They appear mainly in an oval belt around the magnetic poles: Norway, Alaska, Canada, Antarctica, southern New Zealand.

How they are triggered

• Solar wind: the Sun constantly emits charged particles. Solar flares and coronal mass ejections (CMEs) throw out large bursts.
• Earth's magnetosphere: the magnetic field deflects most particles, but along field lines near the poles they enter the upper atmosphere.
• Collision: particles strike oxygen and nitrogen atoms at about 100–300 km height, exciting them.
• Light: as atoms return to normal they emit light. Oxygen gives green (most common) and red (higher altitude); nitrogen gives blue and purple.

Geomagnetic storms

• Strong CMEs compress the magnetosphere and push the auroral oval towards the equator.
• In May 2024 a severe (G5) geomagnetic storm produced auroras visible as far south as Ladakh; the Indian Astronomical Observatory at Hanle recorded them.
• Activity peaks near the solar maximum of the roughly 11-year sunspot cycle.

Significance

• Such storms can disrupt satellites, GPS, radio and power grids.
• ISRO's Aditya-L1 studies the Sun's activity for space weather forecasting.

Auroras are beautiful reminders that Earth lives inside the Sun's atmosphere and depends on its magnetic shield.