What are aurora australis and aurora borealis? How are these triggered?

What the Auroras Are

Auroras are luminous, shifting curtains of light that appear in the night sky at high latitudes. Aurora borealis (northern lights) occurs around the Arctic — over Norway, Iceland, Canada and Alaska — while aurora australis (southern lights) is its mirror over Antarctica, Tasmania and southern New Zealand. Both occur in ring-shaped 'auroral ovals' centred on Earth's geomagnetic poles, at altitudes of roughly 90–400 km in the thermosphere. The name derives from Aurora, the Roman goddess of dawn, with 'borealis' and 'australis' denoting north and south.

How They Are Triggered

• The Sun continuously ejects the solar wind — a stream of charged particles (electrons and protons) travelling at 300–800 km per second.
• Earth's magnetic field deflects most of this stream, but magnetic reconnection in the magnetosphere's tail accelerates some particles along field lines towards the poles.
• These precipitating electrons collide with atmospheric gases: excited oxygen emits the characteristic green and, at higher altitudes, red light, while nitrogen produces blue, purple and pink fringes.
• Because field lines converge at both magnetic poles, the displays occur nearly simultaneously in the two hemispheres as mirror images.

Why Intensity Varies

• Solar flares and coronal mass ejections (CMEs) hurl plasma at Earth, causing geomagnetic storms that push the auroral ovals towards lower latitudes.
• Activity peaks with the 11-year solar cycle; the Solar Cycle 25 maximum produced the May 2024 storm — the strongest since 2003 — when red auroral glow was photographed even from Hanle, Ladakh.

Conclusion

Auroras are thus the visible signature of Sun–Earth interaction: solar wind particles, guided by the magnetosphere, energising the upper atmosphere. The same geomagnetic storms can disrupt satellites, GPS and power grids, making auroral science central to space-weather preparedness — a field India has joined with Aditya-L1.