Q. What are aurora australis and aurora borealis? How are these triggered?
UPSC Mains 2024 GS1 Paper
Model Answer:
Aurora australis and aurora borealis
Aurora australis and aurora borealis, also known as the Southern and Northern Lights respectively, are spectacular natural light displays occurring in Earth’s polar regions. Aurora australis is visible primarily in Antarctica and southern parts of South America and New Zealand, while aurora borealis is observed in northern countries like Canada, Iceland, and Norway.
These auroras are characterized by:
• Colorful, dancing lights in the night sky
• Typical colors including green, pink, red, and sometimes blue or purple
• Varying shapes such as curtains, arcs, or swirling patterns
The triggering mechanism for both aurora australis and aurora borealis involves a complex interaction between solar particles, Earth’s magnetic field, and atmospheric gases:
1. Solar wind: The Sun emits a stream of charged particles, primarily electrons and protons, known as the solar wind.
2. Earth’s magnetic field interaction: As these particles approach Earth, they interact with our planet’s magnetic field. While most are deflected, some are trapped and funneled towards the polar regions along magnetic field lines.
3. Atmospheric collision: The charged particles enter the Earth’s upper atmosphere, typically at altitudes between 60 to 250 km, where they collide with atmospheric gases, primarily oxygen and nitrogen.
4. Energy release: These collisions cause the gas atoms to become excited and release energy in the form of light, creating the colorful auroral displays.
5. Color variation: The colors of the auroras depend on the type of gas molecules involved and the altitude of the collisions. Oxygen produces green and red lights, while nitrogen is responsible for blue and purple hues.
The intensity and frequency of auroras are influenced by solar activity, with more dramatic displays occurring during periods of increased solar storms and sunspot activity.
In conclusion, auroras are captivating phenomena that showcase the intricate connections between the Sun and Earth, providing both visual splendor and valuable scientific insights.
