Aurora

Why in news?

• The northern lights, aka the aurora borealis, have been appearing more frequently in the night sky over the United States recently

About Aurora:

• An aurora sometimes referred to as polar lights is a natural light display in the Earth's sky, predominantly seen in the high-latitude regions (around the Arctic and Antarctic).
• The lights are seen above the magnetic poles of the northern and southern hemispheres between 60°-75° latitudes.
• Northern lights (aurora borealis) are in the Arctic Circle and southern lights (aurora australis) in the Antarctic Circle.
• Northern Lights can be seen from the US (Alaska), Canada, Iceland, Greenland, Norway, Sweden and Finland.
• In the south southern lights are visible from high latitudes in Antarctica, Chile, Argentina, New Zealand and Australia.

How are they formed?

• Solar wind from the sun consists of charged particles moving towards the earth and rest of the solar system from the solar surface.
• As the Solar wind approaches the earth, most of the particles are deflected away by the geomagnetic field, but some escape into our atmosphere around the magnetic poles.
• As the charged particles enter the earth's upper atmosphere, they will collide with atoms and molecules in our atmosphere.
• These collisions result in ionization and excitation of atmospheric constituents that emits light of varying color and complexity, which make up the aurora.

PRACTICE QUESTION

With reference to ‘Aurora’ formation, consider the following statements:

1. It is absent in northern hemisphere due to increased continentality

2. It is caused when electrically-charged particles from the sun collide with particles present in the Earth’s atmosphere

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer