Previous Year Question
Electrically charged particles from space travelling at speeds of several hundred km/sec can severely harm living beings if they reach the surface of the Earth. What prevents them from reaching the surface of the Earth?
Correct Answer: A
Detailed Solution
The Sun continuously releases a stream of charged particles, including electrons, protons and other ions, into space. This stream is known as the solar wind. Earth’s magnetic field, generated largely by the movement of liquid iron in its outer core, forms a vast protective region around the planet called the magnetosphere.
Option (a) is correct. Most solar-wind particles are deflected around Earth when they encounter the magnetosphere. Some particles can enter the magnetic environment and travel along magnetic-field lines towards the northern and southern magnetic poles. Their collisions with oxygen and nitrogen atoms and molecules in the upper atmosphere can produce the aurora borealis and aurora australis.
Earth’s magnetic field is not perfectly aligned with its geographical north-south rotational axis. Consequently, the magnetic and geographical poles are not situated at exactly the same locations.
Option (b) is incorrect. The ozone layer primarily absorbs harmful ultraviolet radiation, particularly UV-B and UV-C. It does not reflect high-speed charged particles back into space like a mirror.
Option (c) is incorrect. Moisture in the upper atmosphere is not Earth’s principal defence against these charged particles. Protection is provided mainly by the magnetosphere and, to some extent, the atmosphere.
Therefore, Earth’s magnetic field protects the planet by deflecting most charged particles and directing some of them towards the polar regions.