Electrically charged particles from space travelling at speeds of several hundred km/sec can severely harm human beings if they reach the surface of the Earth. What prevents them from reaching the surface of the Earth? (UPSC Prelims 2012)

Question

The correct answer is [A]. The Earth\'s magnetic field diverts them towards its poles. This phenomenon is a result of the Earth\'s magnetosphere, which acts as a protective shield against high-energy charged particles (mostly protons and electrons) emanating from the Sun (solar wind) and cosmic rays from outer space.

Earth\'s Magnetic Field (Statement A is Correct): The Earth acts like a giant bar magnet with magnetic field lines emerging from the southern hemisphere and entering at the northern hemisphere. When electrically charged particles approach Earth, the Lorentz force exerted by the magnetic field causes them to deflect. Instead of hitting the Earth\'s surface directly, these particles are trapped and diverted along the magnetic field lines toward the North and South Poles. When these particles collide with gas molecules in the upper atmosphere near the poles, they create the beautiful light displays known as Auroras (Aurora Borealis and Aurora Australis).
Ozone Layer (Statement B is Incorrect): The ozone layer, located in the stratosphere, is primarily responsible for absorbing harmful ultraviolet (UV) radiation from the Sun. It does not reflect or stop high-speed electrically charged particles from space.
Moisture in the Atmosphere (Statement C is Incorrect): While moisture (water vapor) in the atmosphere plays a critical role in weather patterns and the greenhouse effect, it does not have the capacity to stop high-energy, electrically charged subatomic particles traveling at several hundred kilometers per second.
Magnetosphere Protection: Without the Earth\'s magnetic field, these charged particles would strip away the atmosphere over time (as is thought to have happened on Mars) and would cause significant genetic damage to living organisms and disrupt electronic communication systems on the surface.

GKToday Admin · Accepted Answer

The Earth\'s magnetic field diverts them towards its poles The correct answer is [A]. The Earth\'s magnetic field diverts them towards its poles. This phenomenon is a result of the Earth\'s magnetosphere, which acts as a protective shield against high-energy charged particles (mostly protons and electrons) emanating from the Sun (solar wind) and cosmic rays from outer space.

Earth\'s Magnetic Field (Statement A is Correct): The Earth acts like a giant bar magnet with magnetic field lines emerging from the southern hemisphere and entering at the northern hemisphere. When electrically charged particles approach Earth, the Lorentz force exerted by the magnetic field causes them to deflect. Instead of hitting the Earth\'s surface directly, these particles are trapped and diverted along the magnetic field lines toward the North and South Poles. When these particles collide with gas molecules in the upper atmosphere near the poles, they create the beautiful light displays known as Auroras (Aurora Borealis and Aurora Australis).
Ozone Layer (Statement B is Incorrect): The ozone layer, located in the stratosphere, is primarily responsible for absorbing harmful ultraviolet (UV) radiation from the Sun. It does not reflect or stop high-speed electrically charged particles from space.
Moisture in the Atmosphere (Statement C is Incorrect): While moisture (water vapor) in the atmosphere plays a critical role in weather patterns and the greenhouse effect, it does not have the capacity to stop high-energy, electrically charged subatomic particles traveling at several hundred kilometers per second.
Magnetosphere Protection: Without the Earth\'s magnetic field, these charged particles would strip away the atmosphere over time (as is thought to have happened on Mars) and would cause significant genetic damage to living organisms and disrupt electronic communication systems on the surface.

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