Electrically charged particles from space travelling at speeds of several hundred km/sec can severel

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UPSC Prelims is a competitive examination conducted in India. This question is from the 2012 UPSC Prelims Science & Technology paper.

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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?

Accepted Answer

Correct Answer: A — The Earth's magnetic field diverts them towards its polesSolution:The electrically charged particles referred to here are primarily those from the solar wind (protons, electrons, alpha particles) and cosmic rays. These charged particles cannot travel in straight lines through a magnetic field — they follow curved paths (Lorentz force). The Earth's magnetosphere (the region dominated by Earth's magnetic field, extending tens of thousands of kilometres into space) deflects most of these particles, channelling them along field lines towards the polar regions.This is why: (1) Auroras (Northern and Southern Lights) occur near the poles — where deflected charged particles interact with the upper atmosphere; (2) Solar storms are most dangerous near the poles; (3) Astronauts on the ISS (within Earth's magnetic protection) are far safer than those outside it. The Van Allen Radiation Belts (inner and outer) are regions where trapped charged particles form intense radiation zones.Why other options are incorrect:Option B (Ozone layer reflects charged particles): The ozone layer absorbs ultraviolet radiation — it does not reflect electrically charged particles. UV is electromagnetic radiation, not charged particles. The ozone layer has no magnetic or electrical properties to deflect charged particles.Option C (Moisture in upper layers prevents them): Upper atmospheric moisture (water vapour) cannot prevent the passage of high-energy charged particles. The interaction of moisture with charged particles is negligible compared to the magnetospheric deflection.Option D (None of the above): Option A is the correct scientific explanation.Key Concept: Earth's magnetic field is generated by convection currents in the liquid outer core (geodynamo effect). The magnetosphere extends about 60,000 km on the sunward side and over 200,000 km on the opposite side (magnetotail). During geomagnetic storms (caused by coronal mass ejections from the Sun), the magnetosphere can be compressed, disrupting power grids, satellite communications, and GPS. The March 1989 geomagnetic storm caused a 9-hour blackout in Quebec, Canada. Mars lacks a global magnetic field — making its surface heavily bombarded by solar wind radiation, contributing to its atmospheric stripping over billions of years.

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?

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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?

Master UPSC Prelims with Our Test Series

More Questions from Physics Concepts – Laws, Motion, Optics & Thermodynamics

Frequently Asked Questions