MCQ Detailed View

Aurora Borealis, commonly known as the Northern Lights, is a fascinating natural phenomenon that appears as bright, colorful lights in the night sky of the northern hemisphere. These lights are usually red, green, or purple and are caused by the interaction of charged solar particles with the Earth's ionosphere.

The ionosphere is a high layer of Earth's atmosphere filled with charged particles called ions. When the Sun emits strong solar winds, streams of electrons and protons travel toward Earth at high speeds. As these charged particles reach the Earth, the planet's magnetic field guides them toward the polar regions. Upon entering the ionosphere, these particles collide with atoms of gases, mainly oxygen and nitrogen. These collisions excite the gas particles, causing them to release energy in the form of visible light, creating the stunning Aurora Borealis.

The color of the aurora depends on which gases are involved and the altitude of the collisions:

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  Green light: Produced when solar particles collide with oxygen at lower altitudes.

  
  


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  Red light: Produced by oxygen at higher altitudes.

  
  


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  Blue or purple light: Often caused by nitrogen molecules.

  
  

This phenomenon does not take place in the troposphere, mesosphere, or stratosphere, as these lower layers of the atmosphere do not receive enough charged solar particles to produce light. Only the ionosphere, located around 80–600 km above Earth’s surface, has the right conditions for this display.

A similar effect occurs in the southern hemisphere and is called Aurora Australis, or the Southern Lights. Both are examples of how solar radiation and Earth's magnetic field create breathtaking natural light shows in the polar skies.

Thus, the correct answer is Ionosphere, as it is the atmospheric layer where this interaction takes place.