What is Northern Lights and how is it caused? - WorldOfChemicals

Chemistry of Northern Lights

Northern Lights

An aurora is a natural light phenomenon, which occurs in the high latitude regions of the two poles. They are known as northern lights or aurora borealis around the arctic circle. On the other hand, they are known as southern lights or aurora australis around the Antarctic circle. 


How does this phenomenon occur?

The sun is situated approximately 150 million kilometres away from our planet. However, its effects are felt much beyond its visible surface. When storms occur on the sun, strong solar winds move across space. These solar winds react with our planet's magnetic field in a region known as the magnetosphere, where the fast-moving particles or electrons originate. These solar charged molecules, strike oxygen and nitrogen atoms present in the earth's atmosphere. This results in the lighting up of atoms due to their excitation.


What is excitation of an atom?

In chemistry, atoms constitute a central nucleus with a group of electrons encircling it in an orbit. When oxygen and nitrogen atoms in earth's atmosphere are struck by the charged particles from the sun, electrons move from a lower energy state to a higher energy state. In other words, the electrons move away from the central nucleus to higher energy orbits. Finally, when an electron moves back to a lower energy state or orbit, it results in the liberation of a photon or a light particle.



Northern lights and southern lights are mostly pale green and pink in color. Shades of green, blue, yellow, red and violet have also been reported. The shimmering lights appear in various forms such as scattered clouds of light, patches, arcs, streamers, rippling curtains and shooting rays, which light up the night sky with an eerie glow.


The colors emitted from elements can be classified as follows: 

1. Oxygen: Green and brownish-red colored lights in the aurora are due to oxygen. These colors are emitted due to the excitation of oxygen molecules. 

2. Nitrogen: The excitation of Nitrogen molecules results in the emission of blue and red colored lights.

3. Other Gases: There are other gases that get excited and emit light in the atmosphere. However, their wavelengths may not fall in the visible electromagnetic spectrum. Helium and hydrogen emit purple and blue colored lights.


Aurora on Other Planets

Auroras have been observed on other planets like Jupiter, Saturn, Uranus and Neptune. However, they have different colors because of their different atmospheres. Northern lights are possible in planets and moons, where energetic particles are present in the atmosphere. A Planet with a magnetic field would have an oval-shaped aurora at both poles. Whereas, a planet without a magnetic field would have an irregular shaped aurora.



The mystery of northern lights is not so mysterious as it was before. According to chemistry, different gases in earth’s atmosphere emit different colors on excitation. Yet many travel thousands of miles to witness the spectacular light shows in the earth's atmosphere. Despite knowing the real reason for the phenomenon, it can still light up our imagination.

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