Aurora is an atmospheric phenomenon that occurs when electrically charged particles from the Sun hit gas atoms in the Earth’s atmosphere. The energy released during the collision creates a colorful light seen within the Earth’s polar areas.
How do auroras occur?
Auroras are most commonly seen around the aurora oval – a ring-shaped belt roughly 2,500 miles in diameter near the Earth’s magnetic poles. The aurora oval is asymmetrical and can be displaced by the solar wind. It also varies in size depending on the level of aurora activity.
Energy is released when electrically charged particles from the Sun collide with gas atoms in the Earth’s upper atmosphere. This energy is transferred to Oxygen and nitrogen atoms and molecules. And as the gases return to their normal state, they create small bursts of energy in the form of colorful light visible in the Earth’s polar regions. The glowing aurora comprises a billion individual collisions, lighting up Earth’s magnetic field.
Who discovered the aurora light?
Some prehistoric cave paintings may have shown auroras. The Cro-Magnon drawings, known as “Macaronis,” were made approximately 30,000 B.C. and have been speculated to be representations of the aurora. We can find the earliest written record of an aurora in the Chinese work from 2600 B.C. that narrates the birth of Huangdi, the Yellow Emperor. He was one of the five mythological emperors of ancient China portrayed as a cosmic ruler and the originator of the centralized state.
Aurora australis and Aurora borealis
Aurora activity can be found in both the Arctic and the Antarctic. The term “aurora borealis” was coined by Italian astronomer and scientist Galileo Galilei in 1619 A.D. The name “Aurora” refers to Aurora, the Roman goddess of dawn. The word “Borealis” is derived from Boreas, the Ancient Greek god of the north wind.
Auroras in the Earth’s southern hemisphere are referred to as “aurora australis” or “southern lights.”It is the same phenomenon, except in high southern latitudes. British explorer James Cook coined the word “aurora australis” after an expedition to the Antarctic Circle between 1772 and 1775. The term “Australis” is derived from the Latin word “Austra,” meaning “South.”
What produces the aurora’s many colors?
The charged particles from the Sun clash primarily with Oxygen and nitrogen atoms in the Earth’s atmosphere at varying heights, ranging from 50 to 400 miles (80 to 644 kilometers), resulting in various aurora colors. The colors of the aurora are determined by the following:
- The amount of energy the solar wind’s electrons have at the time of contact.
- The altitude at which the collision happens.
Low energy electrons colliding with Oxygen lower in the ionosphere (between around 62 miles and 186 miles) cause Oxygen to emit green or greenish-yellow light. Red light is produced by high-energy electrons interacting with Oxygen at higher altitudes in the ionosphere (above 180 miles). Nitrogen collisions usually produce blue or red light. Colors such as white, pinks, and purples can result from the mix of these colors. Similarly, the collisions result in ultraviolet light emission, invisible to the naked eye. However, it can be detected by special cameras on satellites.
How common are these aurora colors?
Green auroras are the most common since the Earth’s atmosphere features a lot of atomic Oxygen, and the human eyes are more sensitive to the green color. The purple and blue hues are also not apparent in the night sky. Blue and purple lights are more abundant at lower altitudes, so they’re usually spotted near the bottom of the aurora’s “curtains.” They are caused by molecular nitrogen in the Earth’s lower atmosphere. Blue lights can also be produced by sunlight in exceptional cases.
Where can you see the northern lights?
The northern lights can be seen in high northern latitudes, particularly those near the Arctic Circle’s center. They are often spotted in Alaska, especially in the Fairbanks area, located under the aurora oval.
Northern lights can also be seen in Iceland, Russia, Canada, some parts of the United States, Greenland’s high arctic tundra ecoregion, Sweden, Finnish Lapland, and Norway, particularly around Troms, a city in the country’s north at the center of the aurora oval at night. Due to its location, the Polar Night in Troms can last for at least six weeks, making the lights a lot more visible.
The aurora oval can be seen predominantly over the oceans around Antarctica in the southern hemisphere. It does, however, occasionally reach the distant reaches of New Zealand, Chile, Australia, and even South Africa and Argentina.
Do other planets have auroras?
Auroras have been discovered on several planets throughout the solar system. Although not all of these planets have magnetospheres, scientists have demonstrated that the interaction between the solar wind and the planet’s atmosphere can be sufficient to cause an aurora on planets with modest magnetic fields. Because each planet’s atmosphere is distinct, auroras appear differently on different planets. For instance;
The magnetic field of Jupiter is 20,000 times more powerful than Earth’s. Thus, the auroras on the giant planet are much brighter. However, Jupiter’s magnetic field is constantly bombarded by particles from its close-orbiting moon Io, apart from the solar wind. X-ray flares have been found in Jupiter’s auroras due to Io’s charged interactions with sulfur and oxygen ions with Jupiter’s magnetic field.
Venus lacks a potent magnetic field. It features a lot of carbon dioxide with a few traces of Oxygen and nitrogen atoms in its atmosphere. Hence, auroras on Venus are not bright enough to be seen from the planet’s surface but only from space.
As a result of the abundance of exciting types of hydrogen in Saturn‘s atmosphere, its auroras are red, pink, and purple, as seen by NASA’s Cassini spacecraft. It has auroras in the infrared and ultraviolet spectrum, invisible to the human eye.
On Mars, aurora activity is limited to places covered by remnants of the planet’s global magnetic field that the red planet is considered to have had in the past.
