If you ever have a chance to visit the North or South Pole, don’t miss it because you are in for a special treat. A spectacular view of beautiful lights is frequently shown in the sky. These lights are known as Aurora. The Northern lights are called Aurora Borealis and the Southern lights are called Aurora Australis.


How Auroras are formed?

Let’s take a journey to the polar lights. These lights are formed when high-energy particles from the sun collide with neutral atoms in the atmosphere. Approximately one million tons of matter per second is blasted from the sun at the speed of one million miles per hour and it’s directed towards the Earth.

(Don’t worry we are fine)

When these high-energy particles crash into the atmosphere of Earth, an amazing phenomenon is produced. So is it as simple as that? The answer is NO. Let’s dive into it by focusing on three main points of this intergalactic journey:

1)      Particles leaving the sun’s surface,

2)      Making a pit stop at the Earth’s magnetic field,

3)      And finally arriving at the atmosphere above our heads.

The outermost layer of the sun’s atmosphere is known as corona, it is one of the hottest regions. Sun’s corona ejects high-energy protons and electrons, they interact with our atmosphere producing Northern lights. The extreme heat increases the kinetic energy of hydrogen and helium atoms in the sun, due to which they vibrate violently and strip off protons and electrons. These free protons and electrons are so fast that they escape the sun’s gravity and group together in the form of plasma, an electrically charged gas. Together they travel away from the sun as the constant gale of plasma, known as the solar wind. However, our planet is quite unwelcoming towards them. So the Earth prevents these solar winds from traveling straight into the planet by setting up a detour, the magnetosphere.

The magnetosphere is formed by the Earth’s magnetic currents and shields the Earth from solar winds by sending out the particles around our planet. Their opportunity to continue the journey down to the atmosphere comes when the magnetosphere is overwhelmed by the new wave of particles. This event is known as coronal mass ejection, and it occurs when the sun ejects a massive ball of plasma into the solar wind. When one of these coronal mass ejections collides with Earth, it overpowers the magnetosphere and created a magnetic storm. The intense storm strains the magnetosphere to the point where it snaps back, like an overstretched elastic band, flinging some of the detoured particles toward Earth. The magnetic field's retracting band drags them down to the aurora ovals, which are the locations of the northern and southern lights.

The Sun's particles have traveled 93 million miles across the galaxy to finally produce their stunning light show. The oxygen and nitrogen atoms interact with electrons and protons 20 to 200 miles above the Earth’s surface, and they are thrilled to see each other. The sun’s particles give their energy to the Earth’s neutral oxygen and nitrogen atoms. When the atoms in the atmosphere receive this energy they get excited, and then they emit photons after de-excitation. Photons are small bundles or packets of energy, they are the quanta of electromagnetic radiation.

The colors that appear in the sky depend upon the wavelength of the photons emitted by the atoms. Green and red hues are caused by excited oxygen atoms, while blue and deep red hues are caused by excited nitrogen atoms. The northern and southern lights are the result of a collection of these interactions.

Which time is best to see Aurora?

The polar lights are best seen on clear nights in regions close to the magnetic north and south poles. Nighttime is ideal because the Aurora is much dimmer than sunlight and cannot be seen in the daytime. Remember to look up at the sky and learn about the Sun's energy patterns, particularly sunspots and solar flares, as these can help you predict the auroras.

The Appearance of an Aurora

Streams of colorful light appear as reds, greens, yellows, pinks, and purples during the luminous phenomenon of an aurora. Most spectacular displays fall into one of three categories. In the first form, a homogeneous band or arc of light rises from east to west across the lower part of the sky, reaching within a few degrees of the horizon. This band could be only 100 m thick. Rays stream up vertically from the arc or band-like fringes on fine fabric in the second form, following the lines of the Earth's magnetic field. In the third form, the corona appears when the aurora is directly above you and rays appear to fall around you from the zenith of the sky. Depending on the composition of the atmosphere, a single auroral display may include a variety of these forms and colors. Auroral arcs can stand almost still, then begin to dance and turn as if a hand has been run along a long curtain. After midnight, the aurora can appear patchy, with the patches frequently blinking on and off once every 10 seconds or so until dawn.

Auroras are generally visible at altitudes between 100 and 500 kilometers because they originate in an atmospheric layer high above the Earth's surface. They are most frequently seen in the auroral ovals, which are two rough circles with a diameter of about 3000 km centered on the Earth's magnetic poles. These high-density aurora circles are located between 60° and 70° north and south latitudes, roughly in line with the Arctic and Antarctic circles. When high solar activity (such as sunspots) disturbs the Earth's magnetosphere, the size of the auroral ovals grows.

Auroras on other planets

Auroras can occur on other planets as well; all that is needed is an atmosphere and a magnetic field. Any planet in the path of the solar wind that has a sufficiently dense atmosphere will have auroras. Any planet in the path of the solar wind that has a sufficiently dense atmosphere will have auroras. Venus has no magnetic field and thus has irregularly shaped auroras, whereas planets with magnetic axes that are very different from their rotational axes have severely distorted auroral ovals.

Auroras have been photographed on Saturn, Jupiter, and even some of these planets' moons. Because our moon lacks the necessary atmosphere, it does not have an aurora. The same phenomenon is likely to occur on planets in other planetary systems. An aurora is produced when a planet with a dense enough atmosphere is bombarded by high-energy particles emitted by the star at the system's center.

History of Aurora

The aurora borealis has been mentioned throughout history, even in Stone Age cave paintings dating back 30,000 years. Aristotle described the aurora in his book Meteorology, written over 2,000 years ago.

However, prior to the Chinese passage, the northern lights were first recorded around 679-655 B.C. On cuneiform tablets, Assyrian astronomers recorded an aurora event. According to some scholars, biblical accounts of the Hebrew prophet Ezekiel described a vision that resembled the northern lights. In 567 B.C., Babylonian King Nebuchadnezzar II recorded an aurora in his astronomical diary. Even in A.D. 34, Roman Emperor Tiberius Caesar sent men to the Italian town of Ostia, believing it was on fire. Instead, the aurora borealis glowed overhead.

However, it was not until 1619 that Galileo Galilei coined the term "aurora borealis." The Greeks believed Aurora was the sister of Helios and Selene, and her name was derived from the Greek words
"aurora" meaning "sunrise" and "boreas" meaning "wind." Helios represented the sun. Selene represented the moon. Aurora was the one who raced her colorful chariot across the sky to wake her siblings up at the start of each day.

In 1790, Henry Cavendish made the first scientific observations of the northern lights. The French-born English scientist determined the aurora borealis occurred approximately 60 miles above the Earth's surface using triangulation. The aurora borealis was first linked to the sun by British astronomer Richard Carrington in 1859.

Even though Norwegian scientist Kristian Birkeland was the first to explain what caused the northern lights in the early 1900s, Benjamin Franklin had a theory on a ship sailing across the Atlantic. The lights were caused by a concentration of electrical charges at the North Pole, which was exacerbated by snow and moisture.

From cave people to the King of China, Roman emperors to our founding fathers, humankind has long gazed up at the aurora borealis in awe and documented evidence of it.