Abstract: The purpose of this article is to give information about Northern lights (Aurora borealis) and Southern lights (Aurora australis). Northern and Southern lights are also known as aurora borealis and aurora australis in order. Aurora’s form because of solar wind that hits Earth’s magnetic shield. Those lights glow in different colors because the solar wind hits variety of gasses every time. Auroras do not only happen on Earth, in other planets, like Jupiter, it also appears. The difference between Northern and Southern lights is that they appear in different hemi circles, but the fame of Northern lights is bigger than the Southern lights. The best place to view Auroras in North hemisphere is Alaska, Canada, Iceland, and Scandinavia. In South hemisphere Antarctica, New Zealand, and Tasmania are the best places to watch the Aurora australis. There is lot of people who learned Auroras, for instance: Aristotle, William Gilbert, and Anders Celsius.

Key words: aurora australis, aurora borealis, magnetic shield, heliosphere, solar wind, excite, ionosphere, ion, Arctic circle.

Introduction: Aurora- the term comes from Italian astronomer Galieo Galilei, naming after the Roman goddess of dawn in year 1619. Mistaking it for the reflection of sunlight off the atmosphere.
Auroras are the glowing lights that happen at the North and the South hemisphere of the Earth.[1]

The heliosphere and solar wind

Just like the Earth, Sun has a magnetic shield. The Sun’s magnetic shield is called heliosphere and it fills the solar system. The Sun radiates its energy throughout the heliosphere. Planets and other subjects in the solar system gets this radiation as a form of charged particles and magnetic fields. This stream of fields and particles are called the solar wind.
It all starts when the solar wind hits the Earth.

Forming of Auroras
When that solar wind reaches to the Earth’s atmosphere it makes contact with the magnetic shield, then currents of charged particles that flow toward the poles. Some of those many ions become trapped in a layer of atmosphere, which is ionosphere. There ions collide with gas atoms- mainly nitrogen and oxygen- and “excite’’ them with more than enough energy. It gets released and causes light (also known as photon).
That interaction happens in oval-shaped zones that covers Earth’s magnetic polars and puts more or less fixed orientation. During periods of low solar activity, the auroral zones shift poleward. During periods of intense solar activity, auroras occasionally extend to the middle latitudes; for instance, the aurora borealis has been seen as far south as 40° latitude in the United States. Auroral emissions normally happen at altitudes of about 100 km (60 miles); however, they may occur anywhere between 80 and 250 km (about 50 to 155 miles) above Earth’s surface.

Why are Auroras colorful?
Auroras appear in different colors such as pink, blue, green, and purple. It happens because the particles hit different gasses and in different atmosphere locations. Primary it hits oxygen and nitrogen.
Oxygen excited to varying energy levels can produce green and red. Green occurs roughly between 60 to 120 miles (100-200 km) altitude, and red occurs above 120 miles (200 km).
Excited nitrogen gas from about 60 to 120 miles (100-200 km) glows blue. Since the type and energy of the particle differs it interacting with, nitrogen can give off both pink and blue light. When it is below about 60 miles (100 km), it gives the lower edge of the aurora a reddish-purple to pink glow.
Sometimes auroras can be even white because the gasses emitted gets mixed.[2]

The difference between Northern lights and Southern lights
Aurora borealis happen in the Northern hemisphere, around the Arctic circle. Aurora australis happen in the Southern hemisphere, around the Antarctic circle. Both phenomena happen because of the same process of solar wind affecting Earth’s magnetic shield.
While both Aurora borealis and Aurora australis are breathtakingly beautiful, the Aurora borealis is well-known and well-observed than the Aurora australis, due to the large population in the Northern hemisphere.

 
Earth's full North Polar auroral oval, in an image taken in ultraviolet light by the U.S. Polar spacecraft over northern Canada, April 6, 1996. In the color-coded image, which simultaneously shows dayside and nightside auroral activity, the most intense levels of activity are red, and the lowest levels are blue. Polar, launched in February 1996, was designed to further scientists' understanding of how plasma energy contained in the solar wind interacts with Earth's magnetosphere. [3]

Where to observe the Auroras
To see Auroras in person there are some places they might appear. In the Northern Hemisphere, famous locations are Alaska, Canada, Iceland, and Scandinavia. In the Southern Hemisphere, the best places to view the Aurora Australis are in Antarctica, New Zealand, and Tasmania.
To make the chance of seeing auroras bigger, it is advised to go there in the winter when nights are longer and darker compared to other seasons. It is also important to check local weather forecasts.[4]

Do other planets experience Auroras?
Auroras have been observed on Jupiter, Saturn, and Uranus, but not on Mars, Venus, or Mercury. Any planet with a magnetic shield and an atmosphere should likely have auroras (Mars and Venus have no global magnetosphere; Mercury has almost no atmosphere). Since an aurora indicates the presence of an atmosphere, we might be able use the presence of auroras to and planets beyond our solar system that could support life. [5]

Does the Aurora make sounds?
Observers have heard crackling, hissing or swishing sounds for years. But the scientific experiments were unable to notice any sound and they cannot find a reason why light should make sound. The air in the upper part of atmosphere is too thin to make sound hearable. If you have heard any sound while watching an Aurora it must be because of the other things.

Who has helped us learn them?
Some of the brightest minds in history have puzzled over the aurora. In the 4th century B.C. Aristotle made one of the first truly scientific accounts of the aurora borealis, describing “glowing clouds” and a light that resembled fames of burning gas. The real advances in auroral science began when scientists started connecting auroras to magnetism. In the late 16th century, William Gilbert conducted experiments that led him to propose that the Earth itself was a giant magnet, with a North and South Pole as if a great bar magnet had been buried inside. In the 17th century Anders Celsius proposed that the lights were caused by moonlight reflected by ice and water in the air. Rene Descartes (France) and other scientists asserted that the refraction of moonlight and the reflection of colored rays by ice crystals in the atmosphere somehow caused the aurora. Some of these misconceptions survive even today. In 1739, a London watchmaker, George Graham, noticed that on some days, a compass needle made irregular motions from true north that he could not explain. That same year in Sweden, Anders Celsius detected the same phenomenon and noted that it seemed to occur when auroras danced in the sky. Benjamin Franklin wrongly attributed the lights to a sort of lightning or electric discharge from clouds above the polar regions. An important discovery of the link between solar activity and the aurora occurred in England in 1859 when astronomer Richard Carrington and amateur sun-watcher Richard Hodgson independently noticed bright patches of white light coming from around some sunspots. These were the first reported observations of a solar flare. About 18 hours after the flare, the magnetic instruments at the Kew Observatory in London measured large variations in the Earth’s magnetic shield. Across the Atlantic, Elias Loomis, a Yale professor, noted a day later that the auroral light show was “one of the most remarkable ever recorded in the United States.” It wasn’t until the late 1800s and early 1900s that spectroscopic measurements of auroral light identified oxygen and nitrogen as the color sources for the aurora. A Finnish oil painting of the aurora Around the turn of the 20th century, Norwegian physicist Kris tian Birkeland revived Gilbert’s experiments. He placed a spherical magnet inside a vacuum chamber and shot an electron beam at it. He found that the beam was guided by the magnetic shield to hit the sphere near the poles. He reasoned that the Sun must shoot beams of corpuscles (now called electrons) toward Earth, where the planet’s magnetic shield guides them in near the Poles. His view of the aurora was close to the truth, except that the corpuscles originate in our magnetosphere, not from the Sun. In the 1930s, Sydney Chapman and Vincent Ferraro proposed that clouds of electrically charged particles ejected from the Sun fly across empty space and envelope the Earth to cause auroras; we now call this mixture of electrons and protons plasma, the fourth state of matter. Since these clouds would be excellent conductors of electricity, they would generate currents and distort Earth’s magnetic field. Following the launch of the Sputnik satellites by the Soviet Birkeland in his lab testing his theories on what causes aurora Union and the Explorer satellites by the United States, centuries of scientific theories, remote observations and wild speculations were put to the test by first-hand observations. Scientists such as James Van Allen and Sergei Vernov discovered that the space around Earth was filled with high-energy particles, trapped by the Earth’s magnetic field into doughnut shaped rings around the Earth, called the radiation belts. Russian and American space probes proved the existence of the solar wind and a series of US satellites mapped out the shape of the magnetosphere. Satellites in the tail of the magnetosphere found it unstable, and low altitude polar satellites measured the electrons producing the aurora.[6]

Conclusion
In conclusion, one of the greatest phenomena is Auroras. While Northern lights are infamous, both Northern and Southern lights look awesome. It makes us feel nostalgia from long ago. It generally happens in Southern and Northern hemispheres, and visible to area near there. There have been and there will be lot of observation to learn these phenomena.

“And the skies of night were alive with light, with a throbbing, thrilling fame; Amber and rose and violet, opal and gold it came.
It swept the sky like a giant scythe, it quivered back to a wedge;
Argently bright, it cleft the night with a wavy golden edge.
Pennants of silver waved and streamed, lazy banners unfurled;
Sudden splendors of sabres gleamed, lightning javelins were hurled.
There in awe we crouched and saw with our wild, uplifted eyes
Charge and retire the hosts of fire in the battlefield of the skies.” — Robert Service, from “The Ballad of the Northern Lights,” published in 1908