What are Aurora Borealis and Aurora Australis and do they match?

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northern and southern lights

What is an Aurora and the science behind its formation?

An Aurora is a natural light that shimmers in Earth’s sky, mainly seen in high-latitude and lower polar regions (i.e. around the Arctic and Antarctic). They are only visible at night. An aurora is also referred to as Northern lights (Aurora Borealis), Southern lights (Aurora Australis), and Polar lights (Aurora Polaris).

Auroras occur due to the disturbances in the magnetosphere caused by the solar wind. The activity which creates auroras begins on the sun. The sun is called the ball of superhot gases which is made up of electrically charged particles called ions. The ions which continuously stream from the surface of the sun are called the solar wind. As the solar wind approaches the Earth, it meets the magnetic field of the earth. Without this magnetic field, the solar wind would blow away the Earth’s fragile atmosphere.

As the magnetosphere blocks most of the solar wind, some of the ions get trapped in ring-shaped holding areas around the planet. These areas where ions revolve around the planet in an atmosphere called the ionosphere are centered around the Earth’s geomagnetic poles. In the ionosphere, the ions of the solar wind collide with atoms of nitrogen and oxygen from the Earth’s atmosphere. The energy released during the collisions causes a colorful glowing halo around the poles—an aurora.

Note – The most active auroras are formed when the solar wind is the strongest. The solar wind usually remains constant, but solar weather i.e. the cooling and heating of different parts of the sun change daily.

The increased activity and regular fluctuations in the solar wind are known as magnetic storms. Magnetic storms can lead to auroras being seen in the midlatitudes regions during the time around the autumn and spring equinoxes. Magnetic storms and active auroras interfere with the communication process. They can disrupt radio and radar signals. Communication Satellites are also disabled by the intense magnetic storm

The colors of the aurora changes, depending upon the altitude and the kind of atoms involved in it during the collision. If ions strike against oxygen atoms high in the atmosphere, the interaction produces a red glow light. This is an unusual aurora, the most familiar display, a green-yellow color light, occurs as ions strike against oxygen at lower altitudes. Reddish and bluish light which often appears in the lower fringes of auroras is produced by ions striking against atoms of nitrogen. Ions striking against hydrogen and helium atoms produce blue and purple auroras, although our eyes rarely detect this part of the electromagnetic spectrum.

What is an Aurora Borealis or Northern Lights?

Aurora borealis or Northern lights of the northern hemisphere are also called the ‘dawn of the north’. The lights which are seen above the magnetic poles of the northern hemisphere are called Northern lights or Aurora Borealis.

aurora borealis
Aurora Borealis

The Northern Lights are formed as a result of collisions between charged particles released from the sun and gaseous particles in the Earth’s atmosphere. Colour variations are found due to the type and nature of gas particles that are colliding. The most common auroral color is a pale yellowish-greenish light that is produced above 60 miles from the Earth due to oxygen atoms while all-red auroras are formed at a height of up to 200 miles due to high – altitude oxygen atoms. Nitrogen produces blue and purplish-red aurora.

The places where Northern lights are seen

  • Tasmania and New Zealand
  • Iceland
  • Greenland, Alaska
  • Yellow Knife, Canada
  • Tromso, Norway
  • Northern Sweden
  • Finland

What is an Aurora Australis or Southern Lights?

Aurora Australis or Southern Light is a natural light that occurs in Earth’s atmosphere above the Southern Ocean and Antarctica. It is a fluorescent green ring of light above the Earth which becomes visible during the interaction between the solar wind and Earth’s magnetic field.

aurora australis
Aurora Australis, By NASA Astronaut photograph from ISS – Public Domain

Southern Lights are produced when electrons traveling from the Sun collide against the gas molecules in the upper parts of Earth’s atmosphere. As the electrons reach the Earth, they descend towards the ground following the attraction of the magnetic field of the Earth. As they pass through the atmosphere, they collide against nitrogen and oxygen molecules, dislodging electrons in the molecules and exciting them to higher energy levels. When those dislodged electrons fall back to the ground state of orbitals, they emit a small amount of energy in the form of light. This release of light is called fluorescence and is very similar to the light released by fluorescent minerals.

The Southern lights look like a glittering curtain of scintillating light across the night sky for the observers on the ground. If you are observing the southern lights from a far distance apart, they look like a fluorescent glow across the horizon. If you are observing the southern lights from below, they often look like curtains of light descending towards the ground.

The places where Southern Lights are seen

  • The Falkland Islands
  • Patagonia, Chile & Argentina
  • South Georgia Island
  • Antarctica
  • Bruny& Satellite Islands, Tasmania, Australia
  • South Arm Peninsula, Tasmania, Australia
  • Queenstown, New Zealand
  • Hobart, Tasmania
  • Mount Nelson, Tasmania, Australia
  • Stewart Island, New Zealand
  • Victoria, Australia

Do Aurora Borealis and Aurora Australis match with each other?

The northern lights and the southern lights, i.e. aurora borealis and aurora australis, respectively, display the light in the sky in hazy green and red color near Earth’s polar regions. The two phenomena are not identical.

The Magnetic field of the Earth where charged particles flow links the north and south poles, it made sense to assume that the atmospheric displays in each hemisphere would mirror each other. Advancement in Earth imaging technology repealed the way of thinking in approx. 2009 when scientists observed simultaneous auroras drifting across the poles in patterns that didn’t match up. But the reason is still unknown.

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