The Northern Lights is noted as one of the most spectacular and unique attractions of the Arctic Circle. Every winter, hordes of tourists flock to the Arctic to witness auroras lighting up the night sky in a breathtaking array of colors. While the science of the Northern Lights has become better known in recent years, many potential tourists are unaware of the particulars of how the Northern Lights are created. One thing that can be said is that the Earth’s magnetosphere is vital in the creation of auroras.
The Northern Lights are created by interactions between the Earth and the sun, specifically by Earth’s magnetosphere. Read on to learn about the magnetosphere and its importance to life on Earth.
The Magnetosphere and the Northern Lights
The magnetosphere is a protective bubble around the Earth generated by the planet’s magnetic field. While space might seem empty, it is full of cosmic radiation and other particles that are harmful to life. The magnetosphere deflects or neutralizes cosmic radiation, protecting the Earth and allowing humans and other forms of life to exist on its surface.
One particular type of cosmic radiation is solar wind, a term used for the particles that are emitted by the sun on a constant basis. While most know the sun as creating light and allowing plants to grow and animals to live, solar wind is actively harmful to life. Solar wind is regularly deflected by the magnetosphere along with other types of radiation.
What does this have to do with the Northern Lights? When solar wind impacts the portions of the magnetosphere that are located within Earth’s atmosphere, it comes into contact with air particles. All matter is comprised of atoms, which are made up of protons (which carry a positive electrical charge), neutrons (which carry no charge), and electrons (which carry a negative charge). Protons and neutrons are located in the nucleus, which is the center of the atom, while electrons orbit around the nucleus in a manner similar to how the moon revolves around Earth or Earth revolves around the sun.
When charged particles emitted by the sun come into contact with the atmosphere, the resultant reaction excites the air particles, causing electrons to move into higher-energy orbits further away from the nucleus. When those atoms cease to be excited, the electrons move back to their original orbits, giving off photons (particles of light) in the process. When this happens on a large scale as a result of solar wind, the resultant effect is visible as an aurora. This chemical reaction is common in nature and is also used by some modern technology. For example, neon signs work by using electricity to excite neon atoms, who in turn produce light.
The reason why the Northern Lights is most commonly seen in the Arctic Circle is because this process can only occur where the magnetosphere intersects with the atmosphere. The magnetosphere is generated by the Earth’s magnetic field, which emanates from the North and South Poles. Much of the magnetosphere extends into space, with the North and South Poles being the only areas where it intersects with the Earth itself.
While solar wind hits all areas of the Earth, it is deflected by the magnetosphere and can only travel along magnetic field lines, lines of force that originate at the poles and connect them to each other. Outside of the poles, magnetic field lines extend into space, meaning that the North and South Poles are the only areas where sufficient solar wind enters the atmosphere to cause a reaction and create auroras. This is why the Northern Lights can generally only be seen outside the North and South Poles during periods of exceptionally high solar activity.
The only time that auroras can be seen outside the geographic North and South Poles is during a period of magnetic reversal, when the magnetic North and South Poles switch positions. This occurs roughly every 450,000 years, though according to scientists, the most recent magnetic reversal occurred 780,000 years ago. During this period, the poles shift position, with the North Pole heading south and the South Pole heading north. Since the magnetosphere converges with the atmosphere at the poles, this means that it will be possible to see auroras as the poles move across other parts of the Earth.
The exact color of the Northern Lights is determined by the distance at which solar wind penetrates the atmosphere before being dissipated by the magnetosphere. The most common aurora colors are blue and green, created by reactions with nitrogen and oxygen particles in the lower atmosphere, respectively. Red auroras can also sometimes be witnessed due to solar wind in the outermost reaches of the atmosphere, but due to the lack of air particles at this height, they are rare.
The magnetosphere plays a vital role in not only creating the Northern Lights, but in safeguarding life on Earth. Without the magnetosphere, not only would auroras not occur, but Earth would be inhospitable due to constant bombardment from cosmic radiation. Thanks to the Earth’s magnetic fields, visitors to the Arctic can be treated to the Northern Lights, a visual reminder of the magnetosphere’s existence and one of the most memorable natural sights in the world.