There exists a phenomenon in which a bright blanket of light covers the sky at night. The typically dark night sky becomes aglow with various colors; it seems as if the heavens are draped with natural light rays. Such occurrence is called an aurora; one of the kinds of which is called the aurora borealis.
Auroras are incandescent displays of natural light that fill the sky, but is only capable of being viewed by the naked eye during nighttime (Akasofu 325; O’Dell). There are two kinds of auroral displays. One of them occurs in the Southern Hemisphere called the aurora australis, which is also known as the southern lights. On the other hand, there is the light display which occurs in the Northern Hemisphere called the northern lights, or most popularly known as the aurora borealis (Akasofu 325; O’Dell).
Auroras are most often seen in the far regions of the North and South (O’Dell). The general appearance of auroras resembles that of clouds, with its streaks and arches. There are times when the auroras are seen in motion; they suddenly glow and go grow brighter. These auroras occur above the surface of the earth, at an estimated 1,000 kilometers. The undermost part of the auroral spread is estimated to have a height of 100 kilometers, while its width measures around 300 kilometers or more (Akasofu 325). The entire scope of the aurora appears to have folds or pleats at the bottom. The aurora in its entirety also proceeds in two directions: the movement is directed either near the pole, or the equator (Akasofu 325).
The “auroral curtain,” as it is called, is visible along belts which surround the “geomagnetic poles” (Akasofu 325). The belts, which are oval in shape, have a radius which measures 2,200 kilometers. These belts may spread extensively in great distances from east to west, but from north to south its width is a mere one kilometer. The center of the oval leans more to the Earth’s dark side by 3° (Akasofu 325). This is the reason why the aurora borealis is most often seen at midnight; it is also seen up north in a circle which includes the central Alaska, the coast of Siberia near the Arctic Ocean, the northern edge of the peninsula in Scandinavia, Iceland, Greenland, and the Southern part of the Hudson Bay (Akasofu 325).
The reason behind the occurrence of the aurora borealis is the processes regarding the electrical charges that occur in the Earth’s surroundings (Akasofu 325). The process begins with the heightened period in the 11-year cycle of the sun. To begin with, the temperature of the surface of the sun is about 6,000 °C (Pettersen 3). However, in the corona or the atmosphere of the sun, the temperature continues to increase with a million degrees. During this time, dark colored patches are produced on the surface of the sun; these patches are called sunspots (O’Dell). These sunspots would soon multiply and be active, causing intense eruptions (O’Dell; Pettersen 3).
These eruptions, called solar flares, are characterized by the collision of particles which result in the breakdown of atoms into electrons and nuclei. These solar flares emit what is called plasma; plasma is the group of electrons and protons which come from the disintegrated atoms of the solar flares. The plasma will then travel from the corona through an opening in the magnetic field of the sun (Pettersen 3). As the plasma leaves the corona, it is immersed in a spiral as the sun turns. This is referred to as the “garden-hose effect,” a phrase coined from the pattern created by the water from the rotation of the hose (Pettersen 3).
The plasma contributes to the amount of solar particles that reach the atmosphere of the earth (O’Dell; Pettersen 4). These particles are known as the solar wind, which is the constant drift of particles derived from the sun (O’Dell). The plasma would then touch the magnetic field of the Earth through compression of the “daylight” side, and reaches it by the “tail” on the night side (Pettersen 4). When the said particles have reached the magnetic field of the Earth, there can be two outcomes.
On one hand, the particles can be trapped. On the other hand, it can move towards the magnetic poles. Those particles are able to reach the Earth through the “tail” (Pettersen 4). This “tail” serves as a tunnel; it is a cylinder with a diameter and length which are, individually, significantly larger than the radius of the Earth (Pettersen 4). The Earth is at the end of this tunnel, and in its surrounding is where the solar wind and the magnetism of the Earth meet. That interaction hit the molecules and atoms from the atmosphere. As a result, energy is discharged. This energy is responsible for the appearance of the aurora borealis (O’Dell).
In the case of the aurora borealis, the conversion of energy into light is made possible by quantum leap (Pettersen 6). To better explain what quantum leap is, a hydrogen atom should be used as an example. The hydrogen atom in question is composed of one positively charged proton nucleus; at a distance, one electron revolves around this nucleus. Nonetheless, it is also possible that the orbit of the electron can be at a much greater distance from the nucleus. When an electron quickly strikes another hydrogen electron, energy is emitted. It also causes the spinning electron to transfer in another orbit not only with more energy but also with more distance from the nucleus. Usually, when the electron is in close proximity with the proton, the hydrogen atom has less energy.
In this case, it contains more energy; however, it is not stable and has no capacity to maintain the energy acquired. As a result, while the electron resumes its primary orbit, the excess energy is emitted as a light photon. The simultaneous quantum leaps are responsible for the creation of the aurora borealis (Pettersen 6).
However, quantum leaps in hydrogen atoms are only partly responsible for the existence of the aurora borealis (Pettersen 6). The most prominent color of the aurora borealis is green (O’Dell). The green color is caused by oxygen quantum leaps (Akasofu 325; O’Dell). Other colors in the aurora borealis include red, yellow, purple, and pink (Akasofu 325). Red and yellow are produced by molecules of oxygen, while the color purple is caused by nitrogen atoms. Lastly, the molecules of nitrogen are responsible for the pink color (Akasofu 325).
Indeed, there are many processes that work behind the creation of the aurora borealis. This magnificent showcase of light is one of nature’s best displays, much more remarkable than any man made light show ever created.
Works Cited
- Akasofu, Syun-Ichi. “Auroras.” Lexicon Universal Encyclopedia. 21 vols. New York: Lexicon Publications, 1992.
- O’Dell, C. Robert. “Aurora.” National Aeronautic and Space Administration. 29 Nov. 2007. 19 May 2008 <http://www.nasa.gov/worldbook/aurora_worldbook.html>.
- Pettersen, Franck. Aurora Borealis-the northern lights. 10 Sept. 1996. 19 May 2008 <http://www.imv.uit.no/english/science/publicat/waynorth/wn1/contents.htm>.
