Gifts of Nature:
AURORAS
Only the luckiest of people have gotten a chance to see nature’s gift to mankind that is the auroras. The name ‘aurora’ can be traced back to the Roman goddess of dawn, Aurora, and many other legends of civilizations in ancient history when the science behind the auroras was not fully understood [1]. To name just a few, the Aborigines thought that auroras were the dances of the gods, the Sámi natives of Scandinavia thought that the auroras had the power to resolve conflicts, and the Algonquin native American tribes saw auroras as a reminder from their creator god, Nanahbozho, telling them that he did not forget about them. Numerous other tales of early civilizations made attempts to explain these mysterious lights that were visible in the night sky. Now, the mystery behind these phenomenons can be fully understood. The auroras are beautiful curtain-like light displays that look as if they are being projected into the sky with a three dimensional effect. Unlike the technology we use today to create aesthetic pleasure, however, auroras are one hundred percent natural. So now several questions can be posed pertaining to this phenomenon: what really causes the sky to light up in different colors, what determines the auroras’ brilliant color display, how do the auroras affect the environment, and how can someone view this spectacle? There are two kinds of auroras: aurora borealis (Northern Lights) and aurora australis, (Southern Lights), which occur in the Arctic and Antarctic regions respectively. There are two concepts of science that can explain how these auroras form. First, there is the science behind the outer level of interaction between the KRISTINE PAIK/GRAPHIC Sun and Earth particles. Both types of auroras are caused by collisions between energized gas particles from the Earth’s atmosphere, and charged particles, mostly composed of electrons and protons, released by the Sun [3]. The charged particles are carried to the Earth from the Sun through a solar wind, which is a stream of charged particles ejected by the sun’s magnetic field at an extremely high speed. As the solar wind nears the Earth, it is obstructed by the magnetic field, so the wind splits in half and travels towards the poles. After entering the Earth’s atmosphere at the polar regions, the solar wind’s charged particles interact with the gas particles in the Earth’s atmosphere [2]. Second, there is a science behind the primary level of interaction, which occurs within the atoms themselves. When the charged particles from the sun collide with the gas particles from the Earth’s atmosphere, the electrons in the gas particles get very excited as their energy increases. This is because some of the energy from the particles, which are in motion, transfers to the electrons during the collision [4]. As these electrons return to their original energy levels after they lose the energy they gained, they emit visible light, which in turn joins the light emissions of other electrons and combines to form the auroras. Since the auroras are a result of the particles carried to Earth by the solar wind, it is actually a possibility that other planets in our solar system have auroras; this would depend on whether or not they lay in the path of the solar wind and have dense enough atmospheres with gas particles that could 4 | JOURNYS | FALL 2012
Written by Harshita Nadimpalli Edited by Daniella Park, Reviewed by Dr. Jim Kadonaga
react with the charged particles from the Sun. In fact, NASA has picked up activity on Saturn and Jupiter that is very likely a form of aurora [2]. The auroras put on a light show with numerous colors, the most commonly seen being a pale yellow-green. Auroras can be a single color, or have a multitude of colors like green, red, blue, or purple, depending on the collisions of the particles and the altitude at which they collide. The difference in colors is explained by the fact that different gas particles emit different colors of light when they are in the excited state [5]. Green and red light is caused when the sun’s particles collide with oxygen atoms. However, green light is formed up to 150 miles in altitude, whereas red light is formed above that. On the other hand, blue and purple light is formed when the sun’s particles collide with nitrogen atoms; blue light is formed up to 60 miles in altitude, while purple light is formed above that [6]. In addition, the bottom edge of an aurora is usually around 60 miles high, and as the intensity of an aurora increases, its distance from the ground decreases (so a very intense aurora might be as low as 50 miles) [3]. Not much research has been conducted regarding whether the auroras have long-term effects on the environment or not, but it is generally known that the auroras mostly affect the higher altitudes in which they take place and/or the ground directly below where they occur. Although some ionization of the areas directly below the aurora can interfere with radio waves, the effects of auroras are mostly limited to convective currents between the magnetosphere and ionosphere, near or inside the aurora. Sometimes the changes in temperature can also cause stronger winds [3]. Other than that, auroras provide a brilliant display in the skies without disturbance. For the readers who are already planning vacations to the colder regions of the Earth to see auroras, here are a few tips. Aurora activity tends to be higher and more evident when the solar winds are higher (since the solar winds carry the charged particles necessary for the auroras to occur); although there is always at least a faint trace of aurora activity some place on the Earth. In addition, trips should be planned to destinations such as Alaska, Canada, Siberia, Greenland, and Scandinavia during the winter season, because aurora sightings are more likely in these locations [7]. Once there, one should look for the aurora in a clear, dark sky, which can be anytime throughout the day; however, the best time to spot an aurora display is around midnight, when it is completely dark [1]. Pictures of auroras are great, but seeing one in person is a breathtaking and unforgettable experience. 1. “Northern Lights.” http://www.northernlightscentre.ca/northernlights.html 2. “Auroras.” http://www.webexhibits.org/causesofcolor/4B.html. 3. “Frequently Asked Questions about Aurora and Answers.” http://odin.gi.alaska.edu/ FAQ/ (2012). 4. “Two Ways to Excite Electrons Into High Energy States.” http://www.ehow.com/ info_8508063_2-electrons-high-energy-states.html (2011). 5. “Colored by the Atmosphere.” http://www2.gi.alaska.edu/asahi/color.htm (2003). 6. “How Does the Aurora Borealis (the Northern Lights) Work?” http://science.howstuffworks.com/nature/climateweather/atmospheric/question471.htm (2000). 7. “Auroras: Paintings in the Sky.” http://www.exploratorium.edu/learning_studio/auroras/seethem.html (2001).