Journey into the Unknown: Delving Into the World of Auroras
Auroras are a natural wonder that has captivated people for centuries. These magnificent lights dance in the night sky, creating a stunning display of colors and patterns. Many people have gazed at posters or wallpapers adorned with sparkling lights, wondering if they were real or just a product of photo editing. The truth is that auroras are a very real phenomenon and occur in both the Earth's atmosphere and outer space. This article will focus on the myths and superstitions associated with these lights and then delve into the scientific explanations behind their existence.
Myths and Superstitions
Long before the scientific revolution, people observed the phenomenon of the Aurora Borealis and developed a variety of myths and stories to explain it. Some believed it to be a sign of divine anger, war, and plague, evoking fear in their hearts. Ancient Canadians interpreted it as the dance of dead spirits, while the Sami people called it "guovssahas" - the light you can hear because it makes a crackling sound (Nikel, 2022). According to Norse mythology, people believed Auroras to be the rainbow bridge that connected the homes of gods and humans (Nikel, 2022.). These myths and legends demonstrate how the Aurora Borealis captivated the imaginations of people from different cultures and inspired a range of interpretations. In addition to the scientific understanding of this natural phenomenon, these stories serve as a reminder of the awe and wonder the aurora has inspired throughout human history.
What are Auroras and where are they?
Auroras, or Northern/Southern Lights, are a natural phenomenon caused by electrically charged particles from the Sun colliding with particles in the Earth's atmosphere. (Aurora Borealis (Northern Lights), n.d.)
The Aurora Borealis is visible in the northern hemisphere, primarily in regions close to the Arctic Circle such as Alaska, Canada, Norway, Sweden, Finland, and Iceland, while the Aurora Australis is visible in the southern hemisphere, primarily in regions close to the Antarctic Circle such as New Zealand, Tasmania, and Antarctica.
ORIGIN: Sun as the Master Behind this Interplay
In order to thoroughly grasp the concept one must understand the sun first.
The Sun, a yellow dwarf star composed of hydrogen and helium, is the largest object in our solar system, located 93 million miles away from Earth (NASA, n.d.). Despite its shiny appearance in the daytime sky, the temperature drops significantly to 10,000 °F (5,500 °C) as we look toward the Sun's surface. However, further out in the Sun's outer atmosphere, the corona, the temperature rises significantly to a staggering 3.5 million °F (2 million °C). This inexplicable phenomenon is still a mystery to scientists. The corona's extreme heat accompanies a fundamental force of nature, magnetic force, due to the energetic radiations and plasma at the Sun's surface.
The Sun's behavior is not constant and undergoes cycles every 11 years, with the peak of activity known as solar maximum. During this phase, the Sun releases violent solar flares that can interfere with satellites, GPS, and radio communication, and even cripple power grids on Earth. This solar activity, along with the accompanying energy, also plays a crucial role in the formation of auroras or the northern and southern lights (NASA, n.d.).
How it occurs: The Secret Connection between the Sun and Earth's Magnetic Fields
Image Credit: NASA
Earth also surrounds itself with a magnetic field, just like the Sun, but scientists have not yet confirmed its origin. Scientists have hypothesized that our planet acts like a magnet with north and south poles (Magnetic Field of the Earth, n.d.). When this solar wind interacts with the ions and atoms of oxygen and nitrogen from Earth's atmosphere in the ionosphere, these collisions excite the particles in the atmosphere, causing them to emit light in various colors. This collision results in a colorful, glowing halo around the poles. The color of the auroras depends on the type of gas particles that the charged particles collide with. For example, collisions with oxygen molecules in the upper atmosphere can produce green or red auroras, while collisions with nitrogen molecules can produce blue or purple auroras (Aurora, n.d.). Auroras are typically formed about 97-1,000 kilometers (60-620 miles) above the surface of the Earth. When directed at the poles of Earth, these flares then interact violently with the ions in Earth’s atmosphere and because of the interatomic interactions; light radiates outward creating exquisite patterns of shimmering and dancing glitters in the sky.
The Mastermind Behind this Explanation
Kristian Birkeland was a Norwegian scientist known for his pioneering research on the aurora borealis. He proposed that electric currents flowing in the Earth's atmosphere caused the auroras and that these currents were linked to the Sun. Birkeland's work on the aurora and plasma physics has influenced our understanding of the universe and laid the foundation for much of modern space science (Egeland, 2009).
Kristian Birkeland conducted the Terrella experiment in 1895 to demonstrate the phenomenon of geomagnetism. He later used an electromagnetic terrella to create an artificial Aurora around the poles of the terrella, replicating the effects of the solar wind on the magnetic Earth and attempting to simulate other cosmic phenomena. Birkeland used a magnetic sphere that represented Earth called Terrella, which was covered with a fluorescent substance. The sphere was placed in a vacuum chamber, and a beam of electrons was fired. Because of these electrons colliding with the Terrella, the light produced by the fluorescent substance showed that the electrons were being guided toward the magnetic poles of the sphere (The Museum of the History of Science, University of Oxford, n.d.).This experiment provided evidence for the theory of geomagnetism and the role of Earth's magnetic field in deflecting charged particles from the sun.
According to available sources, modern research confirms Birkeland's theories on the aurora and electrical currents in the atmosphere. Evidence includes measurements from NASA's Mariner II spacecraft in 1962, which detected electrified gas in space traveling at high speeds, and observations made by a US Navy navigation satellite in 1966, which recorded magnetic disturbances near the polar regions. These findings demonstrate that space is not empty, as previously believed, but filled with particles such as the solar wind and that electric currents do flow in the Earth's upper atmosphere. These discoveries support Birkeland's work. (Fahleson, 1967)
Below is a picture of Birkeland performing this experiment.
© Terrella. (2022, March 5). In Wikipedia. https://en.wikipedia.org/wiki/Terrella
One of the most significant impacts of auroras on technology is their potential to disrupt communications and power grids. The electric currents that create the aurora can interfere with radio signals and cause power outages in high-latitude regions. For example, in 1859, a massive solar storm caused widespread disruptions to telegraph systems, resulting in visible auroras in places where they would not normally be visible (NASA, n.d.). Today, the study of auroras and space weather is critical for predicting and mitigating these events.
Birkeland's work continues to influence space science research today. For example, the European Space Agency's Swarm mission uses a trio of satellites to measure the Earth's magnetic field and study electric currents in the ionosphere (European Space Agency, n.d.). The Swarm mission aims to provide detailed information about the Earth's magnetic field, which is crucial for understanding the Sun-Earth connection and space weather. Birkeland's research on the Earth's magnetic field and aurora borealis has directly influenced the mission by demonstrating the connection between the Sun and the Earth's magnetic field, which is the foundation for understanding the interaction between the Earth's magnetic field and the solar wind. (European Space Agency, n.d.)
In conclusion, the aurora borealis and the study of space physics have significant implications for technology and our understanding of the universe. Kristian Birkeland and subsequent studies of auroras played a crucial role in advancing our knowledge of these phenomena, laying the foundation for modern plasma physics and inspiring further research into space weather and its impacts on technology.
Works Cited
National Aeronautics and Space Administration. (n.d.). Sun In Depth. Solar System Exploration. Retrieved from https://solarsystem.nasa.gov/solar-system/sun/in-depth/
Nikel, D. (2022, March 28). Myths And Legends About The Northern Lights. Forbes. Retrieved from https://www.forbes.com/sites/davidnikel/2022/03/28/myths-and-legends-about-the-northern-lights/?sh=24d22bdb13fd
National Aeronautics and Space Administration. (n.d.). Aurora History. THEMIS Mission. Retrieved from https://www.nasa.gov/mission_pages/themis/auroras/aurora_history.html
Mariner, I. I. (n.d.). NASA Facts: Venus, 2, 2.
European Space Agency. (n.d.). Swarm. ESA - Observing the Earth - FutureEO. Retrieved from https://www.esa.int/Applications/Observing_the_Earth/FutureEO/Swarm
Fahleson, U. (1967). Theory of electric field measurements conducted in the magnetosphere with electric probes. Space Science Reviews, 7(2–3), 238–262.
National Geographic Society. (n.d.). Aurora. National Geographic Education. Retrieved April 22, 2023, from https://education.nationalgeographic.org/resource/aurora
National Weather Service. (n.d.). Aurora. Retrieved April 26, 2023, from https://www.weather.gov/fsd/aurora
Magnetic Field of the Earth. (n.d.). Retrieved April 27, 2023, from http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/MagEarth.html
The Birkeland Terrella—Museum of the History of Science: Museum of the History of Science. (n.d.). Retrieved April 27, 2023, from http://www.mhs.ox.ac.uk/about/sphaera/sphaera-issue-no-7/the-birkeland-terrella/
