An aurora, which is sometimes referred to as northern lights, is a natural display in the Earth’s sky, usually seen in high-altitude regions. However, they only appear at night and in lower polar regions. Northern lights usually consist of many beautiful, colorful lights that move gently and softly like curtains in the sky. The magnificent lights are visible almost every night near the Arctic and Antarctic circles. In the north, the show is called aurora borealis or northern lights, and in the south, it is called aurora australis or southern lights.
These wonders are the result of disturbances in the magnetosphere caused by the solar wind. These activities that create the auroras really start in the sun. The sun is a ball made up of superhot gases composed of electrically charged particles, also known as ions. The ions, which continuously surge from the sun’s surface, are commonly known as solar winds. As these solar winds come closer to Earth, it greets the planet’s magnetic field. Without this magnetic field protecting the planet, life on Earth would not be possible because it would disturb Earth’s fragile atmosphere. Most of these solar winds are blocked by the magnetosphere, causing the ions to be forced around the planet, allowing them to continue traveling further into the solar system.
Although most of these solar winds are blocked by the Earth’s magnetosphere, some of the ions are trapped, for a short period of time, in ring-shaped holding areas, which are located around the planet. These areas, which are in a region called the ionosphere, are centered around the Earth’s geomagnetic poles. The geomagnetic poles mark the tilted axis of the Earth’s magnetic field. In the ionosphere, the solar wind ions collide with oxygen and nitrogen atoms from the Earth’s atmosphere. The energy released during these collisions causes a colorful glowing halo around the poles, which are actually the auroras. Most of these wonders happen anywhere between 97-1,000 kilometers above the Earth’s surface. The most active auroras usually happen when the solar winds are the strongest. Although the solar winds are mostly constant, the solar weather, which heats and cools different parts of the sun, can change all the time, sometimes daily.
Solar weather is usually measured in sunspots, which are the coldest part of the sun and appear as dark sections on the sun’s white-hot surface. Solar flares and coronal mass ejections are also associated with sunspots. Both are sudden, extra bursts of energy in the solar winds. Sunspot activity is tracked over an eleven-year cycle. The height of sunspot activity is usually when auroras are most bright and consistent. Increased activity in solar winds happens during every equinox. These normal fluctuations are known as magnetic storms, leading to auroras being seen in the midlatitudes during the spring and autumnal equinoxes. Magnetic storms and active auroras sometimes interfere with communications. They can disrupt radio and radar signals and some intense magnetic storms can also disable communication satellites.
Finally, the most iconic aspect of auroras, colors. Each aurora’s colors vary depending on the altitude and atoms involved. If ions strike the oxygen atoms at high points in the atmosphere, the interaction tends to produce a red glow in comparison to a green-yellow, which occurs at lower points in the atmosphere. The red and blue light that appears in the lower parts of the auroras is produced by ions striking atoms of nitrogen in the Earth’s atmosphere. Ions that strike hydrogen and helium atoms tend to produce blue and purple auroras, however, our eyes barely detect this section of the electromagnetic spectrum.
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By: Zubin Sidhu
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References: Boudreau, Diane, et al. “Aurora.” National Geographic, 14 May 2011, www.nationalgeographic.org/encyclopedia/aurora.
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