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Auroras: Nature's Polar Light Show
May 12, 2024 at 11:23 AM EDT
By WeatherBug's Brandon Bush
The visual beauty of Earth’s sky takes many forms including rainbows, colorful sunsets and spectacular cloud formations. All of these are usually visible practically everywhere on the globe; however, one particularly special phenomenon in the sky is a high-latitude delight.
To the Inuit people, they were the dancing spirits of their ancestors. For the Norse people, they were fiery sky bridges built by gods. Nowadays, we refer to them as the northern lights, or more sophistically the Aurora Borealis. Given the name, it can be tempting to think that they only occur in the northern hemisphere. However, they have a southern counterpart called the Aurora Australis.
The auroras appear as long streams of light emanating across the sky. Most of the time they are green, but hints of pink can appear too. Stronger displays may appear red, purple or even white. Usually when they occur, both the northern and southern lights will shine at the same time and often in similar patterns, but occasionally the northern lights can be active while the southern lights aren’t, and vice versa.
The formation of the aurora is fully dependent on interactions between tiny particles near the top of Earth’s atmosphere. Between 60 and 200 miles above the Earth’s surface, oxygen and nitrogen interact with charged particles that flow out from the Sun. The colors also depend on the gas that is being excited. Oxygen usually gives off the brilliant green colors, while nitrogen produces more blue and red colors. The Sun’s charged particles are emitted from sunspots that form on its surface. The emitted radiation is known as Solar Wind and takes about 40 hours to reach the Earth.
The gas atoms and molecules in Earth’s atmosphere get excited by the Sun’s particles and emit the light that we see on the surface. Atoms consist of a nucleus and a surrounding series of orbital levels. The orbital levels are the region of space where the electrons surrounding the nucleus are housed. Conceptually, it’s the same as the Sun at the solar system center and the planets occupying various orbital levels. When particles from the Sun strike the atom, the electrons move between different orbital levels. When this happens, the atom becomes excited and light is emitted.
The Arctic Circle presents the best locations to view the aurora. Northern Canada’s Yukon, Nunavut and Northwest Territories, Alaska, Greenland, Iceland, Sweden, Norway and Finland are primed viewing spots. During the winter, the Arctic Circle is dark for nearly 24 hours each day, so this is the optimal time of year to see the amazing lights. September, October, March and April are also prime months to see the auroras. The southern lights are harder to see because they usually don’t occur outside of the Antarctic Circle and southern Indian Ocean.
Every 11 years, auroral activity peaks in occurrence with sunspot activity. The last peak occurred in 2013, leaving 2024 as the next opportunity to see the northern lights at their brightest. During these peak showings, the aurora can extend much farther south, if the conditions are right. In the rarest occasions, the northern lights have been seen as far south as New Orleans. However, total darkness is necessary for the best viewing experience.
Image: The Aurora Borealis, or northern lights, above Bear Lake, Alaska (U.S. Air Force Photo By Senior Airman Joshua Strang via Wikimedia Commons)
To the Inuit people, they were the dancing spirits of their ancestors. For the Norse people, they were fiery sky bridges built by gods. Nowadays, we refer to them as the northern lights, or more sophistically the Aurora Borealis. Given the name, it can be tempting to think that they only occur in the northern hemisphere. However, they have a southern counterpart called the Aurora Australis.
The auroras appear as long streams of light emanating across the sky. Most of the time they are green, but hints of pink can appear too. Stronger displays may appear red, purple or even white. Usually when they occur, both the northern and southern lights will shine at the same time and often in similar patterns, but occasionally the northern lights can be active while the southern lights aren’t, and vice versa.
The formation of the aurora is fully dependent on interactions between tiny particles near the top of Earth’s atmosphere. Between 60 and 200 miles above the Earth’s surface, oxygen and nitrogen interact with charged particles that flow out from the Sun. The colors also depend on the gas that is being excited. Oxygen usually gives off the brilliant green colors, while nitrogen produces more blue and red colors. The Sun’s charged particles are emitted from sunspots that form on its surface. The emitted radiation is known as Solar Wind and takes about 40 hours to reach the Earth.
The gas atoms and molecules in Earth’s atmosphere get excited by the Sun’s particles and emit the light that we see on the surface. Atoms consist of a nucleus and a surrounding series of orbital levels. The orbital levels are the region of space where the electrons surrounding the nucleus are housed. Conceptually, it’s the same as the Sun at the solar system center and the planets occupying various orbital levels. When particles from the Sun strike the atom, the electrons move between different orbital levels. When this happens, the atom becomes excited and light is emitted.
The Arctic Circle presents the best locations to view the aurora. Northern Canada’s Yukon, Nunavut and Northwest Territories, Alaska, Greenland, Iceland, Sweden, Norway and Finland are primed viewing spots. During the winter, the Arctic Circle is dark for nearly 24 hours each day, so this is the optimal time of year to see the amazing lights. September, October, March and April are also prime months to see the auroras. The southern lights are harder to see because they usually don’t occur outside of the Antarctic Circle and southern Indian Ocean.
Every 11 years, auroral activity peaks in occurrence with sunspot activity. The last peak occurred in 2013, leaving 2024 as the next opportunity to see the northern lights at their brightest. During these peak showings, the aurora can extend much farther south, if the conditions are right. In the rarest occasions, the northern lights have been seen as far south as New Orleans. However, total darkness is necessary for the best viewing experience.
Image: The Aurora Borealis, or northern lights, above Bear Lake, Alaska (U.S. Air Force Photo By Senior Airman Joshua Strang via Wikimedia Commons)