![]() Spring and fall are by far the best seasons for aurora spotting in all locations. When solar activity is stronger, lower-latitude regions such as North Dakota, Michigan, Quebec, or Tasmania may experience auroral shows. But the light shows are far more common closer to the Poles, in chilly hot spots such as Alaska, Canada, Scandinavia, Siberia, and Antarctica. Under the right conditions, auroras might be seen at any time of the year from many places around the globe. In the very thick lower atmosphere, less than 60 miles (100 kilometers) above the planet's surface, we see a purplish mixture of red and blue lights-the signature colors of molecular nitrogen. Green photons are discharged in less than a second, so they're able to occur in the moderately dense atmosphere at middle elevations. Bright greens are most common 150 to 60 miles (240 to 100 kilometers) above Earth. That's why red appears only in the thinner air found at very high altitudes. It takes almost two minutes for an excited oxygen atom to emit a red photon, and if the atom collides with another air particle before releasing its light, the color may never emerge. Reds are the highest of the auroral colors, appearing above 150 miles (240 kilometers). In the upper atmosphere, solar particles collide with gas atoms and "excite" them with extra energy, which then gets released as light.Īn aurora's brilliant colors are determined by the compositions and densities of atmospheric gases-mostly oxygen and nitrogen-found at different altitudes. ![]() When this so-called solar wind slams into the invisible magnetic field surrounding Earth, it produces currents of charged particles, mostly electrons, which flow toward the Poles. The sun generates a constant stream of charged particles, or plasma, that's ejected in all directions into space. Auroras seen in the Northern Hemisphere are called the aurora borealis, or northern lights, while displays around the Southern Hemisphere are called the aurora australis, or southern lights.Īuroras aren't visible while the sun is shining, but our stormy star is the source of these nighttime shows. Auroras are the vibrant displays of red, green, and purplish-blue lights that appear around Earth's Poles, sometimes seeming to shimmer or pulse in the night sky.
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