What Causes the Aurora?
The Aurora Australis dances over the South Pole. This photo was snapped from the International Space Station on June 20th.
CREDIT: Doug Wheelock, NASA.
The aurora lights have dazzled and mystified human civilizations for centuries. The psychedelic light show is the natural result of fast-moving particles from the sun entering the Earth's outer atmosphere.
Once believed by ancient civilizations to be signs from the gods, auroras are created when the Earth’s magnetic field manipulates particles from space. These particles collide with the natural gases in our atmosphere, creating the aurora lights as a result.
How it works
The sun constantly emits electrically-charged particles called ions in a stream of plasma, or ionized gas, known as the solar wind. The Earth’s magnetic field acts as a shield against the solar wind by capturing these high-energy particles and channeling them around the planet, forming a protective bubble called the magnetosphere.
However, some of these particles filter through magnetosphere. The particles then descend into the Earth's atmosphere, imparting energy to the oxygen and nitrogen molecules there, and exciting the electrons of these gas molecules. As the excited electrons return to their normal state, they release photons, or small bursts of energy in the form of light.
This light becomes visible in form of auroras, also known as polar auroras.
Where you can see them
Because the particles are drawn by magnetism to the planet's poles, auroras are only witnessed in areas near the North and South Pole. The aurora australis, also referred to as the southern lights, is only visible from high southern latitudes in Antarctica, South America and Australia.
The aurora borealis, also known as the northern lights, is only visible in the Northern Hemisphere, and the chance of seeing it increases the closer you are to the North Pole. The best places to witness auroras are Alaska, Canada and Scandinavia, according to NASA.
Because the intensity of the light is low, it can only be seen at night, with heightened activity nearing midnight. Auroras can move and change shape rapidly, but are usually seen as long wisps of light stretching across the sky for most of the night.
Auroras usually show up in glowing, ghostly shades of lime green. However, as energy builds up within the magnetic field, it sometimes releases a burst of electrical current. This is called a substorm, and results in pulsating lights in shades of scarlet, fuchsia, violet, amethyst, aquamarine and white.
- Can You See a Sonic Boom?
- Space.com Image Gallery: Colorful Aurora
- Video: Secret of the Northern Lights Revealed
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