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Auroras explained: How the sky puts up a spectacular lights show

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Monday, 30 May 2016 - Last Updated on May 30, 2016
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auroras-1203288_640Beyond being a spectacle of glowing lights up in the sky, auroras are actually outcomes of atomic interaction somewhere in the Eath’s atmosphere.

Auroral light, which is visible to polar regions in the north as Aurora Borealis and to the south as Aurora Australis, has been a much awaited evening sky phenomenon for space enthusiasts and even ordinary folks on Earth’s opposite sides.

During the phenomenon, glowing, shifting curtains of green with a faint touch of red wrap the night sky, extending upward until the colorful brush strokes gently vanish into a stellar background. A NASA space observer said that “like snowflakes, each display is different from the last.”

Residents of Seattle were treated to an unusual sighting of Aurora Borealis in the first few hours of May 8, which was described by the National Weather Service in Seattle as “probably the best aurora display we’ve seen in a decade here.”

In April, the NASA posted a breakthtaking 4K video of Aurora Borealis on Youtube, the first video made available online by the space agency from its ultra high definition (UHD) television channel.

The phenomenon was documented using time-lapse shots from the International Space Station (ISS), a satellite at low Earth orbit approximately 400 kilometers above the Earth’s surface.

 

Solar wind meets Earth’s atoms

Perhaps unknown to many, auroral light begins with a solar wind, a stream of charged particles emitted through space from the sun’s surface. During active parts of the solar cycle, solar flares packed with powerful energy and coronal mass ejections (CME) launch billions of tons of plasma into space. Some of these charged particles eventually reach the Earth’s magnetosphere.

The particle streams from the sun get deflected at first by the magnetoshpere and swirls past Earth, and then pushes in again at night side. These particles eventually “rain down into the upper atmosphere over the polar regions, the places where our protective magnetic envelope is most open to space.”

“Auroral light comes largely from electrons hitting oxygen and nitrogen atoms and molecules in the upper atmosphere, the same phenomenon that produces the glow in a neon lighting tube. But in the aurora the illumination can be 600 miles (965.6 kilometers) high, stretch for thousands of miles, and be linked to a magnetospheric power generator churning out three million megawatts or more—about four times the electricity the United States uses at peak summer demand,” a National Geographic article explained.

The color of auroral light depends on the atomic particles in contact, with red and green for oxygen and green and blue for nitrogen.

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Beautiful but dangerous?

Auroras are essentially beautiful outcomes of particle interations over the Earth’s polar magnetic regions. The spectacle, while generally causing no harm on human activity, can be disruptive at times though.

It was in March 13, 1989 when auroras’ extreme reach was demonstrated, when a powerful explosion in the sun created a geomagnetic storm that resulted in spectacular northern lights. The amazing aurora borealis show could be seen as far south as Florida and Cuba. At the same time, electrical currents were created in the ground, which found weakness in the electrical grid of Quebec. The geomagnetic storm shut down Dorval Airport and Montreal Metro, and left people in office buildings and tunnels in the dark.

NASA astronomer Dr. Sten Odenwald described the phenomenon as “the day the Sun brought darkness” on Earth.

“The Quebec Blackout was by no means a local event. Some of the U.S. electrical utilities had their own cliffhanger problems to deal with. New York Power lost 150 megawatts the moment the Quebec power grid went down. The New England Power Pool lost 1,410 megawatts at about the same time,” Dr. Odenwald said.

In today’s digital era when people are heavily dependent on eletronic gadgets and when most vehicles from cars to tractors are mostly dependent on GPS, such powerful storm could cause serious trouble.

Thankfully, scientists have devised means to predict geomagnetic storms at least a day in advance.

A team led by Dr. Neel Savani at Imperial College London has produced a modelling tool that will forecast coronal mass ejections and solar flares more than 24 hours in advance.

The modelling tool projects the initial form of the coronal mass ejections and their evolution as they travel towards the Earth. With these, scientists can now determine the extent by which the storm will affect the Earth and the estimated time of the phenomenon.

For now, we can enjoy the dreamy Aurora show without worrying about another aurora-caused power disruption in the magnitude of the 1989 geomagnetic storm.

Images: Northern Lights, Auroras Camp and Aurora Astralis from Pixabay.com.

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