Not that it matters: no fact about their cause or origin can affect our pleasure over the dancing curtains of pale blue, bright green and shimmering purple that fall out of the polar skies by the name known worldwide as northern lights. Knowing that How it occurs is as interesting as seeing it from the eyes.Â
Physics theorists have discussed this special light (northern light) phenomenon produced at a particular location-the Earth’s polar regions-since for quite some time.
What are the Northern Lights?
Near the two poles of the northern and southern hemisphere the aurora has been seen for more than a thousand years. So in the north this was called the aurora borealis; in the south, it is still just called the aurora australis.
For over a thousand years ‘northern’ and ‘southern lights’ have enchanted, frightened and inspired human beings. It has only recently been left to photographers to make heroic attempts to reproduce the glory of these magnificent atmospheric happenings.
What causes Northern Lights?Â
The sun is unstable, and violent processes there like geomagnetic storms can reverberate outward into the cosmos. Some of the solar disturbances are so powerful that they reach out and snap at Earth’s magnetic field like an elastic band, pulling it away from the planet.
But, like a stretched rubber band when it snaps back, the magnetic field springs back and the energy from that snapback makes mighty waves called Alfvén waves 80,000 miles above the Earth. When these waves are closer to Earth, they speed up even more with the magnetic pull of the planet. Electrons headed for Earth on the same space highway do not travel as fast as the Alfvén waves.
Sometimes, electrons hitch a ride on these super-fast Alfven waves, occasionally even travelling as fast as 45 million miles an hour while falling.
“Think about surfing,” says Jim Schroeder, assistant professor of physics at Wheaton College and lead author of the paper. “To surf, you have to paddle up to the appropriate speed for an ocean wave to catch you and push you along, and that’s exactly what we see the electrons doing. When they were moving at just the right speed relative to the wave, they got caught up and accelerated by it.“
An illustration shows how electrons “surf” on passing Alfvén waves, which eject the electrons at high speed into Earth’s atmosphere where they produce the aurora.
According to Austin Montelius/College of Liberal Arts and Sciences, University of Iowa,the electrons eventually reach Earth’s thin upper atmosphere, where they collide with nitrogen and oxygen molecules, exciting them. These excited electrons slowly return to their ground state, releasing light and what we see in the form of an aurora.
What Colours does the Aurora Produce?
Other elements glow in other colours as they heat up. And that’s exactly what’s happening to the aurora.
Nitrogen and oxygen are the two main components of the Earth’s atmosphere, and it is from these elements that we have different colours in an aurora display.
The colour of the aurora depends on which of the two main components is responsible for its colour. Oxygen is greenish in colour, whereas slight traces of purple, blue or pink are due to nitrogen.
According to astronomer Tom the scarlet red colour is caused by the very high altitude of oxygen interaction with solar particles.”This occurs when the aurora is energetic.”
Places to see Northern LightsÂ
Northern lights, on the other hand, are also referred to as aurora borealis. You can see them most amazingly from the Northern Hemisphere if they are near the Arctic Circle. Some of the best viewing places for northern lights are:
- Iceland– The distant Westfjords is an excellent place to witness northern lights.
- Fairbanks, Alaska, is among the best destinations to see the northern lights.
- Abisko, Sweden: Two mountains have a cloud-free microclimate at night, located 125 north of the Arctic Circle.
- Yellowknife, Canada: You are in the middle of the auroral oval. You might even catch a glimpse of northern lights.
- Tromsø, Norway: Take part in an expedition and be drawn to northern lights.
- Rovaniemi, Finland: This is the official hometown of Santa Claus. And northern lights are enough reasons to visit Rovaniemi.
Conclusion
Auroras are developed due to magnetospheric disturbances produced by the solar wind. Important disturbances have been observed from an increase in the velocity of the solar wind, resulting from holes in the corona or coronal mass ejection. Such disturbances alter trajectories of charged particles within plasma of the magnetosphere. These charged particles consist almost entirely of electrons and protons and fall into the upper atmosphere-thermosphere/exosphere. This produces the ionization and excitation of atmospheric constituents to varying colour and complexity, which emit light. The shape of the aurora also depends upon the amount of acceleration given to the precipitating particles, occurring within bands around both polar regions.
Also Read: Why are the Northern Lights sometimes colored differently? | Top 8 Magical Places to View Auroras or Northern Lights
