The Aurora Borealis is a true natural wonder and it has captivated people throughout history. Writing in the Daily Telegraph recently, Professor Mike Lockwood explained the phenomenon.
He noted that the Aurora lie in rings that surround the northern and southern magnetic poles. The expert, who is a professor of space environment physics at the University of Reading, added that the lights are caused by energetic particles that hit the Earth’s upper atmosphere and make it glow.
Adding clarification, he remarked: “It is often said that these particles come from the sun but for most auroras this is inaccurate. It is true that there is a stream of supersonic charged particles that is emitted from the extremely hot solar atmosphere and the Aurora is powered by energy extracted from this ‘solar wind’ as it passes Earth.”
Professor Lockwood went on to point out that different colours arise because of the various atmospheric gases involved and because of the different energies of precipitating particles.
The dominant colour, he noted, is pale green and it arises from oxygen gas at around 62 miles up. However, Oxygen is also made to glow red by lower energy particles that do not penetrate as far into the atmosphere. About this, he added: “The red tends to be seen above the green, coming from about 95 to 250 miles.”
Meanwhile, he went on to state that the green Aurora of the night side oval is usually somewhere over mainland Norway and it forms one or more “waving curtains” from horizon to horizon. He also stated: “One can often see a purple lower rim that is emission from nitrogen gas.”
Every year, the Aurora peaks in activity around the March and September equinoxes, when the tilt of the Earth’s axis “favours energy extraction from the solar wind”, the professor suggested.
When people want to witness this phenomenon for themselves, they can book special Northern Lights holidays.