Why can’t the northern lights be seen everywhere?

Published: October 19, 2018

Green northern lights illuminate the night sky Photo by Oleg Bakhirev/Shutterstock

A few weeks ago, I was visiting a friend and his grandfather at a cottage on Stoney Lake, when my friend asked: “How come we can never see northern lights anymore?” This got me thinking.

Growing up in Yellowknife, NWT., had its many wild and rugged perks. But one of the most memorable experiences I had there was getting to witness bright green and blue ribbons illuminate the night sky. As a 10-year-old child, I believed that having the northern lights painted onto the sky’s canvas was normal — just a part of everyone’s life, but as I grew older and moved to Southern Ontario, I realized that wasn’t true and that there was a lot I didn’t know about the phenomenon.

I came to understand that the northern lights, also known as the aurora borealis, is the interaction between solar wind and atoms in the Earth’s upper atmosphere—solar wind being the continuous stream of charged particles streaming out in all directions from the sun. For the most part, the Earth’s magnetic field shields us against the majority of the solar wind the sun sends our way. But when these particles do make it through and strike the upper atmosphere—at speeds of 90 to 400 km/h or more—they give off energy that we see as light.

James Edgar, an astronomy ambassador and past president of the Royal Astronomical Society of Canada, explains that the presence of different atoms in our upper atmosphere will give off different colours. For example, green and red are from oxygen, while nitrogen gives off a blue tint.

As for why the phenomenon isn’t seen everywhere on Earth equally, he explains that the aurora is greatly influenced by the Earth’s magnetic field, which directs solar wind to the magnetic poles, both north and south. The strength of the solar wind also determines how far away from the poles the aurora can be seen. For instance, when solar wind is more energetic—based on how intense activity is on the surface of the sun—the auroral oval, which circles the magnetic pole, can become larger, and thus be seen at lower latitudes.

So while there are obviously better destinations for seeing the northern lights, they could still be seen in the skies above Southern Ontario. Which brought me back to my friend’s question: why aren’t we seeing the northern lights in places we used to? 

Right now, Edgar says the sun is at a quiet stage, which means there isn’t much solar activity going on and therefore not many northern lights. He also says there are no indications that the sunspot count will increase.“Even though the sun is at a quiet stage right now, the aurora is still visible from some locations,” says Edgar. “It’s a permanent part of Earth’s atmosphere.” The closer you are to the magnetic pole, the more likely you are to see the northern lights, which explains why I saw them so often as a little girl in Yellowknife.

He also mentions how the aurora is only somewhat predictable. It isn’t related to the time of year, but is a direct result of solar activity, which is mostly random and chaotic. Plus, he explains that there’s a delay between the solar outburst and our seeing the northern lights. That’s because activity on the sun that’s directed our way will take two or three days to get to Earth.

And along with the northern lights, there are also the southern lights, called aurora australis. These lights occur simultaneously with the northern lights, but are centred on the south magnetic pole. Earth is also not the only planet to experience this phenomenon. The aurora have been detected on all planets that have a magnetic field and a gaseous atmosphere, including Jupiter, Saturn, Uranus, and Neptune. 

Looking back, having had the remarkable pleasure of witnessing the northern lights makes me feel incredibly fortunate: the way they fill the Earth’s ceiling with vibrant moving colours and how they can brighten up any dark and dreary night. Gazing up at the northern lights brings a feeling of pure awe and wonder, and understanding how and why they occur makes seeing them all the more wondrous. 

 

 

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