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The science behind the northern lights: from a solar flare to a nighttime display of color

Published: Nov. 17, 2021 at 6:15 PM CST
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BISMARCK, N.D. (KFYR) - With several viewing opportunities for the northern lights over the past couple of months in North Dakota, you may be wondering if it’s becoming a more common occurrence.

But first, let’s understand how the aurora borealis forms. To do this, we have to go 93 million miles away to the surface of the sun where solar flares can occur, ejecting mass into space.

“Sunspots are pretty much centers of eruption on the sun, kind of like what we see with volcanoes here on Earth, and some of these eruptions can be fairly strong and they can send plasma out into space — actual mass of the sun can be sent and hurled out into space,” said Zachary Hargrove, a meteorologist with the National Weather Service in Bismarck.

The Earth’s magnetic field protects most of us from these particles, but where it’s the weakest — at the poles — these particles can enter Earth’s atmosphere.

How auroras form
How auroras form(KFYR)

As the electrons collide with various molecules in our atmosphere, such as oxygen and nitrogen, the different colors of the aurora can be seen, ranging from the common green hue to the more rare red and pink colors.

How auroras form
How auroras form(KFYR)

The strength and speed that these particles impact the Earth will determine how far south the northern lights can be viewed. The Kp index is commonly used as a parameter for this, with a Kp index of five generally meaning that the northern lights can be viewed in North Dakota.

A common myth about the northern lights is that they occur more frequently in the winter, but this is not the case. It’s just that there’s more darkness in the winter allowing for a longer period of time during the night to see the aurora.

And with the sun on a 11 year cycle for activity, we’re now entering a new solar maximum where solar flares can occur more frequently, leading to more northern lights viewing opportunities.

“We should just start seeing a little more and more activity yearly as we ramp up to the next solar maximum,” said Hargrove.

So when the next viewing opportunity for the northern lights is, remember to get away from city lights, find a cloudless sky and look north!

But be patient, because forecasts can change quickly as predicting exactly when the mass ejected from the sun will reach the Earth is very tricky. There’s uncertainty in every forecast because we have very limited space observing tools for determining exactly how fast and in what direction the ejection of mass from the sun is moving.

Therefore, oftentimes we don’t know about a Northern Lights viewing opportunity until the day of or maybe one day beforehand.

So stay tuned to the Space Weather Prediction Center as they monitor solar activity and release aurora forecasts, and your First Warn Weather Team will also try to let you know when there’s viewing opportunities for the Northern Lights in North Dakota.

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