Curious Iowa: Why can the northern lights sometimes be seen in Iowa?

Conditions were almost right for Aurora Borealis, a natural light display also known as the northern lights, to be visible in Iowa last week.

A light show last May was seen by people across Iowa who aren’t usually able to see the dazzling displays this far south.

A Cedar Rapids resident wondered what causes the northern lights and how often they can be seen from Iowa, so they wrote to Curious Iowa, a Gazette series that answers readers’ questions about our state and how it works, to find the answer.

“We’re kind of lucky ... when things come together and we have a favorable magnetic field and orientation, the northern lights can drive up a little further south here in the United States than over in Europe,” said Shawn Dahl, service coordinator for the Space Weather Prediction Center in Boulder, Colo.

What are the northern lights?

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The northern lights are a visible representation of geomagnetic energy from the sun interacting with the earth’s magnetic field. Much of the sun’s energy gets directed toward the North and South poles, hence the northern and southern lights.

“A lot of that energy, when it directs toward the poles, that would then react with the upper part of the atmosphere and excite certain molecules, primarily oxygen and nitrogen,” said Andy Ervin, lead forecaster at National Weather Service’s Quad Cities bureau. “And when those get excited by that energy, they kind of rise to a higher energy state, and then when they come back down to their normal state, that actually produces the visible effect that we would call Aurora Borealis.”

Last week, Aurora Borealis was visible to parts of Earth thanks to a coronal mass ejection — billions of tons of magnetized solar material that rockets off the sun and into space — on April 15.

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“It’s like the sun let loose a strong magnetic field towards earth and that magnetic energy, when it arrives here, if it’s orientated properly, it can really spin up what we call geomagnetic storms and magnetic disturbance at earth, and that’s really what drives the northern lights.”

Ervin said the lights are not to be feared.

“They’re not going to hurt you and they don’t mean anything,” he said. “They are just the Earth’s upper atmosphere reacting to geomagnetic energy.”

In Iowa, we typically see greens and purples when the northern lights are visible. These colors have to do with the interactions of the charged particles that make their way into the polar regions of Earth’s magnetic field and the heights where the molecules exist.

Greens and reds come from oxygen molecules that are excited by solar storms and return to their regular state. Purples and blues are from nitrogen molecules.

How often are the northern lights visible in Iowa?

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A few things need to happen for people to see the Aurora Borealis in Iowa.

First, you need a geomagnetic storm, “which is a burst of energy coming from the sun, more or less,” Ervin said. Then, that storm needs to be aimed at earth. The list goes on.

“We need it to be dark. We need the skies to be clear,” Ervin said. “And the last thing is even though the Aurora itself is not temperature dependent, if you’re going to stand outside for an hour or two at night in this part of the world, my guess is you’re hoping that the weather forecast is not bitterly cold or something else that’s going to prevent you from enjoying your time outside.”

Ervin said that many times, there may be an Aurora forecast to be visible, but the skies are cloudy, so the National Weather Service Quad Cities doesn’t share that information with the public.

If you’d like to see the Aurora during a geomagnetic storm, try to find a viewing location away from bright lights, like a state park.

It takes a significant solar storm for the Aurora to be visible in Iowa. Geomagnetic storms are categorized between G1 (minor) and G5 (extreme). Last week’s storm got up to a G4, which denotes severe storms. Last May, when the northern lights were visible in Iowa, a storm reached a G5.

When Dahl spoke to The Gazette last week, he said that the Space Weather Prediction Center had been in contact with the entire North American power grid as a G3 level storm can impact radio and GPS communications.

Geomagnetic storms can happen at any time, but the Aurora has been more visible lately.

Why is that?

Dahl said that activity can be stronger around the equinoxes — the dates that denote the start of spring and fall. Plus, the sun is in its solar maximum, the period in its 11-year cycle with the greatest solar activity.

How can will you know when the northern lights may be visible?

The Space Weather Prediction Center of the National Oceanic and Atmospheric Administration maintains an Aurora forecast that can be found online.

It’s also a good idea to keep an eye on local weather forecasts, which also may include notices about the northern lights’ visibility in Iowa.

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Comments: bailey.cichon@thegazette.com