Normally when you talk about the northern lights, places like Iceland or Alaska or maybe Canada come to mind. But skywatchers in Pennsylvania got to see the phenomenon late Sunday into Monday. WPSU’s Anne Danahy talked with Bill Bristow, a Penn State professor of atmospheric science, about the science behind the light show; and a Penn State meteorology student who saw Sunday night’s display.
LISTEN to their conversation
Anne Danahy
Bill Bristow, thank you for talking with us.
Bill Bristow
Sure, happy to do this.
Anne Danahy
The aurora borealis or northern lights put on quite a show Sunday night into Monday morning. For us non-scientists, what’s behind the green and the purple and the pink lights that fill the sky?
Bill Bristow
I could go into a lot of detail about the specifics of the colors, but in general, there was an eruption on the sun that sent charged particles streaming towards the earth, and that interacts with the Earth’s magnetic field, and sends them streaming into the upper atmosphere.
Anne Danahy
Are there different particles that create different colors? How does that work?
Bill Bristow
So it’s not the colors of or the particles that are coming in. It’s the the atmospheric gases. So, oxygen makes one color light, nitrogen makes a different color light. And it’s just the colors you see depend on you know, where in altitude the particles reach.
Anne Danahy
And these geomagnetic storms are rated by how strong they are. Is that right? What have we been seeing this year?
Bill Bristow
So far, not a lot. But the the storm in the last couple of days was quite strong. It reached what the Weather Service Space Weather Prediction Center classified as a strong storm. The index that they use reached 9, which is pretty pretty high, a nine out of 10.
Anne Danahy
OK, is that unusual, especially here in Pennsylvania?
Bill Bristow
Well, the storm is global. To see the northern lights here is unusual. The average location of the aurora is just north of Fairbanks, Alaska. On any given night, if you’re just north of Fairbanks, you will see them. Whereas here, it’s a couple of times a year, though, we are going into the peak of the solar cycle, which means over the next couple years, it’s more likely that big storms will happen.
Anne Danahy
OK, so in some places they’re actually fairly common.
Bill Bristow
Yeah, I used to live in Fairbanks and would see them many, many nights a year, if I was outside.
Anne Danahy
Tell us about that. What was it like when you saw them? Are there any ones that stand out?
Bill Bristow
I studied them for years from from Alaska. And you know, there are many nights that were just a spectacular show where you have the lights dancing all over the sky, with the various colors.
Anne Danahy
I wonder too, if what makes them so fascinating is that the colors in there, for example, green, that’s not something like you know, you look up at the sky, and you might see pink or purple or orange or red. But to see that kind of green shade is so unusual from our perspective.
Bill Bristow
Sure. And that’s because of the emission. If you had something on in the troposphere that excited the molecules, they would not emit the light, they would run into another molecule and get unexcited. But when they’re up in the upper atmosphere, collisions become very rare. So they get sent into an excited state. And then they have time to decay down to their ground state and generate the light.
Anne Danahy
I understand that you did not catch the Sunday night show. I didn’t either. But I talked with a Penn State student Denys Khrulov, and he’s a meteorology student. And he did, and let’s hear what he had to say about it.
Penn State meteorology student Denys Khrulov captured this picture of the Northern Lights from Jo Hays Vista in Centre County the night of April 23, 2023. Photo courtesy of Denys Khrulov
Denys Khrulov
So it was a pretty cool experience. I didn’t think I would be seeing the northern lights in Pa at the end of the weekend. But just going out to see them that night, it was just pretty cool. … It wasn’t as amazing as it was in the photos. But you could still pick it out your eyes, especially later in the night, and when your eyes got a little more adjusted, you can pick out some of the green colors in the distance and some of the colors that would pop up once in a while. … Especially with us going into an active solar cycle right now, I think we’ll definitely be seeing a lot more aurora borealis across the U.S. and even down here in PA with stronger solar storms.
Anne Danahy
He’s saying that we’re going into this stronger cycle of storms. Is that true? Can we maybe expect to see more of this?
Bill Bristow
It is true. For the last few years we’ve been at what we call solar minimum. The sun has an 11-year cycle of sunspots on its surface. And at minimum you have a minimum number of sunspots, and at maximum, a maximum. And the cycle is 11 years, so in the next few years we’ll be seeing more sunspots.
Anne Danahy
How do scientists like you know where we might be able to see them? I’m thinking also is the cloudy weather a factor?
Bill Bristow
Absolutely cloudy weather is a factor. You are only going to see the lights on clear nights and you will only see them at night of course. But you can get predictions of where to see them from some websites online. Probably the best place to go is to the Weather Service Space Weather Prediction Center. And they have displays of the phenomena that are causing the lights and predictions of where the lights will occur.
Anne Danahy
So Bill, are there any good places that people can go to get more information if they missed it this time, or they want to make sure they catch it next time?
Bill Bristow
Yeah, absolutely. There are websites that have warnings that there will be occurrences. And there’s a citizen science site called Aurorasaurus that is a place where people can report what they have seen and even upload photographs of what they’ve seen. It’s a NASA National Science Foundation sponsored program to help map the extent of the aurora using the citizen input.
Anne Danahy
Bill Bristow, thank you so much for talking with us.
Bill Bristow
You’re welcome, Anne, thank you.
