SCOTT SIMON, HOST:
The strongest solar storm in over 20 years is underway right now. The sun is sending charged particles into the Earth's atmosphere. That can create beautiful auroras. It can also disrupt the power grid here on Earth. The storm has reached level G5 on the National Oceanic and Atmospheric Administration scale, and that's the highest level possible. Astrophysicist Regina Barber, host of NPR science podcast Short Wave, joins us now. Regina, thanks for being with us.
REGINA BARBER, BYLINE: Thank you. I'm excited.
SIMON: Well, I guess I am, too, although I haven't seen it yet. What have I missed?
BARBER: Yeah, me neither. I was a little too south. But there's this solar storm, and it arrived last night, and it gave a lot of people a pretty good show. I've been seeing images popping up on social media of people in Europe and London, Spain - even images from, like, Florida, even as south as Alabama, that saw these northern lights. My sister was sending me images from Washington state, and they're gorgeous. I'm really sad that I missed it.
SIMON: What's going on on the surface of the sun?
BARBER: So basically, this is happening because the sun's magnetic field. It has a magnetic field like Earth. But it goes through these, like, 11-year cycles. And it's approaching its solar maximum, like, right now. It will approach the maximum in 2025. And what NOAA saw - which is the National Oceanic Atmospheric Administration - they saw that there are these massive sunspots. There was a group of them, like, a cluster of them. They were 17 times the diameter of Earth.
And these sunspots, they are these cooler parts on the sun's surface. They're related to its magnetic field getting tangled up. But what happens with the sun's magnetic field, that tangling can unwind and eject stuff - sun stuff - towards us. Those are called coronal mass ejections, and they kind of look like these huge loops. And here's heliophysicist India Jackson.
INDIA JACKSON: Those loops are full of plasma that can rain down back on to the sun and are typically associated with magnetic field lines. And then those field lines, they get twisted up and knotted up, and then they break. They pop. And then it spits out all of those high-energy particles that hurdle towards us, and we have to prepare for those things to come.
BARBER: And she says sometimes these ejections are accompanied by, like, bright flares of light on the sun's surface, and that's what NOAA saw on Wednesday in addition to those sunspots. And that kicked off this severe geomagnetic storm. And as of now, NOAA thinks there are, like, several of these coronal mass ejections that came towards Earth.
SIMON: Regina, that doesn't (laughter) sound very comforting. There can be some side effects, right?
BARBER: Yeah. So basically, these chunks of sun coming at us can disrupt the Earth's magnetic field, and it can cause some problems. And it creates electricity along very long power lines. It can cause this extra electricity to happen in power grids, and that can kind of mess them up. So here's Jackson again.
JACKSON: Now, when it comes to the power grids, the primary concern is the geomagnetically-induced currents that can cause - overload circuits and that can lead to blackouts.
SIMON: That sounds serious. Is it?
BARBER: Yeah, well, I mean, this storm was severe. It was G4, and then it actually peaked at a G5 last night. G5 is the highest on NOAA's scale. It's come back down to a G4. The last time this happened was in 2003, and it did disrupt power grids in Sweden and transformers in South Africa. But I haven't heard of anything yet being disrupted now.
Also, NOAA does issue these alerts so they it can, like, warn satellite controllers and power grid operators. So they are prepared. For now, it seems like the most intense part has passed, though. So basically, you can just kind of enjoy the northern lights. It won't be as intense as it was last night. But if - let's say, you know, there is a power outage, you'll be able to see...
SIMON: (Laughter).
BARBER: ...The northern lights if you're pretty far up north.
SIMON: Well, I think I'll look forward to that.
BARBER: OK.
SIMON: Regina Barber, with NPR science podcast Short Wave. Thanks so much.
BARBER: Thank you. Transcript provided by NPR, Copyright NPR.
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