Beautiful curtains of pink and green light swirled in night skies around the world in May during one of the strongest displays of auroras in half a millennium.
The source of that light show was the sun. In the first week of May, a barrage of explosive solar flares and coronal mass ejections blasted billions of tons of material from the sun into space. This created the strongest solar storm in more than two decades, resulting in auroras as far south as Florida and parts of northern India (SN: 2/26/21).
Those celestial fireworks were just the start of what could be a years-long run of similar displays. That’s because the sun is now nearing the peak of activity in its 11-year solar cycle — and already is far stormier than originally predicted.
Auroras happen when charged particles from the sun collide with oxygen and nitrogen molecules in Earth’s upper atmosphere. As the atmospheric molecules shed the energy imparted from such collisions, they emit light in a variety of colors. Because the planet’s magnetic field directs these charged particles toward the poles, auroras are mostly seen only in the highest latitudes — unless the storms are unusually powerful.
To find out what to expect over the next few years, and to understand how this period of high solar activity impacts us, Science News talked to Teresa Nieves-Chinchilla, acting director of NASA’s Moon to Mars Space Weather Analysis Office in Greenbelt, Md., and Shawn Dahl, a space weather forecaster at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center in Boulder, Colo. The conversations have been edited for clarity and brevity.
SN: What was going on with the sun in early May that caused so much excitement?
Nieves-Chinchilla: We are getting to the maximum of solar cycle 25 [the current solar cycle, which began in December 2019]. And as we are approaching that, we have more activity from the sun, particularly in those days in May.
Dahl: Essentially, we had space weather activity going on in all three categories: from solar flares to radiation storms and, ultimately, to the geomagnetic storms that the world saw on May 10th through the 11th. There’s no doubt this was a historical storm, on par with the storm of 2003, which did cause some power outage issues in South Africa and Sweden.
SN: Much of this was caused by spots on the sun’s surface known as active regions. What are those?
Dahl: Active regions are strong areas of localized magnetic fields that show up on the sun. They form deeper within the sun, and they punch up through the surface. Because they’re so strong magnetically, they inhibit the normal transfer of energy and light from deeper in the sun. So, they appear darker, and they’re much cooler than the surrounding surface of the sun. [The regions are as hot as 3,500° Celsius, whereas the rest of the surface is about 5,500° C.]
Nieves-Chinchilla: [In active regions], we can see lots of sunspots, these black areas on the sun. These regions accumulate a large amount of magnetic energy that eventually needs to get released.
SN: How did the May 10–11 storm impact us on Earth?
Dahl: Satellite communications were degraded because the ionosphere — the [part of the] atmosphere that the communications have to go through — was quite messed up. GPS was in error massively for farmers [who use machines that rely on the technology and were] trying to plant crops, as one example. They needed to be within centimeters of accuracy, and they were off by up to 10 feet. They had to stop their operations on [May 10] because of this storm.
Launch operations were calling us — [folks] sending rockets up — because they had concerns with GPS accuracy. Aviation was changing their flight routes farther equator-ward to stay away from the communication issues. We were talking to [NASA] for the benefit of the astronauts on the space station. They were advised, when possible, to stay away from the less shielded areas of the space station [to avoid radiation].
The power grid had enormous effects throughout the system, seeing large amounts of induced currents that don’t belong there from the storm. [Operators] had equipment in place to help make sure that there was going to be no major catastrophic collapse anywhere. And, as far as we can tell, there were no bulk system failures.
SN: How do we prepare for such solar storms?
Nieves-Chinchilla: It was very interesting because [by coincidence] we had an exercise two days before the solar storm. And during this tabletop exercise, agencies were working together to evaluate if we were prepared to receive the storm. NOAA, for instance, and [the Federal Emergency Management Agency] need to talk to give notifications to specific people to be prepared for these things.
Dahl: There’s been a lot of work done over the last decade to learn more about space weather. All the technological providers that we use in society today are well aware of space weather and they incorporate it into their planning and thinking. This was the most successfully mitigated extreme space weather storm in history for that reason. That’s why we’re not hearing about a lot of confirmed impacts to our technologies.
SN: Solar cycle 25 was predicted to be relatively weak, right?
Dahl: The international panel of scientific experts that make these long-range solar cycle predictions — this was pre-2019 — they predicted a lightweight solar cycle very similar to the previous one, which was not all that active. We are well outside that original margin of error with that forecast. We expect solar max at this point to be much more active than originally anticipated. So, all of this year, all of 2025, and even into 2026 we anticipate to be at the highest risk for another such event.
SN: Those regions on the sun that caused the May storm are about to face Earth again. Can we expect similar events soon?
Nieves-Chinchilla: We don’t know yet. But I can tell you that there are several X-ray flares coming from this region.
Dahl: Perhaps we’ll see some more activity, but it certainly will not be anywhere close to what happened on May 10th or 11th. People should always go to our webpage to find out the real story of what’s factually going on and what we’re predicting.
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