Sunspots that caused solar storm could bring more auroras to Earth


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Colorful auroras could appear again soon over parts of the United States — including northern and upper Midwest states from New York to Idaho — due to a solar storm that may affect Earth, according to the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center.

The center, a division of the National Weather Service, issued a modern geomagnetic storm watch, known as a G2, for Friday and Saturday. Unlike the G5, or extreme geomagnetic storm, that occurred on May 10, moderate storm watches are not uncommon, according to the center.

But the aurora-causing solar flares and coronal mass ejections currently spewing from the sun are a result of the same sunspots that triggered solar activity in May, according to Dr. Ryan French, solar physicist at the National Solar Observatory in Boulder, Colorado.

Coronal mass ejections are large clouds of ionized gas called plasma and magnetic fields that erupt from the sun’s outer atmosphere. When these outbursts are directed at Earth, they can cause geomagnetic storms, or major disturbances of Earth’s magnetic field.

As the sun nears solar maximum — the peak in its 11-year cycle, expected this year — it becomes more active, and researchers have observed increasingly intense solar flares erupting from the fiery orb.

Increased solar activity causes auroras that dance around Earth’s poles, known as the northern lights, or aurora borealis, and southern lights, or aurora australis. When the energized particles from coronal mass ejections reach Earth’s magnetic field, they interact with gases in the atmosphere to create different colored lights in the sky.

The sun rotates on its axis once every 27 days, which scientists have learned by tracking sunspots. These dark regions, some of which can reach the size of Earth or larger, are driven by the star’s strong and constantly shifting magnetic fields.

The northern lights were visible over Rochester, New York, on May 11. - Lokman Vural Elibol/Anadolu Agency/Getty ImagesThe northern lights were visible over Rochester, New York, on May 11. - Lokman Vural Elibol/Anadolu Agency/Getty Images

The northern lights were visible over Rochester, New York, on May 11. – Lokman Vural Elibol/Anadolu Agency/Getty Images

The large, complex clusters of sunspots on the sun’s surface that drove increased solar activity in May have survived their rotation around the sun. The European Space Agency’s Solar Orbiter mission, currently studying the backside of the sun, was able to monitor the progress of the sunspots while they were out of view of Earth’s telescopes.

Now, the sunspots are returning to the side of the sun facing Earth, which means the chances for dazzling auroral displays could increase over the next week, experts say.

The birth of solar storms

While it’s typical for sunspot clusters to survive two to three rotations around the sun, they typically decay after one rotation and become less active, French said.

The sunspot cluster coming back around now is still capable of producing X-class flares, the largest of solar flares, but the frequency appears to have decreased, he said.

French observed two X-class flares per day for about six days in May.

“It’s probably the highest cluster of X-class flares that we’ve had in a couple of decades,” French said. “This current solar cycle seems to be more active than the 2014 peak, but not as active as the 2003 peak.”

The sunspots responsible for the May 10 solar storm began much larger (left) before they completed a rotation around the sun. Now, the sunspots (right) have reappeared and are less complex, solar physicist Dr. Ryan French said. - Ryan French/Solar Dynamics ObservatoryThe sunspots responsible for the May 10 solar storm began much larger (left) before they completed a rotation around the sun. Now, the sunspots (right) have reappeared and are less complex, solar physicist Dr. Ryan French said. - Ryan French/Solar Dynamics Observatory

The sunspots responsible for the May 10 solar storm began much larger (left) before they completed a rotation around the sun. Now, the sunspots (right) have reappeared and are less complex, solar physicist Dr. Ryan French said. – Ryan French/Solar Dynamics Observatory

Now, the sunspots are producing flares every two days, so the frequency has gone down, and the complexity of the sunspot cluster has decreased, French said.

Earth is predicted “to just catch the very edge” of the coronal mass ejection currently en route, French said.

The sunspots will face Earth in a more direct way between Tuesday and Thursday, French said.

“Any larger eruptions during that time, and a few days outside of that window, could cause an eruption heading our way and that could cause a geomagnetic storm,” French said. “The frequency of things is decreasing, but you only need one to cause a large geomagnetic storm. Whether that one will be large enough to cause something matching what we saw in mid-May I think is unlikely.”

Keep an eye out for auroras during that Tuesday to Thursday window as well as a few days after it, French said. The auroras could be visible to millions, but the locations depend on if any coronal mass ejections affect Earth.

A panel of experts typically declare the peak of solar maximum well after it has passed, so scientists can’t say whether solar maximum is occurring right now. But an increased chance of solar activity is expected over the next two years, French said.

“The thing about solar cycles is sometimes they kind of have a twin peak,” said Shawn Dahl, service coordinator for the Space Weather Prediction Center. “Sometimes the (sun’s) southern hemisphere or the northern hemisphere will kind of peak first.”

Near the peak of solar maximum, sunspots tend to gather around the equator. But the sunspot clusters that have been active over the past month were in the northern and southern hemispheres of the sun, Dahl noted.

While scientists can track active sunspot clusters, others could appear at any time during the lead-up to solar maximum.

“We can have a new sunspot group emerge right in front of us,” Dahl said. “We have no way of knowing that’s about to happen until we see it. That’s just the way it’s going to be over the course of this year all the way through next year and even into 2026.”

Lessons learned from solar storms

The May 10 storm was a historic one, but fortunately it didn’t reach the level of the Carrington Event of 1859, which caused telegraph stations to spark and catch fire and remains the most intense geomagnetic storm ever recorded.

Before May 10, the last G5 storm to hit Earth occurred in 2003, resulting in power outages in Sweden and damaging power transformers in South Africa.

Since then, governments have taken measures with legislation, research and operations to mitigate the potentially negative impacts of solar storms, Dahl said.

The solar storm on May 10 was the most successfully mitigated space weather storm in history, Dahl said.

“All this work and preparation led to this moment, and the nation could not have been any more prepared for a space weather storm,” he said.

With these events, there’s always a chance that communications, the electric power grid, navigation, and radio and satellite operations will be affected. During the May 10 storm, power grid and satellite operators kept satellites in order and properly in orbit and managed the buildup of intense geomagnetic currents on the grid systems.

Extreme solar storms can cause Earth’s atmosphere to swell, which changes the level of drag that satellites experience, so it’s more difficult for operators to keep them within their specific trajectories, according to the European Space Agency.

“There were a lot of effects that people aren’t going to hear about because things were successfully mitigated where we weren’t seeing direct impacts as much,” Dahl said.

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