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As the sun nears the peak of its current solar cycle, our star is growing increasingly active. And that peak may be occurring sooner than predicted, according to scientists.
Every 11 years or so, the sun experiences periods of low and high solar activity, which is associated with the amount of sunspots on its surface. These dark regions, some of which can reach the size of Earth or larger, are driven by the sun’s strong and constantly shifting magnetic fields.
Over the course of a solar cycle, the sun will transition from a calm to an intense and active period. During the peak of activity, called solar maximum, the sun’s magnetic poles flip. Then, the sun will grow quiet again during a solar minimum.
Initially, peak activity was forecast to begin in July 2025. Now, experts believe the cyclical peak is more likely to take place in mid- to late 2024.
A solar activity spike
The current solar cycle, known as Solar Cycle 25, has been full of activity, more so than expected. Scientists at the National Oceanic and Atmospheric Administration’s Space Weather Prediction Center in Boulder, Colorado, have already tracked more sunspots than those counted at the peak of the previous cycle.
“No two solar cycles are the same,” said Mark Miesch, research scientist at the Space Weather Prediction Center. “This solar maximum is the space weather equivalent of hurricane season. It’s when we see the biggest storms. But unlike hurricane season, which lasts a few months, solar maximum lasts a few years.”
The increased activity has also included strong solar flares and coronal mass ejections, or large clouds of ionized gas called plasma and magnetic fields that erupt from the sun’s outer atmosphere. The solar storms generated by the sun can affect electric power grids, GPS and aviation, and satellites in low-Earth orbit. These events also cause radio blackouts and even pose risks for crewed space missions.
A well-known example happened when a series of coronal mass ejections erupted from the sun on January 29, 2022, causing Earth’s outer atmosphere to heat and expand. This expansion caused 38 of the 49 Starlink satellites launched by SpaceX to burn up.
But the increase in activity isn’t unusual, and it will only continue as solar maximum approaches.
“It’s absolutely normal,” said Dr. Alex Young, associate director for science within NASA’s Heliophysics Science Division at the Goddard Space Flight Center in Greenbelt, Maryland. “What we’re seeing is overall completely expected. As you get closer to solar maximum, you see more sunspots appear in clumps. Those clumps will sometimes be bigger and last longer.”
As the solar maximum nears, sunspot clumps will form with increasingly greater frequency, leading to the boost of activity.
“As we become more dependent on technology, on electrical power grids, on satellites, on aircraft and on GPS, the impacts of space weather increase because these are the kinds of systems that are affected by solar storms,” Miesch said. “Although this particular cycle isn’t anything remarkable from the sun’s point of view, it is from our point of view.”
Predicting what the sun will do
The new predictions for solar maximum were led by Scott McIntosh, deputy director of the National Center for Atmospheric Research, and Robert Leamon, an associate research scientist at the Goddard Planetary Heliophysics Institute, along with their collaborators. The institute is a partnership of the University of Maryland, Baltimore County, the University of Maryland, College Park, and American University with NASA.
Rather than tracking sunspots, the researchers focused on what they call “the terminator,” the point when activity from one solar cycle disappears from the sun’s surface, followed by a sharp increase in solar activity in the new cycle.
Sunspots are regarded as a keystone of solar cycle prediction, but Leamon said he and his colleagues believe that tracking the magnetic activity that leads to the sunspots could yield more accurate predictions.
Once solar maximum is reached, the activity can persist for years.
In fact, the number of solar flares peak after maximum, Leamon said. The increase occurs on the rising phase of even numbered solar cycles, and during the declining phase of odd cycles.
“The peak of consequence is after maximum by a couple of years, so the biggest effects here on Earth will happen after maximum,” he said. “That’s when you expect to see the biggest fireworks. Even if there are fewer sunspots, they are more productive.”
While it typically takes about four years to transition from solar minimum to solar maximum, there’s no simple peak for maximum because the sun is so variable, Miesch said.
Sometimes two peaks occur during some solar cycles when the sun’s northern and southern hemispheres are out of sync, Young said. This can happen when the number of sunspots in one hemisphere peak at a different time than the other hemisphere, causing an extended maximum.
Solar maximum can last about two years before things die down, meaning the chance of solar storms can remain high for longer than the actual peak, Miesch said.
Northern and southern lights
A more positive side effect of increased solar activity, however, is the 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 light in the sky.
Geomagnetic storms driven by the sun in February and April caused auroras to be visible in places where they are rarely seen, including as far south as New Mexico, Missouri, North Carolina and California in the United States, and the southeast of England and other parts of the United Kingdom.
Depending on the location, the auroras may not always be visible overhead, but they may cause a colorful display on the horizon as well, Young said.
For those interested in seeing more intense auroras in the future, it may be worth a trip to Alaska, Canada, Iceland, Norway, Scandinavia or the upper peninsula of Michigan, Young said.
“Having seen aurora, they’re one of the most amazing things that I’ve ever experienced,” he said.
Tracking solar storms
While the most likely time for solar storms to occur is during the maximum, they can happen at any time in the cycle, Miesch said.
Teams at the Space Weather Prediction Center use data from ground and space-based observatories, magnetic maps of the solar surface, and ultraviolet observations of the sun’s outer atmosphere to determine when the sun is most likely to send out solar flares, coronal mass ejections and other space weather that could affect Earth.
The center provides forecasts, watches, warnings and alerts as soon as possible to those affected by space weather, varying hours to weeks ahead of time, said Bill Murtagh, the center’s program coordinator.
Solar flares can affect communications and GPS almost immediately because they disrupt Earth’s ionosphere, or part of the upper atmosphere.
Energetic particles released by the sun can also disrupt electronics on spacecraft and affect astronauts without proper protection within 20 minutes to several hours.
The material sent speeding away from the sun during coronal mass ejections can arrive at Earth between 30 and 72 hours afterward, causing geomagnetic storms that affect satellites and create electrical currents in the upper atmosphere that travel through the ground and can have an impact on electric power grids.
Regions just east of the Appalachian Mountains, in the Upper Midwest and within the Pacific Northwest are more susceptible to power grid disruption because the ground conducts current differently in those areas based on its composition, according to research from the US Geological Survey.
The storms also affect flight patterns of commercial airlines, which are instructed to stay away from Earth’s poles during geomagnetic storms due to loss of communication or navigation capabilities.
Predicting when the next big solar storm will have an impact on Earth is difficult. Extreme storms have occurred before, such as one that knocked out the power grid in Quebec in 1989 and the Carrington Event of 1859.
The latter remains the most intense geomagnetic storm ever recorded, causing telegraph stations to spark and catch fire.
If such an event were to occur today, it could cause trillions of dollars’ worth of damage and bring down some power grids for a substantial amount of time.
“We do not know when the next big one will occur,” Murtagh said. “It could happen a couple of weeks from now or 50 years from now.”
Unraveling the remaining secrets of the sun through missions such as NASA’s Parker Solar Probe and the European Space Agency’s Solar Orbiter could improve predictions. And scientists will have a chance to study the sun during the total solar eclipse on April 8, 2024.
The sun and its mysteries have fascinated humanity for millennia. The sun anchors our solar system and provides the heat and light life needs to survive, yet many questions remain about its interior, which drives its magnetic activity.
“On the one hand, it affects our daily lives,” Miesch said. “We’ve organized our societies around the seasons of the sun from the beginning. But at the same time, it’s a window to the cosmos.”