Shawn Dahl was deep into a tabletop simulation about solar storms with other federal staff on May 9, 2024, when notification came about the real thing. It turned out to be one of the largest geomagnetic storms in a generation.
The G5 event — the most intense on the National Oceanic and Atmospheric Administration’s (NOAA) geomagnetic storm scale — unfolded over two to three days. Planes were rerouted to overcome high-frequency radio interference, and power grids experienced electrical surges. Satellites encountered drag, potentially shortening their lifespan, and many GPS receivers stopped working.
“We start talking to the forecasters back at the Space Weather Prediction Center and it turns out there’s a flurry of these CMEs [coronal mass ejections],” Dahl, the center’s service coordinator, told Apogee. “We started briefing in real time a space weather event, kind of preempting the exercise and saying, ‘OK, we really have something going on here.’”
Dahl and NOAA team members in Denver, Colorado, Washington, D.C., and at NOAA’s Space Weather Prediction Center (SWPC) in Boulder, Colorado, pored over data and issued warnings to power grid operators through the North American Electric Reliability Corp. (NERC) and to other agencies. In the end, no significant impacts were reported, largely due to the advanced notification.
When they receive notification about pending CMEs, power grid managers can make adjustments to avoid damage to relays, transformers and other equipment. When charged particles from a CME interact with Earth’s magnetosphere-ionosphere, they produce currents called electrojets. Typically millions of amperes in magnitude, electrojets interact with Earth’s geomagnetic field to create geomagnetic induced currents (GIC) that can flow into power transmission lines and overwhelm relays and transformers, according to NERC. With advanced warning, power grid managers can blunt the effects of GIC by redistributing power, draining off excess power and shutting down parts of the grid not immediately vital. Recognizing the threat posed by CMEs, some grid operators in recent years have installed specialized relays equipped to handle GIC surges and capacitors that can absorb and drain off excess amperage. Other technologies include specialized flywheels that speed up to dissipate current and neutral blocking devices (NBD), which are relatively new and have undergone recent testing. Activated when the amperage exceeds a threshold, NBDs block GIC (DC current) from reaching transformers.
During instances of solar flares and solar radiation, advanced warning helps airports and the military understand the source of radio interference and allows them to reroute planes and make frequency adjustments. They also help satellite operators to be aware of ionized solar particles and to adjust the altitude of spacecraft to keep them from falling out of orbit.
I believe it is critical to continue researching ways to protect electrical systems against the effects of geomagnetic storms, for example by installing devices that can shield vulnerable equipment like transformers and by developing strategies for adjusting grid loads when solar storms are about to hit. In short, it’s important to work now to minimize the disruptions from the next Carrington Event. ~ David Wallaceassistant clinical professor of electrical engineering at Mississippi State University
Solar weather experts described the May 2024 event as the strongest since the Halloween solar storm of 2003, which also registered as a G5. That event — more severe than its 2024 successor — disabled a dozen transformers in South Africa, resulting in their replacement, and caused an hourlong power outage in Sweden. In addition, satellite and communications systems were damaged and astronauts aboard the International Space Station were forced to take cover from the high radiation levels.
Forecasters have since learned much about solar weather, thanks in part to advancements in sun monitoring technology. “We’ve learned so much more because that storm in 2003 really provided the impetus to start paying attention to affected industries and technology,” Dahl said.
That goes for satellite operators, as well. Chris Jones, vice president, network operations, at satellite communications company Iridium, told Apogee that the company continually analyzes space weather data and keeps in close contact with NOAA to make altitude adjustments to satellites. The measures enabled the company to avoid problems during both G5 events, he said.
“The most significant impact for most satellites in low Earth orbit is a drastic increase in atmospheric drag during these events. It’s short-lived but could be a major problem for satellites that are not equipped to maneuver to regain their previous orbits,” he said. “For Iridium, maneuvering to counteract atmospheric drag is something we do very often.
“We had been seeing more solar activity in 2024 leading up to the G5 event in May, so it didn’t come as a surprise,” he said. “These things are not easy to predict, but NOAA does provide plenty of usable data to the public and did warn of a potential major solar event a day or two prior.”
Still, ample lead time might not be enough to stave off a bigger, potentially devastating threat, like a repeat of 1859’s Carrington Event, a space weather phenomenon that forecasters say was three to five times stronger than the 2003 and 2024 storms. “If we experienced that kind of level today, we’re pretty certain that this could be the first where the general public might notice some kind of bulk transmission failure because of overheated transformers or failures in the high-voltage transmission line systems that we have in the Canadian provinces and down here through the mainland 48 in the United States,” Dahl said.
That’s just the start. GPS signals would become garbled, and receivers would fail, affecting agriculture, banking, transportation — essentially any technology dependent on the global navigation satellite system. High-frequency communications would be degraded or stop working altogether, affecting planes and the military, and the internet would shut down. The breakdown could last possibly for weeks or months.
Named for British astronomer Richard Carrington — who observed an intense white flare on the sun’s surface followed by a series of CMEs shortly before noon on September 1, 1859 — the geomagnetic storm is regarded as the largest on record. It was reported that the event produced polarlike auroras visible as far from the poles as Colombia. Miners in the Rockies made breakfast after 1 a.m., mistaking the northern lights for a misty early morning. New Yorkers read their evening newspapers by the sudden bright night sky. And telegraph operators noted widespread outages as their machines sparked and flared up, igniting telegraph paper.
Dahl said he believes another Carrington-type storm will likely occur. In fact, he said, the sun already has produced similarly powerful weather events, but none angled sufficiently toward Earth to produce a geomagnetic storm like the Carrington one.
David Wallace, assistant clinical professor of electrical engineering at Mississippi State University, agrees, writing in 2024 that it’s “a matter of time” before another Carrington Event happens. When it does, he said, it will allow for only a narrow lead time to notify the nation’s power grid operators and military. “Even with space weather warnings from NOAA’s Space Weather Prediction Center, the world would have only a few minutes to a few hours’ notice.”
“Today, a geomagnetic storm of the same intensity as the Carrington Event would affect far more than telegraph wires and could be catastrophic,” Wallace wrote in an article published in 2024 in The Conversation and Astronomy magazine. “In addition to electrical failures, communications would be disrupted on a worldwide scale. Internet service providers could go down, which in turn would take out the ability of different systems to communicate with each other.
“High-frequency communication systems such as ground-to-air, shortwave and ship-to-shore radio would be disrupted,” he said. “Satellites in orbit around Earth could be damaged by induced currents from the geomagnetic storm burning out their circuit boards. This would lead to disruptions in satellite-based telephone, internet, radio and television.”
The disruption to GPS for navigation and tracking would extend beyond civil usage, potentially affecting the military’s over-the-horizon radar at North American Aerospace Defense Command and submarine detection systems, “which would hamper national defense,” Wallace said.
Estimates to restore the systems, including the grid, vary widely, with some experts asserting it might take weeks or months for power to fully return. However, the aftereffects could linger longer. Physics Professor Mike Hapgood of Lancaster University, United Kingdom, wrote in an April 2012 study in the journal Nature that the technological and economic ripple effects of a Carrington Event could continue for years.
Hapgood based his findings on assessments of space weather events worldwide, including in the U.K. and North America. He also analyzed a more recent event — a geomagnetic storm in 1989 that was one-third the intensity of the Carrington one. That event resulted in the collapse of the Hydro-Quebec electrical grid in Quebec, Canada, which triggered a nine-hour blackout that left 5 million people in freezing temperatures and caused $2 billion in damages to businesses. “It also permanently wiped out a $12 million transformer in the United States and caused two large U.K. transformers to be sent back to the factory for repairs.”
“A study by the UK National Grid suggests that a repeat of the 1859 event would leave some regions without power for several months,” Hapgood wrote. “In the United States, some assessments predict widescale disruption with ripple effects lasting for years and an economic impact of several trillion dollars.”
Spurred by these events and the threat of other storms, government officials have stepped up measures to monitor the sun and develop strategies to prepare for extreme space weather. In 2015, the U.S. launched NOAA’s Deep Space Climate Observatory (DSCOVR) to join the Solar and Heliospheric Observatory (SOHO) satellite — maintained by NASA and the European Space Agency — that was deployed 20 years earlier.
DSCOVR can measure sudden increases in solar wind density, total interplanetary magnetic field strength and solar wind speed, which, in turn, may indicate the arrival of a “CME-associated interplanetary shock ahead of the magnetic cloud,” according to SWPC. “This can often provide 15 to 60 minutes advanced warning of shock arrival at Earth – and any possible sudden impulse or sudden storm commencement, as registered by Earth-based magnetometers.” Both the DSCOVR and SOHO spacecraft are positioned about 1.5 million kilometers from Earth.
In 2016, the White House directed federal agencies to develop plans to mitigate the impacts of space weather events. These measures have continued through subsequent administrations.
In 2020, Congress approved the Promoting Research and Observations of Space Weather to Improve the Forecasting of Tomorrow (PROSWIFT) Act. The legislation called for a coordinated federal response to severe space weather. NOAA was tasked with improving forecasting and evaluating commercial satellite data. For the past 10 years, SWPC has worked with emergency management teams from counties, states and the federal government to help them understand the threat that severe solar storms can pose. Power grid operators, for example, regularly receive alerts and warnings when a G3, G4 or G5 storm is anticipated.
“Over the last 10 to 15 years, a lot of work has been done, bills have been passed in Congress and executive orders have been given, and FEMA now recognizes this as a significant potential hazard,” Dahl said. “We’re ready, and a big event may prove that we’re ready. But a Carrington G5, we don’t know if we’re quite ready for that yet, so a lot of this information is going to be studied because we want to be ready. The ultimate goal here is to be able to weather a major Carrington-like event here on Earth, with all of our technologies, but in particular the power grid because we can’t let people go without power for weeks to months.”
Mississippi State’s Wallace suggested pushing the envelope further to safeguard the grid, saying, “It is only a matter of time before Earth is hit by another geomagnetic storm.
“I believe it is critical to continue researching ways to protect electrical systems against the effects of geomagnetic storms, for example by installing devices that can shield vulnerable equipment like transformers and by developing strategies for adjusting grid loads when solar storms are about to hit,” he said. “In short, it’s important to work now to minimize the disruptions from the next Carrington Event.”