Solar storms have influenced our history – an environmental historian explains how they could also threaten our future

In May 2024, part of the Sun exploded.

The Sun is a huge ball of superheated gas called plasma. Since plasma is conductive, magnetic fields escape from the solar surface. Because different parts of the surface rotate at different speeds, the fields become entangled. Eventually, like rubber bands that are too tight, they can snap – and that’s what they did last year.

These titanic plasma explosions, also known as solar flares, each released the energy of a million hydrogen bombs. Parts of the solar magnetic field were also released in the form of magnetic bubbles loaded with billions of tons of plasma.

These bubbles, called coronal mass ejections, or CMEs, crashed into space at about 6,000 times the speed of a commercial airliner. After a few days, they crashed one after the other in the magnetic field that envelops the Earth. Plasma from each CME moved toward us, creating bright auroras and powerful electrical currents that spread through the Earth’s crust.

You may not have noticed it. Just as the opposite poles of refrigerator magnets must line up for them to fit together, the poles of Earth’s magnetic field and the incoming CMEs must line up perfectly for plasma from CMEs to reach Earth. This time they didn’t, so most of the plasma flew off into deep space.

Humans haven’t always been so lucky. I am an environmental historian and author of the new book “Ripples on the Cosmic Ocean: An Environmental History of Our Place in the Solar System.”

In writing this book, I learned that a series of technological breakthroughs – from telegraphs to satellites – have made modern societies increasingly vulnerable to the influence of solar storms, that is, flares and CMEs.

Since the 19th century, these storms have repeatedly disrupted life on Earth. Today, there are indications that they threaten the very survival of civilization as we know it.

The telegraph: a first warning

On the morning of September 1, 1859, two young astronomers, Richard Carrington and Richard Hodgson, became the first humans to observe a solar flare. To their amazement, it was so powerful that, for two minutes, it far eclipsed the rest of the Sun.

About 18 hours later, brilliant blood-red auroras shimmered in the night sky all the way to the equator, while newly constructed telegraph lines were short-circuited across Europe and the Americas.

The Carrington Event, as it would later be called, revealed that the Sun’s environment could change violently. It also suggested that emerging technologies, such as the electric telegraph, were beginning to link modern life to the extraordinary violence of the Sun’s most explosive changes.

For more than a century, these connections represented little more than inconveniences, such as occasional telegraph outages, in part because no solar storm rivaled the power of the Carrington event. But another reason was that the world’s economies and militaries were only gradually beginning to rely more and more on technologies that proved deeply vulnerable to changes wrought by the Sun.

A brushstroke with Armageddon

Then came May 1967.

Soviet and American warships collided in the Sea of ​​Japan, American troops marched into North Vietnam, and the Middle East stood on the brink of the Six-Day War.

It was only a frightening combination of new technologies that kept the United States and the Soviet Union from all-out war; nuclear missiles could now destroy a country in minutes, but radar could detect their approach in time to strike back. A direct attack on either superpower would be suicidal.

Suddenly, on May 23, a series of violent solar flares swept the Earth with powerful radio waves, destroying American radar stations in Alaska, Greenland and England.

Forecasters had warned officers at the North American Air Defense Command, or NORAD, to expect a solar storm. But the scale of the radar failure convinced Air Force officers that the Soviets were responsible. This was exactly the kind of thing the USSR would do before launching a nuclear attack.

American bombers, loaded with nuclear weapons, are preparing to respond. The solar storm had jammed their wireless communications so badly that it might have been impossible to call them back once they took off. Just in time, forecasters used their observations of the Sun to convince NORAD officers that a solar storm had jammed their radar. We may be alive today because they succeeded.

Power outages, transformers and meltdowns

In contact with nuclear war, solar storms had become a source of existential risk, that is to say a potential threat to the existence of humanity. Yet the magnitude of this risk did not become apparent until March 1989, when 11 powerful flares preceded the arrival of consecutive coronal mass ejections.

For more than two decades, North American utility companies built a vast transmission system that relayed electricity from power plants to consumers. In 1989, this system was found to be vulnerable to the currents that coronal mass ejections channeled through the Earth’s crust.

In Quebec, the crystalline bedrock beneath the city conducts electricity with difficulty. Rather than flowing through rock, the currents surged through the world’s largest hydroelectric transmission system. It collapsed, leaving millions without power in freezing weather.

The repairs revealed something worrying: The currents had damaged several transformers, which are huge custom devices that transfer electricity between circuits.

Replacing transformers can take several months. If the 1989 storm had been as powerful as the Carrington event, hundreds of transformers could have been destroyed. It would have taken years to restore electricity across North America.

Solar storms: an existential risk

But was the Carrington event really the worst storm the Sun could unleash?

Scientists thought this was the case until, in 2012, a team of Japanese scientists discovered evidence of an extraordinary burst of high-energy particles in tree rings dating back to the eighth century CE. The main explanation for this is: huge solar storms eclipsing the Carrington event. Scientists now estimate that these “Miyake events” occur every few centuries.

Astronomers have also discovered that every century, stars similar to the Sun can explode in super flares up to 10,000 times more powerful than the most powerful solar flares ever observed. Because the Sun is older and rotates more slowly than many of these stars, its super flares may be much rarer, occurring perhaps once every 3,000 years.

Nevertheless, the implications are alarming. In the past, powerful solar storms only affected humanity by creating brilliant auroras. Today, civilization depends on electrical grids that allow goods, information and people to move across our world, from sewer systems to satellite constellations.

What would happen if these systems suddenly collapsed on a continental scale for months or even years? Would millions of people die? And could a single solar storm cause this?

Researchers are working to answer these questions. For now, one thing is certain: to protect these networks, scientists must monitor the Sun in real time. This way, operators can reduce or reroute electricity flowing through networks as a CME approaches. A little preparation can prevent a meltdown.

Fortunately, satellites and telescopes on Earth today keep the Sun under constant observation. Yet in the United States, recent efforts to cut NASA’s science budget have cast doubt on plans to replace aging Sun-monitoring satellites. Even the Daniel K. Inouye Solar Telescope, the world’s first solar observatory, could soon close its doors.

These potential reductions remind us of our tendency to ignore existential risks – until it is too late.

This article is republished from The Conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you make sense of our complex world. It was written by: Dagomar Degroot, Georgetown University

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Dagomar Degroot has received funding from NASA.